[Bug c++/96957] New: No name-lookup into base class when using an non dependent base class via template alias with dummy parameter.

[anders.granlund.0 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96957

            Bug ID: 96957
           Summary: No name-lookup into base class when using an non
                    dependent base class via template alias with dummy
                    parameter.
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: anders.granlund.0 at gmail dot com
  Target Milestone: ---

Consider the following c++ program:

  class A
  {
      protected:
          int x;
  };

  template<typename X>
  using B = A;

  template<typename T>
  class C : public B<T>
  {
      public:
          void f()
          {
              x = 0;
          }
  };

  int main()
  {
  }

Compile it with "-std=c++17 -pedantic-errors".

Expected behaviour:

  Since the base class is not dependent (see http://wg21.link/cwg1390 ) the
  name lookup of x should succeed and no error message should be outputed
  during the compilation.

Observed behaviour:

  An compilation error about failing the name lookup of x was outputed during
  the compilation.

GCC is correctly compiling the program with no error messages outputed. See the
discussion in: https://bugs.llvm.org/show_bug.cgi?id=47435