Add ILLink coverage for unused virtual method annotations by Copilot · Pull Request #130640 · dotnet/runtime

Copilot · 2026-07-13T18:53:10Z

ILLink should validate virtual annotation mismatches only for retained implementations, avoiding IL2046/IL2092 warnings from unused code.

Coverage
- Completely unused implementation
- Type-only reference
- Used implementation that must warn
- Used interface with an unused sibling implementation

Co-authored-by: jtschuster <36744439+jtschuster@users.noreply.github.com>

Copilot

Pull request overview

Adds a new ILLink test case under Mono.Linker.Tests.Cases intended to ensure virtual/interface annotation mismatch validation only happens for implementations that are actually retained, avoiding IL2046/IL2092 noise from unused implementations.

Changes:

Introduces UnusedVirtualMethodAnnotations test coverage for four scenarios (fully unused impl, type-only reference, used impl must warn, used interface with unused sibling impl).
Uses ExpectedWarning to pin IL2046/IL2092 to the retained implementations while suppressing IL2026 at the call sites.

Comments suppressed due to low confidence (2)

src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/UnusedVirtualMethodAnnotations.cs:49

Same as UnusedImplementation: the Roslyn analyzers validate virtual/interface annotation mismatches independent of trimming reachability, so analyzer-only IL2046/IL2092 expectations are needed here to avoid unexpected warnings under the class-level [ExpectedNoWarnings].

        class TypeOnlyImplementation : ITypeOnly
        {
            public void Method(Type type) { }
        }

src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/UnusedVirtualMethodAnnotations.cs:82

Because [ExpectedNoWarnings] is applied at the test-case level, any analyzer-emitted mismatches for unused sibling implementations will be treated as unexpected. Add analyzer-only IL2046/IL2092 expectations for this unused implementation so the test can still validate the trimmer-specific reachability behavior without breaking analyzer runs.

        class UnusedImplementationOfPartiallyUsedInterface : IPartiallyUsed
        {
            public void Method(Type type) { }
        }

…unused implementations Co-authored-by: jtschuster <36744439+jtschuster@users.noreply.github.com>

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jtschuster · 2026-07-24T20:31:10Z

+            [UnexpectedWarning("IL2046", Tool.Analyzer, "https://github.com/dotnet/runtime/pull/130640")]
+            [UnexpectedWarning("IL2092", Tool.Analyzer, "https://github.com/dotnet/runtime/pull/130640")]


@copilot Update the issue/reason string for the UnexpectedWarnings to say "Analyzer does not track reachability"

Updated all 6 UnexpectedWarning reason strings to "Analyzer does not track reachability" in the latest commit.

…eachability' Co-authored-by: jtschuster <36744439+jtschuster@users.noreply.github.com>

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sbomer · 2026-07-27T15:49:15Z

+
+        class UnusedImplementation : IUnused
+        {
+            [UnexpectedWarning("IL2046", Tool.Analyzer, "Analyzer does not track reachability")]


@copilot this should be ExpectedWarning for the analyzer warnings

Changed all three sites from UnexpectedWarning to ExpectedWarning with Tool.Analyzer.

sbomer · 2026-07-27T15:50:55Z

+            public void Method(Type type) { }
+        }
+
+        [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods)]


Do the interfaces need DAM to repro this issue? I would leave this out (or at least add a simpler test without DAM on the interface).

sbomer · 2026-07-27T15:53:29Z

+
+        class UnusedImplementationOfPartiallyUsedInterface : IPartiallyUsed
+        {
+            [UnexpectedWarning("IL2046", Tool.Analyzer, "Analyzer does not track reachability")]


The testcase should demonstrate a scenario where ILLink produces unexpected warnings too

…IL2092 warnings Co-authored-by: sbomer <787361+sbomer@users.noreply.github.com>

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Initial plan

b6609f2

Copilot AI assigned Copilot and jtschuster Jul 13, 2026

Copilot AI requested review from Copilot and removed request for Copilot July 13, 2026 18:53

github-project-automation Bot added this to AppModel Jul 13, 2026

Copilot started work on behalf of jtschuster July 13, 2026 18:53 View session

Copilot AI linked an issue Jul 13, 2026 that may be closed by this pull request

ILLink warns for virtual method annotations on unused code #98870

Open

github-actions Bot added the area-Infrastructure label Jul 13, 2026

github-project-automation Bot added this to Runtime Infra Jul 13, 2026

Add ILLink unused annotation regression coverage

860048e

Co-authored-by: jtschuster <36744439+jtschuster@users.noreply.github.com>

Copilot AI requested review from Copilot and removed request for Copilot July 13, 2026 19:44

dotnet-policy-service Bot added the linkable-framework Issues associated with delivering a linker friendly framework label Jul 13, 2026

Copilot AI changed the title ~~[WIP] Fix ILLink warnings for virtual method annotations on unused code~~ Add ILLink coverage for unused virtual method annotations Jul 13, 2026

Copilot AI requested a review from jtschuster July 13, 2026 19:46

Copilot finished work on behalf of jtschuster July 13, 2026 19:46

jtschuster approved these changes Jul 13, 2026

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build-analysis Bot mentioned this pull request Jul 14, 2026

Wasm.Build.NativeRebuild.Tests.ReferenceNewAssemblyRebuildTest.ReferenceNewAssembly failure: Expected changed file: driver-gen.c #130540

Closed

sbomer reviewed Jul 24, 2026

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Comment thread src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/UnusedVirtualMethodAnnotations.cs

Merge branch 'main' into copilot/fix-ilink-warnings-unused-code

6c3c3b7

Copilot AI review requested due to automatic review settings July 24, 2026 19:29

Copilot started reviewing on behalf of jtschuster July 24, 2026 19:30 View session

Copilot AI reviewed Jul 24, 2026

View reviewed changes

Comment thread src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/UnusedVirtualMethodAnnotations.cs

Copilot started work on behalf of jtschuster July 24, 2026 20:20 View session

Add UnexpectedWarning annotations for analyzer-only IL2046/IL2092 on …

c60ab0a

…unused implementations Co-authored-by: jtschuster <36744439+jtschuster@users.noreply.github.com>

Copilot AI review requested due to automatic review settings July 24, 2026 20:25

Copilot AI reviewed Jul 24, 2026

Copilot finished work on behalf of jtschuster July 24, 2026 20:25

Copilot AI requested a review from jtschuster July 24, 2026 20:25

jtschuster reviewed Jul 24, 2026

View reviewed changes

Copilot started work on behalf of jtschuster July 24, 2026 20:34 View session

Update UnexpectedWarning reason strings to 'Analyzer does not track r…

51884f2

…eachability' Co-authored-by: jtschuster <36744439+jtschuster@users.noreply.github.com>

Copilot AI review requested due to automatic review settings July 24, 2026 20:35

Copilot AI reviewed Jul 24, 2026

Copilot finished work on behalf of jtschuster July 24, 2026 20:35

Copilot AI requested a review from jtschuster July 24, 2026 20:35

sbomer reviewed Jul 27, 2026

View reviewed changes

Copilot started work on behalf of sbomer July 27, 2026 15:55 View session

Change UnexpectedWarning to ExpectedWarning for analyzer-only IL2046/…

5bc07dc

…IL2092 warnings Co-authored-by: sbomer <787361+sbomer@users.noreply.github.com>

Copilot AI review requested due to automatic review settings July 27, 2026 15:59

Copilot AI reviewed Jul 27, 2026

Copilot finished work on behalf of sbomer July 27, 2026 15:59

Copilot AI requested a review from sbomer July 27, 2026 15:59

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Add ILLink coverage for unused virtual method annotations - #130640

Add ILLink coverage for unused virtual method annotations#130640
jtschuster with Copilot wants to merge 6 commits into
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copilot/fix-ilink-warnings-unused-code

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		[UnexpectedWarning("IL2046", Tool.Analyzer, "https://github.com/dotnet/runtime/pull/130640")]
		[UnexpectedWarning("IL2092", Tool.Analyzer, "https://github.com/dotnet/runtime/pull/130640")]

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Copilot AI commented Jul 13, 2026 •

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