On Wed, Jun 10, 2020 at 10:58:57PM -0600, Jonathan M Davis via
Digitalmars-d-learn wrote:
[...]
> As things stand, @property has no real practical purpose but
> frequently gets used to indicate that it's the intention of a
> function's author for it to be used as if it were a variable. I
> suspect that it's also frequently misunderstand that it's required if
> you want to call a function without parens. So, you're likely to see
> @property in quite a lot of D code, but ultimately, all it's really
> doing is serving as documentation of the author's intent and screwing
> up metaprogramming.
[...]
Ironically, just today I ran into this corner case where @property
actually became a solution to a real problem:
//-----module1.d------
auto someGenericFunc(T)(T t) {
...
static if (is(typeof(T.init.method) : T)) {
R someRange = ...; // ElementType!R == T
auto value = someRange.map!(e => e.method);
}
...
}
//-----module2.d------
struct MyType {
...
auto method()() {
return ...;
}
...
}
//------module3.d-----
import module1;
import module2;
auto someFunc(...) {
auto result = someGenericFunc!MyType;
}
This was failing compilation, because when MyType.method is a template,
the static if condition in module1 fails. Adding @property to
MyType.method tells the compiler that `T.init.method` is intended to
refer to the return value rather than the template function itself, and
thus neatly solves the problem.
T
--
It's amazing how careful choice of punctuation can leave you hanging:
