Concrete types - lots of tech debt in here (#79)

CLAUDE.md

@@ -100,3 +100,77 @@ It strongly prefers to avoid special-casing to get around problems, but instead
 ### Common Gotchas
 
 * I've named several types in such a way as to overlap with built-in types, e.g. MethodInfo is in both WoofWare.PawPrint and System.Reflection.Metadata namespaces. Build errors can usually be fixed by fully-qualifying the type.
+
+## Type Concretization System
+
+### Overview
+
+Type concretization converts abstract type definitions (`TypeDefn`) to concrete runtime types (`ConcreteTypeHandle`). This is essential because IL operations need exact types at runtime, including all generic instantiations. The system separates type concretization from IL execution, ensuring types are properly loaded before use.
+
+### Key Concepts
+
+#### Generic Parameters
+- **Common error**: "Generic type/method parameter X out of range" probably means you're missing the proper generic context: some caller has passed the wrong list of generics through somewhere.
+
+#### Assembly Context
+TypeRefs must be resolved in the context of the assembly where they're defined, not where they're used. When resolving a TypeRef, always use the assembly that contains the TypeRef in its metadata.
+
+### Common Scenarios and Solutions
+
+#### Nested Generic Contexts
+When inside `Array.Empty<T>()` calling `AsRef<T>`, the `T` refers to the outer method's generic parameter. Pass the current executing method's generics as context:
+```fsharp
+let currentMethod = state.ThreadState.[thread].MethodState.ExecutingMethod
+concretizeMethodWithTypeGenerics ... currentMethod.Generics state
+```
+
+#### Field Access in Generic Contexts
+When accessing `EmptyArray<T>.Value` from within `Array.Empty<T>()`, use both type and method generics:
+```fsharp
+let contextTypeGenerics = currentMethod.DeclaringType.Generics
+let contextMethodGenerics = currentMethod.Generics
+```
+
+#### Call vs CallMethod
+- `callMethodInActiveAssembly` expects unconcretized methods and does concretization internally
+- `callMethod` expects already-concretized methods
+- The refactoring changed to concretizing before calling to ensure types are loaded
+
+### Common Pitfalls
+
+1. **Don't create new generic parameters when they already exist**. It's *very rarely* correct to instantiate `TypeDefn.Generic{Type,Method}Parameter` yourself:
+   ```fsharp
+   // Wrong: field.DeclaringType.Generics |> List.mapi (fun i _ -> TypeDefn.GenericTypeParameter i)
+   // Right: field.DeclaringType.Generics
+   ```
+
+2. **Assembly loading context**: The `loadAssembly` function expects the assembly that contains the reference as the first parameter, not the target assembly
+
+3. **Type forwarding**: Use `Assembly.resolveTypeRef` which handles type forwarding and exported types correctly
+
+### Key Files for Type System
+
+- **TypeConcretisation.fs**: Core type concretization logic
+  - `concretizeType`: Main entry point
+  - `concretizeGenericInstantiation`: Handles generic instantiations like `List<T>`
+  - `ConcretizationContext`: Tracks state during concretization
+
+- **IlMachineState.fs**:
+  - `concretizeMethodForExecution`: Prepares methods for execution
+  - `concretizeFieldForExecution`: Prepares fields for access
+  - Manages the flow of generic contexts through execution
+
+- **Assembly.fs**:
+  - `resolveTypeRef`: Resolves type references across assemblies
+  - `resolveTypeFromName`: Handles type forwarding and exported types
+  - `resolveTypeFromExport`: Follows type forwarding chains
+
+### Debugging Type Concretization Issues
+
+When encountering errors:
+1. Check the generic context (method name, generic parameters)
+2. Verify the assembly context being used
+3. Identify the TypeDefn variant being concretized
+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

WoofWare.PawPrint.Domain/Assembly.fs

@@ -429,12 +429,20 @@ module Assembly =
         (assemblies : ImmutableDictionary<string, DumpedAssembly>)
         (referencedInAssembly : DumpedAssembly)
         (target : TypeRef)
-        (genericArgs : ImmutableArray<TypeDefn> option)
+        (genericArgs : ImmutableArray<TypeDefn>)
         : TypeResolutionResult
         =
         match target.ResolutionScope with
         | TypeRefResolutionScope.Assembly r ->
-            let assemblyRef = referencedInAssembly.AssemblyReferences.[r]
+            match referencedInAssembly.AssemblyReferences.TryGetValue r with
+            | false, _ ->
+                failwithf
+                    "AssemblyReferenceHandle %A not found in assembly %s. Available references: %A"
+                    r
+                    referencedInAssembly.Name.FullName
+                    (referencedInAssembly.AssemblyReferences.Keys |> Seq.toList)
+            | true, assemblyRef ->
+
             let assemblyName = assemblyRef.Name
 
             match assemblies.TryGetValue assemblyName.FullName with
@@ -459,13 +467,7 @@ module Assembly =
 
                 match targetType with
                 | [ t ] ->
-                let t =
+                    let t = t |> TypeInfo.mapGeneric (fun _ param -> genericArgs.[param.SequenceNumber])
-                    t
-                    |> TypeInfo.mapGeneric (fun _ param ->
-                        match genericArgs with
-                        | None -> failwith "got a generic TypeRef but no generic args in context"
-                        | Some genericArgs -> genericArgs.[param.SequenceNumber]
-                    )
 
                     TypeResolutionResult.Resolved (assy, t)
                 | _ :: _ :: _ -> failwith $"Multiple matching type definitions! {nsPath} {target.Name}"
@@ -480,7 +482,7 @@ module Assembly =
         (assemblies : ImmutableDictionary<string, DumpedAssembly>)
         (ns : string option)
         (name : string)
-        (genericArgs : ImmutableArray<TypeDefn> option)
+        (genericArgs : ImmutableArray<TypeDefn>)
         : TypeResolutionResult
         =
         match ns with
@@ -491,11 +493,7 @@ module Assembly =
         | Some typeDef ->
             let typeDef =
                 typeDef
-                |> TypeInfo.mapGeneric (fun _ param ->
+                |> TypeInfo.mapGeneric (fun _ param -> genericArgs.[param.SequenceNumber])
-                    match genericArgs with
-                    | None -> failwith<TypeDefn> $"tried to resolve generic type {ns}.{name} but no generics in scope"
-                    | Some genericArgs -> genericArgs.[param.SequenceNumber]
-                )
 
             TypeResolutionResult.Resolved (assy, typeDef)
         | None ->
@@ -512,7 +510,7 @@ module Assembly =
         (fromAssembly : DumpedAssembly)
         (assemblies : ImmutableDictionary<string, DumpedAssembly>)
         (ty : WoofWare.PawPrint.ExportedType)
-        (genericArgs : ImmutableArray<TypeDefn> option)
+        (genericArgs : ImmutableArray<TypeDefn>)
         : TypeResolutionResult
         =
         match ty.Data with
@@ -538,7 +536,7 @@ module DumpedAssembly =
             | Some (BaseTypeInfo.TypeRef r) ->
                 let assy = loadedAssemblies.[source.FullName]
                 // TODO: generics
-                match Assembly.resolveTypeRef loadedAssemblies assy assy.TypeRefs.[r] None with
+                match Assembly.resolveTypeRef loadedAssemblies assy assy.TypeRefs.[r] ImmutableArray.Empty with
                 | TypeResolutionResult.FirstLoadAssy _ ->
                     failwith
                         "seems pretty unlikely that we could have constructed this object without loading its base type"

WoofWare.PawPrint.Domain/ConcreteType.fs

@@ -75,8 +75,6 @@ type ConcreteType<'typeGeneric when 'typeGeneric : comparison and 'typeGeneric :
                 (this :> IComparable<ConcreteType<'typeGeneric>>).CompareTo other
             | _ -> failwith "bad comparison"
 
-type RuntimeConcreteType = ConcreteType<TypeDefn>
-
 [<RequireQualifiedAccess>]
 module ConcreteType =
     let make
@@ -85,7 +83,7 @@ module ConcreteType =
         (name : string)
         (defn : TypeDefinitionHandle)
         (generics : TypeDefn list)
-        : RuntimeConcreteType
+        : ConcreteType<TypeDefn>
         =
         {
             _AssemblyName = assemblyName

WoofWare.PawPrint.Domain/TypeConcretisation.fs

@@ -0,0 +1,900 @@
+namespace WoofWare.PawPrint
+
+open System.Collections.Immutable
+open System.Reflection
+open System.Reflection.Metadata
+
+type ConcreteTypeHandle =
+    | Concrete of int
+    | Byref of ConcreteTypeHandle
+    | Pointer of ConcreteTypeHandle
+
+type AllConcreteTypes =
+    {
+        Mapping : Map<int, ConcreteType<ConcreteTypeHandle>>
+        NextHandle : int
+    }
+
+    static member Empty =
+        {
+            Mapping = Map.empty
+            NextHandle = 0
+        }
+
+[<RequireQualifiedAccess>]
+module AllConcreteTypes =
+    let lookup (cth : ConcreteTypeHandle) (this : AllConcreteTypes) : ConcreteType<ConcreteTypeHandle> option =
+        match cth with
+        | ConcreteTypeHandle.Concrete id -> this.Mapping |> Map.tryFind id
+        | ConcreteTypeHandle.Byref _ -> None // Byref types are not stored in the mapping
+        | ConcreteTypeHandle.Pointer _ -> None // Pointer types are not stored in the mapping
+
+    let lookup' (ct : ConcreteType<ConcreteTypeHandle>) (this : AllConcreteTypes) : ConcreteTypeHandle option =
+        this.Mapping
+        |> Map.tryPick (fun id existingCt ->
+            if
+                existingCt._AssemblyName = ct._AssemblyName
+                && existingCt._Namespace = ct._Namespace
+                && existingCt._Name = ct._Name
+                && existingCt._Definition = ct._Definition
+                && existingCt._Generics = ct._Generics
+            then
+                Some (ConcreteTypeHandle.Concrete id)
+            else
+                None
+        )
+
+    let findExistingConcreteType
+        (concreteTypes : AllConcreteTypes)
+        (asm : AssemblyName, ns : string, name : string, generics : ConcreteTypeHandle list as key)
+        : ConcreteTypeHandle option
+        =
+        concreteTypes.Mapping
+        |> Map.tryPick (fun id ct ->
+            if
+                ct.Assembly.FullName = asm.FullName
+                && ct.Namespace = ns
+                && ct.Name = name
+                && ct.Generics = generics
+            then
+                Some (ConcreteTypeHandle.Concrete id)
+            else
+                None
+        )
+
+    /// `source` is AssemblyName * Namespace * Name
+    let add (ct : ConcreteType<ConcreteTypeHandle>) (this : AllConcreteTypes) : ConcreteTypeHandle * AllConcreteTypes =
+        let id = this.NextHandle
+        let toRet = ConcreteTypeHandle.Concrete id
+
+        let newState =
+            {
+                NextHandle = this.NextHandle + 1
+                Mapping = this.Mapping |> Map.add id ct
+            }
+
+        toRet, newState
+
+[<RequireQualifiedAccess>]
+module TypeConcretization =
+
+    type ConcretizationContext =
+        {
+            /// Types currently being processed (to detect cycles)
+            InProgress : ImmutableDictionary<AssemblyName * TypeDefn, ConcreteTypeHandle>
+            /// All concrete types created so far
+            ConcreteTypes : AllConcreteTypes
+            /// For resolving type references
+            LoadedAssemblies : ImmutableDictionary<string, DumpedAssembly>
+            BaseTypes : BaseClassTypes<DumpedAssembly>
+        }
+
+    // Helper function to find existing types by assembly, namespace, name, and generics
+    let private findExistingType
+        (concreteTypes : AllConcreteTypes)
+        (assembly : AssemblyName)
+        (ns : string)
+        (name : string)
+        (generics : ConcreteTypeHandle list)
+        : ConcreteTypeHandle option
+        =
+        concreteTypes.Mapping
+        |> Map.tryPick (fun id ct ->
+            if
+                ct.Assembly.FullName = assembly.FullName
+                && ct.Namespace = ns
+                && ct.Name = name
+                && ct.Generics = generics
+            then
+                Some (ConcreteTypeHandle.Concrete id)
+            else
+                None
+        )
+
+    // Helper function for primitive types (convenience wrapper)
+    let private findExistingPrimitiveType
+        (concreteTypes : AllConcreteTypes)
+        (key : AssemblyName * string * string)
+        : ConcreteTypeHandle option
+        =
+        let (asm, ns, name) = key
+        findExistingType concreteTypes asm ns name []
+
+    // Helper function to create and add a ConcreteType to the context
+    let private createAndAddConcreteType
+        (ctx : ConcretizationContext)
+        (assembly : AssemblyName)
+        (definition : ComparableTypeDefinitionHandle)
+        (ns : string)
+        (name : string)
+        (generics : ConcreteTypeHandle list)
+        : ConcreteTypeHandle * ConcretizationContext
+        =
+        let concreteType =
+            {
+                _AssemblyName = assembly
+                _Definition = definition
+                _Namespace = ns
+                _Name = name
+                _Generics = generics
+            }
+
+        let handle, newConcreteTypes = AllConcreteTypes.add concreteType ctx.ConcreteTypes
+
+        let newCtx =
+            { ctx with
+                ConcreteTypes = newConcreteTypes
+            }
+
+        handle, newCtx
+
+    // Helper function for assembly loading with retry pattern
+    let private loadAssemblyAndResolveTypeRef
+        (loadAssembly :
+            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
+        (ctx : ConcretizationContext)
+        (currentAssembly : AssemblyName)
+        (typeRef : TypeRef)
+        : (DumpedAssembly * WoofWare.PawPrint.TypeInfo<_, _>) * ConcretizationContext
+        =
+        let currentAssy =
+            match ctx.LoadedAssemblies.TryGetValue currentAssembly.FullName with
+            | false, _ -> failwithf "Current assembly %s not loaded" currentAssembly.FullName
+            | true, assy -> assy
+
+        // First try to resolve without loading new assemblies
+        let resolutionResult =
+            Assembly.resolveTypeRef ctx.LoadedAssemblies currentAssy typeRef ImmutableArray.Empty
+
+        match resolutionResult with
+        | TypeResolutionResult.Resolved (targetAssy, typeInfo) -> (targetAssy, typeInfo), ctx
+        | TypeResolutionResult.FirstLoadAssy assemblyRef ->
+            // Need to load the assembly
+            match typeRef.ResolutionScope with
+            | TypeRefResolutionScope.Assembly assyRef ->
+                let newAssemblies, loadedAssy = loadAssembly currentAssembly assyRef
+
+                let newCtx =
+                    { ctx with
+                        LoadedAssemblies = newAssemblies
+                    }
+
+                // Now try to resolve again with the loaded assembly
+                let resolutionResult2 =
+                    Assembly.resolveTypeRef newCtx.LoadedAssemblies currentAssy typeRef ImmutableArray.Empty
+
+                match resolutionResult2 with
+                | TypeResolutionResult.Resolved (targetAssy, typeInfo) -> (targetAssy, typeInfo), newCtx
+                | TypeResolutionResult.FirstLoadAssy _ ->
+                    failwithf "Failed to resolve type %s.%s after loading assembly" typeRef.Namespace typeRef.Name
+            | _ -> failwith "Unexpected resolution scope"
+
+    let private concretizePrimitive
+        (ctx : ConcretizationContext)
+        (prim : PrimitiveType)
+        : ConcreteTypeHandle * ConcretizationContext
+        =
+
+        // Get the TypeInfo for this primitive from BaseClassTypes
+        let typeInfo =
+            match prim with
+            | PrimitiveType.Boolean -> ctx.BaseTypes.Boolean
+            | PrimitiveType.Char -> ctx.BaseTypes.Char
+            | PrimitiveType.SByte -> ctx.BaseTypes.SByte
+            | PrimitiveType.Byte -> ctx.BaseTypes.Byte
+            | PrimitiveType.Int16 -> ctx.BaseTypes.Int16
+            | PrimitiveType.UInt16 -> ctx.BaseTypes.UInt16
+            | PrimitiveType.Int32 -> ctx.BaseTypes.Int32
+            | PrimitiveType.UInt32 -> ctx.BaseTypes.UInt32
+            | PrimitiveType.Int64 -> ctx.BaseTypes.Int64
+            | PrimitiveType.UInt64 -> ctx.BaseTypes.UInt64
+            | PrimitiveType.Single -> ctx.BaseTypes.Single
+            | PrimitiveType.Double -> ctx.BaseTypes.Double
+            | PrimitiveType.String -> ctx.BaseTypes.String
+            | PrimitiveType.Object -> ctx.BaseTypes.Object
+            | PrimitiveType.TypedReference -> ctx.BaseTypes.TypedReference
+            | PrimitiveType.IntPtr -> ctx.BaseTypes.IntPtr
+            | PrimitiveType.UIntPtr -> ctx.BaseTypes.UIntPtr
+
+        // Check if we've already concretized this primitive type
+        let key = (typeInfo.Assembly, typeInfo.Namespace, typeInfo.Name)
+
+        match findExistingPrimitiveType ctx.ConcreteTypes key with
+        | Some handle -> handle, ctx
+        | None ->
+            // Create and add the concrete type (primitives have no generic arguments)
+            createAndAddConcreteType
+                ctx
+                typeInfo.Assembly
+                (ComparableTypeDefinitionHandle.Make typeInfo.TypeDefHandle)
+                typeInfo.Namespace
+                typeInfo.Name
+                [] // Primitives have no generic parameters
+
+    let private concretizeArray
+        (ctx : ConcretizationContext)
+        (elementHandle : ConcreteTypeHandle)
+        (shape : 'a)
+        : ConcreteTypeHandle * ConcretizationContext
+        =
+
+        // Arrays are System.Array<T> where T is the element type
+        let arrayTypeInfo = ctx.BaseTypes.Array
+
+        // Check if we've already concretized this array type
+        match
+            findExistingType
+                ctx.ConcreteTypes
+                arrayTypeInfo.Assembly
+                arrayTypeInfo.Namespace
+                arrayTypeInfo.Name
+                [ elementHandle ]
+        with
+        | Some handle -> handle, ctx
+        | None ->
+            // Create and add the concrete array type
+            createAndAddConcreteType
+                ctx
+                arrayTypeInfo.Assembly
+                (ComparableTypeDefinitionHandle.Make arrayTypeInfo.TypeDefHandle)
+                arrayTypeInfo.Namespace
+                arrayTypeInfo.Name
+                [ elementHandle ] // Array<T> has one generic parameter
+
+    let private concretizeOneDimArray
+        (ctx : ConcretizationContext)
+        (elementHandle : ConcreteTypeHandle)
+        : ConcreteTypeHandle * ConcretizationContext
+        =
+
+        // One-dimensional arrays with lower bound 0 are also System.Array<T>
+        // They just have different IL instructions for access
+        let arrayTypeInfo = ctx.BaseTypes.Array
+
+        // Check if we've already concretized this array type
+        match
+            findExistingType
+                ctx.ConcreteTypes
+                arrayTypeInfo.Assembly
+                arrayTypeInfo.Namespace
+                arrayTypeInfo.Name
+                [ elementHandle ]
+        with
+        | Some handle -> handle, ctx
+        | None ->
+            // Create and add the concrete array type
+            createAndAddConcreteType
+                ctx
+                arrayTypeInfo.Assembly
+                (ComparableTypeDefinitionHandle.Make arrayTypeInfo.TypeDefHandle)
+                arrayTypeInfo.Namespace
+                arrayTypeInfo.Name
+                [ elementHandle ] // Array<T> has one generic parameter
+
+    let concretizeTypeDefinition
+        (ctx : ConcretizationContext)
+        (assemblyName : AssemblyName)
+        (typeDefHandle : ComparableTypeDefinitionHandle)
+        : ConcreteTypeHandle * ConcretizationContext
+        =
+
+        // Look up the type definition in the assembly
+        let assembly =
+            match ctx.LoadedAssemblies.TryGetValue assemblyName.FullName with
+            | false, _ -> failwithf "Cannot concretize type definition - assembly %s not loaded" assemblyName.FullName
+            | true, assy -> assy
+
+        let typeInfo = assembly.TypeDefs.[typeDefHandle.Get]
+
+        // Check if this type has generic parameters
+        if not typeInfo.Generics.IsEmpty then
+            failwithf
+                "Cannot concretize open generic type %s.%s - it has %d generic parameters"
+                typeInfo.Namespace
+                typeInfo.Name
+                typeInfo.Generics.Length
+
+        // Check if we've already concretized this type
+        match findExistingType ctx.ConcreteTypes assemblyName typeInfo.Namespace typeInfo.Name [] 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
+
+    let private concretizeTypeReference
+        (loadAssembly :
+            AssemblyName -> AssemblyReferenceHandle -> ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly)
+        (ctx : ConcretizationContext)
+        (currentAssembly : AssemblyName)
+        (typeRef : TypeRef)
+        : ConcreteTypeHandle * ConcretizationContext
+        =
+        // Use the helper to load assembly and resolve the type reference
+        let (targetAssy, typeInfo), ctx =
+            loadAssemblyAndResolveTypeRef loadAssembly ctx currentAssembly typeRef
+
+        // Check if this type has generic parameters
+        if not typeInfo.Generics.IsEmpty then
+            failwithf
+                "Cannot concretize type reference to open generic type %s.%s - it has %d generic parameters"
+                typeInfo.Namespace
+                typeInfo.Name
+                typeInfo.Generics.Length
+
+        // Create or find the concrete type
+        concretizeTypeDefinition ctx targetAssy.Name (ComparableTypeDefinitionHandle.Make typeInfo.TypeDefHandle)
+
+    /// Concretize a type in a specific generic context
+    let rec concretizeType
+        (ctx : ConcretizationContext)
+        (loadAssembly :
+            AssemblyName -> AssemblyReferenceHandle -> (ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly))
+        (assembly : AssemblyName)
+        (typeGenerics : ConcreteTypeHandle ImmutableArray)
+        (methodGenerics : ConcreteTypeHandle ImmutableArray)
+        (typeDefn : TypeDefn)
+        : ConcreteTypeHandle * ConcretizationContext
+        =
+
+        let key = (assembly, typeDefn)
+
+        // Check if we're already processing this type (cycle detection)
+        match ctx.InProgress.TryGetValue key with
+        | true, handle -> handle, ctx
+        | false, _ ->
+
+        match typeDefn with
+        | TypeDefn.PrimitiveType prim -> concretizePrimitive ctx prim
+
+        | TypeDefn.Array (elementType, shape) ->
+            let elementHandle, ctx =
+                concretizeType ctx loadAssembly assembly typeGenerics methodGenerics elementType
+
+            concretizeArray ctx elementHandle shape
+
+        | TypeDefn.OneDimensionalArrayLowerBoundZero elementType ->
+            let elementHandle, ctx =
+                concretizeType ctx loadAssembly assembly typeGenerics methodGenerics elementType
+
+            concretizeOneDimArray ctx elementHandle
+
+        | TypeDefn.GenericTypeParameter index ->
+            if index < typeGenerics.Length then
+                typeGenerics.[index], ctx
+            else
+                failwithf "Generic type parameter %d out of range" index
+
+        | TypeDefn.GenericMethodParameter index ->
+            if index < methodGenerics.Length then
+                methodGenerics.[index], ctx
+            else
+                failwithf "Generic method parameter %d out of range" index
+
+        | TypeDefn.GenericInstantiation (genericDef, args) ->
+            concretizeGenericInstantiation ctx loadAssembly assembly typeGenerics methodGenerics genericDef args
+
+        | TypeDefn.FromDefinition (typeDefHandle, targetAssembly, _) ->
+            concretizeTypeDefinition ctx (AssemblyName targetAssembly) typeDefHandle
+
+        | TypeDefn.FromReference (typeRef, _) -> concretizeTypeReference loadAssembly ctx assembly typeRef
+
+        | TypeDefn.Byref elementType ->
+            // Byref types are managed references to other types
+            // First concretize the element type
+            let elementHandle, ctx =
+                concretizeType ctx loadAssembly assembly typeGenerics methodGenerics elementType
+
+            // Return a Byref constructor wrapping the element type
+            ConcreteTypeHandle.Byref elementHandle, ctx
+
+        | TypeDefn.Pointer elementType ->
+            // Pointer types are unmanaged pointers to other types
+            // First concretize the element type
+            let elementHandle, ctx =
+                concretizeType ctx loadAssembly assembly typeGenerics methodGenerics elementType
+
+            // Return a Pointer constructor wrapping the element type
+            ConcreteTypeHandle.Pointer elementHandle, ctx
+
+        | TypeDefn.Void ->
+            // Void isn't a real runtime type, but we assign it a concretization entry anyway
+            // Use System.Void from the base class types
+            let voidTypeInfo = ctx.BaseTypes.Void
+
+            match
+                findExistingType ctx.ConcreteTypes voidTypeInfo.Assembly voidTypeInfo.Namespace voidTypeInfo.Name []
+            with
+            | Some handle -> handle, ctx
+            | None ->
+                // Create and add the concrete Void type
+                createAndAddConcreteType
+                    ctx
+                    voidTypeInfo.Assembly
+                    (ComparableTypeDefinitionHandle.Make voidTypeInfo.TypeDefHandle)
+                    voidTypeInfo.Namespace
+                    voidTypeInfo.Name
+                    [] // Void has no generic parameters
+
+        | _ -> failwithf "TODO: Concretization of %A not implemented" typeDefn
+
+    and private concretizeGenericInstantiation
+        (ctx : ConcretizationContext)
+        (loadAssembly :
+            AssemblyName -> AssemblyReferenceHandle -> (ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly))
+        (assembly : AssemblyName)
+        (typeGenerics : ConcreteTypeHandle ImmutableArray)
+        (methodGenerics : ConcreteTypeHandle ImmutableArray)
+        (genericDef : TypeDefn)
+        (args : ImmutableArray<TypeDefn>)
+        : ConcreteTypeHandle * ConcretizationContext
+        =
+        // First, concretize all type arguments
+        let argHandles, ctxAfterArgs =
+            args
+            |> Seq.fold
+                (fun (handles, ctx) arg ->
+                    let handle, ctx =
+                        concretizeType ctx loadAssembly assembly typeGenerics methodGenerics arg
+
+                    handle :: handles, ctx
+                )
+                ([], ctx)
+
+        let argHandles = argHandles |> List.rev
+
+        // Get the base type definition
+        let baseAssembly, baseTypeDefHandle, baseNamespace, baseName, ctxAfterArgs =
+            match genericDef with
+            | FromDefinition (handle, assy, _) ->
+                // Look up the type definition to get namespace and name
+                let currentAssy = ctxAfterArgs.LoadedAssemblies.[AssemblyName(assy).FullName]
+                let typeDef = currentAssy.TypeDefs.[handle.Get]
+                AssemblyName assy, handle, typeDef.Namespace, typeDef.Name, ctxAfterArgs
+            | FromReference (typeRef, _) ->
+                // For a type reference, we need to find where the type is defined
+                // We're looking for the generic type definition, not an instantiation
+                let currentAssy = ctxAfterArgs.LoadedAssemblies.[assembly.FullName]
+
+                // Helper to find the type definition without instantiating generics
+                let rec findTypeDefinition (assy : DumpedAssembly) (ns : string) (name : string) =
+                    // First check if it's defined in this assembly
+                    match assy.TypeDef ns name with
+                    | Some typeDef -> Some (assy, typeDef)
+                    | None ->
+                        // Check if it's exported/forwarded
+                        match assy.ExportedType (Some ns) name with
+                        | Some export ->
+                            match export.Data with
+                            | NonForwarded _ -> None // Shouldn't happen
+                            | ForwardsTo assyRef ->
+                                let forwardedAssy = assy.AssemblyReferences.[assyRef]
+
+                                match ctxAfterArgs.LoadedAssemblies.TryGetValue forwardedAssy.Name.FullName with
+                                | true, targetAssy -> findTypeDefinition targetAssy ns name
+                                | false, _ -> None // Assembly not loaded yet
+                        | None -> None
+
+                // First try to resolve without loading new assemblies
+                match typeRef.ResolutionScope with
+                | TypeRefResolutionScope.Assembly assyRef ->
+                    let targetAssyRef = currentAssy.AssemblyReferences.[assyRef]
+                    let targetAssyName = targetAssyRef.Name
+
+                    match ctxAfterArgs.LoadedAssemblies.TryGetValue targetAssyName.FullName with
+                    | true, targetAssy ->
+                        // Try to find the type
+                        match findTypeDefinition targetAssy typeRef.Namespace typeRef.Name with
+                        | Some (foundAssy, typeDef) ->
+                            foundAssy.Name,
+                            ComparableTypeDefinitionHandle.Make typeDef.TypeDefHandle,
+                            typeDef.Namespace,
+                            typeDef.Name,
+                            ctxAfterArgs
+                        | None ->
+                            failwithf
+                                "Type %s.%s not found in assembly %s or its forwards"
+                                typeRef.Namespace
+                                typeRef.Name
+                                targetAssyName.FullName
+
+                    | false, _ ->
+                        // Need to load the assembly
+                        let newAssemblies, loadedAssy = loadAssembly assembly assyRef
+
+                        let ctxWithNewAssy =
+                            { ctxAfterArgs with
+                                LoadedAssemblies = newAssemblies
+                            }
+
+                        // Now try to find the type in the loaded assembly
+                        match findTypeDefinition loadedAssy typeRef.Namespace typeRef.Name with
+                        | Some (foundAssy, typeDef) ->
+                            foundAssy.Name,
+                            ComparableTypeDefinitionHandle.Make typeDef.TypeDefHandle,
+                            typeDef.Namespace,
+                            typeDef.Name,
+                            ctxWithNewAssy
+                        | None ->
+                            failwithf
+                                "Type %s.%s not found in loaded assembly %s or its forwards"
+                                typeRef.Namespace
+                                typeRef.Name
+                                loadedAssy.Name.FullName
+
+                | _ -> failwith "TODO: handle other resolution scopes for type refs in generic instantiation"
+            | _ -> failwithf "Generic instantiation of %A not supported" genericDef
+
+        // Check if this exact generic instantiation already exists
+        match findExistingType ctxAfterArgs.ConcreteTypes baseAssembly baseNamespace baseName argHandles with
+        | Some existingHandle ->
+            // Type already exists, return it
+            existingHandle, ctxAfterArgs
+        | None ->
+            // Need to handle cycles: check if we're already processing this type
+            let typeDefnKey = (assembly, GenericInstantiation (genericDef, args))
+
+            match ctxAfterArgs.InProgress.TryGetValue typeDefnKey with
+            | true, handle ->
+                // We're in a cycle, return the in-progress handle
+                handle, ctxAfterArgs
+            | false, _ ->
+                // Pre-allocate a handle for this type to handle cycles
+                let tempId = ctxAfterArgs.ConcreteTypes.NextHandle
+                let tempHandle = ConcreteTypeHandle.Concrete tempId
+
+                // Create the concrete type
+                let concreteType =
+                    {
+                        _AssemblyName = baseAssembly
+                        _Definition = baseTypeDefHandle
+                        _Namespace = baseNamespace
+                        _Name = baseName
+                        _Generics = argHandles
+                    }
+
+                // Add to the concrete types and mark as in progress
+                let newCtx =
+                    { ctxAfterArgs with
+                        ConcreteTypes =
+                            { ctxAfterArgs.ConcreteTypes with
+                                NextHandle = ctxAfterArgs.ConcreteTypes.NextHandle + 1
+                                Mapping = ctxAfterArgs.ConcreteTypes.Mapping |> Map.add tempId concreteType
+                            }
+                        InProgress = ctxAfterArgs.InProgress.SetItem (typeDefnKey, tempHandle)
+                    }
+
+                // Remove from in-progress when done
+                let finalCtx =
+                    { newCtx with
+                        InProgress = newCtx.InProgress.Remove typeDefnKey
+                    }
+
+                tempHandle, finalCtx
+
+/// High-level API for concretizing types
+[<RequireQualifiedAccess>]
+module Concretization =
+
+    /// Helper to concretize an array of types
+    let private concretizeTypeArray
+        (ctx : TypeConcretization.ConcretizationContext)
+        (loadAssembly :
+            AssemblyName -> AssemblyReferenceHandle -> (ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly))
+        (assembly : AssemblyName)
+        (typeArgs : ConcreteTypeHandle ImmutableArray)
+        (methodArgs : ConcreteTypeHandle ImmutableArray)
+        (types : ImmutableArray<TypeDefn>)
+        : ImmutableArray<ConcreteTypeHandle> * TypeConcretization.ConcretizationContext
+        =
+
+        let handles = ImmutableArray.CreateBuilder (types.Length)
+        let mutable ctx = ctx
+
+        for i = 0 to types.Length - 1 do
+            let handle, newCtx =
+                TypeConcretization.concretizeType ctx loadAssembly assembly typeArgs methodArgs types.[i]
+
+            handles.Add handle
+            ctx <- newCtx
+
+        handles.ToImmutable (), ctx
+
+    /// Helper to concretize a method signature
+    let private concretizeMethodSignature
+        (ctx : TypeConcretization.ConcretizationContext)
+        (loadAssembly :
+            AssemblyName -> AssemblyReferenceHandle -> (ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly))
+        (assembly : AssemblyName)
+        (typeArgs : ConcreteTypeHandle ImmutableArray)
+        (methodArgs : ConcreteTypeHandle ImmutableArray)
+        (signature : TypeMethodSignature<TypeDefn>)
+        : TypeMethodSignature<ConcreteTypeHandle> * TypeConcretization.ConcretizationContext
+        =
+
+        // Concretize return type
+        let returnHandle, ctx =
+            TypeConcretization.concretizeType ctx loadAssembly assembly typeArgs methodArgs signature.ReturnType
+
+        // Concretize parameter types
+        let paramHandles = ResizeArray<ConcreteTypeHandle> ()
+        let mutable ctx = ctx
+
+        for paramType in signature.ParameterTypes do
+            let handle, newCtx =
+                TypeConcretization.concretizeType ctx loadAssembly assembly typeArgs methodArgs paramType
+
+            paramHandles.Add (handle)
+            ctx <- newCtx
+
+        let newSignature =
+            {
+                Header = signature.Header
+                ReturnType = returnHandle
+                ParameterTypes = paramHandles |> Seq.toList
+                GenericParameterCount = signature.GenericParameterCount
+                RequiredParameterCount = signature.RequiredParameterCount
+            }
+
+        newSignature, ctx
+
+    /// Helper to ensure base type assembly is loaded
+    let rec private ensureBaseTypeAssembliesLoaded
+        (loadAssembly :
+            AssemblyName -> AssemblyReferenceHandle -> (ImmutableDictionary<string, DumpedAssembly> * DumpedAssembly))
+        (assemblies : ImmutableDictionary<string, DumpedAssembly>)
+        (assyName : AssemblyName)
+        (baseTypeInfo : BaseTypeInfo option)
+        : ImmutableDictionary<string, DumpedAssembly>
+        =
+        match baseTypeInfo with
+        | None -> assemblies
+        | Some (BaseTypeInfo.TypeRef r) ->
+            let assy = assemblies.[assyName.FullName]
+            let typeRef = assy.TypeRefs.[r]
+
+            match typeRef.ResolutionScope with
+            | TypeRefResolutionScope.Assembly assyRef ->
+                let targetAssyRef = assy.AssemblyReferences.[assyRef]
+
+                match assemblies.TryGetValue targetAssyRef.Name.FullName with
+                | true, _ -> assemblies
+                | false, _ ->
+                    // Need to load the assembly - pass the assembly that contains the reference
+                    let newAssemblies, _ = loadAssembly assy.Name assyRef
+                    newAssemblies
+            | _ -> assemblies
+        | Some (BaseTypeInfo.TypeDef _)
+        | Some (BaseTypeInfo.ForeignAssemblyType _)
+        | Some (BaseTypeInfo.TypeSpec _) -> assemblies
+
+    /// Concretize a method's signature and body
+    let concretizeMethod
+        (ctx : AllConcreteTypes)
+        (loadAssembly :
+            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)
+        : WoofWare.PawPrint.MethodInfo<ConcreteTypeHandle, ConcreteTypeHandle, ConcreteTypeHandle> *
+          AllConcreteTypes *
+          ImmutableDictionary<string, DumpedAssembly>
+        =
+
+        // Ensure base type assemblies are loaded for the declaring type
+        let assemblies =
+            let assy = assemblies.[method.DeclaringType._AssemblyName.FullName]
+            let typeDef = assy.TypeDefs.[method.DeclaringType._Definition.Get]
+            ensureBaseTypeAssembliesLoaded loadAssembly assemblies assy.Name typeDef.BaseType
+
+        let concCtx =
+            {
+                TypeConcretization.ConcretizationContext.InProgress = ImmutableDictionary.Empty
+                TypeConcretization.ConcretizationContext.ConcreteTypes = ctx
+                TypeConcretization.ConcretizationContext.LoadedAssemblies = assemblies
+                TypeConcretization.ConcretizationContext.BaseTypes = baseTypes
+            }
+
+        // First, we need to create a TypeDefn for the declaring type with its generics instantiated
+        let declaringTypeDefn =
+            if method.DeclaringType._Generics.IsEmpty then
+                // Non-generic type - determine the SignatureTypeKind
+                let assy = concCtx.LoadedAssemblies.[method.DeclaringType._AssemblyName.FullName]
+                let arg = assy.TypeDefs.[method.DeclaringType._Definition.Get]
+
+                let baseType =
+                    arg.BaseType
+                    |> DumpedAssembly.resolveBaseType baseTypes concCtx.LoadedAssemblies assy.Name
+
+                let signatureTypeKind =
+                    match baseType with
+                    | ResolvedBaseType.Enum
+                    | ResolvedBaseType.ValueType -> SignatureTypeKind.ValueType
+                    | ResolvedBaseType.Object
+                    | ResolvedBaseType.Delegate -> SignatureTypeKind.Class
+
+                TypeDefn.FromDefinition (
+                    method.DeclaringType._Definition,
+                    method.DeclaringType._AssemblyName.FullName,
+                    signatureTypeKind
+                )
+            else
+                // Generic type - create a GenericInstantiation
+                let assy = concCtx.LoadedAssemblies.[method.DeclaringType._AssemblyName.FullName]
+                let arg = assy.TypeDefs.[method.DeclaringType._Definition.Get]
+
+                let baseTypeResolved =
+                    arg.BaseType
+                    |> DumpedAssembly.resolveBaseType baseTypes concCtx.LoadedAssemblies assy.Name
+
+                let signatureTypeKind =
+                    match baseTypeResolved with
+                    | ResolvedBaseType.Enum
+                    | ResolvedBaseType.ValueType -> SignatureTypeKind.ValueType
+                    | ResolvedBaseType.Object
+                    | ResolvedBaseType.Delegate -> SignatureTypeKind.Class
+
+                let baseType =
+                    TypeDefn.FromDefinition (
+                        method.DeclaringType._Definition,
+                        method.DeclaringType._AssemblyName.FullName,
+                        signatureTypeKind
+                    )
+
+                let genericArgsLength = method.DeclaringType.Generics.Length
+
+                if genericArgsLength > typeArgs.Length then
+                    failwithf
+                        "Method declaring type expects %d generic arguments but only %d provided"
+                        genericArgsLength
+                        typeArgs.Length
+
+                let genericArgs =
+                    typeArgs.Slice (0, genericArgsLength)
+                    |> Seq.mapi (fun i _ -> TypeDefn.GenericTypeParameter i)
+                    |> ImmutableArray.CreateRange
+
+                TypeDefn.GenericInstantiation (baseType, genericArgs)
+
+        // Concretize the declaring type
+        let declaringHandle, concCtx =
+            TypeConcretization.concretizeType
+                concCtx
+                loadAssembly
+                method.DeclaringType._AssemblyName
+                typeArgs
+                methodArgs
+                declaringTypeDefn
+
+        // Look up the concretized declaring type
+        let concretizedDeclaringType =
+            AllConcreteTypes.lookup declaringHandle concCtx.ConcreteTypes |> Option.get
+
+        // Concretize signature
+        let signature, concCtx =
+            concretizeMethodSignature
+                concCtx
+                loadAssembly
+                method.DeclaringType._AssemblyName
+                typeArgs
+                methodArgs
+                method.Signature
+
+        // Concretize local variables
+        let instructions, concCtx2 =
+            match method.Instructions with
+            | None -> None, concCtx
+            | Some instr ->
+                let locals, updatedCtx =
+                    match instr.LocalVars with
+                    | None -> None, concCtx
+                    | Some vars ->
+                        let handles, ctx =
+                            concretizeTypeArray
+                                concCtx
+                                loadAssembly
+                                method.DeclaringType._AssemblyName
+                                typeArgs
+                                methodArgs
+                                vars
+
+                        Some handles, ctx
+
+                Some (MethodInstructions.setLocalVars locals instr), updatedCtx
+
+        // Map generics to handles
+        let genericHandles =
+            method.Generics
+            |> Seq.mapi (fun i _ -> methodArgs.[i])
+            |> ImmutableArray.CreateRange
+
+        let concretizedMethod : MethodInfo<_, _, ConcreteTypeHandle> =
+            {
+                DeclaringType = concretizedDeclaringType
+                Handle = method.Handle
+                Name = method.Name
+                Instructions = instructions
+                Parameters = method.Parameters
+                Generics = genericHandles
+                Signature = signature
+                RawSignature = method.RawSignature
+                CustomAttributes = method.CustomAttributes
+                MethodAttributes = method.MethodAttributes
+                ImplAttributes = method.ImplAttributes
+                IsStatic = method.IsStatic
+            }
+
+        concretizedMethod, concCtx2.ConcreteTypes, concCtx2.LoadedAssemblies
+
+    let rec concreteHandleToTypeDefn
+        (baseClassTypes : BaseClassTypes<DumpedAssembly>)
+        (handle : ConcreteTypeHandle)
+        (concreteTypes : AllConcreteTypes)
+        (assemblies : ImmutableDictionary<string, DumpedAssembly>)
+        : TypeDefn
+        =
+        match handle with
+        | ConcreteTypeHandle.Byref elementHandle ->
+            let elementType =
+                concreteHandleToTypeDefn baseClassTypes elementHandle concreteTypes assemblies
+
+            TypeDefn.Byref elementType
+        | ConcreteTypeHandle.Pointer elementHandle ->
+            let elementType =
+                concreteHandleToTypeDefn baseClassTypes elementHandle concreteTypes assemblies
+
+            TypeDefn.Pointer elementType
+        | ConcreteTypeHandle.Concrete _ ->
+            match AllConcreteTypes.lookup handle concreteTypes with
+            | None -> failwith "Logic error: handle not found"
+            | Some concreteType ->
+
+            // Determine SignatureTypeKind
+            let assy = assemblies.[concreteType.Assembly.FullName]
+            let typeDef = assy.TypeDefs.[concreteType.Definition.Get]
+            // Determine SignatureTypeKind from base type
+            let baseType =
+                typeDef.BaseType
+                |> DumpedAssembly.resolveBaseType baseClassTypes assemblies assy.Name
+
+            let signatureTypeKind =
+                match baseType with
+                | ResolvedBaseType.Enum
+                | ResolvedBaseType.ValueType -> SignatureTypeKind.ValueType
+                | ResolvedBaseType.Object
+                | ResolvedBaseType.Delegate -> SignatureTypeKind.Class
+
+            if concreteType.Generics.IsEmpty then
+                TypeDefn.FromDefinition (concreteType.Definition, concreteType.Assembly.FullName, signatureTypeKind)
+            else
+                // Recursively convert generic arguments
+                let genericArgs =
+                    concreteType.Generics
+                    |> List.map (fun h -> concreteHandleToTypeDefn baseClassTypes h concreteTypes assemblies)
+                    |> ImmutableArray.CreateRange
+
+                let baseDef =
+                    TypeDefn.FromDefinition (concreteType.Definition, concreteType.Assembly.FullName, signatureTypeKind)
+
+                TypeDefn.GenericInstantiation (baseDef, genericArgs)

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

@@ -26,6 +26,7 @@
         <Compile Include="ExportedType.fs" />
         <Compile Include="TypeSpec.fs" />
         <Compile Include="Assembly.fs" />
+        <Compile Include="TypeConcretisation.fs" />
     </ItemGroup>
 
     <ItemGroup>

WoofWare.PawPrint.Test/TestPureCases.fs

@@ -16,6 +16,18 @@ module TestPureCases =
 
     let unimplemented =
         [
+            {
+                FileName = "CrossAssemblyTypes.cs"
+                ExpectedReturnCode = 0
+                NativeImpls = MockEnv.make ()
+                LocalVariablesOfMain = None
+            }
+            {
+                FileName = "GenericEdgeCases.cs"
+                ExpectedReturnCode = 0
+                NativeImpls = MockEnv.make ()
+                LocalVariablesOfMain = None
+            }
             {
                 FileName = "TestShl.cs"
                 ExpectedReturnCode = 0
@@ -80,6 +92,12 @@ module TestPureCases =
                 NativeImpls = MockEnv.make ()
                 LocalVariablesOfMain = [ CliType.Numeric (CliNumericType.Int32 1) ] |> Some
             }
+            {
+                FileName = "StaticVariables.cs"
+                ExpectedReturnCode = 0
+                NativeImpls = MockEnv.make ()
+                LocalVariablesOfMain = None
+            }
             {
                 FileName = "Ldind.cs"
                 ExpectedReturnCode = 0
@@ -200,6 +218,12 @@ module TestPureCases =
                 NativeImpls = MockEnv.make ()
                 LocalVariablesOfMain = None
             }
+            {
+                FileName = "TypeConcretization.cs"
+                ExpectedReturnCode = 0
+                NativeImpls = MockEnv.make ()
+                LocalVariablesOfMain = None
+            }
             {
                 FileName = "TestOr.cs"
                 ExpectedReturnCode = 0

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

@@ -22,6 +22,7 @@
     <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" />
@@ -36,6 +37,9 @@
     <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" />

WoofWare.PawPrint.Test/sourcesPure/CrossAssemblyTypes.cs

@@ -0,0 +1,120 @@
+using System;
+using System.Collections.Generic;
+using System.Collections;
+
+// Test cross-assembly type resolution using standard library types
+public class CrossAssemblyTypeTest
+{
+    public static int TestSystemTypes()
+    {
+        // Test various System types to ensure proper assembly resolution
+        
+        // System.DateTime
+        var date = new DateTime(2023, 1, 1);
+        if (date.Year != 2023) return 1;
+        
+        // System.Guid
+        var guid = Guid.Empty;
+        if (guid != Guid.Empty) return 2;
+        
+        // System.TimeSpan
+        var timeSpan = TimeSpan.FromMinutes(30);
+        if (timeSpan.TotalMinutes != 30) return 3;
+        
+        return 0;
+    }
+    
+    public static int TestCollectionTypes()
+    {
+        // Test various collection types from different assemblies
+        
+        // Dictionary<TKey, TValue>
+        var dict = new Dictionary<string, int>();
+        dict["test"] = 42;
+        if (dict["test"] != 42) return 1;
+        
+        // HashSet<T>
+        var hashSet = new HashSet<int>();
+        hashSet.Add(1);
+        hashSet.Add(2);
+        hashSet.Add(1); // duplicate
+        if (hashSet.Count != 2) return 2;
+        
+        // Queue<T>
+        var queue = new Queue<string>();
+        queue.Enqueue("first");
+        queue.Enqueue("second");
+        if (queue.Dequeue() != "first") return 3;
+        
+        return 0;
+    }
+    
+    public static int TestGenericInterfaces()
+    {
+        // Test generic interfaces across assemblies
+        
+        var list = new List<int> { 1, 2, 3 };
+        
+        // IEnumerable<T>
+        IEnumerable<int> enumerable = list;
+        int count = 0;
+        foreach (int item in enumerable)
+        {
+            count++;
+        }
+        if (count != 3) return 1;
+        
+        // ICollection<T>
+        ICollection<int> collection = list;
+        if (collection.Count != 3) return 2;
+        
+        // IList<T>
+        IList<int> ilist = list;
+        if (ilist[0] != 1) return 3;
+        
+        return 0;
+    }
+}
+
+// Test Array.Empty<T> which was mentioned in the diff as a specific case
+public class ArrayEmptyTest
+{
+    public static int TestArrayEmpty()
+    {
+        // Test Array.Empty<T> for different types
+        var emptyInts = Array.Empty<int>();
+        var emptyStrings = Array.Empty<string>();
+        
+        if (emptyInts.Length != 0) return 1;
+        if (emptyStrings.Length != 0) return 2;
+        
+        // Verify they are different instances for different types
+        // but same instance for same type
+        var emptyInts2 = Array.Empty<int>();
+        if (!ReferenceEquals(emptyInts, emptyInts2)) return 3;
+        
+        return 0;
+    }
+}
+
+class Program
+{
+    static int Main(string[] args)
+    {
+        int result;
+        
+        result = CrossAssemblyTypeTest.TestSystemTypes();
+        if (result != 0) return 100 + result;
+        
+        result = CrossAssemblyTypeTest.TestCollectionTypes();
+        if (result != 0) return 200 + result;
+        
+        result = CrossAssemblyTypeTest.TestGenericInterfaces();
+        if (result != 0) return 300 + result;
+        
+        result = ArrayEmptyTest.TestArrayEmpty();
+        if (result != 0) return 400 + result;
+        
+        return 0; // All tests passed
+    }
+}

WoofWare.PawPrint.Test/sourcesPure/GenericEdgeCases.cs

@@ -0,0 +1,142 @@
+using System;
+using System.Collections.Generic;
+
+// Test edge cases with generic parameters as mentioned in the diff
+public class GenericParameterEdgeCases
+{
+    // Test method with multiple generic parameters
+    public static T2 Convert<T1, T2>(T1 input, Func<T1, T2> converter)
+    {
+        return converter(input);
+    }
+    
+    // Test nested generic method calls
+    public static List<T> WrapInList<T>(T item)
+    {
+        var list = new List<T>();
+        list.Add(item);
+        return list;
+    }
+    
+    public static int TestMultipleGenericParameters()
+    {
+        // Test Convert method with different type combinations
+        string result1 = Convert<int, string>(42, x => x.ToString());
+        if (result1 != "42") return 1;
+        
+        int result2 = Convert<string, int>("123", x => int.Parse(x));
+        if (result2 != 123) return 2;
+        
+        return 0;
+    }
+    
+    public static int TestNestedGenericMethodCalls()
+    {
+        // Test calling generic method from within another generic method
+        var intList = WrapInList<int>(42);
+        if (intList.Count != 1) return 1;
+        if (intList[0] != 42) return 2;
+        
+        var stringList = WrapInList<string>("test");
+        if (stringList.Count != 1) return 3;
+        if (stringList[0] != "test") return 4;
+        
+        return 0;
+    }
+}
+
+// Test deeply nested generic types
+public class DeepNestingTest
+{
+    public static int TestDeeplyNestedGenerics()
+    {
+        // Test Dictionary<string, List<Dictionary<int, string>>>
+        var complexType = new Dictionary<string, List<Dictionary<int, string>>>();
+        
+        var innerDict = new Dictionary<int, string>();
+        innerDict[1] = "one";
+        innerDict[2] = "two";
+        
+        var listOfDicts = new List<Dictionary<int, string>>();
+        listOfDicts.Add(innerDict);
+        
+        complexType["test"] = listOfDicts;
+        
+        if (complexType["test"].Count != 1) return 1;
+        if (complexType["test"][0][1] != "one") return 2;
+        if (complexType["test"][0][2] != "two") return 3;
+        
+        return 0;
+    }
+}
+
+// Test generic constraints and inheritance scenarios
+public class GenericConstraintTest<T> where T : class
+{
+    private T value;
+    
+    public GenericConstraintTest(T val)
+    {
+        value = val;
+    }
+    
+    public bool IsNull()
+    {
+        return value == null;
+    }
+    
+    public static int TestGenericConstraints()
+    {
+        var test = new GenericConstraintTest<string>("hello");
+        if (test.IsNull()) return 1;
+        
+        var nullTest = new GenericConstraintTest<string>(null);
+        if (!nullTest.IsNull()) return 2;
+        
+        return 0;
+    }
+}
+
+// Test generic field access scenarios mentioned in the diff
+public class GenericFieldAccess<T>
+{
+    public static T DefaultValue = default(T);
+    
+    public static int TestStaticGenericField()
+    {
+        // Test that static fields work correctly with generics
+        if (GenericFieldAccess<int>.DefaultValue != 0) return 1;
+        
+        // Test that different instantiations have different static fields
+        GenericFieldAccess<int>.DefaultValue = 42;
+        if (GenericFieldAccess<int>.DefaultValue != 42) return 2;
+        if (GenericFieldAccess<string>.DefaultValue != null) return 3;
+        
+        return 0;
+    }
+}
+
+class Program
+{
+    static int Main(string[] args)
+    {
+        int result;
+        
+        result = GenericParameterEdgeCases.TestMultipleGenericParameters();
+        if (result != 0) return 100 + result;
+        
+        result = GenericParameterEdgeCases.TestNestedGenericMethodCalls();
+        if (result != 0) return 200 + result;
+        
+        result = DeepNestingTest.TestDeeplyNestedGenerics();
+        if (result != 0) return 300 + result;
+        
+        result = GenericConstraintTest<string>.TestGenericConstraints();
+        if (result != 0) return 400 + result;
+        
+        result = GenericFieldAccess<int>.TestStaticGenericField();
+        if (result != 0) return 500 + result;
+        
+        return 0; // All tests passed
+    }
+}

WoofWare.PawPrint.Test/sourcesPure/StaticVariables.cs

@@ -0,0 +1,54 @@
+public class GenericCounter<T>
+{
+    private static int count = 0;
+
+    public static void Increment()
+    {
+        count++;
+    }
+
+    public static int GetCount()
+    {
+        return count;
+    }
+
+    public static void Reset()
+    {
+        count = 0;
+    }
+}
+
+class Program
+{
+    static int Main(string[] argv)
+    {
+        // Test that different generic instantiations have separate static variables
+
+        // Initial state should be 0 for all
+        if (GenericCounter<int>.GetCount() != 0) return 1;
+        if (GenericCounter<string>.GetCount() != 0) return 2;
+
+        // Increment int version 3 times
+        GenericCounter<int>.Increment();
+        GenericCounter<int>.Increment();
+        GenericCounter<int>.Increment();
+
+        // Increment string version 2 times
+        GenericCounter<string>.Increment();
+        GenericCounter<string>.Increment();
+
+        // Verify counts are independent
+        if (GenericCounter<int>.GetCount() != 3) return 3;
+        if (GenericCounter<string>.GetCount() != 2) return 4;
+
+        // Reset int version only
+        GenericCounter<int>.Reset();
+
+        // Verify reset only affected int version
+        if (GenericCounter<int>.GetCount() != 0) return 5;
+        if (GenericCounter<string>.GetCount() != 2) return 6;
+
+        // Test passes - static variables are isolated per generic instantiation
+        return 0;
+    }
+}

WoofWare.PawPrint.Test/sourcesPure/TypeConcretization.cs

@@ -0,0 +1,112 @@
+using System;
+using System.Collections.Generic;
+
+// Test basic type concretization
+public class BasicTypeTest
+{
+    public static int TestBasicTypes()
+    {
+        // Test primitive types
+        int i = 42;
+        string s = "hello";
+        bool b = true;
+        
+        if (i != 42) return 1;
+        if (s != "hello") return 2;
+        if (!b) return 3;
+        
+        return 0;
+    }
+}
+
+// Test generic type instantiation
+public class GenericTypeTest<T>
+{
+    private T value;
+    
+    public GenericTypeTest(T val)
+    {
+        value = val;
+    }
+    
+    public T GetValue()
+    {
+        return value;
+    }
+    
+    public static int TestGenericInstantiation()
+    {
+        var intTest = new GenericTypeTest<int>(123);
+        var stringTest = new GenericTypeTest<string>("test");
+        
+        if (intTest.GetValue() != 123) return 1;
+        if (stringTest.GetValue() != "test") return 2;
+        
+        return 0;
+    }
+}
+
+// Test nested generic types
+public class NestedGenericTest
+{
+    public static int TestNestedGenerics()
+    {
+        var listOfInts = new List<int>();
+        listOfInts.Add(1);
+        listOfInts.Add(2);
+        
+        if (listOfInts.Count != 2) return 1;
+        if (listOfInts[0] != 1) return 2;
+        if (listOfInts[1] != 2) return 3;
+        
+        var listOfLists = new List<List<int>>();
+        listOfLists.Add(listOfInts);
+        
+        if (listOfLists.Count != 1) return 4;
+        if (listOfLists[0].Count != 2) return 5;
+        
+        return 0;
+    }
+}
+
+// Test generic methods
+public class GenericMethodTest
+{
+    public static T Identity<T>(T input)
+    {
+        return input;
+    }
+    
+    public static int TestGenericMethods()
+    {
+        int intResult = Identity<int>(42);
+        string stringResult = Identity<string>("hello");
+        
+        if (intResult != 42) return 1;
+        if (stringResult != "hello") return 2;
+        
+        return 0;
+    }
+}
+
+class Program
+{
+    static int Main(string[] args)
+    {
+        int result;
+        
+        result = BasicTypeTest.TestBasicTypes();
+        if (result != 0) return 100 + result;
+        
+        result = GenericTypeTest<int>.TestGenericInstantiation();
+        if (result != 0) return 200 + result;
+        
+        result = NestedGenericTest.TestNestedGenerics();
+        if (result != 0) return 300 + result;
+        
+        result = GenericMethodTest.TestGenericMethods();
+        if (result != 0) return 400 + result;
+        
+        return 0; // All tests passed
+    }
+}

WoofWare.PawPrint/AbstractMachine.fs

@@ -60,22 +60,18 @@ module AbstractMachine =
 
                     let delegateToRun = state.ManagedHeap.NonArrayObjects.[delegateToRunAddr]
 
-                    if delegateToRun.Fields.["_target"] <> CliType.ObjectRef None then
+                    let target =
-                        failwith "TODO: delegate target wasn't None"
+                        match delegateToRun.Fields.["_target"] with
+                        | CliType.ObjectRef addr -> addr
+                        | x -> failwith $"TODO: delegate target wasn't an object ref: %O{x}"
 
                     let methodPtr =
                         match delegateToRun.Fields.["_methodPtr"] with
                         | CliType.Numeric (CliNumericType.NativeInt (NativeIntSource.FunctionPointer mi)) -> mi
                         | d -> failwith $"unexpectedly not a method pointer in delegate invocation: {d}"
 
-                    let typeGenerics =
-                        instruction.ExecutingMethod.DeclaringType.Generics |> ImmutableArray.CreateRange
-
                     let methodGenerics = instruction.ExecutingMethod.Generics
 
-                    let methodPtr =
-                        methodPtr |> MethodInfo.mapTypeGenerics (fun i _ -> typeGenerics.[i])
-
                     // When we return, we need to go back up the stack
                     match state |> IlMachineState.returnStackFrame loggerFactory baseClassTypes thread with
                     | None -> failwith "unexpectedly nowhere to return from delegate"
@@ -86,23 +82,41 @@ module AbstractMachine =
                         (state, instruction.Arguments)
                         ||> Seq.fold (fun state arg -> IlMachineState.pushToEvalStack arg thread state)
 
+                    // The odd little calling convention strikes again: we push the `target` parameter on top of the
+                    // stack, although that doesn't actually happen in the CLR.
+                    // We'll pretend we're constructing an object, so that the calling convention gets respected in
+                    // `callMethod`.
+                    let state, constructing =
+                        match target with
+                        | None -> state, None
+                        | Some target ->
+                            let state =
+                                IlMachineState.pushToEvalStack (CliType.ObjectRef (Some target)) thread state
+
+                            state, Some target
+
                     let state, _ =
                         state.WithThreadSwitchedToAssembly methodPtr.DeclaringType.Assembly thread
 
                     // Don't advance the program counter again on return; that was already done by the Callvirt that
                     // caused this delegate to be invoked.
-                    let state, result =
+                    let currentThreadState = state.ThreadState.[thread]
-                        state
+
-                        |> IlMachineState.callMethodInActiveAssembly
+                    let state =
+                        IlMachineState.callMethod
                             loggerFactory
                             baseClassTypes
-                            thread
-                            false
-                            (Some methodGenerics)
-                            methodPtr
                             None
+                            constructing
+                            false
+                            false
+                            methodGenerics
+                            methodPtr
+                            thread
+                            currentThreadState
+                            state
 
-                    ExecutionResult.Stepped (state, result)
+                    ExecutionResult.Stepped (state, WhatWeDid.Executed)
             | _ ->
 
             let outcome =
@@ -111,8 +125,8 @@ module AbstractMachine =
                     targetType.Namespace,
                     targetType.Name,
                     instruction.ExecutingMethod.Name,
-                    instruction.ExecutingMethod.Signature.ParameterTypes,
+                    instruction.ExecutingMethod.RawSignature.ParameterTypes,
-                    instruction.ExecutingMethod.Signature.ReturnType
+                    instruction.ExecutingMethod.RawSignature.ReturnType
                 with
                 | "System.Private.CoreLib",
                   "System",

WoofWare.PawPrint/BasicCliType.fs

@@ -1,6 +1,5 @@
 namespace WoofWare.PawPrint
 
-open System
 open System.Collections.Immutable
 open System.Reflection
 open System.Reflection.Metadata
@@ -63,7 +62,7 @@ type UnsignedNativeIntSource =
 type NativeIntSource =
     | Verbatim of int64
     | ManagedPointer of ManagedPointerSource
-    | FunctionPointer of MethodInfo<FakeUnit, WoofWare.PawPrint.GenericParameter, TypeDefn>
+    | FunctionPointer of MethodInfo<ConcreteTypeHandle, ConcreteTypeHandle, ConcreteTypeHandle>
     | TypeHandlePtr of int64<typeHandle>
 
     override this.ToString () : string =
@@ -168,7 +167,6 @@ type CliTypeResolutionResult =
 
 [<RequireQualifiedAccess>]
 module CliType =
-
     let zeroOfPrimitive (primitiveType : PrimitiveType) : CliType =
         match primitiveType with
         | PrimitiveType.Boolean -> CliType.Bool 0uy
@@ -194,92 +192,208 @@ module CliType =
         | PrimitiveType.Object -> CliType.ObjectRef None
 
     let rec zeroOf
+        (concreteTypes : AllConcreteTypes)
         (assemblies : ImmutableDictionary<string, DumpedAssembly>)
         (corelib : BaseClassTypes<DumpedAssembly>)
-        (assy : DumpedAssembly)
+        (handle : ConcreteTypeHandle)
-        (typeGenerics : TypeDefn ImmutableArray option)
+        : CliType * AllConcreteTypes
-        (methodGenerics : TypeDefn ImmutableArray option)
-        (ty : TypeDefn)
-        : CliTypeResolutionResult
         =
-        match ty with
+        zeroOfWithVisited concreteTypes assemblies corelib handle Set.empty
-        | TypeDefn.PrimitiveType primitiveType -> CliTypeResolutionResult.Resolved (zeroOfPrimitive primitiveType)
-        | TypeDefn.Array _ -> CliType.ObjectRef None |> CliTypeResolutionResult.Resolved
-        | TypeDefn.Pinned typeDefn -> failwith "todo"
-        | TypeDefn.Pointer _ ->
-            CliType.RuntimePointer (CliRuntimePointer.Managed CliRuntimePointerSource.Null)
-            |> CliTypeResolutionResult.Resolved
-        | TypeDefn.Byref _ -> CliType.ObjectRef None |> CliTypeResolutionResult.Resolved
-        | TypeDefn.OneDimensionalArrayLowerBoundZero _ -> CliType.ObjectRef None |> CliTypeResolutionResult.Resolved
-        | TypeDefn.Modified (original, afterMod, modificationRequired) -> failwith "todo"
-        | TypeDefn.FromReference (typeRef, signatureTypeKind) ->
-            match signatureTypeKind with
-            | SignatureTypeKind.Unknown -> failwith "todo"
-            | SignatureTypeKind.ValueType ->
-                match Assembly.resolveTypeRef assemblies assy typeRef typeGenerics with
-                | TypeResolutionResult.Resolved (sourceAssy, ty) ->
-                    let fields =
-                        ty.Fields
-                        |> List.filter (fun field -> not (field.Attributes.HasFlag FieldAttributes.Static))
-                        |> List.map (fun fi ->
-                            match zeroOf assemblies corelib sourceAssy typeGenerics methodGenerics fi.Signature with
-                            | CliTypeResolutionResult.Resolved ty -> Ok (fi.Name, ty)
-                            | CliTypeResolutionResult.FirstLoad a -> Error a
-                        )
-                        |> Result.allOkOrError
 
-                    match fields with
+    and zeroOfWithVisited
-                    | Error (_, []) -> failwith "logic error"
+        (concreteTypes : AllConcreteTypes)
-                    | Error (_, f :: _) -> CliTypeResolutionResult.FirstLoad f
+        (assemblies : ImmutableDictionary<string, DumpedAssembly>)
-                    | Ok fields -> CliType.ValueType fields |> CliTypeResolutionResult.Resolved
+        (corelib : BaseClassTypes<DumpedAssembly>)
-                | TypeResolutionResult.FirstLoadAssy assy -> CliTypeResolutionResult.FirstLoad assy
+        (handle : ConcreteTypeHandle)
-            | SignatureTypeKind.Class -> CliType.ObjectRef None |> CliTypeResolutionResult.Resolved
+        (visited : Set<ConcreteTypeHandle>)
-            | _ -> raise (ArgumentOutOfRangeException ())
+        : CliType * AllConcreteTypes
-        | TypeDefn.FromDefinition (typeDefinitionHandle, _, signatureTypeKind) ->
+        =
-            let typeDef = assy.TypeDefs.[typeDefinitionHandle.Get]
 
-            if typeDef = corelib.Int32 then
+        // Handle constructed types first
-                zeroOfPrimitive PrimitiveType.Int32 |> CliTypeResolutionResult.Resolved
+        match handle with
-            elif typeDef = corelib.Int64 then
+        | ConcreteTypeHandle.Byref _ ->
-                zeroOfPrimitive PrimitiveType.Int64 |> CliTypeResolutionResult.Resolved
+            // Byref types are managed references - the zero value is a null reference
-            elif typeDef = corelib.UInt32 then
+            CliType.RuntimePointer (CliRuntimePointer.Managed CliRuntimePointerSource.Null), concreteTypes
-                zeroOfPrimitive PrimitiveType.UInt32 |> CliTypeResolutionResult.Resolved
+
-            elif typeDef = corelib.UInt64 then
+        | ConcreteTypeHandle.Pointer _ ->
-                zeroOfPrimitive PrimitiveType.UInt64 |> CliTypeResolutionResult.Resolved
+            // Pointer types are unmanaged pointers - the zero value is a null pointer
+            CliType.RuntimePointer (CliRuntimePointer.Unmanaged 0L), concreteTypes
+
+        | ConcreteTypeHandle.Concrete _ ->
+            // This is a concrete type - look it up in the mapping
+            let concreteType =
+                match AllConcreteTypes.lookup handle concreteTypes with
+                | Some ct -> ct
+                | None -> failwithf "ConcreteTypeHandle %A not found in AllConcreteTypes" handle
+
+            // Get the type definition from the assembly
+            let assembly = assemblies.[concreteType.Assembly.FullName]
+            let typeDef = assembly.TypeDefs.[concreteType.Definition.Get]
+
+            // Check if it's a primitive type by comparing with corelib types FIRST
+            if concreteType.Assembly = corelib.Corelib.Name && concreteType.Generics.IsEmpty then
+                // Check against known primitive types
+                if TypeInfo.NominallyEqual typeDef corelib.Boolean then
+                    zeroOfPrimitive PrimitiveType.Boolean, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.Char then
+                    zeroOfPrimitive PrimitiveType.Char, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.SByte then
+                    zeroOfPrimitive PrimitiveType.SByte, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.Byte then
+                    zeroOfPrimitive PrimitiveType.Byte, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.Int16 then
+                    zeroOfPrimitive PrimitiveType.Int16, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.UInt16 then
+                    zeroOfPrimitive PrimitiveType.UInt16, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.Int32 then
+                    zeroOfPrimitive PrimitiveType.Int32, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.UInt32 then
+                    zeroOfPrimitive PrimitiveType.UInt32, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.Int64 then
+                    zeroOfPrimitive PrimitiveType.Int64, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.UInt64 then
+                    zeroOfPrimitive PrimitiveType.UInt64, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.Single then
+                    zeroOfPrimitive PrimitiveType.Single, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.Double then
+                    zeroOfPrimitive PrimitiveType.Double, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.String then
+                    zeroOfPrimitive PrimitiveType.String, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.Object then
+                    zeroOfPrimitive PrimitiveType.Object, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.IntPtr then
+                    zeroOfPrimitive PrimitiveType.IntPtr, concreteTypes
+                elif TypeInfo.NominallyEqual typeDef corelib.UIntPtr then
+                    zeroOfPrimitive PrimitiveType.UIntPtr, concreteTypes
+                else if
+                    // Check if it's an array type
+                    typeDef = corelib.Array
+                then
+                    CliType.ObjectRef None, concreteTypes // Arrays are reference types
+                else if
+                    // Not a known primitive, now check for cycles
+                    Set.contains handle visited
+                then
+                    // We're in a cycle - return a default zero value for the type
+                    // For value types in cycles, we'll return a null reference as a safe fallback
+                    // This should only happen with self-referential types
+                    CliType.ObjectRef None, concreteTypes
                 else
-            // TODO: the rest
+                    let visited = Set.add handle visited
-            match signatureTypeKind with
+                    // Not a known primitive, check if it's a value type or reference type
-            | SignatureTypeKind.Unknown -> failwith "todo"
+                    determineZeroForCustomType concreteTypes assemblies corelib handle concreteType typeDef visited
-            | SignatureTypeKind.ValueType ->
+            else if
-                let fields =
+                // Not from corelib or has generics
+                concreteType.Assembly = corelib.Corelib.Name
+                && typeDef = corelib.Array
+                && concreteType.Generics.Length = 1
+            then
+                // This is an array type
+                CliType.ObjectRef None, concreteTypes
+            else if
+                // Custom type - now check for cycles
+                Set.contains handle visited
+            then
+                // We're in a cycle - return a default zero value for the type
+                // For value types in cycles, we'll return a null reference as a safe fallback
+                // This should only happen with self-referential types
+                CliType.ObjectRef None, concreteTypes
+            else
+                let visited = Set.add handle visited
+                // Custom type - need to determine if it's a value type or reference type
+                determineZeroForCustomType concreteTypes assemblies corelib handle concreteType typeDef visited
+
+    and private determineZeroForCustomType
+        (concreteTypes : AllConcreteTypes)
+        (assemblies : ImmutableDictionary<string, DumpedAssembly>)
+        (corelib : BaseClassTypes<DumpedAssembly>)
+        (handle : ConcreteTypeHandle)
+        (concreteType : ConcreteType<ConcreteTypeHandle>)
+        (typeDef : WoofWare.PawPrint.TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>)
+        (visited : Set<ConcreteTypeHandle>)
+        : CliType * AllConcreteTypes
+        =
+
+        // Determine if this is a value type by checking inheritance
+        let isValueType =
+            match DumpedAssembly.resolveBaseType corelib assemblies typeDef.Assembly typeDef.BaseType with
+            | ResolvedBaseType.ValueType
+            | ResolvedBaseType.Enum -> true
+            | ResolvedBaseType.Delegate -> false // Delegates are reference types
+            | ResolvedBaseType.Object -> false
+
+        if isValueType then
+            // It's a value type - need to create zero values for all non-static fields
+            let mutable currentConcreteTypes = concreteTypes
+
+            let fieldZeros =
                 typeDef.Fields
-                    // oh lord, this is awfully ominous - I really don't want to store the statics here
                 |> List.filter (fun field -> not (field.Attributes.HasFlag FieldAttributes.Static))
-                    |> List.map (fun fi ->
+                |> List.map (fun field ->
-                        match zeroOf assemblies corelib assy typeGenerics methodGenerics fi.Signature with
+                    // Need to concretize the field type with the concrete type's generics
-                        | CliTypeResolutionResult.Resolved ty -> Ok (fi.Name, ty)
+                    let fieldTypeDefn = field.Signature
-                        | CliTypeResolutionResult.FirstLoad a -> Error a
+
+                    let fieldHandle, updatedConcreteTypes =
+                        concretizeFieldType currentConcreteTypes assemblies corelib concreteType fieldTypeDefn
+
+                    currentConcreteTypes <- updatedConcreteTypes
+
+                    let fieldZero, updatedConcreteTypes2 =
+                        zeroOfWithVisited currentConcreteTypes assemblies corelib fieldHandle visited
+
+                    currentConcreteTypes <- updatedConcreteTypes2
+                    (field.Name, fieldZero)
                 )
-                    |> Result.allOkOrError
 
-                match fields with
+            CliType.ValueType fieldZeros, currentConcreteTypes
-                | Error (_, []) -> failwith "logic error"
+        else
-                | Error (_, f :: _) -> CliTypeResolutionResult.FirstLoad f
+            // It's a reference type
-                | Ok fields ->
+            CliType.ObjectRef None, concreteTypes
 
-                CliType.ValueType fields |> CliTypeResolutionResult.Resolved
+    and private concretizeFieldType
-            | SignatureTypeKind.Class -> CliType.ObjectRef None |> CliTypeResolutionResult.Resolved
+        (concreteTypes : AllConcreteTypes)
-            | _ -> raise (ArgumentOutOfRangeException ())
+        (assemblies : ImmutableDictionary<string, DumpedAssembly>)
-        | TypeDefn.GenericInstantiation (generic, args) ->
+        (corelib : BaseClassTypes<DumpedAssembly>)
-            zeroOf assemblies corelib assy (Some args) methodGenerics generic
+        (declaringType : ConcreteType<ConcreteTypeHandle>)
-        | TypeDefn.FunctionPointer typeMethodSignature -> failwith "todo"
+        (fieldType : TypeDefn)
-        | TypeDefn.GenericTypeParameter index ->
+        : ConcreteTypeHandle * AllConcreteTypes
-            // TODO: can generics depend on other generics? presumably, so we pass the array down again
+        =
-            match typeGenerics with
+
-            | None -> failwith "asked for a type parameter of generic type, but no generics in scope"
+        // Create a concretization context
-            | Some generics -> zeroOf assemblies corelib assy (Some generics) methodGenerics generics.[index]
+        let ctx =
-        | TypeDefn.GenericMethodParameter index ->
+            {
-            match methodGenerics with
+                TypeConcretization.ConcretizationContext.InProgress = ImmutableDictionary.Empty
-            | None -> failwith "asked for a method parameter of generic type, but no generics in scope"
+                TypeConcretization.ConcretizationContext.ConcreteTypes = concreteTypes
-            | Some generics -> zeroOf assemblies corelib assy typeGenerics (Some generics) generics.[index]
+                TypeConcretization.ConcretizationContext.LoadedAssemblies = assemblies
-        | TypeDefn.Void -> failwith "should never construct an element of type Void"
+                TypeConcretization.ConcretizationContext.BaseTypes = corelib
+            }
+
+        // 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)
+            =
+            match assemblies.TryGetValue assyName.FullName with
+            | true, currentAssy ->
+                let targetAssyRef = currentAssy.AssemblyReferences.[ref]
+
+                match assemblies.TryGetValue targetAssyRef.Name.FullName with
+                | true, targetAssy -> assemblies, targetAssy
+                | false, _ ->
+                    failwithf "Assembly %s not loaded when trying to resolve reference" targetAssyRef.Name.FullName
+            | false, _ -> failwithf "Current assembly %s not loaded when trying to resolve reference" assyName.FullName
+
+        let handle, newCtx =
+            TypeConcretization.concretizeType
+                ctx
+                loadAssembly
+                declaringType.Assembly
+                typeGenerics
+                methodGenerics
+                fieldType
+
+        handle, newCtx.ConcreteTypes

WoofWare.PawPrint/MethodState.fs

@@ -6,7 +6,7 @@ type MethodReturnState =
     {
         /// Index in the MethodStates array of a ThreadState
         JumpTo : int
-        WasInitialisingType : RuntimeConcreteType option
+        WasInitialisingType : ConcreteTypeHandle option
         /// The Newobj instruction means we need to push a reference immediately after Ret.
         WasConstructingObj : ManagedHeapAddress option
     }
@@ -19,16 +19,16 @@ and MethodState =
         _IlOpIndex : int
         EvaluationStack : EvalStack
         Arguments : CliType ImmutableArray
-        ExecutingMethod : WoofWare.PawPrint.MethodInfo<TypeDefn, TypeDefn, TypeDefn>
+        ExecutingMethod : WoofWare.PawPrint.MethodInfo<ConcreteTypeHandle, ConcreteTypeHandle, ConcreteTypeHandle>
         /// We don't implement the local memory pool right now
         LocalMemoryPool : unit
         /// On return, we restore this state. This should be Some almost always; an exception is the entry point.
         ReturnState : MethodReturnState option
-        Generics : ImmutableArray<TypeDefn> option
+        Generics : ImmutableArray<ConcreteTypeHandle>
         /// Track which exception regions are currently active (innermost first)
         ActiveExceptionRegions : ExceptionRegion list
         /// When executing a finally/fault/filter, we need to know where to return
-        ExceptionContinuation : ExceptionContinuation<TypeDefn, TypeDefn, TypeDefn> option
+        ExceptionContinuation : ExceptionContinuation<ConcreteTypeHandle, ConcreteTypeHandle, ConcreteTypeHandle> option
     }
 
     member this.IlOpIndex = this._IlOpIndex
@@ -136,11 +136,12 @@ and MethodState =
     /// If `method` is an instance method, `args` must be of length 1+numParams.
     /// If `method` is static, `args` must be of length numParams.
     static member Empty
+        (concreteTypes : AllConcreteTypes)
         (corelib : BaseClassTypes<DumpedAssembly>)
         (loadedAssemblies : ImmutableDictionary<string, DumpedAssembly>)
         (containingAssembly : DumpedAssembly)
-        (method : WoofWare.PawPrint.MethodInfo<TypeDefn, TypeDefn, TypeDefn>)
+        (method : WoofWare.PawPrint.MethodInfo<ConcreteTypeHandle, ConcreteTypeHandle, ConcreteTypeHandle>)
-        (methodGenerics : ImmutableArray<TypeDefn> option)
+        (methodGenerics : ImmutableArray<ConcreteTypeHandle>)
         (args : ImmutableArray<CliType>)
         (returnState : MethodReturnState option)
         : Result<MethodState, WoofWare.PawPrint.AssemblyReference list>
@@ -164,28 +165,18 @@ and MethodState =
         // I think valid code should remain valid if we unconditionally localsInit - it should be undefined
         // to use an uninitialised value? Not checked this; TODO.
 
-        let requiredAssemblies = ResizeArray<WoofWare.PawPrint.AssemblyReference> ()
-
-        let typeGenerics =
-            match method.DeclaringType.Generics with
-            | [] -> None
-            | x -> ImmutableArray.CreateRange x |> Some
-
         let localVars =
             let result = ImmutableArray.CreateBuilder ()
 
             for var in localVariableSig do
-                match CliType.zeroOf loadedAssemblies corelib containingAssembly typeGenerics methodGenerics var with
+                // Note: This assumes all types have already been concretized
-                | CliTypeResolutionResult.Resolved t -> result.Add t
+                // If this fails with "ConcreteTypeHandle not found", it means
-                | CliTypeResolutionResult.FirstLoad (assy : WoofWare.PawPrint.AssemblyReference) ->
+                // we need to ensure types are concretized before creating the MethodState
-                    requiredAssemblies.Add assy
+                let zero, _ = CliType.zeroOf concreteTypes loadedAssemblies corelib var
+                result.Add zero
 
             result.ToImmutable ()
 
-        if requiredAssemblies.Count > 0 then
-            Error (requiredAssemblies |> Seq.toList)
-        else
-
         let activeRegions = ExceptionHandling.getActiveRegionsAtOffset 0 method
 
         {

WoofWare.PawPrint/Program.fs

@@ -17,11 +17,7 @@ module Program =
         let argsAllocations, state =
             (state, args)
             ||> Seq.mapFold (fun state arg ->
-                IlMachineState.allocateManagedObject
+                IlMachineState.allocateManagedObject corelib.String (failwith "TODO: assert fields and populate") state
-                    (corelib.String
-                     |> TypeInfo.mapGeneric (fun _ _ -> failwith<unit> "there are no generics here"))
-                    (failwith "TODO: assert fields and populate")
-                    state
             // TODO: set the char values in memory
             )
 
@@ -83,71 +79,177 @@ module Program =
             | None -> failwith "No entry point in input DLL"
             | Some d -> d
 
-        let mainMethod = dumped.Methods.[entryPoint]
+        let mainMethodFromMetadata = dumped.Methods.[entryPoint]
 
-        if mainMethod.Signature.GenericParameterCount > 0 then
+        if mainMethodFromMetadata.Signature.GenericParameterCount > 0 then
             failwith "Refusing to execute generic main method"
 
-        let mainMethod =
+        let state = IlMachineState.initial loggerFactory dotnetRuntimeDirs dumped
-            mainMethod
+
-            |> MethodInfo.mapTypeGenerics (fun _ -> failwith "Refusing to execute generic main method")
+        // Find the core library by traversing the type hierarchy of the main method's declaring type
-            |> MethodInfo.mapMethodGenerics (fun _ -> failwith "Refusing to execute generic main method")
+        // until we reach System.Object
+        let rec handleBaseTypeInfo
+            (state : IlMachineState)
+            (baseTypeInfo : BaseTypeInfo)
+            (currentAssembly : DumpedAssembly)
+            (continueWithGeneric :
+                IlMachineState
+                    -> TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>
+                    -> DumpedAssembly
+                    -> IlMachineState * BaseClassTypes<DumpedAssembly> option)
+            (continueWithResolved :
+                IlMachineState
+                    -> TypeInfo<TypeDefn, TypeDefn>
+                    -> DumpedAssembly
+                    -> IlMachineState * BaseClassTypes<DumpedAssembly> option)
+            : IlMachineState * BaseClassTypes<DumpedAssembly> option
+            =
+            match baseTypeInfo with
+            | BaseTypeInfo.TypeRef typeRefHandle ->
+                // Look up the TypeRef from the handle
+                let typeRef = currentAssembly.TypeRefs.[typeRefHandle]
+
+                let rec go state =
+                    // Resolve the type reference to find which assembly it's in
+                    match
+                        Assembly.resolveTypeRef state._LoadedAssemblies currentAssembly typeRef ImmutableArray.Empty
+                    with
+                    | TypeResolutionResult.FirstLoadAssy assyRef ->
+                        // Need to load this assembly first
+                        let handle, definedIn = assyRef.Handle
+
+                        let state, _, _ =
+                            IlMachineState.loadAssembly
+                                loggerFactory
+                                state._LoadedAssemblies.[definedIn.FullName]
+                                handle
+                                state
+
+                        go state
+                    | TypeResolutionResult.Resolved (resolvedAssembly, resolvedType) ->
+                        continueWithResolved state resolvedType resolvedAssembly
+
+                go state
+            | BaseTypeInfo.TypeDef typeDefHandle ->
+                // Base type is in the same assembly
+                let baseType = currentAssembly.TypeDefs.[typeDefHandle]
+                continueWithGeneric state baseType currentAssembly
+            | BaseTypeInfo.TypeSpec _ -> failwith "Type specs not yet supported in base type traversal"
+            | BaseTypeInfo.ForeignAssemblyType (assemblyName, typeDefHandle) ->
+                // Base type is in a foreign assembly
+                match state._LoadedAssemblies.TryGetValue assemblyName.FullName with
+                | true, foreignAssembly ->
+                    let baseType = foreignAssembly.TypeDefs.[typeDefHandle]
+                    continueWithGeneric state baseType foreignAssembly
+                | false, _ -> failwith $"Foreign assembly {assemblyName.FullName} not loaded"
+
+        let rec findCoreLibraryAssemblyFromGeneric
+            (state : IlMachineState)
+            (currentType : TypeInfo<WoofWare.PawPrint.GenericParameter, TypeDefn>)
+            (currentAssembly : DumpedAssembly)
+            =
+            match currentType.BaseType with
+            | None ->
+                // We've reached the root (System.Object), so this assembly contains the core library
+                let baseTypes = Corelib.getBaseTypes currentAssembly
+                state, Some baseTypes
+            | Some baseTypeInfo ->
+                handleBaseTypeInfo
+                    state
+                    baseTypeInfo
+                    currentAssembly
+                    findCoreLibraryAssemblyFromGeneric
+                    findCoreLibraryAssemblyFromResolved
+
+        and findCoreLibraryAssemblyFromResolved
+            (state : IlMachineState)
+            (currentType : TypeInfo<TypeDefn, TypeDefn>)
+            (currentAssembly : DumpedAssembly)
+            =
+            match currentType.BaseType with
+            | None ->
+                // We've reached the root (System.Object), so this assembly contains the core library
+                let baseTypes = Corelib.getBaseTypes currentAssembly
+                state, Some baseTypes
+            | Some baseTypeInfo ->
+                handleBaseTypeInfo
+                    state
+                    baseTypeInfo
+                    currentAssembly
+                    findCoreLibraryAssemblyFromGeneric
+                    findCoreLibraryAssemblyFromResolved
 
         let rec computeState (baseClassTypes : BaseClassTypes<DumpedAssembly> option) (state : IlMachineState) =
-            // The thread's state is slightly fake: we will need to put arguments onto the stack before actually
+            match baseClassTypes with
-            // executing the main method.
+            | Some baseTypes ->
-            // We construct the thread here before we are entirely ready, because we need a thread from which to
+                // We already have base class types, can directly create the concretized method
-            // initialise the class containing the main method.
+                // Use the original method from metadata, but convert FakeUnit to TypeDefn
-            // Once we've obtained e.g. the String and Array classes, we can populate the args array.
+                let rawMainMethod =
-            match
+                    mainMethodFromMetadata
-                MethodState.Empty
+                    |> MethodInfo.mapTypeGenerics (fun i _ -> TypeDefn.GenericTypeParameter i)
-                    (Option.toObj baseClassTypes)
+
-                    state._LoadedAssemblies
+                let state, concretizedMainMethod, _ =
-                    dumped
+                    IlMachineState.concretizeMethodWithTypeGenerics
-                    // pretend there are no instructions, so we avoid preparing anything
+                        loggerFactory
-                    { mainMethod with
+                        baseTypes
+                        ImmutableArray.Empty // No type generics for main method's declaring type
+                        { rawMainMethod with
                             Instructions = Some (MethodInstructions.onlyRet ())
                         }
                         None
+                        dumped.Name
+                        ImmutableArray.Empty
+                        state
+
+                // Create the method state with the concretized method
+                match
+                    MethodState.Empty
+                        state.ConcreteTypes
+                        baseTypes
+                        state._LoadedAssemblies
+                        dumped
+                        concretizedMainMethod
+                        ImmutableArray.Empty
                         (ImmutableArray.CreateRange [ CliType.ObjectRef None ])
                         None
                 with
-            | Ok meth -> IlMachineState.addThread meth dumped.Name state, baseClassTypes
+                | Ok concretizedMeth -> IlMachineState.addThread concretizedMeth dumped.Name state, Some baseTypes
-            | Error requiresRefs ->
+                | Error _ -> failwith "Unexpected failure creating method state with concretized method"
-                let state =
+            | None ->
-                    (state, requiresRefs)
+                // We need to discover the core library by traversing the type hierarchy
-                    ||> List.fold (fun state ref ->
+                let mainMethodType =
-                        let handle, referencingAssy = ref.Handle
+                    dumped.TypeDefs.[mainMethodFromMetadata.DeclaringType.Definition.Get]
-                        let referencingAssy = state.LoadedAssembly referencingAssy |> Option.get
 
-                        let state, _, _ =
+                let state, baseTypes =
-                            IlMachineState.loadAssembly loggerFactory referencingAssy handle state
+                    findCoreLibraryAssemblyFromGeneric state mainMethodType dumped
 
+                computeState baseTypes state
+
+        let (state, mainThread), baseClassTypes = state |> computeState None
+
+        // Now that we have base class types, concretize the main method for use in the rest of the function
+        let state, concretizedMainMethod, mainTypeHandle =
+            match baseClassTypes with
+            | Some baseTypes ->
+                let rawMainMethod =
+                    mainMethodFromMetadata
+                    |> MethodInfo.mapTypeGenerics (fun i _ -> TypeDefn.GenericTypeParameter i)
+
+                IlMachineState.concretizeMethodWithTypeGenerics
+                    loggerFactory
+                    baseTypes
+                    ImmutableArray.Empty // No type generics for main method's declaring type
+                    rawMainMethod
+                    None
+                    dumped.Name
+                    ImmutableArray.Empty
                     state
-                    )
+            | None -> failwith "Expected base class types to be available at this point"
-
-                let corelib =
-                    let coreLib =
-                        state._LoadedAssemblies.Keys
-                        |> Seq.tryFind (fun x -> x.StartsWith ("System.Private.CoreLib, ", StringComparison.Ordinal))
-
-                    coreLib
-                    |> Option.map (fun coreLib -> state._LoadedAssemblies.[coreLib] |> Corelib.getBaseTypes)
-
-                computeState corelib state
-
-        let (state, mainThread), baseClassTypes =
-            IlMachineState.initial loggerFactory dotnetRuntimeDirs dumped
-            |> computeState None
 
         let rec loadInitialState (state : IlMachineState) =
             match
                 state
-                |> IlMachineState.loadClass
+                |> IlMachineState.loadClass loggerFactory (Option.toObj baseClassTypes) mainTypeHandle mainThread
-                    loggerFactory
-                    (Option.toObj baseClassTypes)
-                    mainMethod.DeclaringType
-                    mainThread
             with
             | StateLoadResult.NothingToDo ilMachineState -> ilMachineState
             | StateLoadResult.FirstLoadThis ilMachineState -> loadInitialState ilMachineState
@@ -167,12 +269,12 @@ module Program =
             | Some c -> c
 
         let arrayAllocation, state =
-            match mainMethod.Signature.ParameterTypes |> Seq.toList with
+            match mainMethodFromMetadata.Signature.ParameterTypes |> Seq.toList with
             | [ TypeDefn.OneDimensionalArrayLowerBoundZero (TypeDefn.PrimitiveType PrimitiveType.String) ] ->
                 allocateArgs argv baseClassTypes state
             | _ -> failwith "Main method must take an array of strings; other signatures not yet implemented"
 
-        match mainMethod.Signature.ReturnType with
+        match mainMethodFromMetadata.Signature.ReturnType with
         | TypeDefn.PrimitiveType PrimitiveType.Int32 -> ()
         | _ -> failwith "Main method must return int32; other types not currently supported"
 
@@ -185,15 +287,16 @@ module Program =
         logger.LogInformation "Main method class now initialised"
 
         // Now that BCL initialisation has taken place and the user-code classes are constructed,
-        // overwrite the main thread completely.
+        // overwrite the main thread completely using the already-concretized method.
         let methodState =
             match
                 MethodState.Empty
+                    state.ConcreteTypes
                     baseClassTypes
                     state._LoadedAssemblies
                     dumped
-                    mainMethod
+                    concretizedMainMethod
-                    None
+                    ImmutableArray.Empty
                     (ImmutableArray.Create (CliType.OfManagedObject arrayAllocation))
                     None
             with
@@ -210,11 +313,7 @@ module Program =
             { state with
                 ThreadState = state.ThreadState |> Map.add mainThread threadState
             }
-            |> IlMachineState.ensureTypeInitialised
+            |> IlMachineState.ensureTypeInitialised loggerFactory baseClassTypes mainThread mainTypeHandle
-                loggerFactory
-                baseClassTypes
-                mainThread
-                methodState.ExecutingMethod.DeclaringType
 
         match init with
         | WhatWeDid.SuspendedForClassInit -> failwith "TODO: suspended for class init"

WoofWare.PawPrint/Tuple.fs

@@ -4,3 +4,5 @@ namespace WoofWare.PawPrint
 module internal Tuple =
     let withLeft<'a, 'b> (x : 'a) (y : 'b) : 'a * 'b = x, y
     let withRight<'a, 'b> (y : 'b) (x : 'a) = x, y
+    let lmap<'a, 'b, 'c> (f : 'a -> 'c) (x : 'a, y : 'b) : 'c * 'b = f x, y
+    let rmap<'a, 'b, 'c> (f : 'b -> 'c) (x : 'a, y : 'b) : 'a * 'c = x, f y

WoofWare.PawPrint/TypeInitialisation.fs

@@ -9,21 +9,21 @@ type TypeInitState =
 
 /// Tracks the initialization state of types across assemblies. The string in the key is the FullName of the AssemblyName where the type comes from.
 // TODO: need a better solution than string here! AssemblyName didn't work, we had nonequal assembly names.
-type TypeInitTable = ImmutableDictionary<RuntimeConcreteType, TypeInitState>
+type TypeInitTable = ImmutableDictionary<ConcreteTypeHandle, TypeInitState>
 
 [<RequireQualifiedAccess>]
 module TypeInitTable =
-    let tryGet (ty : RuntimeConcreteType) (t : TypeInitTable) =
+    let tryGet (ty : ConcreteTypeHandle) (t : TypeInitTable) =
         match t.TryGetValue ty with
         | true, v -> Some v
         | false, _ -> None
 
-    let beginInitialising (thread : ThreadId) (ty : RuntimeConcreteType) (t : TypeInitTable) : TypeInitTable =
+    let beginInitialising (thread : ThreadId) (ty : ConcreteTypeHandle) (t : TypeInitTable) : TypeInitTable =
         match t.TryGetValue ty with
         | false, _ -> t.Add (ty, TypeInitState.InProgress thread)
         | true, v -> failwith "Logic error: tried initialising a type which has already started initialising"
 
-    let markInitialised (thread : ThreadId) (ty : RuntimeConcreteType) (t : TypeInitTable) : TypeInitTable =
+    let markInitialised (thread : ThreadId) (ty : ConcreteTypeHandle) (t : TypeInitTable) : TypeInitTable =
         match t.TryGetValue ty with
         | false, _ -> failwith "Logic error: completing initialisation of a type which never started initialising"
         | true, TypeInitState.Initialized ->

WoofWare.PawPrint/UnaryMetadataIlOp.fs

@@ -20,7 +20,7 @@ module internal UnaryMetadataIlOp =
 
         match op with
         | Call ->
-            let state, methodToCall, methodGenerics =
+            let state, methodToCall, methodGenerics, typeArgsFromMetadata =
                 match metadataToken with
                 | MetadataToken.MethodSpecification h ->
                     let spec = activeAssy.MethodSpecs.[h]
@@ -29,11 +29,11 @@ module internal UnaryMetadataIlOp =
                     | MetadataToken.MethodDef token ->
                         let method =
                             activeAssy.Methods.[token]
-                            |> MethodInfo.mapTypeGenerics (fun i _ -> spec.Signature.[i])
+                            |> MethodInfo.mapTypeGenerics (fun i _ -> TypeDefn.GenericTypeParameter i)
 
-                        state, method, Some spec.Signature
+                        state, method, Some spec.Signature, None
                     | MetadataToken.MemberReference ref ->
-                        let state, _, method =
+                        let state, _, method, extractedTypeArgs =
                             IlMachineState.resolveMember
                                 loggerFactory
                                 baseClassTypes
@@ -44,10 +44,10 @@ module internal UnaryMetadataIlOp =
 
                         match method with
                         | Choice2Of2 _field -> failwith "tried to Call a field"
-                        | Choice1Of2 method -> state, method, Some spec.Signature
+                        | Choice1Of2 method -> state, method, Some spec.Signature, Some extractedTypeArgs
                     | k -> failwith $"Unrecognised kind: %O{k}"
                 | MetadataToken.MemberReference h ->
-                    let state, _, method =
+                    let state, _, method, extractedTypeArgs =
                         IlMachineState.resolveMember
                             loggerFactory
                             baseClassTypes
@@ -58,18 +58,114 @@ module internal UnaryMetadataIlOp =
 
                     match method with
                     | Choice2Of2 _field -> failwith "tried to Call a field"
-                    | Choice1Of2 method -> state, method, None
+                    | Choice1Of2 method -> state, method, None, Some extractedTypeArgs
 
                 | MetadataToken.MethodDef defn ->
                     match activeAssy.Methods.TryGetValue defn with
                     | true, method ->
                         let method = method |> MethodInfo.mapTypeGenerics (fun _ -> failwith "not generic")
-                        state, method, None
+                        state, method, None, None
                     | false, _ -> failwith $"could not find method in {activeAssy.Name}"
                 | k -> failwith $"Unrecognised kind: %O{k}"
 
-            match IlMachineState.loadClass loggerFactory baseClassTypes methodToCall.DeclaringType thread state with
+            let state, concretizedMethod, declaringTypeHandle =
+                IlMachineState.concretizeMethodForExecution
+                    loggerFactory
+                    baseClassTypes
+                    thread
+                    methodToCall
+                    methodGenerics
+                    typeArgsFromMetadata
+                    state
+
+            match IlMachineState.loadClass loggerFactory baseClassTypes declaringTypeHandle thread state with
             | NothingToDo state ->
+                let state, _ =
+                    state.WithThreadSwitchedToAssembly methodToCall.DeclaringType.Assembly thread
+
+                let threadState = state.ThreadState.[thread]
+
+                IlMachineState.callMethod
+                    loggerFactory
+                    baseClassTypes
+                    None
+                    None
+                    false
+                    true
+                    concretizedMethod.Generics
+                    concretizedMethod
+                    thread
+                    threadState
+                    state,
+                WhatWeDid.Executed
+            | FirstLoadThis state -> state, WhatWeDid.SuspendedForClassInit
+
+        | Callvirt ->
+
+            // TODO: this is presumably super incomplete
+            let state, methodToCall, methodGenerics, typeArgsFromMetadata =
+                match metadataToken with
+                | MetadataToken.MethodSpecification h ->
+                    let spec = activeAssy.MethodSpecs.[h]
+
+                    match spec.Method with
+                    | MetadataToken.MethodDef token ->
+                        let method =
+                            activeAssy.Methods.[token]
+                            |> MethodInfo.mapTypeGenerics (fun i _ -> spec.Signature.[i])
+
+                        state, method, Some spec.Signature, None
+                    | MetadataToken.MemberReference ref ->
+                        let state, _, method, extractedTypeArgs =
+                            IlMachineState.resolveMember
+                                loggerFactory
+                                baseClassTypes
+                                thread
+                                (state.ActiveAssembly thread)
+                                ref
+                                state
+
+                        match method with
+                        | Choice2Of2 _field -> failwith "tried to Callvirt a field"
+                        | Choice1Of2 method -> state, method, Some spec.Signature, Some extractedTypeArgs
+                    | k -> failwith $"Unrecognised kind: %O{k}"
+                | MetadataToken.MemberReference h ->
+                    let state, _, method, extractedTypeArgs =
+                        IlMachineState.resolveMember
+                            loggerFactory
+                            baseClassTypes
+                            thread
+                            (state.ActiveAssembly thread)
+                            h
+                            state
+
+                    match method with
+                    | Choice2Of2 _field -> failwith "tried to Callvirt a field"
+                    | Choice1Of2 method -> state, method, None, Some extractedTypeArgs
+
+                | MetadataToken.MethodDef defn ->
+                    match activeAssy.Methods.TryGetValue defn with
+                    | true, method ->
+                        let method = method |> MethodInfo.mapTypeGenerics (fun _ -> failwith "not generic")
+                        state, method, None, None
+                    | false, _ -> failwith $"could not find method in {activeAssy.Name}"
+                | k -> failwith $"Unrecognised kind: %O{k}"
+
+            // TODO: this is pretty inefficient, we're concretising here and then immediately after in callMethodInActiveAssembly
+            let state, concretizedMethod, declaringTypeHandle =
+                IlMachineState.concretizeMethodForExecution
+                    loggerFactory
+                    baseClassTypes
+                    thread
+                    methodToCall
+                    methodGenerics
+                    typeArgsFromMetadata
+                    state
+
+            match IlMachineState.loadClass loggerFactory baseClassTypes declaringTypeHandle thread state with
+            | FirstLoadThis state -> state, WhatWeDid.SuspendedForClassInit
+            | NothingToDo state ->
+
             state.WithThreadSwitchedToAssembly methodToCall.DeclaringType.Assembly thread
             |> fst
             |> IlMachineState.callMethodInActiveAssembly
@@ -80,78 +176,23 @@ module internal UnaryMetadataIlOp =
                 methodGenerics
                 methodToCall
                 None
-            | FirstLoadThis state -> state, WhatWeDid.SuspendedForClassInit
+                typeArgsFromMetadata
-
-        | Callvirt ->
-
-            // TODO: this is presumably super incomplete
-            let state, method, generics =
-                match metadataToken with
-                | MetadataToken.MethodSpecification h ->
-                    let spec = activeAssy.MethodSpecs.[h]
-
-                    match spec.Method with
-                    | MetadataToken.MethodDef token ->
-                        let method =
-                            activeAssy.Methods.[token]
-                            |> MethodInfo.mapTypeGenerics (fun i _ -> spec.Signature.[i])
-
-                        state, method, Some spec.Signature
-                    | MetadataToken.MemberReference ref ->
-                        let state, _, method =
-                            IlMachineState.resolveMember
-                                loggerFactory
-                                baseClassTypes
-                                thread
-                                (state.ActiveAssembly thread)
-                                ref
-                                state
-
-                        match method with
-                        | Choice2Of2 _field -> failwith "tried to Callvirt a field"
-                        | Choice1Of2 method -> state, method, Some spec.Signature
-                    | k -> failwith $"Unrecognised kind: %O{k}"
-                | MetadataToken.MemberReference h ->
-                    let state, _, method =
-                        IlMachineState.resolveMember
-                            loggerFactory
-                            baseClassTypes
-                            thread
-                            (state.ActiveAssembly thread)
-                            h
-                            state
-
-                    match method with
-                    | Choice2Of2 _field -> failwith "tried to Callvirt a field"
-                    | Choice1Of2 method -> state, method, None
-
-                | MetadataToken.MethodDef defn ->
-                    match activeAssy.Methods.TryGetValue defn with
-                    | true, method ->
-                        let method = method |> MethodInfo.mapTypeGenerics (fun _ -> failwith "not generic")
-                        state, method, None
-                    | false, _ -> failwith $"could not find method in {activeAssy.Name}"
-                | k -> failwith $"Unrecognised kind: %O{k}"
-
-            match IlMachineState.loadClass loggerFactory baseClassTypes method.DeclaringType thread state with
-            | FirstLoadThis state -> state, WhatWeDid.SuspendedForClassInit
-            | NothingToDo state ->
-
-            state.WithThreadSwitchedToAssembly method.DeclaringType.Assembly thread
-            |> fst
-            |> IlMachineState.callMethodInActiveAssembly loggerFactory baseClassTypes thread true generics method None
 
         | Castclass -> failwith "TODO: Castclass unimplemented"
         | Newobj ->
             let logger = loggerFactory.CreateLogger "Newobj"
 
-            let state, assy, ctor =
+            let state, assy, ctor, typeArgsFromMetadata =
                 match metadataToken with
                 | MethodDef md ->
                     let method = activeAssy.Methods.[md]
-                    state, activeAssy.Name, MethodInfo.mapTypeGenerics (fun _ -> failwith "non-generic method") method
+
+                    state,
+                    activeAssy.Name,
+                    MethodInfo.mapTypeGenerics (fun _ -> failwith "non-generic method") method,
+                    None
                 | MemberReference mr ->
-                    let state, name, method =
+                    let state, name, method, extractedTypeArgs =
                         IlMachineState.resolveMember
                             loggerFactory
                             baseClassTypes
@@ -161,12 +202,24 @@ module internal UnaryMetadataIlOp =
                             state
 
                     match method with
-                    | Choice1Of2 mr -> state, name, mr
+                    | Choice1Of2 mr -> state, name, mr, Some extractedTypeArgs
                     | 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
+                    baseClassTypes
+                    thread
+                    ctor
+                    None
+                    typeArgsFromMetadata
+                    state
+
             let state, init =
-                IlMachineState.ensureTypeInitialised loggerFactory baseClassTypes thread ctor.DeclaringType state
+                IlMachineState.ensureTypeInitialised loggerFactory baseClassTypes thread declaringTypeHandle state
 
             match init with
             | WhatWeDid.BlockedOnClassInit state -> failwith "TODO: another thread is running the initialiser"
@@ -184,9 +237,7 @@ module internal UnaryMetadataIlOp =
                 )
 
             let typeGenerics =
-                match ctor.DeclaringType.Generics with
+                concretizedCtor.DeclaringType.Generics |> ImmutableArray.CreateRange
-                | [] -> None
-                | l -> Some (ImmutableArray.CreateRange l)
 
             let state, fieldZeros =
                 ((state, []), ctorType.Fields)
@@ -199,7 +250,7 @@ module internal UnaryMetadataIlOp =
                             ctorAssembly
                             field.Signature
                             typeGenerics
-                            None
+                            ImmutableArray.Empty
                             state
 
                     state, (field.Name, zero) :: zeros
@@ -232,6 +283,7 @@ module internal UnaryMetadataIlOp =
                     None
                     ctor
                     (Some allocatedAddr)
+                    typeArgsFromMetadata
 
             match whatWeDid with
             | SuspendedForClassInit -> failwith "unexpectedly suspended while initialising constructor"
@@ -255,9 +307,8 @@ module internal UnaryMetadataIlOp =
                 | popped -> failwith $"unexpectedly popped value %O{popped} to serve as array len"
 
             let typeGenerics =
-                match newMethodState.ExecutingMethod.DeclaringType.Generics with
+                newMethodState.ExecutingMethod.DeclaringType.Generics
-                | [] -> None
+                |> ImmutableArray.CreateRange
-                | l -> Some (ImmutableArray.CreateRange l)
 
             let state, elementType, assy =
                 match metadataToken with
@@ -274,14 +325,30 @@ module internal UnaryMetadataIlOp =
                         | ResolvedBaseType.Enum
                         | ResolvedBaseType.ValueType -> SignatureTypeKind.ValueType
                         | ResolvedBaseType.Object -> SignatureTypeKind.Class
-                        | ResolvedBaseType.Delegate -> failwith "TODO: delegate"
+                        | ResolvedBaseType.Delegate -> SignatureTypeKind.Class
 
                     let result =
+                        if defn.Generics.IsEmpty then
                             TypeDefn.FromDefinition (
                                 ComparableTypeDefinitionHandle.Make defn.TypeDefHandle,
-                            defn.Assembly.Name,
+                                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 ->
@@ -290,6 +357,18 @@ module internal UnaryMetadataIlOp =
                 | 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
@@ -307,7 +386,7 @@ module internal UnaryMetadataIlOp =
                         | ResolvedBaseType.Enum
                         | ResolvedBaseType.ValueType -> SignatureTypeKind.ValueType
                         | ResolvedBaseType.Object -> SignatureTypeKind.Class
-                        | ResolvedBaseType.Delegate -> failwith "TODO: delegate"
+                        | ResolvedBaseType.Delegate -> SignatureTypeKind.Class
 
                     let result =
                         TypeDefn.FromDefinition (
@@ -393,7 +472,7 @@ module internal UnaryMetadataIlOp =
                         | ResolvedBaseType.Enum
                         | ResolvedBaseType.ValueType -> SignatureTypeKind.ValueType
                         | ResolvedBaseType.Object -> SignatureTypeKind.Class
-                        | ResolvedBaseType.Delegate -> failwith "todo"
+                        | ResolvedBaseType.Delegate -> SignatureTypeKind.Class
 
                     TypeDefn.FromDefinition (ComparableTypeDefinitionHandle.Make td, activeAssy.Name.FullName, sigType)
                 | MetadataToken.TypeSpecification handle -> state.ActiveAssembly(thread).TypeSpecs.[handle].Signature
@@ -435,7 +514,7 @@ module internal UnaryMetadataIlOp =
 
                     state, field
                 | MetadataToken.MemberReference mr ->
-                    let state, _, field =
+                    let state, _, field, _ =
                         IlMachineState.resolveMember loggerFactory baseClassTypes thread activeAssy mr state
 
                     match field with
@@ -456,10 +535,8 @@ module internal UnaryMetadataIlOp =
 
             let valueToStore, state = IlMachineState.popEvalStack thread state
 
-            let typeGenerics =
+            let state, declaringTypeHandle, typeGenerics =
-                match field.DeclaringType.Generics with
+                IlMachineState.concretizeFieldForExecution loggerFactory baseClassTypes thread field state
-                | [] -> None
-                | l -> Some (ImmutableArray.CreateRange l)
 
             let state, zero =
                 IlMachineState.cliTypeZeroOf
@@ -468,7 +545,7 @@ module internal UnaryMetadataIlOp =
                     (state.ActiveAssembly thread)
                     field.Signature
                     typeGenerics
-                    None // field can't have its own generics
+                    ImmutableArray.Empty // field can't have its own generics
                     state
 
             let valueToStore = EvalStackValue.toCliTypeCoerced zero valueToStore
@@ -477,7 +554,7 @@ module internal UnaryMetadataIlOp =
 
             if field.Attributes.HasFlag FieldAttributes.Static then
                 let state =
-                    IlMachineState.setStatic field.DeclaringType field.Name valueToStore state
+                    IlMachineState.setStatic declaringTypeHandle field.Name valueToStore state
 
                 state, WhatWeDid.Executed
             else
@@ -534,7 +611,7 @@ module internal UnaryMetadataIlOp =
 
                         state, field
                 | MetadataToken.MemberReference mr ->
-                    let state, _, method =
+                    let state, _, method, _ =
                         IlMachineState.resolveMember
                             loggerFactory
                             baseClassTypes
@@ -563,17 +640,15 @@ module internal UnaryMetadataIlOp =
                     field.Signature
                 )
 
-            match IlMachineState.loadClass loggerFactory baseClassTypes field.DeclaringType thread state with
+            let state, declaringTypeHandle, typeGenerics =
+                IlMachineState.concretizeFieldForExecution loggerFactory baseClassTypes thread field state
+
+            match IlMachineState.loadClass loggerFactory baseClassTypes declaringTypeHandle thread state with
             | FirstLoadThis state -> state, WhatWeDid.SuspendedForClassInit
             | NothingToDo state ->
 
             let popped, state = IlMachineState.popEvalStack thread state
 
-            let typeGenerics =
-                match field.DeclaringType.Generics with
-                | [] -> None
-                | l -> Some (ImmutableArray.CreateRange l)
-
             let state, zero =
                 IlMachineState.cliTypeZeroOf
                     loggerFactory
@@ -581,13 +656,13 @@ module internal UnaryMetadataIlOp =
                     activeAssy
                     field.Signature
                     typeGenerics
-                    None // field can't have its own generics
+                    ImmutableArray.Empty // field can't have its own generics
                     state
 
             let toStore = EvalStackValue.toCliTypeCoerced zero popped
 
             let state =
-                IlMachineState.setStatic field.DeclaringType field.Name toStore state
+                IlMachineState.setStatic declaringTypeHandle field.Name toStore state
                 |> IlMachineState.advanceProgramCounter thread
 
             state, WhatWeDid.Executed
@@ -602,7 +677,7 @@ module internal UnaryMetadataIlOp =
 
                     state, field
                 | MetadataToken.MemberReference mr ->
-                    let state, assyName, field =
+                    let state, assyName, field, _ =
                         IlMachineState.resolveMember loggerFactory baseClassTypes thread activeAssy mr state
 
                     match field with
@@ -624,14 +699,15 @@ module internal UnaryMetadataIlOp =
 
             let currentObj, state = IlMachineState.popEvalStack thread state
 
-            let typeGenerics =
+            let state, declaringTypeHandle, typeGenerics =
-                match field.DeclaringType.Generics with
+                IlMachineState.concretizeFieldForExecution loggerFactory baseClassTypes thread field state
-                | [] -> None
-                | l -> Some (ImmutableArray.CreateRange l)
 
             if field.Attributes.HasFlag FieldAttributes.Static then
+                let declaringTypeHandle, state =
+                    IlMachineState.concretizeFieldDeclaringType loggerFactory baseClassTypes field.DeclaringType state
+
                 let state, staticField =
-                    match IlMachineState.getStatic field.DeclaringType field.Name state with
+                    match IlMachineState.getStatic declaringTypeHandle field.Name state with
                     | Some v -> state, v
                     | None ->
                         let state, zero =
@@ -641,10 +717,10 @@ module internal UnaryMetadataIlOp =
                                 (state.LoadedAssembly(field.DeclaringType.Assembly).Value)
                                 field.Signature
                                 typeGenerics
-                                None // field can't have its own generics
+                                ImmutableArray.Empty // field can't have its own generics
                                 state
 
-                        let state = IlMachineState.setStatic field.DeclaringType field.Name zero state
+                        let state = IlMachineState.setStatic declaringTypeHandle field.Name zero state
                         state, zero
 
                 let state = state |> IlMachineState.pushToEvalStack staticField thread
@@ -705,7 +781,7 @@ module internal UnaryMetadataIlOp =
 
                         state, field
                 | MetadataToken.MemberReference mr ->
-                    let state, _, field =
+                    let state, _, field, _ =
                         IlMachineState.resolveMember loggerFactory baseClassTypes thread activeAssy mr state
 
                     match field with
@@ -727,17 +803,15 @@ module internal UnaryMetadataIlOp =
                     field.Signature
                 )
 
-            match IlMachineState.loadClass loggerFactory baseClassTypes field.DeclaringType thread state with
+            let state, declaringTypeHandle, typeGenerics =
+                IlMachineState.concretizeFieldForExecution loggerFactory baseClassTypes thread field state
+
+            match IlMachineState.loadClass loggerFactory baseClassTypes declaringTypeHandle thread state with
             | FirstLoadThis state -> state, WhatWeDid.SuspendedForClassInit
             | NothingToDo state ->
 
-            let typeGenerics =
-                match field.DeclaringType.Generics with
-                | [] -> None
-                | l -> Some (ImmutableArray.CreateRange l)
-
             let fieldValue, state =
-                match IlMachineState.getStatic field.DeclaringType field.Name state with
+                match IlMachineState.getStatic declaringTypeHandle field.Name state with
                 | None ->
                     let state, newVal =
                         IlMachineState.cliTypeZeroOf
@@ -746,10 +820,10 @@ module internal UnaryMetadataIlOp =
                             activeAssy
                             field.Signature
                             typeGenerics
-                            None // field can't have its own generics
+                            ImmutableArray.Empty // field can't have its own generics
                             state
 
-                    newVal, IlMachineState.setStatic field.DeclaringType field.Name newVal state
+                    newVal, IlMachineState.setStatic declaringTypeHandle field.Name newVal state
                 | Some v -> v, state
 
             do
@@ -783,9 +857,7 @@ module internal UnaryMetadataIlOp =
             let currentMethod = state.ThreadState.[thread].MethodState.ExecutingMethod
 
             let declaringTypeGenerics =
-                match currentMethod.DeclaringType.Generics with
+                currentMethod.DeclaringType.Generics |> ImmutableArray.CreateRange
-                | [] -> None
-                | x -> Some (ImmutableArray.CreateRange x)
 
             let state, assy, elementType =
                 match metadataToken with
@@ -793,9 +865,10 @@ module internal UnaryMetadataIlOp =
                     state,
                     assy,
                     assy.TypeDefs.[defn]
-                    |> TypeInfo.mapGeneric (fun _ i -> declaringTypeGenerics.Value.[i.SequenceNumber])
+                    |> TypeInfo.mapGeneric (fun _ p -> TypeDefn.GenericTypeParameter p.SequenceNumber)
                 | MetadataToken.TypeSpecification spec ->
-                    IlMachineState.resolveTypeFromSpec
+                    let state, assy, ty =
+                        IlMachineState.resolveTypeFromSpecConcrete
                             loggerFactory
                             baseClassTypes
                             spec
@@ -803,6 +876,8 @@ module internal UnaryMetadataIlOp =
                             declaringTypeGenerics
                             currentMethod.Generics
                             state
+
+                    state, assy, ty
                 | x -> failwith $"TODO: Stelem element type resolution unimplemented for {x}"
 
             let contents, state = IlMachineState.popEvalStack thread state
@@ -836,7 +911,7 @@ module internal UnaryMetadataIlOp =
                     assy
                     elementType
                     declaringTypeGenerics
-                    None
+                    ImmutableArray.Empty
                     state
 
             let contents = EvalStackValue.toCliTypeCoerced zeroOfType contents
@@ -852,9 +927,7 @@ module internal UnaryMetadataIlOp =
             let currentMethod = state.ThreadState.[thread].MethodState.ExecutingMethod
 
             let declaringTypeGenerics =
-                match currentMethod.DeclaringType.Generics with
+                currentMethod.DeclaringType.Generics |> ImmutableArray.CreateRange
-                | [] -> None
-                | x -> Some (ImmutableArray.CreateRange x)
 
             let state, assy, elementType =
                 match metadataToken with
@@ -862,9 +935,10 @@ module internal UnaryMetadataIlOp =
                     state,
                     assy,
                     assy.TypeDefs.[defn]
-                    |> TypeInfo.mapGeneric (fun _ i -> declaringTypeGenerics.Value.[i.SequenceNumber])
+                    |> TypeInfo.mapGeneric (fun _ p -> TypeDefn.GenericTypeParameter p.SequenceNumber)
                 | MetadataToken.TypeSpecification spec ->
-                    IlMachineState.resolveTypeFromSpec
+                    let state, assy, ty =
+                        IlMachineState.resolveTypeFromSpecConcrete
                             loggerFactory
                             baseClassTypes
                             spec
@@ -872,6 +946,8 @@ module internal UnaryMetadataIlOp =
                             declaringTypeGenerics
                             currentMethod.Generics
                             state
+
+                    state, assy, ty
                 | x -> failwith $"TODO: Ldelem element type resolution unimplemented for {x}"
 
             let index, state = IlMachineState.popEvalStack thread state
@@ -898,7 +974,7 @@ module internal UnaryMetadataIlOp =
                     else
                         failwith "TODO: raise an out of bounds"
 
-            failwith $"TODO: Ldelem {index} {arr} resulted in {toPush}"
+            IlMachineState.pushToEvalStack toPush thread state
             |> IlMachineState.advanceProgramCounter thread
             |> Tuple.withRight WhatWeDid.Executed
         | Initobj -> failwith "TODO: Initobj unimplemented"
@@ -916,22 +992,20 @@ module internal UnaryMetadataIlOp =
                         |> FieldInfo.mapTypeGenerics (fun _ _ -> failwith "generics not allowed on FieldDefinition")
                 | t -> failwith $"Unexpectedly asked to load a non-field: {t}"
 
-            match IlMachineState.loadClass loggerFactory baseClassTypes field.DeclaringType thread state with
+            let state, declaringTypeHandle, typeGenerics =
+                IlMachineState.concretizeFieldForExecution loggerFactory baseClassTypes thread field state
+
+            match IlMachineState.loadClass loggerFactory baseClassTypes declaringTypeHandle thread state with
             | FirstLoadThis state -> state, WhatWeDid.SuspendedForClassInit
             | NothingToDo state ->
 
             if TypeDefn.isManaged field.Signature then
-                match IlMachineState.getStatic field.DeclaringType field.Name state with
+                match IlMachineState.getStatic declaringTypeHandle field.Name state with
                 | Some v ->
                     IlMachineState.pushToEvalStack v thread state
                     |> IlMachineState.advanceProgramCounter thread
                     |> Tuple.withRight WhatWeDid.Executed
                 | None ->
-                    let typeGenerics =
-                        match field.DeclaringType.Generics with
-                        | [] -> None
-                        | l -> Some (ImmutableArray.CreateRange l)
-
                     // Field is not yet initialised
                     let state, zero =
                         IlMachineState.cliTypeZeroOf
@@ -940,10 +1014,10 @@ module internal UnaryMetadataIlOp =
                             activeAssy
                             field.Signature
                             typeGenerics
-                            None // field can't have its own generics
+                            ImmutableArray.Empty // field can't have its own generics
                             state
 
-                    IlMachineState.setStatic field.DeclaringType field.Name zero state
+                    IlMachineState.setStatic declaringTypeHandle field.Name zero state
                     |> IlMachineState.pushToEvalStack (CliType.ObjectRef None) thread
                     |> IlMachineState.advanceProgramCounter thread
                     |> Tuple.withRight WhatWeDid.Executed
@@ -953,11 +1027,37 @@ module internal UnaryMetadataIlOp =
         | Ldftn ->
             let logger = loggerFactory.CreateLogger "Ldftn"
 
-            let method =
+            let (method : MethodInfo<TypeDefn, WoofWare.PawPrint.GenericParameter, TypeDefn>), methodGenerics =
                 match metadataToken with
-                | MetadataToken.MethodDef handle -> activeAssy.Methods.[handle]
+                | MetadataToken.MethodDef handle ->
+                    let method =
+                        activeAssy.Methods.[handle]
+                        |> MethodInfo.mapTypeGenerics (fun i _ -> TypeDefn.GenericTypeParameter i)
+
+                    method, None
+                | MetadataToken.MethodSpecification h ->
+                    let spec = activeAssy.MethodSpecs.[h]
+
+                    match spec.Method with
+                    | MetadataToken.MethodDef token ->
+                        let method =
+                            activeAssy.Methods.[token]
+                            |> MethodInfo.mapTypeGenerics (fun i _ -> TypeDefn.GenericTypeParameter i)
+
+                        method, Some spec.Signature
+                    | k -> failwith $"Unrecognised MethodSpecification kind: %O{k}"
                 | t -> failwith $"Unexpectedly asked to Ldftn a non-method: {t}"
 
+            let state, concretizedMethod, _declaringTypeHandle =
+                IlMachineState.concretizeMethodForExecution
+                    loggerFactory
+                    baseClassTypes
+                    thread
+                    method
+                    methodGenerics
+                    None
+                    state
+
             logger.LogDebug (
                 "Pushed pointer to function {LdFtnAssembly}.{LdFtnType}.{LdFtnMethodName}",
                 method.DeclaringType.Assembly.Name,
@@ -967,7 +1067,7 @@ module internal UnaryMetadataIlOp =
 
             state
             |> IlMachineState.pushToEvalStack'
-                (EvalStackValue.NativeInt (NativeIntSource.FunctionPointer method))
+                (EvalStackValue.NativeInt (NativeIntSource.FunctionPointer concretizedMethod))
                 thread
             |> IlMachineState.advanceProgramCounter thread
             |> Tuple.withRight WhatWeDid.Executed
@@ -999,8 +1099,7 @@ module internal UnaryMetadataIlOp =
 
                     let currentMethod = state.ThreadState.[thread].MethodState
 
-                    let methodGenerics =
+                    let methodGenerics = currentMethod.Generics
-                        currentMethod.Generics |> Option.defaultValue ImmutableArray.Empty
 
                     let typeGenerics = currentMethod.ExecutingMethod.DeclaringType.Generics
 

WoofWare.PawPrint/UnaryStringTokenIlOp.fs

@@ -52,11 +52,7 @@ module internal UnaryStringTokenIlOp =
                         ]
 
                     let addr, state =
-                        IlMachineState.allocateManagedObject
+                        IlMachineState.allocateManagedObject baseClassTypes.String fields state
-                            (baseClassTypes.String
-                             |> TypeInfo.mapGeneric (fun _ _ -> failwith<unit> "string is not generic"))
-                            fields
-                            state
 
                     addr,
                     { state with