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Parens: more fixes (#16901)
* Fix a few more paren corner cases * Match-like exprs in `if` exprs, `while` exprs, and `for` exprs. Also `let` exprs. * Nested, dangling `as` patterns. * Outlaw `match` exprs (where the first `|` is leftward of the `m` in `match) * Single-line comments (`//`, `///`). Multiline comments (`(*…*)`) would be… rather more difficult to handle. * Double-parenthesized tuples in method applications, since we can't tell purely syntactically whether the tuple might be the first parameter of a method whose next parameter is an implied outref parameter: `x.TryGetValue ((y, z))` i.e., `x.TryGetValue ((y, z), &value)` * Multiline tuple patterns in `let`-bindings. These need parens if the bound expression starts on the same column. * Handle typed pats in getters & setters * Double parens oddities * Sometimes we can't tell just by looking at the untyped AST whether we need parens, since their necessity may be dictated by type information located elsewhere. Compare, e.g., #16254, which probably has a similar underlying cause. * Keep parens for parenzed app preceded by prefix op * Keep parens around tuple in interp string * More nested match fun * No space when expr would reparse as prefix op * No space when expr would reparse as prefix op * No space when expr would reparse as prefix op * Update release notes * Remove unfinished multiline comment stuff * Keep parens around dot-get that would be adjacent * E.g., removing parens in place from ```fsharp Debug.Assert((xT.DeclaringType :?> ProvidedTypeDefinition).BelongsToTargetModel) ``` would result in the the argument to `Assert` becoming `(xT.DeclaringType :?> ProvidedTypeDefinition)`. The `.BelongsToTargetModel` would then be parsed as a get on the return value of _that_ call. * Fantomas
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‎docs/release-notes/.FSharp.Compiler.Service/8.0.300.md‎

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Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
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* 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))
77
* `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))
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* 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))
9-
* Various parenthesization API fixes. ([PR #16578](https://github.com/dotnet/fsharp/pull/16578), [PR #16666](https://github.com/dotnet/fsharp/pull/16666))
9+
* 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))
1010
* Keep parens for problematic exprs (`if`, `match`, etc.) in `$"{(…):N0}"`, `$"{(…),-3}"`, etc. ([PR #16578](https://github.com/dotnet/fsharp/pull/16578))
1111
* Fix crash in DOTNET_SYSTEM_GLOBALIZATION_INVARIANT mode [#PR 16471](https://github.com/dotnet/fsharp/pull/16471))
1212
* 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))

‎docs/release-notes/.VisualStudio/17.10.md‎

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@@ -1,7 +1,7 @@
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### Fixed
22

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* Show signature help mid-pipeline in more scenarios. ([PR #16462](https://github.com/dotnet/fsharp/pull/16462))
4-
* Various unneeded parentheses code fix improvements. ([PR #16578](https://github.com/dotnet/fsharp/pull/16578), [PR #16666](https://github.com/dotnet/fsharp/pull/16666), [PR #16789](https://github.com/dotnet/fsharp/pull/16789))
4+
* Various unneeded parentheses code fix improvements. ([PR #16578](https://github.com/dotnet/fsharp/pull/16578), [PR #16666](https://github.com/dotnet/fsharp/pull/16666), [PR #16789](https://github.com/dotnet/fsharp/pull/16789), [PR #16901](https://github.com/dotnet/fsharp/pull/16901))
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### Changed
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‎src/Compiler/Service/SynExpr.fs‎

Lines changed: 66 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -344,6 +344,7 @@ module SynExpr =
344344
| InfixApp(prec, side) -> ValueSome(prec, side)
345345
| SynExpr.App(argExpr = SynExpr.ComputationExpr _) -> ValueSome(UnaryPrefix, Left)
346346
| SynExpr.App(funcExpr = SynExpr.Paren(expr = SynExpr.App _)) -> ValueSome(Apply, Left)
347+
| SynExpr.App(flag = ExprAtomicFlag.Atomic) -> ValueSome(Dot, Non)
347348
| SynExpr.App _ -> ValueSome(Apply, Non)
348349
| SynExpr.DotSet(targetExpr = SynExpr.Paren(expr = Is inner)) -> ValueSome(Dot, Left)
349350
| SynExpr.DotSet(rhsExpr = SynExpr.Paren(expr = Is inner)) -> ValueSome(Set, Right)
@@ -437,6 +438,14 @@ module SynExpr =
437438
| SynExpr.IfThenElse _ as expr -> Some expr
438439
| _ -> None)
439440

441+
/// Matches a dangling let or use construct.
442+
[<return: Struct>]
443+
let (|LetOrUse|_|) =
444+
dangling (function
445+
| SynExpr.LetOrUse _
446+
| SynExpr.LetOrUseBang _ as expr -> Some expr
447+
| _ -> None)
448+
440449
/// Matches a dangling sequential expression.
441450
[<return: Struct>]
442451
let (|Sequential|_|) =
@@ -610,13 +619,26 @@ module SynExpr =
610619
//
611620
// o.M((x = y))
612621
// o.N((x = y), z)
622+
//
623+
// Likewise, double parens must stay around a tuple, since we don't know whether
624+
// the method being invoked might have a signature like
625+
//
626+
// val TryGetValue : 'Key * outref<'Value> -> bool
627+
//
628+
// where 'Key is 'a * 'b, in which case the double parens are required.
613629
| SynExpr.Paren(expr = InfixApp(Relational(OriginalNotation "="), _)),
614-
SyntaxNode.SynExpr(SynExpr.App(funcExpr = SynExpr.LongIdent _)) :: _
630+
SyntaxNode.SynExpr(SynExpr.App(funcExpr = SynExpr.LongIdent _ | SynExpr.DotGet _ | SynExpr.Ident _)) :: _
615631
| InfixApp(Relational(OriginalNotation "="), _),
616-
SyntaxNode.SynExpr(SynExpr.Paren _) :: SyntaxNode.SynExpr(SynExpr.App(funcExpr = SynExpr.LongIdent _)) :: _
632+
SyntaxNode.SynExpr(SynExpr.Paren _) :: SyntaxNode.SynExpr(SynExpr.App(
633+
funcExpr = SynExpr.LongIdent _ | SynExpr.DotGet _ | SynExpr.Ident _)) :: _
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| InfixApp(Relational(OriginalNotation "="), _),
618635
SyntaxNode.SynExpr(SynExpr.Tuple(isStruct = false)) :: SyntaxNode.SynExpr(SynExpr.Paren _) :: SyntaxNode.SynExpr(SynExpr.App(
619-
funcExpr = SynExpr.LongIdent _)) :: _ -> true
636+
funcExpr = SynExpr.LongIdent _ | SynExpr.DotGet _ | SynExpr.Ident _)) :: _
637+
| SynExpr.Paren(expr = SynExpr.Tuple(isStruct = false)),
638+
SyntaxNode.SynExpr(SynExpr.App(funcExpr = SynExpr.LongIdent _ | SynExpr.DotGet _ | SynExpr.Ident _)) :: _
639+
| SynExpr.Tuple(isStruct = false),
640+
SyntaxNode.SynExpr(SynExpr.Paren _) :: SyntaxNode.SynExpr(SynExpr.App(
641+
funcExpr = SynExpr.LongIdent _ | SynExpr.DotGet _ | SynExpr.Ident _)) :: _ -> true
620642

621643
// Already parenthesized.
622644
| _, SyntaxNode.SynExpr(SynExpr.Paren _) :: _ -> false
@@ -676,6 +698,15 @@ module SynExpr =
676698
SyntaxNode.SynExpr(SynExpr.App _) :: SyntaxNode.SynExpr(HighPrecedenceApp | SynExpr.Assert _ | SynExpr.InferredUpcast _ | SynExpr.InferredDowncast _) :: _ ->
677699
true
678700

701+
// Parens must be kept in a scenario like
702+
//
703+
// !x.M(y)
704+
// ~~~x.M(y)
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//
706+
// since prefix ! or ~~~ (with no space) have higher
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// precedence than regular function application.
708+
| _, SyntaxNode.SynExpr(SynExpr.App _) :: SyntaxNode.SynExpr(PrefixApp High) :: _ -> true
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679710
// Parens are never required around suffixed or infixed numeric literals, e.g.,
680711
//
681712
// (1l).ToString()
@@ -794,13 +825,17 @@ module SynExpr =
794825
match outer, inner with
795826
| ConfusableWithTypeApp, _ -> true
796827

797-
| SynExpr.IfThenElse _, Dangling.Sequential _ -> true
828+
| SynExpr.IfThenElse(trivia = trivia), Dangling.LetOrUse letOrUse ->
829+
Position.posLt letOrUse.Range.Start trivia.ThenKeyword.Start
798830

799-
| SynExpr.IfThenElse(trivia = trivia), Dangling.IfThen ifThenElse when
800-
problematic ifThenElse.Range trivia.ThenKeyword
801-
|| trivia.ElseKeyword |> Option.exists (problematic ifThenElse.Range)
802-
->
803-
true
831+
| SynExpr.IfThenElse(trivia = trivia), Dangling.IfThen dangling
832+
| SynExpr.IfThenElse(trivia = trivia), Dangling.Match dangling ->
833+
problematic dangling.Range trivia.ThenKeyword
834+
|| trivia.ElseKeyword |> Option.exists (problematic dangling.Range)
835+
836+
| SynExpr.IfThenElse(ifExpr = expr), Dangling.Sequential dangling
837+
| SynExpr.While(whileExpr = expr), Dangling.Problematic dangling
838+
| SynExpr.ForEach(enumExpr = expr), Dangling.Problematic dangling -> Range.rangeContainsRange expr.Range dangling.Range
804839

805840
| SynExpr.TryFinally(trivia = trivia), Dangling.Try tryExpr when problematic tryExpr.Range trivia.FinallyKeyword -> true
806841

@@ -824,6 +859,25 @@ module SynExpr =
824859
->
825860
true
826861

862+
// A match-like construct could be problematically nested like this:
863+
//
864+
// match () with
865+
// | _ when
866+
// p &&
867+
// let x = f ()
868+
// (let y = z
869+
// match x with
870+
// | 3 | _ -> y) -> ()
871+
// | _ -> ()
872+
| _, Dangling.Match matchOrTry when
873+
let line = getSourceLineStr matchOrTry.Range.EndLine
874+
let endCol = matchOrTry.Range.EndColumn
875+
876+
line.Length > endCol + 1
877+
&& line.AsSpan(endCol + 1).TrimStart(' ').StartsWith("->".AsSpan())
878+
->
879+
true
880+
827881
| SynExpr.Sequential(expr1 = SynExpr.Paren(expr = Is inner); expr2 = expr2), Dangling.Problematic _ when
828882
problematic inner.Range expr2.Range
829883
->
@@ -842,9 +896,10 @@ module SynExpr =
842896
| SynExpr.Sequential(expr1 = SynExpr.Paren(expr = Is inner); expr2 = expr2), _ when innerBindingsWouldShadowOuter inner expr2 ->
843897
true
844898

845-
| SynExpr.InterpolatedString _, SynExpr.Sequential _ -> true
899+
| SynExpr.InterpolatedString _, SynExpr.Sequential _
900+
| SynExpr.InterpolatedString _, SynExpr.Tuple(isStruct = false) -> true
846901

847-
| SynExpr.InterpolatedString(contents = contents), (SynExpr.Tuple(isStruct = false) | Dangling.Problematic _) ->
902+
| SynExpr.InterpolatedString(contents = contents), Dangling.Problematic _ ->
848903
contents
849904
|> List.exists (function
850905
| SynInterpolatedStringPart.FillExpr(qualifiers = Some _) -> true

‎src/Compiler/Service/SynPat.fs‎

Lines changed: 65 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -55,6 +55,24 @@ module SynPat =
5555
| SynPat.Tuple(isStruct = false; elementPats = Last(Rightmost pat)) -> pat
5656
| pat -> pat
5757

58+
/// Matches a nested as pattern.
59+
[<return: Struct>]
60+
let rec (|DanglingAs|_|) pat =
61+
let (|AnyDanglingAs|_|) =
62+
List.tryPick (function
63+
| DanglingAs -> Some()
64+
| _ -> None)
65+
66+
match pat with
67+
| SynPat.As _ -> ValueSome()
68+
| SynPat.Or(lhsPat = DanglingAs)
69+
| SynPat.Or(rhsPat = DanglingAs)
70+
| SynPat.ListCons(lhsPat = DanglingAs)
71+
| SynPat.ListCons(rhsPat = DanglingAs)
72+
| SynPat.Ands(pats = AnyDanglingAs)
73+
| SynPat.Tuple(isStruct = false; elementPats = AnyDanglingAs) -> ValueSome()
74+
| _ -> ValueNone
75+
5876
/// Matches if the given pattern is atomic.
5977
[<return: Struct>]
6078
let (|Atomic|_|) pat =
@@ -88,6 +106,7 @@ module SynPat =
88106
// fun (x, y, …) -> …
89107
// fun (x: …) -> …
90108
// fun (Pattern …) -> …
109+
// set (x: …, y: …) = …
91110
| SynPat.Typed _, SyntaxNode.SynPat(Rightmost(SynPat.Paren(Is pat, _))) :: SyntaxNode.SynMatchClause _ :: _
92111
| Rightmost(SynPat.Typed _), SyntaxNode.SynMatchClause _ :: _
93112
| SynPat.Typed _, SyntaxNode.SynExpr(SynExpr.LetOrUseBang _) :: _
@@ -98,23 +117,62 @@ module SynPat =
98117
| SynPat.LongIdent(argPats = SynArgPats.Pats(_ :: _)), SyntaxNode.SynBinding _ :: _
99118
| SynPat.LongIdent(argPats = SynArgPats.Pats(_ :: _)), SyntaxNode.SynExpr(SynExpr.Lambda _) :: _
100119
| SynPat.Tuple(isStruct = false), SyntaxNode.SynExpr(SynExpr.Lambda(parsedData = Some _)) :: _
101-
| SynPat.Typed _, SyntaxNode.SynExpr(SynExpr.Lambda(parsedData = Some _)) :: _ -> true
120+
| SynPat.Typed _, SyntaxNode.SynExpr(SynExpr.Lambda(parsedData = Some _)) :: _
121+
| SynPat.Typed _,
122+
SyntaxNode.SynPat(SynPat.Tuple(isStruct = false)) :: SyntaxNode.SynPat(SynPat.LongIdent _) :: SyntaxNode.SynBinding _ :: SyntaxNode.SynMemberDefn(SynMemberDefn.GetSetMember _) :: _
123+
| SynPat.Typed _,
124+
SyntaxNode.SynPat(SynPat.Tuple(isStruct = false)) :: SyntaxNode.SynPat(SynPat.LongIdent _) :: SyntaxNode.SynBinding(SynBinding(
125+
valData = SynValData(
126+
memberFlags = Some {
127+
MemberKind = SynMemberKind.PropertyGetSet | SynMemberKind.PropertyGet | SynMemberKind.PropertySet
128+
}))) :: _ -> true
102129

103130
// () is parsed as this.
104131
| SynPat.Const(SynConst.Unit, _), _ -> true
105132

106133
// (()) is required when overriding a generic member
107-
// where unit is the generic type argument:
134+
// where unit or a tuple type is the generic type argument:
108135
//
109136
// type C<'T> = abstract M : 'T -> unit
110137
// let _ = { new C<unit> with override _.M (()) = () }
111-
| SynPat.Paren(SynPat.Const(SynConst.Unit, _), _),
138+
// let _ = { new C<int * int> with override _.M ((x, y)) = () }
139+
| SynPat.Paren((SynPat.Const(SynConst.Unit, _) | SynPat.Tuple(isStruct = false)), _),
112140
SyntaxNode.SynPat(SynPat.LongIdent _) :: SyntaxNode.SynBinding _ :: SyntaxNode.SynExpr(SynExpr.ObjExpr(
113141
objType = SynType.App(typeArgs = _ :: _) | SynType.LongIdentApp(typeArgs = _ :: _))) :: _
114-
| SynPat.Paren(SynPat.Const(SynConst.Unit, _), _),
142+
| SynPat.Tuple(isStruct = false),
143+
SyntaxNode.SynPat(SynPat.Paren _) :: SyntaxNode.SynPat(SynPat.LongIdent _) :: SyntaxNode.SynBinding _ :: SyntaxNode.SynExpr(SynExpr.ObjExpr(
144+
objType = SynType.App(typeArgs = _ :: _) | SynType.LongIdentApp(typeArgs = _ :: _))) :: _
145+
| SynPat.Paren((SynPat.Const(SynConst.Unit, _) | SynPat.Tuple(isStruct = false)), _),
115146
SyntaxNode.SynPat(SynPat.LongIdent _) :: SyntaxNode.SynBinding _ :: SyntaxNode.SynMemberDefn _ :: SyntaxNode.SynTypeDefn(SynTypeDefn(
116147
typeRepr = SynTypeDefnRepr.ObjectModel(members = AnyGenericInheritOrInterfaceImpl))) :: _ -> true
117148

149+
// Not required:
150+
//
151+
// let (a,
152+
// b,
153+
// c) = …
154+
//
155+
// Required:
156+
//
157+
// let (a,
158+
// b,
159+
// c) =
160+
// …
161+
| SynPat.Tuple(isStruct = false; range = innerRange), SyntaxNode.SynBinding(SynBinding(expr = body)) :: _ ->
162+
innerRange.StartLine <> innerRange.EndLine
163+
&& innerRange.StartLine < body.Range.StartLine
164+
&& body.Range.StartColumn <= innerRange.StartColumn
165+
166+
// The parens could be required by a signature file like this:
167+
//
168+
// type SemanticClassificationItem =
169+
// new: (range * SemanticClassificationType) -> SemanticClassificationItem
170+
| SynPat.Paren(SynPat.Tuple(isStruct = false), _),
171+
SyntaxNode.SynPat(SynPat.LongIdent(longDotId = SynLongIdent(id = [ Ident "new" ]))) :: SyntaxNode.SynBinding _ :: SyntaxNode.SynMemberDefn _ :: SyntaxNode.SynTypeDefn _ :: _
172+
| SynPat.Tuple(isStruct = false),
173+
SyntaxNode.SynPat(SynPat.Paren _) :: SyntaxNode.SynPat(SynPat.LongIdent(longDotId = SynLongIdent(id = [ Ident "new" ]))) :: SyntaxNode.SynBinding _ :: SyntaxNode.SynMemberDefn _ :: SyntaxNode.SynTypeDefn _ :: _ ->
174+
true
175+
118176
// Parens are required around the atomic argument of
119177
// any additional `new` constructor that is not the last.
120178
//
@@ -204,9 +262,9 @@ module SynPat =
204262
// A | (B as C)
205263
// A & (B as C)
206264
// A, (B as C)
207-
| SynPat.Or _, SynPat.As _
208-
| SynPat.Ands _, SynPat.As _
209-
| SynPat.Tuple _, SynPat.As _
265+
| SynPat.Or _, (SynPat.As _ | DanglingAs)
266+
| SynPat.Ands _, (SynPat.As _ | DanglingAs)
267+
| SynPat.Tuple _, (SynPat.As _ | DanglingAs)
210268

211269
// x, (y, z)
212270
// x & (y, z)

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