[Bug c++/126149] New: GCC rejects valid program with auto used in decltype

[jlame646 at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126149

            Bug ID: 126149
           Summary: GCC rejects valid program with auto used in decltype
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jlame646 at gmail dot com
  Target Milestone: ---

The following valid program is rejected by all three compilers(including gcc):
```
struct NoMove {
    NoMove(NoMove&&) = delete;
};

NoMove&& DeclVal();
void     F1(...);
void     F2(auto);

using Type1 = decltype(F1(DeclVal()));   // #1: this compiles 
using Type2 = decltype(F2(DeclVal()));   // #2: this doesn't compile when it
should
```