Remove inconsistent UnmanagedCallersOnly delegate construction check

[Copilot]

Description

Removes the eager check in COMDelegate::GetDelegateCtor that throws NotSupportedException when attempting to create a delegate to a method with [UnmanagedCallersOnly]. This check is inconsistent with the runtime's policy of lazy validation for UnmanagedCallersOnly methods, which failfast only when actually invoked (e.g., via reflection or calli).

Changes:

• Removed HasUnmanagedCallersOnlyAttribute() check and exception throw from comdelegate.cpp:2796-2801
• Removed NegativeTest_ViaDelegate test that verified this exception behavior
• Removed unused IL methods GetDoubleDelegate and ManagedDoubleCallback from test infrastructure
• Removed unused resource string NotSupported_UnmanagedCallersOnlyTarget from Strings.resx

Behavior change:

// Before: throws NotSupportedException during delegate creation
var del = new Func<int, int>(MyUnmanagedCallersOnlyMethod);

// After: delegate creation succeeds, failfast occurs on invocation (consistent with reflection path)
var del = new Func<int, int>(MyUnmanagedCallersOnlyMethod);
del(42); // failfast here

Customer Impact

Minimal. The previous exception could be worked around, and invoking an UnmanagedCallersOnly method via delegate already triggers failfast at call time. This aligns the fast delegate construction path with the existing slow path behavior.

Regression

No. Removes a safety check introduced earlier but makes behavior consistent across all delegate construction paths.

Testing

CoreCLR and libraries builds verified. Remaining UnmanagedCallersOnly tests ensure failfast behavior on invocation still works correctly.

Risk

Low. Change removes defensive check but failfast protection remains at invocation time, consistent with other code paths.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Delegate fast path construction checks for [UnmanagedCallersOnly] attribute</issue_title>
<issue_description>This is inconsistent with other behavior around UnmanagedCallersOnly where misuse simply triggers a failfast. Consider removing this check.

Check that is inconsistent with policy.

runtime/src/coreclr/vm/comdelegate.cpp

Line 2796 in 6b4ee34

// Do not allow static methods with [UnmanagedCallersOnlyAttribute] to be a delegate target.

Commentary about this, #122656 (comment)

Test code that depends on the check

runtime/src/tests/Interop/UnmanagedCallersOnly/InvalidCallbacks.il

Line 140 in 6b4ee34

ldftn int32 InvalidCSharp.CallingUnmanagedCallersOnlyDirectly::ManagedDoubleCallback(int32)

</issue_description>

<agent_instructions>Please delete this check and the related test</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Delegate fast path construction checks for [UnmanagedCallersOnly] attribute #122890

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[jkotas]

/azp run runtime-coreclr outerloop

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[Copilot]

Pull request overview

This PR removes an inconsistent eager validation check that threw NotSupportedException when creating a delegate to a method marked with [UnmanagedCallersOnly]. This aligns delegate construction behavior with the runtime's lazy validation policy, where validation occurs at invocation time (during JIT compilation) rather than at delegate creation time. The failfast protection remains in place through ThrowIfInvalidUnmanagedCallersOnlyUsage called during JIT compilation.

Key changes:

• Removed eager HasUnmanagedCallersOnlyAttribute() check from delegate constructor path in CoreCLR
• Removed test that verified the now-removed exception behavior
• Cleaned up unused IL test methods and resource strings

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/coreclr/vm/comdelegate.cpp	Removed the eager UnmanagedCallersOnly attribute check from GetDelegateCtor that threw NotSupportedException during delegate construction
src/tests/Interop/UnmanagedCallersOnly/UnmanagedCallersOnlyTest.cs	Removed NegativeTest_ViaDelegate test that verified the removed NotSupportedException behavior
src/tests/Interop/UnmanagedCallersOnly/InvalidCallbacks.il	Removed unused IL methods ManagedDoubleCallback, DoubleImpl, and GetDoubleDelegate that were only used by the removed test
src/libraries/System.Private.CoreLib/src/Resources/Strings.resx	Removed unused resource string NotSupported_UnmanagedCallersOnlyTarget that was displayed in the removed exception

[jkotas]

/azp run runtime-coreclr outerloop

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[AaronRobinsonMSFT]

@jkotas @janvorli Looks like updates to the PAL missed updating the PAL tests.

[jkotas]

Looks like updates to the PAL missed updating the PAL tests.

Fixed by #122914

[jkotas]

/azp run runtime-coreclr outerloop

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Azure Pipelines successfully started running 1 pipeline(s).

[jkotas]

/azp run runtime-coreclr outerloop

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Azure Pipelines successfully started running 1 pipeline(s).

[jkotas]

/ba-g known issue #122345, build analysis is unable to match it for some reason