On 03/29/2013 06:07 PM, Ben Gertzfield wrote:
Hi folks,
I ran into what I think might be a bug with template specialization not
applying when using a mixin template to specialize a function.
Here's an example:
http://pastebin.com/Wp96KHAY
The output I get with dmd v2.061 seems to show that the compiler only
chooses a template specialization if a template mixin defines both the
most general function as well as the specialized version.
In the example below, I would expect the second instance of Bar.go(T) to
be MakeGo.go(T : U).
$ rdmd templateSpecialization.d
Foo.go(T)
Foo.go(T : int)
Bar.go(T)
Bar.go(T : int)
Bar.go(T)
MakeGo2.go(T)
MakeGo2.go(T : U)
I chatted with Andrei, and he suggested this behavior seemed like a bug.
Anyway, the workaround is pretty easy (ensure we provide both the
general and specialized implementation of the method when using a mixin
template), but I wanted to send it to the group to see if I'm missing
something.
It is not a bug.
The relevant part of dlang.org specification:
dlang.org/template-mixin.html:
Mixin Scope
The declarations in a mixin are ‘imported’ into the surrounding scope.
If the name of a declaration in a mixin is the same as a declaration in
the surrounding scope, the surrounding declaration overrides the mixin one:
int x = 3;
mixin template Foo() {
int x = 5;
int y = 5;
}
mixin Foo;
int y = 3;
void test() {
writefln("x = %d", x); // prints 3
writefln("y = %d", y); // prints 3
}
