The following code fails to compile with the error no member named 'foo' in 'B' despite that only being an issue within a context that should be discarded at compile time.

#include <type_traits>

struct A {
    int foo() {
        return 1;
    }
};

struct B {
    int bar() {
        return 2;
    }
};

static constexpr bool TEST = false;
using T = std::conditional_t<TEST, A, B>;

int main() {
    T t{};
    if constexpr (TEST) {
        return t.foo();
    } else {
        return t.bar();
    }
}

What can I do to enable code like this? If I were to replace the constexpr with preprocessor macros this would likely work just fine, no?