From eb8c2b30b947dd8a2012ee658117bea05e46bc85 Mon Sep 17 00:00:00 2001
From: Nathan Sidwell <nathan@acm.org>
Date: Thu, 3 Dec 2020 08:58:44 -0800
Subject: [PATCH] c++:  templatey type creation

This patch makes a couple of type-creation routines available to
modules.  That needs to create unbound template parms, and canonical
template parms.

	gcc/cp/
	* cp-tree.h (make_unbound_class_template_raw): Declare.
	(canonical_type_parameter): Declare.
	* decl.c (make_unbound_class_template_raw): Break out of ...
	(make_unboud_class_template): ... here.  Call it.
	* pt.c (canonical_type_parameter): Externalize.  Refactor & set
	structural_equality for type parms.
---
 gcc/cp/cp-tree.h |  2 ++
 gcc/cp/decl.c    |  8 ++++++++
 gcc/cp/pt.c      | 27 ++++++++++++++++-----------
 3 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index de905dcf37c..69f8ed56e62 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -6542,6 +6542,7 @@ extern bool check_omp_return			(void);
 extern tree make_typename_type			(tree, tree, enum tag_types, tsubst_flags_t);
 extern tree build_typename_type			(tree, tree, tree, tag_types);
 extern tree make_unbound_class_template		(tree, tree, tree, tsubst_flags_t);
+extern tree make_unbound_class_template_raw	(tree, tree, tree);
 extern tree build_library_fn_ptr		(const char *, tree, int);
 extern tree build_cp_library_fn_ptr		(const char *, tree, int);
 extern tree push_library_fn			(tree, tree, tree, int);
@@ -6880,6 +6881,7 @@ extern void maybe_show_extern_c_location (void);
 extern bool literal_integer_zerop (const_tree);
 
 /* in pt.c */
+extern tree canonical_type_parameter		(tree);
 extern void push_access_scope			(tree);
 extern void pop_access_scope			(tree);
 extern bool check_template_shadow		(tree);
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 0cf84a0750c..a28e7924869 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -4132,6 +4132,14 @@ make_unbound_class_template (tree context, tree name, tree parm_list,
       return tmpl;
     }
 
+  return make_unbound_class_template_raw (context, name, parm_list);
+}
+
+/* Build an UNBOUND_CLASS_TEMPLATE.  */
+
+tree
+make_unbound_class_template_raw (tree context, tree name, tree parm_list)
+{
   /* Build the UNBOUND_CLASS_TEMPLATE.  */
   tree t = cxx_make_type (UNBOUND_CLASS_TEMPLATE);
   TYPE_CONTEXT (t) = FROB_CONTEXT (context);
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 66ac6473983..3ca28133d94 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -4432,7 +4432,7 @@ build_template_parm_index (int index,
    parameter.  Returns the canonical type parameter, which may be TYPE
    if no such parameter existed.  */
 
-static tree
+tree
 canonical_type_parameter (tree type)
 {
   int idx = TEMPLATE_TYPE_IDX (type);
@@ -13212,19 +13212,24 @@ tsubst_argument_pack (tree orig_arg, tree args, tsubst_flags_t complain,
 		      tree in_decl)
 {
   /* Substitute into each of the arguments.  */
-  tree new_arg = TYPE_P (orig_arg)
-    ? cxx_make_type (TREE_CODE (orig_arg))
-    : make_node (TREE_CODE (orig_arg));
-
   tree pack_args = tsubst_template_args (ARGUMENT_PACK_ARGS (orig_arg),
 					 args, complain, in_decl);
-  if (pack_args == error_mark_node)
-    new_arg = error_mark_node;
-  else
-    SET_ARGUMENT_PACK_ARGS (new_arg, pack_args);
+  tree new_arg = error_mark_node;
+  if (pack_args != error_mark_node)
+    {
+      if (TYPE_P (orig_arg))
+	{
+	  new_arg = cxx_make_type (TREE_CODE (orig_arg));
+	  SET_TYPE_STRUCTURAL_EQUALITY (new_arg);
+	}
+      else
+	{
+	  new_arg = make_node (TREE_CODE (orig_arg));
+	  TREE_CONSTANT (new_arg) = TREE_CONSTANT (orig_arg);
+	}
 
-  if (TREE_CODE (new_arg) == NONTYPE_ARGUMENT_PACK)
-    TREE_CONSTANT (new_arg) = TREE_CONSTANT (orig_arg);
+      SET_ARGUMENT_PACK_ARGS (new_arg, pack_args);
+    }
 
   return new_arg;
 }
-- 
2.30.2