Allow return|return! yield|yield! and type annotations without parentheses

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

@@ -31,6 +31,7 @@
 * Fix code completion considers types from own namespace non-imported ([PR #18518](https://github.com/dotnet/fsharp/issues/18518))
 * Code completion: fix getting qualifier expression in do statements in type decls ([PR #18524](https://github.com/dotnet/fsharp/pull/18524))
 * Fixed: [#18441](https://github.com/dotnet/fsharp/issues/18441) FSI multi-emit unstable. ([PR #18465](https://github.com/dotnet/fsharp/pull/18465))
+* Fixed: Allow `return`, `return!`, `yield`, `yield!` type annotations without parentheses ([PR #18533](https://github.com/dotnet/fsharp/pull/18533))
 
 ### Added
 * Added missing type constraints in FCS. ([PR #18241](https://github.com/dotnet/fsharp/pull/18241))

src/Compiler/pars.fsy

@@ -4430,6 +4430,34 @@ declExpr:
      { let trivia: SynExprYieldOrReturnTrivia = { YieldOrReturnKeyword = rhs parseState 1 }
        SynExpr.YieldOrReturn(($1, not $1), $2, (unionRanges (rhs parseState 1) $2.Range), trivia) }
 
+  | YIELD declExpr COLON typ
+     { let trivia: SynExprYieldOrReturnTrivia = { YieldOrReturnKeyword = rhs parseState 1 }
+       let typedExpr = SynExpr.Typed($2, $4, unionRanges $2.Range $4.Range)
+       SynExpr.YieldOrReturn(($1, not $1), typedExpr, (unionRanges (rhs parseState 1) $4.Range), trivia) }
+
+  | YIELD declExpr opt_topReturnTypeWithTypeConstraints
+     { let trivia: SynExprYieldOrReturnTrivia = { YieldOrReturnKeyword = rhs parseState 1 }
+       let expr = 
+           match $3 with
+           | None -> $2
+           | Some(_, SynReturnInfo((ty, _), m)) -> 
+               SynExpr.Typed($2, ty, unionRanges $2.Range m)
+       SynExpr.YieldOrReturn(($1, not $1), expr, (unionRanges (rhs parseState 1) expr.Range), trivia) }
+
+  | YIELD_BANG declExpr COLON typ
+    {  let trivia: SynExprYieldOrReturnFromTrivia = { YieldOrReturnFromKeyword = rhs parseState 1 }
+       let typedExpr = SynExpr.Typed($2, $4, unionRanges $2.Range $4.Range)
+       SynExpr.YieldOrReturnFrom(($1, not $1), typedExpr, (unionRanges (rhs parseState 1) $2.Range), trivia) }
+
+  | YIELD_BANG declExpr opt_topReturnTypeWithTypeConstraints
+    {  let trivia: SynExprYieldOrReturnFromTrivia = { YieldOrReturnFromKeyword = rhs parseState 1 }
+       let expr = 
+           match $3 with
+           | None -> $2
+           | Some(_, SynReturnInfo((ty, _), m)) -> 
+               SynExpr.Typed($2, ty, unionRanges $2.Range m)
+       SynExpr.YieldOrReturnFrom(($1, not $1), expr, (unionRanges (rhs parseState 1) $2.Range), trivia) }
+
   | YIELD_BANG declExpr
      {  let trivia: SynExprYieldOrReturnFromTrivia = { YieldOrReturnFromKeyword = rhs parseState 1 }
         SynExpr.YieldOrReturnFrom(($1, not $1), $2, (unionRanges (rhs parseState 1) $2.Range), trivia) }

tests/FSharp.Compiler.ComponentTests/Language/ComputationExpressionTests.fs

@@ -23,6 +23,41 @@ let x = lb {1; 2;}
         |> shouldSucceed
         |> ignore
 
+    [<Fact>]
+    let ``Allow CE return and type annotations to play well together without needing parentheses``() =
+        FSharp """
+module ComputationExpressionTests
+open System
+
+type MyType() =
+    interface IDisposable with
+        member this.Dispose () = ()
+
+let f () =
+    async {
+        return new MyType() : IDisposable
+    }
+
+let f1 () =
+    async {
+        return new MyType() :> IDisposable
+    }
+
+let f2 () : Async<IDisposable> =
+    async {
+        return new MyType()
+    }
+
+let f3 () =
+    async {
+        return (new MyType() : IDisposable)
+    }
+        """
+        |> asExe
+        |> withOptions ["--nowarn:988"]
+        |> compileAndRun
+        |> shouldSucceed
+
     [<Fact>]
     let ``A CE explicitly using Zero fails without a defined Zero``() =
         FSharp """

tests/service/data/SyntaxTree/Expression/Return 01.fs

@@ -0,0 +1,7 @@
+module Module
+
+let _ =
+    async {
+        return new MyType() : IDisposable
+    }
+

tests/service/data/SyntaxTree/Expression/Return 01.fs.bsl

@@ -0,0 +1,36 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/Expression/Return 01.fs", false, QualifiedNameOfFile Module, [], [],
+      [SynModuleOrNamespace
+         ([Module], false, NamedModule,
+          [Let
+             (false,
+              [SynBinding
+                 (None, Normal, false, false, [],
+                  PreXmlDoc ((3,0), FSharp.Compiler.Xml.XmlDocCollector),
+                  SynValData
+                    (None, SynValInfo ([], SynArgInfo ([], false, None)), None),
+                  Wild (3,4--3,5), None,
+                  App
+                    (NonAtomic, false, Ident async,
+                     ComputationExpr
+                       (false,
+                        YieldOrReturn
+                          ((false, true),
+                           Typed
+                             (New
+                                (false,
+                                 LongIdent (SynLongIdent ([MyType], [], [None])),
+                                 Const (Unit, (5,25--5,27)), (5,15--5,27)),
+                              LongIdent
+                                (SynLongIdent ([IDisposable], [], [None])),
+                              (5,15--5,41)), (5,8--5,41),
+                           { YieldOrReturnKeyword = (5,8--5,14) }), (4,10--6,5)),
+                     (4,4--6,5)), (3,4--3,5), NoneAtLet,
+                  { LeadingKeyword = Let (3,0--3,3)
+                    InlineKeyword = None
+                    EqualsRange = Some (3,6--3,7) })], (3,0--6,5))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--6,5), { LeadingKeyword = Module (1,0--1,6) })], (true, true),
+      { ConditionalDirectives = []
+        CodeComments = [] }, set []))

tests/service/data/SyntaxTree/Expression/Return 02.fs

@@ -0,0 +1,7 @@
+module Module
+
+let _ =
+    async {
+        return (new MyType() : IDisposable)
+    }
+

tests/service/data/SyntaxTree/Expression/Return 02.fs.bsl

@@ -0,0 +1,39 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/Expression/Return 02.fs", false, QualifiedNameOfFile Module, [], [],
+      [SynModuleOrNamespace
+         ([Module], false, NamedModule,
+          [Let
+             (false,
+              [SynBinding
+                 (None, Normal, false, false, [],
+                  PreXmlDoc ((3,0), FSharp.Compiler.Xml.XmlDocCollector),
+                  SynValData
+                    (None, SynValInfo ([], SynArgInfo ([], false, None)), None),
+                  Wild (3,4--3,5), None,
+                  App
+                    (NonAtomic, false, Ident async,
+                     ComputationExpr
+                       (false,
+                        YieldOrReturn
+                          ((false, true),
+                           Paren
+                             (Typed
+                                (New
+                                   (false,
+                                    LongIdent
+                                      (SynLongIdent ([MyType], [], [None])),
+                                    Const (Unit, (5,26--5,28)), (5,16--5,28)),
+                                 LongIdent
+                                   (SynLongIdent ([IDisposable], [], [None])),
+                                 (5,16--5,42)), (5,15--5,16), Some (5,42--5,43),
+                              (5,15--5,43)), (5,8--5,43),
+                           { YieldOrReturnKeyword = (5,8--5,14) }), (4,10--6,5)),
+                     (4,4--6,5)), (3,4--3,5), NoneAtLet,
+                  { LeadingKeyword = Let (3,0--3,3)
+                    InlineKeyword = None
+                    EqualsRange = Some (3,6--3,7) })], (3,0--6,5))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--6,5), { LeadingKeyword = Module (1,0--1,6) })], (true, true),
+      { ConditionalDirectives = []
+        CodeComments = [] }, set []))

tests/service/data/SyntaxTree/Expression/Return 03.fs

@@ -0,0 +1,7 @@
+module Module
+
+let _ =
+    async {
+        return new MyType() :> IDisposable
+    }
+

tests/service/data/SyntaxTree/Expression/Return 03.fs.bsl

@@ -0,0 +1,36 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/Expression/Return 03.fs", false, QualifiedNameOfFile Module, [], [],
+      [SynModuleOrNamespace
+         ([Module], false, NamedModule,
+          [Let
+             (false,
+              [SynBinding
+                 (None, Normal, false, false, [],
+                  PreXmlDoc ((3,0), FSharp.Compiler.Xml.XmlDocCollector),
+                  SynValData
+                    (None, SynValInfo ([], SynArgInfo ([], false, None)), None),
+                  Wild (3,4--3,5), None,
+                  App
+                    (NonAtomic, false, Ident async,
+                     ComputationExpr
+                       (false,
+                        YieldOrReturn
+                          ((false, true),
+                           Upcast
+                             (New
+                                (false,
+                                 LongIdent (SynLongIdent ([MyType], [], [None])),
+                                 Const (Unit, (5,25--5,27)), (5,15--5,27)),
+                              LongIdent
+                                (SynLongIdent ([IDisposable], [], [None])),
+                              (5,15--5,42)), (5,8--5,42),
+                           { YieldOrReturnKeyword = (5,8--5,14) }), (4,10--6,5)),
+                     (4,4--6,5)), (3,4--3,5), NoneAtLet,
+                  { LeadingKeyword = Let (3,0--3,3)
+                    InlineKeyword = None
+                    EqualsRange = Some (3,6--3,7) })], (3,0--6,5))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--6,5), { LeadingKeyword = Module (1,0--1,6) })], (true, true),
+      { ConditionalDirectives = []
+        CodeComments = [] }, set []))

tests/service/data/SyntaxTree/Expression/Return 04.fs

@@ -0,0 +1,7 @@
+module Module
+
+let _ =
+    async {
+        return (new MyType() :> IDisposable)
+    }
+

tests/service/data/SyntaxTree/Expression/Return 04.fs.bsl

@@ -0,0 +1,39 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/Expression/Return 04.fs", false, QualifiedNameOfFile Module, [], [],
+      [SynModuleOrNamespace
+         ([Module], false, NamedModule,
+          [Let
+             (false,
+              [SynBinding
+                 (None, Normal, false, false, [],
+                  PreXmlDoc ((3,0), FSharp.Compiler.Xml.XmlDocCollector),
+                  SynValData
+                    (None, SynValInfo ([], SynArgInfo ([], false, None)), None),
+                  Wild (3,4--3,5), None,
+                  App
+                    (NonAtomic, false, Ident async,
+                     ComputationExpr
+                       (false,
+                        YieldOrReturn
+                          ((false, true),
+                           Paren
+                             (Upcast
+                                (New
+                                   (false,
+                                    LongIdent
+                                      (SynLongIdent ([MyType], [], [None])),
+                                    Const (Unit, (5,26--5,28)), (5,16--5,28)),
+                                 LongIdent
+                                   (SynLongIdent ([IDisposable], [], [None])),
+                                 (5,16--5,43)), (5,15--5,16), Some (5,43--5,44),
+                              (5,15--5,44)), (5,8--5,44),
+                           { YieldOrReturnKeyword = (5,8--5,14) }), (4,10--6,5)),
+                     (4,4--6,5)), (3,4--3,5), NoneAtLet,
+                  { LeadingKeyword = Let (3,0--3,3)
+                    InlineKeyword = None
+                    EqualsRange = Some (3,6--3,7) })], (3,0--6,5))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--6,5), { LeadingKeyword = Module (1,0--1,6) })], (true, true),
+      { ConditionalDirectives = []
+        CodeComments = [] }, set []))

tests/service/data/SyntaxTree/Expression/Return 05.fs

@@ -0,0 +1,7 @@
+module Module
+
+let _ =
+    async {
+        return new MyType()
+    }
+

tests/service/data/SyntaxTree/Expression/Return 05.fs.bsl

@@ -0,0 +1,32 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/Expression/Return 05.fs", false, QualifiedNameOfFile Module, [], [],
+      [SynModuleOrNamespace
+         ([Module], false, NamedModule,
+          [Let
+             (false,
+              [SynBinding
+                 (None, Normal, false, false, [],
+                  PreXmlDoc ((3,0), FSharp.Compiler.Xml.XmlDocCollector),
+                  SynValData
+                    (None, SynValInfo ([], SynArgInfo ([], false, None)), None),
+                  Wild (3,4--3,5), None,
+                  App
+                    (NonAtomic, false, Ident async,
+                     ComputationExpr
+                       (false,
+                        YieldOrReturn
+                          ((false, true),
+                           New
+                             (false,
+                              LongIdent (SynLongIdent ([MyType], [], [None])),
+                              Const (Unit, (5,25--5,27)), (5,15--5,27)),
+                           (5,8--5,27), { YieldOrReturnKeyword = (5,8--5,14) }),
+                        (4,10--6,5)), (4,4--6,5)), (3,4--3,5), NoneAtLet,
+                  { LeadingKeyword = Let (3,0--3,3)
+                    InlineKeyword = None
+                    EqualsRange = Some (3,6--3,7) })], (3,0--6,5))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--6,5), { LeadingKeyword = Module (1,0--1,6) })], (true, true),
+      { ConditionalDirectives = []
+        CodeComments = [] }, set []))

tests/service/data/SyntaxTree/Expression/Return 06.fs

@@ -0,0 +1,7 @@
+module Module
+
+let _ =
+    async {
+        return (new MyType())
+    }
+

tests/service/data/SyntaxTree/Expression/Return 06.fs.bsl

@@ -0,0 +1,34 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/Expression/Return 06.fs", false, QualifiedNameOfFile Module, [], [],
+      [SynModuleOrNamespace
+         ([Module], false, NamedModule,
+          [Let
+             (false,
+              [SynBinding
+                 (None, Normal, false, false, [],
+                  PreXmlDoc ((3,0), FSharp.Compiler.Xml.XmlDocCollector),
+                  SynValData
+                    (None, SynValInfo ([], SynArgInfo ([], false, None)), None),
+                  Wild (3,4--3,5), None,
+                  App
+                    (NonAtomic, false, Ident async,
+                     ComputationExpr
+                       (false,
+                        YieldOrReturn
+                          ((false, true),
+                           Paren
+                             (New
+                                (false,
+                                 LongIdent (SynLongIdent ([MyType], [], [None])),
+                                 Const (Unit, (5,26--5,28)), (5,16--5,28)),
+                              (5,15--5,16), Some (5,28--5,29), (5,15--5,29)),
+                           (5,8--5,29), { YieldOrReturnKeyword = (5,8--5,14) }),
+                        (4,10--6,5)), (4,4--6,5)), (3,4--3,5), NoneAtLet,
+                  { LeadingKeyword = Let (3,0--3,3)
+                    InlineKeyword = None
+                    EqualsRange = Some (3,6--3,7) })], (3,0--6,5))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--6,5), { LeadingKeyword = Module (1,0--1,6) })], (true, true),
+      { ConditionalDirectives = []
+        CodeComments = [] }, set []))

tests/service/data/SyntaxTree/Expression/Return 07.fs

@@ -0,0 +1,6 @@
+module Module
+
+let _ =
+    async { 
+        return new MyType() :
+    }

tests/service/data/SyntaxTree/Expression/Return 07.fs.bsl

@@ -0,0 +1,36 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/Expression/Return 07.fs", false, QualifiedNameOfFile Module, [], [],
+      [SynModuleOrNamespace
+         ([Module], false, NamedModule,
+          [Let
+             (false,
+              [SynBinding
+                 (None, Normal, false, false, [],
+                  PreXmlDoc ((3,0), FSharp.Compiler.Xml.XmlDocCollector),
+                  SynValData
+                    (None, SynValInfo ([], SynArgInfo ([], false, None)), None),
+                  Wild (3,4--3,5), None,
+                  App
+                    (NonAtomic, false, Ident async,
+                     ComputationExpr
+                       (false,
+                        YieldOrReturn
+                          ((false, true),
+                           Typed
+                             (New
+                                (false,
+                                 LongIdent (SynLongIdent ([MyType], [], [None])),
+                                 Const (Unit, (5,25--5,27)), (5,15--5,27)),
+                              FromParseError (5,29--5,29), (5,15--5,29)),
+                           (5,8--5,29), { YieldOrReturnKeyword = (5,8--5,14) }),
+                        (4,10--6,5)), (4,4--6,5)), (3,4--3,5), NoneAtLet,
+                  { LeadingKeyword = Let (3,0--3,3)
+                    InlineKeyword = None
+                    EqualsRange = Some (3,6--3,7) })], (3,0--6,5))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--6,5), { LeadingKeyword = Module (1,0--1,6) })], (true, true),
+      { ConditionalDirectives = []
+        CodeComments = [] }, set []))
+
+(6,4)-(6,5) parse error Unexpected symbol '}' in expression