Show C# and VB uses of an F# symbol in Find All References

[xperiandri]

Description

Find All References on an F# symbol never listed the call sites in C# or VB projects. Roslyn hands F# entirely to IFSharpFindUsagesService, and the F# search only ever visited F# documents: no C# project was in scope and Project.FindFSharpReferencesAsync filters by isFSharpSourceFile. This is not related to [<CompiledName>] — the compiled name is what the cross-language lookup already uses.

Change (Symbols.fs, FindUsagesService.fs): after the F# uses have been reported, FSharpSymbol.DocumentationCommentId — the symbol's XmlDocSig, the compiled form Roslyn resolves — is looked up with DocumentationCommentId.GetFirstSymbolForDeclarationId in the compilation of every C# or VB project whose metadata references include the built assembly of a project declaring the symbol (ProjectFiltering.getProjectsReferencingAssembly on OutputFilePath; Visual Studio keeps a C# → F# project reference as a PortableExecutableReference, see ProjectSystemProjectFactory.CanConvertMetadataReferenceToProjectReference). SymbolFinder.FindReferencesAsync is limited to that project's documents, the locations are reported as FSharpSourceReferenceItems under the F# definition item, and each file span is reported once across the target-framework instances of a consumer. The consumers are searched a few at a time (each search may build a compilation) and concurrently with the F# projects, since the id and the definition items are known before either search starts; the C# locations are reported after the F# uses, so the window keeps its order. Only Find All References does this; Find Implementations and Rename keep their F#-only scope, and symbols internal to their project or declared in external assemblies are skipped. Expected failures are null results (no compilation, unresolved id, unbuilt or stale assembly) and simply yield no C# results.

Known limits: a union case resolves to its nested type, so U.NewCase(…) calls are not found; conversion operators need ~ret in the id; active patterns have no compiled name Roslyn can parse.

Test infrastructure: the test host now serves language services for any language from the same export provider and imports Microsoft.CodeAnalysis.CSharp.Workspaces (added to eng/Packages.props at the Roslyn version the tests already use). RoslynTestHelpers.CompileToAssembly builds a SyntheticProject into its OutputFilename with the checker's options; AddCSharpProject adds a C# library referencing the framework of those options and the given assemblies — added after AdhocWorkspace.AddProject, which otherwise rewrites a reference to a project's output into a project reference, unlike Visual Studio. The first two commits are shared with #20462 and #20464.

Tests (FindReferencesFromCSharpTests): the C# compilation resolves the doc comment id of the F# function and SymbolFinder finds its call site; ProjectFiltering sees the C# project as a consumer of the F# assembly; DocumentationCommentId gives T:/M: ids for a module and a function and nothing for a local; Find All References on the F# declaration reports exactly the C# twice span; Find Implementations reports nothing.

Checklist

• Test cases added

• Performance benchmarks added in case of performance changes

• Release notes entry updated:

  Please make sure to add an entry with short succinct description of the change as well as link to this pull request to the respective release notes file, if applicable.

  Release notes files:

  • If anything under src/Compiler has been changed, please make sure to make an entry in docs/release-notes/.FSharp.Compiler.Service/<version>.md, where <version> is usually "highest" one, e.g. 42.8.200
  • If language feature was added (i.e. LanguageFeatures.fsi was changed), please add it to docs/release-notes/.Language/preview.md
  • If a change to FSharp.Core was made, please make sure to edit docs/release-notes/.FSharp.Core/<version>.md where version is "highest" one, e.g. 8.0.200.

  Information about the release notes entries format can be found in the documentation.
  Example:

  • More inlines for Result module. (PR #16106)
  • Correctly handle assembly imports with public key token of 0 length. (Issue #16359, PR #16363)
    *while! (Language suggestion #1038, PR #14238)

  If you believe that release notes are not necessary for this PR, please add NO_RELEASE_NOTES label to the pull request.

🤖 Generated with Claude Code

[github-actions]

❗ Release notes required

You can open this PR in browser to add release notes: open in github.dev

---

✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
`vsintegration/src`	docs/release-notes/.VisualStudio/18.vNext.md

[T-Gro]

🤖 🕵️ AI review — verify independently.

[T-Gro]

🤖 🕵️ [P2] Find All References reports the unrelated C# method and misses the F# call. With the F# reference aliased as FSLib, the editor search returns Other()'s Value span instead of Real()'s. Resolve the ID within the declaring assembly rather than taking the compilation-wide first match.

// F# library
namespace Collision
type Widget() =
    static member Value() = 1

// Reference the F# library with alias FSLib.
extern alias FSLib;
namespace Collision {
    public class Widget { public static int Value() => 2; }
}
class Consumer {
    int Real() => FSLib::Collision.Widget.Value(); // missed
    int Other() => Collision.Widget.Value();      // incorrectly reported
}

[T-Gro]

🤖🕵️ Enum IDs do not resolve: P:N.Color.Red returns null, but F:N.Color.Red resolves the field.

namespace N
type Color = Red = 0 | Blue = 1

Map enum-field IDs to F: and cover C#/VB callers.

[github-actions]

🔍 Tooling Safety Check — Affects-Build-Infra, Affects-Design-Time, Affects-Restore
Affects-Build-Infra: Changes production editor project structure and dependencies.
Affects-Design-Time: Adds cross-language Find All References integration.
Affects-Restore: Changes Roslyn package references.

Generated by PR Tooling Safety Check · gpt56 3.1M · ◷