Overflow-safe use of unsigned integral types

[rumbu]

On Sunday, 10 November 2013 at 12:19:18 UTC, mike james wrote:
> When writing software for embedded micros you can always check 
> an overflow flag - is the no such mechanism on PC software?
>

This is not overflow checking, it's the compiler considering a
variable of type int implicitely convertible to equivalent
unsigned types at bit level.

I suppose it's a bug or may be the documentation is wrong
(http://dlang.org/type.html):

ubyte  u1 = cast(byte)-1;  // error, -1 cannot be represented in
a ubyte
ushort u2 = cast(short)-1; // error, -1 cannot be represented in
a ushort

These two lines are succesfully compiled by the last DMD on 
Windows.