[Bug c++/97399] [9/10/11 Regression] g++ 9.3 cannot compile SFINAE code with separated declaration and definition, g++ 7.3 compiles

["ppalka at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97399

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |ppalka at gcc dot gnu.org
                 CC|                            |ppalka at gcc dot gnu.org

--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
The alias template in the reduced testcase is a red herring, the ICE can be
reproduced without it:

template <bool> struct enable_if_t {};
struct tmp {
  template <class> static constexpr bool is_integral();
  template <class E>
  static auto func(E, E) -> enable_if_t<tmp::is_integral<E>()>;
};
template <class> constexpr bool tmp::is_integral() { return true; }
int main() { tmp::func(1, 0); }


Looks like the problematic hunk from r9-5972 is

--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -2096,7 +2096,8 @@ finish_qualified_id_expr (tree qualifying_class,
     {
       /* See if any of the functions are non-static members.  */
       /* If so, the expression may be relative to 'this'.  */
-      if (!shared_member_p (expr)
+      if ((type_dependent_expression_p (expr)
+          || !shared_member_p (expr))
          && current_class_ptr
          && DERIVED_FROM_P (qualifying_class,
                             current_nonlambda_class_type ()))