re PR c++/80866 (segfault in is_overloaded_fn())

	PR c++/80866
	* parser.c (cp_parser_template_id): Keep the lookup when stashing
	the template_id.

	PR c++/80866
	* g++.dg/parse/pr80866.C: New.

From-SVN: r248377

gcc/cp/ChangeLog

 2017-05-23  Nathan Sidwell  <nathan@acm.org>
 
+	PR c++/80866
+	* parser.c (cp_parser_template_id): Keep the lookup when stashing
+	the template_id.
+
 	* cp-tree.h (DECL_HIDDEN_P): New.
 	* name-lookup.c (set_decl_context,
 	set_local_extern_decl_linkage):	New, broken out of ...

gcc/cp/parser.c

@@ -15570,6 +15570,11 @@ cp_parser_template_id (cp_parser *parser,
 	= make_location (token->location, token->location, finish_loc);
       token->location = combined_loc;
 
+      /* We must mark the lookup as kept, so we don't throw it away on
+	 the first parse.  */
+      if (is_overloaded_fn (template_id))
+	lookup_keep (get_fns (template_id), true);
+
       /* Retrieve any deferred checks.  Do not pop this access checks yet
 	 so the memory will not be reclaimed during token replacing below.  */
       token->u.tree_check_value = ggc_cleared_alloc<struct tree_check> ();

gcc/testsuite/ChangeLog

+2017-05-23  Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/80866
+	* g++.dg/parse/pr80866.C: New.
+
 2017-05-23  Jan Hubicka  <hubicka@ucw.cz>
 
 	* gcc.dg/ipa/ctor-empty-1.c: Update template.

gcc/testsuite/g++.dg/parse/pr80866.C

+// { dg-do compile { target c++11 } }
+// PR 80866 recycled a lookup too soon.
+
+void pow();
+namespace math {
+  template <typename T> void pow(T);
+}
+using namespace math;
+
+decltype(pow<>(0)) z();