Demand for copy constructor definition when mandatory copy elision must take place

[Fedr]

In next code copy constructor shall not be called and checked because of mandatory copy elision:

struct A {       
    consteval A() {}
    consteval A(const A&);
    consteval void f() {}
};

int main() {
    A{A{}}.f();
}

GCC and MSVC accept the code. But Clang does not:

undefined constructor 'A' cannot be used in a constant expression

Demo: https://gcc.godbolt.org/z/cKboT3qf6

[llvmbot]

@llvm/issue-subscribers-clang-frontend

[Izaron]

Proposed fix at https://reviews.llvm.org/D119095

[usx95]

This is essentially an assertion failure as in #53244. (https://godbolt.org/z/n1G5bjzfr)
Duplicate of #53244