https://issues.dlang.org/show_bug.cgi?id=22931

          Issue ID: 22931
           Summary: importC: Error: `0` has no effect
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: ImportC, rejects-valid
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: duser@neet.fi
                CC: duser@neet.fi

void fn()
{
        0;
}

perhaps this error could be relaxed for importC

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