[Bug c++/109677] New: Access control bypass for function template default argument brace initialization of private default constructor

[ed at catmur dot uk via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109677

            Bug ID: 109677
           Summary: Access control bypass for function template default
                    argument brace initialization of private default
                    constructor
           Product: gcc
           Version: 13.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ed at catmur dot uk
  Target Milestone: ---

gcc accepts-invalid:

struct B { private: B(); };
template<class T> int f(T = {});
int i = f<B>();

This is mostly a curiosity, but it came up while trying to understand why a
misuse of the passkey pattern was seemingly working.