https://issues.dlang.org/show_bug.cgi?id=20741

          Issue ID: 20741
           Summary: `dup`, `idup` for arrays plus `keys`, `values` for
                    built-in associative arrays: if a type is known to
                    have a postblit do not emit code for the non-postblit
                    path and vice versa
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: druntime
          Assignee: nobody@puremagic.com
          Reporter: n8sh.secondary@hotmail.com

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