[Issue 20678] New: Integral deprecation should not trigger on valid code

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20678

          Issue ID: 20678
           Summary: Integral deprecation should not trigger on valid code
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: pro.mathias.lang at gmail.com

The current rule for triggering the integral deprecation message are way too
lax and intrusive...
The following is perfectly valid:
```
struct BitField
{
    private ushort[] data;
    private enum BitsPerT = (ushort.sizeof * 8);

    public bool opIndexAssign (bool value, size_t index)
    {
        if (!value)
        {
            this.data[index / BitsPerT] &= ~mask(index); // HERE
        }
        return value;
    }

    static ushort mask (size_t index)
    {
        return (1 << ( BitsPerT - 1 - (index % BitsPerT)));
    }
}
```

But it forces the user to insert a dumb cast on the line annotated with `//
HERE`.
This can be seen in https://issues.dlang.org/show_bug.cgi?id=19614

--