Ignore AssociatedSourceType on UnmanagedCallersOnly in CoreCLR

[Copilot]

CoreCLR rejected [UnmanagedCallersOnly] attributes containing the newer AssociatedSourceType named argument, throwing META_E_CA_UNKNOWN_ARGUMENT when setting up unmanaged callbacks. Assemblies valid for NativeAOT could therefore fail under CoreCLR.

• Runtime

  • Accept AssociatedSourceType in CoreCLR’s hand-written UnmanagedCallersOnlyAttribute parser.
  • Parse and ignore the value, matching the property’s NativeAOT-only semantics.

• Regression coverage

  • Add a CoreCLR interop test for an unmanaged function pointer call to a method annotated with:

    [UnmanagedCallersOnly(AssociatedSourceType = typeof(UnmanagedCallersOnlyBasicTest))]

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[MichalStrehovsky]

@copilot same problem with mono: * Assertion at /__w/1/s/src/mono/mono/metadata/marshal.c:3478, condition `is_ok (error)' not met, function:mono_marshal_set_callconv_from_unmanaged_callers_only_attribute, Binary format of the specified custom attribute was invalid. assembly: type:UnmanagedCallersOnlyBasicTest member:(null)

[Copilot]

@copilot undo changes in marshal.c that are not strictly necessary for the bugfix

Addressed in 7ea546a. The marshal.c diff against main now only keeps the image-context change needed for the bug fix and restores the unrelated assertion/warning/comment/style edits.

[MichalStrehovsky]

@AaronRobinsonMSFT @elinor-fung could one of you have a look please? This fixes #130245 that macios repo hit.

[Copilot]

Pull request overview

This PR updates CoreCLR’s UnmanagedCallersOnlyAttribute named-argument parsing to recognize the newer AssociatedSourceType named argument (and ignore it), preventing attribute parsing failures when consuming assemblies that include that argument. It also adds coverage and aligns Mono’s custom-attribute decoding to use the correct image when decoding the attribute blob.

Changes:

• CoreCLR: Extend the known named-argument set for UnmanagedCallersOnlyAttribute to include AssociatedSourceType so parsing doesn’t fail on unknown named arguments.
• Tests: Add an interop regression test using [UnmanagedCallersOnly(AssociatedSourceType = typeof(...))].
• Mono: Decode UnmanagedCallersOnlyAttribute named args using the method’s defining image rather than corlib, to avoid decode failures when named args reference types outside corlib.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/coreclr/vm/callconvbuilder.cpp	Adds AssociatedSourceType to the recognized named args for UnmanagedCallersOnlyAttribute parsing.
src/tests/Interop/UnmanagedCallersOnlyBasic/UnmanagedCallersOnlyBasicTest.cs	Adds a new UnmanagedCallersOnly method and a regression test for AssociatedSourceType.
src/mono/mono/metadata/marshal.c	Switches attribute-blob decode context to the method’s image to correctly resolve named-arg types.