[Bug c++/101873] New: Compilation error of valid code with return local variable in C++20 mode

[fchelnokov at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101873

            Bug ID: 101873
           Summary: Compilation error of valid code with return local
                    variable in C++20 mode
           Product: gcc
           Version: 11.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fchelnokov at gmail dot com
  Target Milestone: ---

The program as follows fails to compile in C++20 mode:
```
struct U {
    U(int) {}
    U(int&&) {}
};

U foo(int a = 0) { return a; }

int main() { foo(); }
```
But it is a valid program and other compilers accept it:
https://gcc.godbolt.org/z/fMvEPMGhq