[Bug c++/114163] New: Calling member function of an incomplete type compiles in gcc and does not compile in clang and msvc

[Bug c++/114163] New: Calling member function of an incomplete type compiles in gcc and does not compile in clang and msvc

[jlame646 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114163

            Bug ID: 114163
           Summary: Calling member function of an incomplete type compiles
                    in gcc and does not compile in clang and msvc
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jlame646 at gmail dot com
  Target Milestone: ---

The following invalid program(since lambda's body in not complete class
context) is compiled by gcc:

```
struct TestClass {
  void testFinction() {}
  static TestClass* ptr_;
  constexpr static auto funcPtr = +[](){ ptr_->testFinction(); };
};

TestClass* TestClass::ptr_ = new TestClass();

int main() {
//   TestClass::funcPtr();
//   delete TestClass::ptr_;
  return 0;
}
```
Demo https://godbolt.org/z/Yhc8MeWW6

First discovered at
https://stackoverflow.com/questions/78080083/calling-member-function-of-an-incomplete-type-compiles-in-gcc-and-does-not-compi

[Bug c++/114163] Calling member function of an incomplete type compiles in gcc and does not compile in clang and msvc

[harald at gigawatt dot nl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114163

Harald van Dijk <harald at gigawatt dot nl> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |harald at gigawatt dot nl

--- Comment #1 from Harald van Dijk <harald at gigawatt dot nl> ---
You may be right that the class is not complete at that point but there is no
requirement for the class to be complete. CWG1836 changed that to "In both
cases, the class type shall be complete unless the class member access appears
in the definition of that class." Here, the class member access does appear in
the definition of the class, so it's okay that the class is incomplete.

[Bug c++/114163] Calling member function of an incomplete type compiles in gcc and does not compile in clang and msvc

[de34 at live dot cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114163

Jiang An <de34 at live dot cn> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |de34 at live dot cn

--- Comment #2 from Jiang An <de34 at live dot cn> ---
May be related to CWG2852.
https://cplusplus.github.io/CWG/issues/2852.html

[Bug c++/114163] Calling member function of an incomplete type compiles in gcc and does not compile in clang and msvc

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114163

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
https://wg21.link/CWG1836
https://eel.is/c++draft/expr.ref#4