https://issues.dlang.org/show_bug.cgi?id=13991

          Issue ID: 13991
           Summary: Invariant grammar does not document that parenthesis
                    are optional
           Product: D
           Version: D2
          Hardware: All
               URL: http://dlang.org/grammar.html#Invariant
                OS: All
            Status: NEW
          Keywords: spec
          Severity: normal
          Priority: P1
         Component: websites
          Assignee: nobody@puremagic.com
          Reporter: briancschott@gmail.com
            Blocks: 10233

https://github.com/D-Programming-Language/dmd/pull/3540 should have had a documentation change.

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