From eedaaaf7d7892011245b1e2054ca917c6d81c213 Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Thu, 1 Mar 2018 14:40:36 -0500
Subject: [PATCH] PR c++/71569 - decltype of template.

	* parser.c (cp_parser_decltype_expr): Handle missing template args.

From-SVN: r258110
---
 gcc/cp/ChangeLog                            |  5 +++++
 gcc/cp/parser.c                             |  7 +++++++
 gcc/testsuite/g++.dg/cpp0x/decltype-33837.C |  4 ++--
 gcc/testsuite/g++.dg/cpp0x/decltype43.C     |  2 +-
 gcc/testsuite/g++.dg/cpp1y/var-templ59.C    | 14 ++++++++++++++
 5 files changed, 29 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1y/var-templ59.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index acaabd0e197..df5f48c845b 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2018-03-01  Jason Merrill  <jason@redhat.com>
+
+	PR c++/71569 - decltype of template.
+	* parser.c (cp_parser_decltype_expr): Handle missing template args.
+
 2018-03-01  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/84596
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 359460cd4d8..e1acb07d29e 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -13983,6 +13983,10 @@ cp_parser_decltype_expr (cp_parser *parser,
 	expr = cp_parser_lookup_name_simple (parser, expr,
 					     id_expr_start_token->location);
 
+      if (expr && TREE_CODE (expr) == TEMPLATE_DECL)
+	/* A template without args is not a complete id-expression.  */
+	expr = error_mark_node;
+
       if (expr
           && expr != error_mark_node
           && TREE_CODE (expr) != TYPE_DECL
@@ -14048,6 +14052,9 @@ cp_parser_decltype_expr (cp_parser *parser,
          expression.  */
       cp_parser_abort_tentative_parse (parser);
 
+      /* Commit to the tentative_firewall so we get syntax errors.  */
+      cp_parser_commit_to_tentative_parse (parser);
+
       /* Parse a full expression.  */
       expr = cp_parser_expression (parser, /*pidk=*/NULL, /*cast_p=*/false,
 				   /*decltype_p=*/true);
diff --git a/gcc/testsuite/g++.dg/cpp0x/decltype-33837.C b/gcc/testsuite/g++.dg/cpp0x/decltype-33837.C
index fbbc6a14972..4a8f053234e 100644
--- a/gcc/testsuite/g++.dg/cpp0x/decltype-33837.C
+++ b/gcc/testsuite/g++.dg/cpp0x/decltype-33837.C
@@ -2,6 +2,6 @@
 // PR c++/33837
 void foo()
 {
-  __decltype (A::foo()); // { dg-error "was not declared|expected" }
-  __decltype (B); // { dg-error "was not declared" }
+  __decltype (A::foo()); // { dg-error "A" }
+  __decltype (B); // { dg-error "B" }
 }
diff --git a/gcc/testsuite/g++.dg/cpp0x/decltype43.C b/gcc/testsuite/g++.dg/cpp0x/decltype43.C
index 4df95a1047c..7a1dcbf8744 100644
--- a/gcc/testsuite/g++.dg/cpp0x/decltype43.C
+++ b/gcc/testsuite/g++.dg/cpp0x/decltype43.C
@@ -22,6 +22,6 @@ struct B
 int main()
 {
   int x = B<decltype(A<int>::a(1))>::b(A<int>::a(1));
-  int y = B<decltype(A     ::a(2))>::b(A<int>::a(2)); // { dg-error "template argument" }
+  int y = B<decltype(A     ::a(2))>::b(A<int>::a(2)); // { dg-error "template" }
   return x + y;
 }
diff --git a/gcc/testsuite/g++.dg/cpp1y/var-templ59.C b/gcc/testsuite/g++.dg/cpp1y/var-templ59.C
new file mode 100644
index 00000000000..da9710e1ce4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/var-templ59.C
@@ -0,0 +1,14 @@
+// PR c++/71569
+// { dg-do compile { target c++14 } }
+
+template <class T>
+struct A {
+  template <class U>
+  static U u;
+};
+
+int main()
+{
+  decltype(A<int>::u) a;	// { dg-error "missing template arguments" }
+  return a;
+}
-- 
2.30.2