Comment #0 by bearophile_hugs — 2013-06-23T13:11:24Z
A low-priority enhancement request.
For this code:
void main() {
ubyte x;
ubyte y = x << 1;
}
The range analysis determines that it's conceivable to the result of that expression to not fit in y, so the D compiler 2.064alpha gives:
temp.d(3): Error: cannot implicitly convert expression (cast(int)x << 1) of type int to ubyte
To help the programmer understand faster the mistake in his/her code when expressions become more complex I think it's also useful to print the range resulting from the analysis, like:
temp.d(3): Error: cannot implicitly convert expression (cast(int)x << 1) in interval [0 ... 510] of type int to ubyte
It uses 3 dots because it's an interval that includes the right end. Otherwise if you print an interval open on the right in a case like this you have to print a ulong.max+1 value:
void main() {
ulong x;
int y = x;
}
One downside: those error messages become a little longer (and a bit more noisy).
Comment #1 by bearophile_hugs — 2013-06-23T14:08:52Z
> temp.d(3): Error: cannot implicitly convert expression (cast(int)x << 1) in
> interval [0 ... 510] of type int to ubyte
Jonathan M Davis suggests to use a more mathematical syntax to denote an interval closed on the right, like:
temp.d(3): Error: cannot implicitly convert expression (cast(int)x << 1) in interval [0, 510] of type int to ubyte
Comment #2 by robert.schadek — 2024-12-13T18:08:31Z