Alt text:
A screenshot from the linked article titled “Reflection in C++26”, showing reflection as one of the bullet points listed in the “Core Language” section
A screenshot from the linked article titled “Reflection in C++26”, showing reflection as one of the bullet points listed in the “Core Language” section
You already can do that with C++20 concepts and the requires expression
template <typename T> concept has_member_foo = requires(T t) { t.foo(); }; // Will fail to instantiate (with nice error // message) if t.foo() is ill-formed template <has_member_foo T> void bar(T t) { // ... } // abbreviated form of above void baz(has_member_foo auto t) { // ... } // verbose form of above template <typename T> requires has_member_foo<T> void biz(T t) { // ... } // same as above but with anonymous concept template <typename T> requires requires(T t) { t.foo(); } void bom(T t) { // ... } // If already inside a function if constexpr (has_member_foo<T>) { // ... } // Same but with anonymous concept if constexpr (requires(T t) { t.foo(); }) { // ... }I imagine reflections would make the process more straightforward, requires expressions are powerful but either somewhat verbose or possibly incomplete.
For instance, in your example
foocould have any of the following declarations in a class:void foo();int foo() const;template <typename T> foo(T = { }) &&;decltype([]() { }) foo;