[Bug c++/114183] New: Lambda constexpr works in msvc but not in gcc

["jlame646 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114183

            Bug ID: 114183
           Summary: Lambda constexpr works in msvc but not in gcc
           Product: gcc
           Version: 14.0
            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(afaik) program is rejected by gcc:
https://godbolt.org/z/xhes5fvoc

```
int main() {
    constexpr auto func = []()constexpr { return 1; };
    auto i = []{return func();};
}   

```

GCC says:

```
<source>: In lambda function:
<source>:3:28: error: 'func' is not captured
    3 |     auto i = []{return func();};
      |                        ~~~~^~
<source>:3:15: note: the lambda has no capture-default
    3 |     auto i = []{return func();};
      |               ^
<source>:2:20: note: 'constexpr const main()::<lambda()> func' declared here
    2 |     constexpr auto func = []()constexpr { return 1; };
      |
```

https://en.cppreference.com/w/cpp/language/lambda says:

> A lambda expression can read the value of a variable without capturing it if the variable
> is constexpr and has no mutable members.