https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109745
albin <albin at yahoo dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |albin at yahoo dot com --- Comment #2 from albin <albin at yahoo dot com> --- Simpler example: #include <cassert> template <typename T> struct Foo { T val; }; class Bar { public: constexpr Bar() = default; constexpr Bar(Bar const& other) { other.val_ = 42; } constexpr int val() const { return val_; } private: mutable int val_{}; }; int main() { constexpr Foo<Bar> x{}; Foo<Bar> y{x}; assert(x.val.val() == 42); }