More misc parens fixes

docs/release-notes/.FSharp.Compiler.Service/9.0.300.md

@@ -13,6 +13,7 @@
 * Fix NRE when accessing nullable fields of types within their equals/hash/compare methods ([PR #18296](https://github.com/dotnet/fsharp/pull/18296))
 * Fix nullness warning for overrides of generic code with nullable type instance ([Issue #17988](https://github.com/dotnet/fsharp/issues/17988), [PR #18337](https://github.com/dotnet/fsharp/pull/18337))
 * Unsafe downcast from `obj` to generic `T` no longer requires `not null` constraint on `T`([Issue #18275](https://github.com/dotnet/fsharp/issues/18275), [PR #18343](https://github.com/dotnet/fsharp/pull/18343))
+* Miscellanous parentheses analyzer fixes. ([PR #18350](https://github.com/dotnet/fsharp/pull/18350))
 
 ### Added
 * Added missing type constraints in FCS. ([PR #18241](https://github.com/dotnet/fsharp/pull/18241))

src/Compiler/Service/SynExpr.fs

@@ -343,6 +343,7 @@ module SynExpr =
         | PrefixApp prec -> ValueSome(prec, Non)
         | InfixApp(prec, side) -> ValueSome(prec, side)
         | SynExpr.App(argExpr = SynExpr.ComputationExpr _) -> ValueSome(UnaryPrefix, Left)
+        | SynExpr.App(argExpr = SynExpr.Paren(expr = SynExpr.App _ & Is inner)) -> ValueSome(Apply, Right)
         | SynExpr.App(funcExpr = SynExpr.Paren(expr = SynExpr.App _)) -> ValueSome(Apply, Left)
         | SynExpr.App(flag = ExprAtomicFlag.Atomic) -> ValueSome(Dot, Non)
         | SynExpr.App _ -> ValueSome(Apply, Non)
@@ -396,6 +397,7 @@ module SynExpr =
         | SynExpr.DotIndexedSet _
         | SynExpr.DotNamedIndexedPropertySet _
         | SynExpr.DotSet _ -> ValueSome Set
+        | SynExpr.TypeTest _ -> ValueSome TypeTest
         | _ -> ValueNone
 
     module Dangling =
@@ -540,7 +542,7 @@ module SynExpr =
 
                         if i >= 0 && i < offsidesCol then
                             let slice = line.AsSpan(i, min (offsidesCol - i) (line.Length - i))
-                            let j = slice.IndexOfAnyExcept("*/%-+:^@><=!|0$.?".AsSpan())
+                            let j = slice.IndexOfAnyExcept("*/%-+:^@><=!|$.?".AsSpan())
 
                             let lo = i + (if j >= 0 && slice[j] = ' ' then j else 0)
 
@@ -845,22 +847,6 @@ module SynExpr =
         // precedence than regular function application.
         | _, SyntaxNode.SynExpr(SynExpr.App _) :: SyntaxNode.SynExpr(PrefixApp High) :: _ -> true
 
-        // Parens are never required around suffixed or infixed numeric literals, e.g.,
-        //
-        //     (1l).ToString()
-        //     (1uy).ToString()
-        //     (0b1).ToString()
-        //     (1e10).ToString()
-        //     (1.0).ToString()
-        | DotSafeNumericLiteral, _ -> false
-
-        // Parens are required around bare decimal ints or doubles ending
-        // in dots when being dotted into, e.g.,
-        //
-        //     (1).ToString()
-        //     (1.).ToString()
-        | SynExpr.Const(constant = SynConst.Int32 _ | SynConst.Double _), SyntaxNode.SynExpr(SynExpr.DotGet _) :: _ -> true
-
         // Parens are required around join conditions:
         //
         //     join … on (… = …)
@@ -907,6 +893,22 @@ module SynExpr =
             ->
             true
 
+        // Parens are never required around suffixed or infixed numeric literals, e.g.,
+        //
+        //     (1l).ToString()
+        //     (1uy).ToString()
+        //     (0b1).ToString()
+        //     (1e10).ToString()
+        //     (1.0).ToString()
+        | DotSafeNumericLiteral, _ -> false
+
+        // Parens are required around bare decimal ints or doubles ending
+        // in dots when being dotted into, e.g.,
+        //
+        //     (1).ToString()
+        //     (1.).ToString()
+        | SynExpr.Const(constant = SynConst.Int32 _ | SynConst.Double _), SyntaxNode.SynExpr(SynExpr.DotGet _) :: _ -> true
+
         // The :: operator is parsed differently from other symbolic infix operators,
         // so we need to give it special treatment.
 
@@ -952,6 +954,7 @@ module SynExpr =
                 let rec loop =
                     function
                     | [] -> false
+                    | SynMatchClause(whenExpr = Some(SynExpr.Paren(expr = Dangling.ArrowSensitive _ & Is inner))) :: _ -> true
                     | SynMatchClause(trivia = trivia) :: clauses ->
                         trivia.BarRange |> Option.exists (problematic matchOrTryRange)
                         || trivia.ArrowRange |> Option.exists (problematic matchOrTryRange)
@@ -1148,6 +1151,7 @@ module SynExpr =
                                | _, MulDivMod(Mod, _)
                                | _, AddSub(Sub, _) -> true
                                | Relational _, Relational _ -> true
+                               | Apply, Apply -> true
                                | _ -> false
 
                     | c -> c > 0

vsintegration/tests/FSharp.Editor.Tests/CodeFixes/RemoveUnnecessaryParenthesesTests.fs

@@ -398,7 +398,7 @@ let _ =
             ",
             "
             match () with
-            | () when box x :? int
+            | () when (box x :? int)
                 -> ()
             | _ -> ()
             "
@@ -1830,6 +1830,8 @@ in x
                 f ((+) x y) z
                 "
 
+                "(Gen.map f << Gen.map g) (Gen.constant x)", "(Gen.map f << Gen.map g) (Gen.constant x)"
+
                 // TypeApp
                 "id (id<int>)", "id id<int>"
 
@@ -1890,6 +1892,7 @@ in x
                 """(id "x").Length""", """(id "x").Length"""
                 """(3L.ToString("x")).Length""", """(3L.ToString "x").Length"""
                 "~~TypedResults.Ok<string>(maybe.Value)", "~~TypedResults.Ok<string>(maybe.Value)"
+                "bg.lighten(0.2).hexa ()", "bg.lighten(0.2).hexa ()"
 
                 // DotLambda
                 "[{| A = x |}] |> List.map (_.A)", "[{| A = x |}] |> List.map _.A"