bearophile schrieb:
Manfred_Nowak:
Daniel Gibson wrote:
What's wrong with "with"?
http://www.digitalmars.com/d/archives/digitalmars/D/with_should_be_deprecat
ed_with_extreme_prejudice_90375.html#N90375
I see
Andrei said there:
I think "with" is a very dangerous feature due to the way it hides
symbols. It essentially makes the feeblest attempt at modular reasoning
utterly impossible:
int x, y;
with (whatever)
{
y += x;
++x;
}
What can be said about such code? Nothing. If whatever has or will ever
have fields x or y or both, the names will bind to them; otherwise,
they'll bind to the locals. Non-local code dependency at its finest.
Today "with" is a bit tricky still, but its main problem that Andrei talks
about has being patched. So this code:
struct Foo { int x, y; }
void main() {
Foo f;
int x, y;
with (f) {
y += x;
++x;
}
}
Generates:
temp.d(6): Error: with symbol temp.Foo.y is shadowing local symbol temp.main.y
temp.d(6): Error: with symbol temp.Foo.x is shadowing local symbol temp.main.x
temp.d(7): Error: with symbol temp.Foo.x is shadowing local symbol temp.main.x
Bye,
bearophile
Great, so "with" shouldn't be much of a problem anymore. I find it really handy,
e.g. when dealing with enums (like in a switch() statement).
Cheers,
- Daniel
