[Bug c++/105320] New: Use of shared_ptr within a type exported from a module results in spurious compiler error

["john at johnmaddock dot co.uk" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105320

            Bug ID: 105320
           Summary: Use of shared_ptr within a type exported from a module
                    results in spurious compiler error
           Product: gcc
           Version: 11.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: john at johnmaddock dot co.uk
  Target Milestone: ---

Reduced test case:

module.cpp:
module;

#include <memory>

export module test_support;

export template <class T> struct pimpl
{
private:
   std::shared_ptr<T> data;
public:
   pimpl(const T& x) : data(new T(x)) {}
   pimpl() = default;
};


test_module.cpp:
import test_support;

int main()
{
   pimpl<int> p1, p2(3);
}

Compile with:
g++ -std=gnu++20 -fmodules-ts module.cpp test_module.cpp

Results in:
D:/compilers/msys64/mingw64/include/c++/11.2.0/bits/shared_ptr_base.h:1369:
confused by earlier errors, bailing out

Note that there were no earlier errors ! ;)