Proposed resolution (October 2003):

At the end of 9.2.4 [dcl.typedef] paragraph 2, add the following:

In a given class scope, a typedef specifier can be used to redefine any class-name declared in that scope that is not also a typedef-name to refer to the type to which it already refers. [Example:

  struct S {
    typedef struct A {} A;  // OK
    typedef struct B B;     // OK
    typedef A A;            // error
  };

]