[cdac] Extract ITypeHandle interface and add synthetic type handles by max-charlamb · Pull Request #129800 · dotnet/runtime

max-charlamb · 2026-06-24T14:31:07Z

Summary

Convert TypeHandle from a readonly struct to the ITypeHandle interface, enabling synthetic (reader-fabricated) TypeHandles for unloaded constructed types (Ptr, Byref, SzArray, Array).

Changes

Rename TypeHandle -> ITypeHandle across entire cDAC codebase
ITypeHandle interface in Abstractions with Address, IsNull, IsSynthetic
NullTypeHandle singleton in Abstractions (ITypeHandle.Null)
TargetTypeHandle struct in Contracts (real target-backed handles)
SyntheticTypeHandle internal class in Contracts (unloaded constructed types)
10 RTS methods with synthetic-aware branches
GetConstructedType synthesizes on miss for Ptr/Byref/SzArray/Array instead of returning null
ReadOnlySpan<TypeHandle> replaced with ITypeHandle[] in public API

Motivation

When decoding method signatures, the runtime frequently has no loaded TypeHandle for constructed types like int*, ref T, or T[]. Previously GetConstructedType returned null, forcing consumers into ad-hoc side-channels. Now it returns a synthetic handle that downstream contracts can query uniformly.

Note

This content was generated with the assistance of GitHub Copilot.

dotnet-policy-service · 2026-06-24T14:37:54Z

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Copilot

Pull request overview

This PR refactors cDAC’s type identity from a concrete TypeHandle struct to an ITypeHandle abstraction, enabling “synthetic” (reader-fabricated) handles for unloaded constructed types (Ptr/Byref/SZArray/Array) and updating the contracts/legacy layers/tests accordingly.

Changes:

Introduces ITypeHandle (+ null/synthetic/target-backed implementations) and updates contracts to traffic in ITypeHandle.
Updates RuntimeTypeSystem_1.GetConstructedType to synthesize constructed types on miss for Ptr/Byref/SZArray/Array.
Updates legacy SOS/DacDbi code and cDAC unit/dump tests to consume the new handle abstraction.

Reviewed changes

Copilot reviewed 52 out of 52 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/native/managed/cdac/tests/UnitTests/TypeDescTests.cs	Updates unit tests to use `ITypeHandle` and array-returning APIs.
src/native/managed/cdac/tests/UnitTests/SOSDacInterface5Tests.cs	Switches test setup to `TargetTypeHandle`.
src/native/managed/cdac/tests/UnitTests/RuntimeMutableTypeSystemTests.cs	Updates Moq setups and APIs to `ITypeHandle`.
src/native/managed/cdac/tests/UnitTests/ObjectTests.cs	Updates object contract tests to use `TargetTypeHandle`.
src/native/managed/cdac/tests/UnitTests/MethodTableTests.cs	Replaces `TypeHandle` usage with `ITypeHandle` across MT tests.
src/native/managed/cdac/tests/UnitTests/MethodDescTests.cs	Updates generic-instantiation test assertions to use `ITypeHandle[]`.
src/native/managed/cdac/tests/UnitTests/ExceptionTests.cs	Updates exception contract tests to use `TargetTypeHandle`.
src/native/managed/cdac/tests/UnitTests/DacDbiImplTests.cs	Updates DacDbi tests to use `TargetTypeHandle` and new APIs.
src/native/managed/cdac/tests/UnitTests/CodeVersionsTests.cs	Updates code versions test helpers to use `ITypeHandle`.
src/native/managed/cdac/tests/DumpTests/RuntimeTypeSystemDumpTests.cs	Updates dump tests to the `ITypeHandle` API surface.
src/native/managed/cdac/tests/DumpTests/ObjectiveCMarshalDumpTests.cs	Updates dump test to `ITypeHandle`.
src/native/managed/cdac/tests/DumpTests/IXCLRDataValueDumpTests.cs	Updates commentary/type references for `ITypeHandle`.
src/native/managed/cdac/tests/DumpTests/IXCLRDataMethodDefinitionDumpTests.cs	Updates dump test to `ITypeHandle`.
src/native/managed/cdac/tests/DumpTests/DacDbi/DacDbiObjectDumpTests.cs	Updates DacDbi dump tests and helpers to `ITypeHandle`.
src/native/managed/cdac/tests/DumpTests/DacDbi/DacDbiLoaderDumpTests.cs	Updates DacDbi loader dump test to `ITypeHandle`.
src/native/managed/cdac/tests/DumpTests/DacDbi/DacDbiExactTypeHandleDumpTests.cs	Updates exact-typehandle roundtrip dump test to `ITypeHandle`.
src/native/managed/cdac/tests/DumpTests/CCWDumpTests.cs	Updates CCW dump test wording and `ITypeHandle` usage.
src/native/managed/cdac/tests/DumpTests/AsyncContinuationDumpTests.cs	Updates continuation dump tests to `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/TypeNameBuilder.cs	Updates type/method name formatting to consume `ITypeHandle` and array-returning instantiation APIs.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/SOSDacImpl.IXCLRDataProcess.cs	Updates IXCLRDataProcess implementation to `ITypeHandle` and array-returning APIs.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/SOSDacImpl.cs	Updates SOS DAC implementation to `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/SigFormat.cs	Updates signature formatting helpers to use `ITypeHandle` and array-returning APIs.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/IDacDbiInterface.cs	Updates interop struct comments to refer to `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/Helpers/HeapWalk.cs	Updates heap-walk helper to use `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/DacDbiImpl.cs	Updates DacDbi implementation to use `ITypeHandle` and constructed-type synthesis.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/ClrDataMethodInstance.cs	Updates method instance implementation to use `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/ClrDataMethodDefinition.cs	Updates generic-instantiation checks to `ITypeHandle[]`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/ClrDataFrame.cs	Updates frame/type resolution paths to use `ITypeHandle` and array-returning instantiations.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/RuntimeTypeSystemHelpers/ExtensionMethods.cs	Adapts type-handle helper extensions to operate on `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/GC/GcSignatureTypeProvider.cs	Updates GC signature decoding context and lookups to `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/FrameHandling/FrameHelpers.cs	Updates frame helper logic to use `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Signature/SignatureTypeProvider.cs	Updates signature type provider to produce/consume `ITypeHandle` and constructed types.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Signature/Signature_1.cs	Updates signature contract implementation to decode to `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Signature/IRuntimeSignatureTypeProvider.cs	Updates documentation for “internal type” handling to `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/RuntimeTypeSystem/TypeHandleImplementations.cs	Adds `TargetTypeHandle` and `SyntheticTypeHandle` implementations of `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/RuntimeTypeSystem_1.cs	Core RuntimeTypeSystem changes: `ITypeHandle` plumbing + synthetic constructed-type behavior.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/RuntimeMutableTypeSystem_1.cs	Updates mutable type system APIs to accept `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Object_1.cs	Updates object sizing/array logic to use `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/ManagedTypeSource_1.cs	Updates managed type resolution/caching to `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/ExecutionManager/ExecutionManagerCore.cs	Updates exception-clause reading path to use `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Exception_1.cs	Updates exception contract implementation to use `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/ConditionalWeakTable_1.cs	Updates CWT contract implementation to use `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/ComWrappers_1.cs	Updates RCW detection to use the renamed generated type-handle accessor.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/CodeVersions_1.cs	Updates code-versions contract to use `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/ISignature.cs	Changes signature decoding contract to return `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IRuntimeTypeSystem.cs	Introduces `ITypeHandle`/`NullTypeHandle` and updates the RuntimeTypeSystem contract signatures.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IRuntimeMutableTypeSystem.cs	Updates mutable-type-system contract signature to use `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IManagedTypeSource.cs	Updates managed type source contract to use `ITypeHandle`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/CdacAttributes.cs	Updates generator-related docs to refer to `ITypeHandle`.
src/native/managed/cdac/gen/TypeNameResolverSource.cs	Updates generated helper to return `ITypeHandle`.
src/native/managed/cdac/gen/Emitter.cs	Updates generated output to reference `ITypeHandle`.
src/native/managed/cdac/gen/CdacGenerator.cs	Updates generator docs to refer to `ITypeHandle`.

+/// <summary>
+/// An opaque handle to a runtime type. May represent a loaded type (backed by a
+/// target-process MethodTable or TypeDesc address) or a synthetic type fabricated
+/// by the reader for unloaded constructed types.
+/// </summary>
+public interface ITypeHandle : IEquatable<ITypeHandle>
 {
-    // TODO-Layering: These members should be accessible only to contract implementations.
-    public TypeHandle(TargetPointer address)
-    {
-        Address = address;
-    }
-
-    public TargetPointer Address { get; }
+    TargetPointer Address { get; }
+    bool IsNull { get; }
+    bool IsSynthetic { get; }
+    static ITypeHandle Null { get; } = NullTypeHandle.Instance;
+}


+    public bool IsNull => Address == 0;
+    public bool IsSynthetic => false;
+
+    public bool Equals(ITypeHandle? other)
+        => other is TargetTypeHandle t && Address == t.Address;
+    public bool Equals(TargetTypeHandle other) => Address == other.Address;


@@ -474,14 +474,14 @@ public TypeHandle GetTypeHandle(TargetPointer typeHandlePointer)
        // if we already validated this address, return a handle
        if (_methodTables.ContainsKey(typeHandlePointer))
        {
-            return new TypeHandle(typeHandlePointer);
+            return new TargetTypeHandle(typeHandlePointer);


+        // No loaded match found. For Ptr/Byref/SzArray/Array, synthesize a handle
+        // so signature-decoding contracts can treat unloaded constructed types uniformly.
+        if (corElementType is CorElementType.Ptr or CorElementType.Byref or CorElementType.SzArray or CorElementType.Array)
+        {
+            var synthetic = new SyntheticTypeHandle(corElementType, typeHandle, rank);
+            _ = _typeHandles.TryAdd(new TypeKey(typeHandle, corElementType, rank, typeArguments), synthetic);
+            return synthetic;
+        }


Rename the TypeHandle struct to ITypeHandle across the entire cDAC codebase in preparation for converting it to an interface that supports synthetic type handles for unloaded constructed types. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…peHandle Convert ITypeHandle from a readonly struct to an interface, enabling polymorphic type handles. Add NullTypeHandle (Abstractions) and TargetTypeHandle (Contracts) implementations. Replace ReadOnlySpan with ITypeHandle[] in public API signatures. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

rcj1 · 2026-06-24T14:52:10Z

ad-hoc side-channels

Am I missing something, or where are you removing said side channels with this abstraction? If this is a helper for a PR that you have in progress, what does it look like before and after?

max-charlamb · 2026-06-24T15:34:00Z

ad-hoc side-channels

Am I missing something, or where are you removing said side channels with this abstraction? If this is a helper for a PR that you have in progress, what does it look like before and after?

I needed extra data for implementing the ArgIterator: https://github.com/dotnet/runtime/pull/129769/changes#r3468318817

I believe adding synthetic typehandles aligns with our long-term goal to not have to load things in the runtime just for diagnostics.

rcj1 · 2026-06-24T15:35:55Z

ad-hoc side-channels

Am I missing something, or where are you removing said side channels with this abstraction? If this is a helper for a PR that you have in progress, what does it look like before and after?

I needed extra data for implementing the ArgIterator: https://github.com/dotnet/runtime/pull/129769/changes#r3468318817

I believe adding synthetic typehandles aligns with our long-term goal to not have to load things in the runtime just for diagnostics.

Could we accomplish this by adding (optional) fields and properties to the TypeHandle struct?

max-charlamb · 2026-06-24T15:56:50Z

ad-hoc side-channels

Am I missing something, or where are you removing said side channels with this abstraction? If this is a helper for a PR that you have in progress, what does it look like before and after?

I needed extra data for implementing the ArgIterator: https://github.com/dotnet/runtime/pull/129769/changes#r3468318817
I believe adding synthetic typehandles aligns with our long-term goal to not have to load things in the runtime just for diagnostics.

Could we accomplish this by adding (optional) fields and properties to the TypeHandle struct?

The TypeHandle was always meant to be an opaque handle, moving to an interface better accomplishes that and matches the pattern in other contracts.

runtime/src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IRuntimeTypeSystem.cs

Lines 11 to 23 in 440e6cb

    
           // an opaque handle to a type handle.  See IMetadata.GetMethodTableData 
        
           public readonly struct TypeHandle 
        
           { 
        
               // TODO-Layering: These members should be accessible only to contract implementations. 
        
               public TypeHandle(TargetPointer address) 
        
               { 
        
                   Address = address; 
        
               } 
        
               public TargetPointer Address { get; } 
        
               public bool IsNull => Address == 0; 
        
           }

Copilot

Pull request overview

Copilot reviewed 54 out of 54 changed files in this pull request and generated 6 comments.

+public sealed class NullTypeHandle : ITypeHandle
+{
+    public static readonly NullTypeHandle Instance = new();
+    private NullTypeHandle() { }


+    public bool Equals(ITypeHandle? other)
+        => other is TargetTypeHandle t && Address == t.Address;
+    public bool Equals(TargetTypeHandle other) => Address == other.Address;


+        if (corElementType is CorElementType.Ptr or CorElementType.Byref or CorElementType.SzArray or CorElementType.Array)
+        {
+            var synthetic = new SyntheticTypeHandle(corElementType, typeHandle, rank);
+            _ = _typeHandles.TryAdd(new TypeKey(typeHandle, corElementType, rank, typeArguments), synthetic);
+            return synthetic;


+        foreach (ITypeHandle arg in retAndArgTypes)
        {
            if (arg.Address == TargetPointer.Null)
                continue;


                // that we can return to SOS for pretty-printing.
-                // In the future we may want to return a TypeHandle instead of a MethodTable, and modify SOS to do more complete pretty-printing.
-                // DAC equivalent: src/coreclr/vm/typehandle.inl TypeHandle::GetMethodTable
+                // In the future we may want to return a ITypeHandle instead of a MethodTable, and modify SOS to do more complete pretty-printing.
+                // DAC equivalent: src/coreclr/vm/typehandle.inl ITypeHandle::GetMethodTable
                if (rtsContract.IsFunctionPointer(foundTypeHandle, out _, out _) || rtsContract.IsPointer(foundTypeHandle))


    // Shared core implementation for TypeHandleToExpandedTypeInfo and GetObjectExpandedTypeInfo.
-    private void TypeHandleToExpandedTypeInfoImpl(IRuntimeTypeSystem rts, AreValueTypesBoxed boxed, TypeHandle typeHandle, DebuggerIPCE_ExpandedTypeData* pTypeInfo)
+    private void ITypeHandleToExpandedTypeInfoImpl(IRuntimeTypeSystem rts, AreValueTypesBoxed boxed, ITypeHandle typeHandle, DebuggerIPCE_ExpandedTypeData* pTypeInfo)
    {


Add SyntheticTypeHandle (internal) for Ptr, Byref, SzArray, and Array types that the runtime has not loaded. GetConstructedType now returns a synthetic handle on miss instead of null, enabling signature-decoding contracts to treat all parameter types uniformly. Synthetic-aware branches added to 10 RTS methods: - GetSignatureCorElementType, HasTypeParam, GetTypeParam - IsPointer, IsArray, ContainsGenericVariables - GetModule, GetLoaderModule, IsLoaded - GetConstructedType (synthesis on miss) Also fixes GcSignatureTypeProvider to use IsNull instead of Address comparison, so synthetics get properly classified. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

rcj1 · 2026-06-24T20:24:21Z

The TypeHandle was always meant to be an opaque handle

Ok, sounds good

Copilot AI review requested due to automatic review settings June 24, 2026 14:31

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max-charlamb added area-Diagnostics-cdac and removed area-Diagnostics-coreclr labels Jun 24, 2026

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Max Charlamb and others added 2 commits June 24, 2026 10:42

max-charlamb force-pushed the dev/max-charlamb/rts-synthetic-typehandles branch from 1c85305 to 2050b89 Compare June 24, 2026 14:50

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max-charlamb force-pushed the dev/max-charlamb/rts-synthetic-typehandles branch from 2050b89 to 6522cf8 Compare June 24, 2026 16:03

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max-charlamb force-pushed the dev/max-charlamb/rts-synthetic-typehandles branch from 6522cf8 to 791163a Compare June 24, 2026 19:40

build-analysis Bot mentioned this pull request Jun 25, 2026

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[cdac] Extract ITypeHandle interface and add synthetic type handles#129800

[cdac] Extract ITypeHandle interface and add synthetic type handles#129800
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