Optimize comment after source code detection. Fixes fsprojects#1671.

src/Fantomas.Tests/CommentTests.fs

@@ -1311,3 +1311,175 @@ let a =  b
 (* meh *)
 let a = b
 """
+
+[<Test>]
+let ``comment right after first token`` () =
+    formatSourceString
+        false
+        """
+1//
+// next line
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+1 //
+// next line
+"""
+
+[<Test>]
+[<Ignore("line comment after block comment currently not supported")>]
+let ``block comment followed by line comment`` () =
+    formatSourceString
+        false
+        """
+(* foo *)// bar
+let a = 0
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+(* foo *) // bar
+let a = 0
+"""
+
+[<Test>]
+let ``line comment after source code`` () =
+    formatSourceString
+        false
+        """
+__SOURCE_DIRECTORY__ // comment
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+__SOURCE_DIRECTORY__ // comment
+"""
+
+[<Test>]
+let ``line comment after hash define`` () =
+    formatSourceString
+        false
+        """
+#if FOO // MEH
+#endif
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+#if FOO // MEH
+#endif
+"""
+
+[<Test>]
+let ``line comment after interpolated string`` () =
+    formatSourceString
+        false
+        """
+$"{meh}.." // foo
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+$"{meh}.." // foo
+"""
+
+[<Test>]
+let ``line comment after negative constant`` () =
+    formatSourceString
+        false
+        """
+-1.0 // foo
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+-1.0 // foo
+"""
+
+[<Test>]
+let ``line comment after trivia number`` () =
+    formatSourceString
+        false
+        """
+1. // bar
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+1. // bar
+"""
+
+[<Test>]
+let ``line comment after infix operator in full words`` () =
+    formatSourceString
+        false
+        """
+op_LessThan // meh
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+op_LessThan // meh
+"""
+
+[<Test>]
+let ``line comment after ident between ticks`` () =
+    formatSourceString
+        false
+        """
+``foo oo`` // bar
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+``foo oo`` // bar
+"""
+
+[<Test>]
+let ``line comment after special char`` () =
+    formatSourceString
+        false
+        """
+'\u0000' // foo
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+'\u0000' // foo
+"""
+
+[<Test>]
+let ``line comment after embedded il`` () =
+    formatSourceString
+        false
+        """
+(# "" x : 'U #) // bar
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+(# "" x : 'U #) // bar
+"""

src/Fantomas.Tests/TriviaTests.fs

@@ -247,10 +247,9 @@ x
     let triviaNodes = toTrivia source |> List.head
 
     match triviaNodes with
-    | [ { ContentBefore = [ Comment (BlockComment (fooComment, _, true)); Comment (BlockComment (barComment, _, true)) ] } ] ->
-        fooComment == "(* foo *)"
-        barComment == "(* bar *)"
-    | _ -> fail ()
+    | [ { ContentBefore = [ Comment (BlockComment (combinedComment, _, true)) ] } ] ->
+        combinedComment == "(* foo *)\n(* bar *)"
+    | _ -> Assert.Fail(sprintf "Unexpected trivia %A" triviaNodes)
 
 [<Test>]
 let ``block comment inside line comment parsed correctly`` () =

src/Fantomas/CodePrinter.fs

@@ -1602,7 +1602,7 @@ and genExpr astContext synExpr ctx =
             +> sepSpace
             +> genExpr astContext e
 
-        | Paren (_, ILEmbedded r, _, _) ->
+        | Paren (_, ILEmbedded r, rpr, _) ->
             fun ctx ->
                 let expr =
                     Map.tryFindOrEmptyList SynExpr_LibraryOnlyILAssembly ctx.TriviaMainNodes
@@ -1618,7 +1618,9 @@ and genExpr astContext synExpr ctx =
                     |> Option.map (!-)
                     |> Option.defaultValue sepNone
 
-                expr ctx
+                (expr
+                 +> optSingle (fun r -> leaveNodeTokenByName r RPAREN) rpr)
+                    ctx
         | Paren (lpr, e, rpr, pr) ->
             match e with
             | LetOrUses _ ->