Andrej Mitrovic:
However I'd like to see a custom compiler warning switch that
would
warn me if I tried to call opAssign on a fundamental or struct
type in
a foreach loop with a non-ref foreach parameter:
foreach (idx, val; arr)
{
val.x = idx; // clearly a bug, but lacks warning
}
I've had *numerous* occasions over the last few years where
I've had this bug happen to me.
The same for me. Most people seem to not care for this problem, I
don't understand why. But I think it's a common source for bugs
in D programs. D design must take in account not just error-prone
features inherited from C, but also to avoid bug-prone situations
created by D-specific features.
C# designers have avoided this problem:
http://msdn.microsoft.com/en-us/library/04t3s14w.aspx
A possible solution is to require an explicit annotation if you
want to modify just the copy:
foreach (idx, @copy val; arr)
val.x = idx;
But maybe better is to do as in C# and turn "val" (and idx!) into
a const on default, and require an annotation if you want to
modify the copy:
foreach (idx, @mutable val; arr)
val.x = idx;
Bye,
bearophile
