On 2/2/20 12:51 PM, ShadoLight wrote:
// Should this assertion pass or fail?
static assert(is(a)); //PASS
static assert(is(b)); //FAIL
But I don't see how braces will affect this. Can you explain?
First, note that:
struct S(T) {}
is *exactly* equivalent to (in fact, you can write it this way, and it
works exactly the same):
template S(T) { struct S {} }
So does S!int refer to the template instantiation (which is not a type)
or the eponymous S struct inside the template (which is a type)? This
was Paul's point. Since you didn't use any members, there is an
ambiguity of intention (if accessing other parts of the template are
allowed).
Even if you use a member, it's not hard to come up with an ambiguous
example:
struct S(T) {
template S(X) {}
}
What does S!int.S refer to? The S template inside the S struct, or the S
struct itself inside the outer S template?
This is the main reason why eponymous templates were disallowed from
using the classical template access syntax. I think this was not a
mistake, and we are better off for it.
-Steve
