https://issues.dlang.org/show_bug.cgi?id=17221

          Issue ID: 17221
           Summary: __traits(isUnsigned, bool/char) should be false
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: code@dawg.eu

See issue 17196, it doesn't make much sense to treat bool and chars as unsigned. This would need to be deprecated before being changed.

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