Why are unsigned to signed conversions implicit and don't emit a warning?

[Jonathan M Davis]

> Andrej Mitrovic:
> > I just had a little bug in my code. In the WindowsAPI, there's this
> > alias:
> > 
> > alias ubyte BYTE;
> > 
> > Unfortunately I didn't check for this, and I erroneously assumed BYTE was
> > a signed value (blame it on my lack of coffee).
> 
> I and Don have asked (in Bugzilla and elsewhere) to change the built-in
> names into sbyte and ubyte, to avoid the common confusions between signed
> and unsigned bytes in D, but Walter was deaf to this.
> 
> > But what really surprises me is that these unsigned to signed conversions
> > happen implicitly. I didn't even get a warning, even though I have all
> > warning switches turned on.
> 
> Add your vote here (I have voted this), a bug report from 07 2006, but
> Walter doesn't like this warning, and warnings in general too:
> http://d.puremagic.com/issues/show_bug.cgi?id=259

Personally, I see _zero_ value in renaming byte, int, etc. to sbyte, sint, 
etc. It's well-known that they're signed. I don't see how adding an extra s 
would make that any clearer. Their names are perfectly clear as they are.

However, I also would have thought that converting between signed and unsigned 
values would be just as much of an error as narrowing conversions are - such 
as assigning an int to a byte. And arguably, assigning either an unsigned 
value to a signed value or vice versa is _also_ a narrowing conversion. So, I 
would have thought that it would be an error. Apparently not though.

- Jonathan M Davis