Report a hand-written __ self identifier to editor tooling

docs/release-notes/.FSharp.Compiler.Service/11.0.100.md

@@ -95,6 +95,7 @@
 * Fix nativeptr in interfaces leads to TypeLoadException. (Issue [#14508](https://github.com/dotnet/fsharp/issues/14508), [PR #19338](https://github.com/dotnet/fsharp/pull/19338))
 * Fix box instruction for literal upcasts. (Issue [#18319](https://github.com/dotnet/fsharp/issues/18319), [PR #19338](https://github.com/dotnet/fsharp/pull/19338))
 * Fix Decimal Literal causes InvalidProgramException in Debug builds. (Issue [#18956](https://github.com/dotnet/fsharp/issues/18956), [PR #19338](https://github.com/dotnet/fsharp/pull/19338))
+* Report a self identifier named `__` (as in `member __.M()`) to editor tooling. Only its uses were reported, not its declaration, so Rename rewrote the body of such a member and left `member __.` behind. The self identifier synthesized by the auto-property desugaring, which the name check was really aimed at, is now suppressed by its synthetic range instead. ([Issue #20566](https://github.com/dotnet/fsharp/issues/20566), [PR #20598](https://github.com/dotnet/fsharp/pull/20598))
 * Fix `AttributeUsage.AllowMultiple` not being inherited for attributes subclassed in C#. ([Issue #17107](https://github.com/dotnet/fsharp/issues/17107), [PR #19315](https://github.com/dotnet/fsharp/pull/19315))
 * Fix signature generation: recursive module `do` binding leaking compiler-generated val. ([Issue #13832](https://github.com/dotnet/fsharp/issues/13832), [PR #19586](https://github.com/dotnet/fsharp/pull/19586))
 * Fix signature generation: literal values in attribute arguments now preserve literal identifier name. ([Issue #13810](https://github.com/dotnet/fsharp/issues/13810), [PR #19586](https://github.com/dotnet/fsharp/pull/19586))

src/Compiler/Checking/CheckDeclarations.fs

@@ -4841,7 +4841,7 @@ module TcDeclarations =
                 // 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.MakeSynthetic())
-                let headPatIds = if isStatic then [id] else [ident ("__", mMemberPortion);id]
+                let headPatIds = if isStatic then [id] else [ident ("__", mMemberPortion.MakeSynthetic());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 }
                 let memberFlagsForSet = { memberFlagsForSet with GetterOrSetterIsCompilerGenerated = true }

src/Compiler/Checking/Expressions/CheckExpressions.fs

@@ -1451,13 +1451,9 @@ let MakeAndPublishVal (cenv: cenv) env (altActualParent, inSig, declKind, valRec
 
     let shouldNotifySink (vspec: Val) =
         match vspec.MemberInfo with
-        // `this` reference named `__`. It's either:
-        // * generated by compiler for auto properties or
-        // * provided by source code (i.e. `member _.Method = ...`)
-        // We don't notify sink about it to prevent generating `FSharpSymbol` for it and appearing in completion list.
-        | None when
-            vspec.IsBaseVal ||
-            vspec.IsMemberThisVal && vspec.LogicalName = "__" -> false
+        // visualfsharp#3699: the range of `base` spans the whole `inherit` expression, so reporting it
+        // makes its environment the most deeply nested one at the constructor arguments, shadowing theirs.
+        | None when vspec.IsBaseVal -> false
         | _ -> true
 
     match cenv.tcSink.CurrentSink with

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

@@ -689,6 +689,50 @@ type Foo =
         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)}")
 
+    let private selfIdentifierRanges (checkResults: FSharpCheckFileResults) =
+        checkResults.GetAllUsesOfAllSymbolsInFile()
+        |> Seq.filter (fun su ->
+            match su.Symbol with
+            | :? FSharpMemberOrFunctionOrValue as mfv -> mfv.IsMemberThisValue
+            | _ -> false)
+        |> Seq.map _.Range
+        |> Seq.sortBy (fun m -> m.StartLine, m.StartColumn)
+        |> Seq.toList
+
+    [<Theory>]
+    [<InlineData "this">]
+    [<InlineData "self">]
+    [<InlineData "__">]
+    let ``Self identifier is reported at its declaration and at its uses`` (selfId: string) =
+        let _, checkResults = getParseAndCheckResults $"""
+namespace Foo
+
+type Foo() =
+    member {selfId}.M() = {selfId}.N()
+    member {selfId}.N() = 1
+"""
+        let n = selfId.Length
+
+        match selfIdentifierRanges checkResults with
+        | [ mDeclInM; mUseInM; mDeclInN ] ->
+            assertRange (5, 11) (5, 11 + n) mDeclInM
+            assertRange (5, 18 + n) (5, 18 + 2 * n) mUseInM
+            assertRange (6, 11) (6, 11 + n) mDeclInN
+        | ranges -> failwith $"Expected three self identifier symbol uses, got %A{ranges}"
+
+    [<Fact>]
+    let ``AutoProperty does not expose its compiler-generated self identifier`` () =
+        let _, checkResults = getParseAndCheckResults """
+namespace Foo
+
+type Foo =
+    member val AutoPropGetSet = 0 with get, set
+"""
+        // The synthesized `__` sits on the property name's range, so reporting it would shadow the property
+        match selfIdentifierRanges checkResults with
+        | [] -> ()
+        | ranges -> failwith $"Expected no self identifier symbol uses, got %A{ranges}"
+
     [<Fact>]
     let ``Property symbol is resolved for property`` () =
         let symbols = Checker.getSymbolUses """