// P1401R5: Narrowing contextual conversions to bool // { dg-do compile { target c++11 } } void f() noexcept(sizeof(char[2])); // { dg-error "narrowing" } conversion of value 2 to type bool void g() noexcept(sizeof(char)); // OK, conversion of value 1 to type bool is non-narrowing #if __cpp_conditional_explicit struct S { explicit(sizeof(char[2])) S(char); // { dg-error "narrowing" "" { target c++20 } } explicit(sizeof(char)) S(bool); // OK, conversion of value 1 to type bool is non-narrowing }; #endif static_assert(sizeof(int[2]), ""); // OK, narrowing allowed #if __cpp_if_constexpr int main() { if constexpr (sizeof(int[2])) // OK, narrowing allowed {} } #endif