[Bug c++/100032] New: renaming alias template that also adds cv-qualifiers is deemed equivalent to underlying template

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100032

            Bug ID: 100032
           Summary: renaming alias template that also adds cv-qualifiers
                    is deemed equivalent to underlying template
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ppalka at gcc dot gnu.org
  Target Milestone: ---

DR 1286 allows alias templates to be equivalent to the underlying template if
the alias is just a renaming of the underlying template.  In the testcase
below, Z is arguably not equivalent to Y because of the added const qualifier,
but GCC still deems them equivalent, and accepts the testcase.

template <template<class> class> struct X { };
template <class> struct Y { };
template <class T> using Z = const Y<T>;
using T = X<Y>;
using T = X<Z>;