From 1e2b90c4ac0b08279fdfe65c6fab3c49573f236c Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Thu, 29 Mar 2018 15:38:41 -0400
Subject: [PATCH] PR c++/85093 - too many template args with pack expansion.

	* pt.c (coerce_template_parms): Keep pack expansion args that will
	need to be empty.

From-SVN: r258964
---
 gcc/cp/ChangeLog                             |  6 ++++++
 gcc/cp/pt.c                                  | 16 ++++++++++++++++
 gcc/testsuite/g++.dg/cpp0x/variadic-empty1.C | 13 +++++++++++++
 3 files changed, 35 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/variadic-empty1.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index cc950e8d74e..1536c359fe8 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2018-03-29  Jason Merrill  <jason@redhat.com>
+
+	PR c++/85093 - too many template args with pack expansion.
+	* pt.c (coerce_template_parms): Keep pack expansion args that will
+	need to be empty.
+
 2018-03-29  Jason Merrill  <jason@redhat.com>
 
 	* pt.c (build_non_dependent_expr): Propagate expr location.
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 40ddf9ec989..284eaf3cab6 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -8497,6 +8497,22 @@ coerce_template_parms (tree parms,
       goto bad_nargs;
     }
 
+  if (arg_idx < nargs)
+    {
+      /* We had some pack expansion arguments that will only work if the packs
+	 are empty, but wait until instantiation time to complain.
+	 See variadic-ttp3.C.  */
+      int len = nparms + (nargs - arg_idx);
+      tree args = make_tree_vec (len);
+      int i = 0;
+      for (; i < nparms; ++i)
+	TREE_VEC_ELT (args, i) = TREE_VEC_ELT (new_inner_args, i);
+      for (; i < len; ++i, ++arg_idx)
+	TREE_VEC_ELT (args, i) = TREE_VEC_ELT (inner_args,
+					       arg_idx - pack_adjust);
+      new_inner_args = args;
+    }
+
   if (lost)
     {
       gcc_assert (!(complain & tf_error) || seen_error ());
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic-empty1.C b/gcc/testsuite/g++.dg/cpp0x/variadic-empty1.C
new file mode 100644
index 00000000000..42daeaa3dcb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic-empty1.C
@@ -0,0 +1,13 @@
+// PR c++/85093
+// { dg-do compile { target c++11 } }
+
+template<class V> class A {};
+
+template<class V, class... G> class B {
+  typedef A<V,G...> AB;		// { dg-error "arguments" }
+  AB ab;
+};
+
+int main() {
+  B<int,double> b;  
+}
-- 
2.30.2