[Bug c++/109621] [10/11/12/13/14 Regression] GCC accepts invalid program with multiple using declarations

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109621

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Possibly started with 

    re PR c++/31749 (ICE with invalid redeclaration of builtin)

            PR c++/31749

            gcc/cp/
            * name-lookup.c (do_nonmember_using_decl): Shift implicit type
            declarations into appropriate slots for comparison.  Fix type
            comparison.

            gcc/testsuite/
            * g++.dg/lookup/builtin3.C: New test.
            * g++.dg/lookup/builtin4.C: New test.
            * g++.dg/lookup/using19.C: New test.

    From-SVN: r127600

Or something before that and after r127526.