Support using 'auto' in a function parameter list to introduce an implicit template parameter.

	* cp-tree.h (type_uses_auto_or_concept): Declare.
	(is_auto_or_concept): Declare.
	* decl.c (grokdeclarator): Allow 'auto' parameters in lambdas with
	-std=gnu++1y or -std=c++1y or, as a GNU extension, in plain functions.
	* type-utils.h: New header defining ...
	(find_type_usage): ... this new function based on pt.c (type_uses_auto)
	for searching a type tree given a predicate.
	* pt.c (type_uses_auto): Reimplement via type-utils.h (find_type_usage).
	(is_auto_or_concept): New function.
	(type_uses_auto_or_concept): New function.
	* parser.h (struct cp_parser): Add fully_implicit_function_template_p.
	* parser.c (cp_parser_new): Initialize fully_implicit_function_template_p.
	(cp_parser_new): Initialize fully_implicit_function_template_p.
	(cp_parser_lambda_expression): Copy and restore value of
	fully_implicit_function_template_p as per other parser fields.
	(cp_parser_parameter_declaration_list): Count generic
	parameters and call ...
	(add_implicit_template_parms): ... this new function to synthesize them
	with help from type-utils.h (find_type_usage), ...
	(tree_type_is_auto_or_concept): ... this new static function and ...
	(make_generic_type_name): ... this new static function.
	(cp_parser_direct_declarator): Account for implicit template parameters.
	(cp_parser_lambda_declarator_opt): Finish fully implicit template if
	necessary by calling ...
	(finish_fully_implicit_template): ... this new function.
	(cp_parser_member_declaration): Likewise.
	(cp_parser_function_definition_after_declarator): Likewise.
	* Make-lang.in (cp/pt.o): Add dependency on type-utils.h.
	(cp/parser.o): Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@202540 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 20 insertions, 15 deletions

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 93e6258bd63..de1022efec2 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -41,6 +41,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "toplev.h"
 #include "timevar.h"
 #include "tree-iterator.h"
+#include "type-utils.h"
 
 /* The type of functions taking a tree, and some additional data, and
    returning an int.  */
@@ -21110,31 +21111,35 @@ is_auto (const_tree type)
     return false;
 }
 
-/* Returns true iff TYPE contains a use of 'auto'.  Since auto can only
-   appear as a type-specifier for the declaration in question, we don't
-   have to look through the whole type.  */
+/* Returns the TEMPLATE_TYPE_PARM in TYPE representing `auto' iff TYPE contains
+   a use of `auto'.  Returns NULL_TREE otherwise.  */
 
 tree
 type_uses_auto (tree type)
 {
-  enum tree_code code;
-  if (is_auto (type))
-    return type;
+  return find_type_usage (type, is_auto);
+}
 
-  code = TREE_CODE (type);
+/* Returns true iff TYPE is a TEMPLATE_TYPE_PARM representing 'auto',
+   'decltype(auto)' or a concept.  */
 
-  if (code == POINTER_TYPE || code == REFERENCE_TYPE
-      || code == OFFSET_TYPE || code == FUNCTION_TYPE
-      || code == METHOD_TYPE || code == ARRAY_TYPE)
-    return type_uses_auto (TREE_TYPE (type));
+bool
+is_auto_or_concept (const_tree type)
+{
+  return is_auto (type); // or concept
+}
 
-  if (TYPE_PTRMEMFUNC_P (type))
-    return type_uses_auto (TREE_TYPE (TREE_TYPE
-				   (TYPE_PTRMEMFUNC_FN_TYPE (type))));
+/* Returns the TEMPLATE_TYPE_PARM in TYPE representing a generic type (`auto' or
+   a concept identifier) iff TYPE contains a use of a generic type.  Returns
+   NULL_TREE otherwise.  */
 
-  return NULL_TREE;
+tree
+type_uses_auto_or_concept (tree type)
+{
+  return find_type_usage (type, is_auto_or_concept);
 }
 
+
 /* For a given template T, return the vector of typedefs referenced
    in T for which access check is needed at T instantiation time.
    T is either  a FUNCTION_DECL or a RECORD_TYPE.