https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105623
Bug ID: 105623
Summary: [12/13 regression][rejects valid] invalid use of auto
when deducing return type of base class template
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: hello at josephloser dot com
Target Milestone: ---
The following code used to work in GCC 11.3.0, but fails on GCC 12.1.0 and
trunk.
```
#include <string_view>
constexpr auto g(auto name_fn) {
return name_fn();
}
template <char... Cs> struct ct_string {
static constexpr char str[] = {Cs..., 0};
static constexpr auto name() { return std::string_view{str, sizeof...(Cs)};
}
};
struct S : ct_string<'f', 'o', 'o'> {
constexpr auto f() {
return g(name);
}
};
int main() {
{
S s;
[[maybe_unused]] constexpr auto name = s.f();
}
return 0;
}
```
This code works on GCC 11.3.0 but fails on GCC 12.1.0 onward, including trunk.
See it live at https://godbolt.org/z/9c8vb1eP5
One workaround is to explicitly provide the return type for `ct_string::foo`
static function such as at https://godbolt.org/z/ccqPxoM5P which works on GCC
11.3.0, 12.1.0, and trunk.
