On Tuesday, 6 October 2015 at 05:38:36 UTC, Jonathan M Davis
wrote:
Your suggestion only works by assuming that the result will fit
in a char, which doesn't fit at all with how coversions are
currently done in D. It would allow for narrowing conversions
which lost data. And there's no way that Walter would go for
that (and I don't think that he should). VRP solves the problem
insofar as it can guarantee that the result will fit in the
target type and thus reduces the need for casting, but simply
assuming that char + int will fit in a char just doesn't work
unless we're going to allow narrowing conversions to lose data,
which we aren't.
If we were to allow the specific conversions that you're
suggesting but only when VRP was used, then that could work,
though it does make the implicit rules even screwier, becauses
it becomes very dependent on how the int that you're trying to
assign to a char was generated in the first place (straight
assignment wouldn't work, but '0' - 40 would, whereas 'a' + 500
wouldn't, etc.). VRP already makes it a bit funky as it is,
though mostly in a straightforward manner.
I see, this is a new problem introduced by `char + int = char`.
But at least the following could be disallowed without
introducing problems:
int a = 'a';
char b = 32;
But strictly speaking, we already accept overflow (i.e. loss of
precision) for ints, so it's a bit inconsistent to disallow it
for chars.
