[Bug c++/94422] New: static_cast from std::array to enum class

[vincent.hamp at higaski dot at]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94422

            Bug ID: 94422
           Summary: static_cast from std::array to enum class
           Product: gcc
           Version: 9.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vincent.hamp at higaski dot at
  Target Milestone: ---

static_cast from std::array operator[] to an enum class inside a template class
produces an unexpected expression error. It seems that error is only present in
9.3, 9.2 and trunk work.

#include <array>
#include <cstdint>

enum class EnumC : int8_t { Forward = 1, Backward = -1 };

std::array<uint8_t, sizeof(EnumC)> buf;

template <typename T>
struct S {
  void foo() { auto const cast_to_enum{static_cast<EnumC>(buf[0])}; }
};

S<int> s;