Fix #3939: Hide compiler-generated auto-property symbols from Symbols API

Fixes #3939

Mark the compiler-generated `v` setter parameter and backing field
identifiers in auto-property desugaring with synthetic ranges, so they
are excluded from GetAllUsesOfAllSymbolsInFile(). Previously these
internal symbols leaked through the API with empty EnclosingEntity
and misleading DisplayName/CompiledName values.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: T-Gro

src/Compiler/Checking/CheckDeclarations.fs

@@ -4418,7 +4418,7 @@ module TcDeclarations =
                 // Only the keep the field-targeted attributes
                 let attribs = attribs |> List.filter (fun a -> match a.Target with Some t when t.idText = "field" -> true | _ -> false)
                 let mLetPortion = synExpr.Range
-                let fldId = ident (CompilerGeneratedName id.idText, mLetPortion)
+                let fldId = ident (CompilerGeneratedName id.idText, mLetPortion.MakeSynthetic())
                 let headPat = SynPat.LongIdent (SynLongIdent([fldId], [], [None]), None, Some noInferredTypars, SynArgPats.Pats [], None, mLetPortion)
                 let retInfo = match tyOpt with None -> None | Some ty -> Some (None, SynReturnInfo((ty, SynInfo.unnamedRetVal), ty.Range))
                 let isMutable = 
@@ -4446,7 +4446,7 @@ module TcDeclarations =
                 let mMemberPortion = id.idRange
                 // Only the keep the non-field-targeted attributes
                 let attribs = attribs |> List.filter (fun a -> match a.Target with Some t when t.idText = "field" -> false | _ -> true)
-                let fldId = ident (CompilerGeneratedName id.idText, mMemberPortion)
+                let fldId = ident (CompilerGeneratedName id.idText, mMemberPortion.MakeSynthetic())
                 let headPatIds = if isStatic then [id] else [ident ("__", mMemberPortion);id]
                 let headPat = SynPat.LongIdent (SynLongIdent(headPatIds, [], List.replicate headPatIds.Length None), None, Some noInferredTypars, SynArgPats.Pats [], None, mMemberPortion)
                 let memberFlags = { memberFlags with GetterOrSetterIsCompilerGenerated = true }
@@ -4475,7 +4475,7 @@ module TcDeclarations =
                     | SynMemberKind.PropertySet 
                     | SynMemberKind.PropertyGetSet -> 
                         let setter = 
-                            let vId = ident("v", mMemberPortion)
+                            let vId = ident("v", mMemberPortion.MakeSynthetic())
                             let headPat = SynPat.LongIdent (SynLongIdent(headPatIds, [], List.replicate headPatIds.Length None), None, Some noInferredTypars, SynArgPats.Pats [mkSynPatVar None vId], None, mMemberPortion)
                             let rhsExpr = mkSynAssign (SynExpr.Ident fldId) (SynExpr.Ident vId)
                             let binding = mkSynBinding (xmlDoc, headPat) (setterAccess, false, false, mMemberPortion, DebugPointAtBinding.NoneAtInvisible, None, rhsExpr, rhsExpr.Range, [], [], Some memberFlagsForSet, SynBindingTrivia.Zero)

tests/FSharp.Compiler.Service.Tests/Symbols.fs

@@ -634,18 +634,23 @@ type Foo =
             Assert.True(setMfv.CompiledName.StartsWith("set_"))
         | _ -> failwith $"Expected three symbols, got %A{symbols}"
 
-    [<Fact(Skip = "Should not resolve the `v` name")>]
-    let ``AutoProperty with get, set has property symbol 02`` () =
-        let symbol = Checker.getSymbolUse """
+    // https://github.com/dotnet/fsharp/issues/3939
+    [<Fact>]
+    let ``AutoProperty with get, set does not expose compiler-generated v symbol`` () =
+        let _, checkResults = getParseAndCheckResults """
 namespace Foo
 
 type Foo =
-    member val AutoPropGetSet{caret} = 0 with get, set
+    member val AutoPropGetSet = 0 with get, set
 """
-        // The setter should have a symbol for the generated parameter `v`.
-        let setVMfv = symbol |> chooseMemberOrFunctionOrValue
-        if Option.isNone setVMfv then
-            failwith "No generated v symbol for the setter was found"
+        let allSymbols = checkResults.GetAllUsesOfAllSymbolsInFile()
+        let allMfvs = allSymbols |> Seq.choose (fun su -> match su.Symbol with :? FSharpMemberOrFunctionOrValue as mfv -> Some mfv | _ -> None) |> Seq.toList
+        // The compiler-generated `v` setter parameter should NOT appear in symbol uses
+        let vSymbols = allMfvs |> List.filter (fun mfv -> mfv.DisplayName = "v")
+        Assert.True(vSymbols.IsEmpty, $"Compiler-generated 'v' symbol should not be exposed via GetAllUsesOfAllSymbolsInFile, but found {vSymbols.Length} occurrences")
+        // The compiler-generated backing field should also not appear
+        let backingFieldSymbols = allMfvs |> List.filter (fun mfv -> mfv.DisplayName.Contains("@"))
+        Assert.True(backingFieldSymbols.IsEmpty, $"Compiler-generated backing field should not appear, but found: {backingFieldSymbols |> List.map (fun m -> m.DisplayName)}")
 
     [<Fact>]
     let ``Property symbol is resolved for property`` () =