code: func (st *state) nestedName() AST {
  	st.checkChar('N')
  	q := st.cvQualifiers()
  	r := st.refQualifier()
  	a := st.prefix()
  	if len(q) > 0 || r != "" {
  		a = &MethodWithQualifiers{Method: a, Qualifiers: q, RefQualifier: r}
  	}
  	if len(st.str) == 0 || st.str[0] != 'E' {
  		st.fail("expected E after nested name")
  	}
  	st.advance(1)
  	return a
  }
docs: // <nested-name> ::= N [<CV-qualifiers>] [<ref-qualifier>] <prefix> <unqualified-name> E
  //               ::= N [<CV-qualifiers>] [<ref-qualifier>] <template-prefix> <template-args> E