Can a member of a class be named the same name as its type (another class)?

Question

Trying to compile the following code on different compilers gives me two different results:

struct S{};
struct T{S S;};
int main(){}

As you

Answer 1

gcc is correct, from [3.3.7 Class Scope]

A name N used in a class S shall refer to the same declaration in its context and when re-evaluated in the completed scope of S. No diagnostic is required for a violation of this rule.

However, note that no diagnostic is required, so all compilers are conforming.

The reason is because of how class scope works. When you write S S; S is visible within the entire class and changes the meaning when you use S.

struct S{};
struct T{
    void foo()
    { 
        S myS; // Not possible anymore because S refers to local S
    }
    S S;
};