From 4602a494e94835f693a9230adb69ce92249ebf15 Mon Sep 17 00:00:00 2001
From: Marek Polacek <polacek@redhat.com>
Date: Tue, 22 Feb 2022 15:03:34 -0500
Subject: [PATCH] c++: ->template and implicit typedef [PR104608]

Here we have a forward declaration of Parameter for which we create
an implicit typedef, which is a TYPE_DECL.  Then, when looking it up
at template definition time, cp_parser_template_id gets (since r12-6754)
this TYPE_DECL which it can't handle.

This patch defers lookup for TYPE_DECLs that cp_parser_template_id can't
handle, a la r12-6879.

	PR c++/104608

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_template_name): Repeat lookup of
	TYPE_DECLs.

gcc/testsuite/ChangeLog:

	* g++.dg/parse/template-keyword3.C: New test.
	* g++.dg/parse/template-keyword4.C: New test.
---
 gcc/cp/parser.cc                               |  5 ++++-
 gcc/testsuite/g++.dg/parse/template-keyword3.C | 12 ++++++++++++
 gcc/testsuite/g++.dg/parse/template-keyword4.C | 17 +++++++++++++++++
 3 files changed, 33 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/parse/template-keyword3.C
 create mode 100644 gcc/testsuite/g++.dg/parse/template-keyword4.C

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 18db9d40a01..87b9781e793 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -18674,7 +18674,10 @@ cp_parser_template_name (cp_parser* parser,
 	  return error_mark_node;
 	}
       else if ((!DECL_P (decl) && !is_overloaded_fn (decl))
-	       || TREE_CODE (decl) == USING_DECL)
+	       || TREE_CODE (decl) == USING_DECL
+	       /* cp_parser_template_id can only handle some TYPE_DECLs.  */
+	       || (TREE_CODE (decl) == TYPE_DECL
+		   && TREE_CODE (TREE_TYPE (decl)) != TYPENAME_TYPE))
 	/* Repeat the lookup at instantiation time.  */
 	decl = identifier;
     }
diff --git a/gcc/testsuite/g++.dg/parse/template-keyword3.C b/gcc/testsuite/g++.dg/parse/template-keyword3.C
new file mode 100644
index 00000000000..59fe0fc180b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/parse/template-keyword3.C
@@ -0,0 +1,12 @@
+// PR c++/104608
+
+class Parameter;
+template <typename R> class Function 
+: public R  
+{
+    Function();
+};
+template <typename R>
+Function<R>::Function() {
+    this->template Parameter<R>();
+}
diff --git a/gcc/testsuite/g++.dg/parse/template-keyword4.C b/gcc/testsuite/g++.dg/parse/template-keyword4.C
new file mode 100644
index 00000000000..c688094bcf2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/parse/template-keyword4.C
@@ -0,0 +1,17 @@
+// PR c++/104608
+// { dg-do compile { target c++11 } }
+
+class S;
+using Parameter = S;
+typedef S Parameter2;
+
+template <typename R> class Function 
+: public R  
+{
+    Function();
+};
+template <typename R>
+Function<R>::Function() {
+    this->template Parameter<R>();
+    this->template Parameter2<R>();
+}