https://issues.dlang.org/show_bug.cgi?id=19623

          Issue ID: 19623
           Summary: HERE string identifier cannot start with Unicode
                    letter
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: rejects-valid, trivial
          Severity: trivial
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: Marco.Leise@gmx.de

The character c is actually not a decoded dchar, but the first byte from the sequence. Subsequently the test for Unicode letters fails here:

https://github.com/dlang/dmd/blob/77260f78e45675bb1418feb9836ed0c6252fd1b9/src/dmd/lexer.d#L1504

So this would fail:

q"übel
übel"

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