[Issue 24278] New: std.math.abs promotes unsigned argument to 32 bits

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24278

          Issue ID: 24278
           Summary: std.math.abs promotes unsigned argument to 32 bits
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: minor
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: dkorpel at live.nl

```D
import std.math;  
void main()
{
     assert(is(typeof(abs(ubyte(8u))) == ubyte));
}
```

The assert fails, while the documentation says "the return type will be the
same as the input."

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