hubert.reinterpretcast added a comment. I am concerned that the general direction of this patch (to allow the previously ill-formed constexpr functions as an extension under older language levels) is based upon bugs/divergences-from-orthodoxy in Clang's implementation of C++20 (noting that the committee discussion did not agree with Clang's split between the template and non-template cases).
Evaluating "an invocation of an instantiated constexpr function that fails to satisfy the requirements for a constexpr function" causes an expression to not be a core constant expression. The ability to SFINAE on this can be demonstrated using GCC. For the following case under C++20, GCC finds that the template candidate suffers from substitution failure (Clang doesn't): https://godbolt.org/z/h71ffYafM struct NonLiteral { NonLiteral(); operator int(); } *pNL = 0; template <typename T, T> struct ValueSink; template <typename T> struct A { constexpr int f() { return 42; T t; } }; short *f(void *); template <typename T> long *f(T *, ValueSink<int, A<T>().f()> * = 0); using retty = decltype(f(pNL)); typedef short *retty; Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D111400/new/ https://reviews.llvm.org/D111400 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
