`FindBackgroundReferencesInFile` on Active Pattern Case finds all other Cases too

[Booksbaum]

"Find All References" in Visual Studio (and Ionide) on an Active Pattern Case sometimes not just finds current case, but all other cases too:

-> "Find All References" on Even -- but finds Odd too

But this isn't always the case:

Here VS correctly finds just Even occurrences.

Difference: First one is a fs file inside a Project, second one is a Script file (even one not saved on disk)

Also an issue for Renaming:
Instead of just renaming Even, Odd gets renamed at same time (to same name)

---

Side Note:
Images above show a presentation error too:
let |Even|Odd|(|Even|Odd|) v = instead of let (|Even|Odd|) v =
Link location (click on result) works fine

---

The difference in behaviour can be explained by looking at FindUsagesService:

fsharp/vsintegration/src/FSharp.Editor/Navigation/FindUsagesService.fs

Lines 103 to 126 in d13df68

	match symbolUse.GetDeclarationLocation document with
	| Some SymbolDeclarationLocation.CurrentDocument ->
	let symbolUses = checkFileResults.GetUsesOfSymbolInFile(symbolUse.Symbol)
	for symbolUse in symbolUses do
	match RoslynHelpers.TryFSharpRangeToTextSpan(sourceText, symbolUse.Range) with
	| Some textSpan ->
	do! onFound document textSpan symbolUse.Range |> liftAsync
	| _ ->
	()
	| scope ->
	let projectsToCheck =
	match scope with
	| Some (SymbolDeclarationLocation.Projects (declProjects, false)) ->
	[ for declProject in declProjects do
	yield declProject
	yield! declProject.GetDependentProjects() ]
	|> List.distinct
	| Some (SymbolDeclarationLocation.Projects (declProjects, true)) -> declProjects
	// The symbol is declared in .NET framework, an external assembly or in a C# project within the solution.
	// In order to find all its usages we have to check all F# projects.
	| _ -> Seq.toList document.Project.Solution.Projects
	let! _ = SymbolHelpers.getSymbolUsesInProjects (symbolUse.Symbol, projectsToCheck, onFound) |> liftAsync
	()

-> different lookup methods depending on local to current doc or public:

• current doc: checkFileResults.GetUsesOfSymbolInFile
• otherwise: SymbolHelpers.getSymbolUsesInProjects which boils down to checker.FindBackgroundReferencesInFile (actual call)

(Ionide uses same functions for same scopes -> explains same behavior as in VS)

So it seems FSharpCheckFileResults.GetUsesOfSymbolInFile and FSharpChecker.FindBackgroundReferencesInFile return different results for Active Pattern Cases -- with FSharpChecker.FindBackgroundReferencesInFile being wrong

Repro steps

(Test Script)

Tests find usages on last Even in:

let (|Even|Odd|) v = 
  if v % 2 = 0 then Even else Odd
match 2 with
| Even -> ()
| Odd -> ()

git clone https://gist.github.com/275f6af13410812ba97a0647b9d2408f.git test

cd test

dotnet fsi --nologo --exec .\Test.fsx

Output:

# Project
* uses: Ok
* refs: Error
    Expected 3, but was 6: [|...\src\Project.fs (2,6--2,10);
  ...\src\Project.fs (2,11--2,14);
  ...\src\Project.fs (3,20--3,24);
  ...\src\Project.fs (3,30--3,33);
  ...\src\Project.fs (5,2--5,6);
  ...\src\Project.fs (6,2--6,5)|]
# Script
* uses: Ok
* refs: Error
    Expected 3, but was 6: [|...\src\Script.fsx (2,6--2,10);
  ...\src\Script.fsx (2,11--2,14);
  ...\src\Script.fsx (3,20--3,24);
  ...\src\Script.fsx (3,30--3,33);
  ...\src\Script.fsx (5,2--5,6);
  ...\src\Script.fsx (6,2--6,5)|]
# InMemory
* uses: Ok
* refs: Error
    Exception: System.AggregateException: [...]
    // Expected, because no existing file

• uses: GetUsesOfSymbolInFile
• refs: FindBackgroundReferencesInFile
• Ok when 3 occurrences found, otherwise Error

-> tests prove: Different results for GetUsesOfSymbolInFile and FindBackgroundReferencesInFile and wrong results for FindBackgroundReferencesInFile

Expected behavior

FindBackgroundReferencesInFile should only return locations of search Active Pattern Case.

Actual behavior

FindBackgroundReferencesInFile returns locations of other Cases too

Known workarounds

Use GetUsesOfSymbolInFile instead of FindBackgroundReferencesInFile

Related information

• Win 11 x64
• dotnet --version: 6.0.402, 7.0.100-rc.2.22477.23
• FCS: 41.0.5, 41.0.6, 42.7.100-preview.22473.1
• Microsoft Visual Studio Community 2022 (64-bit) - Current Version 17.3.6