Recognise more exceptions (#129)

CLAUDE.md

@@ -67,13 +67,12 @@ dotnet run --project WoofWare.PawPrint.App/WoofWare.PawPrint.App.fsproj -- CShar
 - `Corelib.fs`: Core library type definitions (String, Array, etc.)
 
 **WoofWare.PawPrint.Test**
-- Uses Expecto as the test framework
+- Uses NUnit as the test framework
 - Test cases are defined in `TestPureCases.fs` and `TestImpureCases.fs`
-- C# source files in `sources{Pure,Impure}/` are compiled and executed by the runtime as test cases
+- C# source files in `sources{Pure,Impure}/` are compiled and executed by the runtime as test cases; files in `sourcesPure` are automatically turned into test cases with no further action (see TestPureCases.fs for the mechanism)
 - `TestHarness.fs` provides infrastructure for running test assemblies through the interpreter
 - Run all tests with `dotnet run --project WoofWare.PawPrint.Test/WoofWare.PawPrint.Test.fsproj -- --no-spinner` (note the additional `--`)
 - Run a specific test with `dotnet run --project WoofWare.PawPrint.Test/WoofWare.PawPrint.Test.fsproj -- --filter-test-case StringWithinTestName --no-spinner`
-- Pending test definitions must be moved into the non-pending test case list before they can be run.
 
 **WoofWare.PawPrint.App**
 - Entry point application for running the interpreter

WoofWare.PawPrint.Domain/Assembly.fs

@@ -565,6 +565,7 @@ module DumpedAssembly =
         (bct : BaseClassTypes<DumpedAssembly>)
         (assemblies : ImmutableDictionary<string, DumpedAssembly>)
         (ti : TypeInfo<TypeDefn, TypeDefn>)
+        : TypeDefn
         =
         ti
         |> TypeInfo.toTypeDefn

WoofWare.PawPrint.Domain/ConcreteType.fs

@@ -33,6 +33,20 @@ type ConcreteType<'typeGeneric> =
             _Generics : ImmutableArray<'typeGeneric>
         }
 
+    override this.ToString () : string =
+        let basic = $"%s{this.Assembly.Name}.%s{this.Namespace}.%s{this.Name}"
+
+        let generics =
+            if this.Generics.IsEmpty then
+                ""
+            else
+                this.Generics
+                |> Seq.map string
+                |> String.concat ", "
+                |> fun x -> "<" + x + ">"
+
+        basic + generics
+
     member this.Assembly : AssemblyName = this._AssemblyName
     member this.Definition : ComparableTypeDefinitionHandle = this._Definition
     member this.Generics : ImmutableArray<'typeGeneric> = this._Generics

WoofWare.PawPrint.Domain/Constants.fs

@@ -8,3 +8,9 @@ module Constants =
 
     [<Literal>]
     let SIZEOF_OBJ = 8
+
+    [<Literal>]
+    let DEFAULT_STRUCT_ALIGNMENT = 8
+
+    [<Literal>]
+    let NATIVE_INT_SIZE = 8

WoofWare.PawPrint.Domain/FieldInfo.fs

@@ -57,11 +57,10 @@ module FieldInfo =
         let fieldSig = def.DecodeSignature (TypeDefn.typeProvider assembly, ())
         let declaringType = def.GetDeclaringType ()
 
-        let typeGenerics =
-            mr.GetTypeDefinition(declaringType).GetGenericParameters ()
-            |> GenericParameter.readAll mr
-
         let decType = mr.GetTypeDefinition declaringType
+
+        let typeGenerics = decType.GetGenericParameters () |> GenericParameter.readAll mr
+
         let declaringTypeNamespace = mr.GetString decType.Namespace
         let declaringTypeName = mr.GetString decType.Name
 

WoofWare.PawPrint.Domain/TypeConcretisation.fs

@@ -183,6 +183,24 @@ module ConcreteActivePatterns =
             | _ -> None
         | _ -> None
 
+    let (|ConcreteGenericArray|_|)
+        (concreteTypes : AllConcreteTypes)
+        (eltType : ConcreteTypeHandle)
+        (handle : ConcreteTypeHandle)
+        =
+        match handle with
+        | ConcreteTypeHandle.Concrete id ->
+            match concreteTypes.Mapping |> Map.tryFind id with
+            | Some ct when
+                ct.Assembly.Name = "System.Private.CoreLib"
+                && ct.Namespace = "System"
+                && ct.Name = "Array"
+                && Seq.tryExactlyOne ct.Generics = Some eltType
+                ->
+                Some ()
+            | _ -> None
+        | _ -> None
+
     let (|ConcreteObj|_|) (concreteTypes : AllConcreteTypes) (handle : ConcreteTypeHandle) : unit option =
         match handle with
         | ConcreteTypeHandle.Concrete id ->
@@ -302,6 +320,40 @@ module ConcreteActivePatterns =
             | None -> None
         | _ -> None
 
+    let (|ConcreteUInt32|_|) (concreteTypes : AllConcreteTypes) (handle : ConcreteTypeHandle) : unit option =
+        match handle with
+        | ConcreteTypeHandle.Concrete id ->
+            match concreteTypes.Mapping |> Map.tryFind id with
+            | Some ct ->
+                if
+                    ct.Assembly.Name = "System.Private.CoreLib"
+                    && ct.Namespace = "System"
+                    && ct.Name = "UInt32"
+                    && ct.Generics.IsEmpty
+                then
+                    Some ()
+                else
+                    None
+            | None -> None
+        | _ -> None
+
+    let (|ConcreteUInt64|_|) (concreteTypes : AllConcreteTypes) (handle : ConcreteTypeHandle) : unit option =
+        match handle with
+        | ConcreteTypeHandle.Concrete id ->
+            match concreteTypes.Mapping |> Map.tryFind id with
+            | Some ct ->
+                if
+                    ct.Assembly.Name = "System.Private.CoreLib"
+                    && ct.Namespace = "System"
+                    && ct.Name = "UInt64"
+                    && ct.Generics.IsEmpty
+                then
+                    Some ()
+                else
+                    None
+            | None -> None
+        | _ -> None
+
     let (|ConcreteSingle|_|) (concreteTypes : AllConcreteTypes) (handle : ConcreteTypeHandle) : unit option =
         match handle with
         | ConcreteTypeHandle.Concrete id ->
@@ -331,6 +383,13 @@ module ConcreteActivePatterns =
         | ConcreteTypeHandle.Pointer inner -> Some inner
         | _ -> None
 
+type IAssemblyLoad =
+    abstract LoadAssembly :
+        loadedAssemblies : ImmutableDictionary<string, DumpedAssembly> ->
+        referencedIn : AssemblyName ->
+        handle : AssemblyReferenceHandle ->
+            ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly
+
 [<RequireQualifiedAccess>]
 module TypeConcretization =
 
@@ -406,8 +465,7 @@ module TypeConcretization =
 
     // Helper function for assembly loading with retry pattern
     let private loadAssemblyAndResolveTypeRef
-        (loadAssembly :
-            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
+        (loadAssembly : IAssemblyLoad)
         (ctx : ConcretizationContext<'corelib>)
         (currentAssembly : AssemblyName)
         (typeRef : TypeRef)
@@ -428,7 +486,8 @@ module TypeConcretization =
             // Need to load the assembly
             match typeRef.ResolutionScope with
             | TypeRefResolutionScope.Assembly assyRef ->
-                let newAssemblies, _ = loadAssembly currentAssembly assyRef
+                let newAssemblies, _ =
+                    loadAssembly.LoadAssembly ctx.LoadedAssemblies currentAssembly assyRef
 
                 let newCtx =
                     { ctx with
@@ -584,8 +643,7 @@ module TypeConcretization =
                 ImmutableArray.Empty // No generic parameters
 
     let private concretizeTypeReference
-        (loadAssembly :
-            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
+        (loadAssembly : IAssemblyLoad)
         (ctx : ConcretizationContext<'corelib>)
         (currentAssembly : AssemblyName)
         (typeRef : TypeRef)
@@ -609,8 +667,7 @@ module TypeConcretization =
     /// Concretize a type in a specific generic context
     let rec concretizeType
         (ctx : ConcretizationContext<DumpedAssembly>)
-        (loadAssembly :
-            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
+        (loadAssembly : IAssemblyLoad)
         (assembly : AssemblyName)
         (typeGenerics : ImmutableArray<ConcreteTypeHandle>)
         (methodGenerics : ImmutableArray<ConcreteTypeHandle>)
@@ -706,8 +763,7 @@ module TypeConcretization =
 
     and private concretizeGenericInstantiation
         (ctx : ConcretizationContext<DumpedAssembly>)
-        (loadAssembly :
-            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
+        (loadAssembly : IAssemblyLoad)
         (assembly : AssemblyName)
         (typeGenerics : ImmutableArray<ConcreteTypeHandle>)
         (methodGenerics : ImmutableArray<ConcreteTypeHandle>)
@@ -786,7 +842,8 @@ module TypeConcretization =
 
                     | false, _ ->
                         // Need to load the assembly
-                        let newAssemblies, loadedAssy = loadAssembly assembly assyRef
+                        let newAssemblies, loadedAssy =
+                            loadAssembly.LoadAssembly ctx.LoadedAssemblies assembly assyRef
 
                         let ctxWithNewAssy =
                             { ctxAfterArgs with
@@ -865,8 +922,7 @@ module Concretization =
     /// Helper to concretize an array of types
     let private concretizeTypeArray
         (ctx : TypeConcretization.ConcretizationContext<DumpedAssembly>)
-        (loadAssembly :
-            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
+        (loadAssembly : IAssemblyLoad)
         (assembly : AssemblyName)
         (typeArgs : ImmutableArray<ConcreteTypeHandle>)
         (methodArgs : ImmutableArray<ConcreteTypeHandle>)
@@ -889,8 +945,7 @@ module Concretization =
     /// Helper to concretize a method signature
     let private concretizeMethodSignature
         (ctx : TypeConcretization.ConcretizationContext<DumpedAssembly>)
-        (loadAssembly :
-            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
+        (loadAssembly : IAssemblyLoad)
         (assembly : AssemblyName)
         (typeArgs : ImmutableArray<ConcreteTypeHandle>)
         (methodArgs : ImmutableArray<ConcreteTypeHandle>)
@@ -926,8 +981,7 @@ module Concretization =
 
     /// Helper to ensure base type assembly is loaded
     let rec private ensureBaseTypeAssembliesLoaded
-        (loadAssembly :
-            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
+        (loadAssembly : IAssemblyLoad)
         (assemblies : ImmutableDictionary<string, DumpedAssembly>)
         (assyName : AssemblyName)
         (baseTypeInfo : BaseTypeInfo option)
@@ -947,7 +1001,7 @@ module Concretization =
                 | true, _ -> assemblies
                 | false, _ ->
                     // Need to load the assembly - pass the assembly that contains the reference
-                    let newAssemblies, _ = loadAssembly assy.Name assyRef
+                    let newAssemblies, _ = loadAssembly.LoadAssembly assemblies assy.Name assyRef
                     newAssemblies
             | _ -> assemblies
         | Some (BaseTypeInfo.TypeDef _)
@@ -957,8 +1011,7 @@ module Concretization =
     /// Concretize a method's signature and body
     let concretizeMethod
         (ctx : AllConcreteTypes)
-        (loadAssembly :
-            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
+        (loadAssembly : IAssemblyLoad)
         (assemblies : ImmutableDictionary<string, DumpedAssembly>)
         (baseTypes : BaseClassTypes<DumpedAssembly>)
         (method : WoofWare.PawPrint.MethodInfo<'ty, GenericParamFromMetadata, TypeDefn>)

WoofWare.PawPrint.Domain/TypeDefn.fs

@@ -6,6 +6,8 @@ open System.Reflection.Metadata
 open System.Reflection.Metadata.Ecma335
 open Microsoft.FSharp.Core
 
+[<RequireQualifiedAccess>]
+[<NoComparison>]
 type ResolvedBaseType =
     | Enum
     | ValueType
@@ -167,8 +169,8 @@ module PrimitiveType =
         | PrimitiveType.Double -> 8
         | PrimitiveType.String -> 8
         | PrimitiveType.TypedReference -> failwith "todo"
-        | PrimitiveType.IntPtr -> 8
-        | PrimitiveType.UIntPtr -> 8
+        | PrimitiveType.IntPtr -> NATIVE_INT_SIZE
+        | PrimitiveType.UIntPtr -> NATIVE_INT_SIZE
         | PrimitiveType.Object -> 8
 
 type TypeDefn =

WoofWare.PawPrint.Domain/TypeInfo.fs

@@ -29,6 +29,10 @@ type InterfaceImplementation =
         RelativeToAssembly : AssemblyName
     }
 
+type Layout =
+    | Default
+    | Custom of size : int * packingSize : int
+
 /// <summary>
 /// Represents detailed information about a type definition in a .NET assembly.
 /// This is a strongly-typed representation of TypeDefinition from System.Reflection.Metadata.
@@ -93,6 +97,8 @@ type TypeInfo<'generic, 'fieldGeneric> =
         Events : EventDefn ImmutableArray
 
         ImplementedInterfaces : InterfaceImplementation ImmutableArray
+
+        Layout : Layout
     }
 
     member this.IsInterface = this.TypeAttributes.HasFlag TypeAttributes.Interface
@@ -184,6 +190,18 @@ type BaseClassTypes<'corelib> =
         TypedReference : TypeInfo<GenericParamFromMetadata, TypeDefn>
         IntPtr : TypeInfo<GenericParamFromMetadata, TypeDefn>
         UIntPtr : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        Exception : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        ArithmeticException : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        DivideByZeroException : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        OverflowException : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        StackOverflowException : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        TypeLoadException : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        IndexOutOfRangeException : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        InvalidCastException : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        MissingFieldException : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        MissingMethodException : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        NullReferenceException : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        OutOfMemoryException : TypeInfo<GenericParamFromMetadata, TypeDefn>
     }
 
 [<RequireQualifiedAccess>]
@@ -213,6 +231,7 @@ module TypeInfo =
             Generics = gen
             Events = t.Events
             ImplementedInterfaces = t.ImplementedInterfaces
+            Layout = t.Layout
         }
 
     let mapGeneric<'a, 'b, 'field> (f : 'a -> 'b) (t : TypeInfo<'a, 'field>) : TypeInfo<'b, 'field> =
@@ -308,6 +327,14 @@ module TypeInfo =
 
             result.ToImmutable ()
 
+        let layout =
+            let l = typeDef.GetLayout ()
+
+            if l.IsDefault then
+                Layout.Default
+            else
+                Layout.Custom (size = l.Size, packingSize = l.PackingSize)
+
         {
             Namespace = ns
             Name = name
@@ -323,6 +350,7 @@ module TypeInfo =
             Events = events
             ImplementedInterfaces = interfaces
             DeclaringType = declaringType
+            Layout = layout
         }
 
     let isBaseType<'corelib>

WoofWare.PawPrint.Domain/WoofWare.PawPrint.Domain.fsproj

@@ -7,6 +7,7 @@
 
     <ItemGroup>
         <Compile Include="StringToken.fs" />
+        <Compile Include="Constants.fs" />
         <Compile Include="ImmutableArray.fs" />
         <Compile Include="Tokens.fs" />
         <Compile Include="TypeRef.fs" />

WoofWare.PawPrint.Test/LoggerFactory.fs

@@ -23,7 +23,7 @@ module LoggerFactory =
     let makeTest () : (unit -> LogLine list) * ILoggerFactory =
         // Shared sink for all loggers created by the factory.
         let sink = ResizeArray ()
-        let isEnabled (logLevel : LogLevel) : bool = logLevel >= LogLevel.Debug
+        let isEnabled (logLevel : LogLevel) : bool = logLevel >= LogLevel.Information
 
         let createLogger (category : string) : ILogger =
             { new ILogger with

WoofWare.PawPrint.Test/TestImpureCases.fs

@@ -1,5 +1,6 @@
 namespace WoofWare.Pawprint.Test
 
+open System
 open System.Collections.Immutable
 open System.IO
 open FsUnitTyped

WoofWare.PawPrint.Test/TestPureCases.fs

@@ -1,5 +1,6 @@
 namespace WoofWare.Pawprint.Test
 
+open System
 open System.Collections.Immutable
 open System.IO
 open FsUnitTyped
@@ -16,161 +17,65 @@ module TestPureCases =
 
     let unimplemented =
         [
-            {
-                FileName = "CrossAssemblyTypes.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "InitializeArray.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "GenericEdgeCases.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "Threads.cs"
-                ExpectedReturnCode = 3
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "ComplexTryCatch.cs"
-                ExpectedReturnCode = 14
-                NativeImpls = NativeImpls.PassThru ()
-            }
-            {
-                FileName = "ResizeArray.cs"
-                ExpectedReturnCode = 114
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "Sizeof.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "LdtokenField.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "AdvancedStructLayout.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "OverlappingStructs.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "UnsafeAs.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
+            "CrossAssemblyTypes.cs"
+            "OverlappingStructs.cs"
+            "AdvancedStructLayout.cs"
+            "InitializeArray.cs"
+            "Threads.cs"
+            "ComplexTryCatch.cs"
+            "ResizeArray.cs"
+            "LdtokenField.cs"
+            "GenericEdgeCases.cs"
+            "UnsafeAs.cs"
         ]
+        |> Set.ofList
+
+    let requiresMocks =
+        let empty = MockEnv.make ()
 
-    let cases : EndToEndTestCase list =
         [
-            {
-                FileName = "NoOp.cs"
-                ExpectedReturnCode = 1
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "TestShl.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "TestShr.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "StaticVariables.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "Ldind.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "CustomDelegate.cs"
-                ExpectedReturnCode = 8
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "ArgumentOrdering.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "BasicLock.cs"
-                ExpectedReturnCode = 1
-                NativeImpls =
-                    let mock = MockEnv.make ()
-
-                    { mock with
-                        System_Threading_Monitor = System_Threading_Monitor.passThru
-                    }
-            }
-            {
-                FileName = "TriangleNumber.cs"
-                ExpectedReturnCode = 10
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "ExceptionWithNoOpFinally.cs"
-                ExpectedReturnCode = 3
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "ExceptionWithNoOpCatch.cs"
-                ExpectedReturnCode = 10
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "Floats.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "TryCatchWithThrowInBody.cs"
-                ExpectedReturnCode = 4
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "Ldelema.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "TypeConcretization.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "TestOr.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "InterfaceDispatch.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
-            {
-                FileName = "Initobj.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-            }
+            "BasicLock.cs",
+            (1,
+             { empty with
+                 System_Threading_Monitor = System_Threading_Monitor.passThru
+             })
         ]
+        |> Map.ofList
+
+    let customExitCodes =
+        [
+            "NoOp.cs", 1
+            "CustomDelegate.cs", 8
+            "ExceptionWithNoOpFinally.cs", 3
+            "ExceptionWithNoOpCatch.cs", 10
+            "TryCatchWithThrowInBody.cs", 4
+            "ResizeArray.cs", 114
+            "Threads.cs", 3
+            "TriangleNumber.cs", 10
+        ]
+        |> Map.ofList
+
+    let allPure =
+        assy.GetManifestResourceNames ()
+        |> Seq.choose (fun res ->
+            let s = "WoofWare.PawPrint.Test.sourcesPure."
+
+            if res.StartsWith (s, StringComparison.OrdinalIgnoreCase) then
+                res.Substring s.Length |> Some
+            else
+                None
+        )
+        |> Set.ofSeq
+
+    let simpleCases : string list =
+        allPure
+        |> Seq.filter (fun s ->
+            (customExitCodes.ContainsKey s
+             || requiresMocks.ContainsKey s
+             || unimplemented.Contains s)
+            |> not
+        )
+        |> Seq.toList
 
     let runTest (case : EndToEndTestCase) : unit =
         let source = Assembly.getEmbeddedResourceAsString case.FileName assy
@@ -205,9 +110,43 @@ module TestPureCases =
 
             reraise ()
 
+    [<TestCaseSource(nameof simpleCases)>]
+    let ``Standard tests`` (fileName : string) =
+        {
+            FileName = fileName
+            ExpectedReturnCode = 0
+            NativeImpls = MockEnv.make ()
+        }
+        |> runTest
+
+    [<TestCaseSource(nameof customExitCodes)>]
+    let ``Custom exit code tests`` (KeyValue (fileName : string, exitCode : int)) =
+        if unimplemented.Contains fileName then
+            Assert.Inconclusive ()
+
+        {
+            FileName = fileName
+            ExpectedReturnCode = exitCode
+            NativeImpls = MockEnv.make ()
+        }
+        |> runTest
+
+    [<TestCaseSource(nameof requiresMocks)>]
+    let ``Tests which require mocks`` (KeyValue (fileName : string, (exitCode : int, mock : NativeImpls))) =
+        {
+            FileName = fileName
+            ExpectedReturnCode = exitCode
+            NativeImpls = mock
+        }
+        |> runTest
+
+
     [<TestCaseSource(nameof unimplemented)>]
     [<Explicit>]
-    let ``Can evaluate C# files, unimplemented`` (case : EndToEndTestCase) = runTest case
-
-    [<TestCaseSource(nameof cases)>]
-    let ``Can evaluate C# files`` (case : EndToEndTestCase) = runTest case
+    let ``Can evaluate C# files, unimplemented`` (fileName : string) =
+        {
+            FileName = fileName
+            ExpectedReturnCode = 0
+            NativeImpls = MockEnv.make ()
+        }
+        |> runTest

WoofWare.PawPrint.Test/sourcesPure/ComparisonOperations.cs

@@ -0,0 +1,255 @@
+public class TestComparisonOperations
+{
+    // Test Ceq: Compare equal
+    public static int TestCompareEqual()
+    {
+        // Integer equality
+        if ((5 == 5) != true) return 1;
+        if ((5 == 6) != false) return 2;
+        if ((int.MaxValue == int.MaxValue) != true) return 3;
+        if ((int.MinValue == int.MaxValue) != false) return 4;
+        
+        // Negative numbers
+        if ((-1 == -1) != true) return 5;
+        if ((-5 == 5) != false) return 6;
+        
+        // Long equality
+        if ((100L == 100L) != true) return 7;
+        if ((100L == 101L) != false) return 8;
+        
+        // Mixed sizes (after promotion)
+        int i = 42;
+        long l = 42L;
+        if ((l == (long)i) != true) return 9;
+        
+        // Zero comparisons
+        if ((0 == 0) != true) return 10;
+        if ((0 == 1) != false) return 11;
+        
+        return 0;
+    }
+    
+    // Test Cgt: Compare greater than (signed)
+    public static int TestCompareGreaterThan()
+    {
+        // Positive integers
+        if ((10 > 5) != true) return 20;
+        if ((5 > 10) != false) return 21;
+        if ((5 > 5) != false) return 22;
+        
+        // Negative integers
+        if ((-5 > -10) != true) return 23;
+        if ((-10 > -5) != false) return 24;
+        if ((5 > -5) != true) return 25;
+        if ((-5 > 5) != false) return 26;
+        
+        // Boundary values
+        if ((int.MaxValue > int.MinValue) != true) return 27;
+        if ((int.MinValue > int.MaxValue) != false) return 28;
+        if ((int.MaxValue > (int.MaxValue - 1)) != true) return 29;
+        
+        // Zero comparisons
+        if ((1 > 0) != true) return 30;
+        if ((0 > 1) != false) return 31;
+        if ((-1 > 0) != false) return 32;
+        if ((0 > -1) != true) return 33;
+        
+        return 0;
+    }
+    
+    // Test Cgt_un: Compare greater than (unsigned)
+    public static int TestCompareGreaterThanUnsigned()
+    {
+        uint a = 10;
+        uint b = 5;
+        
+        // Basic unsigned comparison
+        if ((a > b) != true) return 40;
+        if ((b > a) != false) return 41;
+        if ((a > a) != false) return 42;
+        
+        // High bit set (would be negative if signed)
+        uint high = 0x80000000;
+        uint low = 0x7FFFFFFF;
+        if ((high > low) != true) return 43;  // Unsigned: high > low
+        
+        // Maximum values
+        uint max = uint.MaxValue;
+        uint min = uint.MinValue;
+        if ((max > min) != true) return 44;
+        if ((min > max) != false) return 45;
+        
+        // Interpret negative as unsigned
+        uint negAsUint = unchecked((uint)-1);
+        uint one = 1;
+        if ((negAsUint > one) != true) return 46;  // 0xFFFFFFFF > 1
+        
+        return 0;
+    }
+    
+    // Test Clt: Compare less than (signed)
+    public static int TestCompareLessThan()
+    {
+        // Positive integers
+        if ((5 < 10) != true) return 50;
+        if ((10 < 5) != false) return 51;
+        if ((5 < 5) != false) return 52;
+        
+        // Negative integers
+        if ((-10 < -5) != true) return 53;
+        if ((-5 < -10) != false) return 54;
+        if ((-5 < 5) != true) return 55;
+        if ((5 < -5) != false) return 56;
+        
+        // Boundary values
+        if ((int.MinValue < int.MaxValue) != true) return 57;
+        if ((int.MaxValue < int.MinValue) != false) return 58;
+        
+        // Zero comparisons
+        if ((0 < 1) != true) return 59;
+        if ((1 < 0) != false) return 60;
+        if ((0 < -1) != false) return 61;
+        if ((-1 < 0) != true) return 62;
+        
+        return 0;
+    }
+    
+    // Test Clt_un: Compare less than (unsigned)
+    public static int TestCompareLessThanUnsigned()
+    {
+        uint a = 5;
+        uint b = 10;
+        
+        // Basic unsigned comparison
+        if ((a < b) != true) return 70;
+        if ((b < a) != false) return 71;
+        if ((a < a) != false) return 72;
+        
+        // High bit set
+        uint high = 0x80000000;
+        uint low = 0x7FFFFFFF;
+        if ((low < high) != true) return 73;  // Unsigned: low < high
+        
+        // Boundary values
+        uint max = uint.MaxValue;
+        uint min = uint.MinValue;
+        if ((min < max) != true) return 74;
+        if ((max < min) != false) return 75;
+        
+        // Negative as unsigned
+        uint one = 1;
+        uint negAsUint = unchecked((uint)-1);
+        if ((one < negAsUint) != true) return 76;  // 1 < 0xFFFFFFFF
+        
+        return 0;
+    }
+    
+    // Test comparison combinations
+    public static int TestComparisonCombinations()
+    {
+        int x = 10;
+        int y = 20;
+        int z = 10;
+        
+        // Equality chains
+        if ((x == z) != true) return 80;
+        if ((x == y) != false) return 81;
+        
+        // Inequality combinations
+        if ((x < y && y > x) != true) return 82;
+        if ((x < y && x == y) != false) return 83;
+        
+        // Transitive comparisons
+        if (x < y && y < 30)
+        {
+            if ((x < 30) != true) return 84;
+        }
+        else
+        {
+            return 85;
+        }
+        
+        return 0;
+    }
+    
+    // Test comparisons with different types
+    public static int TestMixedTypeComparisons()
+    {
+        // byte comparisons (unsigned by default)
+        byte b1 = 200;
+        byte b2 = 100;
+        if ((b1 > b2) != true) return 90;
+        
+        // sbyte comparisons (signed)
+        sbyte sb1 = -50;
+        sbyte sb2 = 50;
+        if ((sb1 < sb2) != true) return 91;
+        
+        // short comparisons
+        short s1 = -1000;
+        short s2 = 1000;
+        if ((s1 < s2) != true) return 92;
+        if ((s1 == s2) != false) return 93;
+        
+        // long comparisons
+        long l1 = long.MaxValue;
+        long l2 = long.MinValue;
+        if ((l1 > l2) != true) return 94;
+        
+        return 0;
+    }
+    
+    // Test null comparisons
+    public static int TestNullComparisons()
+    {
+        object obj1 = null;
+        object obj2 = null;
+        object obj3 = new object();
+        
+        // Null equality
+        if ((obj1 == obj2) != true) return 100;
+        if ((obj1 == obj3) != false) return 101;
+        if ((obj3 == obj1) != false) return 102;
+        
+        // String null comparisons
+        string s1 = null;
+        string s2 = null;
+        string s3 = "";
+        
+        if ((s1 == s2) != true) return 103;
+        if ((s1 == s3) != false) return 104;
+        
+        return 0;
+    }
+    
+    public static int Main(string[] argv)
+    {
+        int result;
+        
+        result = TestCompareEqual();
+        if (result != 0) return 100 + result;
+        
+        result = TestCompareGreaterThan();
+        if (result != 0) return 200 + result;
+        
+        result = TestCompareGreaterThanUnsigned();
+        if (result != 0) return 300 + result;
+        
+        result = TestCompareLessThan();
+        if (result != 0) return 400 + result;
+        
+        result = TestCompareLessThanUnsigned();
+        if (result != 0) return 500 + result;
+        
+        result = TestComparisonCombinations();
+        if (result != 0) return 600 + result;
+        
+        result = TestMixedTypeComparisons();
+        if (result != 0) return 700 + result;
+        
+        result = TestNullComparisons();
+        if (result != 0) return 800 + result;
+        
+        return 0;
+    }
+}

WoofWare.PawPrint.Test/sourcesPure/OverlappingStructs.cs

@@ -323,10 +323,10 @@ public class StructLayoutTests
     {
         int result = 0;
 
-        result = TestSequentialLayout();
+        result = TestExplicitUnion();
         if (result != 0) return result;
 
-        result = TestExplicitUnion();
+        result = TestSequentialLayout();
         if (result != 0) return result;
 
         result = TestFixedSizeStruct();

WoofWare.PawPrint.Test/sourcesPure/Sizeof.cs

@@ -10,16 +10,16 @@ unsafe public class Program
 
     public struct MediumStruct
     {
-        public int Value1;
-        public int Value2;
+        public int MediumValue1;
+        public int MediumValue2;
     }
 
     public struct LargeStruct
     {
-        public long Value1;
-        public long Value2;
-        public long Value3;
-        public long Value4;
+        public long LongValue1;
+        public long LongValue2;
+        public long LongValue3;
+        public long LongValue4;
     }
 
     public struct NestedStruct

WoofWare.PawPrint.Test/sourcesPure/Sizeof2.cs

@@ -0,0 +1,235 @@
+using System;
+using System.Runtime.InteropServices;
+
+unsafe public class Program
+{
+    // Test for empty struct (should be 1 byte, not 0)
+    public struct EmptyStruct
+    {
+    }
+
+    // Test for char alignment (should align to 2, not 1)
+    public struct CharStruct
+    {
+        public byte B;
+        public char C;  // Should be at offset 2, not 1
+    }
+
+    // Test for end padding
+    public struct NeedsEndPadding
+    {
+        public int X;
+        public byte Y;
+        // Should pad to 8 bytes total (multiple of 4)
+    }
+
+    // Test Pack=1 (no padding)
+    [StructLayout(LayoutKind.Sequential, Pack = 1)]
+    public struct PackedStruct
+    {
+        public byte B;
+        public int I;   // At offset 1, not 4
+        public byte B2;
+        // Total 6 bytes, no padding
+    }
+
+    // Test Pack=2
+    [StructLayout(LayoutKind.Sequential, Pack = 2)]
+    public struct Pack2Struct
+    {
+        public byte B;
+        public int I;   // At offset 2 (2-byte aligned, not 4)
+        public byte B2;
+        // Should pad to 8 bytes (multiple of 2)
+    }
+
+    // Test custom size smaller than natural size
+    [StructLayout(LayoutKind.Sequential, Size = 12)]
+    public struct CustomSizeSmaller
+    {
+        public long L1;
+        public long L2;
+        // Natural size is 16, but Size=12 is ignored (12 < 16)
+    }
+
+    // Test custom size larger than natural size
+    [StructLayout(LayoutKind.Sequential, Size = 20)]
+    public struct CustomSizeLarger
+    {
+        public long L;
+        // Natural size is 8, custom size 20 should win
+    }
+
+    // Test custom size not multiple of alignment
+    [StructLayout(LayoutKind.Sequential, Size = 15)]
+    public struct CustomSizeOdd
+    {
+        public long L;
+        // Size=15 should be honored even though not multiple of 8
+    }
+
+    // Test Pack=0 (means default, not 0)
+    [StructLayout(LayoutKind.Sequential, Pack = 0)]
+    public struct Pack0Struct
+    {
+        public byte B;
+        public int I;  // Should be at offset 4 (default packing)
+    }
+
+    // Test both Pack and Size
+    [StructLayout(LayoutKind.Sequential, Pack = 1, Size = 10)]
+    public struct PackAndSize
+    {
+        public byte B;
+        public int I;
+        // Natural packed size is 5, custom size 10 should win
+    }
+
+    // Test explicit with custom Size
+    [StructLayout(LayoutKind.Explicit, Size = 10)]
+    public struct ExplicitWithSize
+    {
+        [FieldOffset(0)]
+        public int I;
+        [FieldOffset(2)]
+        public short S;
+        // Max offset+size is 4, but Size=10 should win
+    }
+
+    public struct SmallStruct
+    {
+        public byte Value;
+    }
+
+    public struct MediumStruct
+    {
+        public int MediumValue1;
+        public int MediumValue2;
+    }
+
+    public struct LargeStruct
+    {
+        public long LongValue1;
+        public long LongValue2;
+        public long LongValue3;
+        public long LongValue4;
+    }
+
+    public struct NestedStruct
+    {
+        public SmallStruct Small;
+        public MediumStruct Medium;
+        public int Extra;
+    }
+
+    [StructLayout(LayoutKind.Explicit)]
+    public struct UnionStruct
+    {
+        [FieldOffset(0)]
+        public int AsInt;
+        [FieldOffset(0)]
+        public float AsFloat;
+    }
+
+    public static int Main(string[] args)
+    {
+        // Test 1: Basic primitive types
+        if (sizeof(byte) != 1) return 1;
+        if (sizeof(sbyte) != 1) return 2;
+        if (sizeof(short) != 2) return 3;
+        if (sizeof(ushort) != 2) return 4;
+        if (sizeof(int) != 4) return 5;
+        if (sizeof(uint) != 4) return 6;
+        if (sizeof(long) != 8) return 7;
+        if (sizeof(ulong) != 8) return 8;
+        if (sizeof(float) != 4) return 9;
+        if (sizeof(double) != 8) return 10;
+        if (sizeof(char) != 2) return 11;
+        if (sizeof(bool) != 1) return 12;
+
+        // Test 2: Struct sizes
+        if (sizeof(SmallStruct) != 1) return 13;
+        if (sizeof(MediumStruct) != 8) return 14;
+        if (sizeof(LargeStruct) != 32) return 15;
+
+        // Test 3: Nested struct size
+        // SmallStruct (1) + padding (3) + MediumStruct (8) + int (4) = 16
+        if (sizeof(NestedStruct) != 16) return 16;
+
+        // Test 4: Union struct size
+        if (sizeof(UnionStruct) != 4) return 17;
+
+        // Test 5: Enum size (underlying type is int)
+        if (sizeof(DayOfWeek) != 4) return 18;
+
+        // Test 6: Empty struct (should be 1, not 0)
+        if (sizeof(EmptyStruct) != 1) return 19;
+
+        // Test 7: Char alignment
+        // byte (1) + padding (1) + char (2) = 4
+        if (sizeof(CharStruct) != 4) return 20;
+
+        // Test 8: End padding
+        // int (4) + byte (1) + padding (3) = 8
+        if (sizeof(NeedsEndPadding) != 8) return 21;
+
+        // Test 9: Pack=1 removes all padding
+        // byte (1) + int (4) + byte (1) = 6
+        if (sizeof(PackedStruct) != 6) return 22;
+
+        // Test 10: Pack=2
+        // byte (1) + padding (1) + int (4) + byte (1) + padding (1) = 8
+        if (sizeof(Pack2Struct) != 8) return 23;
+
+        // Test 11: Custom size smaller than natural (ignored)
+        if (sizeof(CustomSizeSmaller) != 16) return 24;
+
+        // Test 12: Custom size larger than natural (honored)
+        if (sizeof(CustomSizeLarger) != 20) return 25;
+
+        // Test 13: Custom size not multiple of alignment (honored)
+        if (sizeof(CustomSizeOdd) != 15) return 26;
+
+        // Test 14: Pack=0 means default packing
+        // byte (1) + padding (3) + int (4) = 8
+        if (sizeof(Pack0Struct) != 8) return 27;
+
+        // Test 15: Pack and Size together
+        // Natural packed: byte (1) + int (4) = 5, but Size=10
+        if (sizeof(PackAndSize) != 10) return 28;
+
+        // Test 16: Explicit with Size
+        // Max used is 4, but Size=10
+        if (sizeof(ExplicitWithSize) != 10) return 29;
+
+        // Test 17: Pointer types
+        unsafe
+        {
+            if (sizeof(IntPtr) != sizeof(void*)) return 30;
+            if (sizeof(UIntPtr) != sizeof(void*)) return 31;
+        }
+
+        // Test 18: Using sizeof in expressions
+        int totalSize = sizeof(int) + sizeof(long) + sizeof(byte);
+        if (totalSize != 13) return 32;
+
+        // Test 19: Array element size calculation
+        int arrayElementSize = sizeof(MediumStruct);
+        int arraySize = arrayElementSize * 3;
+        if (arraySize != 24) return 33;
+
+        // Test 20: Complex nested struct with Pack
+        // byte (1) + CharStruct (4) + byte (1) = 6
+        if (sizeof(PackedNested) != 6) return 34;
+
+        return 0;
+    }
+
+    [StructLayout(LayoutKind.Sequential, Pack = 1)]
+    struct PackedNested
+    {
+        public byte B;
+        public CharStruct C;
+        public byte B2;
+    }
+}

WoofWare.PawPrint.Test/sourcesPure/StackOperations.cs

@@ -0,0 +1,184 @@
+public class TestStackOperations
+{
+    // Test LdArg0-3: Load method arguments
+    public static int TestLoadArguments(int arg0, int arg1, int arg2, int arg3)
+    {
+        // LdArg0 loads 'this' for instance methods or first arg for static
+        if (arg0 != 10) return 1;
+
+        // LdArg1 loads second argument
+        if (arg1 != 20) return 2;
+
+        // LdArg2 loads third argument
+        if (arg2 != 30) return 3;
+
+        // LdArg3 loads fourth argument
+        if (arg3 != 40) return 4;
+
+        return 0;
+    }
+
+    // Test Ldloc_0-3 and Stloc_0-3: Load/store local variables
+    public static int TestLocalVariables()
+    {
+        int local0 = 100;
+        int local1 = 200;
+        int local2 = 300;
+        int local3 = 400;
+
+        // Test loading locals
+        if (local0 != 100) return 10;
+        if (local1 != 200) return 11;
+        if (local2 != 300) return 12;
+        if (local3 != 400) return 13;
+
+        // Test storing to locals
+        local0 = local1 + local2;  // Stloc_0
+        if (local0 != 500) return 14;
+
+        local1 = local2 * 2;  // Stloc_1
+        if (local1 != 600) return 15;
+
+        local2 = local3 - 100;  // Stloc_2
+        if (local2 != 300) return 16;
+
+        local3 = local0 / 5;  // Stloc_3
+        if (local3 != 100) return 17;
+
+        return 0;
+    }
+
+    // Test Pop: Remove top stack value
+    public static int TestPop()
+    {
+        int value = 42;
+
+        // Push value on stack then pop it
+        PushAndPop(value);
+
+        // If we get here, pop worked
+        return 0;
+    }
+
+    private static void PushAndPop(int value)
+    {
+        // The compiler will generate pop instructions
+        // for unused return values
+        GetValue();
+        GetValue();
+    }
+
+    private static int GetValue()
+    {
+        return 123;
+    }
+
+    // Test Dup: Duplicate top stack value
+    public static int TestDup()
+    {
+        int value = 50;
+
+        // Dup is used when same value is needed twice
+        int result1 = value * value;  // Compiler may use dup here
+        if (result1 != 2500) return 20;
+
+        // More complex dup scenario
+        int x = 10;
+        int result2 = AddTwice(x);
+        if (result2 != 20) return 21;
+
+        return 0;
+    }
+
+    private static int AddTwice(int val)
+    {
+        // Compiler may generate dup to use val twice
+        return val + val;
+    }
+
+    // Test Ret: Return from method
+    public static int TestReturn()
+    {
+        // Test void return
+        VoidReturn();
+
+        // Test value return
+        int result = ValueReturn(5);
+        if (result != 5) return 30;
+
+        // Test early return
+        result = EarlyReturn(true);
+        if (result != 1) return 31;
+
+        result = EarlyReturn(false);
+        if (result != 2) return 32;
+
+        return 0;
+    }
+
+    private static void VoidReturn()
+    {
+        // Ret with no value
+        return;
+    }
+
+    private static int ValueReturn(int x)
+    {
+        // Ret with value
+        return x;
+    }
+
+    private static int EarlyReturn(bool condition)
+    {
+        if (condition)
+            return 1;  // Early ret
+
+        return 2;  // Normal ret
+    }
+
+    // Test combinations of stack operations
+    public static int TestStackCombinations()
+    {
+        int a = 10, b = 20, c = 30;
+
+        // Complex expression using multiple locals
+        int result = (a + b) * c - (b - a);
+        if (result != 890) return 40;
+
+        // Nested method calls
+        result = Compute(a, Compute(b, c));
+        if (result != 60) return 41;
+
+        return 0;
+    }
+
+    private static int Compute(int x, int y)
+    {
+        return x + y;
+    }
+
+    public static int Main(string[] argv)
+    {
+        int result;
+
+        result = TestLoadArguments(10, 20, 30, 40);
+        if (result != 0) return 100 + result;
+
+        result = TestLocalVariables();
+        if (result != 0) return 200 + result;
+
+        result = TestPop();
+        if (result != 0) return 300 + result;
+
+        result = TestDup();
+        if (result != 0) return 400 + result;
+
+        result = TestReturn();
+        if (result != 0) return 500 + result;
+
+        result = TestStackCombinations();
+        if (result != 0) return 600 + result;
+
+        return 0;
+    }
+}

WoofWare.PawPrint/AbstractMachine.fs

@@ -42,7 +42,7 @@ module AbstractMachine =
                 | Some {
                            WasConstructingObj = Some _
                        } ->
-                    IlMachineState.executeDelegateConstructor instruction state
+                    IlMachineState.executeDelegateConstructor baseClassTypes instruction state
                     // can't advance the program counter here - there's no IL instructions executing!
                     |> IlMachineState.returnStackFrame loggerFactory baseClassTypes thread
                     |> Option.get
@@ -54,7 +54,7 @@ module AbstractMachine =
                     // We've been instructed to run a delegate.
                     let delegateToRunAddr =
                         match instruction.Arguments.[0] with
-                        | CliType.RuntimePointer (CliRuntimePointer.Managed (CliRuntimePointerSource.Heap addr))
+                        | CliType.RuntimePointer (CliRuntimePointer.Managed (ManagedPointerSource.Heap addr))
                         | CliType.ObjectRef (Some addr) -> addr
                         | _ -> failwith "expected a managed object ref to delegate"
 
@@ -222,5 +222,5 @@ module AbstractMachine =
             |> ExecutionResult.Stepped
         | IlOp.Switch immutableArray -> failwith "TODO: Switch unimplemented"
         | IlOp.UnaryStringToken (unaryStringTokenIlOp, stringHandle) ->
-            UnaryStringTokenIlOp.execute baseClassTypes unaryStringTokenIlOp stringHandle state thread
+            UnaryStringTokenIlOp.execute loggerFactory baseClassTypes unaryStringTokenIlOp stringHandle state thread
             |> ExecutionResult.Stepped

WoofWare.PawPrint/BasicCliType.fs

@@ -1,8 +1,9 @@
 namespace WoofWare.PawPrint
 
+open System
 open System.Collections.Immutable
 open System.Reflection
-open System.Reflection.Metadata
+open Checked
 
 /// Source:
 /// Table I.6: Data Types Directly Supported by the CLI
@@ -43,6 +44,7 @@ type ManagedPointerSource =
     | ArrayIndex of arr : ManagedHeapAddress * index : int
     | Field of ManagedPointerSource * fieldName : string
     | Null
+    | InterpretedAsType of ManagedPointerSource * ConcreteType<ConcreteTypeHandle>
 
     override this.ToString () =
         match this with
@@ -54,6 +56,7 @@ type ManagedPointerSource =
             $"<argument %i{var} in method frame %i{method} of thread %O{source}>"
         | ManagedPointerSource.ArrayIndex (arr, index) -> $"<index %i{index} of array %O{arr}>"
         | ManagedPointerSource.Field (source, name) -> $"<field %s{name} of %O{source}>"
+        | ManagedPointerSource.InterpretedAsType (src, ty) -> $"<%O{src} as %s{ty.Namespace}.%s{ty.Name}>"
 
 [<RequireQualifiedAccess>]
 type UnsignedNativeIntSource =
@@ -66,6 +69,7 @@ type NativeIntSource =
     | ManagedPointer of ManagedPointerSource
     | FunctionPointer of MethodInfo<ConcreteTypeHandle, ConcreteTypeHandle, ConcreteTypeHandle>
     | TypeHandlePtr of ConcreteTypeHandle
+    | FieldHandlePtr of int64
 
     override this.ToString () : string =
         match this with
@@ -74,12 +78,14 @@ type NativeIntSource =
         | NativeIntSource.FunctionPointer methodDefinition ->
             $"<pointer to {methodDefinition.Name} in {methodDefinition.DeclaringType.Assembly.Name}>"
         | NativeIntSource.TypeHandlePtr ptr -> $"<type ID %O{ptr}>"
+        | NativeIntSource.FieldHandlePtr ptr -> $"<field ID %O{ptr}>"
 
 [<RequireQualifiedAccess>]
 module NativeIntSource =
     let isZero (n : NativeIntSource) : bool =
         match n with
         | NativeIntSource.Verbatim i -> i = 0L
+        | NativeIntSource.FieldHandlePtr _
         | NativeIntSource.TypeHandlePtr _ -> false
         | NativeIntSource.FunctionPointer _ -> failwith "TODO"
         | NativeIntSource.ManagedPointer src ->
@@ -91,6 +97,7 @@ module NativeIntSource =
         match n with
         | NativeIntSource.Verbatim i -> i >= 0L
         | NativeIntSource.FunctionPointer _ -> failwith "TODO"
+        | NativeIntSource.FieldHandlePtr _
         | NativeIntSource.TypeHandlePtr _ -> true
         | NativeIntSource.ManagedPointer _ -> true
 
@@ -115,46 +122,51 @@ type CliNumericType =
     | Float32 of float32
     | Float64 of float
 
-[<RequireQualifiedAccess>]
-type CliRuntimePointerSource =
-    | LocalVariable of sourceThread : ThreadId * methodFrame : int * whichVar : uint16
-    | Argument of sourceThread : ThreadId * methodFrame : int * whichVar : uint16
-    | Field of source : CliRuntimePointerSource * fieldName : string
-    | Heap of ManagedHeapAddress
-    | ArrayIndex of arr : ManagedHeapAddress * index : int
-    | Null
+    static member SizeOf (t : CliNumericType) : int =
+        match t with
+        | CliNumericType.Int32 _ -> 4
+        | CliNumericType.Int64 _ -> 8
+        | CliNumericType.NativeInt _ -> 8
+        | CliNumericType.NativeFloat _ -> 8
+        | CliNumericType.Int8 _ -> 1
+        | CliNumericType.Int16 _ -> 2
+        | CliNumericType.UInt8 _ -> 1
+        | CliNumericType.UInt16 _ -> 2
+        | CliNumericType.Float32 _ -> 4
+        | CliNumericType.Float64 _ -> 8
 
-[<RequireQualifiedAccess>]
-module CliRuntimePointerSource =
-    let rec ofManagedPointerSource (ptrSource : ManagedPointerSource) : CliRuntimePointerSource =
-        match ptrSource with
-        | ManagedPointerSource.LocalVariable (sourceThread, methodFrame, whichVar) ->
-            CliRuntimePointerSource.LocalVariable (sourceThread, methodFrame, whichVar)
-        | ManagedPointerSource.Argument (sourceThread, methodFrame, whichVar) ->
-            CliRuntimePointerSource.Argument (sourceThread, methodFrame, whichVar)
-        | ManagedPointerSource.Heap managedHeapAddress -> CliRuntimePointerSource.Heap managedHeapAddress
-        | ManagedPointerSource.Null -> CliRuntimePointerSource.Null
-        | ManagedPointerSource.ArrayIndex (arr, ind) -> CliRuntimePointerSource.ArrayIndex (arr, ind)
-        | ManagedPointerSource.Field (a, ind) ->
-            let a = ofManagedPointerSource a
-            CliRuntimePointerSource.Field (a, ind)
-
-    let rec toManagedPointerSource (ptrSource : CliRuntimePointerSource) : ManagedPointerSource =
-        match ptrSource with
-        | CliRuntimePointerSource.LocalVariable (sourceThread, methodFrame, whichVar) ->
-            ManagedPointerSource.LocalVariable (sourceThread, methodFrame, whichVar)
-        | CliRuntimePointerSource.Argument (sourceThread, methodFrame, whichVar) ->
-            ManagedPointerSource.Argument (sourceThread, methodFrame, whichVar)
-        | CliRuntimePointerSource.Heap managedHeapAddress -> ManagedPointerSource.Heap managedHeapAddress
-        | CliRuntimePointerSource.Null -> ManagedPointerSource.Null
-        | CliRuntimePointerSource.ArrayIndex (arr, ind) -> ManagedPointerSource.ArrayIndex (arr, ind)
-        | CliRuntimePointerSource.Field (a, ind) ->
-            let a = toManagedPointerSource a
-            ManagedPointerSource.Field (a, ind)
+    static member ToBytes (t : CliNumericType) : byte[] =
+        match t with
+        | CliNumericType.Int32 i -> BitConverter.GetBytes i
+        | CliNumericType.Int64 i -> BitConverter.GetBytes i
+        | CliNumericType.NativeInt src ->
+            match src with
+            | NativeIntSource.Verbatim i -> BitConverter.GetBytes i
+            | NativeIntSource.ManagedPointer src ->
+                match src with
+                | ManagedPointerSource.Null -> BitConverter.GetBytes 0L
+                | _ -> failwith "refusing to express pointer as bytes"
+            | NativeIntSource.FieldHandlePtr _ -> failwith "refusing to express FieldHandlePtr as bytes"
+            | NativeIntSource.FunctionPointer _ -> failwith "refusing to express FunctionPointer as bytes"
+            | NativeIntSource.TypeHandlePtr _ -> failwith "refusing to express TypeHandlePtr as bytes"
+        | CliNumericType.NativeFloat f -> BitConverter.GetBytes f
+        | CliNumericType.Int8 i -> BitConverter.GetBytes i
+        | CliNumericType.Int16 i -> BitConverter.GetBytes i
+        | CliNumericType.UInt8 i -> BitConverter.GetBytes i
+        | CliNumericType.UInt16 i -> BitConverter.GetBytes i
+        | CliNumericType.Float32 i -> BitConverter.GetBytes i
+        | CliNumericType.Float64 i -> BitConverter.GetBytes i
 
 type CliRuntimePointer =
-    | Unmanaged of int64
-    | Managed of CliRuntimePointerSource
+    | Verbatim of int64
+    | FieldRegistryHandle of int64
+    | Managed of ManagedPointerSource
+
+type SizeofResult =
+    {
+        Alignment : int
+        Size : int
+    }
 
 /// This is the kind of type that can be stored in arguments, local variables, statics, array elements, fields.
 type CliType =
@@ -172,27 +184,349 @@ type CliType =
     /// as a concatenated list of its fields.
     | ValueType of CliValueType
 
+    static member SizeOf (t : CliType) : SizeofResult =
+        match t with
+        | CliType.Numeric ty ->
+            let size = CliNumericType.SizeOf ty
+
+            {
+                Size = size
+                Alignment = size
+            }
+        | CliType.Bool _ ->
+            {
+                Size = 1
+                Alignment = 1
+            }
+        | CliType.Char _ ->
+            {
+                Size = 2
+                Alignment = 2
+            }
+        | CliType.ObjectRef _ ->
+            {
+                Size = 8
+                Alignment = 8
+            }
+        | CliType.RuntimePointer _ ->
+            {
+                Size = 8
+                Alignment = 8
+            }
+        | CliType.ValueType vt -> CliValueType.SizeOf vt
+
+    static member ToBytes (t : CliType) : byte[] =
+        match t with
+        | CliType.Numeric n -> CliNumericType.ToBytes n
+        | CliType.Bool b -> [| b |]
+        | CliType.Char (high, low) -> [| low ; high |]
+        | CliType.ObjectRef None -> Array.zeroCreate NATIVE_INT_SIZE
+        | CliType.ObjectRef (Some i) -> failwith "todo"
+        | CliType.RuntimePointer cliRuntimePointer -> failwith "todo"
+        | CliType.ValueType cvt -> CliValueType.ToBytes cvt
+
+    static member OfBytesAsType (targetType : ConcreteTypeHandle) (bytes : byte[]) : CliType = failwith "TODO"
+
 and CliField =
     {
         Name : string
         Contents : CliType
         /// "None" for "no explicit offset specified"; we expect most offsets to be None.
         Offset : int option
+        Type : ConcreteTypeHandle
     }
 
-and CliValueType =
-    {
-        Fields : CliField list
-    }
-
-    static member OfFields (f : CliField list) =
+and CliConcreteField =
+    private
         {
-            Fields = f
+            Name : string
+            Contents : CliType
+            Offset : int
+            Size : int
+            Alignment : int
+            ConfiguredOffset : int option
+            EditedAtTime : uint64
+            Type : ConcreteTypeHandle
         }
 
-    static member DereferenceField (name : string) (f : CliValueType) : CliType =
-        // TODO: this is wrong, it doesn't account for overlapping fields
-        f.Fields |> List.find (fun f -> f.Name = name) |> _.Contents
+    static member ToCliField (this : CliConcreteField) : CliField =
+        {
+            Offset = this.ConfiguredOffset
+            Contents = this.Contents
+            Name = this.Name
+            Type = this.Type
+        }
+
+and CliValueType =
+    private
+        {
+            _Fields : CliConcreteField list
+            Layout : Layout
+            /// We track dependency orderings between updates to overlapping fields with a monotonically increasing
+            /// timestamp.
+            NextTimestamp : uint64
+        }
+
+    static member private ComputeConcreteFields (layout : Layout) (fields : CliField list) : CliConcreteField list =
+        // Minimum size only matters for `sizeof` computation
+        let _minimumSize, packingSize =
+            match layout with
+            | Layout.Custom (size = size ; packingSize = packing) ->
+                size, if packing = 0 then DEFAULT_STRUCT_ALIGNMENT else packing
+            | Layout.Default -> 0, DEFAULT_STRUCT_ALIGNMENT
+
+        let seqFields, nonSeqFields =
+            fields |> List.partition (fun field -> field.Offset.IsNone)
+
+        match seqFields, nonSeqFields with
+        | [], [] -> []
+        | _ :: _, [] ->
+            // Sequential layout: compute offsets respecting alignment
+            let _, concreteFields =
+                ((0, []), seqFields)
+                ||> List.fold (fun (currentOffset, acc) field ->
+                    let size = CliType.SizeOf field.Contents
+                    let alignmentCap = min size.Alignment packingSize
+                    let error = currentOffset % alignmentCap
+
+                    let alignedOffset =
+                        if error > 0 then
+                            currentOffset + (alignmentCap - error)
+                        else
+                            currentOffset
+
+                    let concreteField =
+                        {
+                            Name = field.Name
+                            Contents = field.Contents
+                            Offset = alignedOffset
+                            Size = size.Size
+                            Alignment = size.Alignment
+                            ConfiguredOffset = field.Offset
+                            EditedAtTime = 0UL
+                            Type = field.Type
+                        }
+
+                    alignedOffset + size.Size, concreteField :: acc
+                )
+
+            List.rev concreteFields
+
+        | [], _ :: _ ->
+            // Explicit layout: use provided offsets
+            nonSeqFields
+            |> List.map (fun field ->
+                let size = CliType.SizeOf field.Contents
+
+                {
+                    Name = field.Name
+                    Contents = field.Contents
+                    Offset = field.Offset.Value
+                    Size = size.Size
+                    Alignment = size.Alignment
+                    ConfiguredOffset = field.Offset
+                    EditedAtTime = 0UL
+                    Type = field.Type
+                }
+            )
+
+        | _ :: _, _ :: _ -> failwith "unexpectedly mixed explicit and automatic layout of fields"
+
+    static member ToBytes (cvt : CliValueType) : byte[] =
+        let bytes = Array.zeroCreate<byte> (CliValueType.SizeOf(cvt).Size)
+
+        cvt._Fields
+        |> List.sortBy _.EditedAtTime
+        |> List.iter (fun candidateField ->
+            let fieldBytes : byte[] = CliType.ToBytes candidateField.Contents
+
+            for i = 0 to candidateField.Size - 1 do
+                bytes.[candidateField.Offset + i] <- fieldBytes.[i]
+        )
+
+        bytes
+
+    static member OfFields (layout : Layout) (f : CliField list) : CliValueType =
+        let fields = CliValueType.ComputeConcreteFields layout f
+
+        {
+            _Fields = fields
+            Layout = layout
+            NextTimestamp = 1UL
+        }
+
+    static member AddField (f : CliField) (vt : CliValueType) : CliValueType =
+        // Recompute all fields with the new one added
+        // TODO: the existence of this function at all is rather dubious, but it's there
+        // at the moment to support delegate types.
+        // The whole function is just a bodge and it will hopefully go away soon; I just don't know how.
+        let prevFields = vt._Fields |> List.map (fun f -> f.Name, f) |> Map.ofList
+
+        let allFields =
+            f
+            :: (vt._Fields
+                |> List.map (fun cf ->
+                    {
+                        Name = cf.Name
+                        Contents = cf.Contents
+                        Offset =
+                            match vt.Layout with
+                            | Layout.Default -> None
+                            | Layout.Custom _ -> Some cf.Offset
+                        Type = cf.Type
+                    }
+                ))
+
+        let newFields =
+            CliValueType.ComputeConcreteFields vt.Layout allFields
+            |> List.map (fun field ->
+                match Map.tryFind field.Name prevFields with
+                | Some prev ->
+                    { field with
+                        EditedAtTime = prev.EditedAtTime
+                    }
+                | None ->
+                    { field with
+                        EditedAtTime = vt.NextTimestamp
+                    }
+            )
+
+        {
+            _Fields = newFields
+            Layout = vt.Layout
+            NextTimestamp = vt.NextTimestamp + 1UL
+        }
+
+    /// Returns the offset and size.
+    static member GetFieldLayout (field : string) (cvt : CliValueType) : int * int =
+        let targetField =
+            cvt._Fields
+            |> List.tryFind (fun f -> f.Name = field)
+            |> Option.defaultWith (fun () -> failwithf $"Field '%s{field}' not found")
+
+        targetField.Offset, targetField.Size
+
+    // TODO: use DereferenceFieldAt for the implementation.
+    // We should eventually be able to dereference an arbitrary field of a struct
+    // as though it were any other field of any other type, to accommodate Unsafe.As.
+    static member DereferenceField (field : string) (cvt : CliValueType) : CliType =
+        let targetField =
+            cvt._Fields
+            |> List.tryFind (fun f -> f.Name = field)
+            |> Option.defaultWith (fun () -> failwithf $"Field '%s{field}' not found")
+
+        // Identify all fields that overlap with the target field's memory range
+        let targetStart = targetField.Offset
+        let targetEnd = targetField.Offset + targetField.Size
+
+        let affectedFields =
+            cvt._Fields
+            |> List.filter (fun f ->
+                let fieldStart = f.Offset
+                let fieldEnd = f.Offset + f.Size
+                // Fields overlap if their ranges intersect
+                fieldStart < targetEnd && targetStart < fieldEnd
+            )
+
+        match affectedFields with
+        | [] -> failwith "unexpectedly didn't dereference a field"
+        | [ f ] -> f.Contents
+        | fields ->
+            let bytes = CliValueType.ToBytes cvt
+
+            let fieldBytes =
+                bytes.[targetField.Offset .. targetField.Offset + targetField.Size - 1]
+
+            CliType.OfBytesAsType targetField.Type fieldBytes
+
+    static member FieldsAt (offset : int) (cvt : CliValueType) : CliConcreteField list =
+        cvt._Fields |> List.filter (fun f -> f.Offset = offset)
+
+    static member DereferenceFieldAt (offset : int) (size : int) (cvt : CliValueType) : CliType =
+        let targetField =
+            CliValueType.FieldsAt offset cvt |> List.tryFind (fun f -> f.Size = size)
+
+        match targetField with
+        | None -> failwith "TODO: couldn't find the field"
+        | Some f -> f.Contents
+
+    static member SizeOf (vt : CliValueType) : SizeofResult =
+        let minimumSize, packingSize =
+            match vt.Layout with
+            | Layout.Custom (size = size ; packingSize = packing) ->
+                size, if packing = 0 then DEFAULT_STRUCT_ALIGNMENT else packing
+            | Layout.Default -> 0, DEFAULT_STRUCT_ALIGNMENT
+
+        if vt._Fields.IsEmpty then
+            {
+                Size = minimumSize
+                Alignment = 1
+            }
+        else
+            // Now we can just use the precomputed offsets and sizes
+            let finalOffset, alignment =
+                vt._Fields
+                |> List.fold
+                    (fun (maxEnd, maxAlign) field ->
+                        let fieldEnd = field.Offset + field.Size
+                        let alignmentCap = min field.Alignment packingSize
+                        max maxEnd fieldEnd, max maxAlign alignmentCap
+                    )
+                    (0, 0)
+
+            let error = finalOffset % alignment
+
+            let size =
+                if error = 0 then
+                    finalOffset
+                else
+                    finalOffset + (alignment - error)
+
+            {
+                Size = max size minimumSize
+                Alignment = alignment
+            }
+
+    /// Sets the value of the specified field, *without* touching any overlapping fields.
+    /// `DereferenceField` handles resolving conflicts between overlapping fields.
+    static member WithFieldSet (field : string) (value : CliType) (cvt : CliValueType) : CliValueType =
+        {
+            Layout = cvt.Layout
+            _Fields =
+                cvt._Fields
+                |> List.replaceWhere (fun f ->
+                    if f.Name = field then
+                        { f with
+                            Contents = value
+                            EditedAtTime = cvt.NextTimestamp
+                        }
+                        |> Some
+                    else
+                        None
+                )
+            NextTimestamp = cvt.NextTimestamp + 1UL
+        }
+
+    /// To facilitate bodges. This function absolutely should not exist.
+    static member TryExactlyOneField (cvt : CliValueType) : CliField option =
+        match cvt._Fields with
+        | [] -> None
+        | [ x ] ->
+            if x.Offset = 0 then
+                Some (CliConcreteField.ToCliField x)
+            else
+                None
+        | _ -> None
+
+    /// To facilitate bodges. This function absolutely should not exist.
+    static member TrySequentialFields (cvt : CliValueType) : CliField list option =
+        let isNone, isSome =
+            cvt._Fields |> List.partition (fun field -> field.ConfiguredOffset.IsNone)
+
+        match isSome with
+        | [] -> Some (isNone |> List.map CliConcreteField.ToCliField)
+        | [ field ] when field.ConfiguredOffset = Some 0 -> Some [ CliConcreteField.ToCliField field ]
+        | _ -> None
 
 type CliTypeResolutionResult =
     | Resolved of CliType
@@ -208,33 +542,14 @@ module CliType =
 
     let ofManagedObject (ptr : ManagedHeapAddress) : CliType = CliType.ObjectRef (Some ptr)
 
-    let rec sizeOf (ty : CliType) : int =
-        match ty with
-        | CliType.Numeric ty ->
-            match ty with
-            | CliNumericType.Int32 _ -> 4
-            | CliNumericType.Int64 _ -> 8
-            | CliNumericType.NativeInt _ -> 8
-            | CliNumericType.NativeFloat _ -> 8
-            | CliNumericType.Int8 _ -> 1
-            | CliNumericType.Int16 _ -> 2
-            | CliNumericType.UInt8 _ -> 1
-            | CliNumericType.UInt16 _ -> 2
-            | CliNumericType.Float32 _ -> 4
-            | CliNumericType.Float64 _ -> 8
-        | CliType.Bool _ -> 1
-        | CliType.Char _ -> 2
-        | CliType.ObjectRef _ -> 8
-        | CliType.RuntimePointer _ -> 8
-        | CliType.ValueType vt ->
-            match vt.Fields with
-            | [] -> failwith "is it even possible to instantiate a value type with no fields"
-            | [ field ] -> sizeOf field.Contents
-            | fields ->
-                // TODO: consider struct layout (there's an `Explicit` test that will exercise that)
-                fields |> List.map (_.Contents >> sizeOf) |> List.sum
+    let sizeOf (ty : CliType) : int = CliType.SizeOf(ty).Size
 
-    let zeroOfPrimitive (primitiveType : PrimitiveType) : CliType =
+    let zeroOfPrimitive
+        (concreteTypes : AllConcreteTypes)
+        (corelib : BaseClassTypes<DumpedAssembly>)
+        (primitiveType : PrimitiveType)
+        : CliType
+        =
         match primitiveType with
         | PrimitiveType.Boolean -> CliType.Bool 0uy
         | PrimitiveType.Char -> CliType.Char (0uy, 0uy)
@@ -257,20 +572,36 @@ module CliType =
         | PrimitiveType.IntPtr ->
             {
                 Name = "_value"
-                Contents = CliType.RuntimePointer (CliRuntimePointer.Managed CliRuntimePointerSource.Null)
-                Offset = Some 0
+                Contents =
+                    CliType.Numeric (
+                        CliNumericType.NativeInt (NativeIntSource.ManagedPointer ManagedPointerSource.Null)
+                    )
+                Offset = None
+                Type =
+                    AllConcreteTypes.findExistingConcreteType
+                        concreteTypes
+                        (corelib.IntPtr.Assembly, corelib.IntPtr.Namespace, corelib.IntPtr.Name, ImmutableArray.Empty)
+                    |> Option.get
             }
             |> List.singleton
-            |> CliValueType.OfFields
+            |> CliValueType.OfFields Layout.Default
             |> CliType.ValueType
         | PrimitiveType.UIntPtr ->
             {
                 Name = "_value"
-                Contents = CliType.RuntimePointer (CliRuntimePointer.Managed CliRuntimePointerSource.Null)
-                Offset = Some 0
+                Contents =
+                    CliType.Numeric (
+                        CliNumericType.NativeInt (NativeIntSource.ManagedPointer ManagedPointerSource.Null)
+                    )
+                Offset = None
+                Type =
+                    AllConcreteTypes.findExistingConcreteType
+                        concreteTypes
+                        (corelib.UIntPtr.Assembly, corelib.UIntPtr.Namespace, corelib.UIntPtr.Name, ImmutableArray.Empty)
+                    |> Option.get
             }
             |> List.singleton
-            |> CliValueType.OfFields
+            |> CliValueType.OfFields Layout.Default
             |> CliType.ValueType
         | PrimitiveType.Object -> CliType.ObjectRef None
 
@@ -296,11 +627,11 @@ module CliType =
         match handle with
         | ConcreteTypeHandle.Byref _ ->
             // Byref types are managed references - the zero value is a null reference
-            CliType.RuntimePointer (CliRuntimePointer.Managed CliRuntimePointerSource.Null), concreteTypes
+            CliType.RuntimePointer (CliRuntimePointer.Managed ManagedPointerSource.Null), concreteTypes
 
         | ConcreteTypeHandle.Pointer _ ->
             // Pointer types are unmanaged pointers - the zero value is a null pointer
-            CliType.RuntimePointer (CliRuntimePointer.Unmanaged 0L), concreteTypes
+            CliType.RuntimePointer (CliRuntimePointer.Managed ManagedPointerSource.Null), concreteTypes
 
         | ConcreteTypeHandle.Concrete _ ->
             // This is a concrete type - look it up in the mapping
@@ -314,72 +645,82 @@ module CliType =
             let typeDef = assembly.TypeDefs.[concreteType.Definition.Get]
 
             // Check if it's a primitive type by comparing with corelib types FIRST
-            if concreteType.Assembly = corelib.Corelib.Name && concreteType.Generics.IsEmpty then
+            if
+                concreteType.Assembly.FullName = corelib.Corelib.Name.FullName
+                && concreteType.Generics.IsEmpty
+            then
                 // Check against known primitive types
                 if TypeInfo.NominallyEqual typeDef corelib.Boolean then
-                    zeroOfPrimitive PrimitiveType.Boolean, concreteTypes
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.Boolean, concreteTypes
                 elif TypeInfo.NominallyEqual typeDef corelib.Char then
-                    zeroOfPrimitive PrimitiveType.Char, concreteTypes
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.Char, concreteTypes
                 elif TypeInfo.NominallyEqual typeDef corelib.SByte then
-                    zeroOfPrimitive PrimitiveType.SByte, concreteTypes
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.SByte, concreteTypes
                 elif TypeInfo.NominallyEqual typeDef corelib.Byte then
-                    zeroOfPrimitive PrimitiveType.Byte, concreteTypes
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.Byte, concreteTypes
                 elif TypeInfo.NominallyEqual typeDef corelib.Int16 then
-                    zeroOfPrimitive PrimitiveType.Int16, concreteTypes
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.Int16, concreteTypes
                 elif TypeInfo.NominallyEqual typeDef corelib.UInt16 then
-                    zeroOfPrimitive PrimitiveType.UInt16, concreteTypes
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.UInt16, concreteTypes
                 elif TypeInfo.NominallyEqual typeDef corelib.Int32 then
-                    zeroOfPrimitive PrimitiveType.Int32, concreteTypes
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.Int32, concreteTypes
                 elif TypeInfo.NominallyEqual typeDef corelib.UInt32 then
-                    zeroOfPrimitive PrimitiveType.UInt32, concreteTypes
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.UInt32, concreteTypes
                 elif TypeInfo.NominallyEqual typeDef corelib.Int64 then
-                    zeroOfPrimitive PrimitiveType.Int64, concreteTypes
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.Int64, concreteTypes
                 elif TypeInfo.NominallyEqual typeDef corelib.UInt64 then
-                    zeroOfPrimitive PrimitiveType.UInt64, concreteTypes
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.UInt64, concreteTypes
                 elif TypeInfo.NominallyEqual typeDef corelib.Single then
-                    zeroOfPrimitive PrimitiveType.Single, concreteTypes
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.Single, concreteTypes
                 elif TypeInfo.NominallyEqual typeDef corelib.Double then
-                    zeroOfPrimitive PrimitiveType.Double, concreteTypes
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.Double, concreteTypes
                 elif TypeInfo.NominallyEqual typeDef corelib.String then
-                    zeroOfPrimitive PrimitiveType.String, concreteTypes
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.String, concreteTypes
                 elif TypeInfo.NominallyEqual typeDef corelib.Object then
-                    zeroOfPrimitive PrimitiveType.Object, concreteTypes
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.Object, concreteTypes
                 elif TypeInfo.NominallyEqual typeDef corelib.IntPtr then
-                    zeroOfPrimitive PrimitiveType.IntPtr, concreteTypes
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.IntPtr, concreteTypes
                 elif TypeInfo.NominallyEqual typeDef corelib.UIntPtr then
-                    zeroOfPrimitive PrimitiveType.UIntPtr, concreteTypes
-                else if
-                    // Check if it's an array type
-                    typeDef = corelib.Array
-                then
-                    CliType.ObjectRef None, concreteTypes // Arrays are reference types
+                    zeroOfPrimitive concreteTypes corelib PrimitiveType.UIntPtr, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.Array then
+                    // Arrays are reference types
+                    CliType.ObjectRef None, concreteTypes
                 else if
+
                     // Not a known primitive, now check for cycles
                     Set.contains handle visited
                 then
                     // We're in a cycle - return a default zero value for the type
-                    // For value types in cycles, we'll return a null reference as a safe fallback
-                    // This should only happen with self-referential types
+                    // Value types can't be self-referential unless they are specifically known to the
+                    // runtime - for example, System.Byte is a value type with a single field,
+                    // of type System.Byte.
+                    // Since we check for (nominal) equality against all such types in the first branch,
+                    // this code path is only hit with reference types.
                     CliType.ObjectRef None, concreteTypes
                 else
                     let visited = Set.add handle visited
                     // Not a known primitive, check if it's a value type or reference type
                     determineZeroForCustomType concreteTypes assemblies corelib handle concreteType typeDef visited
             else if
+
                 // Not from corelib or has generics
                 concreteType.Assembly = corelib.Corelib.Name
                 && typeDef = corelib.Array
                 && concreteType.Generics.Length = 1
             then
-                // This is an array type
+                // This is an array type, so null is appropriate
                 CliType.ObjectRef None, concreteTypes
             else if
+
                 // Custom type - now check for cycles
                 Set.contains handle visited
             then
-                // We're in a cycle - return a default zero value for the type
-                // For value types in cycles, we'll return a null reference as a safe fallback
-                // This should only happen with self-referential types
+                // We're in a cycle - return a default zero value for the type.
+                // Value types can't be self-referential unless they are specifically known to the
+                // runtime - for example, System.Byte is a value type with a single field,
+                // of type System.Byte.
+                // Since we check for (nominal) equality against all such types in the first branch,
+                // this code path is only hit with reference types.
                 CliType.ObjectRef None, concreteTypes
             else
                 let visited = Set.add handle visited
@@ -430,9 +771,10 @@ module CliType =
                         Name = field.Name
                         Contents = fieldZero
                         Offset = field.Offset
+                        Type = fieldHandle
                     }
                 )
-                |> CliValueType.OfFields
+                |> CliValueType.OfFields typeDef.Layout
 
             CliType.ValueType vt, currentConcreteTypes
         else
@@ -460,20 +802,22 @@ module CliType =
         // The field type might reference generic parameters of the declaring type
         let methodGenerics = ImmutableArray.Empty // Fields don't have method generics
 
-        let loadAssembly
-            (assyName : AssemblyName)
-            (ref : AssemblyReferenceHandle)
-            : ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly
-            =
-            match assemblies.TryGetValue assyName.FullName with
-            | true, currentAssy ->
-                let targetAssyRef = currentAssy.AssemblyReferences.[ref]
+        let loadAssembly =
+            { new IAssemblyLoad with
+                member _.LoadAssembly loaded assyName ref =
+                    match loaded.TryGetValue assyName.FullName with
+                    | true, currentAssy ->
+                        let targetAssyRef = currentAssy.AssemblyReferences.[ref]
 
-                match assemblies.TryGetValue targetAssyRef.Name.FullName with
-                | true, targetAssy -> assemblies, targetAssy
-                | false, _ ->
-                    failwithf "Assembly %s not loaded when trying to resolve reference" targetAssyRef.Name.FullName
-            | false, _ -> failwithf "Current assembly %s not loaded when trying to resolve reference" assyName.FullName
+                        match loaded.TryGetValue targetAssyRef.Name.FullName with
+                        | true, targetAssy -> loaded, targetAssy
+                        | false, _ ->
+                            failwithf
+                                "Assembly %s not loaded when trying to resolve reference"
+                                targetAssyRef.Name.FullName
+                    | false, _ ->
+                        failwithf "Current assembly %s not loaded when trying to resolve reference" assyName.FullName
+            }
 
         let handle, newCtx =
             TypeConcretization.concretizeType
@@ -493,21 +837,7 @@ module CliType =
         | CliType.Char (high, low) -> failwith "todo"
         | CliType.ObjectRef managedHeapAddressOption -> failwith "todo"
         | CliType.RuntimePointer cliRuntimePointer -> failwith "todo"
-        | CliType.ValueType cvt ->
-            {
-                Fields =
-                    cvt.Fields
-                    |> List.replaceWhere (fun f ->
-                        if f.Name = field then
-                            { f with
-                                Contents = value
-                            }
-                            |> Some
-                        else
-                            None
-                    )
-            }
-            |> CliType.ValueType
+        | CliType.ValueType cvt -> CliValueType.WithFieldSet field value cvt |> CliType.ValueType
 
     let getField (field : string) (value : CliType) : CliType =
         match value with
@@ -516,6 +846,24 @@ module CliType =
         | CliType.Char (high, low) -> failwith "todo"
         | CliType.ObjectRef managedHeapAddressOption -> failwith "todo"
         | CliType.RuntimePointer cliRuntimePointer -> failwith "todo"
-        | CliType.ValueType cvt ->
-            cvt.Fields
-            |> List.pick (fun f -> if f.Name = field then Some f.Contents else None)
+        | CliType.ValueType cvt -> CliValueType.DereferenceField field cvt
+
+    /// Returns the offset and size.
+    let getFieldLayout (field : string) (value : CliType) : int * int =
+        match value with
+        | CliType.Numeric cliNumericType -> failwith "todo"
+        | CliType.Bool b -> failwith "todo"
+        | CliType.Char (high, low) -> failwith "todo"
+        | CliType.ObjectRef managedHeapAddressOption -> failwith "todo"
+        | CliType.RuntimePointer cliRuntimePointer -> failwith "todo"
+        | CliType.ValueType cvt -> CliValueType.GetFieldLayout field cvt
+
+    /// Returns None if there isn't *exactly* one field that starts there. This rules out some valid programs.
+    let getFieldAt (offset : int) (value : CliType) : CliConcreteField option =
+        match value with
+        | CliType.Numeric cliNumericType -> failwith "todo"
+        | CliType.Bool b -> failwith "todo"
+        | CliType.Char (high, low) -> failwith "todo"
+        | CliType.ObjectRef managedHeapAddressOption -> failwith "todo"
+        | CliType.RuntimePointer cliRuntimePointer -> failwith "todo"
+        | CliType.ValueType cvt -> CliValueType.FieldsAt offset cvt |> List.tryExactlyOne

WoofWare.PawPrint/BinaryArithmetic.fs

@@ -4,25 +4,133 @@ namespace WoofWare.PawPrint
 
 type IArithmeticOperation =
     abstract Int32Int32 : int32 -> int32 -> int32
+    abstract Int32NativeInt : int32 -> nativeint -> nativeint
+    abstract NativeIntInt32 : nativeint -> int32 -> nativeint
     abstract Int64Int64 : int64 -> int64 -> int64
     abstract FloatFloat : float -> float -> float
+    abstract NativeIntNativeInt : nativeint -> nativeint -> nativeint
+    abstract Int32ManagedPtr : IlMachineState -> int32 -> ManagedPointerSource -> Choice<ManagedPointerSource, int>
+    abstract ManagedPtrInt32 : IlMachineState -> ManagedPointerSource -> int32 -> Choice<ManagedPointerSource, int>
+
+    abstract ManagedPtrManagedPtr :
+        IlMachineState -> ManagedPointerSource -> ManagedPointerSource -> Choice<ManagedPointerSource, nativeint>
+
     abstract Name : string
 
 [<RequireQualifiedAccess>]
 module ArithmeticOperation =
+    let private addInt32ManagedPtr state v ptr =
+        match ptr with
+        | LocalVariable (sourceThread, methodFrame, whichVar) -> failwith "refusing to add to a local variable address"
+        | Argument (sourceThread, methodFrame, whichVar) -> failwith "refusing to add to an argument address"
+        | Heap managedHeapAddress -> failwith "refusing to add to a heap address"
+        | ArrayIndex (arr, index) -> failwith "TODO: arrays"
+        | Field (src, fieldName) ->
+            let obj = IlMachineState.dereferencePointer state src
+            let offset, _ = CliType.getFieldLayout fieldName obj
+
+            match CliType.getFieldAt (offset + v) obj with
+            | None -> failwith "TODO: couldn't identify field at offset"
+            | Some field ->
+                ManagedPointerSource.Field (src, CliConcreteField.ToCliField(field).Name)
+                |> Choice1Of2
+        | Null -> Choice2Of2 v
+        | InterpretedAsType (managedPointerSource, concreteType) -> failwith "todo"
+
+    let private mulInt32ManagedPtr (state : IlMachineState) v ptr =
+        if v = 0 then
+            Choice2Of2 0
+        elif v = 1 then
+            Choice1Of2 ptr
+        else
+
+        match ptr with
+        | ManagedPointerSource.Null -> Choice2Of2 0
+        | _ -> failwith "refusing to multiply pointers"
+
     let add =
         { new IArithmeticOperation with
             member _.Int32Int32 a b = (# "add" a b : int32 #)
             member _.Int64Int64 a b = (# "add" a b : int64 #)
             member _.FloatFloat a b = (# "add" a b : float #)
+            member _.NativeIntNativeInt a b = (# "add" a b : nativeint #)
+            member _.Int32NativeInt a b = (# "add" a b : nativeint #)
+            member _.NativeIntInt32 a b = (# "add" a b : nativeint #)
+
+            member _.ManagedPtrManagedPtr _ ptr1 ptr2 =
+                match ptr1, ptr2 with
+                | ManagedPointerSource.Null, _ -> Choice1Of2 ptr2
+                | _, ManagedPointerSource.Null -> Choice1Of2 ptr1
+                | _, _ -> failwith "refusing to add two managed pointers"
+
+            member _.Int32ManagedPtr state val1 ptr2 = addInt32ManagedPtr state val1 ptr2
+            member _.ManagedPtrInt32 state ptr1 val2 = addInt32ManagedPtr state val2 ptr1
+
             member _.Name = "add"
         }
 
+    let addOvf =
+        { new IArithmeticOperation with
+            member _.Int32Int32 a b = (# "add.ovf" a b : int32 #)
+            member _.Int64Int64 a b = (# "add.ovf" a b : int64 #)
+            member _.FloatFloat a b = (# "add.ovf" a b : float #)
+            member _.NativeIntNativeInt a b = (# "add.ovf" a b : nativeint #)
+            member _.Int32NativeInt a b = (# "add.ovf" a b : nativeint #)
+            member _.NativeIntInt32 a b = (# "add.ovf" a b : nativeint #)
+
+            member _.ManagedPtrManagedPtr _ ptr1 ptr2 =
+                match ptr1, ptr2 with
+                | ManagedPointerSource.Null, _ -> Choice1Of2 ptr2
+                | _, ManagedPointerSource.Null -> Choice1Of2 ptr1
+                | _, _ -> failwith "refusing to add two managed pointers"
+
+            member _.Int32ManagedPtr state val1 ptr2 = addInt32ManagedPtr state val1 ptr2
+            member _.ManagedPtrInt32 state ptr1 val2 = addInt32ManagedPtr state val2 ptr1
+
+            member _.Name = "add.ovf"
+        }
+
     let sub =
         { new IArithmeticOperation with
             member _.Int32Int32 a b = (# "sub" a b : int32 #)
             member _.Int64Int64 a b = (# "sub" a b : int64 #)
             member _.FloatFloat a b = (# "sub" a b : float #)
+            member _.NativeIntNativeInt a b = (# "sub" a b : nativeint #)
+            member _.Int32NativeInt a b = (# "sub" a b : nativeint #)
+            member _.NativeIntInt32 a b = (# "sub" a b : nativeint #)
+
+            member _.ManagedPtrManagedPtr state ptr1 ptr2 =
+                match ptr1, ptr2 with
+                | ptr1, ManagedPointerSource.Null -> Choice1Of2 ptr1
+                | ManagedPointerSource.Null, _ -> failwith "refusing to create negative pointer"
+                | ManagedPointerSource.ArrayIndex (arr1, index1), ManagedPointerSource.ArrayIndex (arr2, index2) ->
+                    if arr1 <> arr2 then
+                        failwith "refusing to operate on pointers to different arrays"
+
+                    (index1 - index2) |> nativeint |> Choice2Of2
+                | ManagedPointerSource.ArrayIndex _, _ -> failwith $"refusing to operate on array index ptr vs %O{ptr2}"
+                | ManagedPointerSource.Argument _, _
+                | _, ManagedPointerSource.Argument _ ->
+                    failwith $"refusing to operate on pointers to arguments: %O{ptr1} and %O{ptr2}"
+                | ManagedPointerSource.Field (obj1, fieldName1), ManagedPointerSource.Field (obj2, fieldName2) ->
+                    if obj1 <> obj2 then
+                        failwith "refusing to operate on field pointers in different objects"
+
+                    let obj = IlMachineState.dereferencePointer state obj1
+
+                    let offset1, _ = CliType.getFieldLayout fieldName1 obj
+                    let offset2, _ = CliType.getFieldLayout fieldName2 obj
+
+                    (offset1 - offset2) |> nativeint |> Choice2Of2
+                | _, _ -> failwith "TODO"
+
+            member _.Int32ManagedPtr state val1 ptr2 =
+                match ptr2 with
+                | ManagedPointerSource.Null -> Choice2Of2 val1
+                | _ -> failwith "refusing to subtract a pointer"
+
+            member _.ManagedPtrInt32 state ptr1 val2 = failwith "TODO: subtract from pointer"
+
             member _.Name = "sub"
         }
 
@@ -31,21 +139,143 @@ module ArithmeticOperation =
             member _.Int32Int32 a b = (# "mul" a b : int32 #)
             member _.Int64Int64 a b = (# "mul" a b : int64 #)
             member _.FloatFloat a b = (# "mul" a b : float #)
+            member _.NativeIntNativeInt a b = (# "mul" a b : nativeint #)
+            member _.Int32NativeInt a b = (# "mul" a b : nativeint #)
+            member _.NativeIntInt32 a b = (# "mul" a b : nativeint #)
+
+            member _.ManagedPtrManagedPtr _ ptr1 ptr2 =
+                match ptr1, ptr2 with
+                | ManagedPointerSource.Null, _ -> Choice2Of2 (nativeint 0)
+                | _, ManagedPointerSource.Null -> Choice2Of2 (nativeint 0)
+                | _, _ -> failwith "refusing to multiply two managed pointers"
+
+            member _.Int32ManagedPtr state a ptr = mulInt32ManagedPtr state a ptr
+            member _.ManagedPtrInt32 state ptr a = mulInt32ManagedPtr state a ptr
+
             member _.Name = "mul"
         }
 
+    let rem =
+        { new IArithmeticOperation with
+            member _.Int32Int32 a b = (# "rem" a b : int32 #)
+            member _.Int64Int64 a b = (# "rem" a b : int64 #)
+            member _.FloatFloat a b = (# "rem" a b : float #)
+            member _.NativeIntNativeInt a b = (# "rem" a b : nativeint #)
+            member _.Int32NativeInt a b = (# "rem" a b : nativeint #)
+            member _.NativeIntInt32 a b = (# "rem" a b : nativeint #)
+
+            member _.ManagedPtrManagedPtr _ ptr1 ptr2 = failwith "refusing to rem pointers"
+
+            member _.Int32ManagedPtr _ a ptr = failwith "refusing to rem pointer"
+
+            member _.ManagedPtrInt32 _ ptr a = failwith "refusing to rem pointer"
+
+            member _.Name = "mul"
+        }
+
+    let mulOvf =
+        { new IArithmeticOperation with
+            member _.Int32Int32 a b = (# "mul.ovf" a b : int32 #)
+            member _.Int64Int64 a b = (# "mul.ovf" a b : int64 #)
+            member _.FloatFloat a b = (# "mul.ovf" a b : float #)
+            member _.NativeIntNativeInt a b = (# "mul.ovf" a b : nativeint #)
+            member _.Int32NativeInt a b = (# "mul.ovf" a b : nativeint #)
+            member _.NativeIntInt32 a b = (# "mul.ovf" a b : nativeint #)
+
+            member _.ManagedPtrManagedPtr _ ptr1 ptr2 =
+                match ptr1, ptr2 with
+                | ManagedPointerSource.Null, _ -> Choice2Of2 (nativeint 0)
+                | _, ManagedPointerSource.Null -> Choice2Of2 (nativeint 0)
+                | _, _ -> failwith "refusing to multiply two managed pointers"
+
+            member _.Int32ManagedPtr state a ptr = mulInt32ManagedPtr state a ptr
+            member _.ManagedPtrInt32 state a ptr = mulInt32ManagedPtr state ptr a
+
+            member _.Name = "mul_ovf"
+        }
+
+    let div =
+        { new IArithmeticOperation with
+            member _.Int32Int32 a b = (# "div" a b : int32 #)
+            member _.Int64Int64 a b = (# "div" a b : int64 #)
+            member _.FloatFloat a b = (# "div" a b : float #)
+            member _.NativeIntNativeInt a b = (# "div" a b : nativeint #)
+            member _.Int32NativeInt a b = (# "div" a b : nativeint #)
+            member _.NativeIntInt32 a b = (# "div" a b : nativeint #)
+
+            member _.ManagedPtrManagedPtr _ ptr1 ptr2 =
+                match ptr1, ptr2 with
+                | ManagedPointerSource.Null, _ -> Choice2Of2 (nativeint 0)
+                | _, _ -> failwith "refusing to divide two managed pointers"
+
+            member _.Int32ManagedPtr _ a ptr =
+                if a = 0 then
+                    Choice2Of2 0
+                else
+                    failwith "refusing to divide pointers"
+
+            member _.ManagedPtrInt32 _ ptr a =
+                if a = 1 then
+                    Choice1Of2 ptr
+                else
+                    failwith "refusing to divide a pointer"
+
+            member _.Name = "div"
+        }
+
 [<RequireQualifiedAccess>]
 module BinaryArithmetic =
-    let execute (op : IArithmeticOperation) (val1 : EvalStackValue) (val2 : EvalStackValue) : EvalStackValue =
+    let execute
+        (op : IArithmeticOperation)
+        (state : IlMachineState)
+        (val1 : EvalStackValue)
+        (val2 : EvalStackValue)
+        : EvalStackValue
+        =
         // see table at https://learn.microsoft.com/en-us/dotnet/api/system.reflection.emit.opcodes.add?view=net-9.0
         match val1, val2 with
         | EvalStackValue.Int32 val1, EvalStackValue.Int32 val2 -> op.Int32Int32 val1 val2 |> EvalStackValue.Int32
-        | EvalStackValue.Int32 val1, EvalStackValue.NativeInt val2 -> failwith "" |> EvalStackValue.NativeInt
-        | EvalStackValue.Int32 val1, EvalStackValue.ManagedPointer val2 -> failwith "" |> EvalStackValue.ManagedPointer
+        | EvalStackValue.Int32 val1, EvalStackValue.NativeInt val2 ->
+            let val2 =
+                match val2 with
+                | NativeIntSource.Verbatim n -> nativeint<int64> n
+                | v -> failwith $"refusing to operate on non-verbatim native int %O{v}"
+
+            op.Int32NativeInt val1 val2
+            |> int64<nativeint>
+            |> NativeIntSource.Verbatim
+            |> EvalStackValue.NativeInt
+        | EvalStackValue.Int32 val1, EvalStackValue.ManagedPointer val2 ->
+            match op.Int32ManagedPtr state val1 val2 with
+            | Choice1Of2 v -> EvalStackValue.ManagedPointer v
+            | Choice2Of2 i -> EvalStackValue.Int32 i
         | EvalStackValue.Int32 val1, EvalStackValue.ObjectRef val2 -> failwith "" |> EvalStackValue.ObjectRef
         | EvalStackValue.Int64 val1, EvalStackValue.Int64 val2 -> op.Int64Int64 val1 val2 |> EvalStackValue.Int64
-        | EvalStackValue.NativeInt val1, EvalStackValue.Int32 val2 -> failwith "" |> EvalStackValue.NativeInt
-        | EvalStackValue.NativeInt val1, EvalStackValue.NativeInt val2 -> failwith "" |> EvalStackValue.NativeInt
+        | EvalStackValue.NativeInt val1, EvalStackValue.Int32 val2 ->
+            let val1 =
+                match val1 with
+                | NativeIntSource.Verbatim n -> nativeint<int64> n
+                | v -> failwith $"refusing to operate on non-verbatim native int %O{v}"
+
+            op.NativeIntInt32 val1 val2
+            |> int64<nativeint>
+            |> NativeIntSource.Verbatim
+            |> EvalStackValue.NativeInt
+        | EvalStackValue.NativeInt val1, EvalStackValue.NativeInt val2 ->
+            let val1 =
+                match val1 with
+                | NativeIntSource.Verbatim n -> nativeint<int64> n
+                | v -> failwith $"refusing to operate on non-verbatim native int %O{v}"
+
+            let val2 =
+                match val2 with
+                | NativeIntSource.Verbatim n -> nativeint<int64> n
+                | v -> failwith $"refusing to operate on non-verbatim native int %O{v}"
+
+            op.NativeIntNativeInt val1 val2
+            |> int64<nativeint>
+            |> NativeIntSource.Verbatim
+            |> EvalStackValue.NativeInt
         | EvalStackValue.NativeInt val1, EvalStackValue.ManagedPointer val2 ->
             failwith "" |> EvalStackValue.ManagedPointer
         | EvalStackValue.NativeInt val1, EvalStackValue.ObjectRef val2 -> failwith "" |> EvalStackValue.ObjectRef
@@ -53,6 +283,13 @@ module BinaryArithmetic =
         | EvalStackValue.ManagedPointer val1, EvalStackValue.NativeInt val2 ->
             failwith "" |> EvalStackValue.ManagedPointer
         | EvalStackValue.ObjectRef val1, EvalStackValue.NativeInt val2 -> failwith "" |> EvalStackValue.ObjectRef
-        | EvalStackValue.ManagedPointer val1, EvalStackValue.Int32 val2 -> failwith "" |> EvalStackValue.ManagedPointer
+        | EvalStackValue.ManagedPointer val1, EvalStackValue.Int32 val2 ->
+            match op.ManagedPtrInt32 state val1 val2 with
+            | Choice1Of2 result -> EvalStackValue.ManagedPointer result
+            | Choice2Of2 result -> EvalStackValue.NativeInt (NativeIntSource.Verbatim (int64<int32> result))
         | EvalStackValue.ObjectRef val1, EvalStackValue.Int32 val2 -> failwith "" |> EvalStackValue.ObjectRef
+        | EvalStackValue.ManagedPointer val1, EvalStackValue.ManagedPointer val2 ->
+            match op.ManagedPtrManagedPtr state val1 val2 with
+            | Choice1Of2 result -> EvalStackValue.ManagedPointer result
+            | Choice2Of2 result -> EvalStackValue.NativeInt (NativeIntSource.Verbatim (int64<nativeint> result))
         | val1, val2 -> failwith $"invalid %s{op.Name} operation: {val1} and {val2}"

WoofWare.PawPrint/Corelib.fs

@@ -1,5 +1,8 @@
 namespace WoofWare.PawPrint
 
+open System.Collections.Immutable
+open System.Reflection.Metadata
+
 [<RequireQualifiedAccess>]
 module Corelib =
 
@@ -149,6 +152,66 @@ module Corelib =
             )
             |> Seq.exactlyOne
 
+        let exceptionType =
+            corelib.TypeDefs
+            |> Seq.choose (fun (KeyValue (_, v)) -> if v.Name = "Exception" then Some v else None)
+            |> Seq.exactlyOne
+
+        let arithmeticException =
+            corelib.TypeDefs
+            |> Seq.choose (fun (KeyValue (_, v)) -> if v.Name = "ArithmeticException" then Some v else None)
+            |> Seq.exactlyOne
+
+        let divideByZeroException =
+            corelib.TypeDefs
+            |> Seq.choose (fun (KeyValue (_, v)) -> if v.Name = "DivideByZeroException" then Some v else None)
+            |> Seq.exactlyOne
+
+        let overflowException =
+            corelib.TypeDefs
+            |> Seq.choose (fun (KeyValue (_, v)) -> if v.Name = "OverflowException" then Some v else None)
+            |> Seq.exactlyOne
+
+        let stackOverflowException =
+            corelib.TypeDefs
+            |> Seq.choose (fun (KeyValue (_, v)) -> if v.Name = "StackOverflowException" then Some v else None)
+            |> Seq.exactlyOne
+
+        let typeLoadException =
+            corelib.TypeDefs
+            |> Seq.choose (fun (KeyValue (_, v)) -> if v.Name = "TypeLoadException" then Some v else None)
+            |> Seq.exactlyOne
+
+        let indexOutOfRangeException =
+            corelib.TypeDefs
+            |> Seq.choose (fun (KeyValue (_, v)) -> if v.Name = "IndexOutOfRangeException" then Some v else None)
+            |> Seq.exactlyOne
+
+        let invalidCastException =
+            corelib.TypeDefs
+            |> Seq.choose (fun (KeyValue (_, v)) -> if v.Name = "InvalidCastException" then Some v else None)
+            |> Seq.exactlyOne
+
+        let missingFieldException =
+            corelib.TypeDefs
+            |> Seq.choose (fun (KeyValue (_, v)) -> if v.Name = "MissingFieldException" then Some v else None)
+            |> Seq.exactlyOne
+
+        let missingMethodException =
+            corelib.TypeDefs
+            |> Seq.choose (fun (KeyValue (_, v)) -> if v.Name = "MissingMethodException" then Some v else None)
+            |> Seq.exactlyOne
+
+        let nullReferenceException =
+            corelib.TypeDefs
+            |> Seq.choose (fun (KeyValue (_, v)) -> if v.Name = "NullReferenceException" then Some v else None)
+            |> Seq.exactlyOne
+
+        let outOfMemoryException =
+            corelib.TypeDefs
+            |> Seq.choose (fun (KeyValue (_, v)) -> if v.Name = "OutOfMemoryException" then Some v else None)
+            |> Seq.exactlyOne
+
         {
             Corelib = corelib
             String = stringType
@@ -179,4 +242,94 @@ module Corelib =
             TypedReference = typedReferenceType
             IntPtr = intPtrType
             UIntPtr = uintPtrType
+            Exception = exceptionType
+            ArithmeticException = arithmeticException
+            DivideByZeroException = divideByZeroException
+            OverflowException = overflowException
+            StackOverflowException = stackOverflowException
+            TypeLoadException = typeLoadException
+            IndexOutOfRangeException = indexOutOfRangeException
+            InvalidCastException = invalidCastException
+            MissingFieldException = missingFieldException
+            MissingMethodException = missingMethodException
+            NullReferenceException = nullReferenceException
+            OutOfMemoryException = outOfMemoryException
         }
+
+    let concretizeAll
+        (loaded : ImmutableDictionary<string, DumpedAssembly>)
+        (bct : BaseClassTypes<DumpedAssembly>)
+        (t : AllConcreteTypes)
+        : AllConcreteTypes
+        =
+        let ctx =
+            {
+                TypeConcretization.ConcretizationContext.InProgress = ImmutableDictionary.Empty
+                TypeConcretization.ConcretizationContext.ConcreteTypes = t
+                TypeConcretization.ConcretizationContext.LoadedAssemblies = loaded
+                TypeConcretization.ConcretizationContext.BaseTypes = bct
+            }
+
+        let loader =
+            { new IAssemblyLoad with
+                member _.LoadAssembly _ _ _ =
+                    failwith "should have already loaded this assembly"
+            }
+
+        let tys =
+            [
+                bct.String
+                bct.Boolean
+                bct.Char
+                bct.SByte
+                bct.Byte
+                bct.Int16
+                bct.UInt16
+                bct.Int32
+                bct.UInt32
+                bct.Int64
+                bct.UInt64
+                bct.Single
+                bct.Double
+                bct.Array
+                bct.Enum
+                bct.ValueType
+                bct.DelegateType
+                bct.Object
+                bct.RuntimeTypeHandle
+                bct.RuntimeMethodHandle
+                bct.RuntimeFieldHandle
+                bct.RuntimeFieldInfoStub
+                bct.RuntimeFieldHandleInternal
+                bct.RuntimeType
+                bct.Void
+                bct.TypedReference
+                bct.IntPtr
+                bct.UIntPtr
+            ]
+
+        (ctx, tys)
+        ||> List.fold (fun ctx ty ->
+            let stk =
+                match DumpedAssembly.resolveBaseType ctx.BaseTypes ctx.LoadedAssemblies ty.Assembly ty.BaseType with
+                | ResolvedBaseType.Enum
+                | ResolvedBaseType.ValueType -> SignatureTypeKind.ValueType
+                | ResolvedBaseType.Object
+                | ResolvedBaseType.Delegate -> SignatureTypeKind.Class
+
+            let _handle, ctx =
+                TypeConcretization.concretizeType
+                    ctx
+                    loader
+                    ty.Assembly
+                    ImmutableArray.Empty
+                    ImmutableArray.Empty
+                    (TypeDefn.FromDefinition (
+                        ComparableTypeDefinitionHandle.Make ty.TypeDefHandle,
+                        ty.Assembly.FullName,
+                        stk
+                    ))
+
+            ctx
+        )
+        |> _.ConcreteTypes

WoofWare.PawPrint/EvalStack.fs

@@ -1,5 +1,7 @@
 namespace WoofWare.PawPrint
 
+#nowarn "42"
+
 /// See I.12.3.2.1 for definition
 type EvalStackValue =
     | Int32 of int32
@@ -8,9 +10,8 @@ type EvalStackValue =
     | Float of float
     | ManagedPointer of ManagedPointerSource
     | ObjectRef of ManagedHeapAddress
-    // Fraser thinks this isn't really a thing in CoreCLR
-    // | TransientPointer of TransientPointerSource
-    | UserDefinedValueType of EvalStackValueUserType
+    /// This doesn't match what the CLR does in reality, but we can work out whatever we need from it.
+    | UserDefinedValueType of CliValueType
 
     override this.ToString () =
         match this with
@@ -20,40 +21,7 @@ type EvalStackValue =
         | EvalStackValue.Float f -> $"Float(%f{f})"
         | EvalStackValue.ManagedPointer managedPointerSource -> $"Pointer(%O{managedPointerSource})"
         | EvalStackValue.ObjectRef managedHeapAddress -> $"ObjectRef(%O{managedHeapAddress})"
-        | EvalStackValue.UserDefinedValueType evalStackValues ->
-            let desc =
-                evalStackValues.Fields
-                |> List.map (_.ContentsEval >> string<EvalStackValue>)
-                |> String.concat " | "
-
-            $"Struct(%s{desc})"
-
-and EvalStackValueField =
-    {
-        Name : string
-        ContentsEval : EvalStackValue
-        Offset : int option
-    }
-
-and EvalStackValueUserType =
-    {
-        Fields : EvalStackValueField list
-    }
-
-    static member DereferenceField (name : string) (this : EvalStackValueUserType) =
-        // TODO: this doesn't account for overlapping fields
-        this.Fields
-        |> List.pick (fun stackField ->
-            if stackField.Name = name then
-                Some stackField.ContentsEval
-            else
-                None
-        )
-
-    static member OfFields (fields : EvalStackValueField list) =
-        {
-            Fields = fields
-        }
+        | EvalStackValue.UserDefinedValueType evalStackValues -> $"Struct(%O{evalStackValues})"
 
 [<RequireQualifiedAccess>]
 module EvalStackValue =
@@ -81,6 +49,7 @@ module EvalStackValue =
                     failwith "todo"
             | NativeIntSource.ManagedPointer _ -> failwith "TODO"
             | NativeIntSource.FunctionPointer _ -> failwith "TODO"
+            | NativeIntSource.FieldHandlePtr _ -> failwith "TODO"
             | NativeIntSource.TypeHandlePtr _ -> failwith "TODO"
         | EvalStackValue.Float f -> failwith "todo"
         | EvalStackValue.ManagedPointer managedPointerSource ->
@@ -109,7 +78,14 @@ module EvalStackValue =
         match value with
         | EvalStackValue.Int32 i -> Some (int64<int> i)
         | EvalStackValue.Int64 i -> Some i
-        | EvalStackValue.NativeInt nativeIntSource -> failwith "todo"
+        | EvalStackValue.NativeInt src ->
+            match src with
+            | NativeIntSource.Verbatim int64 -> Some int64
+            | NativeIntSource.ManagedPointer ManagedPointerSource.Null -> Some 0L
+            | NativeIntSource.ManagedPointer _
+            | NativeIntSource.FunctionPointer _
+            | NativeIntSource.TypeHandlePtr _
+            | NativeIntSource.FieldHandlePtr _ -> failwith "refusing to convert pointer to int64"
         | EvalStackValue.Float f -> failwith "todo"
         | EvalStackValue.ManagedPointer managedPointerSource -> failwith "todo"
         | EvalStackValue.ObjectRef managedHeapAddress -> failwith "todo"
@@ -126,6 +102,52 @@ module EvalStackValue =
         | EvalStackValue.ObjectRef managedHeapAddress -> failwith "todo"
         | EvalStackValue.UserDefinedValueType evalStackValues -> failwith "todo"
 
+    /// Then truncates to int32.
+    let convToUInt8 (value : EvalStackValue) : int32 option =
+        match value with
+        | EvalStackValue.Int32 (i : int32) ->
+            let v = (# "conv.u1" i : uint8 #)
+            Some (int32<uint8> v)
+        | EvalStackValue.Int64 int64 ->
+            let v = (# "conv.u1" int64 : uint8 #)
+            Some (int32<uint8> v)
+        | EvalStackValue.NativeInt nativeIntSource -> failwith "todo"
+        | EvalStackValue.Float f -> failwith "todo"
+        | EvalStackValue.ManagedPointer managedPointerSource -> failwith "todo"
+        | EvalStackValue.ObjectRef managedHeapAddress -> failwith "todo"
+        | EvalStackValue.UserDefinedValueType evalStackValues -> failwith "todo"
+
+    let rec ofCliType (v : CliType) : EvalStackValue =
+        match v with
+        | CliType.Numeric numeric ->
+            match numeric with
+            | CliNumericType.Int32 i -> EvalStackValue.Int32 i
+            | CliNumericType.Int64 i -> EvalStackValue.Int64 i
+            | CliNumericType.NativeInt i -> EvalStackValue.NativeInt i
+            // Sign-extend types int8 and int16
+            // Zero-extend unsigned int8/unsigned int16
+            | CliNumericType.Int8 b -> int32<int8> b |> EvalStackValue.Int32
+            | CliNumericType.UInt8 b -> int32<uint8> b |> EvalStackValue.Int32
+            | CliNumericType.Int16 s -> int32<int16> s |> EvalStackValue.Int32
+            | CliNumericType.UInt16 s -> int32<uint16> s |> EvalStackValue.Int32
+            | CliNumericType.Float32 f -> EvalStackValue.Float (float<float32> f)
+            | CliNumericType.Float64 f -> EvalStackValue.Float f
+            | CliNumericType.NativeFloat f -> EvalStackValue.Float f
+        | CliType.ObjectRef i ->
+            match i with
+            | None -> EvalStackValue.ManagedPointer ManagedPointerSource.Null
+            | Some i -> EvalStackValue.ManagedPointer (ManagedPointerSource.Heap i)
+        // Zero-extend bool/char
+        | CliType.Bool b -> int32 b |> EvalStackValue.Int32
+        | CliType.Char (high, low) -> int32 high * 256 + int32 low |> EvalStackValue.Int32
+        | CliType.RuntimePointer ptr ->
+            match ptr with
+            | CliRuntimePointer.Verbatim ptrInt -> NativeIntSource.Verbatim ptrInt |> EvalStackValue.NativeInt
+            | CliRuntimePointer.FieldRegistryHandle ptrInt ->
+                NativeIntSource.FieldHandlePtr ptrInt |> EvalStackValue.NativeInt
+            | CliRuntimePointer.Managed ptr -> ptr |> EvalStackValue.ManagedPointer
+        | CliType.ValueType fields -> EvalStackValue.UserDefinedValueType fields
+
     let rec toCliTypeCoerced (target : CliType) (popped : EvalStackValue) : CliType =
         match target with
         | CliType.Numeric numeric ->
@@ -134,10 +156,12 @@ module EvalStackValue =
                 match popped with
                 | EvalStackValue.Int32 i -> CliType.Numeric (CliNumericType.Int32 i)
                 | EvalStackValue.UserDefinedValueType popped ->
-                    match popped.Fields with
-                    | [] -> failwith "unexpectedly empty"
-                    | [ popped ] -> toCliTypeCoerced target popped.ContentsEval
-                    | _ -> failwith $"TODO: %O{target}"
+                    let popped = CliValueType.DereferenceFieldAt 0 4 popped
+                    // TODO: when we have a general mechanism to coerce CliTypes to each other,
+                    // do that
+                    match popped with
+                    | CliType.Numeric (CliNumericType.Int32 i) -> CliType.Numeric (CliNumericType.Int32 i)
+                    | _ -> failwith "TODO"
                 | i -> failwith $"TODO: %O{i}"
             | CliNumericType.Int64 _ ->
                 match popped with
@@ -147,7 +171,7 @@ module EvalStackValue =
                     | NativeIntSource.Verbatim i -> CliType.Numeric (CliNumericType.Int64 i)
                     | NativeIntSource.ManagedPointer ptr -> failwith "TODO"
                     | NativeIntSource.FunctionPointer f -> failwith $"TODO: {f}"
-                    // CliType.Numeric (CliNumericType.ProvenanceTrackedNativeInt64 f)
+                    | NativeIntSource.FieldHandlePtr f -> failwith $"TODO: {f}"
                     | NativeIntSource.TypeHandlePtr f -> failwith $"TODO: {f}"
                 // CliType.Numeric (CliNumericType.TypeHandlePtr f)
                 | i -> failwith $"TODO: %O{i}"
@@ -158,9 +182,21 @@ module EvalStackValue =
                     CliNumericType.NativeInt (NativeIntSource.ManagedPointer ptrSrc)
                     |> CliType.Numeric
                 | EvalStackValue.UserDefinedValueType vt ->
-                    match vt.Fields with
-                    | [] -> failwith "unexpected"
-                    | [ vt ] -> toCliTypeCoerced target vt.ContentsEval
+                    let popped = CliValueType.DereferenceFieldAt 0 NATIVE_INT_SIZE vt
+                    // TODO: when we have a general mechanism to coerce CliTypes to each other,
+                    // do that
+                    match popped with
+                    | CliType.Numeric (CliNumericType.NativeInt i) -> CliType.Numeric (CliNumericType.NativeInt i)
+                    | CliType.Numeric (CliNumericType.Int64 i) ->
+                        CliType.Numeric (CliNumericType.NativeInt (NativeIntSource.Verbatim i))
+                    | CliType.RuntimePointer ptr ->
+                        match ptr with
+                        | CliRuntimePointer.Verbatim i ->
+                            CliType.Numeric (CliNumericType.NativeInt (NativeIntSource.Verbatim i))
+                        | CliRuntimePointer.FieldRegistryHandle ptr ->
+                            CliType.Numeric (CliNumericType.NativeInt (NativeIntSource.FieldHandlePtr ptr))
+                        | CliRuntimePointer.Managed src ->
+                            CliType.Numeric (CliNumericType.NativeInt (NativeIntSource.ManagedPointer src))
                     | _ -> failwith $"TODO: {popped}"
                 | _ -> failwith $"TODO: {popped}"
             | CliNumericType.NativeFloat f -> failwith "todo"
@@ -191,11 +227,9 @@ module EvalStackValue =
         | CliType.ObjectRef _ ->
             match popped with
             | EvalStackValue.ManagedPointer ptrSource ->
-                CliRuntimePointerSource.ofManagedPointerSource ptrSource
-                |> CliRuntimePointer.Managed
-                |> CliType.RuntimePointer
+                ptrSource |> CliRuntimePointer.Managed |> CliType.RuntimePointer
             | EvalStackValue.ObjectRef ptr ->
-                CliRuntimePointerSource.Heap ptr
+                ManagedPointerSource.Heap ptr
                 |> CliRuntimePointer.Managed
                 |> CliType.RuntimePointer
             | EvalStackValue.NativeInt nativeIntSource ->
@@ -204,15 +238,18 @@ module EvalStackValue =
                 | NativeIntSource.Verbatim i -> failwith $"refusing to interpret verbatim native int {i} as a pointer"
                 | NativeIntSource.FunctionPointer _ -> failwith "TODO"
                 | NativeIntSource.TypeHandlePtr _ -> failwith "refusing to interpret type handle ID as an object ref"
+                | NativeIntSource.FieldHandlePtr _ -> failwith "refusing to interpret field handle ID as an object ref"
                 | NativeIntSource.ManagedPointer ptr ->
                     match ptr with
                     | ManagedPointerSource.Null -> CliType.ObjectRef None
                     | ManagedPointerSource.Heap s -> CliType.ObjectRef (Some s)
                     | _ -> failwith "TODO"
             | EvalStackValue.UserDefinedValueType obj ->
-                match obj.Fields with
-                | [ esv ] -> toCliTypeCoerced target esv.ContentsEval
-                | fields -> failwith $"TODO: don't know how to coerce struct of {fields} to a pointer"
+                let popped = CliValueType.DereferenceFieldAt 0 NATIVE_INT_SIZE obj
+
+                match popped with
+                | CliType.ObjectRef r -> CliType.ObjectRef r
+                | _ -> failwith "TODO"
             | _ -> failwith $"TODO: {popped}"
         | CliType.Bool _ ->
             match popped with
@@ -224,22 +261,17 @@ module EvalStackValue =
             | i -> failwith $"TODO: %O{i}"
         | CliType.RuntimePointer _ ->
             match popped with
-            | EvalStackValue.ManagedPointer src ->
-                CliRuntimePointerSource.ofManagedPointerSource src
-                |> CliRuntimePointer.Managed
-                |> CliType.RuntimePointer
+            | EvalStackValue.ManagedPointer src -> src |> CliRuntimePointer.Managed |> CliType.RuntimePointer
             | EvalStackValue.NativeInt intSrc ->
                 match intSrc with
-                | NativeIntSource.Verbatim i -> CliType.RuntimePointer (CliRuntimePointer.Unmanaged i)
-                | NativeIntSource.ManagedPointer src ->
-                    CliRuntimePointerSource.ofManagedPointerSource src
-                    |> CliRuntimePointer.Managed
-                    |> CliType.RuntimePointer
+                | NativeIntSource.Verbatim i -> CliType.RuntimePointer (CliRuntimePointer.Verbatim i)
+                | NativeIntSource.ManagedPointer src -> src |> CliRuntimePointer.Managed |> CliType.RuntimePointer
                 | NativeIntSource.FunctionPointer methodInfo ->
                     CliType.Numeric (CliNumericType.NativeInt (NativeIntSource.FunctionPointer methodInfo))
                 | NativeIntSource.TypeHandlePtr int64 -> failwith "todo"
+                | NativeIntSource.FieldHandlePtr int64 -> failwith "todo"
             | EvalStackValue.ObjectRef addr ->
-                CliRuntimePointerSource.Heap addr
+                ManagedPointerSource.Heap addr
                 |> CliRuntimePointer.Managed
                 |> CliType.RuntimePointer
             | _ -> failwith $"TODO: %O{popped}"
@@ -252,91 +284,38 @@ module EvalStackValue =
             | popped -> failwith $"Unexpectedly wanted a char from {popped}"
         | CliType.ValueType vt ->
             match popped with
-            | EvalStackValue.UserDefinedValueType popped ->
-                if vt.Fields.Length <> popped.Fields.Length then
-                    // TODO: overlapping fields
-                    failwith
-                        $"mismatch: popped value type {popped} (length %i{popped.Fields.Length}) into {vt} (length %i{vt.Fields.Length})"
+            | EvalStackValue.UserDefinedValueType popped' ->
+                match CliValueType.TrySequentialFields vt, CliValueType.TrySequentialFields popped' with
+                | Some vt, Some popped ->
+                    if vt.Length <> popped.Length then
+                        failwith
+                            $"mismatch: popped value type {popped} (length %i{popped.Length}) into {vt} (length %i{vt.Length})"
 
-                (vt.Fields, popped.Fields)
-                ||> List.map2 (fun field1 popped ->
-                    if field1.Name <> popped.Name then
-                        failwith $"TODO: name mismatch, {field1.Name} vs {popped.Name}"
+                    (vt, popped)
+                    ||> List.map2 (fun field1 popped ->
+                        if field1.Name <> popped.Name then
+                            failwith $"TODO: name mismatch, {field1.Name} vs {popped.Name}"
 
-                    if field1.Offset <> popped.Offset then
-                        failwith $"TODO: offset mismatch for {field1.Name}, {field1.Offset} vs {popped.Offset}"
+                        if field1.Offset <> popped.Offset then
+                            failwith $"TODO: offset mismatch for {field1.Name}, {field1.Offset} vs {popped.Offset}"
 
-                    let contents = toCliTypeCoerced field1.Contents popped.ContentsEval
+                        let contents = toCliTypeCoerced field1.Contents (ofCliType popped.Contents)
 
-                    {
-                        CliField.Name = field1.Name
-                        Contents = contents
-                        Offset = field1.Offset
-                    }
-                )
-                |> CliValueType.OfFields
-                |> CliType.ValueType
+                        {
+                            CliField.Name = field1.Name
+                            Contents = contents
+                            Offset = field1.Offset
+                            Type = field1.Type
+                        }
+                    )
+                    |> CliValueType.OfFields popped'.Layout
+                    |> CliType.ValueType
+                | _, _ -> failwith "TODO: overlapping fields going onto eval stack"
             | popped ->
-                match vt.Fields with
-                | [ field ] -> toCliTypeCoerced field.Contents popped
+                match CliValueType.TryExactlyOneField vt with
+                | Some field -> toCliTypeCoerced field.Contents popped
                 | _ -> failwith $"TODO: {popped} into value type {target}"
 
-    let rec ofCliType (v : CliType) : EvalStackValue =
-        match v with
-        | CliType.Numeric numeric ->
-            match numeric with
-            | CliNumericType.Int32 i -> EvalStackValue.Int32 i
-            | CliNumericType.Int64 i -> EvalStackValue.Int64 i
-            | CliNumericType.NativeInt i -> EvalStackValue.NativeInt i
-            // Sign-extend types int8 and int16
-            // Zero-extend unsigned int8/unsigned int16
-            | CliNumericType.Int8 b -> int32<int8> b |> EvalStackValue.Int32
-            | CliNumericType.UInt8 b -> int32<uint8> b |> EvalStackValue.Int32
-            | CliNumericType.Int16 s -> int32<int16> s |> EvalStackValue.Int32
-            | CliNumericType.UInt16 s -> int32<uint16> s |> EvalStackValue.Int32
-            | CliNumericType.Float32 f -> EvalStackValue.Float (float<float32> f)
-            | CliNumericType.Float64 f -> EvalStackValue.Float f
-            | CliNumericType.NativeFloat f -> EvalStackValue.Float f
-        | CliType.ObjectRef i ->
-            match i with
-            | None -> EvalStackValue.ManagedPointer ManagedPointerSource.Null
-            | Some i -> EvalStackValue.ManagedPointer (ManagedPointerSource.Heap i)
-        // Zero-extend bool/char
-        | CliType.Bool b -> int32 b |> EvalStackValue.Int32
-        | CliType.Char (high, low) -> int32 high * 256 + int32 low |> EvalStackValue.Int32
-        | CliType.RuntimePointer ptr ->
-            match ptr with
-            | CliRuntimePointer.Unmanaged ptrInt -> NativeIntSource.Verbatim ptrInt |> EvalStackValue.NativeInt
-            | CliRuntimePointer.Managed ptr ->
-                match ptr with
-                | CliRuntimePointerSource.LocalVariable (sourceThread, methodFrame, var) ->
-                    ManagedPointerSource.LocalVariable (sourceThread, methodFrame, var)
-                    |> EvalStackValue.ManagedPointer
-                | CliRuntimePointerSource.ArrayIndex (arr, ind) ->
-                    ManagedPointerSource.ArrayIndex (arr, ind) |> EvalStackValue.ManagedPointer
-                | CliRuntimePointerSource.Argument (sourceThread, methodFrame, var) ->
-                    ManagedPointerSource.Argument (sourceThread, methodFrame, var)
-                    |> EvalStackValue.ManagedPointer
-                | CliRuntimePointerSource.Heap addr -> EvalStackValue.ObjectRef addr
-                | CliRuntimePointerSource.Null -> EvalStackValue.ManagedPointer ManagedPointerSource.Null
-                | CliRuntimePointerSource.Field (source, fieldName) ->
-                    ManagedPointerSource.Field (CliRuntimePointerSource.toManagedPointerSource source, fieldName)
-                    |> EvalStackValue.ManagedPointer
-        | CliType.ValueType fields ->
-            // TODO: this is a bit dubious; we're being a bit sloppy with possibly-overlapping fields here
-            fields.Fields
-            |> List.map (fun field ->
-                let contents = ofCliType field.Contents
-
-                {
-                    Name = field.Name
-                    Offset = field.Offset
-                    ContentsEval = contents
-                }
-            )
-            |> EvalStackValueUserType.OfFields
-            |> EvalStackValue.UserDefinedValueType
-
 type EvalStack =
     {
         Values : EvalStackValue list

WoofWare.PawPrint/EvalStackValueComparisons.fs

@@ -123,24 +123,14 @@ module EvalStackValueComparisons =
     let rec ceq (var1 : EvalStackValue) (var2 : EvalStackValue) : bool =
         // Table III.4
         match var1, var2 with
-        | EvalStackValue.UserDefinedValueType {
-                                                  Fields = [ f ]
-                                              },
-          v -> ceq f.ContentsEval v
-        | u,
-          EvalStackValue.UserDefinedValueType {
-                                                  Fields = [ f ]
-                                              } -> ceq u f.ContentsEval
-        | EvalStackValue.UserDefinedValueType {
-                                                  Fields = []
-                                              },
-          EvalStackValue.UserDefinedValueType {
-                                                  Fields = []
-                                              } ->
-            // hmm, surely this can't happen, but :shrug:
-            true
-        | EvalStackValue.UserDefinedValueType _, _
-        | _, EvalStackValue.UserDefinedValueType _ -> failwith $"TODO: ceq {var1} vs {var2}"
+        | EvalStackValue.UserDefinedValueType var1, v ->
+            match CliValueType.TryExactlyOneField var1 with
+            | None -> failwith "TODO"
+            | Some var1 -> ceq (EvalStackValue.ofCliType var1.Contents) v
+        | u, EvalStackValue.UserDefinedValueType var2 ->
+            match CliValueType.TryExactlyOneField var2 with
+            | None -> failwith "TODO"
+            | Some var2 -> ceq u (EvalStackValue.ofCliType var2.Contents)
         | EvalStackValue.Int32 var1, EvalStackValue.Int32 var2 -> var1 = var2
         | EvalStackValue.Int32 var1, EvalStackValue.NativeInt var2 -> failwith "TODO: int32 CEQ nativeint"
         | EvalStackValue.Int32 _, _ -> failwith $"bad ceq: Int32 vs {var2}"
@@ -173,6 +163,7 @@ module EvalStackValueComparisons =
             | ManagedPointerSource.LocalVariable _
             | ManagedPointerSource.Argument _ -> false
             | ManagedPointerSource.ArrayIndex (arr, index) -> failwith "todo"
+            | ManagedPointerSource.InterpretedAsType (src, ty) -> failwith "todo"
         | EvalStackValue.ObjectRef _, _ -> failwith $"bad ceq: ObjectRef vs {var2}"
         | EvalStackValue.ManagedPointer var1, EvalStackValue.ManagedPointer var2 -> var1 = var2
         | EvalStackValue.ManagedPointer var1, EvalStackValue.NativeInt var2 ->

WoofWare.PawPrint/ExternImplementations/System.Threading.Monitor.fs

@@ -89,6 +89,7 @@ module System_Threading_Monitor =
                     | ManagedPointerSource.Heap addr -> failwith "todo: managed heap"
                     | ManagedPointerSource.ArrayIndex _ -> failwith "todo: array index"
                     | ManagedPointerSource.Field (managedPointerSource, fieldName) -> failwith "todo"
+                    | ManagedPointerSource.InterpretedAsType _ -> failwith "TODO"
 
                 (state, WhatWeDid.Executed) |> ExecutionResult.Stepped
 

WoofWare.PawPrint/FieldHandleRegistry.fs

@@ -1,5 +1,6 @@
 namespace WoofWare.PawPrint
 
+open System.Collections.Immutable
 open System.Reflection
 open System.Reflection.Metadata
 
@@ -33,8 +34,9 @@ module FieldHandleRegistry =
     /// Returns a (struct) System.RuntimeFieldHandle, with its contents (reference type) freshly allocated if necessary.
     let getOrAllocate
         (baseClassTypes : BaseClassTypes<'corelib>)
+        (allConcreteTypes : AllConcreteTypes)
         (allocState : 'allocState)
-        (allocate : CliField list -> 'allocState -> ManagedHeapAddress * 'allocState)
+        (allocate : CliValueType -> 'allocState -> ManagedHeapAddress * 'allocState)
         (declaringAssy : AssemblyName)
         (declaringType : ConcreteTypeHandle)
         (handle : FieldDefinitionHandle)
@@ -57,9 +59,17 @@ module FieldHandleRegistry =
                 Name = "m_ptr"
                 Contents = CliType.ofManagedObject runtimeFieldInfoStub
                 Offset = None
+                Type =
+                    AllConcreteTypes.findExistingConcreteType
+                        allConcreteTypes
+                        (baseClassTypes.RuntimeFieldInfoStub.Assembly,
+                         baseClassTypes.RuntimeFieldInfoStub.Namespace,
+                         baseClassTypes.RuntimeFieldInfoStub.Name,
+                         ImmutableArray.Empty)
+                    |> Option.get
             }
             |> List.singleton
-            |> CliValueType.OfFields
+            |> CliValueType.OfFields Layout.Default
             |> CliType.ValueType
 
         let handle =
@@ -88,50 +98,90 @@ module FieldHandleRegistry =
             // https://github.com/dotnet/runtime/blob/2b21c73fa2c32fa0195e4a411a435dda185efd08/src/coreclr/System.Private.CoreLib/src/System/RuntimeHandles.cs#L1380
             {
                 Name = "m_handle"
-                Contents = CliType.RuntimePointer (CliRuntimePointer.Unmanaged newHandle)
+                Contents = CliType.RuntimePointer (CliRuntimePointer.FieldRegistryHandle newHandle)
                 Offset = None // no struct layout was specified
+                Type =
+                    AllConcreteTypes.findExistingConcreteType
+                        allConcreteTypes
+                        (baseClassTypes.IntPtr.Assembly,
+                         baseClassTypes.IntPtr.Namespace,
+                         baseClassTypes.IntPtr.Name,
+                         ImmutableArray.Empty)
+                    |> Option.get
             }
             |> List.singleton
-            |> CliValueType.OfFields
+            |> CliValueType.OfFields Layout.Default
             |> CliType.ValueType
 
         // https://github.com/dotnet/runtime/blob/1d1bf92fcf43aa6981804dc53c5174445069c9e4/src/coreclr/System.Private.CoreLib/src/System/RuntimeHandles.cs#L1074
         let runtimeFieldInfoStub =
+            let objType =
+                AllConcreteTypes.findExistingConcreteType
+                    allConcreteTypes
+                    (baseClassTypes.Object.Assembly,
+                     baseClassTypes.Object.Namespace,
+                     baseClassTypes.Object.Name,
+                     ImmutableArray.Empty)
+                |> Option.get
+
+            let intType =
+                AllConcreteTypes.findExistingConcreteType
+                    allConcreteTypes
+                    (baseClassTypes.Int32.Assembly,
+                     baseClassTypes.Int32.Namespace,
+                     baseClassTypes.Int32.Name,
+                     ImmutableArray.Empty)
+                |> Option.get
+
             // LayoutKind.Sequential
             [
                 // If we ever implement a GC, something should change here
                 {
                     Name = "m_keepalive"
                     Contents = CliType.ObjectRef None
-                    Offset = Some 0
+                    Offset = None
+                    Type = objType
                 }
                 {
                     Name = "m_c"
                     Contents = CliType.ObjectRef None
-                    Offset = Some SIZEOF_OBJ
+                    Offset = None
+                    Type = objType
                 }
                 {
                     Name = "m_d"
                     Contents = CliType.ObjectRef None
-                    Offset = Some (SIZEOF_OBJ * 2)
+                    Offset = None
+                    Type = objType
                 }
                 {
                     Name = "m_b"
                     Contents = CliType.Numeric (CliNumericType.Int32 0)
-                    Offset = Some (SIZEOF_OBJ * 3)
+                    Offset = None
+                    Type = intType
                 }
                 {
                     Name = "m_e"
                     Contents = CliType.ObjectRef None
-                    Offset = Some (SIZEOF_OBJ * 3 + SIZEOF_INT)
+                    Offset = None
+                    Type = objType
                 }
                 // RuntimeFieldHandleInternal: https://github.com/dotnet/runtime/blob/1d1bf92fcf43aa6981804dc53c5174445069c9e4/src/coreclr/System.Private.CoreLib/src/System/RuntimeHandles.cs#L1048
                 {
                     Name = "m_fieldHandle"
                     Contents = runtimeFieldHandleInternal
-                    Offset = Some (SIZEOF_OBJ * 4 + SIZEOF_INT)
+                    Offset = None
+                    Type =
+                        AllConcreteTypes.findExistingConcreteType
+                            allConcreteTypes
+                            (baseClassTypes.RuntimeFieldHandleInternal.Assembly,
+                             baseClassTypes.RuntimeFieldHandleInternal.Namespace,
+                             baseClassTypes.RuntimeFieldHandleInternal.Name,
+                             ImmutableArray.Empty)
+                        |> Option.get
                 }
             ]
+            |> CliValueType.OfFields Layout.Default // explicitly sequential but no custom packing size
 
         let alloc, state = allocate runtimeFieldInfoStub allocState
 

WoofWare.PawPrint/IlMachineState.fs

@@ -149,7 +149,73 @@ type StateLoadResult =
 module IlMachineState =
     type private Dummy = class end
 
+    let private loadAssembly'
+        (loggerFactory : ILoggerFactory)
+        (dotnetRuntimeDirs : string seq)
+        (referencedInAssembly : DumpedAssembly)
+        (r : AssemblyReferenceHandle)
+        (assemblies : ImmutableDictionary<string, DumpedAssembly>)
+        =
+        let assemblyRef = referencedInAssembly.AssemblyReferences.[r]
+        let assemblyName = assemblyRef.Name
+
+        match assemblies.TryGetValue assemblyName.FullName with
+        | true, v -> v, assemblyName
+        | false, _ ->
+            let logger = loggerFactory.CreateLogger typeof<Dummy>.DeclaringType
+
+            let assy =
+                dotnetRuntimeDirs
+                |> Seq.choose (fun dir ->
+                    let file = Path.Combine (dir, assemblyName.Name + ".dll")
+
+                    try
+                        use f = File.OpenRead file
+                        logger.LogInformation ("Loading assembly from file {AssemblyFileLoadPath}", file)
+                        Assembly.read loggerFactory (Some file) f |> Some
+                    with :? FileNotFoundException ->
+                        None
+                )
+                |> Seq.toList
+
+            match assy |> List.tryHead with
+            | None -> failwith $"Could not find a readable DLL in any runtime dir with name %s{assemblyName.Name}.dll"
+            | Some assy -> assy, assemblyName
+
+    /// <summary>
+    /// Create a new IlMachineState which has loaded the given assembly.
+    /// This involves reading assemblies from the disk and doing a complete parse of them, so it might be quite slow!
+    ///
+    /// This function doesn't do anything if the referenced assembly has already been loaded.
+    /// </summary>
+    /// <param name="loggerFactory">LoggerFactory into which to emit logs.</param>
+    /// <param name="referencedInAssembly">The assembly which contains an AssemblyReference which causes us to want to load a new assembly.</param>
+    /// <param name="r">The AssemblyReferenceHandle pointing at an assembly we want to load. *Important*: this is an AssemblyReferenceHandle from <c>referencedInAssembly</c>; in general, AssemblyReferenceHandles are only well-defined if you know what assembly they were defined in.</param>
+    /// <param name="state">The immutable state to augment with the new assembly.</param>
+    let loadAssembly
+        (loggerFactory : ILoggerFactory)
+        (referencedInAssembly : DumpedAssembly)
+        (r : AssemblyReferenceHandle)
+        (state : IlMachineState)
+        : IlMachineState * DumpedAssembly * AssemblyName
+        =
+        let dumped, assy =
+            loadAssembly' loggerFactory state.DotnetRuntimeDirs referencedInAssembly r state._LoadedAssemblies
+
+        state.WithLoadedAssembly assy dumped, dumped, assy
+
+    let private loader (loggerFactory : ILoggerFactory) (state : IlMachineState) : IAssemblyLoad =
+        { new IAssemblyLoad with
+            member _.LoadAssembly loaded assyName ref =
+                let targetAssy, name =
+                    loadAssembly' loggerFactory state.DotnetRuntimeDirs loaded.[assyName.FullName] ref loaded
+
+                let newAssys = loaded.SetItem (name.FullName, targetAssy)
+                newAssys, targetAssy
+        }
+
     let concretizeType
+        (loggerFactory : ILoggerFactory)
         (baseClassTypes : BaseClassTypes<DumpedAssembly>)
         (state : IlMachineState)
         (declaringAssembly : AssemblyName)
@@ -169,14 +235,7 @@ module IlMachineState =
         let handle, ctx =
             TypeConcretization.concretizeType
                 ctx
-                (fun assyName ref ->
-                    let currentAssy = state.LoadedAssembly assyName |> Option.get
-
-                    let targetAssy =
-                        currentAssy.AssemblyReferences.[ref].Name |> state.LoadedAssembly |> Option.get
-
-                    state._LoadedAssemblies, targetAssy
-                )
+                (loader loggerFactory state)
                 declaringAssembly
                 typeGenerics
                 methodGenerics
@@ -190,51 +249,6 @@ module IlMachineState =
 
         state, handle
 
-    /// <summary>
-    /// Create a new IlMachineState which has loaded the given assembly.
-    /// This involves reading assemblies from the disk and doing a complete parse of them, so it might be quite slow!
-    ///
-    /// This function doesn't do anything if the referenced assembly has already been loaded.
-    /// </summary>
-    /// <param name="loggerFactory">LoggerFactory into which to emit logs.</param>
-    /// <param name="referencedInAssembly">The assembly which contains an AssemblyReference which causes us to want to load a new assembly.</param>
-    /// <param name="r">The AssemblyReferenceHandle pointing at an assembly we want to load. *Important*: this is an AssemblyReferenceHandle from <c>referencedInAssembly</c>; in general, AssemblyReferenceHandles are only well-defined if you know what assembly they were defined in.</param>
-    /// <param name="state">The immutable state to augment with the new assembly.</param>
-    let loadAssembly
-        (loggerFactory : ILoggerFactory)
-        (referencedInAssembly : DumpedAssembly)
-        (r : AssemblyReferenceHandle)
-        (state : IlMachineState)
-        : IlMachineState * DumpedAssembly * AssemblyName
-        =
-        let assemblyRef = referencedInAssembly.AssemblyReferences.[r]
-        let assemblyName = assemblyRef.Name
-
-        match state.LoadedAssembly assemblyName with
-        | Some v -> state, v, assemblyName
-        | None ->
-            let logger = loggerFactory.CreateLogger typeof<Dummy>.DeclaringType
-
-            let assy =
-                state.DotnetRuntimeDirs
-                |> Seq.choose (fun dir ->
-                    let file = Path.Combine (dir, assemblyName.Name + ".dll")
-
-                    try
-                        use f = File.OpenRead file
-                        logger.LogInformation ("Loading assembly from file {AssemblyFileLoadPath}", file)
-                        Assembly.read loggerFactory (Some file) f |> Some
-                    with :? FileNotFoundException ->
-                        None
-                )
-                |> Seq.toList
-
-            match assy |> List.tryHead with
-            | None -> failwith $"Could not find a readable DLL in any runtime dir with name %s{assemblyName.Name}.dll"
-            | Some assy ->
-
-            state.WithLoadedAssembly assemblyName assy, assy, assemblyName
-
     let rec internal resolveTypeFromName
         (loggerFactory : ILoggerFactory)
         (ns : string option)
@@ -440,6 +454,54 @@ module IlMachineState =
 
         resolveTypeFromDefn loggerFactory baseClassTypes sign typeGenericArgsAsDefn methodGenericArgsAsDefn assy state
 
+    /// Resolve a TypeDefinition using concrete type handles from execution context
+    let resolveTypeFromDefnConcrete
+        (loggerFactory : ILoggerFactory)
+        (baseClassTypes : BaseClassTypes<DumpedAssembly>)
+        (ty : TypeDefinitionHandle)
+        (assy : DumpedAssembly)
+        (typeGenericArgs : ConcreteTypeHandle ImmutableArray)
+        (methodGenericArgs : ConcreteTypeHandle ImmutableArray)
+        (state : IlMachineState)
+        : IlMachineState * DumpedAssembly * WoofWare.PawPrint.TypeInfo<TypeDefn, TypeDefn>
+        =
+        let typeDef = assy.TypeDefs.[ty]
+
+        // Convert ConcreteTypeHandle to TypeDefn for the generics
+        let typeGenericArgsAsDefn =
+            typeGenericArgs
+            |> Seq.map (fun handle ->
+                Concretization.concreteHandleToTypeDefn
+                    baseClassTypes
+                    handle
+                    state.ConcreteTypes
+                    state._LoadedAssemblies
+            )
+            |> ImmutableArray.CreateRange
+
+        let methodGenericArgsAsDefn =
+            methodGenericArgs
+            |> Seq.map (fun handle ->
+                Concretization.concreteHandleToTypeDefn
+                    baseClassTypes
+                    handle
+                    state.ConcreteTypes
+                    state._LoadedAssemblies
+            )
+            |> ImmutableArray.CreateRange
+
+        // Map the type definition's generics using the provided type generic arguments
+        let resolvedTypeDef =
+            typeDef
+            |> TypeInfo.mapGeneric (fun (param, _) ->
+                if param.SequenceNumber < typeGenericArgsAsDefn.Length then
+                    typeGenericArgsAsDefn.[param.SequenceNumber]
+                else
+                    failwithf "Generic type parameter %d out of range" param.SequenceNumber
+            )
+
+        state, assy, resolvedTypeDef
+
     /// Get zero value for a type that's already been concretized
     let cliTypeZeroOfHandle
         (state : IlMachineState)
@@ -482,26 +544,6 @@ module IlMachineState =
                 BaseTypes = baseClassTypes
             }
 
-        // Helper function to get assembly from reference
-        let loadAssembly
-            (currentAssembly : AssemblyName)
-            (assyRef : AssemblyReferenceHandle)
-            : ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly
-            =
-            let assyToLoad =
-                match state.LoadedAssembly currentAssembly with
-                | Some assy -> assy
-                | None -> failwithf "Assembly %s not loaded" currentAssembly.FullName
-
-            let referencedAssy = assyToLoad.AssemblyReferences.[assyRef]
-
-            match state.LoadedAssembly referencedAssy.Name with
-            | Some assy -> state._LoadedAssemblies, assy
-            | None ->
-                // Need to load the assembly
-                let newState, loadedAssy, _ = loadAssembly loggerFactory assyToLoad assyRef state
-                newState._LoadedAssemblies, loadedAssy
-
         // Concretize each generic argument first
         let mutable currentCtx = ctx
         let genericHandles = ImmutableArray.CreateBuilder declaringType.Generics.Length
@@ -510,7 +552,7 @@ module IlMachineState =
             let handle, newCtx =
                 TypeConcretization.concretizeType
                     currentCtx
-                    loadAssembly
+                    (loader loggerFactory state)
                     declaringType.Assembly
                     ImmutableArray.Empty // No type generics in this context
                     ImmutableArray.Empty // No method generics in this context
@@ -522,12 +564,13 @@ module IlMachineState =
         // Now we need to concretize the type definition itself
         // If it's a non-generic type, we can use concretizeTypeDefinition directly
         if declaringType.Generics.IsEmpty then
-            let handle, newCtx =
+            let handle, currentCtx =
                 TypeConcretization.concretizeTypeDefinition currentCtx declaringType.Assembly declaringType.Definition
 
             let newState =
                 { state with
-                    ConcreteTypes = newCtx.ConcreteTypes
+                    ConcreteTypes = currentCtx.ConcreteTypes
+                    _LoadedAssemblies = currentCtx.LoadedAssemblies
                 }
 
             handle, newState
@@ -571,7 +614,7 @@ module IlMachineState =
         (typeGenerics : ConcreteTypeHandle ImmutableArray)
         (methodGenerics : ConcreteTypeHandle ImmutableArray)
         (state : IlMachineState)
-        : IlMachineState * CliType
+        : IlMachineState * CliType * ConcreteTypeHandle
         =
 
         // First concretize the type
@@ -583,11 +626,11 @@ module IlMachineState =
                 state.WithLoadedAssembly assy.Name assy
 
         let state, handle =
-            concretizeType baseClassTypes state assy.Name typeGenerics methodGenerics ty
+            concretizeType loggerFactory baseClassTypes state assy.Name typeGenerics methodGenerics ty
 
         // Now get the zero value
         let zero, state = cliTypeZeroOfHandle state baseClassTypes handle
-        state, zero
+        state, zero, handle
 
     let pushToEvalStack' (o : EvalStackValue) (thread : ThreadId) (state : IlMachineState) =
         let activeThreadState = state.ThreadState.[thread]
@@ -710,14 +753,9 @@ module IlMachineState =
             | ResolvedBaseType.Delegate
             | ResolvedBaseType.Object -> state |> pushToEvalStack (CliType.ofManagedObject constructing) currentThread
             | ResolvedBaseType.ValueType ->
-                let vt =
-                    {
-                        CliValueType.Fields = constructed.Fields
-                    }
-
                 state
                 // TODO: ordering of fields probably important
-                |> pushToEvalStack (CliType.ValueType vt) currentThread
+                |> pushToEvalStack (CliType.ValueType constructed.Contents) currentThread
             | ResolvedBaseType.Enum -> failwith "TODO"
         | None ->
             match threadStateAtEndOfMethod.MethodState.EvaluationStack.Values with
@@ -759,22 +797,7 @@ module IlMachineState =
         let concretizedMethod, newConcreteTypes, newAssemblies =
             Concretization.concretizeMethod
                 state.ConcreteTypes
-                (fun assyName ref ->
-                    match state.LoadedAssembly assyName with
-                    | Some currentAssy ->
-                        let targetAssyRef = currentAssy.AssemblyReferences.[ref]
-
-                        match state.LoadedAssembly targetAssyRef.Name with
-                        | Some _ ->
-                            // Assembly already loaded, return existing state
-                            state._LoadedAssemblies, state._LoadedAssemblies.[targetAssyRef.Name.FullName]
-                        | None ->
-                            // Need to load the assembly
-                            let newState, loadedAssy, _ = loadAssembly loggerFactory currentAssy ref state
-                            newState._LoadedAssemblies, loadedAssy
-                    | None ->
-                        failwithf "Current assembly %s not loaded when trying to resolve reference" assyName.FullName
-                )
+                (loader loggerFactory state)
                 state._LoadedAssemblies
                 baseClassTypes
                 methodToCall
@@ -820,6 +843,7 @@ module IlMachineState =
                 for i = 0 to generics.Length - 1 do
                     let state2, handle =
                         concretizeType
+                            loggerFactory
                             baseClassTypes
                             state
                             callingAssembly
@@ -875,14 +899,7 @@ module IlMachineState =
                     let handle, newCtx =
                         TypeConcretization.concretizeType
                             ctx
-                            (fun assyName ref ->
-                                let currentAssy = state.LoadedAssembly assyName |> Option.get
-
-                                let targetAssy =
-                                    currentAssy.AssemblyReferences.[ref].Name |> state.LoadedAssembly |> Option.get
-
-                                state._LoadedAssemblies, targetAssy
-                            )
+                            (loader loggerFactory state)
                             (state.ActiveAssembly thread).Name
                             ImmutableArray.Empty // No type generics for the concretization context
                             ImmutableArray.Empty // No method generics for the concretization context
@@ -893,6 +910,7 @@ module IlMachineState =
                     state <-
                         { state with
                             ConcreteTypes = newCtx.ConcreteTypes
+                            _LoadedAssemblies = newCtx.LoadedAssemblies
                         }
 
                 handles.ToImmutable (), state
@@ -997,14 +1015,7 @@ module IlMachineState =
         let declaringHandle, newCtx =
             TypeConcretization.concretizeType
                 ctx
-                (fun assyName ref ->
-                    let currentAssy = state.LoadedAssembly assyName |> Option.get
-
-                    let targetAssy =
-                        currentAssy.AssemblyReferences.[ref].Name |> state.LoadedAssembly |> Option.get
-
-                    state._LoadedAssemblies, targetAssy
-                )
+                (loader loggerFactory state)
                 field.DeclaringType.Assembly
                 contextTypeGenerics
                 contextMethodGenerics
@@ -1113,13 +1124,13 @@ module IlMachineState =
 
     let allocateManagedObject
         (ty : ConcreteTypeHandle)
-        (fields : CliField list)
+        (fields : CliValueType)
         (state : IlMachineState)
         : ManagedHeapAddress * IlMachineState
         =
         let o =
             {
-                Fields = fields
+                Contents = fields
                 ConcreteType = ty
                 SyncBlock = SyncBlock.Free
             }
@@ -1190,6 +1201,7 @@ module IlMachineState =
         (baseClassTypes : BaseClassTypes<DumpedAssembly>)
         (currentThread : ThreadId)
         (assy : DumpedAssembly)
+        (genericMethodTypeArgs : ImmutableArray<ConcreteTypeHandle>)
         (m : MemberReferenceHandle)
         (state : IlMachineState)
         : IlMachineState *
@@ -1253,6 +1265,7 @@ module IlMachineState =
                 // TODO: generics?
                 let state, t =
                     concretizeType
+                        loggerFactory
                         baseClassTypes
                         state
                         targetType.Assembly
@@ -1270,6 +1283,7 @@ module IlMachineState =
             // Concretize the field signature from the member reference
             let state, concreteFieldSig =
                 concretizeType
+                    loggerFactory
                     baseClassTypes
                     state
                     (state.ActiveAssembly(currentThread).Name)
@@ -1287,6 +1301,7 @@ module IlMachineState =
                         // Concretize the field's signature for comparison
                         let state, fieldSigConcrete =
                             concretizeType
+                                loggerFactory
                                 baseClassTypes
                                 state
                                 assy.Name
@@ -1324,11 +1339,12 @@ module IlMachineState =
                     state
                     (fun state ty ->
                         concretizeType
+                            loggerFactory
                             baseClassTypes
                             state
                             (state.ActiveAssembly(currentThread).Name)
                             concreteExtractedTypeArgs
-                            ImmutableArray.Empty
+                            genericMethodTypeArgs
                             ty
                     )
 
@@ -1341,11 +1357,12 @@ module IlMachineState =
                             state
                             (fun state ty ->
                                 concretizeType
+                                    loggerFactory
                                     baseClassTypes
                                     state
                                     assy.Name
                                     concreteExtractedTypeArgs
-                                    ImmutableArray.Empty
+                                    genericMethodTypeArgs
                                     ty
                             )
 
@@ -1417,6 +1434,7 @@ module IlMachineState =
         | ManagedPointerSource.ArrayIndex (arr, index) -> getArrayValue arr index state |> CliType.getField fieldName
         | ManagedPointerSource.Field (src, fieldName) -> failwith "todo"
         | ManagedPointerSource.Null -> failwith "TODO: throw NRE"
+        | ManagedPointerSource.InterpretedAsType (src, ty) -> failwith "TODO"
 
     let setFieldValue
         (obj : ManagedPointerSource)
@@ -1446,8 +1464,14 @@ module IlMachineState =
             state |> setArrayValue arr v index
         | ManagedPointerSource.Field (managedPointerSource, fieldName) -> failwith "todo"
         | ManagedPointerSource.Null -> failwith "TODO: throw NRE"
+        | ManagedPointerSource.InterpretedAsType (src, ty) -> failwith "TODO"
 
-    let executeDelegateConstructor (instruction : MethodState) (state : IlMachineState) : IlMachineState =
+    let executeDelegateConstructor
+        (baseClassTypes : BaseClassTypes<DumpedAssembly>)
+        (instruction : MethodState)
+        (state : IlMachineState)
+        : IlMachineState
+        =
         // We've been called with arguments already popped from the stack into local arguments.
         let constructing = instruction.Arguments.[0]
         let targetObj = instruction.Arguments.[1]
@@ -1455,17 +1479,17 @@ module IlMachineState =
 
         let targetObj =
             match targetObj with
-            | CliType.RuntimePointer (CliRuntimePointer.Managed (CliRuntimePointerSource.Heap target))
+            | CliType.RuntimePointer (CliRuntimePointer.Managed (ManagedPointerSource.Heap target))
             | CliType.ObjectRef (Some target) -> Some target
             | CliType.ObjectRef None
-            | CliType.RuntimePointer (CliRuntimePointer.Managed CliRuntimePointerSource.Null) -> None
+            | CliType.RuntimePointer (CliRuntimePointer.Managed ManagedPointerSource.Null) -> None
             | _ -> failwith $"Unexpected target type for delegate: {targetObj}"
 
         let constructing =
             match constructing with
-            | CliType.RuntimePointer (CliRuntimePointer.Managed CliRuntimePointerSource.Null)
+            | CliType.RuntimePointer (CliRuntimePointer.Managed ManagedPointerSource.Null)
             | CliType.ObjectRef None -> failwith "unexpectedly constructing the null delegate"
-            | CliType.RuntimePointer (CliRuntimePointer.Managed (CliRuntimePointerSource.Heap target))
+            | CliType.RuntimePointer (CliRuntimePointer.Managed (ManagedPointerSource.Heap target))
             | CliType.ObjectRef (Some target) -> target
             | _ -> failwith $"Unexpectedly not constructing a managed object: {constructing}"
 
@@ -1476,24 +1500,42 @@ module IlMachineState =
 
         // Standard delegate fields in .NET are _target and _methodPtr
         // Update the fields with the target object and method pointer
-        let updatedFields =
-            // Let's not consider field ordering for reference types like delegates.
-            // Nobody's going to be marshalling a reference type anyway, I hope.
-            {
-                Name = "_target"
-                Contents = CliType.ObjectRef targetObj
-                Offset = None
-            }
-            :: {
-                   Name = "_methodPtr"
-                   Contents = methodPtr
-                   Offset = None
-               }
-            :: heapObj.Fields
+        let allConcreteTypes = state.ConcreteTypes
 
         let updatedObj =
+            let newContents =
+                heapObj.Contents
+                |> CliValueType.AddField
+                    {
+                        Name = "_target"
+                        Contents = CliType.ObjectRef targetObj
+                        Offset = None
+                        Type =
+                            AllConcreteTypes.findExistingConcreteType
+                                allConcreteTypes
+                                (baseClassTypes.Object.Assembly,
+                                 baseClassTypes.Object.Namespace,
+                                 baseClassTypes.Object.Name,
+                                 ImmutableArray.Empty)
+                            |> Option.get
+                    }
+                |> CliValueType.AddField
+                    {
+                        Name = "_methodPtr"
+                        Contents = methodPtr
+                        Offset = None
+                        Type =
+                            AllConcreteTypes.findExistingConcreteType
+                                allConcreteTypes
+                                (baseClassTypes.Object.Assembly,
+                                 baseClassTypes.Object.Namespace,
+                                 baseClassTypes.Object.Name,
+                                 ImmutableArray.Empty)
+                            |> Option.get
+                    }
+
             { heapObj with
-                Fields = updatedFields
+                Contents = newContents
             }
 
         let updatedHeap =
@@ -1507,6 +1549,7 @@ module IlMachineState =
 
     /// Returns the type handle and an allocated System.RuntimeType.
     let getOrAllocateType
+        (loggerFactory : ILoggerFactory)
         (baseClassTypes : BaseClassTypes<DumpedAssembly>)
         (defn : ConcreteTypeHandle)
         (state : IlMachineState)
@@ -1518,10 +1561,18 @@ module IlMachineState =
                 baseClassTypes.Corelib.Name.FullName,
                 SignatureTypeKind.Class
             )
-            |> concretizeType baseClassTypes state baseClassTypes.Corelib.Name ImmutableArray.Empty ImmutableArray.Empty
+            |> concretizeType
+                loggerFactory
+                baseClassTypes
+                state
+                baseClassTypes.Corelib.Name
+                ImmutableArray.Empty
+                ImmutableArray.Empty
 
         let result, reg, state =
             TypeHandleRegistry.getOrAllocate
+                state.ConcreteTypes
+                baseClassTypes
                 state
                 (fun fields state -> allocateManagedObject runtimeType fields state)
                 defn
@@ -1562,11 +1613,18 @@ module IlMachineState =
                 baseClassTypes.Corelib.Name.FullName,
                 SignatureTypeKind.Class
             )
-            |> concretizeType baseClassTypes state baseClassTypes.Corelib.Name ImmutableArray.Empty ImmutableArray.Empty
+            |> concretizeType
+                loggerFactory
+                baseClassTypes
+                state
+                baseClassTypes.Corelib.Name
+                ImmutableArray.Empty
+                ImmutableArray.Empty
 
         let result, reg, state =
             FieldHandleRegistry.getOrAllocate
                 baseClassTypes
+                state.ConcreteTypes
                 state
                 (fun fields state -> allocateManagedObject runtimeType fields state)
                 declaringAssy
@@ -1612,7 +1670,10 @@ module IlMachineState =
             state.ThreadState.[sourceThread].MethodStates.[methodFrame].LocalVariables.[int<uint16> whichVar]
         | ManagedPointerSource.Argument (sourceThread, methodFrame, whichVar) ->
             state.ThreadState.[sourceThread].MethodStates.[methodFrame].Arguments.[int<uint16> whichVar]
-        | ManagedPointerSource.Heap addr -> failwith "todo"
+        | ManagedPointerSource.Heap addr ->
+            let result = ManagedHeap.get addr state.ManagedHeap
+            // TODO: this is awfully dubious, this ain't no value type
+            CliType.ValueType result.Contents
         | ManagedPointerSource.ArrayIndex (arr, index) -> getArrayValue arr index state
         | ManagedPointerSource.Field (addr, name) ->
             let obj = dereferencePointer state addr
@@ -1620,6 +1681,19 @@ module IlMachineState =
             match obj with
             | CliType.ValueType vt -> vt |> CliValueType.DereferenceField name
             | v -> failwith $"could not find field {name} on object {v}"
+        | ManagedPointerSource.InterpretedAsType (src, ty) ->
+            let src = dereferencePointer state src
+
+            let concrete =
+                match
+                    AllConcreteTypes.findExistingConcreteType
+                        state.ConcreteTypes
+                        (ty.Assembly, ty.Namespace, ty.Name, ty.Generics)
+                with
+                | Some ty -> ty
+                | None -> failwith "not concretised type"
+
+            failwith $"TODO: interpret as type %s{ty.Assembly.Name}.%s{ty.Namespace}.%s{ty.Name}, object %O{src}"
 
     let lookupTypeDefn
         (baseClassTypes : BaseClassTypes<DumpedAssembly>)

WoofWare.PawPrint/IlMachineStateExecution.fs

@@ -10,6 +10,7 @@ open Microsoft.Extensions.Logging
 [<RequireQualifiedAccess>]
 module IlMachineStateExecution =
     let getTypeOfObj
+        (loggerFactory : ILoggerFactory)
         (baseClassTypes : BaseClassTypes<DumpedAssembly>)
         (state : IlMachineState)
         (esv : EvalStackValue)
@@ -19,6 +20,7 @@ module IlMachineStateExecution =
         | EvalStackValue.Int32 _ ->
             DumpedAssembly.typeInfoToTypeDefn' baseClassTypes state._LoadedAssemblies baseClassTypes.Int32
             |> IlMachineState.concretizeType
+                loggerFactory
                 baseClassTypes
                 state
                 baseClassTypes.Corelib.Name
@@ -27,6 +29,7 @@ module IlMachineStateExecution =
         | EvalStackValue.Int64 _ ->
             DumpedAssembly.typeInfoToTypeDefn' baseClassTypes state._LoadedAssemblies baseClassTypes.Int64
             |> IlMachineState.concretizeType
+                loggerFactory
                 baseClassTypes
                 state
                 baseClassTypes.Corelib.Name
@@ -36,6 +39,7 @@ module IlMachineStateExecution =
         | EvalStackValue.Float _ ->
             DumpedAssembly.typeInfoToTypeDefn' baseClassTypes state._LoadedAssemblies baseClassTypes.Double
             |> IlMachineState.concretizeType
+                loggerFactory
                 baseClassTypes
                 state
                 baseClassTypes.Corelib.Name
@@ -51,6 +55,7 @@ module IlMachineStateExecution =
             | ManagedPointerSource.ArrayIndex (arr, index) -> failwith "todo"
             | ManagedPointerSource.Null -> failwith "todo"
             | ManagedPointerSource.Field (managedPointerSource, fieldName) -> failwith "todo"
+            | ManagedPointerSource.InterpretedAsType (src, ty) -> failwith "todo"
         | EvalStackValue.ObjectRef addr ->
             let o = ManagedHeap.get addr state.ManagedHeap
             state, o.ConcreteType
@@ -113,16 +118,13 @@ module IlMachineStateExecution =
 
         match
             if isIntrinsic then
-                Intrinsics.call baseClassTypes methodToCall thread state
+                Intrinsics.call loggerFactory baseClassTypes methodToCall thread state
             else
                 None
         with
         | Some result -> result
         | None ->
 
-        if methodToCall.Name = "GetValue" then
-            printfn ""
-
         // Get zero values for all parameters
         let state, argZeroObjects =
             ((state, []), methodToCall.Signature.ParameterTypes)
@@ -156,7 +158,8 @@ module IlMachineStateExecution =
                     | None -> failwith "unexpectedly no `this` on the eval stack of instance method"
                     | Some this -> this
 
-                let state, callingObjTyHandle = getTypeOfObj baseClassTypes state callingObj
+                let state, callingObjTyHandle =
+                    getTypeOfObj loggerFactory baseClassTypes state callingObj
 
                 let callingObjTy =
                     let ty =
@@ -200,6 +203,7 @@ module IlMachineStateExecution =
                         let state, retType =
                             meth.Signature.ReturnType
                             |> IlMachineState.concretizeType
+                                loggerFactory
                                 baseClassTypes
                                 state
                                 meth.DeclaringType.Assembly
@@ -211,6 +215,7 @@ module IlMachineStateExecution =
                             ||> Seq.mapFold (fun state ty ->
                                 ty
                                 |> IlMachineState.concretizeType
+                                    loggerFactory
                                     baseClassTypes
                                     state
                                     meth.DeclaringType.Assembly
@@ -407,7 +412,7 @@ module IlMachineStateExecution =
                     // where Newobj puts the object pointer on top
                     let thisArg, newState =
                         popAndCoerceArg
-                            (CliType.RuntimePointer (CliRuntimePointer.Managed CliRuntimePointerSource.Null))
+                            (CliType.RuntimePointer (CliRuntimePointer.Managed ManagedPointerSource.Null))
                             currentState
 
                     currentState <- newState
@@ -430,7 +435,7 @@ module IlMachineStateExecution =
 
                     let thisArg, newState =
                         popAndCoerceArg
-                            (CliType.RuntimePointer (CliRuntimePointer.Managed CliRuntimePointerSource.Null))
+                            (CliType.RuntimePointer (CliRuntimePointer.Managed ManagedPointerSource.Null))
                             currentState
 
                     args.Add thisArg
@@ -573,6 +578,7 @@ module IlMachineStateExecution =
                         // Concretize the base type
                         let state, baseTypeHandle =
                             IlMachineState.concretizeType
+                                loggerFactory
                                 baseClassTypes
                                 state
                                 sourceAssembly.Name
@@ -612,6 +618,7 @@ module IlMachineStateExecution =
                         // Concretize the base type
                         let state, baseTypeHandle =
                             IlMachineState.concretizeType
+                                loggerFactory
                                 baseClassTypes
                                 state
                                 sourceAssembly.Name
@@ -663,6 +670,7 @@ module IlMachineStateExecution =
                         state
                         (fun state typeDefn ->
                             IlMachineState.concretizeType
+                                loggerFactory
                                 baseClassTypes
                                 state
                                 concreteType.Assembly
@@ -687,6 +695,7 @@ module IlMachineStateExecution =
                                     ||> Seq.fold (fun (state, acc) typeDefn ->
                                         let state, handle =
                                             IlMachineState.concretizeType
+                                                loggerFactory
                                                 baseClassTypes
                                                 state
                                                 concreteType.Assembly

WoofWare.PawPrint/Intrinsics.fs

@@ -1,6 +1,8 @@
 namespace WoofWare.PawPrint
 
 open System
+open System.Collections.Immutable
+open Microsoft.Extensions.Logging
 
 [<RequireQualifiedAccess>]
 module Intrinsics =
@@ -14,10 +16,99 @@ module Intrinsics =
             "System.Private.CoreLib", "ArgumentNullException", "ThrowIfNull"
             // https://github.com/dotnet/runtime/blob/ec11903827fc28847d775ba17e0cd1ff56cfbc2e/src/coreclr/System.Private.CoreLib/src/System/Type.CoreCLR.cs#L82
             "System.Private.CoreLib", "Type", "GetTypeFromHandle"
+            // https://github.com/dotnet/runtime/blob/108fa7856efcfd39bc991c2d849eabbf7ba5989c/src/libraries/System.Private.CoreLib/src/System/ReadOnlySpan.cs#L161
+            "System.Private.CoreLib", "ReadOnlySpan`1", "get_Length"
+            // https://github.com/dotnet/runtime/blob/9e5e6aa7bc36aeb2a154709a9d1192030c30a2ef/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.cs#L153
+            "System.Private.CoreLib", "RuntimeHelpers", "CreateSpan"
+            // https://github.com/dotnet/runtime/blob/d258af50034c192bf7f0a18856bf83d2903d98ae/src/libraries/System.Private.CoreLib/src/System/Math.cs#L127
+            // https://github.com/dotnet/runtime/blob/d258af50034c192bf7f0a18856bf83d2903d98ae/src/libraries/System.Private.CoreLib/src/System/Math.cs#L137
+            "System.Private.CoreLib", "Math", "Abs"
+            // https://github.com/dotnet/runtime/blob/d258af50034c192bf7f0a18856bf83d2903d98ae/src/libraries/System.Private.CoreLib/src/System/Math.cs#L965C10-L1062C19
+            "System.Private.CoreLib", "Math", "Max"
+            // https://github.com/dotnet/runtime/blob/d258af50034c192bf7f0a18856bf83d2903d98ae/src/libraries/System.Private.CoreLib/src/System/Buffer.cs#L150
+            "System.Private.CoreLib", "Buffer", "Memmove"
+            // https://github.com/dotnet/runtime/blob/1c3221b63340d7f81dfd829f3bcd822e582324f6/src/libraries/System.Private.CoreLib/src/System/Threading/Thread.cs#L799
+            "System.Private.CoreLib", "Thread", "get_CurrentThread"
         ]
         |> Set.ofList
 
+    type private RefTypeProcessingStatus =
+        | InProgress
+        | Completed of bool
+
+    let rec private containsRefType
+        (loggerFactory : ILoggerFactory)
+        (baseClassTypes : BaseClassTypes<DumpedAssembly>)
+        (state : IlMachineState)
+        (seenSoFar : ImmutableDictionary<TypeInfo<TypeDefn, TypeDefn>, RefTypeProcessingStatus>)
+        (td : TypeInfo<TypeDefn, TypeDefn>)
+        : IlMachineState * ImmutableDictionary<_, RefTypeProcessingStatus> * bool
+        =
+        match seenSoFar.TryGetValue td with
+        | true, InProgress ->
+            // We've hit a cycle. Optimistically assume this path does not introduce a reference type.
+            // If another path finds a reference type, its 'true' will override this.
+            state, seenSoFar, false
+        | true, Completed v ->
+            // We've already calculated this; return the memoized result.
+            state, seenSoFar, v
+        | false, _ ->
+            // Check if this type itself is a reference type.
+            let baseType =
+                td.BaseType
+                |> DumpedAssembly.resolveBaseType baseClassTypes state._LoadedAssemblies td.Assembly
+
+            match baseType with
+            | ResolvedBaseType.Delegate
+            | ResolvedBaseType.Object ->
+                // Short-circuit: if the type itself is a reference type, we're done.
+                let seenSoFar = seenSoFar.Add (td, Completed true)
+                state, seenSoFar, true
+            | ResolvedBaseType.Enum
+            | ResolvedBaseType.ValueType ->
+                // It's a value type, so we must check its fields.
+                // Mark as in progress before recursing.
+                let seenSoFarWithInProgress = seenSoFar.Add (td, InProgress)
+
+                let stateAfterFieldResolution, nonStaticFields =
+                    ((state, []), td.Fields)
+                    ||> List.fold (fun (currentState, acc) field ->
+                        if field.IsStatic then
+                            currentState, acc
+                        else
+                            // TODO: generics
+                            let newState, _, info =
+                                IlMachineState.resolveTypeFromDefn
+                                    loggerFactory
+                                    baseClassTypes
+                                    field.Signature
+                                    ImmutableArray.Empty
+                                    ImmutableArray.Empty
+                                    (currentState.LoadedAssembly (td.Assembly) |> Option.get)
+                                    currentState
+
+                            newState, info :: acc
+                    )
+
+                // Recurse through the fields, correctly propagating state.
+                let finalState, finalSeenSoFar, fieldsContainRefType =
+                    ((stateAfterFieldResolution, seenSoFarWithInProgress, false), nonStaticFields)
+                    ||> List.fold (fun (currentState, currentSeenSoFar, currentResult) field ->
+                        if currentResult then
+                            (currentState, currentSeenSoFar, true) // Short-circuit
+                        else
+                            let newState, newSeenSoFar, fieldResult =
+                                containsRefType loggerFactory baseClassTypes currentState currentSeenSoFar field
+
+                            (newState, newSeenSoFar, currentResult || fieldResult)
+                    )
+
+                // Mark as completed with the final result before returning.
+                let finalSeenSoFar = finalSeenSoFar.SetItem (td, Completed fieldsContainRefType)
+                finalState, finalSeenSoFar, fieldsContainRefType
+
     let call
+        (loggerFactory : ILoggerFactory)
         (baseClassTypes : BaseClassTypes<_>)
         (methodToCall : WoofWare.PawPrint.MethodInfo<ConcreteTypeHandle, ConcreteTypeHandle, ConcreteTypeHandle>)
         (currentThread : ThreadId)
@@ -68,9 +159,9 @@ module Intrinsics =
                 let rec go (arg : EvalStackValue) =
                     match arg with
                     | EvalStackValue.UserDefinedValueType vt ->
-                        match vt.Fields with
-                        | [ field ] -> go field.ContentsEval
-                        | _ -> failwith $"TODO: %O{vt}"
+                        match CliValueType.TryExactlyOneField vt with
+                        | None -> failwith "TODO"
+                        | Some field -> go (EvalStackValue.ofCliType field.Contents)
                     | EvalStackValue.ManagedPointer ManagedPointerSource.Null -> failwith "TODO: throw NRE"
                     | EvalStackValue.ObjectRef addr
                     | EvalStackValue.ManagedPointer (ManagedPointerSource.Heap addr) -> Some addr
@@ -84,36 +175,68 @@ module Intrinsics =
                     {
                         Name = "m_type"
                         Contents = CliType.ObjectRef arg
-                        Offset = Some 0
+                        Offset = None
+                        Type =
+                            AllConcreteTypes.findExistingConcreteType
+                                state.ConcreteTypes
+                                (baseClassTypes.RuntimeType.Assembly,
+                                 baseClassTypes.RuntimeType.Namespace,
+                                 baseClassTypes.RuntimeType.Name,
+                                 ImmutableArray.Empty)
+                            |> Option.get
                     }
                     |> List.singleton
-                    |> CliValueType.OfFields
+                    |> CliValueType.OfFields Layout.Default
 
                 IlMachineState.pushToEvalStack (CliType.ValueType vt) currentThread state
                 |> IlMachineState.advanceProgramCounter currentThread
 
             Some state
+        | "System.Private.CoreLib", "Type", "get_IsValueType" ->
+            match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
+            | [], ConcreteBool state.ConcreteTypes -> ()
+            | _ -> failwith "bad signature Type.get_IsValueType"
+
+            let this, state = IlMachineState.popEvalStack currentThread state
+
+            let this =
+                match this with
+                | EvalStackValue.ObjectRef ptr ->
+                    IlMachineState.dereferencePointer state (ManagedPointerSource.Heap ptr)
+                | EvalStackValue.ManagedPointer ptr -> IlMachineState.dereferencePointer state ptr
+                | EvalStackValue.Float _
+                | EvalStackValue.Int32 _
+                | EvalStackValue.Int64 _ -> failwith "refusing to dereference literal"
+                | _ -> failwith "TODO"
+            // `this` should be of type Type
+            let ty =
+                match this with
+                | CliType.ValueType cvt ->
+                    match CliValueType.DereferenceField "m_handle" cvt with
+                    | CliType.Numeric (CliNumericType.NativeInt (NativeIntSource.TypeHandlePtr cth)) -> cth
+                    | _ -> failwith ""
+                | _ -> failwith "expected a Type"
+
+            let ty = AllConcreteTypes.lookup ty state.ConcreteTypes |> Option.get
+            let ty = state.LoadedAssembly(ty.Assembly).Value.TypeDefs.[ty.Definition.Get]
+
+            let isValueType =
+                match DumpedAssembly.resolveBaseType baseClassTypes state._LoadedAssemblies ty.Assembly ty.BaseType with
+                | ResolvedBaseType.Enum
+                | ResolvedBaseType.ValueType -> true
+                | ResolvedBaseType.Object
+                | ResolvedBaseType.Delegate -> false
+
+            IlMachineState.pushToEvalStack (CliType.ofBool isValueType) currentThread state
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Some
         | "System.Private.CoreLib", "Unsafe", "AsPointer" ->
             // Method signature: 1 generic parameter, we take a Byref of that parameter, and return a TypeDefn.Pointer(Void)
             let arg, state = IlMachineState.popEvalStack currentThread state
 
             let toPush =
                 match arg with
-                | EvalStackValue.ManagedPointer ptr ->
-                    match ptr with
-                    | ManagedPointerSource.LocalVariable (sourceThread, methodFrame, whichVar) ->
-                        CliRuntimePointer.Managed (
-                            CliRuntimePointerSource.LocalVariable (sourceThread, methodFrame, whichVar)
-                        )
-                    | ManagedPointerSource.Argument (sourceThread, methodFrame, whichVar) ->
-                        CliRuntimePointer.Managed (
-                            CliRuntimePointerSource.Argument (sourceThread, methodFrame, whichVar)
-                        )
-                    | ManagedPointerSource.Heap managedHeapAddress ->
-                        CliRuntimePointer.Managed (CliRuntimePointerSource.Heap managedHeapAddress)
-                    | ManagedPointerSource.Null -> failwith "todo"
-                    | ManagedPointerSource.ArrayIndex _ -> failwith "TODO"
-                    | ManagedPointerSource.Field _ -> failwith "TODO"
+                | EvalStackValue.ManagedPointer ptr -> CliRuntimePointer.Managed ptr
                 | x -> failwith $"TODO: Unsafe.AsPointer(%O{x})"
 
             IlMachineState.pushToEvalStack (CliType.RuntimePointer toPush) currentThread state
@@ -150,6 +273,47 @@ module Intrinsics =
             let result =
                 BitConverter.Int32BitsToSingle arg |> CliNumericType.Float32 |> CliType.Numeric
 
+            state
+            |> IlMachineState.pushToEvalStack result currentThread
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Some
+        | "System.Private.CoreLib", "BitConverter", "DoubleToUInt64Bits" ->
+            match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
+            | [ ConcreteDouble state.ConcreteTypes ], ConcreteUInt64 state.ConcreteTypes -> ()
+            | _ -> failwith "bad signature BitConverter.DoubleToUInt64Bits"
+
+            let arg, state = IlMachineState.popEvalStack currentThread state
+
+            let arg =
+                match arg with
+                | EvalStackValue.Float i -> i
+                | _ -> failwith "$TODO: {arr}"
+
+            let result =
+                BitConverter.DoubleToUInt64Bits arg
+                |> int64<uint64>
+                |> CliNumericType.Int64
+                |> CliType.Numeric
+
+            state
+            |> IlMachineState.pushToEvalStack result currentThread
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Some
+        | "System.Private.CoreLib", "BitConverter", "UInt64BitsToDouble" ->
+            match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
+            | [ ConcreteUInt64 state.ConcreteTypes ], ConcreteDouble state.ConcreteTypes -> ()
+            | _ -> failwith "bad signature BitConverter.DoubleToUInt64Bits"
+
+            let arg, state = IlMachineState.popEvalStack currentThread state
+
+            let arg =
+                match arg with
+                | EvalStackValue.Int64 i -> uint64 i
+                | _ -> failwith "$TODO: {arr}"
+
+            let result =
+                BitConverter.UInt64BitsToDouble arg |> CliNumericType.Float64 |> CliType.Numeric
+
             state
             |> IlMachineState.pushToEvalStack result currentThread
             |> IlMachineState.advanceProgramCounter currentThread
@@ -185,6 +349,44 @@ module Intrinsics =
                 | EvalStackValue.Float f -> BitConverter.DoubleToInt64Bits f |> EvalStackValue.Int64
                 | _ -> failwith "TODO"
 
+            state
+            |> IlMachineState.pushToEvalStack' result currentThread
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Some
+        | "System.Private.CoreLib", "BitConverter", "SingleToUInt32Bits" ->
+            match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
+            | [ ConcreteSingle state.ConcreteTypes ], ConcreteUInt32 state.ConcreteTypes -> ()
+            | _ -> failwith "bad signature BitConverter.SingleToUInt32Bits"
+
+            let arg, state = IlMachineState.popEvalStack currentThread state
+
+            let result =
+                match arg with
+                | EvalStackValue.Float f ->
+                    BitConverter.SingleToUInt32Bits (float32<float> f)
+                    |> int<uint32>
+                    |> EvalStackValue.Int32
+                | _ -> failwith "TODO"
+
+            state
+            |> IlMachineState.pushToEvalStack' result currentThread
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Some
+        | "System.Private.CoreLib", "BitConverter", "UInt32BitsToSingle" ->
+            match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
+            | [ ConcreteUInt32 state.ConcreteTypes ], ConcreteSingle state.ConcreteTypes -> ()
+            | _ -> failwith "bad signature BitConverter.UInt32BitsToSingle"
+
+            let arg, state = IlMachineState.popEvalStack currentThread state
+
+            let result =
+                match arg with
+                | EvalStackValue.Int32 f ->
+                    BitConverter.UInt32BitsToSingle (uint32<int> f)
+                    |> float<float32>
+                    |> EvalStackValue.Float
+                | _ -> failwith "TODO"
+
             state
             |> IlMachineState.pushToEvalStack' result currentThread
             |> IlMachineState.advanceProgramCounter currentThread
@@ -198,7 +400,8 @@ module Intrinsics =
                 let arg1 =
                     match arg1 with
                     | EvalStackValue.ObjectRef h
-                    | EvalStackValue.ManagedPointer (ManagedPointerSource.Heap h) -> h
+                    | EvalStackValue.ManagedPointer (ManagedPointerSource.Heap h) -> Some h
+                    | EvalStackValue.ManagedPointer ManagedPointerSource.Null -> None
                     | EvalStackValue.Int32 _
                     | EvalStackValue.Int64 _
                     | EvalStackValue.Float _ -> failwith $"this isn't a string! {arg1}"
@@ -209,32 +412,38 @@ module Intrinsics =
                 let arg2 =
                     match arg2 with
                     | EvalStackValue.ObjectRef h
-                    | EvalStackValue.ManagedPointer (ManagedPointerSource.Heap h) -> h
+                    | EvalStackValue.ManagedPointer (ManagedPointerSource.Heap h) -> Some h
+                    | EvalStackValue.ManagedPointer ManagedPointerSource.Null -> None
                     | EvalStackValue.Int32 _
                     | EvalStackValue.Int64 _
                     | EvalStackValue.Float _ -> failwith $"this isn't a string! {arg2}"
                     | _ -> failwith $"TODO: %O{arg2}"
 
-                if arg1 = arg2 then
-                    state
-                    |> IlMachineState.pushToEvalStack (CliType.ofBool true) currentThread
-                    |> IlMachineState.advanceProgramCounter currentThread
-                    |> Some
-                else
+                let areEqual =
+                    match arg1, arg2 with
+                    | None, None -> true
+                    | Some _, None
+                    | None, Some _ -> false
+                    | Some arg1, Some arg2 ->
+                        if arg1 = arg2 then
+                            true
+                        else
 
-                let arg1 = ManagedHeap.get arg1 state.ManagedHeap
-                let arg2 = ManagedHeap.get arg2 state.ManagedHeap
+                        let arg1 = ManagedHeap.get arg1 state.ManagedHeap
+                        let arg2 = ManagedHeap.get arg2 state.ManagedHeap
 
-                if
-                    AllocatedNonArrayObject.DereferenceField "_firstChar" arg1
-                    <> AllocatedNonArrayObject.DereferenceField "_firstChar" arg2
-                then
-                    state
-                    |> IlMachineState.pushToEvalStack (CliType.ofBool false) currentThread
-                    |> IlMachineState.advanceProgramCounter currentThread
-                    |> Some
-                else
-                    failwith "TODO"
+                        if
+                            AllocatedNonArrayObject.DereferenceField "_firstChar" arg1
+                            <> AllocatedNonArrayObject.DereferenceField "_firstChar" arg2
+                        then
+                            false
+                        else
+                            failwith "TODO"
+
+                state
+                |> IlMachineState.pushToEvalStack (CliType.ofBool areEqual) currentThread
+                |> IlMachineState.advanceProgramCounter currentThread
+                |> Some
             | _ -> None
         | "System.Private.CoreLib", "Unsafe", "ReadUnaligned" ->
             let ptr, state = IlMachineState.popEvalStack currentThread state
@@ -245,16 +454,10 @@ module Intrinsics =
                     | EvalStackValue.ManagedPointer src -> IlMachineState.dereferencePointer state src
                     | EvalStackValue.NativeInt src -> failwith "TODO"
                     | EvalStackValue.ObjectRef ptr -> failwith "TODO"
-                    | EvalStackValue.UserDefinedValueType {
-                                                              Fields = [ f ]
-                                                          } -> go f.ContentsEval
-                    | EvalStackValue.UserDefinedValueType {
-                                                              Fields = []
-                                                          } -> failwith "unexpected no-fields object"
-                    | EvalStackValue.UserDefinedValueType {
-                                                              Fields = _ :: _ :: _
-                                                          } ->
-                        failwith "TODO: check overlapping fields to see if this is a pointer"
+                    | EvalStackValue.UserDefinedValueType vt ->
+                        match CliValueType.TryExactlyOneField vt with
+                        | None -> failwith "TODO"
+                        | Some field -> go (EvalStackValue.ofCliType field.Contents)
                     | EvalStackValue.Int32 _
                     | EvalStackValue.Int64 _
                     | EvalStackValue.Float _ -> failwith $"this isn't a pointer! {ptr}"
@@ -299,15 +502,46 @@ module Intrinsics =
             | [], ConcreteBool state.ConcreteTypes -> ()
             | _ -> failwith "bad signature for System.Private.CoreLib.RuntimeHelpers.IsReferenceOrContainsReference"
 
-            let generic =
-                AllConcreteTypes.lookup (Seq.exactlyOne methodToCall.Generics) state.ConcreteTypes
+            let arg = Seq.exactlyOne methodToCall.Generics
 
-            let generic =
-                match generic with
-                | None -> failwith "somehow have not already concretised type in IsReferenceOrContainsReferences"
-                | Some generic -> generic
+            let state, result =
+                // Some types appear circular, because they're hardcoded in the runtime. We have to special-case them.
+                match arg with
+                | ConcreteChar state.ConcreteTypes -> state, false
+                | _ ->
 
-            failwith $"TODO: do the thing on %O{generic}"
+                let generic = AllConcreteTypes.lookup arg state.ConcreteTypes
+
+                let generic =
+                    match generic with
+                    | None -> failwith "somehow have not already concretised type in IsReferenceOrContainsReferences"
+                    | Some generic -> generic
+
+                let td =
+                    state.LoadedAssembly generic.Assembly
+                    |> Option.get
+                    |> fun a -> a.TypeDefs.[generic.Definition.Get]
+
+                let baseType =
+                    td.BaseType
+                    |> DumpedAssembly.resolveBaseType baseClassTypes state._LoadedAssemblies generic.Assembly
+
+                match baseType with
+                | ResolvedBaseType.Enum
+                | ResolvedBaseType.ValueType ->
+                    td
+                    |> TypeInfo.mapGeneric (fun (par, _) -> TypeDefn.GenericTypeParameter par.SequenceNumber)
+                    |> containsRefType loggerFactory baseClassTypes state ImmutableDictionary.Empty
+                    |> fun (state, _, result) -> state, result
+                | ResolvedBaseType.Object
+                | ResolvedBaseType.Delegate -> state, true
+
+            let state =
+                state
+                |> IlMachineState.pushToEvalStack (CliType.ofBool result) currentThread
+                |> IlMachineState.advanceProgramCounter currentThread
+
+            Some state
         | "System.Private.CoreLib", "RuntimeHelpers", "InitializeArray" ->
             // https://github.com/dotnet/runtime/blob/9e5e6aa7bc36aeb2a154709a9d1192030c30a2ef/src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.CoreCLR.cs#L18
             match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
@@ -319,11 +553,110 @@ module Intrinsics =
             failwith "TODO: if arg1 contains null handle, throw ArgumentException"
 
             failwith "TODO: array initialization"
+        | "System.Private.CoreLib", "Unsafe", "As" ->
+            // https://github.com/dotnet/runtime/blob/721fdf6dcb032da1f883d30884e222e35e3d3c99/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/Unsafe.cs#L64
+            let inputType, retType =
+                match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
+                | [ input ], ret -> input, ret
+                | _ -> failwith "bad signature Unsafe.As"
+
+            let from, to_ =
+                match Seq.toList methodToCall.Generics with
+                | [ from ; to_ ] -> from, to_
+                | _ -> failwith "bad generics"
+
+            if ConcreteTypeHandle.Byref to_ <> retType then
+                failwith "bad return type"
+
+            if ConcreteTypeHandle.Byref from <> inputType then
+                failwith "bad input type"
+
+            let from =
+                match AllConcreteTypes.lookup from state.ConcreteTypes with
+                | None -> failwith "somehow have not concretised input type"
+                | Some t -> t
+
+            let to_ =
+                match AllConcreteTypes.lookup to_ state.ConcreteTypes with
+                | None -> failwith "somehow have not concretised ret type"
+                | Some t -> t
+
+            let inputAddr, state = IlMachineState.popEvalStack currentThread state
+
+            let ptr =
+                match inputAddr with
+                | EvalStackValue.Int32 _
+                | EvalStackValue.Int64 _
+                | EvalStackValue.Float _ -> failwith "expected pointer type"
+                | EvalStackValue.NativeInt nativeIntSource -> failwith "todo"
+                | EvalStackValue.ManagedPointer src ->
+                    ManagedPointerSource.InterpretedAsType (src, to_)
+                    |> EvalStackValue.ManagedPointer
+                | EvalStackValue.ObjectRef addr ->
+                    ManagedPointerSource.InterpretedAsType (ManagedPointerSource.Heap addr, to_)
+                    |> EvalStackValue.ManagedPointer
+                | EvalStackValue.UserDefinedValueType evalStackValueUserType -> failwith "todo"
+
+            let state =
+                state
+                |> IlMachineState.pushToEvalStack' ptr currentThread
+                |> IlMachineState.advanceProgramCounter currentThread
+
+            Some state
+        | "System.Private.CoreLib", "Unsafe", "SizeOf" ->
+            // https://github.com/dotnet/runtime/blob/721fdf6dcb032da1f883d30884e222e35e3d3c99/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/Unsafe.cs#L51
+            match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
+            | [], ConcreteInt32 state.ConcreteTypes -> ()
+            | _ -> failwith "bad signature Unsafe.SizeOf"
+
+            let ty =
+                match Seq.toList methodToCall.Generics with
+                | [ ty ] -> ty
+                | _ -> failwith "bad generics"
+
+            let zero, state = IlMachineState.cliTypeZeroOfHandle state baseClassTypes ty
+
+            let size = CliType.sizeOf zero
+
+            state
+            |> IlMachineState.pushToEvalStack (CliType.Numeric (CliNumericType.Int32 size)) currentThread
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Some
         | "System.Private.CoreLib", "RuntimeHelpers", "CreateSpan" ->
             // https://github.com/dotnet/runtime/blob/9e5e6aa7bc36aeb2a154709a9d1192030c30a2ef/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.cs#L153
             None
         | "System.Private.CoreLib", "Type", "op_Equality" ->
             // https://github.com/dotnet/runtime/blob/ec11903827fc28847d775ba17e0cd1ff56cfbc2e/src/libraries/System.Private.CoreLib/src/System/Type.cs#L703
             None
+        | "System.Private.CoreLib", "MemoryMarshal", "GetArrayDataReference" ->
+            // https://github.com/dotnet/runtime/blob/d258af50034c192bf7f0a18856bf83d2903d98ae/src/coreclr/System.Private.CoreLib/src/System/Runtime/InteropServices/MemoryMarshal.CoreCLR.cs#L20
+            let generic = Seq.exactlyOne methodToCall.Generics
+
+            match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
+            | [ ConcreteGenericArray state.ConcreteTypes generic ], ConcreteByref t when t = generic -> ()
+            | _ -> failwith "bad signature MemoryMarshal.GetArrayDataReference"
+
+            let arr, state = IlMachineState.popEvalStack currentThread state
+
+            let toPush =
+                match arr with
+                | EvalStackValue.Int32 _
+                | EvalStackValue.Int64 _
+                | EvalStackValue.Float _ -> failwith "expected reference"
+                | EvalStackValue.NativeInt nativeIntSource -> failwith "todo"
+                | EvalStackValue.ObjectRef addr
+                | EvalStackValue.ManagedPointer (ManagedPointerSource.Heap addr) ->
+                    if not (state.ManagedHeap.Arrays.ContainsKey addr) then
+                        failwith "array not found"
+
+                    EvalStackValue.ManagedPointer (ManagedPointerSource.ArrayIndex (addr, 0))
+                | EvalStackValue.UserDefinedValueType evalStackValueUserType -> failwith "todo"
+                | EvalStackValue.ManagedPointer ManagedPointerSource.Null -> failwith "TODO: raise NRE"
+                | EvalStackValue.ManagedPointer _ -> failwith "todo"
+
+            state
+            |> IlMachineState.pushToEvalStack' toPush currentThread
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Some
         | a, b, c -> failwith $"TODO: implement JIT intrinsic {a}.{b}.{c}"
         |> Option.map (fun s -> s.WithThreadSwitchedToAssembly callerAssy currentThread |> fst)

WoofWare.PawPrint/ManagedHeap.fs

@@ -8,36 +8,18 @@ type SyncBlock =
 
 type AllocatedNonArrayObject =
     {
-        Fields : CliField list
+        // TODO: this is a slightly odd domain; the same type for value types as class types!
+        Contents : CliValueType
         ConcreteType : ConcreteTypeHandle
         SyncBlock : SyncBlock
     }
 
     static member DereferenceField (name : string) (f : AllocatedNonArrayObject) : CliType =
-        // TODO: this is wrong, it doesn't account for overlapping fields
-        f.Fields |> List.find (fun f -> f.Name = name) |> _.Contents
+        CliValueType.DereferenceField name f.Contents
 
     static member SetField (name : string) (v : CliType) (f : AllocatedNonArrayObject) : AllocatedNonArrayObject =
-        // TODO: this is wrong, it doesn't account for overlapping fields
-        let contents =
-            {
-                Name = name
-                Contents = v
-                Offset = None
-            }
-
         { f with
-            Fields =
-                f.Fields
-                |> List.replaceWhere (fun f ->
-                    if f.Name = name then
-                        Some
-                            { contents with
-                                Offset = f.Offset
-                            }
-                    else
-                        None
-                )
+            Contents = CliValueType.WithFieldSet name v f.Contents
         }
 
 type AllocatedArray =

WoofWare.PawPrint/NullaryIlOp.fs

@@ -1,5 +1,6 @@
 namespace WoofWare.PawPrint
 
+open System
 open Microsoft.Extensions.Logging
 
 [<RequireQualifiedAccess>]
@@ -52,7 +53,7 @@ module NullaryIlOp =
             | EvalStackValue.NativeInt nativeIntSource ->
                 failwith $"TODO: Native int pointer dereferencing not implemented for {targetType}"
             | EvalStackValue.ObjectRef managedHeapAddress ->
-                failwith "TODO: Object reference dereferencing not implemented"
+                IlMachineState.dereferencePointer state (ManagedPointerSource.Heap managedHeapAddress)
             | other -> failwith $"Unexpected eval stack value for Ldind operation: {other}"
 
         let loadedValue = loadedValue |> EvalStackValue.ofCliType
@@ -81,53 +82,39 @@ module NullaryIlOp =
         | EvalStackValue.ManagedPointer src ->
             match src with
             | ManagedPointerSource.Null -> failwith "TODO: throw NullReferenceException"
+            | ManagedPointerSource.InterpretedAsType (src, ty) -> failwith "TODO"
             | ManagedPointerSource.Argument (sourceThread, methodFrame, whichVar) ->
                 failwith "unexpected - can we really write to an argument?"
             | ManagedPointerSource.LocalVariable (sourceThread, methodFrame, whichVar) ->
-                { state with
-                    ThreadState =
-                        state.ThreadState
-                        |> Map.change
-                            sourceThread
-                            (fun state ->
-                                match state with
-                                | None -> failwith "tried to store in local variables of nonexistent stack frame"
-                                | Some state ->
-                                    let frame = state.MethodStates.[methodFrame]
-
-                                    let frame =
-                                        { frame with
-                                            LocalVariables =
-                                                frame.LocalVariables.SetItem (
-                                                    int<uint16> whichVar,
-                                                    EvalStackValue.toCliTypeCoerced varType valueToStore
-                                                )
-                                        }
-
-                                    { state with
-                                        MethodStates = state.MethodStates.SetItem (methodFrame, frame)
-                                    }
-                                    |> Some
-                            )
-                }
+                state
+                |> IlMachineState.setLocalVariable
+                    sourceThread
+                    methodFrame
+                    whichVar
+                    (EvalStackValue.toCliTypeCoerced varType valueToStore)
             | ManagedPointerSource.Heap managedHeapAddress -> failwith "todo"
             | ManagedPointerSource.ArrayIndex _ -> failwith "todo"
-            | ManagedPointerSource.Field (managedPointerSource, fieldName) -> failwith "todo"
+            | ManagedPointerSource.Field (managedPointerSource, fieldName) ->
+                state
+                |> IlMachineState.setFieldValue
+                    managedPointerSource
+                    (EvalStackValue.toCliTypeCoerced varType valueToStore)
+                    fieldName
         | EvalStackValue.ObjectRef managedHeapAddress -> failwith "todo"
 
-    let internal ldElem
-        (targetCliTypeZero : CliType)
+    let internal getArrayElt
         (index : EvalStackValue)
         (arr : EvalStackValue)
         (currentThread : ThreadId)
         (state : IlMachineState)
-        : ExecutionResult
+        : CliType
         =
         let index =
             match index with
             | EvalStackValue.NativeInt src ->
                 match src with
                 | NativeIntSource.FunctionPointer _
+                | NativeIntSource.FieldHandlePtr _
                 | NativeIntSource.TypeHandlePtr _
                 | NativeIntSource.ManagedPointer _ -> failwith "Refusing to treat a pointer as an array index"
                 | NativeIntSource.Verbatim i -> i |> int32
@@ -141,14 +128,7 @@ module NullaryIlOp =
             | EvalStackValue.ManagedPointer ManagedPointerSource.Null -> failwith "TODO: throw NRE"
             | _ -> failwith $"Invalid array: %O{arr}"
 
-        let value = IlMachineState.getArrayValue arrAddr index state
-
-        let state =
-            state
-            |> IlMachineState.pushToEvalStack value currentThread
-            |> IlMachineState.advanceProgramCounter currentThread
-
-        ExecutionResult.Stepped (state, WhatWeDid.Executed)
+        IlMachineState.getArrayValue arrAddr index state
 
     let internal stElem
         (targetCliTypeZero : CliType)
@@ -164,6 +144,7 @@ module NullaryIlOp =
             | EvalStackValue.NativeInt src ->
                 match src with
                 | NativeIntSource.FunctionPointer _
+                | NativeIntSource.FieldHandlePtr _
                 | NativeIntSource.TypeHandlePtr _
                 | NativeIntSource.ManagedPointer _ -> failwith "Refusing to treat a pointer as an array index"
                 | NativeIntSource.Verbatim i -> i |> int32
@@ -430,7 +411,7 @@ module NullaryIlOp =
         | Sub ->
             let val2, state = IlMachineState.popEvalStack currentThread state
             let val1, state = IlMachineState.popEvalStack currentThread state
-            let result = BinaryArithmetic.execute ArithmeticOperation.sub val1 val2
+            let result = BinaryArithmetic.execute ArithmeticOperation.sub state val1 val2
 
             state
             |> IlMachineState.pushToEvalStack' result currentThread
@@ -440,30 +421,84 @@ module NullaryIlOp =
         | Sub_ovf -> failwith "TODO: Sub_ovf unimplemented"
         | Sub_ovf_un -> failwith "TODO: Sub_ovf_un unimplemented"
         | Add ->
-            let val1, state = IlMachineState.popEvalStack currentThread state
             let val2, state = IlMachineState.popEvalStack currentThread state
-            let result = BinaryArithmetic.execute ArithmeticOperation.add val1 val2
+            let val1, state = IlMachineState.popEvalStack currentThread state
+            let result = BinaryArithmetic.execute ArithmeticOperation.add state val1 val2
 
             state
             |> IlMachineState.pushToEvalStack' result currentThread
             |> IlMachineState.advanceProgramCounter currentThread
             |> Tuple.withRight WhatWeDid.Executed
             |> ExecutionResult.Stepped
-        | Add_ovf -> failwith "TODO: Add_ovf unimplemented"
+        | Add_ovf ->
+            let val2, state = IlMachineState.popEvalStack currentThread state
+            let val1, state = IlMachineState.popEvalStack currentThread state
+
+            let result =
+                try
+                    BinaryArithmetic.execute ArithmeticOperation.addOvf state val1 val2 |> Ok
+                with :? OverflowException as e ->
+                    Error e
+
+            let state =
+                match result with
+                | Ok result -> state |> IlMachineState.pushToEvalStack' result currentThread
+                | Error excToThrow -> failwith "TODO: throw OverflowException"
+
+            state
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Tuple.withRight WhatWeDid.Executed
+            |> ExecutionResult.Stepped
         | Add_ovf_un -> failwith "TODO: Add_ovf_un unimplemented"
         | Mul ->
-            let val1, state = IlMachineState.popEvalStack currentThread state
             let val2, state = IlMachineState.popEvalStack currentThread state
-            let result = BinaryArithmetic.execute ArithmeticOperation.mul val1 val2
+            let val1, state = IlMachineState.popEvalStack currentThread state
+            let result = BinaryArithmetic.execute ArithmeticOperation.mul state val1 val2
 
             state
             |> IlMachineState.pushToEvalStack' result currentThread
             |> IlMachineState.advanceProgramCounter currentThread
             |> Tuple.withRight WhatWeDid.Executed
             |> ExecutionResult.Stepped
-        | Mul_ovf -> failwith "TODO: Mul_ovf unimplemented"
+        | Mul_ovf ->
+            let val2, state = IlMachineState.popEvalStack currentThread state
+            let val1, state = IlMachineState.popEvalStack currentThread state
+
+            let result =
+                try
+                    BinaryArithmetic.execute ArithmeticOperation.mulOvf state val1 val2 |> Ok
+                with :? OverflowException as e ->
+                    Error e
+
+            let state =
+                match result with
+                | Ok result -> state |> IlMachineState.pushToEvalStack' result currentThread
+                | Error excToThrow -> failwith "TODO: throw OverflowException"
+
+            state
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Tuple.withRight WhatWeDid.Executed
+            |> ExecutionResult.Stepped
         | Mul_ovf_un -> failwith "TODO: Mul_ovf_un unimplemented"
-        | Div -> failwith "TODO: Div unimplemented"
+        | Div ->
+            let val2, state = IlMachineState.popEvalStack currentThread state
+            let val1, state = IlMachineState.popEvalStack currentThread state
+
+            let result =
+                try
+                    BinaryArithmetic.execute ArithmeticOperation.div state val1 val2 |> Ok
+                with :? OverflowException as e ->
+                    Error e
+
+            let state =
+                match result with
+                | Ok result -> state |> IlMachineState.pushToEvalStack' result currentThread
+                | Error excToThrow -> failwith "TODO: throw OverflowException"
+
+            state
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Tuple.withRight WhatWeDid.Executed
+            |> ExecutionResult.Stepped
         | Div_un -> failwith "TODO: Div_un unimplemented"
         | Shr ->
             let shift, state = IlMachineState.popEvalStack currentThread state
@@ -490,7 +525,33 @@ module NullaryIlOp =
                 |> IlMachineState.advanceProgramCounter currentThread
 
             (state, WhatWeDid.Executed) |> ExecutionResult.Stepped
-        | Shr_un -> failwith "TODO: Shr_un unimplemented"
+        | Shr_un ->
+            let shift, state = IlMachineState.popEvalStack currentThread state
+            let number, state = IlMachineState.popEvalStack currentThread state
+
+            let shift =
+                match shift with
+                | EvalStackValue.Int32 i -> i
+                | EvalStackValue.NativeInt (NativeIntSource.Verbatim i) -> int<int64> i
+                | _ -> failwith $"Not allowed shift of {shift}"
+
+            let result =
+                // See table III.6
+                match number with
+                | EvalStackValue.Int32 i -> uint32<int> i >>> shift |> int32<uint32> |> EvalStackValue.Int32
+                | EvalStackValue.Int64 i -> uint64<int64> i >>> shift |> int64<uint64> |> EvalStackValue.Int64
+                | EvalStackValue.NativeInt (NativeIntSource.Verbatim i) ->
+                    (uint64<int64> i >>> shift |> int64<uint64>)
+                    |> NativeIntSource.Verbatim
+                    |> EvalStackValue.NativeInt
+                | _ -> failwith $"Not allowed to shift {number}"
+
+            let state =
+                state
+                |> IlMachineState.pushToEvalStack' result currentThread
+                |> IlMachineState.advanceProgramCounter currentThread
+
+            (state, WhatWeDid.Executed) |> ExecutionResult.Stepped
         | Shl ->
             let shift, state = IlMachineState.popEvalStack currentThread state
             let number, state = IlMachineState.popEvalStack currentThread state
@@ -578,7 +639,37 @@ module NullaryIlOp =
                 |> IlMachineState.advanceProgramCounter currentThread
 
             (state, WhatWeDid.Executed) |> ExecutionResult.Stepped
-        | Xor -> failwith "TODO: Xor unimplemented"
+        | Xor ->
+            let v2, state = IlMachineState.popEvalStack currentThread state
+            let v1, state = IlMachineState.popEvalStack currentThread state
+
+            let result =
+                match v1, v2 with
+                | EvalStackValue.Int32 v1, EvalStackValue.Int32 v2 -> v1 ^^^ v2 |> EvalStackValue.Int32
+                | EvalStackValue.Int32 v1, EvalStackValue.NativeInt (NativeIntSource.Verbatim v2) ->
+                    int64<int32> v1 ^^^ v2 |> NativeIntSource.Verbatim |> EvalStackValue.NativeInt
+                | EvalStackValue.Int32 _, EvalStackValue.NativeInt _ ->
+                    failwith $"can't do binary operation on non-verbatim native int {v2}"
+                | EvalStackValue.Int64 v1, EvalStackValue.Int64 v2 -> v1 ^^^ v2 |> EvalStackValue.Int64
+                | EvalStackValue.NativeInt (NativeIntSource.Verbatim v1), EvalStackValue.Int32 v2 ->
+                    v1 ^^^ int64<int32> v2 |> NativeIntSource.Verbatim |> EvalStackValue.NativeInt
+                | EvalStackValue.NativeInt _, EvalStackValue.Int32 _ ->
+                    failwith $"can't do binary operation on non-verbatim native int {v1}"
+                | EvalStackValue.NativeInt (NativeIntSource.Verbatim v1),
+                  EvalStackValue.NativeInt (NativeIntSource.Verbatim v2) ->
+                    v1 ^^^ v2 |> NativeIntSource.Verbatim |> EvalStackValue.NativeInt
+                | EvalStackValue.NativeInt (NativeIntSource.Verbatim _), EvalStackValue.NativeInt _ ->
+                    failwith $"can't do binary operation on non-verbatim native int {v2}"
+                | EvalStackValue.NativeInt _, EvalStackValue.NativeInt (NativeIntSource.Verbatim _) ->
+                    failwith $"can't do binary operation on non-verbatim native int {v1}"
+                | _, _ -> failwith $"refusing to do binary operation on {v1} and {v2}"
+
+            let state =
+                state
+                |> IlMachineState.pushToEvalStack' result currentThread
+                |> IlMachineState.advanceProgramCounter currentThread
+
+            (state, WhatWeDid.Executed) |> ExecutionResult.Stepped
         | Conv_I ->
             let popped, state = IlMachineState.popEvalStack currentThread state
             let converted = EvalStackValue.toNativeInt popped
@@ -649,7 +740,20 @@ module NullaryIlOp =
             let state = state |> IlMachineState.advanceProgramCounter currentThread
 
             (state, WhatWeDid.Executed) |> ExecutionResult.Stepped
-        | Conv_U1 -> failwith "TODO: Conv_U1 unimplemented"
+        | Conv_U1 ->
+            let popped, state = IlMachineState.popEvalStack currentThread state
+            let converted = EvalStackValue.convToUInt8 popped
+
+            let state =
+                match converted with
+                | None -> failwith "TODO: Conv_U8 conversion failure unimplemented"
+                | Some conv ->
+                    state
+                    |> IlMachineState.pushToEvalStack' (EvalStackValue.Int32 conv) currentThread
+
+            let state = state |> IlMachineState.advanceProgramCounter currentThread
+
+            (state, WhatWeDid.Executed) |> ExecutionResult.Stepped
         | Conv_U2 -> failwith "TODO: Conv_U2 unimplemented"
         | Conv_U4 -> failwith "TODO: Conv_U4 unimplemented"
         | Conv_U8 ->
@@ -857,7 +961,16 @@ module NullaryIlOp =
         | Ldind_u8 -> failwith "TODO: Ldind_u8 unimplemented"
         | Ldind_r4 -> executeLdind LdindTargetType.LdindR4 currentThread state
         | Ldind_r8 -> executeLdind LdindTargetType.LdindR8 currentThread state
-        | Rem -> failwith "TODO: Rem unimplemented"
+        | Rem ->
+            let val2, state = IlMachineState.popEvalStack currentThread state
+            let val1, state = IlMachineState.popEvalStack currentThread state
+            let result = BinaryArithmetic.execute ArithmeticOperation.rem state val1 val2
+
+            state
+            |> IlMachineState.pushToEvalStack' result currentThread
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Tuple.withRight WhatWeDid.Executed
+            |> ExecutionResult.Stepped
         | Rem_un -> failwith "TODO: Rem_un unimplemented"
         | Volatile -> failwith "TODO: Volatile unimplemented"
         | Tail -> failwith "TODO: Tail unimplemented"
@@ -874,7 +987,22 @@ module NullaryIlOp =
         | Conv_ovf_i -> failwith "TODO: Conv_ovf_i unimplemented"
         | Conv_ovf_u -> failwith "TODO: Conv_ovf_u unimplemented"
         | Neg -> failwith "TODO: Neg unimplemented"
-        | Not -> failwith "TODO: Not unimplemented"
+        | Not ->
+            let val1, state = IlMachineState.popEvalStack currentThread state
+
+            let result =
+                match val1 with
+                | EvalStackValue.Int32 i -> ~~~i |> EvalStackValue.Int32
+                | EvalStackValue.Int64 i -> ~~~i |> EvalStackValue.Int64
+                | EvalStackValue.ManagedPointer _
+                | EvalStackValue.ObjectRef _ -> failwith "refusing to negate a pointer"
+                | _ -> failwith "TODO"
+
+            state
+            |> IlMachineState.pushToEvalStack' result currentThread
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Tuple.withRight WhatWeDid.Executed
+            |> ExecutionResult.Stepped
         | Ldind_ref ->
             let addr, state = IlMachineState.popEvalStack currentThread state
 
@@ -885,6 +1013,7 @@ module NullaryIlOp =
 
             let state =
                 match referenced with
+                | CliType.RuntimePointer (CliRuntimePointer.Managed _)
                 | CliType.ObjectRef _ -> IlMachineState.pushToEvalStack referenced currentThread state
                 | _ -> failwith $"Unexpected non-reference {referenced}"
                 |> IlMachineState.advanceProgramCounter currentThread
@@ -909,19 +1038,91 @@ module NullaryIlOp =
                             (EvalStackValue.toCliTypeCoerced (CliType.ObjectRef None) value)
                             index
                     | ManagedPointerSource.Field _ -> failwith "TODO"
+                    | ManagedPointerSource.InterpretedAsType (src, ty) -> failwith "TODO"
                 | addr -> failwith $"TODO: {addr}"
 
             let state = state |> IlMachineState.advanceProgramCounter currentThread
 
             (state, WhatWeDid.Executed) |> ExecutionResult.Stepped
-        | Ldelem_i -> failwith "TODO: Ldelem_i unimplemented"
-        | Ldelem_i1 -> failwith "TODO: Ldelem_i1 unimplemented"
+        | Ldelem_i ->
+            let index, state = IlMachineState.popEvalStack currentThread state
+            let arr, state = IlMachineState.popEvalStack currentThread state
+
+            let value = getArrayElt index arr currentThread state
+
+            match value with
+            | CliType.Numeric (CliNumericType.NativeInt _) -> ()
+            | _ -> failwith "expected native int in Ldelem.i"
+
+            let state =
+                state
+                |> IlMachineState.pushToEvalStack value currentThread
+                |> IlMachineState.advanceProgramCounter currentThread
+
+            ExecutionResult.Stepped (state, WhatWeDid.Executed)
+        | Ldelem_i1 ->
+            let index, state = IlMachineState.popEvalStack currentThread state
+            let arr, state = IlMachineState.popEvalStack currentThread state
+
+            let value = getArrayElt index arr currentThread state
+
+            failwith "TODO: we got back an int8; turn it into int32"
+
+            let state =
+                state
+                |> IlMachineState.pushToEvalStack value currentThread
+                |> IlMachineState.advanceProgramCounter currentThread
+
+            ExecutionResult.Stepped (state, WhatWeDid.Executed)
         | Ldelem_u1 -> failwith "TODO: Ldelem_u1 unimplemented"
-        | Ldelem_i2 -> failwith "TODO: Ldelem_i2 unimplemented"
+        | Ldelem_i2 ->
+            let index, state = IlMachineState.popEvalStack currentThread state
+            let arr, state = IlMachineState.popEvalStack currentThread state
+
+            let value = getArrayElt index arr currentThread state
+
+            failwith "TODO: we got back an int16; turn it into int32"
+
+            let state =
+                state
+                |> IlMachineState.pushToEvalStack value currentThread
+                |> IlMachineState.advanceProgramCounter currentThread
+
+            ExecutionResult.Stepped (state, WhatWeDid.Executed)
         | Ldelem_u2 -> failwith "TODO: Ldelem_u2 unimplemented"
-        | Ldelem_i4 -> failwith "TODO: Ldelem_i4 unimplemented"
+        | Ldelem_i4 ->
+            let index, state = IlMachineState.popEvalStack currentThread state
+            let arr, state = IlMachineState.popEvalStack currentThread state
+
+            let value = getArrayElt index arr currentThread state
+
+            match value with
+            | CliType.Numeric (CliNumericType.Int32 _) -> ()
+            | _ -> failwith "expected int32 in Ldelem.i4"
+
+            let state =
+                state
+                |> IlMachineState.pushToEvalStack value currentThread
+                |> IlMachineState.advanceProgramCounter currentThread
+
+            ExecutionResult.Stepped (state, WhatWeDid.Executed)
         | Ldelem_u4 -> failwith "TODO: Ldelem_u4 unimplemented"
-        | Ldelem_i8 -> failwith "TODO: Ldelem_i8 unimplemented"
+        | Ldelem_i8 ->
+            let index, state = IlMachineState.popEvalStack currentThread state
+            let arr, state = IlMachineState.popEvalStack currentThread state
+
+            let value = getArrayElt index arr currentThread state
+
+            match value with
+            | CliType.Numeric (CliNumericType.Int64 _) -> ()
+            | _ -> failwith "expected int64 in Ldelem.i8"
+
+            let state =
+                state
+                |> IlMachineState.pushToEvalStack value currentThread
+                |> IlMachineState.advanceProgramCounter currentThread
+
+            ExecutionResult.Stepped (state, WhatWeDid.Executed)
         | Ldelem_u8 -> failwith "TODO: Ldelem_u8 unimplemented"
         | Ldelem_r4 -> failwith "TODO: Ldelem_r4 unimplemented"
         | Ldelem_r8 -> failwith "TODO: Ldelem_r8 unimplemented"
@@ -929,7 +1130,19 @@ module NullaryIlOp =
             let index, state = IlMachineState.popEvalStack currentThread state
             let arr, state = IlMachineState.popEvalStack currentThread state
 
-            ldElem (CliType.ObjectRef None) index arr currentThread state
+            let value = getArrayElt index arr currentThread state
+
+            match value with
+            | CliType.ObjectRef _
+            | CliType.RuntimePointer _ -> ()
+            | _ -> failwith "expected object reference in Ldelem.ref"
+
+            let state =
+                state
+                |> IlMachineState.pushToEvalStack value currentThread
+                |> IlMachineState.advanceProgramCounter currentThread
+
+            ExecutionResult.Stepped (state, WhatWeDid.Executed)
         | Stelem_i ->
             let value, state = IlMachineState.popEvalStack currentThread state
             let index, state = IlMachineState.popEvalStack currentThread state

WoofWare.PawPrint/Program.fs

@@ -10,6 +10,7 @@ open Microsoft.Extensions.Logging
 module Program =
     /// Returns the pointer to the resulting array on the heap.
     let allocateArgs
+        (loggerFactory : ILoggerFactory)
         (args : string list)
         (corelib : BaseClassTypes<DumpedAssembly>)
         (state : IlMachineState)
@@ -18,6 +19,7 @@ module Program =
         let state, stringType =
             DumpedAssembly.typeInfoToTypeDefn' corelib state._LoadedAssemblies corelib.String
             |> IlMachineState.concretizeType
+                loggerFactory
                 corelib
                 state
                 corelib.Corelib.Name
@@ -285,7 +287,7 @@ module Program =
         let arrayAllocation, state =
             match mainMethodFromMetadata.Signature.ParameterTypes |> Seq.toList with
             | [ TypeDefn.OneDimensionalArrayLowerBoundZero (TypeDefn.PrimitiveType PrimitiveType.String) ] ->
-                allocateArgs argv baseClassTypes state
+                allocateArgs loggerFactory argv baseClassTypes state
             | _ -> failwith "Main method must take an array of strings; other signatures not yet implemented"
 
         match mainMethodFromMetadata.Signature.ReturnType with
@@ -300,6 +302,11 @@ module Program =
 
         logger.LogInformation "Main method class now initialised"
 
+        let state =
+            { state with
+                ConcreteTypes = Corelib.concretizeAll state._LoadedAssemblies baseClassTypes state.ConcreteTypes
+            }
+
         // Now that BCL initialisation has taken place and the user-code classes are constructed,
         // overwrite the main thread completely using the already-concretized method.
         let methodState =

WoofWare.PawPrint/TypeHandleRegistry.fs

@@ -1,5 +1,7 @@
 namespace WoofWare.PawPrint
 
+open System.Collections.Immutable
+
 type TypeHandleRegistry =
     private
         {
@@ -17,8 +19,10 @@ module TypeHandleRegistry =
 
     /// Returns an allocated System.RuntimeType as well.
     let getOrAllocate
+        (allConcreteTypes : AllConcreteTypes)
+        (corelib : BaseClassTypes<DumpedAssembly>)
         (allocState : 'allocState)
-        (allocate : CliField list -> 'allocState -> ManagedHeapAddress * 'allocState)
+        (allocate : CliValueType -> 'allocState -> ManagedHeapAddress * 'allocState)
         (def : ConcreteTypeHandle)
         (reg : TypeHandleRegistry)
         : ManagedHeapAddress * TypeHandleRegistry * 'allocState
@@ -38,17 +42,40 @@ module TypeHandleRegistry =
                     Name = "m_keepalive"
                     Contents = CliType.ObjectRef None
                     Offset = None
+                    Type =
+                        AllConcreteTypes.findExistingConcreteType
+                            allConcreteTypes
+                            (corelib.Object.Assembly,
+                             corelib.Object.Namespace,
+                             corelib.Object.Name,
+                             ImmutableArray.Empty)
+                        |> Option.get
                 }
-                // TODO: this is actually a System.IntPtr https://github.com/dotnet/runtime/blob/ec11903827fc28847d775ba17e0cd1ff56cfbc2e/src/coreclr/nativeaot/Runtime.Base/src/System/Primitives.cs#L339
                 {
                     Name = "m_cache"
                     Contents = CliType.Numeric (CliNumericType.NativeInt (NativeIntSource.Verbatim 0L))
                     Offset = None
+                    Type =
+                        AllConcreteTypes.findExistingConcreteType
+                            allConcreteTypes
+                            (corelib.IntPtr.Assembly,
+                             corelib.IntPtr.Namespace,
+                             corelib.IntPtr.Name,
+                             ImmutableArray.Empty)
+                        |> Option.get
                 }
                 {
                     Name = "m_handle"
                     Contents = CliType.Numeric (CliNumericType.NativeInt (NativeIntSource.TypeHandlePtr def))
                     Offset = None
+                    Type =
+                        AllConcreteTypes.findExistingConcreteType
+                            allConcreteTypes
+                            (corelib.IntPtr.Assembly,
+                             corelib.IntPtr.Namespace,
+                             corelib.IntPtr.Name,
+                             ImmutableArray.Empty)
+                        |> Option.get
                 }
                 // This is the const -1, apparently?!
                 // https://github.com/dotnet/runtime/blob/f0168ee80ba9aca18a7e7140b2bb436defda623c/src/coreclr/System.Private.CoreLib/src/System/RuntimeType.CoreCLR.cs#L2496
@@ -56,8 +83,14 @@ module TypeHandleRegistry =
                     Name = "GenericParameterCountAny"
                     Contents = CliType.Numeric (CliNumericType.Int32 -1)
                     Offset = None
+                    Type =
+                        AllConcreteTypes.findExistingConcreteType
+                            allConcreteTypes
+                            (corelib.Int32.Assembly, corelib.Int32.Namespace, corelib.Int32.Name, ImmutableArray.Empty)
+                        |> Option.get
                 }
             ]
+            |> CliValueType.OfFields Layout.Default
 
         let alloc, state = allocate fields allocState
 

WoofWare.PawPrint/UnaryMetadataIlOp.fs

@@ -28,6 +28,24 @@ module internal UnaryMetadataIlOp =
                 | MetadataToken.MethodSpecification h ->
                     let spec = activeAssy.MethodSpecs.[h]
 
+                    let state, methodGenerics =
+                        ((state, []), spec.Signature)
+                        ||> Seq.fold (fun (state, acc) typeDefn ->
+                            let state, concreteType =
+                                IlMachineState.concretizeType
+                                    loggerFactory
+                                    baseClassTypes
+                                    state
+                                    (state.ActiveAssembly thread).Name
+                                    currentMethod.DeclaringType.Generics
+                                    currentMethod.Generics
+                                    typeDefn
+
+                            state, concreteType :: acc
+                        )
+
+                    let methodGenerics = List.rev methodGenerics |> ImmutableArray.CreateRange
+
                     match spec.Method with
                     | MetadataToken.MethodDef token ->
                         let method =
@@ -44,6 +62,7 @@ module internal UnaryMetadataIlOp =
                                 baseClassTypes
                                 thread
                                 (state.ActiveAssembly thread)
+                                methodGenerics
                                 ref
                                 state
 
@@ -58,6 +77,7 @@ module internal UnaryMetadataIlOp =
                             baseClassTypes
                             thread
                             (state.ActiveAssembly thread)
+                            currentMethod.DeclaringType.Generics
                             h
                             state
 
@@ -114,6 +134,24 @@ module internal UnaryMetadataIlOp =
                 | MetadataToken.MethodSpecification h ->
                     let spec = activeAssy.MethodSpecs.[h]
 
+                    let state, methodGenerics =
+                        ((state, []), spec.Signature)
+                        ||> Seq.fold (fun (state, acc) typeDefn ->
+                            let state, concreteType =
+                                IlMachineState.concretizeType
+                                    loggerFactory
+                                    baseClassTypes
+                                    state
+                                    (state.ActiveAssembly thread).Name
+                                    currentMethod.DeclaringType.Generics
+                                    ImmutableArray.Empty
+                                    typeDefn
+
+                            state, concreteType :: acc
+                        )
+
+                    let methodGenerics = List.rev methodGenerics |> ImmutableArray.CreateRange
+
                     match spec.Method with
                     | MetadataToken.MethodDef token ->
                         let method =
@@ -128,6 +166,7 @@ module internal UnaryMetadataIlOp =
                                 baseClassTypes
                                 thread
                                 (state.ActiveAssembly thread)
+                                methodGenerics
                                 ref
                                 state
 
@@ -142,6 +181,7 @@ module internal UnaryMetadataIlOp =
                             baseClassTypes
                             thread
                             (state.ActiveAssembly thread)
+                            ImmutableArray.Empty
                             h
                             state
 
@@ -203,6 +243,7 @@ module internal UnaryMetadataIlOp =
                             baseClassTypes
                             thread
                             (state.ActiveAssembly thread)
+                            ImmutableArray.Empty
                             mr
                             state
 
@@ -255,7 +296,7 @@ module internal UnaryMetadataIlOp =
                 ((state, []), instanceFields)
                 ||> List.fold (fun (state, zeros) field ->
                     // TODO: generics
-                    let state, zero =
+                    let state, zero, concreteType =
                         IlMachineState.cliTypeZeroOf
                             loggerFactory
                             baseClassTypes
@@ -270,12 +311,13 @@ module internal UnaryMetadataIlOp =
                             Name = field.Name
                             Contents = zero
                             Offset = field.Offset
+                            Type = concreteType
                         }
 
                     state, field :: zeros
                 )
 
-            let fields = List.rev fieldZeros
+            let fields = List.rev fieldZeros |> CliValueType.OfFields ctorType.Layout
 
             // Note: this is a bit unorthodox for value types, which *aren't* heap-allocated.
             // We'll perform their construction on the heap, though, to keep the interface
@@ -354,7 +396,7 @@ module internal UnaryMetadataIlOp =
                         ref
                 | x -> failwith $"TODO: Newarr element type resolution unimplemented for {x}"
 
-            let state, zeroOfType =
+            let state, zeroOfType, concreteTypeHandle =
                 IlMachineState.cliTypeZeroOf
                     loggerFactory
                     baseClassTypes
@@ -374,7 +416,55 @@ module internal UnaryMetadataIlOp =
                 |> IlMachineState.advanceProgramCounter thread
 
             state, WhatWeDid.Executed
-        | Box -> failwith "TODO: Box unimplemented"
+        | Box ->
+            let state, ty, assy =
+                match metadataToken with
+                | MetadataToken.TypeDefinition h ->
+                    let state, ty = IlMachineState.lookupTypeDefn baseClassTypes state activeAssy h
+                    state, ty, activeAssy
+                | MetadataToken.TypeReference ref ->
+                    IlMachineState.lookupTypeRef
+                        loggerFactory
+                        baseClassTypes
+                        state
+                        activeAssy
+                        currentMethod.DeclaringType.Generics
+                        ref
+                | MetadataToken.TypeSpecification spec -> state, activeAssy.TypeSpecs.[spec].Signature, activeAssy
+                | _ -> failwith $"unexpected token {metadataToken} in Box"
+
+            let state, typeHandle =
+                IlMachineState.concretizeType
+                    loggerFactory
+                    baseClassTypes
+                    state
+                    assy.Name
+                    currentMethod.DeclaringType.Generics
+                    currentMethod.Generics
+                    ty
+
+            let toBox, state = state |> IlMachineState.popEvalStack thread
+
+            let targetType =
+                AllConcreteTypes.lookup typeHandle state.ConcreteTypes |> Option.get
+
+            let defn =
+                state._LoadedAssemblies.[targetType.Assembly.FullName].TypeDefs.[targetType.Definition.Get]
+
+            let baseType =
+                DumpedAssembly.resolveBaseType baseClassTypes state._LoadedAssemblies targetType.Assembly defn.BaseType
+
+            let toPush =
+                match baseType with
+                | ResolvedBaseType.Enum
+                | ResolvedBaseType.ValueType -> failwith "TODO: implement Box"
+                | ResolvedBaseType.Object
+                | ResolvedBaseType.Delegate -> toBox
+
+            state
+            |> IlMachineState.pushToEvalStack' toPush thread
+            |> IlMachineState.advanceProgramCounter thread
+            |> Tuple.withRight WhatWeDid.Executed
         | Ldelema ->
             let index, state = IlMachineState.popEvalStack thread state
             let arr, state = IlMachineState.popEvalStack thread state
@@ -436,6 +526,7 @@ module internal UnaryMetadataIlOp =
 
             let state, targetConcreteType =
                 IlMachineState.concretizeType
+                    loggerFactory
                     baseClassTypes
                     state
                     activeAssy.Name
@@ -456,7 +547,8 @@ module internal UnaryMetadataIlOp =
                         if v.ConcreteType = targetConcreteType then
                             actualObj
                         else
-                            failwith $"TODO: is {v.ConcreteType} an instance of {targetType} ({targetConcreteType})"
+                            failwith
+                                $"TODO: is {AllConcreteTypes.lookup v.ConcreteType state.ConcreteTypes |> Option.get} an instance of {AllConcreteTypes.lookup targetConcreteType state.ConcreteTypes |> Option.get}"
                     | false, _ ->
 
                     match state.ManagedHeap.Arrays.TryGetValue addr with
@@ -481,7 +573,14 @@ module internal UnaryMetadataIlOp =
                     state, field
                 | MetadataToken.MemberReference mr ->
                     let state, _, field, _ =
-                        IlMachineState.resolveMember loggerFactory baseClassTypes thread activeAssy mr state
+                        IlMachineState.resolveMember
+                            loggerFactory
+                            baseClassTypes
+                            thread
+                            activeAssy
+                            ImmutableArray.Empty
+                            mr
+                            state
 
                     match field with
                     | Choice1Of2 _method -> failwith "member reference was unexpectedly a method"
@@ -492,17 +591,18 @@ module internal UnaryMetadataIlOp =
                 logger.LogInformation (
                     "Storing in object field {FieldAssembly}.{FieldDeclaringType}.{FieldName} (type {FieldType})",
                     field.DeclaringType.Assembly.Name,
-                    field.Name,
+                    field.DeclaringType.Name,
                     field.Name,
                     field.Signature
                 )
 
             let valueToStore, state = IlMachineState.popEvalStack thread state
+            let currentObj, state = IlMachineState.popEvalStack thread state
 
             let state, declaringTypeHandle, typeGenerics =
                 IlMachineState.concretizeFieldForExecution loggerFactory baseClassTypes thread field state
 
-            let state, zero =
+            let state, zero, concreteTypeHandle =
                 IlMachineState.cliTypeZeroOf
                     loggerFactory
                     baseClassTypes
@@ -514,8 +614,6 @@ module internal UnaryMetadataIlOp =
 
             let valueToStore = EvalStackValue.toCliTypeCoerced zero valueToStore
 
-            let currentObj, state = IlMachineState.popEvalStack thread state
-
             if field.Attributes.HasFlag FieldAttributes.Static then
                 let state =
                     IlMachineState.setStatic declaringTypeHandle field.Name valueToStore state
@@ -534,20 +632,7 @@ module internal UnaryMetadataIlOp =
                     match state.ManagedHeap.NonArrayObjects.TryGetValue addr with
                     | false, _ -> failwith $"todo: array {addr}"
                     | true, v ->
-                        let v =
-                            { v with
-                                Fields =
-                                    v.Fields
-                                    |> List.replaceWhere (fun f ->
-                                        if f.Name = field.Name then
-                                            { f with
-                                                Contents = valueToStore
-                                            }
-                                            |> Some
-                                        else
-                                            None
-                                    )
-                            }
+                        let v = AllocatedNonArrayObject.SetField field.Name valueToStore v
 
                         let heap =
                             { state.ManagedHeap with
@@ -576,6 +661,7 @@ module internal UnaryMetadataIlOp =
                     state |> IlMachineState.setArrayValue arr newValue index
                 | EvalStackValue.ManagedPointer (ManagedPointerSource.Field (managedPointerSource, fieldName)) ->
                     failwith "todo"
+                | EvalStackValue.ManagedPointer (ManagedPointerSource.InterpretedAsType (src, ty)) -> failwith "todo"
                 | EvalStackValue.UserDefinedValueType _ -> failwith "todo"
 
             state
@@ -601,6 +687,7 @@ module internal UnaryMetadataIlOp =
                             baseClassTypes
                             thread
                             (state.ActiveAssembly thread)
+                            ImmutableArray.Empty
                             mr
                             state
 
@@ -631,7 +718,7 @@ module internal UnaryMetadataIlOp =
 
             let popped, state = IlMachineState.popEvalStack thread state
 
-            let state, zero =
+            let state, zero, concreteTypeHandle =
                 IlMachineState.cliTypeZeroOf
                     loggerFactory
                     baseClassTypes
@@ -660,7 +747,14 @@ module internal UnaryMetadataIlOp =
                     state, field
                 | MetadataToken.MemberReference mr ->
                     let state, assyName, field, _ =
-                        IlMachineState.resolveMember loggerFactory baseClassTypes thread activeAssy mr state
+                        IlMachineState.resolveMember
+                            loggerFactory
+                            baseClassTypes
+                            thread
+                            activeAssy
+                            ImmutableArray.Empty
+                            mr
+                            state
 
                     match field with
                     | Choice1Of2 _method -> failwith "member reference was unexpectedly a method"
@@ -691,7 +785,7 @@ module internal UnaryMetadataIlOp =
                     match IlMachineState.getStatic declaringTypeHandle field.Name state with
                     | Some v -> state, v
                     | None ->
-                        let state, zero =
+                        let state, zero, concreteTypeHandle =
                             IlMachineState.cliTypeZeroOf
                                 loggerFactory
                                 baseClassTypes
@@ -733,7 +827,7 @@ module internal UnaryMetadataIlOp =
                     | false, _ -> failwith $"todo: array {managedHeapAddress}"
                     | true, v ->
                         IlMachineState.pushToEvalStack
-                            (v.Fields |> List.find (fun f -> field.Name = f.Name) |> _.Contents)
+                            (AllocatedNonArrayObject.DereferenceField field.Name v)
                             thread
                             state
                 | EvalStackValue.ManagedPointer (ManagedPointerSource.ArrayIndex (arr, index)) ->
@@ -748,9 +842,11 @@ module internal UnaryMetadataIlOp =
                         IlMachineState.getFieldValue src fieldName state |> CliType.getField field.Name
 
                     IlMachineState.pushToEvalStack currentValue thread state
+                | EvalStackValue.ManagedPointer (ManagedPointerSource.InterpretedAsType (src, ty)) -> failwith "TODO"
                 | EvalStackValue.UserDefinedValueType vt ->
-                    let result = vt |> EvalStackValueUserType.DereferenceField field.Name
-                    IlMachineState.pushToEvalStack' result thread state
+                    let result = vt |> CliValueType.DereferenceField field.Name
+
+                    IlMachineState.pushToEvalStack result thread state
 
             state
             |> IlMachineState.advanceProgramCounter thread
@@ -779,7 +875,15 @@ module internal UnaryMetadataIlOp =
                     state, field
                 | MetadataToken.MemberReference mr ->
                     let state, assyName, field, _ =
-                        IlMachineState.resolveMember loggerFactory baseClassTypes thread activeAssy mr state
+                        // TODO: generics
+                        IlMachineState.resolveMember
+                            loggerFactory
+                            baseClassTypes
+                            thread
+                            activeAssy
+                            ImmutableArray.Empty
+                            mr
+                            state
 
                     match field with
                     | Choice1Of2 _method -> failwith "member reference was unexpectedly a method"
@@ -793,6 +897,7 @@ module internal UnaryMetadataIlOp =
             |> IlMachineState.pushToEvalStack' result thread
             |> IlMachineState.advanceProgramCounter thread
             |> Tuple.withRight WhatWeDid.Executed
+
         | Ldsfld ->
             let state, field =
                 match metadataToken with
@@ -807,7 +912,14 @@ module internal UnaryMetadataIlOp =
                         state, field
                 | MetadataToken.MemberReference mr ->
                     let state, _, field, _ =
-                        IlMachineState.resolveMember loggerFactory baseClassTypes thread activeAssy mr state
+                        IlMachineState.resolveMember
+                            loggerFactory
+                            baseClassTypes
+                            thread
+                            activeAssy
+                            ImmutableArray.Empty
+                            mr
+                            state
 
                     match field with
                     | Choice1Of2 _method -> failwith "member reference was unexpectedly a method"
@@ -838,7 +950,7 @@ module internal UnaryMetadataIlOp =
             let fieldValue, state =
                 match IlMachineState.getStatic declaringTypeHandle field.Name state with
                 | None ->
-                    let state, newVal =
+                    let state, newVal, concreteTypeHandle =
                         IlMachineState.cliTypeZeroOf
                             loggerFactory
                             baseClassTypes
@@ -916,7 +1028,7 @@ module internal UnaryMetadataIlOp =
             let elementType =
                 DumpedAssembly.typeInfoToTypeDefn baseClassTypes state._LoadedAssemblies elementType
 
-            let state, zeroOfType =
+            let state, zeroOfType, concreteTypeHandle =
                 IlMachineState.cliTypeZeroOf
                     loggerFactory
                     baseClassTypes
@@ -983,6 +1095,7 @@ module internal UnaryMetadataIlOp =
             IlMachineState.pushToEvalStack toPush thread state
             |> IlMachineState.advanceProgramCounter thread
             |> Tuple.withRight WhatWeDid.Executed
+
         | Initobj ->
             let popped, state = IlMachineState.popEvalStack thread state
             let declaringTypeGenerics = currentMethod.DeclaringType.Generics
@@ -1012,7 +1125,7 @@ module internal UnaryMetadataIlOp =
                 targetType
                 |> DumpedAssembly.typeInfoToTypeDefn baseClassTypes state._LoadedAssemblies
 
-            let state, zeroOfType =
+            let state, zeroOfType, concreteTypeHandle =
                 IlMachineState.cliTypeZeroOf
                     loggerFactory
                     baseClassTypes
@@ -1040,12 +1153,14 @@ module internal UnaryMetadataIlOp =
                     | ManagedPointerSource.Field (managedPointerSource, fieldName) ->
                         state |> IlMachineState.setFieldValue managedPointerSource zeroOfType fieldName
                     | ManagedPointerSource.Null -> failwith "runtime error: unexpectedly Initobj'ing null"
+                    | ManagedPointerSource.InterpretedAsType (src, ty) -> failwith "TODO"
                     | ManagedPointerSource.Heap _ -> failwith "logic error"
                 | EvalStackValue.UserDefinedValueType evalStackValueUserType -> failwith "todo"
 
             state
             |> IlMachineState.advanceProgramCounter thread
             |> Tuple.withRight WhatWeDid.Executed
+
         | Ldsflda ->
 
             // TODO: check whether we should throw FieldAccessException
@@ -1067,30 +1182,31 @@ module internal UnaryMetadataIlOp =
             | FirstLoadThis state -> state, WhatWeDid.SuspendedForClassInit
             | NothingToDo state ->
 
-            if TypeDefn.isManaged field.Signature then
-                match IlMachineState.getStatic declaringTypeHandle field.Name state with
-                | Some v ->
-                    IlMachineState.pushToEvalStack v thread state
-                    |> IlMachineState.advanceProgramCounter thread
-                    |> Tuple.withRight WhatWeDid.Executed
-                | None ->
-                    // Field is not yet initialised
-                    let state, zero =
-                        IlMachineState.cliTypeZeroOf
-                            loggerFactory
-                            baseClassTypes
-                            activeAssy
-                            field.Signature
-                            typeGenerics
-                            ImmutableArray.Empty // field can't have its own generics
-                            state
+            // TODO: if field type is unmanaged, push an unmanaged pointer
+            // TODO: Note that field may be a static global with an assigned relative virtual address
+            // (the offset of the field from the base address at which its containing PE file is loaded into memory)
+            // where the memory is unmanaged.
+            match IlMachineState.getStatic declaringTypeHandle field.Name state with
+            | Some v ->
+                IlMachineState.pushToEvalStack v thread state
+                |> IlMachineState.advanceProgramCounter thread
+                |> Tuple.withRight WhatWeDid.Executed
+            | None ->
+                // Field is not yet initialised
+                let state, zero, concreteTypeHandle =
+                    IlMachineState.cliTypeZeroOf
+                        loggerFactory
+                        baseClassTypes
+                        activeAssy
+                        field.Signature
+                        typeGenerics
+                        ImmutableArray.Empty // field can't have its own generics
+                        state
 
-                    IlMachineState.setStatic declaringTypeHandle field.Name zero state
-                    |> IlMachineState.pushToEvalStack (CliType.ObjectRef None) thread
-                    |> IlMachineState.advanceProgramCounter thread
-                    |> Tuple.withRight WhatWeDid.Executed
-            else
-                failwith "TODO: Ldsflda - push unmanaged pointer"
+                IlMachineState.setStatic declaringTypeHandle field.Name zero state
+                |> IlMachineState.pushToEvalStack (CliType.ObjectRef None) thread
+                |> IlMachineState.advanceProgramCounter thread
+                |> Tuple.withRight WhatWeDid.Executed
 
         | Ldftn ->
             let method, methodGenerics =
@@ -1142,6 +1258,50 @@ module internal UnaryMetadataIlOp =
         | Stobj -> failwith "TODO: Stobj unimplemented"
         | Constrained -> failwith "TODO: Constrained unimplemented"
         | Ldtoken ->
+            // Helper function to handle type tokens and create RuntimeTypeHandle
+            let handleTypeToken (typeDefn : TypeDefn) (state : IlMachineState) : IlMachineState =
+                let ty = baseClassTypes.RuntimeTypeHandle
+                let field = ty.Fields |> List.exactlyOne
+
+                if field.Name <> "m_type" then
+                    failwith $"unexpected field name ${field.Name} for BCL type RuntimeTypeHandle"
+
+                let methodGenerics = currentMethod.Generics
+                let typeGenerics = currentMethod.DeclaringType.Generics
+
+                let state, handle =
+                    IlMachineState.concretizeType
+                        loggerFactory
+                        baseClassTypes
+                        state
+                        activeAssy.Name
+                        typeGenerics
+                        methodGenerics
+                        typeDefn
+
+                let alloc, state =
+                    IlMachineState.getOrAllocateType loggerFactory baseClassTypes handle state
+
+                let vt =
+                    // https://github.com/dotnet/runtime/blob/2b21c73fa2c32fa0195e4a411a435dda185efd08/src/coreclr/System.Private.CoreLib/src/System/RuntimeHandles.cs#L92
+                    {
+                        Name = "m_type"
+                        Contents = CliType.ObjectRef (Some alloc)
+                        Offset = None
+                        Type =
+                            AllConcreteTypes.findExistingConcreteType
+                                state.ConcreteTypes
+                                (baseClassTypes.Object.Assembly,
+                                 baseClassTypes.Object.Namespace,
+                                 baseClassTypes.Object.Name,
+                                 ImmutableArray.Empty)
+                            |> Option.get
+                    }
+                    |> List.singleton
+                    |> CliValueType.OfFields Layout.Default
+
+                IlMachineState.pushToEvalStack (CliType.ValueType vt) thread state
+
             let state =
                 match metadataToken with
                 | MetadataToken.FieldDefinition h ->
@@ -1179,6 +1339,7 @@ module internal UnaryMetadataIlOp =
 
                     let state, handle =
                         IlMachineState.concretizeType
+                            loggerFactory
                             baseClassTypes
                             state
                             assy.Name
@@ -1186,16 +1347,25 @@ module internal UnaryMetadataIlOp =
                             methodGenerics
                             typeDefn
 
-                    let alloc, state = IlMachineState.getOrAllocateType baseClassTypes handle state
+                    let alloc, state =
+                        IlMachineState.getOrAllocateType loggerFactory baseClassTypes handle state
 
                     let vt =
                         {
                             Name = "m_type"
                             Contents = CliType.ObjectRef (Some alloc)
                             Offset = None
+                            Type =
+                                AllConcreteTypes.findExistingConcreteType
+                                    state.ConcreteTypes
+                                    (baseClassTypes.Object.Assembly,
+                                     baseClassTypes.Object.Namespace,
+                                     baseClassTypes.Object.Name,
+                                     ImmutableArray.Empty)
+                                |> Option.get
                         }
                         |> List.singleton
-                        |> CliValueType.OfFields
+                        |> CliValueType.OfFields Layout.Default
 
                     IlMachineState.pushToEvalStack (CliType.ValueType vt) thread state
                 | MetadataToken.TypeReference h ->
@@ -1214,6 +1384,7 @@ module internal UnaryMetadataIlOp =
 
                     let state, handle =
                         IlMachineState.concretizeType
+                            loggerFactory
                             baseClassTypes
                             state
                             assy.Name
@@ -1221,60 +1392,102 @@ module internal UnaryMetadataIlOp =
                             methodGenerics
                             typeDefn
 
-                    let alloc, state = IlMachineState.getOrAllocateType baseClassTypes handle state
+                    let alloc, state =
+                        IlMachineState.getOrAllocateType loggerFactory baseClassTypes handle state
 
                     let vt =
                         {
                             Name = "m_type"
                             Contents = CliType.ObjectRef (Some alloc)
                             Offset = None
+                            Type =
+                                AllConcreteTypes.findExistingConcreteType
+                                    state.ConcreteTypes
+                                    (baseClassTypes.Object.Assembly,
+                                     baseClassTypes.Object.Namespace,
+                                     baseClassTypes.Object.Name,
+                                     ImmutableArray.Empty)
+                                |> Option.get
                         }
                         |> List.singleton
-                        |> CliValueType.OfFields
+                        |> CliValueType.OfFields Layout.Default
 
                     IlMachineState.pushToEvalStack (CliType.ValueType vt) thread state
                 | MetadataToken.TypeDefinition h ->
-                    let ty = baseClassTypes.RuntimeTypeHandle
-                    let field = ty.Fields |> List.exactlyOne
-
-                    if field.Name <> "m_type" then
-                        failwith $"unexpected field name ${field.Name} for BCL type RuntimeTypeHandle"
-
-                    let methodGenerics = currentMethod.Generics
-
-                    let typeGenerics = currentMethod.DeclaringType.Generics
-
                     let state, typeDefn =
                         IlMachineState.lookupTypeDefn baseClassTypes state activeAssy h
 
-                    let state, handle =
-                        IlMachineState.concretizeType
-                            baseClassTypes
-                            state
-                            activeAssy.Name
-                            typeGenerics
-                            methodGenerics
-                            typeDefn
-
-                    let alloc, state = IlMachineState.getOrAllocateType baseClassTypes handle state
-
-                    let vt =
-                        {
-                            Name = "m_type"
-                            Contents = CliType.ObjectRef (Some alloc)
-                            Offset = None
-                        }
-                        |> List.singleton
-                        |> CliValueType.OfFields
-
-                    IlMachineState.pushToEvalStack (CliType.ValueType vt) thread state
+                    handleTypeToken typeDefn state
                 | _ -> failwith $"Unexpected metadata token %O{metadataToken} in LdToken"
 
             state
             |> IlMachineState.advanceProgramCounter thread
             |> Tuple.withRight WhatWeDid.Executed
         | Cpobj -> failwith "TODO: Cpobj unimplemented"
-        | Ldobj -> failwith "TODO: Ldobj unimplemented"
+        | Ldobj ->
+            let state, ty, assy =
+                match metadataToken with
+                | MetadataToken.TypeDefinition h ->
+                    let state, ty = IlMachineState.lookupTypeDefn baseClassTypes state activeAssy h
+                    state, ty, activeAssy
+                | MetadataToken.TypeReference ref ->
+                    IlMachineState.lookupTypeRef
+                        loggerFactory
+                        baseClassTypes
+                        state
+                        activeAssy
+                        currentMethod.DeclaringType.Generics
+                        ref
+                | MetadataToken.TypeSpecification spec -> state, activeAssy.TypeSpecs.[spec].Signature, activeAssy
+                | _ -> failwith $"unexpected token {metadataToken} in Ldobj"
+
+            let state, typeHandle =
+                IlMachineState.concretizeType
+                    loggerFactory
+                    baseClassTypes
+                    state
+                    assy.Name
+                    currentMethod.DeclaringType.Generics
+                    currentMethod.Generics
+                    ty
+
+            let addr, state = state |> IlMachineState.popEvalStack thread
+
+            let obj =
+                match addr with
+                | EvalStackValue.ObjectRef addr ->
+                    IlMachineState.dereferencePointer state (ManagedPointerSource.Heap addr)
+                | EvalStackValue.ManagedPointer ptr -> IlMachineState.dereferencePointer state ptr
+                | EvalStackValue.Float _
+                | EvalStackValue.Int64 _
+                | EvalStackValue.Int32 _ -> failwith "refusing to interpret constant as address"
+                | _ -> failwith "TODO"
+
+            let targetType =
+                AllConcreteTypes.lookup typeHandle state.ConcreteTypes |> Option.get
+
+            let defn =
+                state._LoadedAssemblies.[targetType.Assembly.FullName].TypeDefs.[targetType.Definition.Get]
+
+            let baseType =
+                DumpedAssembly.resolveBaseType baseClassTypes state._LoadedAssemblies targetType.Assembly defn.BaseType
+
+            let toPush =
+                match baseType with
+                | ResolvedBaseType.Enum
+                | ResolvedBaseType.ValueType ->
+                    failwith
+                        $"TODO: push %O{obj} as type %s{targetType.Assembly.Name}.%s{targetType.Namespace}.%s{targetType.Name}"
+                | ResolvedBaseType.Object
+                | ResolvedBaseType.Delegate ->
+                    // III.4.13: reference types are just copied as pointers.
+                    // We should have received a pointer, so let's just pass it back.
+                    obj
+
+            state
+            |> IlMachineState.pushToEvalStack toPush thread
+            |> IlMachineState.advanceProgramCounter thread
+            |> Tuple.withRight WhatWeDid.Executed
         | Sizeof ->
             let state, ty, assy =
                 match metadataToken with
@@ -1289,10 +1502,12 @@ module internal UnaryMetadataIlOp =
                         activeAssy
                         currentMethod.DeclaringType.Generics
                         ref
+                | MetadataToken.TypeSpecification spec -> state, activeAssy.TypeSpecs.[spec].Signature, activeAssy
                 | _ -> failwith $"unexpected token {metadataToken} in Sizeof"
 
             let state, typeHandle =
                 IlMachineState.concretizeType
+                    loggerFactory
                     baseClassTypes
                     state
                     assy.Name

WoofWare.PawPrint/UnaryStringTokenIlOp.fs

@@ -2,12 +2,13 @@ namespace WoofWare.PawPrint
 
 open System.Collections.Immutable
 open System.Reflection
-open System.Reflection.Metadata
+open Microsoft.Extensions.Logging
 
 [<RequireQualifiedAccess>]
 [<CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
 module internal UnaryStringTokenIlOp =
     let execute
+        (loggerFactory : ILoggerFactory)
         (baseClassTypes : BaseClassTypes<DumpedAssembly>)
         (op : UnaryStringTokenIlOp)
         (sh : StringToken)
@@ -55,17 +56,35 @@ module internal UnaryStringTokenIlOp =
                                 Name = "_firstChar"
                                 Contents = CliType.ofChar state.ManagedHeap.StringArrayData.[dataAddr]
                                 Offset = None
+                                Type =
+                                    AllConcreteTypes.findExistingConcreteType
+                                        state.ConcreteTypes
+                                        (baseClassTypes.Char.Assembly,
+                                         baseClassTypes.Char.Namespace,
+                                         baseClassTypes.Char.Name,
+                                         ImmutableArray.Empty)
+                                    |> Option.get
                             }
                             {
                                 Name = "_stringLength"
                                 Contents = CliType.Numeric (CliNumericType.Int32 stringToAllocate.Length)
                                 Offset = None
+                                Type =
+                                    AllConcreteTypes.findExistingConcreteType
+                                        state.ConcreteTypes
+                                        (baseClassTypes.Int32.Assembly,
+                                         baseClassTypes.Int32.Namespace,
+                                         baseClassTypes.Int32.Name,
+                                         ImmutableArray.Empty)
+                                    |> Option.get
                             }
                         ]
+                        |> CliValueType.OfFields Layout.Default
 
                     let state, stringType =
                         DumpedAssembly.typeInfoToTypeDefn' baseClassTypes state._LoadedAssemblies baseClassTypes.String
                         |> IlMachineState.concretizeType
+                            loggerFactory
                             baseClassTypes
                             state
                             baseClassTypes.Corelib.Name

WoofWare.PawPrint/WoofWare.PawPrint.fsproj

@@ -10,7 +10,6 @@
     <Compile Include="List.fs" />
     <Compile Include="ImmutableArray.fs" />
     <Compile Include="Result.fs" />
-    <Compile Include="Constants.fs" />
     <Compile Include="Corelib.fs" />
     <Compile Include="AbstractMachineDomain.fs" />
     <Compile Include="BasicCliType.fs" />
@@ -21,10 +20,10 @@
     <Compile Include="Exceptions.fs" />
     <Compile Include="EvalStack.fs" />
     <Compile Include="EvalStackValueComparisons.fs" />
-    <Compile Include="BinaryArithmetic.fs" />
     <Compile Include="MethodState.fs" />
     <Compile Include="ThreadState.fs" />
     <Compile Include="IlMachineState.fs" />
+    <Compile Include="BinaryArithmetic.fs" />
     <Compile Include="Intrinsics.fs" />
     <Compile Include="IlMachineStateExecution.fs" />
     <Compile Include="NullaryIlOp.fs" />

flake.lock

@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1755736253,
-        "narHash": "sha256-jlIQRypNhB1PcB1BE+expE4xZeJxzoAGr1iUbHQta8s=",
+        "lastModified": 1756381814,
+        "narHash": "sha256-tzo7YvAsGlzo4WiIHT0ooR59VHu+aKRQdHk7sIyoia4=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "596312aae91421d6923f18cecce934a7d3bfd6b8",
+        "rev": "aca2499b79170038df0dbaec8bf2f689b506ad32",
         "type": "github"
       },
       "original": {