On Saturday, 5 November 2016 at 10:09:55 UTC, Adam D. Ruppe wrote:
On Saturday, 5 November 2016 at 08:27:49 UTC, Nemanja Boric
wrote:
// This - does nothing
variant.visit!( (string s) => { enforce(false); x = 2;
},
It calls the function... which returns a delegate, which you
never called.
This is one of the most common mistakes people are making: {}
in D is a delegate, and () => is a delegate, therefore () => {}
is a delegate that returns a delegate... usually NOT what you
want.
What you wrote is equivalent to writing
delegate() callback(string s) {
return delegate() {
enforce(false);
x = 2;
};
}
Do not use the => syntax if there is more than one expression.
You'll get what you want by simply leaving the => out:
// This works as expected
variant.visit!( (string s) { x = 2; },
(int i) { x = 3; });
That's really confusing. I've used D for quite a while, and
didn't know that. Admittedly I doubt I've ever tried () => { },
but given languages like C# which this syntax was partially taken
from(?), that behaviour is very unexpected. That feels like it
should be a compiler warning.
