clang incorrectly accepts non-constant consteval function calls in destructor

[kelbon]

https://godbolt.org/z/MzaPMraqK

This code incorrectly produces runtime error instead of compilation error in checking fmt::format string

#include <fmt/core.h>

template<typename T>
struct scope_exit {
   T val;
constexpr ~scope_exit() {  val(); }
};

int main() {
  scope_exit x([]() { std::string s = fmt::format("{}"); });
}

[kelbon]

https://godbolt.org/z/TTncxY6nP

produces runtime segfault with std::format

[frederick-vs-ja]

Reduced example (Godbolt link):

struct fmt_str_like {
  static void non_constexpr_error() {}

  consteval fmt_str_like(const char* ptr) {
    if (!ptr)
      non_constexpr_error();
  }
};

void fmt_like(fmt_str_like) {}

template<typename T>
struct scope_exit {
  T ftor_;

  constexpr ~scope_exit() {
    ftor_();
  }
};

int main() {
  scope_exit guard([]() { fmt_like(nullptr); });
}

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: None (kelbon)

https://godbolt.org/z/MzaPMraqK

This code incorrectly produces runtime error instead of compilation error in checking fmt::format string

#include <fmt/core.h>

template<typename T>
struct scope_exit {
   T val;
constexpr ~scope_exit() {  val(); }
};

int main() {
  scope_exit x([]() { std::string s = fmt::format("{}"); });
}

[kelbon]

Any updates?

[kelbon]

clang 21 have this issue too

[tbaederr]

maybe @cor3ntin has an idea?

[cor3ntin]

Interestingly, it only happens in a template https://godbolt.org/z/qTs3fhY38