https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92633
Bug ID: 92633
Summary: [concepts] constrained lambda with placehoder syntax
getting wrong substitution
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: eric.niebler at gmail dot com
Target Milestone: ---
The following code fails to compile with trunk with -std=c++2a
template<class A, class B>
concept different_than = !__is_same_as(A, B);
template<class B>
auto diff(B) {
return [](different_than<B> auto a) {};
}
int main() {
diff(42)("");
}
By the time the compiler evaluates the constraint, it seems to have forgotten
the context in which the constraint lives; that is, it no longer seems to know
what type B is.
I think the code should compile, and it does with clang-concepts:
https://godbolt.org/z/3QzhxS
