From 809c28c8dd3c8827ab64147994c2b57a91b09f7b Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Mon, 19 Mar 2018 16:32:57 -0400
Subject: [PATCH] PR c++/71834 - template-id with too few arguments.

	* pt.c (coerce_template_parms): Check fixed_parameter_pack_p.

From-SVN: r258659
---
 gcc/cp/ChangeLog                              |  5 ++
 gcc/cp/pt.c                                   | 50 +++++++++++++------
 gcc/testsuite/g++.dg/cpp0x/variadic-nested3.C | 10 ++++
 3 files changed, 49 insertions(+), 16 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/variadic-nested3.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 12aaf135294..194b4689082 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2018-03-16  Jason Merrill  <jason@redhat.com>
+
+	PR c++/71834 - template-id with too few arguments.
+	* pt.c (coerce_template_parms): Check fixed_parameter_pack_p.
+
 2018-03-19  Nathan Sidwell  <nathan@acm.org>
 
 	PR c++/84835
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index fba65b4abdf..086cdc20781 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -8235,6 +8235,11 @@ coerce_template_parms (tree parms,
   int variadic_args_p = 0;
   int post_variadic_parms = 0;
 
+  /* Adjustment to nparms for fixed parameter packs.  */
+  int fixed_pack_adjust = 0;
+  int fixed_packs = 0;
+  int missing = 0;
+
   /* Likewise for parameters with default arguments.  */
   int default_p = 0;
 
@@ -8279,6 +8284,7 @@ coerce_template_parms (tree parms,
 	      || (TREE_VEC_ELT (parms, nargs) != error_mark_node
                   && !TREE_PURPOSE (TREE_VEC_ELT (parms, nargs))))))
     {
+    bad_nargs:
       if (complain & tf_error)
 	{
           if (variadic_p || default_p)
@@ -8390,11 +8396,17 @@ coerce_template_parms (tree parms,
 	      lost++;
 	      /* We are done with all of the arguments.  */
 	      arg_idx = nargs;
+	      break;
 	    }
 	  else
 	    {
 	      pack_adjust = TREE_VEC_LENGTH (ARGUMENT_PACK_ARGS (arg)) - 1;
 	      arg_idx += pack_adjust;
+	      if (fixed_parameter_pack_p (TREE_VALUE (parm)))
+		{
+		  ++fixed_packs;
+		  fixed_pack_adjust += pack_adjust;
+		}
 	    }
           
           continue;
@@ -8452,12 +8464,18 @@ coerce_template_parms (tree parms,
 	    error ("template argument %d is invalid", arg_idx + 1);
 	}
       else if (!arg)
-        /* This only occurs if there was an error in the template
-           parameter list itself (which we would already have
-           reported) that we are trying to recover from, e.g., a class
-           template with a parameter list such as
-           template<typename..., typename>.  */
-	++lost;
+	{
+	  /* This can occur if there was an error in the template
+	     parameter list itself (which we would already have
+	     reported) that we are trying to recover from, e.g., a class
+	     template with a parameter list such as
+	     template<typename..., typename> (cpp0x/variadic150.C).  */
+	  ++lost;
+
+	  /* This can also happen with a fixed parameter pack (71834).  */
+	  if (arg_idx >= nargs)
+	    ++missing;
+	}
       else
 	arg = convert_template_argument (TREE_VALUE (parm),
 					 arg, new_args, complain, 
@@ -8470,20 +8488,20 @@ coerce_template_parms (tree parms,
   cp_unevaluated_operand = saved_unevaluated_operand;
   c_inhibit_evaluation_warnings = saved_inhibit_evaluation_warnings;
 
-  if (variadic_p && arg_idx < nargs)
+  if (missing || arg_idx < nargs - variadic_args_p)
     {
-      if (complain & tf_error)
-	{
-	  error ("wrong number of template arguments "
-		 "(%d, should be %d)", nargs, arg_idx);
-	  if (in_decl)
-	    error ("provided for %q+D", in_decl);
-	}
-      return error_mark_node;
+      /* If we had fixed parameter packs, we didn't know how many arguments we
+	 actually needed earlier; now we do.  */
+      nparms += fixed_pack_adjust;
+      variadic_p -= fixed_packs;
+      goto bad_nargs;
     }
 
   if (lost)
-    return error_mark_node;
+    {
+      gcc_assert (!(complain & tf_error) || seen_error ());
+      return error_mark_node;
+    }
 
   if (CHECKING_P && !NON_DEFAULT_TEMPLATE_ARGS_COUNT (new_inner_args))
     SET_NON_DEFAULT_TEMPLATE_ARGS_COUNT (new_inner_args,
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic-nested3.C b/gcc/testsuite/g++.dg/cpp0x/variadic-nested3.C
new file mode 100644
index 00000000000..381ff731c09
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic-nested3.C
@@ -0,0 +1,10 @@
+// PR c++/71834
+// { dg-do compile { target c++11 } }
+
+template < typename ... Ts > struct A 
+{
+  template < Ts ..., typename U > struct B {};
+};
+
+// should be, e.g.: A < int >::B < 0, int > e; 
+A < int >::B < 0 > e;	   // { dg-error "wrong number of template arguments" }
-- 
2.30.2