Revert "c++: delayed parse DMI [PR96645]"

The breakage from r12-7804 (in WebKit, particularly) is more of a can of
worms than I think we can address in GCC 12, so let's return to the GCC 11
status quo for now and try again in stage 1.

I think the change was correct for the current standard, but the standard
needs a fix in this area; this is CWG issue 2335.

	PR c++/96645

This reverts commits r12-7804 and r12-7929.

1 files changed, 0 insertions, 24 deletions

diff --git a/gcc/cp/method.cc b/gcc/cp/method.cc
index e0fe217..903ee66 100644
--- a/gcc/cp/method.cc
+++ b/gcc/cp/method.cc
@@ -2056,28 +2056,6 @@ assignable_expr (tree to, tree from)
   return r;
 }
 
-/* An unparsed default member initializer prevents calling a defaulted default
-   constructor; make checking std::is_constructible ill-formed until the DMI
-   has been parsed, to avoid caching the wrong value.  */
-
-static bool
-complain_about_unparsed_dmi (tree t)
-{
-  if (type_has_default_ctor_to_be_synthesized (t)
-      && TYPE_HAS_COMPLEX_DFLT (t))
-    for (tree f = TYPE_FIELDS (t); f; f = DECL_CHAIN (f))
-      if (TREE_CODE (f) == FIELD_DECL
-	  && DECL_INITIAL (f)
-	  && TREE_CODE (DECL_INITIAL (f)) == DEFERRED_PARSE)
-	{
-	  error ("default member initializer for %qD required by %qs before "
-		 "the end of its enclosing class", f, "std::is_constructible");
-	  inform (location_of (f), "defined here");
-	  return true;
-	}
-  return false;
-}
-
 /* The predicate condition for a template specialization
    is_constructible<T, Args...> shall be satisfied if and only if the
    following variable definition would be well-formed for some invented
@@ -2092,8 +2070,6 @@ constructible_expr (tree to, tree from)
   cp_unevaluated cp_uneval_guard;
   if (CLASS_TYPE_P (to))
     {
-      if (!from && complain_about_unparsed_dmi (to))
-	return error_mark_node;
       tree ctype = to;
       vec<tree, va_gc> *args = NULL;
       if (!TYPE_REF_P (to))