c++: Fix ICE with concepts and aliases [PR93907].

The problem here was that we were checking satisfaction once with 'e', a
typedef of 'void', and another time with 'void' directly, and treated them
as different for hashing based on the assumption that
canonicalize_type_argument would have already removed a typedef that wasn't
a complex dependent alias.  But that wasn't happening here, so let's add a
call.

gcc/cp/ChangeLog
2020-03-11  Jason Merrill  <jason@redhat.com>

	PR c++/93907
	* constraint.cc (tsubst_parameter_mapping): Canonicalize type
	argument.

gcc/cp/ChangeLog

+2020-03-11  Jason Merrill  <jason@redhat.com>
+
+	PR c++/93907
+	* constraint.cc (tsubst_parameter_mapping): Canonicalize type
+	argument.
+
 2020-03-11  Marek Polacek  <polacek@redhat.com>
 	    Jason Merrill  <jason@redhat.com>
 

gcc/cp/constraint.cc

@@ -2232,7 +2232,11 @@ tsubst_parameter_mapping (tree map, tree args, subst_info info)
       else if (ARGUMENT_PACK_P (arg))
 	new_arg = tsubst_argument_pack (arg, args, complain, in_decl);
       if (!new_arg)
+	{
 	  new_arg = tsubst_template_arg (arg, args, complain, in_decl);
+	  if (TYPE_P (new_arg))
+	    new_arg = canonicalize_type_argument (new_arg, complain);
+	}
       if (new_arg == error_mark_node)
 	return error_mark_node;
 

gcc/cp/cp-tree.h

@@ -7016,6 +7016,7 @@ extern tree resolve_nondeduced_context_or_error	(tree, tsubst_flags_t);
 extern hashval_t iterative_hash_template_arg (tree arg, hashval_t val);
 extern tree coerce_template_parms               (tree, tree, tree);
 extern tree coerce_template_parms               (tree, tree, tree, tsubst_flags_t);
+extern tree canonicalize_type_argument		(tree, tsubst_flags_t);
 extern void register_local_specialization       (tree, tree);
 extern tree retrieve_local_specialization       (tree);
 extern tree extract_fnparm_pack                 (tree, tree *);

gcc/cp/pt.c

@@ -7943,7 +7943,7 @@ template_template_parm_bindings_ok_p (tree tparms, tree targs)
 /* Since type attributes aren't mangled, we need to strip them from
    template type arguments.  */
 
-static tree
+tree
 canonicalize_type_argument (tree arg, tsubst_flags_t complain)
 {
   if (!arg || arg == error_mark_node || arg == TYPE_CANONICAL (arg))

gcc/testsuite/g++.dg/cpp2a/concepts-using2.C

+// PR c++/93907
+// { dg-options -std=gnu++20 }
+
+template <int a> struct c {
+  static constexpr int d = a;
+  typedef c e;
+};
+template <typename> struct f;
+template <typename b> using g = typename f<b>::e;
+struct b;
+template <typename b> struct f { using e = b; };
+template <typename ai> struct m { typedef g<ai> aj; };
+template <typename b> class n { typedef typename m<b>::aj e; };
+template <typename b> using an = typename n<b>::e;
+template <typename> constexpr bool ao = c<true>::d;
+template <typename> constexpr bool i = c<1>::d;
+template <typename> concept bb = i<b>;
+using cc = __int128;
+template <typename> concept cd = bb<cc>;
+template <typename bt> concept ce = requires { requires cd<bt>; };
+template <typename bt> concept h = ce<bt>;
+template <typename bt> concept l = h<bt>;
+template <typename> concept cl = ao<b>;
+template <typename b> concept cp = requires(b j) {
+  requires h<an<decltype(j.begin())>>;
+};
+struct o {
+  template <cl b> requires cp<b> auto operator()(b) {}
+};
+template <typename b> using cm = decltype(o{}(b()));
+template <typename bt> concept ct = l<bt>;
+template <typename da> concept dd = ct<cm<da>>;
+template <typename da> concept de = dd<da>;
+struct {
+  template <de da, typename b> void operator()(da, b);
+} di;
+class p {
+  void begin();
+};
+template <typename> using df = p;
+template <int> void q() {
+  df<int> k;
+  int d;
+  di(k, d);
+}