Interface dispatch (#100)

CLAUDE.md

@@ -42,8 +42,13 @@ dotnet fantomas .
 ```
 
 ### Running the Application
+A playground C# file is in CSharpExample/Class1.cs.
+This environment is convenient for running WoofWare.PawPrint against a standalone DLL.
+Interpolate the appropriate strings like `{Platform}` as necessary depending on the current environment and the output of the `dotnet publish`.
+
 ```bash
-dotnet publish --self-contained --runtime-id osx-arm64 CSharpExample/ && dotnet run --project WoofWare.PawPrint.App/WoofWare.PawPrint.App.fsproj -- CSharpExample/bin/Debug/net9.0/osx-arm64/publish/CSharpExample.dll
+dotnet publish --self-contained --runtime {Platform} CSharpExample/
+dotnet run --project WoofWare.PawPrint.App/WoofWare.PawPrint.App.fsproj -- CSharpExample/bin/{Configuration}/{Framework}/{Platform}/publish/CSharpExample.dll
 ```
 
 ## Architecture
@@ -62,10 +67,13 @@ dotnet publish --self-contained --runtime-id osx-arm64 CSharpExample/ && dotnet
 - `Corelib.fs`: Core library type definitions (String, Array, etc.)
 
 **WoofWare.PawPrint.Test**
-- Uses NUnit as the test framework
-- Test cases are defined in `TestCases.fs`
-- C# source files in `sources/` are compiled and executed by the runtime as test cases
+- Uses Expecto 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
 - `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
@@ -90,8 +98,8 @@ dotnet publish --self-contained --runtime-id osx-arm64 CSharpExample/ && dotnet
 When adding new IL instruction support:
 1. Add the instruction to `IlOp.fs`
 2. Implement execution logic in `AbstractMachine.fs`
-3. Add a test case in `sources/` (C# file) that exercises the instruction
-4. Add the test case to `TestCases.fs`
+3. Add a test case in `sourcesPure/` or `sourcesImpure/` (C# file) that exercises the instruction, remembering also to add the file as an EmbeddedResource in WoofWare.PawPrint.Test.fsproj
+4. Add the test case to `TestPureCases.fs` or `TestImpureCases.fs`
 5. Run tests to verify implementation
 
 The project uses deterministic builds and treats warnings as errors to maintain code quality.
@@ -174,3 +182,47 @@ When encountering errors:
 4. Add logging to see generic contexts: `failwithf "Failed to concretize: %A" typeDefn`
 5. Check if you're in a generic method calling another generic method
 6. Verify TypeRefs are being resolved in the correct assembly
+
+## Common Type System Patterns
+
+### Creating TypeDefn from Type Metadata
+
+When you need to create a `TypeDefn` from type metadata (e.g., from a `TypeInfo`), there's a common pattern that involves:
+1. Resolving the base type to determine `SignatureTypeKind`
+2. Creating the base `TypeDefn.FromDefinition`
+3. For generic types, creating a `GenericInstantiation` with type parameters
+
+This pattern is implemented in `UnaryMetadataIlOp.lookupTypeDefn`. Example usage:
+```fsharp
+let state, typeDefn =
+    UnaryMetadataIlOp.lookupTypeDefn
+        baseClassTypes
+        state
+        activeAssembly
+        typeDefHandle
+```
+
+### Field Signature Comparison in Generic Contexts
+
+When comparing field signatures in generic contexts (e.g., when resolving member references), signatures must be concretized before comparison. This ensures generic type parameters are properly substituted:
+
+```fsharp
+// Concretize both signatures before comparing
+let state, concreteFieldSig = concretizeType ... fieldSig
+let state, fieldSigConcrete = concretizeType ... fi.Signature
+if fieldSigConcrete = concreteFieldSig then ...
+```
+
+### Static vs Instance Fields
+
+When constructing objects with `Newobj`:
+- Only instance fields should be included in the object
+- Static fields belong to the type, not instances
+- Filter using: `field.Attributes.HasFlag FieldAttributes.Static`
+
+Example:
+```fsharp
+let instanceFields =
+    ctorType.Fields
+    |> List.filter (fun field -> not (field.Attributes.HasFlag FieldAttributes.Static))
+```

CSharpExample/CSharpExample.csproj

@@ -6,6 +6,11 @@
       <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
       <WarningsAsErrors>false</WarningsAsErrors>
       <TreatWarningsAsErrors>false</TreatWarningsAsErrors>
+      <EnableDefaultItems>false</EnableDefaultItems>
     </PropertyGroup>
 
+  <ItemGroup>
+    <Compile Include="Class1.cs" />
+  </ItemGroup>
+
 </Project>

WoofWare.PawPrint.Domain/Assembly.fs

@@ -45,10 +45,7 @@ type DumpedAssembly =
         /// Dictionary of all type definitions in this assembly, keyed by their handle.
         /// </summary>
         TypeDefs :
-            IReadOnlyDictionary<
-                TypeDefinitionHandle,
-                WoofWare.PawPrint.TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-             >
+            IReadOnlyDictionary<TypeDefinitionHandle, WoofWare.PawPrint.TypeInfo<GenericParamFromMetadata, TypeDefn>>
 
         /// <summary>
         /// Dictionary of all type references in this assembly, keyed by their handle.
@@ -67,7 +64,7 @@ type DumpedAssembly =
         Methods :
             IReadOnlyDictionary<
                 MethodDefinitionHandle,
-                WoofWare.PawPrint.MethodInfo<FakeUnit, WoofWare.PawPrint.GenericParameter, TypeDefn>
+                WoofWare.PawPrint.MethodInfo<GenericParamFromMetadata, GenericParamFromMetadata, TypeDefn>
              >
 
         /// <summary>
@@ -78,7 +75,8 @@ type DumpedAssembly =
         /// <summary>
         /// Dictionary of all field definitions in this assembly, keyed by their handle.
         /// </summary>
-        Fields : IReadOnlyDictionary<FieldDefinitionHandle, WoofWare.PawPrint.FieldInfo<FakeUnit, TypeDefn>>
+        Fields :
+            IReadOnlyDictionary<FieldDefinitionHandle, WoofWare.PawPrint.FieldInfo<GenericParamFromMetadata, TypeDefn>>
 
         /// <summary>
         /// The entry point method of the assembly, if one exists.
@@ -146,10 +144,7 @@ type DumpedAssembly =
         /// Internal lookup for type definitions by namespace and name.
         /// </summary>
         _TypeDefsLookup :
-            ImmutableDictionary<
-                string * string,
-                WoofWare.PawPrint.TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-             >
+            ImmutableDictionary<string * string, WoofWare.PawPrint.TypeInfo<GenericParamFromMetadata, TypeDefn>>
     }
 
     static member internal BuildExportedTypesLookup
@@ -205,7 +200,7 @@ type DumpedAssembly =
     static member internal BuildTypeDefsLookup
         (logger : ILogger)
         (name : AssemblyName)
-        (typeDefs : WoofWare.PawPrint.TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn> seq)
+        (typeDefs : WoofWare.PawPrint.TypeInfo<GenericParamFromMetadata, TypeDefn> seq)
         =
         let result = ImmutableDictionary.CreateBuilder ()
         let keys = HashSet ()
@@ -236,7 +231,7 @@ type DumpedAssembly =
     member this.TypeDef
         (``namespace`` : string)
         (name : string)
-        : WoofWare.PawPrint.TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn> option
+        : WoofWare.PawPrint.TypeInfo<GenericParamFromMetadata, TypeDefn> option
         =
         match this._TypeDefsLookup.TryGetValue ((``namespace``, name)) with
         | false, _ -> None
@@ -467,7 +462,8 @@ module Assembly =
 
                 match targetType with
                 | [ t ] ->
-                    let t = t |> TypeInfo.mapGeneric (fun _ param -> genericArgs.[param.SequenceNumber])
+                    let t =
+                        t |> TypeInfo.mapGeneric (fun (param, md) -> genericArgs.[param.SequenceNumber])
 
                     TypeResolutionResult.Resolved (assy, t)
                 | _ :: _ :: _ -> failwith $"Multiple matching type definitions! {nsPath} {target.Name}"
@@ -493,7 +489,7 @@ module Assembly =
         | Some typeDef ->
             let typeDef =
                 typeDef
-                |> TypeInfo.mapGeneric (fun _ param -> genericArgs.[param.SequenceNumber])
+                |> TypeInfo.mapGeneric (fun (param, md) -> genericArgs.[param.SequenceNumber])
 
             TypeResolutionResult.Resolved (assy, typeDef)
         | None ->

WoofWare.PawPrint.Domain/ComparableFieldDefinitionHandle.fs

@@ -0,0 +1,37 @@
+namespace WoofWare.PawPrint
+
+open System
+open System.Reflection.Metadata
+
+[<CustomEquality>]
+[<CustomComparison>]
+type ComparableFieldDefinitionHandle =
+    private
+        {
+            _Inner : FieldDefinitionHandle
+        }
+
+    override this.Equals other =
+        match other with
+        | :? ComparableFieldDefinitionHandle as other -> this._Inner.GetHashCode () = other._Inner.GetHashCode ()
+        | _ -> false
+
+    override this.GetHashCode () : int = this._Inner.GetHashCode ()
+
+    interface IComparable<ComparableFieldDefinitionHandle> with
+        member this.CompareTo (other : ComparableFieldDefinitionHandle) : int =
+            this._Inner.GetHashCode().CompareTo (other._Inner.GetHashCode ())
+
+    interface IComparable with
+        member this.CompareTo (other : obj) : int =
+            match other with
+            | :? ComparableFieldDefinitionHandle as other ->
+                (this :> IComparable<ComparableFieldDefinitionHandle>).CompareTo other
+            | _ -> failwith "invalid comparison"
+
+    static member Make (h : FieldDefinitionHandle) =
+        {
+            _Inner = h
+        }
+
+    member this.Get = this._Inner

WoofWare.PawPrint.Domain/ComparableTypeDefinitionHandle.fs

@@ -11,7 +11,7 @@ type ComparableTypeDefinitionHandle =
             _Inner : TypeDefinitionHandle
         }
 
-    override this.Equals (other) =
+    override this.Equals other =
         match other with
         | :? ComparableTypeDefinitionHandle as other -> this._Inner.GetHashCode () = other._Inner.GetHashCode ()
         | _ -> false

WoofWare.PawPrint.Domain/ConcreteType.fs

@@ -1,6 +1,6 @@
 namespace WoofWare.PawPrint
 
-open System
+open System.Collections.Immutable
 open System.Reflection
 open System.Reflection.Metadata
 
@@ -16,8 +16,8 @@ module FakeUnit =
 
 /// A type which has been concretised, runtime-representable, etc.
 [<CustomEquality>]
-[<CustomComparison>]
-type ConcreteType<'typeGeneric when 'typeGeneric : comparison and 'typeGeneric :> IComparable<'typeGeneric>> =
+[<NoComparison>]
+type ConcreteType<'typeGeneric> =
     private
         {
             /// Do not use this, because it's intended to be private; use the accessor `.Assembly : AssemblyName`
@@ -30,12 +30,12 @@ type ConcreteType<'typeGeneric when 'typeGeneric : comparison and 'typeGeneric :
             /// Do not use this, because it's intended to be private; use the accessor `.Namespace` instead.
             _Namespace : string
             /// Do not use this, because it's intended to be private; use the accessor `.Generics` instead.
-            _Generics : 'typeGeneric list
+            _Generics : ImmutableArray<'typeGeneric>
         }
 
     member this.Assembly : AssemblyName = this._AssemblyName
     member this.Definition : ComparableTypeDefinitionHandle = this._Definition
-    member this.Generics : 'typeGeneric list = this._Generics
+    member this.Generics : ImmutableArray<'typeGeneric> = this._Generics
     member this.Name = this._Name
     member this.Namespace = this._Namespace
 
@@ -50,72 +50,26 @@ type ConcreteType<'typeGeneric when 'typeGeneric : comparison and 'typeGeneric :
     override this.GetHashCode () : int =
         hash (this._AssemblyName.FullName, this._Definition, this._Generics)
 
-    interface IComparable<ConcreteType<'typeGeneric>> with
-        member this.CompareTo (other : ConcreteType<'typeGeneric>) : int =
-            let comp = this._AssemblyName.FullName.CompareTo other._AssemblyName.FullName
-
-            if comp <> 0 then
-                comp
-            else
-
-            let comp =
-                (this._Definition :> IComparable<ComparableTypeDefinitionHandle>).CompareTo other._Definition
-
-            if comp <> 0 then
-                comp
-            else
-
-            let thisGen = (this._Generics : 'typeGeneric list) :> IComparable<'typeGeneric list>
-            thisGen.CompareTo other._Generics
-
-    interface IComparable with
-        member this.CompareTo other =
-            match other with
-            | :? ConcreteType<'typeGeneric> as other ->
-                (this :> IComparable<ConcreteType<'typeGeneric>>).CompareTo other
-            | _ -> failwith "bad comparison"
-
 [<RequireQualifiedAccess>]
 module ConcreteType =
     let make
         (assemblyName : AssemblyName)
+        (defn : TypeDefinitionHandle)
         (ns : string)
         (name : string)
-        (defn : TypeDefinitionHandle)
-        (generics : TypeDefn list)
-        : ConcreteType<TypeDefn>
+        (genericParam : ImmutableArray<GenericParamFromMetadata>)
+        : ConcreteType<GenericParamFromMetadata>
         =
         {
             _AssemblyName = assemblyName
             _Definition = ComparableTypeDefinitionHandle.Make defn
             _Name = name
             _Namespace = ns
-            _Generics = generics
+            _Generics = genericParam
         }
 
-    let make'
-        (assemblyName : AssemblyName)
-        (defn : TypeDefinitionHandle)
-        (ns : string)
-        (name : string)
-        (genericParamCount : int)
-        : ConcreteType<FakeUnit>
-        =
-        {
-            _AssemblyName = assemblyName
-            _Definition = ComparableTypeDefinitionHandle.Make defn
-            _Name = name
-            _Namespace = ns
-            _Generics = List.replicate genericParamCount FakeUnit.FakeUnit
-        }
-
-    let mapGeneric<'a, 'b
-        when 'a : comparison and 'a :> IComparable<'a> and 'b : equality and 'b : comparison and 'b :> IComparable<'b>>
-        (f : int -> 'a -> 'b)
-        (x : ConcreteType<'a>)
-        : ConcreteType<'b>
-        =
-        let generics = x._Generics |> List.mapi f
+    let mapGeneric<'a, 'b> (f : int -> 'a -> 'b) (x : ConcreteType<'a>) : ConcreteType<'b> =
+        let generics = x._Generics |> Seq.mapi f |> ImmutableArray.CreateRange
 
         {
             _AssemblyName = x._AssemblyName

WoofWare.PawPrint.Domain/FieldInfo.fs

@@ -1,6 +1,5 @@
 namespace WoofWare.PawPrint
 
-open System
 open System.Reflection
 open System.Reflection.Metadata
 
@@ -8,8 +7,7 @@ open System.Reflection.Metadata
 /// Represents detailed information about a field in a .NET assembly.
 /// This is a strongly-typed representation of FieldDefinition from System.Reflection.Metadata.
 /// </summary>
-type FieldInfo<'typeGeneric, 'fieldGeneric when 'typeGeneric : comparison and 'typeGeneric :> IComparable<'typeGeneric>>
-    =
+type FieldInfo<'typeGeneric, 'fieldGeneric> =
     {
         /// <summary>
         /// The metadata token handle that uniquely identifies this field in the assembly.
@@ -36,6 +34,8 @@ type FieldInfo<'typeGeneric, 'fieldGeneric when 'typeGeneric : comparison and 't
         Attributes : FieldAttributes
     }
 
+    member this.HasFieldRVA = this.Attributes.HasFlag FieldAttributes.HasFieldRVA
+
     override this.ToString () : string =
         $"%s{this.DeclaringType.Assembly.Name}.{this.DeclaringType.Name}.%s{this.Name}"
 
@@ -46,18 +46,22 @@ module FieldInfo =
         (assembly : AssemblyName)
         (handle : FieldDefinitionHandle)
         (def : FieldDefinition)
-        : FieldInfo<FakeUnit, TypeDefn>
+        : FieldInfo<GenericParamFromMetadata, TypeDefn>
         =
         let name = mr.GetString def.Name
         let fieldSig = def.DecodeSignature (TypeDefn.typeProvider assembly, ())
         let declaringType = def.GetDeclaringType ()
-        let typeGenerics = mr.GetTypeDefinition(declaringType).GetGenericParameters().Count
-        let decType = mr.GetTypeDefinition (declaringType)
+
+        let typeGenerics =
+            mr.GetTypeDefinition(declaringType).GetGenericParameters ()
+            |> GenericParameter.readAll mr
+
+        let decType = mr.GetTypeDefinition declaringType
         let declaringTypeNamespace = mr.GetString decType.Namespace
         let declaringTypeName = mr.GetString decType.Name
 
         let declaringType =
-            ConcreteType.make' assembly declaringType declaringTypeNamespace declaringTypeName typeGenerics
+            ConcreteType.make assembly declaringType declaringTypeNamespace declaringTypeName typeGenerics
 
         {
             Name = name
@@ -67,12 +71,7 @@ module FieldInfo =
             Attributes = def.Attributes
         }
 
-    let mapTypeGenerics<'a, 'b, 'field
-        when 'a :> IComparable<'a> and 'a : comparison and 'b :> IComparable<'b> and 'b : comparison>
-        (f : int -> 'a -> 'b)
-        (input : FieldInfo<'a, 'field>)
-        : FieldInfo<'b, 'field>
-        =
+    let mapTypeGenerics<'a, 'b, 'field> (f : int -> 'a -> 'b) (input : FieldInfo<'a, 'field>) : FieldInfo<'b, 'field> =
         let declaringType = input.DeclaringType |> ConcreteType.mapGeneric f
 
         {

WoofWare.PawPrint.Domain/GenericParameter.fs

@@ -0,0 +1,85 @@
+namespace WoofWare.PawPrint
+
+open System.Collections.Immutable
+open System.Reflection
+open System.Reflection.Metadata
+
+type GenericVariance =
+    | Covariant
+    | Contravariant
+
+type GenericConstraint =
+    | Reference
+    | NonNullableValue
+
+type GenericParamMetadata =
+    {
+        Variance : GenericVariance option
+        Constraint : GenericConstraint option
+        RequiresParameterlessConstructor : bool
+    }
+
+/// <summary>
+/// Represents a generic type or method parameter definition.
+/// Corresponds to GenericParameter in System.Reflection.Metadata.
+/// </summary>
+type GenericParameter =
+    {
+        /// <summary>The name of the generic parameter (e.g., 'T', 'TKey', etc.).</summary>
+        Name : string
+
+        /// <summary>
+        /// The zero-based index of the generic parameter in the generic parameter list.
+        /// For example, in Dictionary&lt;TKey, TValue&rt;, TKey has index 0 and TValue has index 1.
+        /// </summary>
+        SequenceNumber : int
+    }
+
+type GenericParamFromMetadata = GenericParameter * GenericParamMetadata
+
+[<RequireQualifiedAccess>]
+module GenericParameter =
+    let readAll
+        (metadata : MetadataReader)
+        (param : GenericParameterHandleCollection)
+        : GenericParamFromMetadata ImmutableArray
+        =
+        param
+        |> Seq.map (fun param ->
+            let param = metadata.GetGenericParameter param
+
+            let requiresParamlessCons =
+                param.Attributes.HasFlag GenericParameterAttributes.DefaultConstructorConstraint
+
+            let constr =
+                if param.Attributes.HasFlag GenericParameterAttributes.NotNullableValueTypeConstraint then
+                    Some GenericConstraint.NonNullableValue
+                elif param.Attributes.HasFlag GenericParameterAttributes.ReferenceTypeConstraint then
+                    Some GenericConstraint.Reference
+                else
+                    None
+
+            let variance =
+                if param.Attributes.HasFlag GenericParameterAttributes.Contravariant then
+                    Some GenericVariance.Contravariant
+                elif param.Attributes.HasFlag GenericParameterAttributes.Covariant then
+                    Some GenericVariance.Covariant
+                else
+                    None
+
+            let md =
+                {
+                    Variance = variance
+                    Constraint = constr
+                    RequiresParameterlessConstructor = requiresParamlessCons
+                }
+
+            let p =
+                {
+                    Name = metadata.GetString param.Name
+                    SequenceNumber = param.Index
+                }
+
+            p, md
+        )
+        |> ImmutableArray.CreateRange

WoofWare.PawPrint.Domain/ImmutableArray.fs

@@ -0,0 +1,22 @@
+namespace WoofWare.PawPrint
+
+open System.Collections.Immutable
+
+[<RequireQualifiedAccess>]
+module internal ImmutableArray =
+
+    let inline map ([<InlineIfLambda>] f : 'a -> 'b) (arr : ImmutableArray<'a>) : ImmutableArray<'b> =
+        let b = ImmutableArray.CreateBuilder ()
+
+        for i in arr do
+            b.Add (f i)
+
+        b.ToImmutable ()
+
+    let inline mapi ([<InlineIfLambda>] f : int -> 'a -> 'b) (arr : ImmutableArray<'a>) : ImmutableArray<'b> =
+        let b = ImmutableArray.CreateBuilder ()
+
+        for i = 0 to arr.Length - 1 do
+            b.Add (f i arr.[i])
+
+        b.ToImmutable ()

WoofWare.PawPrint.Domain/MethodInfo.fs

@@ -52,40 +52,6 @@ module Parameter =
 
         result.ToImmutable ()
 
-/// <summary>
-/// Represents a generic type or method parameter definition.
-/// Corresponds to GenericParameter in System.Reflection.Metadata.
-/// </summary>
-type GenericParameter =
-    {
-        /// <summary>The name of the generic parameter (e.g., 'T', 'TKey', etc.).</summary>
-        Name : string
-
-        /// <summary>
-        /// The zero-based index of the generic parameter in the generic parameter list.
-        /// For example, in Dictionary&lt;TKey, TValue&rt;, TKey has index 0 and TValue has index 1.
-        /// </summary>
-        SequenceNumber : int
-    }
-
-[<RequireQualifiedAccess>]
-module GenericParameter =
-    let readAll
-        (metadata : MetadataReader)
-        (param : GenericParameterHandleCollection)
-        : GenericParameter ImmutableArray
-        =
-        param
-        |> Seq.map (fun param ->
-            let param = metadata.GetGenericParameter param
-
-            {
-                Name = metadata.GetString param.Name
-                SequenceNumber = param.Index
-            }
-        )
-        |> ImmutableArray.CreateRange
-
 type ExceptionOffset =
     {
         TryLength : int
@@ -168,8 +134,7 @@ module MethodInstructions =
 /// Represents detailed information about a method in a .NET assembly.
 /// This is a strongly-typed representation of MethodDefinition from System.Reflection.Metadata.
 /// </summary>
-type MethodInfo<'typeGenerics, 'methodGenerics, 'methodVars
-    when 'typeGenerics :> IComparable<'typeGenerics> and 'typeGenerics : comparison> =
+type MethodInfo<'typeGenerics, 'methodGenerics, 'methodVars> =
     {
         /// <summary>
         /// The type that declares this method, along with its assembly information.
@@ -267,14 +232,13 @@ module MethodInfo =
             | con -> failwith $"TODO: {con}"
         )
 
-    let mapTypeGenerics<'a, 'b, 'methodGen, 'vars
-        when 'a :> IComparable<'a> and 'a : comparison and 'b : comparison and 'b :> IComparable<'b>>
-        (f : int -> 'a -> 'b)
+    let mapTypeGenerics<'a, 'b, 'methodGen, 'vars>
+        (f : 'a -> 'b)
         (m : MethodInfo<'a, 'methodGen, 'vars>)
         : MethodInfo<'b, 'methodGen, 'vars>
         =
         {
-            DeclaringType = m.DeclaringType |> ConcreteType.mapGeneric f
+            DeclaringType = m.DeclaringType |> ConcreteType.mapGeneric (fun _ -> f)
             Handle = m.Handle
             Name = m.Name
             Instructions = m.Instructions
@@ -288,18 +252,20 @@ module MethodInfo =
             IsStatic = m.IsStatic
         }
 
-    let mapMethodGenerics<'a, 'b, 'vars, 'typeGen when 'typeGen :> IComparable<'typeGen> and 'typeGen : comparison>
+    let mapMethodGenerics<'a, 'b, 'vars, 'typeGen>
         (f : int -> 'a -> 'b)
         (m : MethodInfo<'typeGen, 'a, 'vars>)
         : MethodInfo<'typeGen, 'b, 'vars>
         =
+        let generics = m.Generics |> Seq.mapi f |> ImmutableArray.CreateRange
+
         {
             DeclaringType = m.DeclaringType
             Handle = m.Handle
             Name = m.Name
             Instructions = m.Instructions
             Parameters = m.Parameters
-            Generics = m.Generics |> Seq.mapi f |> ImmutableArray.CreateRange
+            Generics = generics
             Signature = m.Signature
             RawSignature = m.RawSignature
             CustomAttributes = m.CustomAttributes
@@ -676,7 +642,7 @@ module MethodInfo =
         (peReader : PEReader)
         (metadataReader : MetadataReader)
         (methodHandle : MethodDefinitionHandle)
-        : MethodInfo<FakeUnit, GenericParameter, TypeDefn> option
+        : MethodInfo<GenericParamFromMetadata, GenericParamFromMetadata, TypeDefn> option
         =
         let logger = loggerFactory.CreateLogger "MethodInfo"
         let assemblyName = metadataReader.GetAssemblyDefinition().GetAssemblyName ()
@@ -717,7 +683,8 @@ module MethodInfo =
         let declaringTypeName = metadataReader.GetString declaringDefn.Name
 
         let declaringTypeGenericParams =
-            metadataReader.GetTypeDefinition(declaringType).GetGenericParameters().Count
+            metadataReader.GetTypeDefinition(declaringType).GetGenericParameters ()
+            |> GenericParameter.readAll metadataReader
 
         let attrs =
             let result = ImmutableArray.CreateBuilder ()
@@ -738,7 +705,7 @@ module MethodInfo =
             GenericParameter.readAll metadataReader (methodDef.GetGenericParameters ())
 
         let declaringType =
-            ConcreteType.make'
+            ConcreteType.make
                 assemblyName
                 declaringType
                 declaringTypeNamespace

WoofWare.PawPrint.Domain/TypeConcretisation.fs

@@ -1,5 +1,6 @@
 namespace WoofWare.PawPrint
 
+open System
 open System.Collections.Immutable
 open System.Reflection
 open System.Reflection.Metadata
@@ -9,6 +10,12 @@ type ConcreteTypeHandle =
     | Byref of ConcreteTypeHandle
     | Pointer of ConcreteTypeHandle
 
+    override this.ToString () =
+        match this with
+        | ConcreteTypeHandle.Byref b -> "&" + b.ToString ()
+        | ConcreteTypeHandle.Concrete i -> i.ToString ()
+        | ConcreteTypeHandle.Pointer i -> "*" + i.ToString ()
+
 type AllConcreteTypes =
     {
         Mapping : Map<int, ConcreteType<ConcreteTypeHandle>>
@@ -46,7 +53,7 @@ module AllConcreteTypes =
 
     let findExistingConcreteType
         (concreteTypes : AllConcreteTypes)
-        (asm : AssemblyName, ns : string, name : string, generics : ConcreteTypeHandle list as key)
+        (asm : AssemblyName, ns : string, name : string, generics : ConcreteTypeHandle ImmutableArray)
         : ConcreteTypeHandle option
         =
         concreteTypes.Mapping
@@ -75,10 +82,242 @@ module AllConcreteTypes =
 
         toRet, newState
 
+// Active patterns for matching concrete types
+
+[<AutoOpen>]
+module ConcreteActivePatterns =
+    /// Active pattern to match primitive types from concrete type handles
+    let (|ConcretePrimitive|_|) (concreteTypes : AllConcreteTypes) (handle : ConcreteTypeHandle) =
+        match handle with
+        | ConcreteTypeHandle.Concrete id ->
+            match concreteTypes.Mapping |> Map.tryFind id with
+            | Some ct when ct.Namespace = "System" && ct.Generics.IsEmpty ->
+                match ct.Name with
+                | "Int32" -> Some PrimitiveType.Int32
+                | "Int64" -> Some PrimitiveType.Int64
+                | "Int16" -> Some PrimitiveType.Int16
+                | "UInt32" -> Some PrimitiveType.UInt32
+                | "UInt64" -> Some PrimitiveType.UInt64
+                | "UInt16" -> Some PrimitiveType.UInt16
+                | "Byte" -> Some PrimitiveType.Byte
+                | "SByte" -> Some PrimitiveType.SByte
+                | "Single" -> Some PrimitiveType.Single
+                | "Double" -> Some PrimitiveType.Double
+                | "String" -> Some PrimitiveType.String
+                | "Boolean" -> Some PrimitiveType.Boolean
+                | "Char" -> Some PrimitiveType.Char
+                | "Object" -> Some PrimitiveType.Object
+                | "IntPtr" -> Some PrimitiveType.IntPtr
+                | "UIntPtr" -> Some PrimitiveType.UIntPtr
+                | "TypedReference" -> Some PrimitiveType.TypedReference
+                | _ -> None
+            | _ -> None
+        | _ -> None
+
+    /// Active pattern to match void type
+    let (|ConcreteVoid|_|) (concreteTypes : AllConcreteTypes) (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 = "Void"
+                && ct.Generics.IsEmpty
+                ->
+                Some ()
+            | _ -> None
+        | _ -> None
+
+    /// Active pattern to match any concrete type by assembly/namespace/name and generics
+    let (|ConcreteType|_|) (concreteTypes : AllConcreteTypes) (handle : ConcreteTypeHandle) =
+        match handle with
+        | ConcreteTypeHandle.Concrete id ->
+            match concreteTypes.Mapping |> Map.tryFind id with
+            | Some ct -> Some (ct.Assembly.Name, ct.Namespace, ct.Name, ct.Generics)
+            | None -> None
+        | _ -> None
+
+    let (|ConcreteRuntimeFieldHandle|_|) (concreteTypes : AllConcreteTypes) (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 = "RuntimeFieldHandle"
+                && ct.Generics.IsEmpty
+                ->
+                Some ()
+            | _ -> None
+        | _ -> None
+
+    let (|ConcreteNonGenericArray|_|) (concreteTypes : AllConcreteTypes) (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"
+                && ct.Generics.IsEmpty
+                ->
+                Some ()
+            | _ -> None
+        | _ -> None
+
+    let (|ConcreteObj|_|) (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 = "Object"
+                    && ct.Generics.IsEmpty
+                then
+                    Some ()
+                else
+                    None
+            | None -> None
+        | _ -> None
+
+    let (|ConcreteValueType|_|) (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 = "ValueType"
+                    && ct.Generics.IsEmpty
+                then
+                    Some ()
+                else
+                    None
+            | None -> None
+        | _ -> None
+
+    let (|ConcreteBool|_|) (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 = "Boolean"
+                    && ct.Generics.IsEmpty
+                then
+                    Some ()
+                else
+                    None
+            | None -> None
+        | _ -> None
+
+    let (|ConcreteString|_|) (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 = "String"
+                    && ct.Generics.IsEmpty
+                then
+                    Some ()
+                else
+                    None
+            | None -> None
+        | _ -> None
+
+    let (|ConcreteDouble|_|) (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 = "Double"
+                    && ct.Generics.IsEmpty
+                then
+                    Some ()
+                else
+                    None
+            | None -> None
+        | _ -> None
+
+    let (|ConcreteInt64|_|) (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 = "Int64"
+                    && ct.Generics.IsEmpty
+                then
+                    Some ()
+                else
+                    None
+            | None -> None
+        | _ -> None
+
+    let (|ConcreteInt32|_|) (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 = "Int32"
+                    && ct.Generics.IsEmpty
+                then
+                    Some ()
+                else
+                    None
+            | None -> None
+        | _ -> None
+
+    let (|ConcreteSingle|_|) (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 = "Single"
+                    && ct.Generics.IsEmpty
+                then
+                    Some ()
+                else
+                    None
+            | None -> None
+        | _ -> None
+
+    /// Active pattern to match byref types
+    let (|ConcreteByref|_|) (handle : ConcreteTypeHandle) =
+        match handle with
+        | ConcreteTypeHandle.Byref inner -> Some inner
+        | _ -> None
+
+    /// Active pattern to match pointer types
+    let (|ConcretePointer|_|) (handle : ConcreteTypeHandle) =
+        match handle with
+        | ConcreteTypeHandle.Pointer inner -> Some inner
+        | _ -> None
+
 [<RequireQualifiedAccess>]
 module TypeConcretization =
 
-    type ConcretizationContext =
+    type ConcretizationContext<'corelib> =
         {
             /// Types currently being processed (to detect cycles)
             InProgress : ImmutableDictionary<AssemblyName * TypeDefn, ConcreteTypeHandle>
@@ -86,7 +325,7 @@ module TypeConcretization =
             ConcreteTypes : AllConcreteTypes
             /// For resolving type references
             LoadedAssemblies : ImmutableDictionary<string, DumpedAssembly>
-            BaseTypes : BaseClassTypes<DumpedAssembly>
+            BaseTypes : BaseClassTypes<'corelib>
         }
 
     // Helper function to find existing types by assembly, namespace, name, and generics
@@ -95,7 +334,7 @@ module TypeConcretization =
         (assembly : AssemblyName)
         (ns : string)
         (name : string)
-        (generics : ConcreteTypeHandle list)
+        (generics : ConcreteTypeHandle ImmutableArray)
         : ConcreteTypeHandle option
         =
         concreteTypes.Mapping
@@ -117,18 +356,18 @@ module TypeConcretization =
         (key : AssemblyName * string * string)
         : ConcreteTypeHandle option
         =
-        let (asm, ns, name) = key
-        findExistingType concreteTypes asm ns name []
+        let asm, ns, name = key
+        findExistingType concreteTypes asm ns name ImmutableArray.Empty
 
     // Helper function to create and add a ConcreteType to the context
     let private createAndAddConcreteType
-        (ctx : ConcretizationContext)
+        (ctx : ConcretizationContext<'corelib>)
         (assembly : AssemblyName)
         (definition : ComparableTypeDefinitionHandle)
         (ns : string)
         (name : string)
-        (generics : ConcreteTypeHandle list)
-        : ConcreteTypeHandle * ConcretizationContext
+        (generics : ConcreteTypeHandle ImmutableArray)
+        : ConcreteTypeHandle * ConcretizationContext<'corelib>
         =
         let concreteType =
             {
@@ -152,10 +391,10 @@ module TypeConcretization =
     let private loadAssemblyAndResolveTypeRef
         (loadAssembly :
             AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
-        (ctx : ConcretizationContext)
+        (ctx : ConcretizationContext<'corelib>)
         (currentAssembly : AssemblyName)
         (typeRef : TypeRef)
-        : (DumpedAssembly * WoofWare.PawPrint.TypeInfo<_, _>) * ConcretizationContext
+        : (DumpedAssembly * WoofWare.PawPrint.TypeInfo<_, _>) * ConcretizationContext<'corelib>
         =
         let currentAssy =
             match ctx.LoadedAssemblies.TryGetValue currentAssembly.FullName with
@@ -172,7 +411,7 @@ module TypeConcretization =
             // Need to load the assembly
             match typeRef.ResolutionScope with
             | TypeRefResolutionScope.Assembly assyRef ->
-                let newAssemblies, loadedAssy = loadAssembly currentAssembly assyRef
+                let newAssemblies, _ = loadAssembly currentAssembly assyRef
 
                 let newCtx =
                     { ctx with
@@ -190,9 +429,9 @@ module TypeConcretization =
             | _ -> failwith "Unexpected resolution scope"
 
     let private concretizePrimitive
-        (ctx : ConcretizationContext)
+        (ctx : ConcretizationContext<'corelib>)
         (prim : PrimitiveType)
-        : ConcreteTypeHandle * ConcretizationContext
+        : ConcreteTypeHandle * ConcretizationContext<'corelib>
         =
 
         // Get the TypeInfo for this primitive from BaseClassTypes
@@ -229,13 +468,13 @@ module TypeConcretization =
                 (ComparableTypeDefinitionHandle.Make typeInfo.TypeDefHandle)
                 typeInfo.Namespace
                 typeInfo.Name
-                [] // Primitives have no generic parameters
+                ImmutableArray.Empty // Primitives have no generic parameters
 
     let private concretizeArray
-        (ctx : ConcretizationContext)
+        (ctx : ConcretizationContext<'corelib>)
         (elementHandle : ConcreteTypeHandle)
         (shape : 'a)
-        : ConcreteTypeHandle * ConcretizationContext
+        : ConcreteTypeHandle * ConcretizationContext<'corelib>
         =
 
         // Arrays are System.Array<T> where T is the element type
@@ -248,7 +487,7 @@ module TypeConcretization =
                 arrayTypeInfo.Assembly
                 arrayTypeInfo.Namespace
                 arrayTypeInfo.Name
-                [ elementHandle ]
+                (ImmutableArray.Create elementHandle)
         with
         | Some handle -> handle, ctx
         | None ->
@@ -259,12 +498,12 @@ module TypeConcretization =
                 (ComparableTypeDefinitionHandle.Make arrayTypeInfo.TypeDefHandle)
                 arrayTypeInfo.Namespace
                 arrayTypeInfo.Name
-                [ elementHandle ] // Array<T> has one generic parameter
+                (ImmutableArray.Create elementHandle) // Array<T> has one generic parameter
 
     let private concretizeOneDimArray
-        (ctx : ConcretizationContext)
+        (ctx : ConcretizationContext<'corelib>)
         (elementHandle : ConcreteTypeHandle)
-        : ConcreteTypeHandle * ConcretizationContext
+        : ConcreteTypeHandle * ConcretizationContext<'corelib>
         =
 
         // One-dimensional arrays with lower bound 0 are also System.Array<T>
@@ -278,7 +517,7 @@ module TypeConcretization =
                 arrayTypeInfo.Assembly
                 arrayTypeInfo.Namespace
                 arrayTypeInfo.Name
-                [ elementHandle ]
+                (ImmutableArray.Create elementHandle)
         with
         | Some handle -> handle, ctx
         | None ->
@@ -289,13 +528,13 @@ module TypeConcretization =
                 (ComparableTypeDefinitionHandle.Make arrayTypeInfo.TypeDefHandle)
                 arrayTypeInfo.Namespace
                 arrayTypeInfo.Name
-                [ elementHandle ] // Array<T> has one generic parameter
+                (ImmutableArray.Create elementHandle) // Array<T> has one generic parameter
 
     let concretizeTypeDefinition
-        (ctx : ConcretizationContext)
+        (ctx : ConcretizationContext<'corelib>)
         (assemblyName : AssemblyName)
         (typeDefHandle : ComparableTypeDefinitionHandle)
-        : ConcreteTypeHandle * ConcretizationContext
+        : ConcreteTypeHandle * ConcretizationContext<'corelib>
         =
 
         // Look up the type definition in the assembly
@@ -315,19 +554,25 @@ module TypeConcretization =
                 typeInfo.Generics.Length
 
         // Check if we've already concretized this type
-        match findExistingType ctx.ConcreteTypes assemblyName typeInfo.Namespace typeInfo.Name [] with
+        match findExistingType ctx.ConcreteTypes assemblyName typeInfo.Namespace typeInfo.Name ImmutableArray.Empty with
         | Some handle -> handle, ctx
         | None ->
             // Create and add the concrete type (no generic arguments since it's not generic)
-            createAndAddConcreteType ctx assemblyName typeDefHandle typeInfo.Namespace typeInfo.Name [] // No generic parameters
+            createAndAddConcreteType
+                ctx
+                assemblyName
+                typeDefHandle
+                typeInfo.Namespace
+                typeInfo.Name
+                ImmutableArray.Empty // No generic parameters
 
     let private concretizeTypeReference
         (loadAssembly :
             AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
-        (ctx : ConcretizationContext)
+        (ctx : ConcretizationContext<'corelib>)
         (currentAssembly : AssemblyName)
         (typeRef : TypeRef)
-        : ConcreteTypeHandle * ConcretizationContext
+        : ConcreteTypeHandle * ConcretizationContext<'corelib>
         =
         // Use the helper to load assembly and resolve the type reference
         let (targetAssy, typeInfo), ctx =
@@ -346,14 +591,14 @@ module TypeConcretization =
 
     /// Concretize a type in a specific generic context
     let rec concretizeType
-        (ctx : ConcretizationContext)
+        (ctx : ConcretizationContext<'corelib>)
         (loadAssembly :
-            AssemblyName -> AssemblyReferenceHandle -> (ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly))
+            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
         (assembly : AssemblyName)
-        (typeGenerics : ConcreteTypeHandle ImmutableArray)
-        (methodGenerics : ConcreteTypeHandle ImmutableArray)
+        (typeGenerics : ImmutableArray<ConcreteTypeHandle>)
+        (methodGenerics : ImmutableArray<ConcreteTypeHandle>)
         (typeDefn : TypeDefn)
-        : ConcreteTypeHandle * ConcretizationContext
+        : ConcreteTypeHandle * ConcretizationContext<'corelib>
         =
 
         let key = (assembly, typeDefn)
@@ -382,13 +627,13 @@ module TypeConcretization =
             if index < typeGenerics.Length then
                 typeGenerics.[index], ctx
             else
-                failwithf "Generic type parameter %d out of range" index
+                raise (IndexOutOfRangeException $"Generic type parameter %i{index}")
 
         | TypeDefn.GenericMethodParameter index ->
             if index < methodGenerics.Length then
                 methodGenerics.[index], ctx
             else
-                failwithf "Generic method parameter %d out of range" index
+                raise (IndexOutOfRangeException $"Generic method parameter %i{index}")
 
         | TypeDefn.GenericInstantiation (genericDef, args) ->
             concretizeGenericInstantiation ctx loadAssembly assembly typeGenerics methodGenerics genericDef args
@@ -422,7 +667,12 @@ module TypeConcretization =
             let voidTypeInfo = ctx.BaseTypes.Void
 
             match
-                findExistingType ctx.ConcreteTypes voidTypeInfo.Assembly voidTypeInfo.Namespace voidTypeInfo.Name []
+                findExistingType
+                    ctx.ConcreteTypes
+                    voidTypeInfo.Assembly
+                    voidTypeInfo.Namespace
+                    voidTypeInfo.Name
+                    ImmutableArray.Empty
             with
             | Some handle -> handle, ctx
             | None ->
@@ -433,20 +683,20 @@ module TypeConcretization =
                     (ComparableTypeDefinitionHandle.Make voidTypeInfo.TypeDefHandle)
                     voidTypeInfo.Namespace
                     voidTypeInfo.Name
-                    [] // Void has no generic parameters
+                    ImmutableArray.Empty // Void has no generic parameters
 
         | _ -> failwithf "TODO: Concretization of %A not implemented" typeDefn
 
     and private concretizeGenericInstantiation
-        (ctx : ConcretizationContext)
+        (ctx : ConcretizationContext<'corelib>)
         (loadAssembly :
-            AssemblyName -> AssemblyReferenceHandle -> (ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly))
+            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
         (assembly : AssemblyName)
-        (typeGenerics : ConcreteTypeHandle ImmutableArray)
-        (methodGenerics : ConcreteTypeHandle ImmutableArray)
+        (typeGenerics : ImmutableArray<ConcreteTypeHandle>)
+        (methodGenerics : ImmutableArray<ConcreteTypeHandle>)
         (genericDef : TypeDefn)
         (args : ImmutableArray<TypeDefn>)
-        : ConcreteTypeHandle * ConcretizationContext
+        : ConcreteTypeHandle * ConcretizationContext<'corelib>
         =
         // First, concretize all type arguments
         let argHandles, ctxAfterArgs =
@@ -460,7 +710,7 @@ module TypeConcretization =
                 )
                 ([], ctx)
 
-        let argHandles = argHandles |> List.rev
+        let argHandles = argHandles |> Seq.rev |> ImmutableArray.CreateRange
 
         // Get the base type definition
         let baseAssembly, baseTypeDefHandle, baseNamespace, baseName, ctxAfterArgs =
@@ -597,17 +847,17 @@ module Concretization =
 
     /// Helper to concretize an array of types
     let private concretizeTypeArray
-        (ctx : TypeConcretization.ConcretizationContext)
+        (ctx : TypeConcretization.ConcretizationContext<'corelib>)
         (loadAssembly :
-            AssemblyName -> AssemblyReferenceHandle -> (ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly))
+            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
         (assembly : AssemblyName)
-        (typeArgs : ConcreteTypeHandle ImmutableArray)
-        (methodArgs : ConcreteTypeHandle ImmutableArray)
+        (typeArgs : ImmutableArray<ConcreteTypeHandle>)
+        (methodArgs : ImmutableArray<ConcreteTypeHandle>)
         (types : ImmutableArray<TypeDefn>)
-        : ImmutableArray<ConcreteTypeHandle> * TypeConcretization.ConcretizationContext
+        : ImmutableArray<ConcreteTypeHandle> * TypeConcretization.ConcretizationContext<'corelib>
         =
 
-        let handles = ImmutableArray.CreateBuilder (types.Length)
+        let handles = ImmutableArray.CreateBuilder types.Length
         let mutable ctx = ctx
 
         for i = 0 to types.Length - 1 do
@@ -621,14 +871,14 @@ module Concretization =
 
     /// Helper to concretize a method signature
     let private concretizeMethodSignature
-        (ctx : TypeConcretization.ConcretizationContext)
+        (ctx : TypeConcretization.ConcretizationContext<'corelib>)
         (loadAssembly :
-            AssemblyName -> AssemblyReferenceHandle -> (ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly))
+            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
         (assembly : AssemblyName)
-        (typeArgs : ConcreteTypeHandle ImmutableArray)
-        (methodArgs : ConcreteTypeHandle ImmutableArray)
+        (typeArgs : ImmutableArray<ConcreteTypeHandle>)
+        (methodArgs : ImmutableArray<ConcreteTypeHandle>)
         (signature : TypeMethodSignature<TypeDefn>)
-        : TypeMethodSignature<ConcreteTypeHandle> * TypeConcretization.ConcretizationContext
+        : TypeMethodSignature<ConcreteTypeHandle> * TypeConcretization.ConcretizationContext<'corelib>
         =
 
         // Concretize return type
@@ -643,7 +893,7 @@ module Concretization =
             let handle, newCtx =
                 TypeConcretization.concretizeType ctx loadAssembly assembly typeArgs methodArgs paramType
 
-            paramHandles.Add (handle)
+            paramHandles.Add handle
             ctx <- newCtx
 
         let newSignature =
@@ -660,7 +910,7 @@ module Concretization =
     /// Helper to ensure base type assembly is loaded
     let rec private ensureBaseTypeAssembliesLoaded
         (loadAssembly :
-            AssemblyName -> AssemblyReferenceHandle -> (ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly))
+            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
         (assemblies : ImmutableDictionary<string, DumpedAssembly>)
         (assyName : AssemblyName)
         (baseTypeInfo : BaseTypeInfo option)
@@ -691,12 +941,12 @@ module Concretization =
     let concretizeMethod
         (ctx : AllConcreteTypes)
         (loadAssembly :
-            AssemblyName -> AssemblyReferenceHandle -> (ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly))
+            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
         (assemblies : ImmutableDictionary<string, DumpedAssembly>)
         (baseTypes : BaseClassTypes<DumpedAssembly>)
-        (method : WoofWare.PawPrint.MethodInfo<TypeDefn, WoofWare.PawPrint.GenericParameter, TypeDefn>)
-        (typeArgs : ConcreteTypeHandle ImmutableArray)
-        (methodArgs : ConcreteTypeHandle ImmutableArray)
+        (method : WoofWare.PawPrint.MethodInfo<'ty, GenericParamFromMetadata, TypeDefn>)
+        (typeArgs : ImmutableArray<ConcreteTypeHandle>)
+        (methodArgs : ImmutableArray<ConcreteTypeHandle>)
         : WoofWare.PawPrint.MethodInfo<ConcreteTypeHandle, ConcreteTypeHandle, ConcreteTypeHandle> *
           AllConcreteTypes *
           ImmutableDictionary<string, DumpedAssembly>
@@ -826,10 +1076,9 @@ module Concretization =
         // Map generics to handles
         let genericHandles =
             method.Generics
-            |> Seq.mapi (fun i _ -> methodArgs.[i])
-            |> ImmutableArray.CreateRange
+            |> ImmutableArray.map (fun (gp, md) -> methodArgs.[gp.SequenceNumber])
 
-        let concretizedMethod : MethodInfo<_, _, ConcreteTypeHandle> =
+        let concretizedMethod : MethodInfo<_, _, _> =
             {
                 DeclaringType = concretizedDeclaringType
                 Handle = method.Handle
@@ -891,7 +1140,7 @@ module Concretization =
                 // Recursively convert generic arguments
                 let genericArgs =
                     concreteType.Generics
-                    |> List.map (fun h -> concreteHandleToTypeDefn baseClassTypes h concreteTypes assemblies)
+                    |> Seq.map (fun h -> concreteHandleToTypeDefn baseClassTypes h concreteTypes assemblies)
                     |> ImmutableArray.CreateRange
 
                 let baseDef =

WoofWare.PawPrint.Domain/TypeDefn.fs

@@ -149,6 +149,28 @@ type PrimitiveType =
         | PrimitiveType.UIntPtr -> "uintptr"
         | PrimitiveType.Object -> "obj"
 
+[<RequireQualifiedAccess>]
+module PrimitiveType =
+    let sizeOf (pt : PrimitiveType) : int =
+        match pt with
+        | PrimitiveType.Boolean -> 1
+        | PrimitiveType.Char -> 2
+        | PrimitiveType.SByte -> 1
+        | PrimitiveType.Byte -> 1
+        | PrimitiveType.Int16 -> 2
+        | PrimitiveType.UInt16 -> 2
+        | PrimitiveType.Int32 -> 4
+        | PrimitiveType.UInt32 -> 4
+        | PrimitiveType.Int64 -> 8
+        | PrimitiveType.UInt64 -> 8
+        | PrimitiveType.Single -> 4
+        | PrimitiveType.Double -> 8
+        | PrimitiveType.String -> 8
+        | PrimitiveType.TypedReference -> failwith "todo"
+        | PrimitiveType.IntPtr -> 8
+        | PrimitiveType.UIntPtr -> 8
+        | PrimitiveType.Object -> 8
+
 type TypeDefn =
     | PrimitiveType of PrimitiveType
     // TODO: array shapes

WoofWare.PawPrint.Domain/TypeInfo.fs

@@ -1,5 +1,6 @@
 namespace WoofWare.PawPrint
 
+open System
 open System.Collections.Generic
 open System.Collections.Immutable
 open System.Reflection
@@ -19,6 +20,15 @@ type MethodImplParsed =
     | MethodImplementation of MethodImplementationHandle
     | MethodDefinition of MethodDefinitionHandle
 
+type InterfaceImplementation =
+    {
+        /// TypeDefinition, TypeReference, or TypeSpecification
+        InterfaceHandle : MetadataToken
+
+        /// The assembly which InterfaceHandle is relative to
+        RelativeToAssembly : AssemblyName
+    }
+
 /// <summary>
 /// Represents detailed information about a type definition in a .NET assembly.
 /// This is a strongly-typed representation of TypeDefinition from System.Reflection.Metadata.
@@ -34,7 +44,7 @@ type TypeInfo<'generic, 'fieldGeneric> =
         /// <summary>
         /// All methods defined within this type.
         /// </summary>
-        Methods : WoofWare.PawPrint.MethodInfo<FakeUnit, WoofWare.PawPrint.GenericParameter, TypeDefn> list
+        Methods : WoofWare.PawPrint.MethodInfo<GenericParamFromMetadata, GenericParamFromMetadata, TypeDefn> list
 
         /// <summary>
         /// Method implementation mappings for this type, often used for interface implementations
@@ -45,7 +55,7 @@ type TypeInfo<'generic, 'fieldGeneric> =
         /// <summary>
         /// Fields defined in this type.
         /// </summary>
-        Fields : WoofWare.PawPrint.FieldInfo<FakeUnit, 'fieldGeneric> list
+        Fields : WoofWare.PawPrint.FieldInfo<GenericParamFromMetadata, 'fieldGeneric> list
 
         /// <summary>
         /// The base type that this type inherits from, or None for types that don't have a base type
@@ -71,6 +81,8 @@ type TypeInfo<'generic, 'fieldGeneric> =
         /// </summary>
         TypeDefHandle : TypeDefinitionHandle
 
+        DeclaringType : TypeDefinitionHandle
+
         /// <summary>
         /// The assembly in which this type is defined.
         /// </summary>
@@ -79,8 +91,23 @@ type TypeInfo<'generic, 'fieldGeneric> =
         Generics : 'generic ImmutableArray
 
         Events : EventDefn ImmutableArray
+
+        ImplementedInterfaces : InterfaceImplementation ImmutableArray
     }
 
+    member this.IsInterface = this.TypeAttributes.HasFlag TypeAttributes.Interface
+
+    member this.IsNested =
+        [
+            TypeAttributes.NestedPublic
+            TypeAttributes.NestedPrivate
+            TypeAttributes.NestedFamily
+            TypeAttributes.NestedAssembly
+            TypeAttributes.NestedFamANDAssem
+            TypeAttributes.NestedFamORAssem
+        ]
+        |> List.exists this.TypeAttributes.HasFlag
+
     override this.ToString () =
         $"%s{this.Assembly.Name}.%s{this.Namespace}.%s{this.Name}"
 
@@ -129,36 +156,47 @@ module TypeInfoCrate =
 type BaseClassTypes<'corelib> =
     {
         Corelib : 'corelib
-        String : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        Boolean : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        Char : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        SByte : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        Byte : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        Int16 : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        UInt16 : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        Int32 : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        UInt32 : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        Int64 : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        UInt64 : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        Single : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        Double : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        Array : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        Enum : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        ValueType : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        DelegateType : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        Object : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        RuntimeMethodHandle : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        RuntimeFieldHandle : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        RuntimeTypeHandle : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        RuntimeType : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        Void : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        TypedReference : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        IntPtr : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
-        UIntPtr : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
+        String : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        Boolean : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        Char : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        SByte : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        Byte : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        Int16 : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        UInt16 : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        Int32 : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        UInt32 : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        Int64 : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        UInt64 : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        Single : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        Double : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        Array : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        Enum : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        ValueType : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        DelegateType : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        Object : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        RuntimeMethodHandle : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        RuntimeFieldHandle : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        RuntimeTypeHandle : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        RuntimeFieldInfoStub : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        RuntimeFieldHandleInternal : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        RuntimeType : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        Void : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        TypedReference : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        IntPtr : TypeInfo<GenericParamFromMetadata, TypeDefn>
+        UIntPtr : TypeInfo<GenericParamFromMetadata, TypeDefn>
     }
 
 [<RequireQualifiedAccess>]
 module TypeInfo =
+    let rec fullName (get : TypeDefinitionHandle -> TypeInfo<_, _>) (ty : TypeInfo<'a, 'b>) =
+        if ty.IsNested then
+            let parent = get ty.DeclaringType |> fullName get
+            $"%s{parent}.{ty.Name}"
+        else if not (String.IsNullOrEmpty ty.Namespace) then
+            $"{ty.Namespace}.{ty.Name}"
+        else
+            ty.Name
+
     let withGenerics<'a, 'b, 'field> (gen : 'b ImmutableArray) (t : TypeInfo<'a, 'field>) : TypeInfo<'b, 'field> =
         {
             Namespace = t.Namespace
@@ -170,13 +208,15 @@ module TypeInfo =
             TypeAttributes = t.TypeAttributes
             Attributes = t.Attributes
             TypeDefHandle = t.TypeDefHandle
+            DeclaringType = t.DeclaringType
             Assembly = t.Assembly
             Generics = gen
             Events = t.Events
+            ImplementedInterfaces = t.ImplementedInterfaces
         }
 
-    let mapGeneric<'a, 'b, 'field> (f : int -> 'a -> 'b) (t : TypeInfo<'a, 'field>) : TypeInfo<'b, 'field> =
-        withGenerics (t.Generics |> Seq.mapi f |> ImmutableArray.CreateRange) t
+    let mapGeneric<'a, 'b, 'field> (f : 'a -> 'b) (t : TypeInfo<'a, 'field>) : TypeInfo<'b, 'field> =
+        withGenerics (t.Generics |> ImmutableArray.map f) t
 
     let internal read
         (loggerFactory : ILoggerFactory)
@@ -184,9 +224,10 @@ module TypeInfo =
         (thisAssembly : AssemblyName)
         (metadataReader : MetadataReader)
         (typeHandle : TypeDefinitionHandle)
-        : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
+        : TypeInfo<GenericParamFromMetadata, TypeDefn>
         =
         let typeDef = metadataReader.GetTypeDefinition typeHandle
+        let declaringType = typeDef.GetDeclaringType ()
         let methods = typeDef.GetMethods ()
 
         let methodImpls =
@@ -253,6 +294,20 @@ module TypeInfo =
 
             result.ToImmutable ()
 
+        let interfaces =
+            let result = ImmutableArray.CreateBuilder ()
+
+            for i in typeDef.GetInterfaceImplementations () do
+                let impl = metadataReader.GetInterfaceImplementation i
+
+                {
+                    InterfaceHandle = MetadataToken.ofEntityHandle impl.Interface
+                    RelativeToAssembly = thisAssembly
+                }
+                |> result.Add
+
+            result.ToImmutable ()
+
         {
             Namespace = ns
             Name = name
@@ -266,6 +321,8 @@ module TypeInfo =
             Assembly = thisAssembly
             Generics = genericParams
             Events = events
+            ImplementedInterfaces = interfaces
+            DeclaringType = declaringType
         }
 
     let isBaseType<'corelib>
@@ -323,7 +380,7 @@ module TypeInfo =
                 (Some (BaseTypeInfo.TypeDef typeDefinitionHandle))
 
     let toTypeDefn
-        (corelib : BaseClassTypes<'corelib>)
+        (baseClassTypes : BaseClassTypes<'corelib>)
         (getName : 'corelib -> AssemblyName)
         (getTypeDef : 'corelib -> TypeDefinitionHandle -> TypeInfo<'generic, 'field>)
         (getTypeRef : 'corelib -> TypeReferenceHandle -> TypeInfo<'generic, 'field>)
@@ -331,7 +388,7 @@ module TypeInfo =
         : TypeDefn
         =
         let stk =
-            match resolveBaseType corelib getName getTypeDef getTypeRef ty.Assembly ty.BaseType with
+            match resolveBaseType baseClassTypes getName getTypeDef getTypeRef ty.Assembly ty.BaseType with
             | ResolvedBaseType.Enum
             | ResolvedBaseType.ValueType -> SignatureTypeKind.ValueType
             | ResolvedBaseType.Object

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

@@ -7,13 +7,16 @@
 
     <ItemGroup>
         <Compile Include="StringToken.fs" />
+        <Compile Include="ImmutableArray.fs" />
         <Compile Include="Tokens.fs" />
         <Compile Include="TypeRef.fs" />
         <Compile Include="IlOp.fs" />
         <Compile Include="CustomAttribute.fs" />
+        <Compile Include="GenericParameter.fs" />
         <Compile Include="AssemblyReference.fs" />
         <Compile Include="EventDefn.fs" />
         <Compile Include="ComparableTypeDefinitionHandle.fs" />
+        <Compile Include="ComparableFieldDefinitionHandle.fs" />
         <Compile Include="ComparableSignatureHeader.fs" />
         <Compile Include="TypeDefn.fs" />
         <Compile Include="ConcreteType.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.Information
+        let isEnabled (logLevel : LogLevel) : bool = logLevel >= LogLevel.Debug
 
         let createLogger (category : string) : ILogger =
             { new ILogger with

WoofWare.PawPrint.Test/TestHarness.fs

@@ -25,10 +25,9 @@ module MockEnv =
             System_Threading_Monitor = System_Threading_MonitorMock.Empty
         }
 
-type TestCase =
+type EndToEndTestCase =
     {
         FileName : string
         ExpectedReturnCode : int
         NativeImpls : NativeImpls
-        LocalVariablesOfMain : CliType list option
     }

WoofWare.PawPrint.Test/TestImpureCases.fs

@@ -20,11 +20,10 @@ module TestImpureCases =
                 FileName = "WriteLine.cs"
                 ExpectedReturnCode = 1
                 NativeImpls = NativeImpls.PassThru ()
-                LocalVariablesOfMain = [] |> Some
             }
         ]
 
-    let cases : TestCase list =
+    let cases : EndToEndTestCase list =
         [
             {
                 FileName = "InstaQuit.cs"
@@ -47,12 +46,10 @@ module TestImpureCases =
                                         ExecutionResult.Terminated (state, thread)
                             }
                     }
-                LocalVariablesOfMain = [] |> Some
             }
         ]
 
-    [<TestCaseSource(nameof cases)>]
-    let ``Can evaluate C# files`` (case : TestCase) : unit =
+    let runTest (case : EndToEndTestCase) : unit =
         let source = Assembly.getEmbeddedResourceAsString case.FileName assy
         let image = Roslyn.compile [ source ]
         let messages, loggerFactory = LoggerFactory.makeTest ()
@@ -75,15 +72,6 @@ module TestImpureCases =
                     | ret -> failwith $"expected program to return an int, but it returned %O{ret}"
 
             exitCode |> shouldEqual case.ExpectedReturnCode
-
-            let finalVariables =
-                terminalState.ThreadState.[terminatingThread].MethodState.LocalVariables
-                |> Seq.toList
-
-            match case.LocalVariablesOfMain with
-            | None -> ()
-            | Some expected -> finalVariables |> shouldEqual expected
-
         with _ ->
             for message in messages () do
                 System.Console.Error.WriteLine $"{message}"
@@ -91,33 +79,8 @@ module TestImpureCases =
             reraise ()
 
     [<TestCaseSource(nameof unimplemented)>]
-    [<Explicit "not yet implemented">]
-    let ``Can evaluate C# files, unimplemented`` (case : TestCase) : unit =
-        let source = Assembly.getEmbeddedResourceAsString case.FileName assy
-        let image = Roslyn.compile [ source ]
-        let messages, loggerFactory = LoggerFactory.makeTest ()
+    [<Explicit>]
+    let ``Can evaluate C# files, unimplemented`` (case : EndToEndTestCase) = runTest case
 
-        let dotnetRuntimes =
-            DotnetRuntime.SelectForDll assy.Location |> ImmutableArray.CreateRange
-
-        use peImage = new MemoryStream (image)
-
-        try
-            let terminalState, terminatingThread =
-                Program.run loggerFactory (Some case.FileName) peImage dotnetRuntimes case.NativeImpls []
-
-            let exitCode =
-                match terminalState.ThreadState.[terminatingThread].MethodState.EvaluationStack.Values with
-                | [] -> failwith "expected program to return a value, but it returned void"
-                | head :: _ ->
-                    match head with
-                    | EvalStackValue.Int32 i -> i
-                    | ret -> failwith $"expected program to return an int, but it returned %O{ret}"
-
-            exitCode |> shouldEqual case.ExpectedReturnCode
-
-        with _ ->
-            for message in messages () do
-                System.Console.Error.WriteLine $"{message}"
-
-            reraise ()
+    [<TestCaseSource(nameof cases)>]
+    let ``Can evaluate C# files`` (case : EndToEndTestCase) = runTest case

WoofWare.PawPrint.Test/TestPureCases.fs

@@ -20,119 +20,80 @@ module TestPureCases =
                 FileName = "CrossAssemblyTypes.cs"
                 ExpectedReturnCode = 0
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain = None
+            }
+            {
+                FileName = "InitializeArray.cs"
+                ExpectedReturnCode = 0
+                NativeImpls = MockEnv.make ()
             }
             {
                 FileName = "GenericEdgeCases.cs"
                 ExpectedReturnCode = 0
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain = None
-            }
-            {
-                FileName = "TestShl.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain = None
-            }
-            {
-                FileName = "TestShr.cs"
-                ExpectedReturnCode = 0
-                NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain = None
             }
             {
                 FileName = "Threads.cs"
                 ExpectedReturnCode = 3
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain = [] |> Some
             }
             {
                 FileName = "ComplexTryCatch.cs"
                 ExpectedReturnCode = 14
                 NativeImpls = NativeImpls.PassThru ()
-                LocalVariablesOfMain =
-                    [
-                        4
-                        20
-                        115
-                        12
-                        1
-                        10
-                        2
-                        112
-                        12
-                        1111
-                        42
-                        99
-                        25
-                        50
-                        123
-                        20
-                        35
-                        5
-                        11111
-                        100001
-                    ]
-                    |> List.map (fun i -> CliType.Numeric (CliNumericType.Int32 i))
-                    |> Some
             }
             {
                 FileName = "ResizeArray.cs"
                 ExpectedReturnCode = 109
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain = [ CliType.Numeric (CliNumericType.Int32 10) ] |> Some
+            }
+            {
+                FileName = "Sizeof.cs"
+                ExpectedReturnCode = 0
+                NativeImpls = MockEnv.make ()
+            }
+            {
+                FileName = "LdtokenField.cs"
+                ExpectedReturnCode = 0
+                NativeImpls = MockEnv.make ()
             }
         ]
 
-    let cases : TestCase list =
+    let cases : EndToEndTestCase list =
         [
             {
                 FileName = "NoOp.cs"
                 ExpectedReturnCode = 1
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain = [ CliType.Numeric (CliNumericType.Int32 1) ] |> Some
+            }
+            {
+                FileName = "TestShl.cs"
+                ExpectedReturnCode = 0
+                NativeImpls = MockEnv.make ()
+            }
+            {
+                FileName = "TestShr.cs"
+                ExpectedReturnCode = 0
+                NativeImpls = MockEnv.make ()
             }
             {
                 FileName = "StaticVariables.cs"
                 ExpectedReturnCode = 0
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain = None
             }
             {
                 FileName = "Ldind.cs"
                 ExpectedReturnCode = 0
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain =
-                    [
-                        // `failures`
-                        CliType.Numeric (CliNumericType.Int32 0)
-                        // Return value
-                        CliType.Numeric (CliNumericType.Int32 0)
-                    ]
-                    |> Some
             }
             {
                 FileName = "CustomDelegate.cs"
                 ExpectedReturnCode = 8
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain =
-                    [
-                        // filter
-                        CliType.ObjectRef (Some (ManagedHeapAddress 2))
-                        // result
-                        CliType.OfBool true
-                        // result, cloned for "if(result)" check
-                        CliType.OfBool true
-                        // ret
-                        CliType.Numeric (CliNumericType.Int32 8)
-                    ]
-                    |> Some
             }
             {
                 FileName = "ArgumentOrdering.cs"
                 ExpectedReturnCode = 0
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain = None
             }
             {
                 FileName = "BasicLock.cs"
@@ -143,97 +104,55 @@ module TestPureCases =
                     { mock with
                         System_Threading_Monitor = System_Threading_Monitor.passThru
                     }
-                LocalVariablesOfMain =
-                    [
-                        // Four variables:
-                        // locker
-                        CliType.ObjectRef (Some (ManagedHeapAddress 2))
-                        // a copy of locker, taken so that the contents of the implicit `finally` have a stable copy
-                        CliType.ObjectRef (Some (ManagedHeapAddress 2))
-                        // out param of `ReliableEnter`
-                        CliType.OfBool true
-                        // return value
-                        CliType.Numeric (CliNumericType.Int32 1)
-                    ]
-                    |> Some
             }
             {
                 FileName = "TriangleNumber.cs"
                 ExpectedReturnCode = 10
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain =
-                    [
-                        // answer
-                        CliType.Numeric (CliNumericType.Int32 10)
-                        // i
-                        CliType.Numeric (CliNumericType.Int32 5)
-                        // End-loop condition
-                        CliType.OfBool false
-                        // Ret
-                        CliType.Numeric (CliNumericType.Int32 10)
-                    ]
-                    |> Some
             }
             {
                 FileName = "ExceptionWithNoOpFinally.cs"
                 ExpectedReturnCode = 3
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain =
-                    [
-                        // Variable 1 is `x`, variable 2 is the implicit return value
-                        4
-                        3
-                    ]
-                    |> List.map (fun i -> CliType.Numeric (CliNumericType.Int32 i))
-                    |> Some
             }
             {
                 FileName = "ExceptionWithNoOpCatch.cs"
                 ExpectedReturnCode = 10
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain = [ CliType.Numeric (CliNumericType.Int32 10) ] |> Some
             }
             {
                 FileName = "Floats.cs"
                 ExpectedReturnCode = 0
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain = None
             }
             {
                 FileName = "TryCatchWithThrowInBody.cs"
                 ExpectedReturnCode = 4
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain =
-                    [
-                        // one variable is x, one variable is the return value which also happens to have the same value
-                        4
-                        4
-                    ]
-                    |> List.map (fun i -> CliType.Numeric (CliNumericType.Int32 i))
-                    |> Some
             }
             {
                 FileName = "Ldelema.cs"
                 ExpectedReturnCode = 0
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain = None
             }
             {
                 FileName = "TypeConcretization.cs"
                 ExpectedReturnCode = 0
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain = None
             }
             {
                 FileName = "TestOr.cs"
                 ExpectedReturnCode = 0
                 NativeImpls = MockEnv.make ()
-                LocalVariablesOfMain = None
+            }
+            {
+                FileName = "InterfaceDispatch.cs"
+                ExpectedReturnCode = 0
+                NativeImpls = MockEnv.make ()
             }
         ]
 
-    [<TestCaseSource(nameof cases)>]
-    let ``Can evaluate C# files`` (case : TestCase) : unit =
+    let runTest (case : EndToEndTestCase) : unit =
         let source = Assembly.getEmbeddedResourceAsString case.FileName assy
         let image = Roslyn.compile [ source ]
         let messages, loggerFactory = LoggerFactory.makeTest ()
@@ -260,14 +179,6 @@ module TestPureCases =
             exitCode |> shouldEqual realResult.ExitCode
 
             exitCode |> shouldEqual case.ExpectedReturnCode
-
-            let finalVariables =
-                terminalState.ThreadState.[terminatingThread].MethodState.LocalVariables
-                |> Seq.toList
-
-            match case.LocalVariablesOfMain with
-            | None -> ()
-            | Some expected -> finalVariables |> shouldEqual expected
         with _ ->
             for message in messages () do
                 System.Console.Error.WriteLine $"{message}"
@@ -275,33 +186,8 @@ module TestPureCases =
             reraise ()
 
     [<TestCaseSource(nameof unimplemented)>]
-    [<Explicit "not yet implemented">]
-    let ``Can evaluate C# files, unimplemented`` (case : TestCase) : unit =
-        let source = Assembly.getEmbeddedResourceAsString case.FileName assy
-        let image = Roslyn.compile [ source ]
-        let messages, loggerFactory = LoggerFactory.makeTest ()
+    [<Explicit>]
+    let ``Can evaluate C# files, unimplemented`` (case : EndToEndTestCase) = runTest case
 
-        let dotnetRuntimes =
-            DotnetRuntime.SelectForDll assy.Location |> ImmutableArray.CreateRange
-
-        use peImage = new MemoryStream (image)
-
-        try
-            let terminalState, terminatingThread =
-                Program.run loggerFactory (Some case.FileName) peImage dotnetRuntimes case.NativeImpls []
-
-            let exitCode =
-                match terminalState.ThreadState.[terminatingThread].MethodState.EvaluationStack.Values with
-                | [] -> failwith "expected program to return a value, but it returned void"
-                | head :: _ ->
-                    match head with
-                    | EvalStackValue.Int32 i -> i
-                    | ret -> failwith $"expected program to return an int, but it returned %O{ret}"
-
-            exitCode |> shouldEqual case.ExpectedReturnCode
-
-        with _ ->
-            for message in messages () do
-                System.Console.Error.WriteLine $"{message}"
-
-            reraise ()
+    [<TestCaseSource(nameof cases)>]
+    let ``Can evaluate C# files`` (case : EndToEndTestCase) = runTest case

WoofWare.PawPrint.Test/WoofWare.PawPrint.Test.fsproj

@@ -4,9 +4,6 @@
     <TargetFramework>net9.0</TargetFramework>
     <IsPackable>false</IsPackable>
     <OutputType>Exe</OutputType>
-    <IsTestProject>true</IsTestProject>
-    <TestingPlatformDotnetTestSupport>true</TestingPlatformDotnetTestSupport>
-    <EnableNUnitRunner>true</EnableNUnitRunner>
   </PropertyGroup>
 
   <ItemGroup>
@@ -19,31 +16,8 @@
     <Compile Include="TestImpureCases.fs" />
   </ItemGroup>
   <ItemGroup>
-    <EmbeddedResource Include="sourcesPure\BasicLock.cs" />
-    <EmbeddedResource Include="sourcesPure\Floats.cs" />
-    <EmbeddedResource Include="sourcesPure\NoOp.cs" />
-    <EmbeddedResource Include="sourcesPure\StaticVariables.cs" />
-    <EmbeddedResource Include="sourcesPure\Ldelema.cs" />
-    <EmbeddedResource Include="sourcesPure\ExceptionWithNoOpCatch.cs" />
-    <EmbeddedResource Include="sourcesPure\ExceptionWithNoOpFinally.cs" />
-    <EmbeddedResource Include="sourcesPure\TryCatchWithThrowInBody.cs" />
-    <EmbeddedResource Include="sourcesPure\ComplexTryCatch.cs" />
-    <EmbeddedResource Include="sourcesPure\TriangleNumber.cs" />
-    <EmbeddedResource Include="sourcesPure\Threads.cs" />
-    <EmbeddedResource Include="sourcesPure\ResizeArray.cs" />
-    <EmbeddedResource Include="sourcesPure\ArgumentOrdering.cs" />
-    <EmbeddedResource Include="sourcesPure\TestShl.cs" />
-    <EmbeddedResource Include="sourcesPure\TestShr.cs" />
-    <EmbeddedResource Include="sourcesPure\TestOr.cs" />
-    <EmbeddedResource Include="sourcesPure\CustomDelegate.cs" />
-    <EmbeddedResource Include="sourcesPure\Ldind.cs" />
-    <EmbeddedResource Include="sourcesPure\TypeConcretization.cs" />
-    <EmbeddedResource Include="sourcesPure\CrossAssemblyTypes.cs" />
-    <EmbeddedResource Include="sourcesPure\GenericEdgeCases.cs" />
-  </ItemGroup>
-  <ItemGroup>
-    <EmbeddedResource Include="sourcesImpure\WriteLine.cs" />
-    <EmbeddedResource Include="sourcesImpure\InstaQuit.cs" />
+    <EmbeddedResource Include="sourcesPure\*.cs" />
+    <EmbeddedResource Include="sourcesImpure\*.cs" />
   </ItemGroup>
 
   <ItemGroup>
@@ -51,10 +25,10 @@
   </ItemGroup>
 
   <ItemGroup>
+    <PackageReference Include="NUnit" Version="4.4.0"/>
+    <PackageReference Include="NUnit3TestAdapter" Version="5.1.0"/>
     <PackageReference Include="FsUnit" Version="7.1.1"/>
-    <PackageReference Include="NUnit3TestAdapter" Version="5.0.0"/>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1"/>
-    <PackageReference Include="NUnit" Version="4.3.2"/>
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.14.0"/>
     <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="9.0.6" />
     <PackageReference Include="WoofWare.DotnetRuntimeLocator" Version="0.3.2"/>

WoofWare.PawPrint.Test/sourcesPure/InitializeArray.cs

@@ -0,0 +1,19 @@
+using System.Linq;
+
+namespace HelloWorldApp
+{
+    class Program
+    {
+        static int Main(string[] args)
+        {
+            int[] array = new[] { 1, 2, 3 };
+
+            if (array.Sum() != 60)
+            {
+                return 1;
+            }
+
+            return 0;
+        }
+    }
+}

WoofWare.PawPrint.Test/sourcesPure/InterfaceDispatch.cs

@@ -0,0 +1,339 @@
+using System;
+
+public class InterfaceDispatchTests
+{
+    public static int Main(string[] argv)
+    {
+        int result = 0;
+
+        result |= TestBasicInterface();
+        result |= TestExplicitImplementation() << 1;
+        result |= TestMultipleInterfaces() << 2;
+        result |= TestInterfaceInheritance() << 3;
+        result |= TestDiamondInheritance() << 4;
+        result |= TestGenericInterface() << 5;
+        result |= TestCovariantInterface() << 6;
+        result |= TestReimplementation() << 7;
+        // TODO
+        /*
+        result |= TestStructInterface() << 8;
+        result |= TestNullDispatch() << 9;
+        */
+        result |= TestSharedMethodSignature() << 10;
+
+        return result;
+    }
+
+    // Test 1: Basic interface dispatch
+    static int TestBasicInterface()
+    {
+        ISimple obj = new SimpleImpl();
+        return obj.GetValue() == 42 ? 0 : 1;
+    }
+
+    // Test 2: Explicit interface implementation
+    static int TestExplicitImplementation()
+    {
+        var obj = new ExplicitImpl();
+        IExplicit iface = obj;
+
+        // Direct call should return 10, interface call should return 20
+        if (obj.GetValue() != 10) return 1;
+        if (iface.GetValue() != 20) return 1;
+
+        return 0;
+    }
+
+    // Test 3: Multiple interfaces
+    static int TestMultipleInterfaces()
+    {
+        var obj = new MultiImpl();
+        IFirst first = obj;
+        ISecond second = obj;
+
+        if (first.GetFirst() != 1) return 1;
+        if (second.GetSecond() != 2) return 1;
+
+        return 0;
+    }
+
+    // Test 4: Interface inheritance
+    static int TestInterfaceInheritance()
+    {
+        IDerived obj = new DerivedImpl();
+        IBase baseIface = obj;
+
+        if (baseIface.GetBase() != 100) return 1;
+        if (obj.GetDerived() != 200) return 1;
+
+        return 0;
+    }
+
+    // Test 5: Diamond inheritance pattern
+    static int TestDiamondInheritance()
+    {
+        var obj = new DiamondImpl();
+        ILeft left = obj;
+        IRight right = obj;
+        IDiamond diamond = obj;
+
+        if (left.GetValue() != 300) return 1;
+        if (right.GetValue() != 300) return 1;
+        if (diamond.GetDiamondValue() != 400) return 1;
+
+        return 0;
+    }
+
+    // Test 6: Generic interface dispatch
+    static int TestGenericInterface()
+    {
+        IGeneric<int> intObj = new GenericImpl<int>();
+        IGeneric<string> strObj = new GenericImpl<string>();
+
+        if (intObj.Process(5) != 3) return 1;
+        if (strObj.Process("test") != 5) return 1;
+
+        return 0;
+    }
+
+    // Test 7: Covariant interface dispatch
+    static int TestCovariantInterface()
+    {
+        ICovariant<string> strCov = new CovariantImpl();
+        ICovariant<object> objCov = strCov; // Covariance allows this
+
+        object result = objCov.Get();
+        if (!(result is string s && s == "covariant")) return 1;
+
+        return 0;
+    }
+
+    // Test 8: Interface reimplementation in derived class
+    static int TestReimplementation()
+    {
+        BaseClass baseObj = new DerivedClass();
+        IReimpl iface = baseObj;
+
+        // Should call derived implementation
+        if (iface.Method() != 500) return 1;
+
+        // Now test with base reference
+        BaseClass pureBase = new BaseClass();
+        IReimpl baseIface = pureBase;
+        if (baseIface.Method() != 600) return 1;
+
+        return 0;
+    }
+
+    // Test 9: Struct implementing interface
+    static int TestStructInterface()
+    {
+        StructImpl s = new StructImpl { Value = 700 };
+        ISimple boxed = s; // Boxing happens here
+
+        if (boxed.GetValue() != 700) return 1;
+
+        // Verify boxing created a copy
+        s.Value = 800;
+        if (boxed.GetValue() != 700) return 1; // Should still be 700
+
+        return 0;
+    }
+
+    // Test 10: Null dispatch (should throw)
+    static int TestNullDispatch()
+    {
+        ISimple nullRef = null;
+        try
+        {
+            nullRef.GetValue();
+            return 1; // Should have thrown
+        }
+        catch (NullReferenceException)
+        {
+            return 0; // Expected
+        }
+    }
+
+    // Test 11: Same method signature on multiple unrelated interfaces
+    static int TestSharedMethodSignature()
+    {
+        var obj = new SharedMethodImpl();
+        IReader reader = obj;
+        IScanner scanner = obj;
+
+        // Both interfaces should be satisfied by the single implementation
+        if (reader.Read() != "shared") return 1;
+        if (scanner.Read() != "shared") return 1;
+
+        // Also test with explicit + implicit combination
+        var mixed = new MixedSharedImpl();
+        IReader readerMixed = mixed;
+        IScanner scannerMixed = mixed;
+
+        if (readerMixed.Read() != "explicit-reader") return 1;
+        if (scannerMixed.Read() != "implicit-scanner") return 1;
+        if (mixed.Read() != "implicit-scanner") return 1; // Public method
+
+        return 0;
+    }
+
+    // Test interfaces and implementations
+
+    interface ISimple
+    {
+        int GetValue();
+    }
+
+    class SimpleImpl : ISimple
+    {
+        public int GetValue() => 42;
+    }
+
+    interface IExplicit
+    {
+        int GetValue();
+    }
+
+    class ExplicitImpl : IExplicit
+    {
+        public int GetValue() => 10;
+        int IExplicit.GetValue() => 20;
+    }
+
+    interface IFirst
+    {
+        int GetFirst();
+    }
+
+    interface ISecond
+    {
+        int GetSecond();
+    }
+
+    class MultiImpl : IFirst, ISecond
+    {
+        public int GetFirst() => 1;
+        public int GetSecond() => 2;
+    }
+
+    interface IBase
+    {
+        int GetBase();
+    }
+
+    interface IDerived : IBase
+    {
+        int GetDerived();
+    }
+
+    class DerivedImpl : IDerived
+    {
+        public int GetBase() => 100;
+        public int GetDerived() => 200;
+    }
+
+    interface ICommon
+    {
+        int GetValue();
+    }
+
+    interface ILeft : ICommon
+    {
+    }
+
+    interface IRight : ICommon
+    {
+    }
+
+    interface IDiamond : ILeft, IRight
+    {
+        int GetDiamondValue();
+    }
+
+    class DiamondImpl : IDiamond
+    {
+        public int GetValue() => 300;
+        public int GetDiamondValue() => 400;
+    }
+
+    interface IGeneric<T>
+    {
+        int Process(T value);
+    }
+
+    class GenericImpl<T> : IGeneric<T>
+    {
+        public int Process(T value)
+        {
+            if (typeof(T) == typeof(int))
+            {
+                return 3;
+            }
+
+            if (typeof(T) == typeof(string))
+            {
+                return 5;
+            }
+
+            return 0;
+        }
+    }
+
+    interface ICovariant<out T>
+    {
+        T Get();
+    }
+
+    class CovariantImpl : ICovariant<string>
+    {
+        public string Get() => "covariant";
+    }
+
+    interface IReimpl
+    {
+        int Method();
+    }
+
+    class BaseClass : IReimpl
+    {
+        public virtual int Method() => 600;
+    }
+
+    class DerivedClass : BaseClass, IReimpl
+    {
+        public override int Method() => 500;
+    }
+
+    struct StructImpl : ISimple
+    {
+        public int Value;
+        public int GetValue() => Value;
+    }
+
+    interface IReader
+    {
+        string Read();
+    }
+
+    interface IScanner
+    {
+        string Read();  // Same signature as IReader.Read()
+    }
+
+    // Single implicit implementation satisfies both interfaces
+    class SharedMethodImpl : IReader, IScanner
+    {
+        public string Read() => "shared";
+    }
+
+    // Mixed: explicit for one, implicit for the other
+    class MixedSharedImpl : IReader, IScanner
+    {
+        // Explicit implementation for IReader
+        string IReader.Read() => "explicit-reader";
+
+        // Implicit implementation (public) - satisfies IScanner
+        public string Read() => "implicit-scanner";
+    }
+}

WoofWare.PawPrint.Test/sourcesPure/Ldind.cs

@@ -39,7 +39,7 @@ unsafe class LdindTest
         failures += TestTruncation();
 
         // Test with managed pointers (ref)
-        // failures += TestManagedPointers();
+        failures += TestManagedPointers();
 
         // Test Ldind.i (native int)
         failures += TestLdindI();
@@ -325,7 +325,10 @@ unsafe class LdindTest
         }
 
         // Test with array element
-        int[] array = { 10, 20, 30 };
+        int[] array = new int[3];
+        array[0] = 10;
+        array[1] = 20;
+        array[2] = 30;
         ref int element = ref array[1];
         if (element != 20)
         {

WoofWare.PawPrint.Test/sourcesPure/LdtokenField.cs

@@ -0,0 +1,128 @@
+using System;
+using System.Linq;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+
+namespace LdtokenFieldTest
+{
+    class Program
+    {
+        // Various field types to test ldtoken with
+        public static int StaticIntField = 42;
+        public string InstanceStringField = "test";
+        private readonly double PrivateReadonlyField = 3.14;
+        internal decimal InternalField;
+        protected bool ProtectedField;
+        public static readonly DateTime StaticReadonlyField = DateTime.MinValue;
+
+        // Generic type fields
+        public GenericClass<int>.NestedClass<string> GenericField;
+
+        static int Main(string[] args)
+        {
+            int testsFailed = 0;
+
+            // Test 1: Static field via FieldInfo
+            FieldInfo staticField = typeof(Program).GetField(nameof(StaticIntField));
+            if (staticField == null || staticField.FieldType != typeof(int))
+            {
+                testsFailed++;
+            }
+
+            // Test 2: Instance field via FieldInfo
+            FieldInfo instanceField = typeof(Program).GetField(nameof(InstanceStringField));
+            if (instanceField == null || instanceField.FieldType != typeof(string))
+            {
+                testsFailed++;
+            }
+
+            // Test 3: Private field via FieldInfo with binding flags
+            FieldInfo privateField = typeof(Program).GetField("PrivateReadonlyField",
+                BindingFlags.NonPublic | BindingFlags.Instance);
+            if (privateField == null || privateField.FieldType != typeof(double))
+            {
+                testsFailed++;
+            }
+
+            // Test 4: Using RuntimeFieldHandle directly
+            RuntimeFieldHandle handle = staticField.FieldHandle;
+            FieldInfo fieldFromHandle = FieldInfo.GetFieldFromHandle(handle);
+            if (!ReferenceEquals(fieldFromHandle, staticField))
+            {
+                testsFailed++;
+            }
+
+            // Test 5: Field from generic type
+            Type genericType = typeof(GenericClass<>);
+            FieldInfo genericFieldInfo = genericType.GetField("GenericField");
+            if (genericFieldInfo == null)
+            {
+                testsFailed++;
+            }
+
+            // Test 6: Field from nested type
+            Type nestedType = typeof(OuterClass.InnerClass);
+            FieldInfo nestedField = nestedType.GetField("NestedField");
+            if (nestedField == null || nestedField.FieldType != typeof(int))
+            {
+                testsFailed++;
+            }
+
+            // Test 7: Field handle with generic context
+            Type constructedGeneric = typeof(GenericClass<int>);
+            FieldInfo constructedField = constructedGeneric.GetField("GenericField");
+            RuntimeFieldHandle genericHandle = constructedField.FieldHandle;
+            FieldInfo reconstructed = FieldInfo.GetFieldFromHandle(genericHandle, constructedGeneric.TypeHandle);
+            if (reconstructed.DeclaringType != constructedGeneric)
+            {
+                testsFailed++;
+            }
+
+            // Test 8: Struct field
+            Type structType = typeof(TestStruct);
+            FieldInfo structField = structType.GetField("StructField");
+            if (structField == null || structField.FieldType != typeof(long))
+            {
+                testsFailed++;
+            }
+
+            // Test 9: Volatile field
+            FieldInfo volatileField = typeof(VolatileFieldClass).GetField("VolatileField");
+            if (volatileField == null || !volatileField.GetRequiredCustomModifiers().Any(t => t == typeof(IsVolatile)))
+            {
+                testsFailed++;
+            }
+
+            return testsFailed;
+        }
+    }
+
+    // Supporting types for testing
+    public class GenericClass<T>
+    {
+        public T GenericField;
+
+        public class NestedClass<U>
+        {
+            public U NestedGenericField;
+        }
+    }
+
+    public class OuterClass
+    {
+        public class InnerClass
+        {
+            public int NestedField = 100;
+        }
+    }
+
+    public struct TestStruct
+    {
+        public long StructField;
+    }
+
+    public class VolatileFieldClass
+    {
+        public volatile int VolatileField;
+    }
+}

WoofWare.PawPrint.Test/sourcesPure/Sizeof.cs

@@ -0,0 +1,118 @@
+using System;
+using System.Runtime.InteropServices;
+
+unsafe public class Program
+{
+    public struct SmallStruct
+    {
+        public byte Value;
+    }
+
+    public struct MediumStruct
+    {
+        public int Value1;
+        public int Value2;
+    }
+
+    public struct LargeStruct
+    {
+        public long Value1;
+        public long Value2;
+        public long Value3;
+        public long Value4;
+    }
+
+    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: Pointer types
+        unsafe
+        {
+            if (sizeof(IntPtr) != sizeof(void*)) return 19;
+            if (sizeof(UIntPtr) != sizeof(void*)) return 20;
+        }
+
+        // Test 7: Using sizeof in expressions
+        int totalSize = sizeof(int) + sizeof(long) + sizeof(byte);
+        if (totalSize != 13) return 21;
+
+        // Test 8: Array element size calculation
+        int arrayElementSize = sizeof(MediumStruct);
+        int arraySize = arrayElementSize * 3;
+        if (arraySize != 24) return 22;
+
+        // Test 9: Conditional using sizeof
+        bool is32Bit = sizeof(IntPtr) == 4;
+        bool is64Bit = sizeof(IntPtr) == 8;
+        if (!is32Bit && !is64Bit) return 23;
+        if (is32Bit && is64Bit) return 24;
+
+        // Test 10: Sizeof in switch statement
+        int result = 0;
+        switch (sizeof(int))
+        {
+            case 1:
+                result = 1;
+                break;
+            case 2:
+                result = 2;
+                break;
+            case 4:
+                result = 4;
+                break;
+            case 8:
+                result = 8;
+                break;
+            default:
+                result = -1;
+                break;
+        }
+        if (result != 4) return 25;
+
+        return 0;
+    }
+}

WoofWare.PawPrint/AbstractMachine.fs

@@ -103,13 +103,14 @@ module AbstractMachine =
                     let currentThreadState = state.ThreadState.[thread]
 
                     let state =
-                        IlMachineState.callMethod
+                        IlMachineStateExecution.callMethod
                             loggerFactory
                             baseClassTypes
                             None
                             constructing
                             false
                             false
+                            false
                             methodGenerics
                             methodPtr
                             thread
@@ -125,42 +126,55 @@ module AbstractMachine =
                     targetType.Namespace,
                     targetType.Name,
                     instruction.ExecutingMethod.Name,
-                    instruction.ExecutingMethod.RawSignature.ParameterTypes,
-                    instruction.ExecutingMethod.RawSignature.ReturnType
+                    instruction.ExecutingMethod.Signature.ParameterTypes,
+                    instruction.ExecutingMethod.Signature.ReturnType
                 with
                 | "System.Private.CoreLib",
                   "System",
                   "Environment",
                   "GetProcessorCount",
                   [],
-                  TypeDefn.PrimitiveType PrimitiveType.Int32 ->
+                  ConcretePrimitive state.ConcreteTypes PrimitiveType.Int32 ->
                     let env = ISystem_Environment_Env.get impls
                     env.GetProcessorCount thread state
                 | "System.Private.CoreLib",
                   "System",
                   "Environment",
                   "_Exit",
-                  [ TypeDefn.PrimitiveType PrimitiveType.Int32 ],
-                  TypeDefn.Void ->
+                  [ ConcretePrimitive state.ConcreteTypes PrimitiveType.Int32 ],
+                  ConcreteVoid state.ConcreteTypes ->
                     let env = ISystem_Environment_Env.get impls
                     env._Exit thread state
                 | "System.Private.CoreLib",
                   "System.Threading",
                   "Monitor",
                   "ReliableEnter",
-                  [ TypeDefn.PrimitiveType PrimitiveType.Object
-                    TypeDefn.Byref (TypeDefn.PrimitiveType PrimitiveType.Boolean) ],
-                  TypeDefn.Void ->
+                  [ ConcretePrimitive state.ConcreteTypes PrimitiveType.Object
+                    ConcreteByref (ConcretePrimitive state.ConcreteTypes PrimitiveType.Boolean) ],
+                  ConcreteVoid state.ConcreteTypes ->
                     let env = ISystem_Threading_Monitor_Env.get impls
                     env.ReliableEnter thread state
                 | "System.Private.CoreLib",
                   "System.Threading",
                   "Monitor",
                   "Exit",
-                  [ TypeDefn.PrimitiveType PrimitiveType.Object ],
-                  TypeDefn.Void ->
+                  [ ConcretePrimitive state.ConcreteTypes PrimitiveType.Object ],
+                  ConcreteVoid state.ConcreteTypes ->
                     let env = ISystem_Threading_Monitor_Env.get impls
                     env.Exit thread state
+                | "System.Private.CoreLib",
+                  "System",
+                  "Type",
+                  "GetField",
+                  [ ConcretePrimitive state.ConcreteTypes PrimitiveType.String ; ty ],
+                  ret ->
+                    let ty = AllConcreteTypes.lookup ty state.ConcreteTypes |> Option.get
+                    let ret = AllConcreteTypes.lookup ret state.ConcreteTypes |> Option.get
+
+                    match ty.Namespace, ty.Name, ty.Generics.IsEmpty, ret.Namespace, ret.Name, ret.Generics.IsEmpty with
+                    | "System.Reflection", "BindingFlags", true, "System.Reflection", "FieldInfo", true ->
+                        failwith "TODO: GetField"
+                    | _ -> failwith "unexpected signature for Type.GetField"
                 | assy, ns, typeName, methName, param, retType ->
                     failwith
                         $"TODO: tried to IL-interpret a method in {assy} {ns}.{typeName} named {methName} with no implementation; {param} -> {retType}"

WoofWare.PawPrint/AbstractMachineDomain.fs

@@ -14,6 +14,3 @@ type ManagedHeapAddress =
     override this.ToString () : string =
         match this with
         | ManagedHeapAddress.ManagedHeapAddress i -> $"<object #%i{i}>"
-
-[<Measure>]
-type typeHandle

WoofWare.PawPrint/BasicCliType.fs

@@ -63,7 +63,7 @@ type NativeIntSource =
     | Verbatim of int64
     | ManagedPointer of ManagedPointerSource
     | FunctionPointer of MethodInfo<ConcreteTypeHandle, ConcreteTypeHandle, ConcreteTypeHandle>
-    | TypeHandlePtr of int64<typeHandle>
+    | TypeHandlePtr of ConcreteTypeHandle
 
     override this.ToString () : string =
         match this with
@@ -71,7 +71,7 @@ type NativeIntSource =
         | NativeIntSource.ManagedPointer ptr -> $"<managed pointer {ptr}>"
         | NativeIntSource.FunctionPointer methodDefinition ->
             $"<pointer to {methodDefinition.Name} in {methodDefinition.DeclaringType.Assembly.Name}>"
-        | NativeIntSource.TypeHandlePtr ptr -> $"<type ID %i{ptr}>"
+        | NativeIntSource.TypeHandlePtr ptr -> $"<type ID %O{ptr}>"
 
 [<RequireQualifiedAccess>]
 module NativeIntSource =
@@ -113,18 +113,6 @@ type CliNumericType =
     | Float32 of float32
     | Float64 of float
 
-type CliValueType =
-    private
-    | Bool of byte
-    /// A UTF-16 code unit, i.e. two bytes. We store the most significant one first.
-    | Char of byte * byte
-    | UInt8 of uint8
-    | UInt16 of uint16
-    | Int8 of int8
-    | Int16 of int16
-    | Float32 of float32
-    | Float64 of float
-
 [<RequireQualifiedAccess>]
 type CliRuntimePointerSource =
     | LocalVariable of sourceThread : ThreadId * methodFrame : int * whichVar : uint16
@@ -151,15 +139,12 @@ type CliType =
     | RuntimePointer of CliRuntimePointer
     /// This is *not* a CLI type as such. I don't actually know its status. A value type is represented simply
     /// as a concatenated list of its fields.
-    | ValueType of (string * CliType) list
+    | ValueType of CliValueType
 
-    /// In fact any non-zero value will do for True, but we'll use 1
-    static member OfBool (b : bool) = CliType.Bool (if b then 1uy else 0uy)
-
-    static member OfChar (c : char) =
-        CliType.Char (byte (int c / 256), byte (int c % 256))
-
-    static member OfManagedObject (ptr : ManagedHeapAddress) = CliType.ObjectRef (Some ptr)
+and CliValueType =
+    {
+        Fields : (string * CliType) list
+    }
 
 type CliTypeResolutionResult =
     | Resolved of CliType
@@ -167,6 +152,38 @@ type CliTypeResolutionResult =
 
 [<RequireQualifiedAccess>]
 module CliType =
+    /// In fact any non-zero value will do for True, but we'll use 1
+    let ofBool (b : bool) : CliType = CliType.Bool (if b then 1uy else 0uy)
+
+    let ofChar (c : char) : CliType =
+        CliType.Char (byte (int c / 256), byte (int c % 256))
+
+    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"
+            | [ _, f ] -> sizeOf f
+            | _ -> failwith $"TODO: %O{vt.Fields} (need to consider struct layout)"
+
     let zeroOfPrimitive (primitiveType : PrimitiveType) : CliType =
         match primitiveType with
         | PrimitiveType.Boolean -> CliType.Bool 0uy
@@ -309,7 +326,7 @@ module CliType =
         (corelib : BaseClassTypes<DumpedAssembly>)
         (handle : ConcreteTypeHandle)
         (concreteType : ConcreteType<ConcreteTypeHandle>)
-        (typeDef : WoofWare.PawPrint.TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>)
+        (typeDef : WoofWare.PawPrint.TypeInfo<GenericParamFromMetadata, TypeDefn>)
         (visited : Set<ConcreteTypeHandle>)
         : CliType * AllConcreteTypes
         =
@@ -345,7 +362,12 @@ module CliType =
                     (field.Name, fieldZero)
                 )
 
-            CliType.ValueType fieldZeros, currentConcreteTypes
+            let vt =
+                {
+                    Fields = fieldZeros
+                }
+
+            CliType.ValueType vt, currentConcreteTypes
         else
             // It's a reference type
             CliType.ObjectRef None, concreteTypes
@@ -369,13 +391,12 @@ module CliType =
             }
 
         // The field type might reference generic parameters of the declaring type
-        let typeGenerics = declaringType.Generics |> ImmutableArray.CreateRange
         let methodGenerics = ImmutableArray.Empty // Fields don't have method generics
 
         let loadAssembly
             (assyName : AssemblyName)
             (ref : AssemblyReferenceHandle)
-            : (ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
+            : ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly
             =
             match assemblies.TryGetValue assyName.FullName with
             | true, currentAssy ->
@@ -392,7 +413,7 @@ module CliType =
                 ctx
                 loadAssembly
                 declaringType.Assembly
-                typeGenerics
+                declaringType.Generics
                 methodGenerics
                 fieldType
 

WoofWare.PawPrint/Corelib.fs

@@ -134,6 +134,21 @@ module Corelib =
             |> Seq.choose (fun (KeyValue (_, v)) -> if v.Name = "UIntPtr" then Some v else None)
             |> Seq.exactlyOne
 
+        let runtimeFieldInfoStubType =
+            corelib.TypeDefs
+            |> Seq.choose (fun (KeyValue (_, v)) -> if v.Name = "RuntimeFieldInfoStub" then Some v else None)
+            |> Seq.exactlyOne
+
+        let runtimeFieldHandleInternalType =
+            corelib.TypeDefs
+            |> Seq.choose (fun (KeyValue (_, v)) ->
+                if v.Name = "RuntimeFieldHandleInternal" then
+                    Some v
+                else
+                    None
+            )
+            |> Seq.exactlyOne
+
         {
             Corelib = corelib
             String = stringType
@@ -157,6 +172,8 @@ module Corelib =
             RuntimeTypeHandle = runtimeTypeHandleType
             RuntimeMethodHandle = runtimeMethodHandleType
             RuntimeFieldHandle = runtimeFieldHandleType
+            RuntimeFieldInfoStub = runtimeFieldInfoStubType
+            RuntimeFieldHandleInternal = runtimeFieldHandleInternalType
             RuntimeType = runtimeTypeType
             Void = voidType
             TypedReference = typedReferenceType

WoofWare.PawPrint/EvalStack.fs

@@ -197,7 +197,7 @@ module EvalStackValue =
             match popped with
             | EvalStackValue.ManagedPointer src ->
                 match src with
-                | ManagedPointerSource.Heap addr -> CliType.OfManagedObject addr
+                | ManagedPointerSource.Heap addr -> CliType.ofManagedObject addr
                 | ManagedPointerSource.Null -> CliType.ObjectRef None
                 | ManagedPointerSource.LocalVariable (sourceThread, methodFrame, var) ->
                     CliRuntimePointerSource.LocalVariable (sourceThread, methodFrame, var)
@@ -238,25 +238,30 @@ module EvalStackValue =
                 let low = i % 256
                 CliType.Char (byte<int> high, byte<int> low)
             | popped -> failwith $"Unexpectedly wanted a char from {popped}"
-        | CliType.ValueType fields ->
+        | CliType.ValueType vt ->
             match popped with
             | EvalStackValue.UserDefinedValueType popped ->
-                if fields.Length <> popped.Length then
+                if vt.Fields.Length <> popped.Length then
                     failwith
-                        $"mismatch: popped value type {popped} (length %i{popped.Length}) into {fields} (length %i{fields.Length})"
+                        $"mismatch: popped value type {popped} (length %i{popped.Length}) into {vt} (length %i{vt.Fields.Length})"
 
-                List.map2
-                    (fun (name1, v1) (name2, v2) ->
-                        if name1 <> name2 then
-                            failwith $"TODO: name mismatch, {name1} vs {name2}"
+                let fields =
+                    List.map2
+                        (fun (name1, v1) (name2, v2) ->
+                            if name1 <> name2 then
+                                failwith $"TODO: name mismatch, {name1} vs {name2}"
 
-                        name1, toCliTypeCoerced v1 v2
-                    )
-                    fields
-                    popped
+                            name1, toCliTypeCoerced v1 v2
+                        )
+                        vt.Fields
+                        popped
+
+                {
+                    Fields = fields
+                }
                 |> CliType.ValueType
             | popped ->
-                match fields with
+                match vt.Fields with
                 | [ _, target ] -> toCliTypeCoerced target popped
                 | _ -> failwith $"TODO: {popped} into value type {target}"
 
@@ -299,7 +304,7 @@ module EvalStackValue =
                 | CliRuntimePointerSource.Heap addr -> EvalStackValue.ObjectRef addr
                 | CliRuntimePointerSource.Null -> EvalStackValue.ManagedPointer ManagedPointerSource.Null
         | CliType.ValueType fields ->
-            fields
+            fields.Fields
             |> List.map (fun (name, f) -> name, ofCliType f)
             |> EvalStackValue.UserDefinedValueType
 
@@ -335,3 +340,5 @@ type EvalStack =
         let v = EvalStackValue.ofCliType v
 
         EvalStack.Push' v stack
+
+    static member PeekNthFromTop (n : int) (stack : EvalStack) : EvalStackValue option = stack.Values |> List.tryItem n

WoofWare.PawPrint/EvalStackValueComparisons.fs

@@ -120,9 +120,14 @@ module EvalStackValueComparisons =
             failwith "TODO"
         | other1, other2 -> failwith $"Cgt.un instruction invalid for comparing {other1} vs {other2}"
 
-    let ceq (var1 : EvalStackValue) (var2 : EvalStackValue) : bool =
+    let rec ceq (var1 : EvalStackValue) (var2 : EvalStackValue) : bool =
         // Table III.4
         match var1, var2 with
+        | EvalStackValue.UserDefinedValueType [ _, u ], v -> ceq u v
+        | u, EvalStackValue.UserDefinedValueType [ _, v ] -> ceq u v
+        | EvalStackValue.UserDefinedValueType [], EvalStackValue.UserDefinedValueType [] -> true
+        | EvalStackValue.UserDefinedValueType _, _
+        | _, EvalStackValue.UserDefinedValueType _ -> failwith $"bad ceq: {var1} vs {var2}"
         | 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}"
@@ -151,4 +156,3 @@ module EvalStackValueComparisons =
         | EvalStackValue.ManagedPointer var1, EvalStackValue.NativeInt var2 ->
             failwith $"TODO (CEQ): managed pointer vs nativeint"
         | EvalStackValue.ManagedPointer _, _ -> failwith $"bad ceq: ManagedPointer vs {var2}"
-        | EvalStackValue.UserDefinedValueType _, _ -> failwith $"bad ceq: {var1} vs {var2}"

WoofWare.PawPrint/Exceptions.fs

@@ -34,7 +34,7 @@ module ExceptionHandling =
 
     /// Check if an exception type matches a catch handler type
     let private isExceptionAssignableTo
-        (exceptionTypeCrate : TypeInfoCrate)
+        (exceptionType : ConcreteTypeHandle)
         (catchTypeToken : MetadataToken)
         (assemblies : ImmutableDictionary<string, DumpedAssembly>)
         : bool
@@ -46,7 +46,7 @@ module ExceptionHandling =
     /// Also returns `isFinally : bool`: whether this is a `finally` block (as opposed to e.g. a `catch`).
     let findExceptionHandler
         (currentPC : int)
-        (exceptionTypeCrate : TypeInfoCrate)
+        (exceptionType : ConcreteTypeHandle)
         (method : WoofWare.PawPrint.MethodInfo<'typeGen, 'methodGeneric, 'methodVar>)
         (assemblies : ImmutableDictionary<string, DumpedAssembly>)
         : (WoofWare.PawPrint.ExceptionRegion * bool) option // handler, isFinally
@@ -62,7 +62,7 @@ module ExceptionHandling =
             | ExceptionRegion.Catch (typeToken, offset) ->
                 if currentPC >= offset.TryOffset && currentPC < offset.TryOffset + offset.TryLength then
                     // Check if exception type matches
-                    if isExceptionAssignableTo exceptionTypeCrate typeToken assemblies then
+                    if isExceptionAssignableTo exceptionType typeToken assemblies then
                         Some (region, false)
                     else
                         None

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

@@ -82,7 +82,7 @@ module System_Threading_Monitor =
                     | ManagedPointerSource.Null -> failwith "logic error"
                     | ManagedPointerSource.LocalVariable (sourceThread, methodFrame, whichVar) ->
                         state
-                        |> IlMachineState.setLocalVariable sourceThread methodFrame whichVar (CliType.OfBool true)
+                        |> IlMachineState.setLocalVariable sourceThread methodFrame whichVar (CliType.ofBool true)
                     | ManagedPointerSource.Argument (sourceThread, methodFrame, whichVar) ->
                         failwith "not really expecting to *edit* an argument..."
                     | ManagedPointerSource.Heap addr -> failwith "todo: managed heap"

WoofWare.PawPrint/FieldHandleRegistry.fs

@@ -0,0 +1,111 @@
+namespace WoofWare.PawPrint
+
+open System.Reflection
+open System.Reflection.Metadata
+
+type FieldHandle =
+    private
+        {
+            AssemblyFullName : string
+            DeclaringType : ConcreteTypeHandle
+            FieldHandle : ComparableFieldDefinitionHandle
+        }
+
+type FieldHandleRegistry =
+    private
+        {
+            FieldHandleToId : Map<FieldHandle, int64>
+            FieldHandleToField : Map<ManagedHeapAddress, FieldHandle>
+            FieldToHandle : Map<FieldHandle, ManagedHeapAddress>
+            NextHandle : int64
+        }
+
+[<RequireQualifiedAccess>]
+module FieldHandleRegistry =
+    let empty () =
+        {
+            FieldHandleToField = Map.empty
+            FieldToHandle = Map.empty
+            FieldHandleToId = Map.empty
+            NextHandle = 1L
+        }
+
+    /// Returns a (struct) System.RuntimeFieldHandle, with its contents (reference type) freshly allocated if necessary.
+    let getOrAllocate
+        (baseClassTypes : BaseClassTypes<'corelib>)
+        (allocState : 'allocState)
+        (allocate : (string * CliType) list -> 'allocState -> ManagedHeapAddress * 'allocState)
+        (declaringAssy : AssemblyName)
+        (declaringType : ConcreteTypeHandle)
+        (handle : FieldDefinitionHandle)
+        (reg : FieldHandleRegistry)
+        : CliType * FieldHandleRegistry * 'allocState
+        =
+
+        let runtimeFieldHandle (runtimeFieldInfoStub : ManagedHeapAddress) =
+            // RuntimeFieldHandle is a struct; it contains one field, an IRuntimeFieldInfo
+            // https://github.com/dotnet/runtime/blob/1d1bf92fcf43aa6981804dc53c5174445069c9e4/src/coreclr/System.Private.CoreLib/src/System/RuntimeHandles.cs#L1048
+            // In practice we expect to use RuntimeFieldInfoStub for that IRuntimeFieldInfo:
+            // https://github.com/dotnet/runtime/blob/1d1bf92fcf43aa6981804dc53c5174445069c9e4/src/coreclr/System.Private.CoreLib/src/System/RuntimeHandles.cs#L1157
+            let runtimeFieldHandleType = baseClassTypes.RuntimeFieldHandle
+            let field = runtimeFieldHandleType.Fields |> List.exactlyOne
+
+            if field.Name <> "m_ptr" then
+                failwith $"unexpected field name %s{field.Name} for BCL type RuntimeFieldHandle"
+
+            {
+                Fields = [ "m_ptr", CliType.ofManagedObject runtimeFieldInfoStub ]
+            }
+            |> CliType.ValueType
+
+        let handle =
+            {
+                AssemblyFullName = declaringAssy.FullName
+                FieldHandle = ComparableFieldDefinitionHandle.Make handle
+                DeclaringType = declaringType
+            }
+
+        match Map.tryFind handle reg.FieldToHandle with
+        | Some v -> runtimeFieldHandle v, reg, allocState
+        | None ->
+
+        let newHandle = reg.NextHandle
+
+        let runtimeFieldHandleInternal =
+            let field = baseClassTypes.RuntimeFieldHandleInternal.Fields |> List.exactlyOne
+
+            if field.Name <> "m_handle" then
+                failwith $"unexpected field name %s{field.Name} for BCL type RuntimeFieldHandleInternal"
+
+            match field.Signature with
+            | TypeDefn.PrimitiveType PrimitiveType.IntPtr -> ()
+            | s -> failwith $"bad sig: {s}"
+
+            {
+                Fields = [ "m_handle", CliType.RuntimePointer (CliRuntimePointer.Unmanaged newHandle) ]
+            }
+            |> CliType.ValueType
+
+        let runtimeFieldInfoStub =
+            [
+                // If we ever implement a GC, something should change here
+                "m_keepalive", CliType.ObjectRef None
+                "m_c", CliType.ObjectRef None
+                "m_d", CliType.ObjectRef None
+                "m_b", CliType.Numeric (CliNumericType.Int32 0)
+                "m_e", CliType.ObjectRef None
+                // RuntimeFieldHandleInternal: https://github.com/dotnet/runtime/blob/1d1bf92fcf43aa6981804dc53c5174445069c9e4/src/coreclr/System.Private.CoreLib/src/System/RuntimeHandles.cs#L1048
+                "m_fieldHandle", runtimeFieldHandleInternal
+            ]
+
+        let alloc, state = allocate runtimeFieldInfoStub allocState
+
+        let reg =
+            {
+                FieldHandleToField = reg.FieldHandleToField |> Map.add alloc handle
+                FieldToHandle = reg.FieldToHandle |> Map.add handle alloc
+                FieldHandleToId = reg.FieldHandleToId |> Map.add handle newHandle
+                NextHandle = reg.NextHandle + 1L
+            }
+
+        runtimeFieldHandle alloc, reg, state

WoofWare.PawPrint/IlMachineStateExecution.fs

@@ -0,0 +1,849 @@
+namespace WoofWare.PawPrint
+
+open System
+open System.Collections.Immutable
+open System.Reflection
+open System.Reflection.Metadata
+open System.Runtime.CompilerServices
+open Microsoft.Extensions.Logging
+
+[<RequireQualifiedAccess>]
+module IlMachineStateExecution =
+    let getTypeOfObj
+        (baseClassTypes : BaseClassTypes<DumpedAssembly>)
+        (state : IlMachineState)
+        (esv : EvalStackValue)
+        : IlMachineState * ConcreteTypeHandle
+        =
+        match esv with
+        | EvalStackValue.Int32 _ ->
+            TypeDefn.FromDefinition (
+                ComparableTypeDefinitionHandle.Make baseClassTypes.Int32.TypeDefHandle,
+                baseClassTypes.Corelib.Name.FullName,
+                SignatureTypeKind.ValueType
+            )
+            |> IlMachineState.concretizeType
+                baseClassTypes
+                state
+                baseClassTypes.Corelib.Name
+                ImmutableArray.Empty
+                ImmutableArray.Empty
+        | EvalStackValue.Int64 _ ->
+            TypeDefn.FromDefinition (
+                ComparableTypeDefinitionHandle.Make baseClassTypes.Int64.TypeDefHandle,
+                baseClassTypes.Corelib.Name.FullName,
+                SignatureTypeKind.ValueType
+            )
+            |> IlMachineState.concretizeType
+                baseClassTypes
+                state
+                baseClassTypes.Corelib.Name
+                ImmutableArray.Empty
+                ImmutableArray.Empty
+        | EvalStackValue.NativeInt nativeIntSource -> failwith "todo"
+        | EvalStackValue.Float _ ->
+            TypeDefn.FromDefinition (
+                ComparableTypeDefinitionHandle.Make baseClassTypes.Double.TypeDefHandle,
+                baseClassTypes.Corelib.Name.FullName,
+                SignatureTypeKind.ValueType
+            )
+            |> IlMachineState.concretizeType
+                baseClassTypes
+                state
+                baseClassTypes.Corelib.Name
+                ImmutableArray.Empty
+                ImmutableArray.Empty
+        | EvalStackValue.ManagedPointer src ->
+            match src with
+            | ManagedPointerSource.LocalVariable (sourceThread, methodFrame, whichVar) -> failwith "todo"
+            | ManagedPointerSource.Argument (sourceThread, methodFrame, whichVar) -> failwith "todo"
+            | ManagedPointerSource.Heap addr ->
+                let o = ManagedHeap.Get addr state.ManagedHeap
+                state, o.ConcreteType
+            | ManagedPointerSource.ArrayIndex (arr, index) -> failwith "todo"
+            | ManagedPointerSource.Null -> failwith "todo"
+        | EvalStackValue.ObjectRef addr ->
+            let o = ManagedHeap.Get addr state.ManagedHeap
+            state, o.ConcreteType
+        | EvalStackValue.UserDefinedValueType tuples -> failwith "todo"
+
+    let isAssignableFrom
+        (objToCast : ConcreteTypeHandle)
+        (possibleTargetType : ConcreteTypeHandle)
+        (state : IlMachineState)
+        : bool
+        =
+        if objToCast = possibleTargetType then
+            true
+        else
+
+        let objToCast' = AllConcreteTypes.lookup objToCast state.ConcreteTypes |> Option.get
+
+        let possibleTargetType' =
+            AllConcreteTypes.lookup possibleTargetType state.ConcreteTypes |> Option.get
+
+        // TODO: null can be assigned to any reference type; might not be relevant here?
+
+        match possibleTargetType with
+        | ConcreteObj state.ConcreteTypes -> true
+        | ConcreteValueType state.ConcreteTypes when failwith "check if objToCast inherits ValueType" -> true
+        | _ ->
+            // Claude describes the algorithm here:
+            // https://claude.ai/chat/f15e23f6-a27b-4655-9e69-e4d445dd1249
+            failwith
+                $"TODO: check inheritance chain and interfaces: is {objToCast'} assignable from {possibleTargetType'}?"
+
+    let callMethod
+        (loggerFactory : ILoggerFactory)
+        (baseClassTypes : BaseClassTypes<DumpedAssembly>)
+        (wasInitialising : ConcreteTypeHandle option)
+        (wasConstructing : ManagedHeapAddress option)
+        (performInterfaceResolution : bool)
+        (wasClassConstructor : bool)
+        (advanceProgramCounterOfCaller : bool)
+        (methodGenerics : ImmutableArray<ConcreteTypeHandle>)
+        (methodToCall : WoofWare.PawPrint.MethodInfo<ConcreteTypeHandle, ConcreteTypeHandle, ConcreteTypeHandle>)
+        (thread : ThreadId)
+        (threadState : ThreadState)
+        (state : IlMachineState)
+        : IlMachineState
+        =
+        let logger = loggerFactory.CreateLogger "CallMethod"
+        let activeAssy = state.ActiveAssembly thread
+
+        // Check for intrinsics first
+        let isIntrinsic =
+            MethodInfo.isJITIntrinsic
+                (fun handle ->
+                    match activeAssy.Members.[handle].Parent with
+                    | MetadataToken.TypeReference r -> activeAssy.TypeRefs.[r]
+                    | x -> failwith $"{x}"
+                )
+                activeAssy.Methods
+                methodToCall
+
+        match
+            if isIntrinsic then
+                Intrinsics.call 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)
+            ||> List.fold (fun (state, zeros) tyHandle ->
+                let zero, state = IlMachineState.cliTypeZeroOfHandle state baseClassTypes tyHandle
+                state, zero :: zeros
+            )
+
+        let argZeroObjects = List.rev argZeroObjects
+
+        let activeMethodState = threadState.MethodStates.[threadState.ActiveMethodState]
+
+        let state, methodToCall =
+            match methodToCall.Instructions, performInterfaceResolution, methodToCall.IsStatic with
+            | None, true, false ->
+                logger.LogDebug (
+                    "Identifying target of virtual call for {TypeName}.{MethodName}",
+                    methodToCall.DeclaringType.Name,
+                    methodToCall.Name
+                )
+                // This might be an interface implementation, or implemented by native code.
+                // If native code, we'll deal with that when we actually start implementing.
+
+                // Since we're not static, there's a `this` on the eval stack.
+                // It comes *below* all the arguments.
+                let callingObj =
+                    match
+                        activeMethodState.EvaluationStack
+                        |> EvalStack.PeekNthFromTop methodToCall.Parameters.Length
+                    with
+                    | None -> failwith "unexpectedly no `this` on the eval stack of instance method"
+                    | Some this -> this
+
+                let state, callingObjTyHandle = getTypeOfObj baseClassTypes state callingObj
+
+                let callingObjTy =
+                    let ty =
+                        AllConcreteTypes.lookup callingObjTyHandle state.ConcreteTypes |> Option.get
+
+                    state.LoadedAssembly(ty.Assembly).Value.TypeDefs.[ty.Definition.Get]
+
+                let declaringAssy = state.LoadedAssembly(methodToCall.DeclaringType.Assembly).Value
+
+                let methodDeclaringType =
+                    declaringAssy.TypeDefs.[methodToCall.DeclaringType.Definition.Get]
+
+                let interfaceExplicitNamedMethod =
+                    if methodDeclaringType.IsInterface then
+                        Some
+                            $"{TypeInfo.fullName (fun h -> declaringAssy.TypeDefs.[h]) methodDeclaringType}.{methodToCall.Name}"
+                    else
+                        None
+
+                // Does type `callingObjTy` implement this method? If so, this is probably a JIT intrinsic or
+                // is supplied by the runtime.
+                let selfImplementation, state =
+                    (state, callingObjTy.Methods)
+                    ||> List.mapFold (fun state meth ->
+                        if
+                            meth.Signature.GenericParameterCount
+                            <> methodToCall.Signature.GenericParameterCount
+                            || meth.Signature.RequiredParameterCount
+                               <> methodToCall.Signature.RequiredParameterCount
+                        then
+                            None, state
+                        else if
+
+                            meth.Name <> methodToCall.Name && Some meth.Name <> interfaceExplicitNamedMethod
+                        then
+                            None, state
+                        else
+
+                        // TODO: check if methodToCall's declaringtype is an interface; if so, check the possible prefixed name first
+
+                        let state, retType =
+                            meth.Signature.ReturnType
+                            |> IlMachineState.concretizeType
+                                baseClassTypes
+                                state
+                                meth.DeclaringType.Assembly
+                                methodToCall.DeclaringType.Generics
+                                methodToCall.Generics
+
+                        let paramTypes, state =
+                            (state, meth.Signature.ParameterTypes)
+                            ||> Seq.mapFold (fun state ty ->
+                                ty
+                                |> IlMachineState.concretizeType
+                                    baseClassTypes
+                                    state
+                                    meth.DeclaringType.Assembly
+                                    methodToCall.DeclaringType.Generics
+                                    methodToCall.Generics
+                                |> fun (a, b) -> b, a
+                            )
+
+                        let paramTypes = List.ofSeq paramTypes
+
+                        if
+                            isAssignableFrom retType methodToCall.Signature.ReturnType state
+                            && paramTypes = methodToCall.Signature.ParameterTypes
+                        then
+                            Some (meth, Some meth.Name = interfaceExplicitNamedMethod), state
+                        else
+                            None, state
+                    )
+
+                let selfImplementation =
+                    selfImplementation
+                    |> List.choose id
+                    |> List.sortBy (fun (_, isInterface) -> if isInterface then -1 else 0)
+
+                match selfImplementation with
+                | (impl, true) :: l when (l |> List.forall (fun (_, b) -> not b)) ->
+                    logger.LogDebug "Found concrete implementation from an interface"
+
+                    let typeGenerics =
+                        AllConcreteTypes.lookup callingObjTyHandle state.ConcreteTypes
+                        |> Option.get
+                        |> _.Generics
+
+                    let state, meth, _ =
+                        IlMachineState.concretizeMethodWithAllGenerics
+                            loggerFactory
+                            baseClassTypes
+                            typeGenerics
+                            impl
+                            methodGenerics
+                            state
+
+                    state, meth
+                | [ impl, false ] ->
+                    logger.LogDebug "Found concrete implementation"
+                    // Yes, callingObjTy implements the method directly. No need to look up interfaces.
+                    let typeGenerics =
+                        AllConcreteTypes.lookup callingObjTyHandle state.ConcreteTypes
+                        |> Option.get
+                        |> _.Generics
+
+                    let state, meth, _ =
+                        IlMachineState.concretizeMethodWithAllGenerics
+                            loggerFactory
+                            baseClassTypes
+                            typeGenerics
+                            impl
+                            methodGenerics
+                            state
+
+                    state, meth
+                | _ :: _ ->
+                    selfImplementation
+                    |> List.map (fun (m, _) -> m.Name)
+                    |> String.concat ", "
+                    |> failwithf "multiple options: %s"
+                | [] ->
+
+                logger.LogDebug "No concrete implementation found; scanning interfaces"
+
+                // If not, what interfaces does it implement, and do any of those implement the method?
+                let possibleInterfaceMethods, state =
+                    (state, callingObjTy.ImplementedInterfaces)
+                    ||> Seq.mapFold (fun state impl ->
+                        let assy = state.LoadedAssembly impl.RelativeToAssembly |> Option.get
+
+                        let state, defn =
+                            match impl.InterfaceHandle with
+                            | MetadataToken.TypeDefinition defn ->
+                                let state, defn = IlMachineState.lookupTypeDefn baseClassTypes state assy defn
+
+                                let state, _, defn =
+                                    // TODO: generics
+                                    IlMachineState.resolveTypeFromDefn
+                                        loggerFactory
+                                        baseClassTypes
+                                        defn
+                                        ImmutableArray.Empty
+                                        ImmutableArray.Empty
+                                        assy
+                                        state
+
+                                state, defn
+                            | MetadataToken.TypeReference ty ->
+                                let state, defn, assy =
+                                    IlMachineState.lookupTypeRef loggerFactory baseClassTypes state assy Seq.empty ty
+
+                                state, failwith "TODO"
+                            | MetadataToken.TypeSpecification spec ->
+                                // TODO: generics
+                                let state, assy, defn =
+                                    IlMachineState.resolveTypeFromSpec
+                                        loggerFactory
+                                        baseClassTypes
+                                        spec
+                                        assy
+                                        ImmutableArray.Empty
+                                        ImmutableArray.Empty
+                                        state
+
+                                state, defn
+                            | handle -> failwith $"unexpected: {handle}"
+
+                        logger.LogDebug (
+                            "Interface {InterfaceName} (generics: {InterfaceGenerics})",
+                            defn.Name,
+                            defn.Generics
+                        )
+
+                        let s, state =
+                            defn.Methods
+                            |> Seq.filter (fun mi -> mi.Name = methodToCall.Name
+                            // TODO: also the rest of the signature
+                            )
+                            |> Seq.mapFold
+                                (fun state meth ->
+                                    // TODO: generics
+                                    let state, mi, _ =
+                                        IlMachineState.concretizeMethodForExecution
+                                            loggerFactory
+                                            baseClassTypes
+                                            thread
+                                            meth
+                                            None
+                                            (if defn.Generics.IsEmpty then None else Some defn.Generics)
+                                            state
+
+                                    mi, state
+                                )
+                                state
+
+                        s, state
+                    )
+
+                let possibleInterfaceMethods = possibleInterfaceMethods |> Seq.concat |> Seq.toList
+
+                match possibleInterfaceMethods with
+                | [] ->
+                    logger.LogDebug "No interface implementation found either"
+                    state, methodToCall
+                | [ meth ] ->
+                    logger.LogDebug (
+                        "Exactly one interface implementation found {DeclaringTypeNamespace}.{DeclaringTypeName}.{MethodName} ({MethodGenerics})",
+                        meth.DeclaringType.Namespace,
+                        meth.DeclaringType.Name,
+                        meth.Name,
+                        meth.Generics
+                    )
+
+                    state, meth
+                | _ -> failwith "TODO: handle overloads"
+            | _, _, true
+            | _, false, _
+            | Some _, _, _ -> state, methodToCall
+
+        // Helper to pop and coerce a single argument
+        let popAndCoerceArg zeroType methodState =
+            let value, newState = MethodState.popFromStack methodState
+            EvalStackValue.toCliTypeCoerced zeroType value, newState
+
+        // Collect arguments based on calling convention
+        let args, afterPop =
+            if methodToCall.IsStatic then
+                // Static method: pop args in reverse order
+                let args = ImmutableArray.CreateBuilder methodToCall.Parameters.Length
+                let mutable currentState = activeMethodState
+
+                for i = methodToCall.Parameters.Length - 1 downto 0 do
+                    let arg, newState = popAndCoerceArg argZeroObjects.[i] currentState
+                    args.Add arg
+                    currentState <- newState
+
+                args.Reverse ()
+                args.ToImmutable (), currentState
+            else
+                // Instance method: handle `this` pointer
+                let argCount = methodToCall.Parameters.Length
+                let args = ImmutableArray.CreateBuilder (argCount + 1)
+                let mutable currentState = activeMethodState
+
+                match wasConstructing with
+                | Some _ ->
+                    // Constructor: `this` is on top of stack, by our own odd little calling convention
+                    // where Newobj puts the object pointer on top
+                    let thisArg, newState =
+                        popAndCoerceArg
+                            (CliType.RuntimePointer (CliRuntimePointer.Managed CliRuntimePointerSource.Null))
+                            currentState
+
+                    currentState <- newState
+
+                    // Pop remaining args in reverse
+                    for i = argCount - 1 downto 0 do
+                        let arg, newState = popAndCoerceArg argZeroObjects.[i] currentState
+                        args.Add arg
+                        currentState <- newState
+
+                    args.Add thisArg
+                    args.Reverse ()
+                    args.ToImmutable (), currentState
+                | None ->
+                    // Regular instance method: args then `this`
+                    for i = argCount - 1 downto 0 do
+                        let arg, newState = popAndCoerceArg argZeroObjects.[i] currentState
+                        args.Add arg
+                        currentState <- newState
+
+                    let thisArg, newState =
+                        popAndCoerceArg
+                            (CliType.RuntimePointer (CliRuntimePointer.Managed CliRuntimePointerSource.Null))
+                            currentState
+
+                    args.Add thisArg
+                    currentState <- newState
+
+                    args.Reverse ()
+                    args.ToImmutable (), currentState
+
+        // Helper to create new frame with assembly loading
+        let rec createNewFrame state =
+            let returnInfo =
+                Some
+                    {
+                        JumpTo = threadState.ActiveMethodState
+                        WasInitialisingType = wasInitialising
+                        WasConstructingObj = wasConstructing
+                    }
+
+            match
+                MethodState.Empty
+                    state.ConcreteTypes
+                    baseClassTypes
+                    state._LoadedAssemblies
+                    (state.ActiveAssembly thread)
+                    methodToCall
+                    methodGenerics
+                    args
+                    returnInfo
+            with
+            | Ok frame -> state, frame
+            | Error toLoad ->
+                let state' =
+                    (state, toLoad)
+                    ||> List.fold (fun s (asmRef : WoofWare.PawPrint.AssemblyReference) ->
+                        let s, _, _ =
+                            IlMachineState.loadAssembly
+                                loggerFactory
+                                (state.LoadedAssembly methodToCall.DeclaringType.Assembly |> Option.get)
+                                (fst asmRef.Handle)
+                                s
+
+                        s
+                    )
+
+                createNewFrame state'
+
+        let state, newFrame = createNewFrame state
+
+        let oldFrame =
+            if wasClassConstructor || not advanceProgramCounterOfCaller then
+                afterPop
+            else
+                afterPop |> MethodState.advanceProgramCounter
+
+        let newThreadState =
+            { threadState with
+                MethodStates = threadState.MethodStates.Add(newFrame).SetItem (threadState.ActiveMethodState, oldFrame)
+                ActiveMethodState = threadState.MethodStates.Length
+            }
+
+        { state with
+            ThreadState = state.ThreadState |> Map.add thread newThreadState
+        }
+
+    let rec loadClass
+        (loggerFactory : ILoggerFactory)
+        (baseClassTypes : BaseClassTypes<DumpedAssembly>)
+        (ty : ConcreteTypeHandle)
+        (currentThread : ThreadId)
+        (state : IlMachineState)
+        : StateLoadResult
+        =
+        let logger = loggerFactory.CreateLogger "LoadClass"
+
+        match TypeInitTable.tryGet ty state.TypeInitTable with
+        | Some TypeInitState.Initialized ->
+            // Type already initialized; nothing to do
+            StateLoadResult.NothingToDo state
+        | Some (TypeInitState.InProgress tid) when tid = currentThread ->
+            // We're already initializing this type on this thread; just proceed with the initialisation, no extra
+            // class loading required.
+            StateLoadResult.NothingToDo state
+        | Some (TypeInitState.InProgress _) ->
+            // This is usually signalled by WhatWeDid.Blocked
+            failwith
+                "TODO: cross-thread class init synchronization unimplemented - this thread has to wait for the other thread to finish initialisation"
+        | None ->
+            // We have work to do!
+
+            // Look up the concrete type from the handle
+            let concreteType =
+                match AllConcreteTypes.lookup ty state.ConcreteTypes with
+                | Some ct -> ct
+                | None -> failwith $"ConcreteTypeHandle {ty} not found in ConcreteTypes mapping"
+
+            let state, origAssyName =
+                state.WithThreadSwitchedToAssembly concreteType.Assembly currentThread
+
+            let sourceAssembly = state.LoadedAssembly concreteType.Assembly |> Option.get
+
+            let typeDef =
+                match sourceAssembly.TypeDefs.TryGetValue concreteType.Definition.Get with
+                | false, _ ->
+                    failwith
+                        $"Failed to find type definition {concreteType.Definition.Get} in {concreteType.Assembly.FullName}"
+                | true, v -> v
+
+            logger.LogDebug ("Resolving type {TypeDefNamespace}.{TypeDefName}", typeDef.Namespace, typeDef.Name)
+
+            // First mark as in-progress to detect cycles
+            let state = state.WithTypeBeginInit currentThread ty
+
+            // Check if the type has a base type that needs initialization
+            let firstDoBaseClass =
+                match typeDef.BaseType with
+                | Some baseTypeInfo ->
+                    // Determine if base type is in the same or different assembly
+                    match baseTypeInfo with
+                    | BaseTypeInfo.ForeignAssemblyType _ -> failwith "TODO"
+                    //logger.LogDebug (
+                    //    "Resolved base type of {TypeDefNamespace}.{TypeDefName} to foreign assembly {ForeignAssemblyName}",
+                    //    typeDef.Namespace,
+                    //    typeDef.Name,
+                    //    baseAssemblyName.Name
+                    //)
+
+                    //match loadClass loggerFactory baseTypeHandle baseAssemblyName currentThread state with
+                    //| FirstLoadThis state -> Error state
+                    //| NothingToDo state -> Ok state
+                    | BaseTypeInfo.TypeDef typeDefinitionHandle ->
+                        logger.LogDebug (
+                            "Resolved base type of {TypeDefNamespace}.{TypeDefName} to this assembly, typedef",
+                            typeDef.Namespace,
+                            typeDef.Name
+                        )
+
+                        // TypeDef won't have any generics; it would be a TypeSpec if it did
+                        // Create a TypeDefn from the TypeDef handle
+                        let baseTypeDefn =
+                            let baseTypeDef = sourceAssembly.TypeDefs.[typeDefinitionHandle]
+
+                            let baseType =
+                                baseTypeDef.BaseType
+                                |> DumpedAssembly.resolveBaseType
+                                    baseClassTypes
+                                    state._LoadedAssemblies
+                                    sourceAssembly.Name
+
+                            let signatureTypeKind =
+                                match baseType with
+                                | ResolvedBaseType.Enum
+                                | ResolvedBaseType.ValueType -> SignatureTypeKind.ValueType
+                                | ResolvedBaseType.Object
+                                | ResolvedBaseType.Delegate -> SignatureTypeKind.Class
+
+                            TypeDefn.FromDefinition (
+                                ComparableTypeDefinitionHandle.Make typeDefinitionHandle,
+                                sourceAssembly.Name.FullName,
+                                signatureTypeKind
+                            )
+
+                        // Concretize the base type
+                        let state, baseTypeHandle =
+                            IlMachineState.concretizeType
+                                baseClassTypes
+                                state
+                                sourceAssembly.Name
+                                concreteType.Generics
+                                // TODO: surely we have generics in scope here?
+                                ImmutableArray.Empty
+                                baseTypeDefn
+
+                        // Recursively load the base class
+                        match loadClass loggerFactory baseClassTypes baseTypeHandle currentThread state with
+                        | FirstLoadThis state -> Error state
+                        | NothingToDo state -> Ok state
+                    | BaseTypeInfo.TypeRef typeReferenceHandle ->
+                        let state, assy, targetType =
+                            // TypeRef won't have any generics; it would be a TypeSpec if it did
+                            IlMachineState.resolveType
+                                loggerFactory
+                                typeReferenceHandle
+                                ImmutableArray.Empty
+                                (state.ActiveAssembly currentThread)
+                                state
+
+                        logger.LogDebug (
+                            "Resolved base type of {TypeDefNamespace}.{TypeDefName} to a typeref in assembly {ResolvedAssemblyName}, {BaseTypeNamespace}.{BaseTypeName}",
+                            typeDef.Namespace,
+                            typeDef.Name,
+                            assy.Name.Name,
+                            targetType.Namespace,
+                            targetType.Name
+                        )
+
+                        // Create a TypeDefn from the resolved TypeRef
+                        let baseTypeDefn =
+                            let baseType =
+                                targetType.BaseType
+                                |> DumpedAssembly.resolveBaseType baseClassTypes state._LoadedAssemblies assy.Name
+
+                            let signatureTypeKind =
+                                match baseType with
+                                | ResolvedBaseType.Enum
+                                | ResolvedBaseType.ValueType -> SignatureTypeKind.ValueType
+                                | ResolvedBaseType.Object
+                                | ResolvedBaseType.Delegate -> SignatureTypeKind.Class
+
+                            TypeDefn.FromDefinition (
+                                ComparableTypeDefinitionHandle.Make targetType.TypeDefHandle,
+                                assy.Name.FullName,
+                                signatureTypeKind
+                            )
+
+                        // Concretize the base type
+                        let state, baseTypeHandle =
+                            IlMachineState.concretizeType
+                                baseClassTypes
+                                state
+                                sourceAssembly.Name
+                                concreteType.Generics
+                                // TODO: surely we have generics in scope here?
+                                ImmutableArray.Empty
+                                baseTypeDefn
+
+                        // Recursively load the base class
+                        match loadClass loggerFactory baseClassTypes baseTypeHandle currentThread state with
+                        | FirstLoadThis state -> Error state
+                        | NothingToDo state -> Ok state
+                    | BaseTypeInfo.TypeSpec typeSpecificationHandle ->
+                        failwith "TODO: TypeSpec base type loading unimplemented"
+                | None -> Ok state // No base type (or it's System.Object)
+
+            match firstDoBaseClass with
+            | Error state -> FirstLoadThis state
+            | Ok state ->
+
+            // TODO: also need to initialise all interfaces implemented by the type
+
+            // Find the class constructor (.cctor) if it exists
+            let cctor =
+                typeDef.Methods
+                |> List.tryFind (fun method -> method.Name = ".cctor" && method.IsStatic && method.Parameters.IsEmpty)
+
+            match cctor with
+            | Some cctorMethod ->
+                // Call the class constructor! Note that we *don't* use `callMethodInActiveAssembly`, because that
+                // performs class loading, but we're already in the middle of loading this class.
+                // TODO: factor out the common bit.
+                let currentThreadState = state.ThreadState.[currentThread]
+
+                // Convert the method's type generics from TypeDefn to ConcreteTypeHandle
+                let cctorMethodWithTypeGenerics =
+                    cctorMethod
+                    |> MethodInfo.mapTypeGenerics (fun (par, _) -> concreteType.Generics.[par.SequenceNumber])
+
+                // Convert method generics (should be empty for cctor)
+                let cctorMethodWithMethodGenerics =
+                    cctorMethodWithTypeGenerics
+                    |> MethodInfo.mapMethodGenerics (fun _ -> failwith "cctor cannot be generic")
+
+                // Convert method signature from TypeDefn to ConcreteTypeHandle using concretization
+                let state, convertedSignature =
+                    cctorMethodWithMethodGenerics.Signature
+                    |> TypeMethodSignature.map
+                        state
+                        (fun state typeDefn ->
+                            IlMachineState.concretizeType
+                                baseClassTypes
+                                state
+                                concreteType.Assembly
+                                concreteType.Generics
+                                // no method generics for cctor
+                                ImmutableArray.Empty
+                                typeDefn
+                        )
+
+                // Convert method instructions (local variables)
+                let state, convertedInstructions =
+                    match cctorMethodWithMethodGenerics.Instructions with
+                    | None -> state, None
+                    | Some methodInstr ->
+                        let state, convertedLocalVars =
+                            match methodInstr.LocalVars with
+                            | None -> state, None
+                            | Some localVars ->
+                                // Concretize each local variable type
+                                let state, convertedVars =
+                                    ((state, []), localVars)
+                                    ||> Seq.fold (fun (state, acc) typeDefn ->
+                                        let state, handle =
+                                            IlMachineState.concretizeType
+                                                baseClassTypes
+                                                state
+                                                concreteType.Assembly
+                                                concreteType.Generics
+                                                ImmutableArray.Empty // no method generics for cctor
+                                                typeDefn
+
+                                        state, handle :: acc
+                                    )
+                                    |> Tuple.rmap ImmutableArray.CreateRange
+
+                                state, Some convertedVars
+
+                        state, Some (MethodInstructions.setLocalVars convertedLocalVars methodInstr)
+
+                let fullyConvertedMethod =
+                    MethodInfo.setMethodVars convertedInstructions convertedSignature cctorMethodWithMethodGenerics
+
+                callMethod
+                    loggerFactory
+                    baseClassTypes
+                    (Some ty)
+                    None
+                    true
+                    true
+                    false
+                    // constructor is surely not generic
+                    ImmutableArray.Empty
+                    fullyConvertedMethod
+                    currentThread
+                    currentThreadState
+                    state
+                |> FirstLoadThis
+            | None ->
+                // No constructor, just continue.
+                // Mark the type as initialized.
+                let state = state.WithTypeEndInit currentThread ty
+
+                // Restore original assembly context if needed
+                state.WithThreadSwitchedToAssembly origAssyName currentThread
+                |> fst
+                |> NothingToDo
+
+    let ensureTypeInitialised
+        (loggerFactory : ILoggerFactory)
+        (baseClassTypes : BaseClassTypes<DumpedAssembly>)
+        (thread : ThreadId)
+        (ty : ConcreteTypeHandle)
+        (state : IlMachineState)
+        : IlMachineState * WhatWeDid
+        =
+        match TypeInitTable.tryGet ty state.TypeInitTable with
+        | None ->
+            match loadClass loggerFactory baseClassTypes ty thread state with
+            | NothingToDo state -> state, WhatWeDid.Executed
+            | FirstLoadThis state -> state, WhatWeDid.SuspendedForClassInit
+        | Some TypeInitState.Initialized -> state, WhatWeDid.Executed
+        | Some (InProgress threadId) ->
+            if threadId = thread then
+                // II.10.5.3.2: avoid the deadlock by simply proceeding.
+                state, WhatWeDid.Executed
+            else
+                state, WhatWeDid.BlockedOnClassInit threadId
+
+    /// It may be useful to *not* advance the program counter of the caller, e.g. if you're using `callMethodInActiveAssembly`
+    /// as a convenient way to move to a different method body rather than to genuinely perform a call.
+    /// (Delegates do this, for example: we get a call to invoke the delegate, and then we implement the delegate as
+    /// another call to its function pointer.)
+    let callMethodInActiveAssembly
+        (loggerFactory : ILoggerFactory)
+        (baseClassTypes : BaseClassTypes<DumpedAssembly>)
+        (thread : ThreadId)
+        (performInterfaceResolution : bool)
+        (advanceProgramCounterOfCaller : bool)
+        (methodGenerics : TypeDefn ImmutableArray option)
+        (methodToCall : WoofWare.PawPrint.MethodInfo<TypeDefn, GenericParamFromMetadata, TypeDefn>)
+        (weAreConstructingObj : ManagedHeapAddress option)
+        (typeArgsFromMetadata : TypeDefn ImmutableArray option)
+        (state : IlMachineState)
+        : IlMachineState * WhatWeDid
+        =
+        let threadState = state.ThreadState.[thread]
+
+        let state, concretizedMethod, declaringTypeHandle =
+            IlMachineState.concretizeMethodForExecution
+                loggerFactory
+                baseClassTypes
+                thread
+                methodToCall
+                methodGenerics
+                typeArgsFromMetadata
+                state
+
+        let state, typeInit =
+            ensureTypeInitialised loggerFactory baseClassTypes thread declaringTypeHandle state
+
+        match typeInit with
+        | WhatWeDid.Executed ->
+            callMethod
+                loggerFactory
+                baseClassTypes
+                None
+                weAreConstructingObj
+                performInterfaceResolution
+                false
+                advanceProgramCounterOfCaller
+                concretizedMethod.Generics
+                concretizedMethod
+                thread
+                threadState
+                state,
+            WhatWeDid.Executed
+        | _ -> state, typeInit

WoofWare.PawPrint/ImmutableArray.fs

@@ -0,0 +1,14 @@
+namespace WoofWare.PawPrint
+
+open System.Collections.Immutable
+
+[<RequireQualifiedAccess>]
+module internal ImmutableArray =
+
+    let map (f : 'a -> 'b) (arr : ImmutableArray<'a>) : ImmutableArray<'b> =
+        let b = ImmutableArray.CreateBuilder ()
+
+        for i in arr do
+            b.Add (f i)
+
+        b.ToImmutable ()

WoofWare.PawPrint/Intrinsics.fs

@@ -0,0 +1,307 @@
+namespace WoofWare.PawPrint
+
+open System
+
+[<RequireQualifiedAccess>]
+module Intrinsics =
+    let private safeIntrinsics =
+        [
+            // The IL implementation is fine: https://github.com/dotnet/runtime/blob/ec11903827fc28847d775ba17e0cd1ff56cfbc2e/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/Unsafe.cs#L677
+            "System.Private.CoreLib", "Unsafe", "AsRef"
+            // https://github.com/dotnet/runtime/blob/ec11903827fc28847d775ba17e0cd1ff56cfbc2e/src/libraries/System.Private.CoreLib/src/System/String.cs#L739-L750
+            "System.Private.CoreLib", "String", "get_Length"
+            // https://github.com/dotnet/runtime/blob/ec11903827fc28847d775ba17e0cd1ff56cfbc2e/src/libraries/System.Private.CoreLib/src/System/ArgumentNullException.cs#L54
+            "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"
+        ]
+        |> Set.ofList
+
+    let call
+        (baseClassTypes : BaseClassTypes<_>)
+        (methodToCall : WoofWare.PawPrint.MethodInfo<ConcreteTypeHandle, ConcreteTypeHandle, ConcreteTypeHandle>)
+        (currentThread : ThreadId)
+        (state : IlMachineState)
+        : IlMachineState option
+        =
+        let callerAssy =
+            state.ThreadState.[currentThread].MethodState.ExecutingMethod.DeclaringType.Assembly
+
+        if
+            methodToCall.DeclaringType.Assembly.Name = "System.Private.CoreLib"
+            && methodToCall.DeclaringType.Name = "Volatile"
+        then
+            // These are all safely implemented in IL, just inefficient.
+            // https://github.com/dotnet/runtime/blob/ec11903827fc28847d775ba17e0cd1ff56cfbc2e/src/libraries/System.Private.CoreLib/src/System/Threading/Volatile.cs#L13
+            None
+        elif
+            Set.contains
+                (methodToCall.DeclaringType.Assembly.Name, methodToCall.DeclaringType.Name, methodToCall.Name)
+                safeIntrinsics
+        then
+            None
+        else
+
+        match methodToCall.DeclaringType.Assembly.Name, methodToCall.DeclaringType.Name, methodToCall.Name with
+        | "System.Private.CoreLib", "Type", "get_TypeHandle" ->
+            // TODO: check return type is RuntimeTypeHandle
+            match methodToCall.Signature.ParameterTypes with
+            | _ :: _ -> failwith "bad signature Type.get_TypeHandle"
+            | _ -> ()
+
+            // https://github.com/dotnet/runtime/blob/ec11903827fc28847d775ba17e0cd1ff56cfbc2e/src/libraries/System.Private.CoreLib/src/System/Type.cs#L470
+            // no args, returns RuntimeTypeHandle, a struct with a single field (a RuntimeType class)
+
+            // The thing on top of the stack will be a RuntimeType.
+            let arg, state = IlMachineState.popEvalStack currentThread state
+
+            let arg =
+                let rec go (arg : EvalStackValue) =
+                    match arg with
+                    | EvalStackValue.UserDefinedValueType [ _, s ] -> go s
+                    | EvalStackValue.ManagedPointer ManagedPointerSource.Null -> failwith "TODO: throw NRE"
+                    | EvalStackValue.ManagedPointer (ManagedPointerSource.Heap addr) -> Some addr
+                    | s -> failwith $"TODO: called with unrecognised arg %O{s}"
+
+                go arg
+
+            let state =
+                let vt =
+                    {
+                        Fields = [ "m_type", CliType.ObjectRef arg ]
+                    }
+
+                IlMachineState.pushToEvalStack (CliType.ValueType vt) currentThread state
+                |> IlMachineState.advanceProgramCounter currentThread
+
+            Some state
+        | "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"
+                | x -> failwith $"TODO: Unsafe.AsPointer(%O{x})"
+
+            IlMachineState.pushToEvalStack (CliType.RuntimePointer toPush) currentThread state
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Some
+        | "System.Private.CoreLib", "BitConverter", "SingleToInt32Bits" ->
+            match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
+            | [ ConcreteSingle state.ConcreteTypes ], ConcreteInt32 state.ConcreteTypes -> ()
+            | _ -> failwith "bad signature BitConverter.SingleToInt32Bits"
+
+            let arg, state = IlMachineState.popEvalStack currentThread state
+
+            let result =
+                match arg with
+                | EvalStackValue.Float f -> BitConverter.SingleToInt32Bits (float32<float> f) |> EvalStackValue.Int32
+                | _ -> failwith "TODO"
+
+            state
+            |> IlMachineState.pushToEvalStack' result currentThread
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Some
+        | "System.Private.CoreLib", "BitConverter", "Int32BitsToSingle" ->
+            match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
+            | [ ConcreteInt32 state.ConcreteTypes ], ConcreteSingle state.ConcreteTypes -> ()
+            | _ -> failwith "bad signature BitConverter.Int64BitsToSingle"
+
+            let arg, state = IlMachineState.popEvalStack currentThread state
+
+            let arg =
+                match arg with
+                | EvalStackValue.Int32 i -> i
+                | _ -> failwith "$TODO: {arr}"
+
+            let result =
+                BitConverter.Int32BitsToSingle arg |> CliNumericType.Float32 |> CliType.Numeric
+
+            state
+            |> IlMachineState.pushToEvalStack result currentThread
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Some
+        | "System.Private.CoreLib", "BitConverter", "Int64BitsToDouble" ->
+            match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
+            | [ ConcreteInt64 state.ConcreteTypes ], ConcreteDouble state.ConcreteTypes -> ()
+            | _ -> failwith "bad signature BitConverter.Int64BitsToDouble"
+
+            let arg, state = IlMachineState.popEvalStack currentThread state
+
+            let arg =
+                match arg with
+                | EvalStackValue.Int64 i -> i
+                | _ -> failwith "$TODO: {arr}"
+
+            let result =
+                BitConverter.Int64BitsToDouble arg |> CliNumericType.Float64 |> CliType.Numeric
+
+            state
+            |> IlMachineState.pushToEvalStack result currentThread
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Some
+        | "System.Private.CoreLib", "BitConverter", "DoubleToInt64Bits" ->
+            match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
+            | [ ConcreteDouble state.ConcreteTypes ], ConcreteInt64 state.ConcreteTypes -> ()
+            | _ -> failwith "bad signature BitConverter.DoubleToInt64Bits"
+
+            let arg, state = IlMachineState.popEvalStack currentThread state
+
+            let result =
+                match arg with
+                | EvalStackValue.Float f -> BitConverter.DoubleToInt64Bits f |> EvalStackValue.Int64
+                | _ -> failwith "TODO"
+
+            state
+            |> IlMachineState.pushToEvalStack' result currentThread
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> Some
+        | "System.Private.CoreLib", "String", "Equals" ->
+            match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
+            | [ ConcreteString state.ConcreteTypes ; ConcreteString state.ConcreteTypes ],
+              ConcreteBool state.ConcreteTypes ->
+                let arg1, state = IlMachineState.popEvalStack currentThread state
+
+                let arg1 =
+                    match arg1 with
+                    | EvalStackValue.ObjectRef h
+                    | EvalStackValue.ManagedPointer (ManagedPointerSource.Heap h) -> h
+                    | EvalStackValue.Int32 _
+                    | EvalStackValue.Int64 _
+                    | EvalStackValue.Float _ -> failwith $"this isn't a string! {arg1}"
+                    | _ -> failwith $"TODO: %O{arg1}"
+
+                let arg2, state = IlMachineState.popEvalStack currentThread state
+
+                let arg2 =
+                    match arg2 with
+                    | EvalStackValue.ObjectRef h
+                    | EvalStackValue.ManagedPointer (ManagedPointerSource.Heap h) -> h
+                    | 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 arg1 = ManagedHeap.Get arg1 state.ManagedHeap
+                let arg2 = ManagedHeap.Get arg2 state.ManagedHeap
+
+                if arg1.Fields.["_firstChar"] <> arg2.Fields.["_firstChar"] then
+                    state
+                    |> IlMachineState.pushToEvalStack (CliType.ofBool false) currentThread
+                    |> IlMachineState.advanceProgramCounter currentThread
+                    |> Some
+                else
+                    failwith "TODO"
+            | _ -> None
+        | "System.Private.CoreLib", "Unsafe", "ReadUnaligned" ->
+            let ptr, state = IlMachineState.popEvalStack currentThread state
+
+            let v : CliType =
+                let rec go ptr =
+                    match ptr with
+                    | EvalStackValue.ManagedPointer src ->
+                        match src with
+                        | ManagedPointerSource.LocalVariable (sourceThread, methodFrame, whichVar) -> failwith "todo"
+                        | ManagedPointerSource.Argument (sourceThread, methodFrame, whichVar) -> failwith "todo"
+                        | ManagedPointerSource.Heap managedHeapAddress -> failwith "todo"
+                        | ManagedPointerSource.ArrayIndex (arr, index) ->
+                            state |> IlMachineState.getArrayValue arr index
+                        | ManagedPointerSource.Null -> failwith "TODO: throw NRE"
+                    | EvalStackValue.NativeInt src -> failwith "TODO"
+                    | EvalStackValue.ObjectRef ptr -> failwith "TODO"
+                    | EvalStackValue.UserDefinedValueType [ _, field ] -> go field
+                    | EvalStackValue.UserDefinedValueType []
+                    | EvalStackValue.UserDefinedValueType (_ :: _ :: _)
+                    | EvalStackValue.Int32 _
+                    | EvalStackValue.Int64 _
+                    | EvalStackValue.Float _ -> failwith $"this isn't a pointer! {ptr}"
+
+                go ptr
+
+            let state =
+                state
+                |> IlMachineState.pushToEvalStack v currentThread
+                |> IlMachineState.advanceProgramCounter currentThread
+
+            Some state
+        | "System.Private.CoreLib", "String", "op_Implicit" ->
+            match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
+            | [ par ], ret ->
+                let par = state.ConcreteTypes |> AllConcreteTypes.lookup par |> Option.get
+                let ret = state.ConcreteTypes |> AllConcreteTypes.lookup ret |> Option.get
+
+                if
+                    par.Namespace = "System"
+                    && par.Name = "String"
+                    && ret.Namespace = "System"
+                    && ret.Name = "ReadOnlySpan`1"
+                then
+                    match ret.Generics |> Seq.toList with
+                    | [ gen ] ->
+                        let gen = state.ConcreteTypes |> AllConcreteTypes.lookup gen |> Option.get
+
+                        if gen.Namespace = "System" && gen.Name = "Char" then
+                            // This is just an optimisation
+                            // https://github.com/dotnet/runtime/blob/ab105b51f8b50ec5567d7cfe9001ca54dd6f64c3/src/libraries/System.Private.CoreLib/src/System/String.cs#L363-L366
+                            None
+                        else
+                            failwith "TODO: unexpected params to String.op_Implicit"
+                    | _ -> failwith "TODO: unexpected params to String.op_Implicit"
+                else
+                    failwith "TODO: unexpected params to String.op_Implicit"
+            | _ -> failwith "TODO: unexpected params to String.op_Implicit"
+        | "System.Private.CoreLib", "RuntimeHelpers", "IsReferenceOrContainsReferences" ->
+            // https://github.com/dotnet/runtime/blob/1d1bf92fcf43aa6981804dc53c5174445069c9e4/src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.CoreCLR.cs#L207
+            match methodToCall.Signature.ParameterTypes, methodToCall.Signature.ReturnType with
+            | [], ConcreteBool state.ConcreteTypes -> ()
+            | _ -> failwith "bad signature for System.Private.CoreLib.RuntimeHelpers.IsReferenceOrContainsReference"
+
+            let generic =
+                AllConcreteTypes.lookup (Seq.exactlyOne methodToCall.Generics) state.ConcreteTypes
+
+            let generic =
+                match generic with
+                | None -> failwith "somehow have not already concretised type in IsReferenceOrContainsReferences"
+                | Some generic -> generic
+
+            failwith $"TODO: do the thing on %O{generic}"
+        | "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
+            | [ ConcreteNonGenericArray state.ConcreteTypes ; ConcreteRuntimeFieldHandle state.ConcreteTypes ],
+              ConcreteVoid state.ConcreteTypes -> ()
+            | _ -> failwith "bad signature for System.Private.CoreLib.RuntimeHelpers.InitializeArray"
+
+            failwith "TODO: if arg0 is null, throw NRE"
+            failwith "TODO: if arg1 contains null handle, throw ArgumentException"
+
+            failwith "TODO: array initialization"
+        | "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
+        | a, b, c -> failwith $"TODO: implement JIT intrinsic {a}.{b}.{c}"
+        |> Option.map (fun s -> s.WithThreadSwitchedToAssembly callerAssy currentThread |> fst)

WoofWare.PawPrint/ManagedHeap.fs

@@ -9,7 +9,7 @@ type SyncBlock =
 type AllocatedNonArrayObject =
     {
         Fields : Map<string, CliType>
-        Type : WoofWare.PawPrint.TypeInfoCrate
+        ConcreteType : ConcreteTypeHandle
         SyncBlock : SyncBlock
     }
 
@@ -119,6 +119,10 @@ type ManagedHeap =
 
         arr.Elements.[offset]
 
+    static member Get (alloc : ManagedHeapAddress) (heap : ManagedHeap) : AllocatedNonArrayObject =
+        // TODO: arrays too
+        heap.NonArrayObjects.[alloc]
+
     static member SetArrayValue
         (alloc : ManagedHeapAddress)
         (offset : int)

WoofWare.PawPrint/MethodState.fs

@@ -137,7 +137,7 @@ and MethodState =
     /// If `method` is static, `args` must be of length numParams.
     static member Empty
         (concreteTypes : AllConcreteTypes)
-        (corelib : BaseClassTypes<DumpedAssembly>)
+        (baseClassTypes : BaseClassTypes<DumpedAssembly>)
         (loadedAssemblies : ImmutableDictionary<string, DumpedAssembly>)
         (containingAssembly : DumpedAssembly)
         (method : WoofWare.PawPrint.MethodInfo<ConcreteTypeHandle, ConcreteTypeHandle, ConcreteTypeHandle>)
@@ -172,7 +172,7 @@ and MethodState =
                 // Note: This assumes all types have already been concretized
                 // If this fails with "ConcreteTypeHandle not found", it means
                 // we need to ensure types are concretized before creating the MethodState
-                let zero, _ = CliType.zeroOf concreteTypes loadedAssemblies corelib var
+                let zero, _ = CliType.zeroOf concreteTypes loadedAssemblies baseClassTypes var
                 result.Add zero
 
             result.ToImmutable ()

WoofWare.PawPrint/NullaryIlOp.fs

@@ -46,7 +46,9 @@ module NullaryIlOp =
         | ManagedPointerSource.LocalVariable (sourceThread, methodFrame, whichVar) ->
             state.ThreadState.[sourceThread].MethodStates.[methodFrame].LocalVariables.[int<uint16> whichVar]
         | ManagedPointerSource.Heap managedHeapAddress -> failwith "TODO: Heap pointer dereferencing not implemented"
-        | ManagedPointerSource.ArrayIndex _ -> failwith "TODO: array index pointer dereferencing not implemented"
+        | ManagedPointerSource.ArrayIndex (arr, index) ->
+            let arr = state.ManagedHeap.Arrays.[arr]
+            arr.Elements.[index]
 
     // Unified Ldind implementation
     let private executeLdind
@@ -775,7 +777,7 @@ module NullaryIlOp =
             match
                 ExceptionHandling.findExceptionHandler
                     currentMethodState.IlOpIndex
-                    heapObject.Type
+                    heapObject.ConcreteType
                     currentMethodState.ExecutingMethod
                     state._LoadedAssemblies
             with

WoofWare.PawPrint/Program.fs

@@ -3,6 +3,7 @@ namespace WoofWare.PawPrint
 open System
 open System.Collections.Immutable
 open System.IO
+open System.Reflection.Metadata
 open Microsoft.Extensions.Logging
 
 [<RequireQualifiedAccess>]
@@ -14,10 +15,23 @@ module Program =
         (state : IlMachineState)
         : ManagedHeapAddress * IlMachineState
         =
+        let state, stringType =
+            TypeDefn.FromDefinition (
+                ComparableTypeDefinitionHandle.Make corelib.String.TypeDefHandle,
+                corelib.Corelib.Name.FullName,
+                SignatureTypeKind.Class
+            )
+            |> IlMachineState.concretizeType
+                corelib
+                state
+                corelib.Corelib.Name
+                ImmutableArray.Empty
+                ImmutableArray.Empty
+
         let argsAllocations, state =
             (state, args)
             ||> Seq.mapFold (fun state arg ->
-                IlMachineState.allocateManagedObject corelib.String (failwith "TODO: assert fields and populate") state
+                IlMachineState.allocateManagedObject stringType (failwith "TODO: assert fields and populate") state
             // TODO: set the char values in memory
             )
 
@@ -28,7 +42,7 @@ module Program =
             ((state, 0), argsAllocations)
             ||> Seq.fold (fun (state, i) arg ->
                 let state =
-                    IlMachineState.setArrayValue arrayAllocation (CliType.OfManagedObject arg) i state
+                    IlMachineState.setArrayValue arrayAllocation (CliType.ofManagedObject arg) i state
 
                 state, i + 1
             )
@@ -94,7 +108,7 @@ module Program =
             (currentAssembly : DumpedAssembly)
             (continueWithGeneric :
                 IlMachineState
-                    -> TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
+                    -> TypeInfo<GenericParamFromMetadata, TypeDefn>
                     -> DumpedAssembly
                     -> IlMachineState * BaseClassTypes<DumpedAssembly> option)
             (continueWithResolved :
@@ -145,7 +159,7 @@ module Program =
 
         let rec findCoreLibraryAssemblyFromGeneric
             (state : IlMachineState)
-            (currentType : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>)
+            (currentType : TypeInfo<GenericParamFromMetadata, TypeDefn>)
             (currentAssembly : DumpedAssembly)
             =
             match currentType.BaseType with
@@ -186,7 +200,7 @@ module Program =
                 // Use the original method from metadata, but convert FakeUnit to TypeDefn
                 let rawMainMethod =
                     mainMethodFromMetadata
-                    |> MethodInfo.mapTypeGenerics (fun i _ -> TypeDefn.GenericTypeParameter i)
+                    |> MethodInfo.mapTypeGenerics (fun (i, _) -> TypeDefn.GenericTypeParameter i.SequenceNumber)
 
                 let state, concretizedMainMethod, _ =
                     IlMachineState.concretizeMethodWithTypeGenerics
@@ -233,7 +247,7 @@ module Program =
             | Some baseTypes ->
                 let rawMainMethod =
                     mainMethodFromMetadata
-                    |> MethodInfo.mapTypeGenerics (fun i _ -> TypeDefn.GenericTypeParameter i)
+                    |> MethodInfo.mapTypeGenerics (fun (i, _) -> TypeDefn.GenericTypeParameter i.SequenceNumber)
 
                 IlMachineState.concretizeMethodWithTypeGenerics
                     loggerFactory
@@ -249,7 +263,11 @@ module Program =
         let rec loadInitialState (state : IlMachineState) =
             match
                 state
-                |> IlMachineState.loadClass loggerFactory (Option.toObj baseClassTypes) mainTypeHandle mainThread
+                |> IlMachineStateExecution.loadClass
+                    loggerFactory
+                    (Option.toObj baseClassTypes)
+                    mainTypeHandle
+                    mainThread
             with
             | StateLoadResult.NothingToDo ilMachineState -> ilMachineState
             | StateLoadResult.FirstLoadThis ilMachineState -> loadInitialState ilMachineState
@@ -297,7 +315,7 @@ module Program =
                     dumped
                     concretizedMainMethod
                     ImmutableArray.Empty
-                    (ImmutableArray.Create (CliType.OfManagedObject arrayAllocation))
+                    (ImmutableArray.Create (CliType.ofManagedObject arrayAllocation))
                     None
             with
             | Ok s -> s
@@ -313,7 +331,7 @@ module Program =
             { state with
                 ThreadState = state.ThreadState |> Map.add mainThread threadState
             }
-            |> IlMachineState.ensureTypeInitialised loggerFactory baseClassTypes mainThread mainTypeHandle
+            |> IlMachineStateExecution.ensureTypeInitialised loggerFactory baseClassTypes mainThread mainTypeHandle
 
         match init with
         | WhatWeDid.SuspendedForClassInit -> failwith "TODO: suspended for class init"

WoofWare.PawPrint/TypeHandleRegistry.fs

@@ -1,18 +1,10 @@
 namespace WoofWare.PawPrint
 
-type CanonicalTypeIdentity =
-    {
-        AssemblyFullName : string
-        FullyQualifiedTypeName : string
-        Generics : CanonicalTypeIdentity list
-    }
-
 type TypeHandleRegistry =
     private
         {
-            TypeHandleToType : Map<int64<typeHandle>, CanonicalTypeIdentity>
-            TypeToHandle : Map<CanonicalTypeIdentity, int64<typeHandle> * ManagedHeapAddress>
-            NextHandle : int64<typeHandle>
+            TypeHandleToType : Map<ManagedHeapAddress, ConcreteTypeHandle>
+            TypeToHandle : Map<ConcreteTypeHandle, ManagedHeapAddress>
         }
 
 [<RequireQualifiedAccess>]
@@ -21,23 +13,20 @@ module TypeHandleRegistry =
         {
             TypeHandleToType = Map.empty
             TypeToHandle = Map.empty
-            NextHandle = 1L<typeHandle>
         }
 
     /// Returns an allocated System.RuntimeType as well.
     let getOrAllocate
         (allocState : 'allocState)
         (allocate : (string * CliType) list -> 'allocState -> ManagedHeapAddress * 'allocState)
-        (def : CanonicalTypeIdentity)
+        (def : ConcreteTypeHandle)
         (reg : TypeHandleRegistry)
-        : (int64<typeHandle> * ManagedHeapAddress) * TypeHandleRegistry * 'allocState
+        : ManagedHeapAddress * TypeHandleRegistry * 'allocState
         =
         match Map.tryFind def reg.TypeToHandle with
         | Some v -> v, reg, allocState
         | None ->
 
-        let handle = reg.NextHandle
-
         // Here follows the class System.RuntimeType, which is an internal class type with a constructor
         // whose only purpose is to throw.
         let fields =
@@ -46,7 +35,7 @@ module TypeHandleRegistry =
                 "m_keepalive", CliType.ObjectRef None
                 // TODO: this is actually a System.IntPtr https://github.com/dotnet/runtime/blob/ec11903827fc28847d775ba17e0cd1ff56cfbc2e/src/coreclr/nativeaot/Runtime.Base/src/System/Primitives.cs#L339
                 "m_cache", CliType.Numeric (CliNumericType.NativeInt (NativeIntSource.Verbatim 0L))
-                "m_handle", CliType.Numeric (CliNumericType.NativeInt (NativeIntSource.TypeHandlePtr handle))
+                "m_handle", CliType.Numeric (CliNumericType.NativeInt (NativeIntSource.TypeHandlePtr def))
                 // This is the const -1, apparently?!
                 // https://github.com/dotnet/runtime/blob/f0168ee80ba9aca18a7e7140b2bb436defda623c/src/coreclr/System.Private.CoreLib/src/System/RuntimeType.CoreCLR.cs#L2496
                 "GenericParameterCountAny", CliType.Numeric (CliNumericType.Int32 -1)
@@ -56,9 +45,8 @@ module TypeHandleRegistry =
 
         let reg =
             {
-                NextHandle = handle + 1L<typeHandle>
-                TypeHandleToType = reg.TypeHandleToType |> Map.add handle def
-                TypeToHandle = reg.TypeToHandle |> Map.add def (handle, alloc)
+                TypeHandleToType = reg.TypeHandleToType |> Map.add alloc def
+                TypeToHandle = reg.TypeToHandle |> Map.add def alloc
             }
 
-        (handle, alloc), reg, state
+        alloc, reg, state

WoofWare.PawPrint/UnaryConstIlOp.fs

@@ -212,7 +212,33 @@ module internal UnaryConstIlOp =
                else
                    id
             |> Tuple.withRight WhatWeDid.Executed
-        | Blt_s b -> failwith "TODO: Blt_s unimplemented"
+        | Blt_s b ->
+            let value2, state = IlMachineState.popEvalStack currentThread state
+            let value1, state = IlMachineState.popEvalStack currentThread state
+
+            let isLessThan =
+                match value1, value2 with
+                | EvalStackValue.Int32 v1, EvalStackValue.Int32 v2 -> v1 < v2
+                | EvalStackValue.Int32 i, EvalStackValue.NativeInt nativeIntSource -> failwith "todo"
+                | EvalStackValue.Int32 i, _ -> failwith $"invalid comparison, {i} with {value2}"
+                | EvalStackValue.Int64 v1, EvalStackValue.Int64 v2 -> v1 < v2
+                | EvalStackValue.Int64 i, _ -> failwith $"invalid comparison, {i} with {value2}"
+                | EvalStackValue.NativeInt nativeIntSource, _ -> failwith "todo"
+                | EvalStackValue.Float v1, EvalStackValue.Float v2 -> failwith "todo"
+                | EvalStackValue.Float f, _ -> failwith $"invalid comparison, {f} with {value2}"
+                | EvalStackValue.ManagedPointer v1, EvalStackValue.ManagedPointer v2 -> failwith "todo"
+                | EvalStackValue.ManagedPointer v1, _ -> failwith $"invalid comparison, {v1} with {value2}"
+                | EvalStackValue.ObjectRef _, _ -> failwith "todo"
+                | EvalStackValue.UserDefinedValueType _, _ ->
+                    failwith "unexpectedly tried to compare user-defined value type"
+
+            state
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> if isLessThan then
+                   IlMachineState.jumpProgramCounter currentThread (int<int8> b)
+               else
+                   id
+            |> Tuple.withRight WhatWeDid.Executed
         | Ble_s b ->
             let value2, state = IlMachineState.popEvalStack currentThread state
             let value1, state = IlMachineState.popEvalStack currentThread state
@@ -240,7 +266,33 @@ module internal UnaryConstIlOp =
                else
                    id
             |> Tuple.withRight WhatWeDid.Executed
-        | Bgt_s b -> failwith "TODO: Bgt_s unimplemented"
+        | Bgt_s b ->
+            let value2, state = IlMachineState.popEvalStack currentThread state
+            let value1, state = IlMachineState.popEvalStack currentThread state
+
+            let isGreaterThan =
+                match value1, value2 with
+                | EvalStackValue.Int32 v1, EvalStackValue.Int32 v2 -> v1 > v2
+                | EvalStackValue.Int32 i, EvalStackValue.NativeInt nativeIntSource -> failwith "todo"
+                | EvalStackValue.Int32 i, _ -> failwith $"invalid comparison, {i} with {value2}"
+                | EvalStackValue.Int64 v1, EvalStackValue.Int64 v2 -> v1 > v2
+                | EvalStackValue.Int64 i, _ -> failwith $"invalid comparison, {i} with {value2}"
+                | EvalStackValue.NativeInt nativeIntSource, _ -> failwith "todo"
+                | EvalStackValue.Float v1, EvalStackValue.Float v2 -> failwith "todo"
+                | EvalStackValue.Float f, _ -> failwith $"invalid comparison, {f} with {value2}"
+                | EvalStackValue.ManagedPointer v1, EvalStackValue.ManagedPointer v2 -> failwith "todo"
+                | EvalStackValue.ManagedPointer v1, _ -> failwith $"invalid comparison, {v1} with {value2}"
+                | EvalStackValue.ObjectRef _, _ -> failwith "todo"
+                | EvalStackValue.UserDefinedValueType _, _ ->
+                    failwith "unexpectedly tried to compare user-defined value type"
+
+            state
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> if isGreaterThan then
+                   IlMachineState.jumpProgramCounter currentThread (int<int8> b)
+               else
+                   id
+            |> Tuple.withRight WhatWeDid.Executed
         | Bge_s b ->
             let value2, state = IlMachineState.popEvalStack currentThread state
             let value1, state = IlMachineState.popEvalStack currentThread state
@@ -351,7 +403,34 @@ module internal UnaryConstIlOp =
                else
                    id
             |> Tuple.withRight WhatWeDid.Executed
-        | Bne_un_s b -> failwith "TODO: Bne_un_s unimplemented"
+        | Bne_un_s b ->
+            // Table III.4
+            let value2, state = IlMachineState.popEvalStack currentThread state
+            let value1, state = IlMachineState.popEvalStack currentThread state
+
+            let isNotEqual =
+                match value1, value2 with
+                | EvalStackValue.Int32 v1, EvalStackValue.Int32 v2 -> v1 <> v2
+                | EvalStackValue.Int32 v1, EvalStackValue.NativeInt v2 -> failwith "TODO"
+                | EvalStackValue.Int32 v1, _ -> failwith $"invalid comparison, {v1} with {value2}"
+                | _, EvalStackValue.Int32 v2 -> failwith $"invalid comparison, {value1} with {v2}"
+                | EvalStackValue.Int64 v1, EvalStackValue.Int64 v2 -> v1 <> v2
+                | EvalStackValue.Int64 v1, _ -> failwith $"invalid comparison, {v1} with {value2}"
+                | _, EvalStackValue.Int64 v2 -> failwith $"invalid comparison, {value1} with {v2}"
+                | EvalStackValue.Float v1, EvalStackValue.Float v2 -> v1 <> v2
+                | _, EvalStackValue.Float v2 -> failwith $"invalid comparison, {value1} with {v2}"
+                | EvalStackValue.Float v1, _ -> failwith $"invalid comparison, {v1} with {value2}"
+                | EvalStackValue.NativeInt v1, EvalStackValue.NativeInt v2 -> v1 <> v2
+                | EvalStackValue.ManagedPointer ptr1, EvalStackValue.ManagedPointer ptr2 -> ptr1 <> ptr2
+                | _, _ -> failwith $"TODO {value1} {value2} (see table III.4)"
+
+            state
+            |> IlMachineState.advanceProgramCounter currentThread
+            |> if isNotEqual then
+                   IlMachineState.jumpProgramCounter currentThread (int b)
+               else
+                   id
+            |> Tuple.withRight WhatWeDid.Executed
         | Bge_un_s b ->
             let value2, state = IlMachineState.popEvalStack currentThread state
             let value1, state = IlMachineState.popEvalStack currentThread state

WoofWare.PawPrint/UnaryMetadataIlOp.fs

@@ -16,7 +16,10 @@ module internal UnaryMetadataIlOp =
         (thread : ThreadId)
         : IlMachineState * WhatWeDid
         =
+        let logger = loggerFactory.CreateLogger (op.ToString ())
+
         let activeAssy = state.ActiveAssembly thread
+        let currentMethod = state.ThreadState.[thread].MethodState.ExecutingMethod
 
         match op with
         | Call ->
@@ -29,7 +32,9 @@ module internal UnaryMetadataIlOp =
                     | MetadataToken.MethodDef token ->
                         let method =
                             activeAssy.Methods.[token]
-                            |> MethodInfo.mapTypeGenerics (fun i _ -> TypeDefn.GenericTypeParameter i)
+                            |> MethodInfo.mapTypeGenerics (fun (par, _) ->
+                                TypeDefn.GenericTypeParameter par.SequenceNumber
+                            )
 
                         state, method, Some spec.Signature, None
                     | MetadataToken.MemberReference ref ->
@@ -78,19 +83,20 @@ module internal UnaryMetadataIlOp =
                     typeArgsFromMetadata
                     state
 
-            match IlMachineState.loadClass loggerFactory baseClassTypes declaringTypeHandle thread state with
+            match IlMachineStateExecution.loadClass loggerFactory baseClassTypes declaringTypeHandle thread state with
             | NothingToDo state ->
                 let state, _ =
                     state.WithThreadSwitchedToAssembly methodToCall.DeclaringType.Assembly thread
 
                 let threadState = state.ThreadState.[thread]
 
-                IlMachineState.callMethod
+                IlMachineStateExecution.callMethod
                     loggerFactory
                     baseClassTypes
                     None
                     None
                     false
+                    false
                     true
                     concretizedMethod.Generics
                     concretizedMethod
@@ -112,7 +118,7 @@ module internal UnaryMetadataIlOp =
                     | MetadataToken.MethodDef token ->
                         let method =
                             activeAssy.Methods.[token]
-                            |> MethodInfo.mapTypeGenerics (fun i _ -> spec.Signature.[i])
+                            |> MethodInfo.mapTypeGenerics (fun (p, _) -> spec.Signature.[p.SequenceNumber])
 
                         state, method, Some spec.Signature, None
                     | MetadataToken.MemberReference ref ->
@@ -162,17 +168,18 @@ module internal UnaryMetadataIlOp =
                     typeArgsFromMetadata
                     state
 
-            match IlMachineState.loadClass loggerFactory baseClassTypes declaringTypeHandle thread state with
+            match IlMachineStateExecution.loadClass loggerFactory baseClassTypes declaringTypeHandle thread state with
             | FirstLoadThis state -> state, WhatWeDid.SuspendedForClassInit
             | NothingToDo state ->
 
             state.WithThreadSwitchedToAssembly methodToCall.DeclaringType.Assembly thread
             |> fst
-            |> IlMachineState.callMethodInActiveAssembly
+            |> IlMachineStateExecution.callMethodInActiveAssembly
                 loggerFactory
                 baseClassTypes
                 thread
                 true
+                true
                 methodGenerics
                 methodToCall
                 None
@@ -180,8 +187,6 @@ module internal UnaryMetadataIlOp =
 
         | Castclass -> failwith "TODO: Castclass unimplemented"
         | Newobj ->
-            let logger = loggerFactory.CreateLogger "Newobj"
-
             let state, assy, ctor, typeArgsFromMetadata =
                 match metadataToken with
                 | MethodDef md ->
@@ -206,8 +211,6 @@ module internal UnaryMetadataIlOp =
                     | Choice2Of2 _field -> failwith "unexpectedly NewObj found a constructor which is a field"
                 | x -> failwith $"Unexpected metadata token for constructor: %O{x}"
 
-            let currentMethod = state.ThreadState.[thread].MethodState.ExecutingMethod
-
             let state, concretizedCtor, declaringTypeHandle =
                 IlMachineState.concretizeMethodForExecution
                     loggerFactory
@@ -219,7 +222,12 @@ module internal UnaryMetadataIlOp =
                     state
 
             let state, init =
-                IlMachineState.ensureTypeInitialised loggerFactory baseClassTypes thread declaringTypeHandle state
+                IlMachineStateExecution.ensureTypeInitialised
+                    loggerFactory
+                    baseClassTypes
+                    thread
+                    declaringTypeHandle
+                    state
 
             match init with
             | WhatWeDid.BlockedOnClassInit state -> failwith "TODO: another thread is running the initialiser"
@@ -236,11 +244,15 @@ module internal UnaryMetadataIlOp =
                     ctorType.Name
                 )
 
-            let typeGenerics =
-                concretizedCtor.DeclaringType.Generics |> ImmutableArray.CreateRange
+            let typeGenerics = concretizedCtor.DeclaringType.Generics
 
             let state, fieldZeros =
-                ((state, []), ctorType.Fields)
+                // Only include instance fields when constructing objects
+                let instanceFields =
+                    ctorType.Fields
+                    |> List.filter (fun field -> not (field.Attributes.HasFlag FieldAttributes.Static))
+
+                ((state, []), instanceFields)
                 ||> List.fold (fun (state, zeros) field ->
                     // TODO: generics
                     let state, zero =
@@ -264,7 +276,15 @@ module internal UnaryMetadataIlOp =
             // On completion of the constructor, we'll copy the value back off the heap,
             // and put it on the eval stack directly.
             let allocatedAddr, state =
-                IlMachineState.allocateManagedObject ctorType fields state
+                let ty =
+                    (concretizedCtor.DeclaringType.Assembly,
+                     concretizedCtor.DeclaringType.Namespace,
+                     concretizedCtor.DeclaringType.Name,
+                     concretizedCtor.DeclaringType.Generics)
+                    |> AllConcreteTypes.findExistingConcreteType state.ConcreteTypes
+                    |> Option.get
+
+                IlMachineState.allocateManagedObject ty fields state
 
             let state =
                 state
@@ -275,10 +295,11 @@ module internal UnaryMetadataIlOp =
             let state, whatWeDid =
                 state.WithThreadSwitchedToAssembly assy thread
                 |> fst
-                |> IlMachineState.callMethodInActiveAssembly
+                |> IlMachineStateExecution.callMethodInActiveAssembly
                     loggerFactory
                     baseClassTypes
                     thread
+                    false
                     true
                     None
                     ctor
@@ -294,11 +315,11 @@ module internal UnaryMetadataIlOp =
             state, WhatWeDid.Executed
         | Newarr ->
             let currentState = state.ThreadState.[thread]
-            let popped, newMethodState = MethodState.popFromStack currentState.MethodState
+            let popped, methodState = MethodState.popFromStack currentState.MethodState
 
             let currentState =
                 { currentState with
-                    MethodStates = currentState.MethodStates.SetItem (currentState.ActiveMethodState, newMethodState)
+                    MethodStates = currentState.MethodStates.SetItem (currentState.ActiveMethodState, methodState)
                 }
 
             let len =
@@ -306,96 +327,24 @@ module internal UnaryMetadataIlOp =
                 | EvalStackValue.Int32 v -> v
                 | popped -> failwith $"unexpectedly popped value %O{popped} to serve as array len"
 
-            let typeGenerics =
-                newMethodState.ExecutingMethod.DeclaringType.Generics
-                |> ImmutableArray.CreateRange
+            let typeGenerics = currentMethod.DeclaringType.Generics
 
             let state, elementType, assy =
                 match metadataToken with
                 | MetadataToken.TypeDefinition defn ->
-                    let assy = state.LoadedAssembly currentState.ActiveAssembly |> Option.get
-                    let defn = assy.TypeDefs.[defn]
+                    let state, resolved =
+                        IlMachineState.lookupTypeDefn baseClassTypes state activeAssy defn
 
-                    let baseType =
-                        defn.BaseType
-                        |> DumpedAssembly.resolveBaseType baseClassTypes state._LoadedAssemblies defn.Assembly
-
-                    let signatureTypeKind =
-                        match baseType with
-                        | ResolvedBaseType.Enum
-                        | ResolvedBaseType.ValueType -> SignatureTypeKind.ValueType
-                        | ResolvedBaseType.Object -> SignatureTypeKind.Class
-                        | ResolvedBaseType.Delegate -> SignatureTypeKind.Class
-
-                    let result =
-                        if defn.Generics.IsEmpty then
-                            TypeDefn.FromDefinition (
-                                ComparableTypeDefinitionHandle.Make defn.TypeDefHandle,
-                                defn.Assembly.FullName,
-                                signatureTypeKind
-                            )
-                        else
-                            // Preserve the generic instantiation by converting GenericParameters to TypeDefn.GenericTypeParameter
-                            let genericDef =
-                                TypeDefn.FromDefinition (
-                                    ComparableTypeDefinitionHandle.Make defn.TypeDefHandle,
-                                    defn.Assembly.FullName,
-                                    signatureTypeKind
-                                )
-
-                            let genericArgs =
-                                defn.Generics
-                                |> Seq.mapi (fun i _ -> TypeDefn.GenericTypeParameter i)
-                                |> ImmutableArray.CreateRange
-
-                            TypeDefn.GenericInstantiation (genericDef, genericArgs)
-
-                    state, result, assy
-                | MetadataToken.TypeSpecification spec ->
-                    let assy = state.LoadedAssembly currentState.ActiveAssembly |> Option.get
-                    state, assy.TypeSpecs.[spec].Signature, assy
+                    state, resolved, activeAssy
+                | MetadataToken.TypeSpecification spec -> state, activeAssy.TypeSpecs.[spec].Signature, activeAssy
                 | MetadataToken.TypeReference ref ->
-                    let ref = state.ActiveAssembly(thread).TypeRefs.[ref]
-
-                    // Convert ConcreteTypeHandles back to TypeDefn for metadata operations
-                    let typeGenerics =
-                        newMethodState.ExecutingMethod.DeclaringType.Generics
-                        |> Seq.map (fun handle ->
-                            Concretization.concreteHandleToTypeDefn
-                                baseClassTypes
-                                handle
-                                state.ConcreteTypes
-                                state._LoadedAssemblies
-                        )
-                        |> ImmutableArray.CreateRange
-
-                    let state, assy, resolved =
-                        IlMachineState.resolveTypeFromRef
-                            loggerFactory
-                            (state.ActiveAssembly thread)
-                            ref
-                            typeGenerics
-                            state
-
-                    let baseType =
-                        resolved.BaseType
-                        |> DumpedAssembly.resolveBaseType baseClassTypes state._LoadedAssemblies assy.Name
-
-                    let signatureTypeKind =
-                        match baseType with
-                        | ResolvedBaseType.Enum
-                        | ResolvedBaseType.ValueType -> SignatureTypeKind.ValueType
-                        | ResolvedBaseType.Object -> SignatureTypeKind.Class
-                        | ResolvedBaseType.Delegate -> SignatureTypeKind.Class
-
-                    let result =
-                        TypeDefn.FromDefinition (
-                            ComparableTypeDefinitionHandle.Make resolved.TypeDefHandle,
-                            assy.Name.FullName,
-                            signatureTypeKind
-                        )
-
-                    state, result, assy
+                    IlMachineState.lookupTypeRef
+                        loggerFactory
+                        baseClassTypes
+                        state
+                        activeAssy
+                        currentMethod.DeclaringType.Generics
+                        ref
                 | x -> failwith $"TODO: Newarr element type resolution unimplemented for {x}"
 
             let state, zeroOfType =
@@ -405,7 +354,7 @@ module internal UnaryMetadataIlOp =
                     assy
                     elementType
                     typeGenerics
-                    newMethodState.Generics
+                    methodState.Generics
                     state
 
             let alloc, state = IlMachineState.allocateArray (fun () -> zeroOfType) len state
@@ -454,7 +403,7 @@ module internal UnaryMetadataIlOp =
         | Isinst ->
             let actualObj, state = IlMachineState.popEvalStack thread state
 
-            let targetType : TypeDefn =
+            let state, targetType =
                 match metadataToken with
                 | MetadataToken.TypeDefinition td ->
                     let activeAssy = state.ActiveAssembly thread
@@ -474,10 +423,46 @@ module internal UnaryMetadataIlOp =
                         | ResolvedBaseType.Object -> SignatureTypeKind.Class
                         | ResolvedBaseType.Delegate -> SignatureTypeKind.Class
 
+                    state,
                     TypeDefn.FromDefinition (ComparableTypeDefinitionHandle.Make td, activeAssy.Name.FullName, sigType)
-                | MetadataToken.TypeSpecification handle -> state.ActiveAssembly(thread).TypeSpecs.[handle].Signature
+                | MetadataToken.TypeSpecification handle ->
+                    state, state.ActiveAssembly(thread).TypeSpecs.[handle].Signature
+                | MetadataToken.TypeReference handle ->
+                    let state, assy, resol =
+                        IlMachineState.resolveTypeFromRef
+                            loggerFactory
+                            activeAssy
+                            (state.ActiveAssembly(thread).TypeRefs.[handle])
+                            ImmutableArray.Empty
+                            state
+
+                    let baseTy =
+                        DumpedAssembly.resolveBaseType baseClassTypes state._LoadedAssemblies assy.Name resol.BaseType
+
+                    let sigType =
+                        match baseTy with
+                        | ResolvedBaseType.Enum
+                        | ResolvedBaseType.ValueType -> SignatureTypeKind.ValueType
+                        | ResolvedBaseType.Object -> SignatureTypeKind.Class
+                        | ResolvedBaseType.Delegate -> SignatureTypeKind.Class
+
+                    state,
+                    TypeDefn.FromDefinition (
+                        ComparableTypeDefinitionHandle.Make resol.TypeDefHandle,
+                        assy.Name.FullName,
+                        sigType
+                    )
                 | m -> failwith $"unexpected metadata token {m} in IsInst"
 
+            let state, targetConcreteType =
+                IlMachineState.concretizeType
+                    baseClassTypes
+                    state
+                    activeAssy.Name
+                    currentMethod.DeclaringType.Generics
+                    currentMethod.Generics
+                    targetType
+
             let returnObj =
                 match actualObj with
                 | EvalStackValue.ManagedPointer ManagedPointerSource.Null ->
@@ -487,10 +472,10 @@ module internal UnaryMetadataIlOp =
                 | EvalStackValue.ManagedPointer (ManagedPointerSource.Heap addr) ->
                     match state.ManagedHeap.NonArrayObjects.TryGetValue addr with
                     | true, v ->
-                        { new TypeInfoEval<_> with
-                            member _.Eval typeInfo = failwith "TODO"
-                        }
-                        |> v.Type.Apply
+                        if v.ConcreteType = targetConcreteType then
+                            actualObj
+                        else
+                            failwith $"TODO: is {v.ConcreteType} an instance of {targetType} ({targetConcreteType})"
                     | false, _ ->
 
                     match state.ManagedHeap.Arrays.TryGetValue addr with
@@ -510,7 +495,7 @@ module internal UnaryMetadataIlOp =
                 | MetadataToken.FieldDefinition f ->
                     let field =
                         activeAssy.Fields.[f]
-                        |> FieldInfo.mapTypeGenerics (fun _ _ -> failwith "no generics allowed in FieldDefinition")
+                        |> FieldInfo.mapTypeGenerics (fun _ -> failwith "no generics allowed in FieldDefinition")
 
                     state, field
                 | MetadataToken.MemberReference mr ->
@@ -523,8 +508,6 @@ module internal UnaryMetadataIlOp =
                 | t -> failwith $"Unexpectedly asked to store to a non-field: {t}"
 
             do
-                let logger = loggerFactory.CreateLogger "Stfld"
-
                 logger.LogInformation (
                     "Storing in object field {FieldAssembly}.{FieldDeclaringType}.{FieldName} (type {FieldType})",
                     field.DeclaringType.Assembly.Name,
@@ -607,7 +590,7 @@ module internal UnaryMetadataIlOp =
                     | true, field ->
                         let field =
                             field
-                            |> FieldInfo.mapTypeGenerics (fun _ _ -> failwith "no generics allowed in FieldDefinition")
+                            |> FieldInfo.mapTypeGenerics (fun _ -> failwith "no generics allowed in FieldDefinition")
 
                         state, field
                 | MetadataToken.MemberReference mr ->
@@ -627,8 +610,6 @@ module internal UnaryMetadataIlOp =
                 | t -> failwith $"Unexpectedly asked to store to a non-field: {t}"
 
             do
-                let logger = loggerFactory.CreateLogger "Stsfld"
-
                 let declaring =
                     state.ActiveAssembly(thread).TypeDefs.[field.DeclaringType.Definition.Get]
 
@@ -643,7 +624,7 @@ module internal UnaryMetadataIlOp =
             let state, declaringTypeHandle, typeGenerics =
                 IlMachineState.concretizeFieldForExecution loggerFactory baseClassTypes thread field state
 
-            match IlMachineState.loadClass loggerFactory baseClassTypes declaringTypeHandle thread state with
+            match IlMachineStateExecution.loadClass loggerFactory baseClassTypes declaringTypeHandle thread state with
             | FirstLoadThis state -> state, WhatWeDid.SuspendedForClassInit
             | NothingToDo state ->
 
@@ -673,7 +654,7 @@ module internal UnaryMetadataIlOp =
                 | MetadataToken.FieldDefinition f ->
                     let field =
                         activeAssy.Fields.[f]
-                        |> FieldInfo.mapTypeGenerics (fun _ _ -> failwith "no generics allowed on FieldDefinition")
+                        |> FieldInfo.mapTypeGenerics (fun _ -> failwith "no generics allowed on FieldDefinition")
 
                     state, field
                 | MetadataToken.MemberReference mr ->
@@ -686,7 +667,6 @@ module internal UnaryMetadataIlOp =
                 | t -> failwith $"Unexpectedly asked to load from a non-field: {t}"
 
             do
-                let logger = loggerFactory.CreateLogger "Ldfld"
                 let declaring = activeAssy.TypeDefs.[field.DeclaringType.Definition.Get]
 
                 logger.LogInformation (
@@ -767,8 +747,6 @@ module internal UnaryMetadataIlOp =
 
         | Ldflda -> failwith "TODO: Ldflda unimplemented"
         | Ldsfld ->
-            let logger = loggerFactory.CreateLogger "Ldsfld"
-
             let state, field =
                 match metadataToken with
                 | MetadataToken.FieldDefinition fieldHandle ->
@@ -777,7 +755,7 @@ module internal UnaryMetadataIlOp =
                     | true, field ->
                         let field =
                             field
-                            |> FieldInfo.mapTypeGenerics (fun _ _ -> failwith "generics not allowed in FieldDefinition")
+                            |> FieldInfo.mapTypeGenerics (fun _ -> failwith "generics not allowed in FieldDefinition")
 
                         state, field
                 | MetadataToken.MemberReference mr ->
@@ -806,7 +784,7 @@ module internal UnaryMetadataIlOp =
             let state, declaringTypeHandle, typeGenerics =
                 IlMachineState.concretizeFieldForExecution loggerFactory baseClassTypes thread field state
 
-            match IlMachineState.loadClass loggerFactory baseClassTypes declaringTypeHandle thread state with
+            match IlMachineStateExecution.loadClass loggerFactory baseClassTypes declaringTypeHandle thread state with
             | FirstLoadThis state -> state, WhatWeDid.SuspendedForClassInit
             | NothingToDo state ->
 
@@ -827,8 +805,6 @@ module internal UnaryMetadataIlOp =
                 | Some v -> v, state
 
             do
-                let logger = loggerFactory.CreateLogger "Ldsfld"
-
                 let declaring =
                     state
                         .LoadedAssembly(field.DeclaringType.Assembly)
@@ -851,28 +827,22 @@ module internal UnaryMetadataIlOp =
 
         | Unbox_Any -> failwith "TODO: Unbox_Any unimplemented"
         | Stelem ->
-            let assy =
-                state.LoadedAssembly state.ThreadState.[thread].ActiveAssembly |> Option.get
-
-            let currentMethod = state.ThreadState.[thread].MethodState.ExecutingMethod
-
-            let declaringTypeGenerics =
-                currentMethod.DeclaringType.Generics |> ImmutableArray.CreateRange
+            let declaringTypeGenerics = currentMethod.DeclaringType.Generics
 
             let state, assy, elementType =
                 match metadataToken with
                 | MetadataToken.TypeDefinition defn ->
                     state,
-                    assy,
-                    assy.TypeDefs.[defn]
-                    |> TypeInfo.mapGeneric (fun _ p -> TypeDefn.GenericTypeParameter p.SequenceNumber)
+                    activeAssy,
+                    activeAssy.TypeDefs.[defn]
+                    |> TypeInfo.mapGeneric (fun (p, _) -> TypeDefn.GenericTypeParameter p.SequenceNumber)
                 | MetadataToken.TypeSpecification spec ->
                     let state, assy, ty =
                         IlMachineState.resolveTypeFromSpecConcrete
                             loggerFactory
                             baseClassTypes
                             spec
-                            assy
+                            activeAssy
                             declaringTypeGenerics
                             currentMethod.Generics
                             state
@@ -921,28 +891,22 @@ module internal UnaryMetadataIlOp =
             |> Tuple.withRight WhatWeDid.Executed
 
         | Ldelem ->
-            let assy =
-                state.LoadedAssembly state.ThreadState.[thread].ActiveAssembly |> Option.get
-
-            let currentMethod = state.ThreadState.[thread].MethodState.ExecutingMethod
-
-            let declaringTypeGenerics =
-                currentMethod.DeclaringType.Generics |> ImmutableArray.CreateRange
+            let declaringTypeGenerics = currentMethod.DeclaringType.Generics
 
             let state, assy, elementType =
                 match metadataToken with
                 | MetadataToken.TypeDefinition defn ->
                     state,
-                    assy,
-                    assy.TypeDefs.[defn]
-                    |> TypeInfo.mapGeneric (fun _ p -> TypeDefn.GenericTypeParameter p.SequenceNumber)
+                    activeAssy,
+                    activeAssy.TypeDefs.[defn]
+                    |> TypeInfo.mapGeneric (fun (p, _) -> TypeDefn.GenericTypeParameter p.SequenceNumber)
                 | MetadataToken.TypeSpecification spec ->
                     let state, assy, ty =
                         IlMachineState.resolveTypeFromSpecConcrete
                             loggerFactory
                             baseClassTypes
                             spec
-                            assy
+                            activeAssy
                             declaringTypeGenerics
                             currentMethod.Generics
                             state
@@ -989,13 +953,13 @@ module internal UnaryMetadataIlOp =
                     | false, _ -> failwith "TODO: Ldsflda - throw MissingFieldException"
                     | true, field ->
                         field
-                        |> FieldInfo.mapTypeGenerics (fun _ _ -> failwith "generics not allowed on FieldDefinition")
+                        |> FieldInfo.mapTypeGenerics (fun _ -> failwith "generics not allowed on FieldDefinition")
                 | t -> failwith $"Unexpectedly asked to load a non-field: {t}"
 
             let state, declaringTypeHandle, typeGenerics =
                 IlMachineState.concretizeFieldForExecution loggerFactory baseClassTypes thread field state
 
-            match IlMachineState.loadClass loggerFactory baseClassTypes declaringTypeHandle thread state with
+            match IlMachineStateExecution.loadClass loggerFactory baseClassTypes declaringTypeHandle thread state with
             | FirstLoadThis state -> state, WhatWeDid.SuspendedForClassInit
             | NothingToDo state ->
 
@@ -1025,14 +989,12 @@ module internal UnaryMetadataIlOp =
                 failwith "TODO: Ldsflda - push unmanaged pointer"
 
         | Ldftn ->
-            let logger = loggerFactory.CreateLogger "Ldftn"
-
-            let (method : MethodInfo<TypeDefn, WoofWare.PawPrint.GenericParameter, TypeDefn>), methodGenerics =
+            let method, methodGenerics =
                 match metadataToken with
                 | MetadataToken.MethodDef handle ->
                     let method =
                         activeAssy.Methods.[handle]
-                        |> MethodInfo.mapTypeGenerics (fun i _ -> TypeDefn.GenericTypeParameter i)
+                        |> MethodInfo.mapTypeGenerics (fun (par, _) -> TypeDefn.GenericTypeParameter par.SequenceNumber)
 
                     method, None
                 | MetadataToken.MethodSpecification h ->
@@ -1042,7 +1004,9 @@ module internal UnaryMetadataIlOp =
                     | MetadataToken.MethodDef token ->
                         let method =
                             activeAssy.Methods.[token]
-                            |> MethodInfo.mapTypeGenerics (fun i _ -> TypeDefn.GenericTypeParameter i)
+                            |> MethodInfo.mapTypeGenerics (fun (par, _) ->
+                                TypeDefn.GenericTypeParameter par.SequenceNumber
+                            )
 
                         method, Some spec.Signature
                     | k -> failwith $"Unrecognised MethodSpecification kind: %O{k}"
@@ -1077,19 +1041,103 @@ module internal UnaryMetadataIlOp =
             let state =
                 match metadataToken with
                 | MetadataToken.FieldDefinition h ->
-                    let ty = baseClassTypes.RuntimeFieldHandle
-                    // this is a struct; it contains one field, an IRuntimeFieldInfo
-                    // https://github.com/dotnet/runtime/blob/1d1bf92fcf43aa6981804dc53c5174445069c9e4/src/coreclr/System.Private.CoreLib/src/System/RuntimeHandles.cs#L1097
-                    let field = ty.Fields |> List.exactlyOne
+                    // TODO: how do we know what concrete type this is a field on?
+                    let runtimeFieldHandle, state =
+                        IlMachineState.getOrAllocateField loggerFactory baseClassTypes activeAssy.Name h state
 
-                    if field.Name <> "m_ptr" then
-                        failwith $"unexpected field name ${field.Name} for BCL type RuntimeFieldHandle"
-
-                    failwith ""
+                    IlMachineState.pushToEvalStack runtimeFieldHandle thread state
                 | MetadataToken.MethodDef h ->
                     let ty = baseClassTypes.RuntimeMethodHandle
                     let field = ty.Fields |> List.exactlyOne
                     failwith ""
+                | MetadataToken.TypeSpecification 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 typeGenerics = currentMethod.DeclaringType.Generics
+                    let methodGenerics = currentMethod.Generics
+
+                    let state, assy, typeDefn =
+                        IlMachineState.resolveTypeFromSpecConcrete
+                            loggerFactory
+                            baseClassTypes
+                            h
+                            activeAssy
+                            typeGenerics
+                            methodGenerics
+                            state
+
+                    let stk =
+                        match
+                            DumpedAssembly.resolveBaseType
+                                baseClassTypes
+                                state._LoadedAssemblies
+                                assy.Name
+                                typeDefn.BaseType
+                        with
+                        | ResolvedBaseType.ValueType
+                        | ResolvedBaseType.Enum -> SignatureTypeKind.ValueType
+                        | ResolvedBaseType.Delegate
+                        | ResolvedBaseType.Object -> SignatureTypeKind.Class
+
+                    let typeDefn =
+                        TypeDefn.FromDefinition (
+                            ComparableTypeDefinitionHandle.Make typeDefn.TypeDefHandle,
+                            assy.Name.FullName,
+                            stk
+                        )
+
+                    let state, handle =
+                        IlMachineState.concretizeType
+                            baseClassTypes
+                            state
+                            assy.Name
+                            typeGenerics
+                            methodGenerics
+                            typeDefn
+
+                    let alloc, state = IlMachineState.getOrAllocateType baseClassTypes handle state
+
+                    let vt =
+                        {
+                            Fields = [ "m_type", CliType.ObjectRef (Some alloc) ]
+                        }
+
+                    IlMachineState.pushToEvalStack (CliType.ValueType vt) thread state
+                | MetadataToken.TypeReference 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, assy =
+                        IlMachineState.lookupTypeRef loggerFactory baseClassTypes state activeAssy typeGenerics h
+
+                    let state, handle =
+                        IlMachineState.concretizeType
+                            baseClassTypes
+                            state
+                            assy.Name
+                            typeGenerics
+                            methodGenerics
+                            typeDefn
+
+                    let alloc, state = IlMachineState.getOrAllocateType baseClassTypes handle state
+
+                    let vt =
+                        {
+                            Fields = [ "m_type", CliType.ObjectRef (Some alloc) ]
+                        }
+
+                    IlMachineState.pushToEvalStack (CliType.ValueType vt) thread state
                 | MetadataToken.TypeDefinition h ->
                     let ty = baseClassTypes.RuntimeTypeHandle
                     let field = ty.Fields |> List.exactlyOne
@@ -1097,26 +1145,30 @@ module internal UnaryMetadataIlOp =
                     if field.Name <> "m_type" then
                         failwith $"unexpected field name ${field.Name} for BCL type RuntimeTypeHandle"
 
-                    let currentMethod = state.ThreadState.[thread].MethodState
-
                     let methodGenerics = currentMethod.Generics
 
-                    let typeGenerics = currentMethod.ExecutingMethod.DeclaringType.Generics
+                    let typeGenerics = currentMethod.DeclaringType.Generics
 
-                    if not (methodGenerics.IsEmpty && typeGenerics.IsEmpty) then
-                        failwith "TODO: generics"
+                    let state, typeDefn =
+                        IlMachineState.lookupTypeDefn baseClassTypes state activeAssy h
 
-                    let handle =
-                        match IlMachineState.canonicaliseTypeDef (state.ActiveAssembly(thread).Name) h [] [] state with
-                        | Error e -> failwith $"TODO: somehow need to load {e.FullName} first"
-                        | Ok h -> h
+                    let state, handle =
+                        IlMachineState.concretizeType
+                            baseClassTypes
+                            state
+                            activeAssy.Name
+                            typeGenerics
+                            methodGenerics
+                            typeDefn
 
-                    let (_, alloc), state = IlMachineState.getOrAllocateType baseClassTypes handle state
+                    let alloc, state = IlMachineState.getOrAllocateType baseClassTypes handle state
 
-                    IlMachineState.pushToEvalStack
-                        (CliType.ValueType [ "m_type", CliType.ObjectRef (Some alloc) ])
-                        thread
-                        state
+                    let vt =
+                        {
+                            Fields = [ "m_type", CliType.ObjectRef (Some alloc) ]
+                        }
+
+                    IlMachineState.pushToEvalStack (CliType.ValueType vt) thread state
                 | _ -> failwith $"Unexpected metadata token %O{metadataToken} in LdToken"
 
             state
@@ -1124,7 +1176,39 @@ module internal UnaryMetadataIlOp =
             |> Tuple.withRight WhatWeDid.Executed
         | Cpobj -> failwith "TODO: Cpobj unimplemented"
         | Ldobj -> failwith "TODO: Ldobj unimplemented"
-        | Sizeof -> failwith "TODO: Sizeof unimplemented"
+        | Sizeof ->
+            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
+                | _ -> failwith $"unexpected token {metadataToken} in Sizeof"
+
+            let state, typeHandle =
+                IlMachineState.concretizeType
+                    baseClassTypes
+                    state
+                    assy.Name
+                    currentMethod.DeclaringType.Generics
+                    currentMethod.Generics
+                    ty
+
+            let zero, state = IlMachineState.cliTypeZeroOfHandle state baseClassTypes typeHandle
+
+            let size = CliType.sizeOf zero
+
+            state
+            |> IlMachineState.pushToEvalStack (CliType.Numeric (CliNumericType.Int32 size)) thread
+            |> IlMachineState.advanceProgramCounter thread
+            |> Tuple.withRight WhatWeDid.Executed
         | Calli -> failwith "TODO: Calli unimplemented"
         | Unbox -> failwith "TODO: Unbox unimplemented"
         | Ldvirtftn -> failwith "TODO: Ldvirtftn unimplemented"

WoofWare.PawPrint/UnaryStringTokenIlOp.fs

@@ -1,12 +1,14 @@
 namespace WoofWare.PawPrint
 
+open System.Collections.Immutable
 open System.Reflection
+open System.Reflection.Metadata
 
 [<RequireQualifiedAccess>]
 [<CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
 module internal UnaryStringTokenIlOp =
     let execute
-        (baseClassTypes : BaseClassTypes<'a>)
+        (baseClassTypes : BaseClassTypes<DumpedAssembly>)
         (op : UnaryStringTokenIlOp)
         (sh : StringToken)
         (state : IlMachineState)
@@ -47,12 +49,24 @@ module internal UnaryStringTokenIlOp =
 
                     let fields =
                         [
-                            "_firstChar", CliType.OfChar state.ManagedHeap.StringArrayData.[dataAddr]
+                            "_firstChar", CliType.ofChar state.ManagedHeap.StringArrayData.[dataAddr]
                             "_stringLength", CliType.Numeric (CliNumericType.Int32 stringToAllocate.Length)
                         ]
 
-                    let addr, state =
-                        IlMachineState.allocateManagedObject baseClassTypes.String fields state
+                    let state, stringType =
+                        TypeDefn.FromDefinition (
+                            ComparableTypeDefinitionHandle.Make baseClassTypes.String.TypeDefHandle,
+                            baseClassTypes.Corelib.Name.FullName,
+                            SignatureTypeKind.Class
+                        )
+                        |> IlMachineState.concretizeType
+                            baseClassTypes
+                            state
+                            baseClassTypes.Corelib.Name
+                            ImmutableArray.Empty
+                            ImmutableArray.Empty
+
+                    let addr, state = IlMachineState.allocateManagedObject stringType fields state
 
                     addr,
                     { state with

WoofWare.PawPrint/WoofWare.PawPrint.fsproj

@@ -7,11 +7,13 @@
 
   <ItemGroup>
     <Compile Include="Tuple.fs" />
+    <Compile Include="ImmutableArray.fs" />
     <Compile Include="Result.fs" />
     <Compile Include="Corelib.fs" />
     <Compile Include="AbstractMachineDomain.fs" />
     <Compile Include="BasicCliType.fs" />
     <Compile Include="TypeHandleRegistry.fs" />
+    <Compile Include="FieldHandleRegistry.fs" />
     <Compile Include="ManagedHeap.fs" />
     <Compile Include="TypeInitialisation.fs" />
     <Compile Include="Exceptions.fs" />
@@ -21,6 +23,8 @@
     <Compile Include="MethodState.fs" />
     <Compile Include="ThreadState.fs" />
     <Compile Include="IlMachineState.fs" />
+    <Compile Include="Intrinsics.fs" />
+    <Compile Include="IlMachineStateExecution.fs" />
     <Compile Include="NullaryIlOp.fs" />
     <Compile Include="UnaryMetadataIlOp.fs" />
     <Compile Include="UnaryStringTokenIlOp.fs" />

flake.lock

@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1750836778,
-        "narHash": "sha256-sRLyRiC7TezRbbjGJwUFOgb2xMbSr3wQ0oJKfYlQ6s0=",
+        "lastModified": 1755736253,
+        "narHash": "sha256-jlIQRypNhB1PcB1BE+expE4xZeJxzoAGr1iUbHQta8s=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "d7bb1922f0bb3d0c990f56f9cdb767fdb20a5f22",
+        "rev": "596312aae91421d6923f18cecce934a7d3bfd6b8",
         "type": "github"
       },
       "original": {

nix/deps.json

@@ -21,8 +21,8 @@
   },
   {
     "pname": "FSharp.Core",
-    "version": "9.0.202",
-    "hash": "sha256-64Gub0qemmCoMa1tDus6TeTuB1+5sHfE6KD2j4o84mA="
+    "version": "9.0.303",
+    "hash": "sha256-AxR6wqodeU23KOTgkUfIgbavgbcSuzD4UBP+tiFydgA="
   },
   {
     "pname": "FsUnit",
@@ -31,33 +31,33 @@
   },
   {
     "pname": "Microsoft.ApplicationInsights",
-    "version": "2.22.0",
-    "hash": "sha256-mUQ63atpT00r49ca50uZu2YCiLg3yd6r3HzTryqcuEA="
+    "version": "2.23.0",
+    "hash": "sha256-5sf3bg7CZZjHseK+F3foOchEhmVeioePxMZVvS6Rjb0="
   },
   {
     "pname": "Microsoft.AspNetCore.App.Ref",
-    "version": "8.0.17",
-    "hash": "sha256-NNGXfUV5RVt1VqLI99NlHoBkt2Vv/Hg3TAHzm8nGM8M="
+    "version": "8.0.19",
+    "hash": "sha256-QySX2bih1UvwmLcn9cy1j+RuvZZwbcFKggL5Y/WcTnw="
   },
   {
     "pname": "Microsoft.AspNetCore.App.Runtime.linux-arm64",
-    "version": "8.0.17",
-    "hash": "sha256-Eunz3nZF5r8a9nqwdeorQPgqd5G+Z4ddofMeAk6VmnA="
+    "version": "8.0.19",
+    "hash": "sha256-69S+Ywyc5U8PDsVkkCVvZdHOgWb6ZZ3+f4UA0MLOLFI="
   },
   {
     "pname": "Microsoft.AspNetCore.App.Runtime.linux-x64",
-    "version": "8.0.17",
-    "hash": "sha256-SWdah72tC5i2CQL4mRUYfHC0Kh8+C2jiskIIeC74smY="
+    "version": "8.0.19",
+    "hash": "sha256-u50rdLuoADSDCthx2Fg+AnT192TalHhFrzFCfMgmTn4="
   },
   {
     "pname": "Microsoft.AspNetCore.App.Runtime.osx-arm64",
-    "version": "8.0.17",
-    "hash": "sha256-y55EGfQ2FzrY2X5+Ne5N3dqi5WNHkFTGVW1hEMrh6OI="
+    "version": "8.0.19",
+    "hash": "sha256-QAKu2xD4UQ4+gX79ynNQ0aA07D+EW6Ke0jRiTZne8CY="
   },
   {
     "pname": "Microsoft.AspNetCore.App.Runtime.osx-x64",
-    "version": "8.0.17",
-    "hash": "sha256-uRCCNPevPemvKIuUxy/VtQlgskChbiAauMWVK/xhoc0="
+    "version": "8.0.19",
+    "hash": "sha256-v5lzESMpodrH2grgk8ojA6BLDUfyxX5r6YY5Pgq61tA="
   },
   {
     "pname": "Microsoft.CodeAnalysis.Analyzers",
@@ -106,48 +106,48 @@
   },
   {
     "pname": "Microsoft.NETCore.App.Host.linux-arm64",
-    "version": "8.0.17",
-    "hash": "sha256-pzOqFCd+UrIXmWGDfds5GxkI+Asjx30yFtLIuHFu/h4="
+    "version": "8.0.19",
+    "hash": "sha256-R86Kqzi3FUuPZlgj3zNOObLAvXtnGrS2mxsBAxWIZrY="
   },
   {
     "pname": "Microsoft.NETCore.App.Host.linux-x64",
-    "version": "8.0.17",
-    "hash": "sha256-AGnEGHcO2hfvChG3xEGOTA6dX4MiYPB7FoBkmWz3dc8="
+    "version": "8.0.19",
+    "hash": "sha256-a9t/bX+WIKOu9q2R52b/hPGwOpkAgpYuP42SW2QXTak="
   },
   {
     "pname": "Microsoft.NETCore.App.Host.osx-arm64",
-    "version": "8.0.17",
-    "hash": "sha256-fpMzkOWaA3OFNtHsqOk9s9xKVrcrqOyKHxE7jk8hebg="
+    "version": "8.0.19",
+    "hash": "sha256-VaeGPR+6ApGNtQpEaky2rdUKd4X/Pp3xFGaSgUfGNiE="
   },
   {
     "pname": "Microsoft.NETCore.App.Host.osx-x64",
-    "version": "8.0.17",
-    "hash": "sha256-Hrn01x+S+gnGEEHhr6mN6bPyqVAhp5u3CqgWwQbh4To="
+    "version": "8.0.19",
+    "hash": "sha256-hw7WMpTq7o544uSNvWUCIr6IRt5xZOo+eERMnwAbYyk="
   },
   {
     "pname": "Microsoft.NETCore.App.Ref",
-    "version": "8.0.17",
-    "hash": "sha256-tKawpjkMjV0ysNIWWrgHTiLxncZJDRNiDkQBwl255l4="
+    "version": "8.0.19",
+    "hash": "sha256-4ymel0R1c0HrX0plAWubJPzev52y0Fsx1esyQ1R7bXc="
   },
   {
     "pname": "Microsoft.NETCore.App.Runtime.linux-arm64",
-    "version": "8.0.17",
-    "hash": "sha256-FutphE4bEjd8s6ZqpFXrD1zuCDkNCJ7Vnl0pBm86HBA="
+    "version": "8.0.19",
+    "hash": "sha256-hqhpd8yT8bv05DhFTuMhfsaSISpLs3t4oM+R/ZkJH80="
   },
   {
     "pname": "Microsoft.NETCore.App.Runtime.linux-x64",
-    "version": "8.0.17",
-    "hash": "sha256-6YVEXiJ3b2gZAYri8iSRBdi/J+0DEl7FcwBX6h1Unkg="
+    "version": "8.0.19",
+    "hash": "sha256-Ou51zUFTPESAAzP/z0+sLDAAXC54+oDlESBBT12M2lM="
   },
   {
     "pname": "Microsoft.NETCore.App.Runtime.osx-arm64",
-    "version": "8.0.17",
-    "hash": "sha256-J3dfDial8GHyKQMFuBNFtOMD/mOK58vjrK2ZtrYObZg="
+    "version": "8.0.19",
+    "hash": "sha256-IC/e8AmT9twcXwzFmXAelf4ctMbg4ancKPGrPLFMNn8="
   },
   {
     "pname": "Microsoft.NETCore.App.Runtime.osx-x64",
-    "version": "8.0.17",
-    "hash": "sha256-WnkJyhSBHMw/VtLHWy0AFwzzkbIC1YQugFuj3Adg+Ks="
+    "version": "8.0.19",
+    "hash": "sha256-Rb0z0PT/FHyk/Fgjj9W3WDpkDMKJoXR9DgHB1cJeZSA="
   },
   {
     "pname": "Microsoft.NETCore.Platforms",
@@ -171,33 +171,38 @@
   },
   {
     "pname": "Microsoft.Testing.Extensions.Telemetry",
-    "version": "1.5.3",
-    "hash": "sha256-bIXwPSa3jkr2b6xINOqMUs6/uj/r4oVFM7xq3uVIZDU="
+    "version": "1.7.3",
+    "hash": "sha256-Z6WsY2FCUbNnT5HJd7IOrfOvqknVXp6PWzTVeb0idVg="
   },
   {
     "pname": "Microsoft.Testing.Extensions.TrxReport.Abstractions",
-    "version": "1.5.3",
-    "hash": "sha256-IfMRfcyaIKEMRtx326ICKtinDBEfGw/Sv8ZHawJ96Yc="
+    "version": "1.7.3",
+    "hash": "sha256-PTee04FHyTHx/gF5NLckXuVje807G51MzkPrZ1gkgCw="
   },
   {
     "pname": "Microsoft.Testing.Extensions.VSTestBridge",
-    "version": "1.5.3",
-    "hash": "sha256-XpM/yFjhLSsuzyDV+xKubs4V1zVVYiV05E0+N4S1h0g="
+    "version": "1.7.3",
+    "hash": "sha256-8d+wZmucfSO7PsviHjVxYB4q6NcjgxvnCUpLePq35sM="
   },
   {
     "pname": "Microsoft.Testing.Platform",
-    "version": "1.5.3",
-    "hash": "sha256-y61Iih6w5D79dmrj2V675mcaeIiHoj1HSa1FRit2BLM="
+    "version": "1.7.3",
+    "hash": "sha256-cavX11P5o9rooqC3ZHw5h002OKRg2ZNR/VaRwpNTQYA="
   },
   {
     "pname": "Microsoft.Testing.Platform.MSBuild",
-    "version": "1.5.3",
-    "hash": "sha256-YspvjE5Jfi587TAfsvfDVJXNrFOkx1B3y1CKV6m7YLY="
+    "version": "1.7.3",
+    "hash": "sha256-cREl529UQ/c5atT8KimMgrgNdy6MrAd0sBGT8sXRRPM="
+  },
+  {
+    "pname": "Microsoft.TestPlatform.AdapterUtilities",
+    "version": "17.13.0",
+    "hash": "sha256-Vr+3Tad/h/nk7f/5HMExn3HvCGFCarehFAzJSfCBaOc="
   },
   {
     "pname": "Microsoft.TestPlatform.ObjectModel",
-    "version": "17.12.0",
-    "hash": "sha256-3XBHBSuCxggAIlHXmKNQNlPqMqwFlM952Av6RrLw1/w="
+    "version": "17.13.0",
+    "hash": "sha256-6S0fjfj8vA+h6dJVNwLi6oZhYDO/I/6hBZaq2VTW+Uk="
   },
   {
     "pname": "Microsoft.TestPlatform.ObjectModel",
@@ -231,13 +236,13 @@
   },
   {
     "pname": "NUnit",
-    "version": "4.3.2",
-    "hash": "sha256-0RWe8uFoxYp6qhPlDDEghOMcKJgyw2ybvEoAqBLebeE="
+    "version": "4.4.0",
+    "hash": "sha256-5geF5QOF+X/WkuCEgkPVKH4AdKx4U0olpU07S8+G3nU="
   },
   {
     "pname": "NUnit3TestAdapter",
-    "version": "5.0.0",
-    "hash": "sha256-7jZM4qAbIzne3AcdFfMbvbgogqpxvVe6q2S7Ls8xQy0="
+    "version": "5.1.0",
+    "hash": "sha256-5z470sFjV67wGHaw8KfmSloIAYe81Dokp0f8I6zXsDc="
   },
   {
     "pname": "runtime.any.System.Runtime",