[Bug c++/117106] [12/13/14/15 Regression] ICE when a "deducing this" function with noexcept specification is used before the class is complete

[fchelnokov at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117106

--- Comment #3 from Fedor Chelnokov <fchelnokov at gmail dot com> ---
(comment #1 corrected)
> This crash is reproducible in C++20 mode as well without deducing this:
```
struct A {
    int x;
    template<class>
    void foo() noexcept(noexcept(x)) {}
    auto bar() -> decltype(foo<int>()) {}
};
```