https://issues.dlang.org/show_bug.cgi?id=23252

          Issue ID: 23252
           Summary: Deprecation: format specifier "%[]]" is invalid
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: ibuclaw@gdcproject.org

Another bogus deprecation message.  If the first character of a scanset is `]`, then that is treated as wanting to match `]`, so is skipped over.

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