https://issues.dlang.org/show_bug.cgi?id=23845

          Issue ID: 23845
           Summary: std.math.traits.copysign returns the wrong value
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: major
          Priority: P1
         Component: phobos
          Assignee: nobody@puremagic.com
          Reporter: grylliade@hotmail.com

As written, the function simply returns its first parameter. Should likely return cast(R) *pto, though my pointer syntax is rusty—surely doing all that work with pto should have *some* point (no pun intended).

I’d honestly bump this up to critical, but if no one’s noticed this yet, maybe
it shouldn’t be—except copysign() can be called from cbrt(), at the very least.
It keeps cbrt() from being inferred pure on the MS runtime, I think; if I’m
wrong, that’s a separate bug.

--