[Bug c++/109136] New: [concepts] initializer_list constructor constraint should require static_cast for explicit conversion operator

[ldalessandro at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109136

            Bug ID: 109136
           Summary: [concepts] initializer_list constructor constraint
                    should require static_cast for explicit conversion
                    operator
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ldalessandro at gmail dot com
  Target Milestone: ---

The following concept should fail the static_assert, but passes (I should need
a static_cast here).

```
    #include <initializer_list>

    template <class From, class To>
    concept implicit_convertible_to = requires(From x) { 
        std::initializer_list<To>{ x }; 
    };

    struct foo {
        explicit operator int();
    };

    static_assert(implicit_convertible_to<foo, int>);

```

Live: https://godbolt.org/z/GffP9f8o7