Parens: only check for sensitive indentation when really needed

docs/release-notes/.FSharp.Compiler.Service/8.0.300.md

@@ -7,7 +7,7 @@
 * Code generated files with > 64K methods and generated symbols crash when loaded. Use infered sequence points for debugging. ([Issue #16399](https://github.com/dotnet/fsharp/issues/16399), [#PR 16514](https://github.com/dotnet/fsharp/pull/16514))
 * `nameof Module` expressions and patterns are processed to link files in `--test:GraphBasedChecking`. ([PR #16550](https://github.com/dotnet/fsharp/pull/16550), [PR #16743](https://github.com/dotnet/fsharp/pull/16743))
 * Graph Based Checking doesn't throw on invalid parsed input so it can be used for IDE scenarios ([PR #16575](https://github.com/dotnet/fsharp/pull/16575), [PR #16588](https://github.com/dotnet/fsharp/pull/16588), [PR #16643](https://github.com/dotnet/fsharp/pull/16643))
-* Various parenthesization API fixes. ([PR #16578](https://github.com/dotnet/fsharp/pull/16578), [PR #16666](https://github.com/dotnet/fsharp/pull/16666), [PR #16901](https://github.com/dotnet/fsharp/pull/16901))
+* Various parenthesization API fixes. ([PR #16578](https://github.com/dotnet/fsharp/pull/16578), [PR #16666](https://github.com/dotnet/fsharp/pull/16666), [PR #16901](https://github.com/dotnet/fsharp/pull/16901), [PR #16973](https://github.com/dotnet/fsharp/pull/16973))
 * Keep parens for problematic exprs (`if`, `match`, etc.) in `$"{(…):N0}"`, `$"{(…),-3}"`, etc. ([PR #16578](https://github.com/dotnet/fsharp/pull/16578))
 * Fix crash in DOTNET_SYSTEM_GLOBALIZATION_INVARIANT mode [#PR 16471](https://github.com/dotnet/fsharp/pull/16471))
 * Fix16572 - Fixed the preview feature enabling Is properties for union case did not work correctly with let .rec and .fsi files ([PR #16657](https://github.com/dotnet/fsharp/pull/16657))

src/Compiler/Service/SynExpr.fs

@@ -657,7 +657,41 @@ module SynExpr =
         //     return (
         //     x
         //     )
-        | _, SyntaxNode.SynExpr outer :: _ when containsSensitiveIndentation outer.Range.StartColumn expr.Range -> true
+        | _, SyntaxNode.SynExpr(SynExpr.YieldOrReturn _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.YieldOrReturnFrom _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.Assert _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.Lazy _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.App(argExpr = SynExpr.Paren(expr = Is expr)) as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.LetOrUse _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.LetOrUseBang _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.TryWith _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.TryFinally _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.For _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.ForEach _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.IfThenElse _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.New _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.Set(rhsExpr = SynExpr.Paren(expr = Is expr)) as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.DotIndexedSet(valueExpr = SynExpr.Paren(expr = Is expr)) as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.DotNamedIndexedPropertySet(rhsExpr = SynExpr.Paren(expr = Is expr)) as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.DotSet(rhsExpr = SynExpr.Paren(expr = Is expr)) as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.LibraryOnlyUnionCaseFieldSet(rhsExpr = SynExpr.Paren(expr = Is expr)) as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.LongIdentSet(expr = SynExpr.Paren(expr = Is expr)) as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.NamedIndexedPropertySet(expr2 = SynExpr.Paren(expr = Is expr)) as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.InferredUpcast _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.InferredDowncast _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.Match _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.MatchBang _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.While _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.WhileBang _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.Do _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.DoBang _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.Fixed _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.Record _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.AnonRecd _ as outer) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.InterpolatedString _ as outer) :: _ when
+            containsSensitiveIndentation outer.Range.StartColumn expr.Range
+            ->
+            true
 
         // Check for nested matches, e.g.,
         //

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

@@ -86,3 +86,37 @@ let shouldBeParenthesizedInContext (expected: Parenthesization list) src =
             | _ -> actual)
 
     CollectionAssert.AreEqual(expected, actual)
+
+[<Theory>]
+[<TestCase("9")>]
+[<TestCase("9 |> ignore")>]
+[<TestCase("
+let x =
+    do ()
+    9
+")>]
+[<TestCase("
+let x =
+    do ()
+    9 |> ignore
+")>]
+[<TestCase("
+for x in 1..10 do
+    9 |> ignore
+")>]
+let ``shouldBeParenthesizedInContext handles an unparenthesized hypothetical`` src =
+    let ast = getParseResults src
+
+    let getSourceLineStr =
+        let lines = src.ReplaceLineEndings().Split '\n'
+        Line.toZ >> Array.get lines
+
+    let expr, path =
+        (None, ast)
+        ||> ParsedInput.foldWhile (fun acc path node ->
+            match node with
+            | SyntaxNode.SynExpr (SynExpr.Const(SynConst.Int32 9, _)  as expr) -> Some(Some(expr, path))
+            | _ -> Some acc)
+        |> Option.defaultWith (fun () -> invalidOp "Expected a 9 but did not find one.")
+
+    Assert.False(SynExpr.shouldBeParenthesizedInContext getSourceLineStr path expr)