c++: Implement __is_nothrow_constructible and __is_nothrow_assignable

gcc/c-family/ChangeLog:

	* c-common.c (__is_nothrow_assignable): New.
	(__is_nothrow_constructible): Likewise.
	* c-common.h (RID_IS_NOTHROW_ASSIGNABLE): New.
	(RID_IS_NOTHROW_CONSTRUCTIBLE): Likewise.

gcc/cp/ChangeLog:

	* cp-tree.h (CPTK_IS_NOTHROW_ASSIGNABLE): New.
	(CPTK_IS_NOTHROW_CONSTRUCTIBLE): Likewise.
	(is_nothrow_xible): Likewise.
	* method.c (is_nothrow_xible): New.
	(is_trivially_xible): Tweak.
	* parser.c (cp_parser_primary_expression): Handle the new RID_*.
	(cp_parser_trait_expr): Likewise.
	* semantics.c (trait_expr_value): Handle the new RID_*.
	(finish_trait_expr): Likewise.

libstdc++-v3/ChangeLog:

	* include/std/type_traits (__is_nt_constructible_impl): Remove.
	(__is_nothrow_constructible_impl): Adjust.
	(is_nothrow_default_constructible): Likewise.
	(__is_nt_assignable_impl): Remove.
	(__is_nothrow_assignable_impl): Adjust.

4 files changed, 36 insertions, 4 deletions

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 5c06ac3..1ce2098 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -1323,7 +1323,9 @@ enum cp_trait_kind
   CPTK_IS_UNION,
   CPTK_UNDERLYING_TYPE,
   CPTK_IS_ASSIGNABLE,
-  CPTK_IS_CONSTRUCTIBLE
+  CPTK_IS_CONSTRUCTIBLE,
+  CPTK_IS_NOTHROW_ASSIGNABLE,
+  CPTK_IS_NOTHROW_CONSTRUCTIBLE
 };
 
 /* The types that we are processing.  */
@@ -6752,6 +6754,7 @@ extern void use_thunk				(tree, bool);
 extern bool trivial_fn_p			(tree);
 extern tree forward_parm			(tree);
 extern bool is_trivially_xible			(enum tree_code, tree, tree);
+extern bool is_nothrow_xible			(enum tree_code, tree, tree);
 extern bool is_xible				(enum tree_code, tree, tree);
 extern tree get_defaulted_eh_spec		(tree, tsubst_flags_t = tf_warning_or_error);
 extern bool maybe_explain_implicit_delete	(tree);
diff --git a/gcc/cp/method.c b/gcc/cp/method.c
index 6e4c5f7..16e7635 100644
--- a/gcc/cp/method.c
+++ b/gcc/cp/method.c
@@ -1924,15 +1924,26 @@ is_xible_helper (enum tree_code code, tree to, tree from, bool trivial)
 bool
 is_trivially_xible (enum tree_code code, tree to, tree from)
 {
-  tree expr;
-  expr = is_xible_helper (code, to, from, /*trivial*/true);
-
+  tree expr = is_xible_helper (code, to, from, /*trivial*/true);
   if (expr == NULL_TREE || expr == error_mark_node)
     return false;
   tree nt = cp_walk_tree_without_duplicates (&expr, check_nontriv, NULL);
   return !nt;
 }
 
+/* Returns true iff TO is nothrow assignable (if CODE is MODIFY_EXPR) or
+   constructible (otherwise) from FROM, which is a single type for
+   assignment or a list of types for construction.  */
+
+bool
+is_nothrow_xible (enum tree_code code, tree to, tree from)
+{
+  tree expr = is_xible_helper (code, to, from, /*trivial*/false);
+  if (expr == NULL_TREE || expr == error_mark_node)
+    return false;
+  return expr_noexcept_p (expr, tf_none);
+}
+
 /* Returns true iff TO is assignable (if CODE is MODIFY_EXPR) or
    constructible (otherwise) from FROM, which is a single type for
    assignment or a list of types for construction.  */
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 7ec7d42..cce3d0a 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -5637,6 +5637,8 @@ cp_parser_primary_expression (cp_parser *parser,
 	case RID_IS_UNION:
 	case RID_IS_ASSIGNABLE:
 	case RID_IS_CONSTRUCTIBLE:
+	case RID_IS_NOTHROW_ASSIGNABLE:
+	case RID_IS_NOTHROW_CONSTRUCTIBLE:
 	  return cp_parser_trait_expr (parser, token->keyword);
 
 	// C++ concepts
@@ -10501,6 +10503,14 @@ cp_parser_trait_expr (cp_parser* parser, enum rid keyword)
       kind = CPTK_IS_CONSTRUCTIBLE;
       variadic = true;
       break;
+    case RID_IS_NOTHROW_ASSIGNABLE:
+      kind = CPTK_IS_NOTHROW_ASSIGNABLE;
+      binary = true;
+      break;
+    case RID_IS_NOTHROW_CONSTRUCTIBLE:
+      kind = CPTK_IS_NOTHROW_CONSTRUCTIBLE;
+      variadic = true;
+      break;
     default:
       gcc_unreachable ();
     }
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 1e42cd7..ac48847 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -10133,6 +10133,12 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_CONSTRUCTIBLE:
       return is_xible (INIT_EXPR, type1, type2);
 
+    case CPTK_IS_NOTHROW_ASSIGNABLE:
+      return is_nothrow_xible (MODIFY_EXPR, type1, type2);
+
+    case CPTK_IS_NOTHROW_CONSTRUCTIBLE:
+      return is_nothrow_xible (INIT_EXPR, type1, type2);
+
     default:
       gcc_unreachable ();
       return false;
@@ -10213,6 +10219,8 @@ finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2)
 
     case CPTK_IS_TRIVIALLY_ASSIGNABLE:
     case CPTK_IS_TRIVIALLY_CONSTRUCTIBLE:
+    case CPTK_IS_NOTHROW_ASSIGNABLE:
+    case CPTK_IS_NOTHROW_CONSTRUCTIBLE:
       if (!check_trait_type (type1)
 	  || !check_trait_type (type2))
 	return error_mark_node;