6 Basics [basic]

6.4 Scope [basic.scope]

6.4.7 Class scope [basic.scope.class]

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Any declaration of a class or class template C introduces a class scope that includes the member-specification of the class-specifier for C (if any).
For each non-friend redeclaration or specialization whose target scope is or is contained by the scope, the portion after the declarator-id, class-head-name, or enum-head-name is also included in the scope.
[Note 1: 
Lookup from a program point before the class-specifier of a class will find no bindings in the class scope.
[Example 1: template<class D> struct B { D::type x; // #1 }; struct A { using type = int; }; struct C : A, B<C> {}; // error at #1: C​::​type not found — end example]
— end note]