Re: [C++ Patch] PR 57397

[Paolo Carlini]

... I'm finishing testing the below.

Thanks!
Paolo.

//////////////////////

Index: cp/pt.c
===================================================================
--- cp/pt.c     (revision 213287)
+++ cp/pt.c     (working copy)
@@ -5517,13 +5517,21 @@ unify_method_type_error (bool explain_p, tree arg)
 }
 
 static int
-unify_arity (bool explain_p, int have, int wanted)
+unify_arity (bool explain_p, int have, int wanted, bool least_p = false)
 {
   if (explain_p)
-    inform_n (input_location, wanted,
-             "  candidate expects %d argument, %d provided",
-             "  candidate expects %d arguments, %d provided",
-             wanted, have);
+    {
+      if (least_p)
+       inform_n (input_location, wanted,
+                 "  candidate expects at least %d argument, %d provided",
+                 "  candidate expects at least %d arguments, %d provided",
+                 wanted, have);
+      else
+       inform_n (input_location, wanted,
+                 "  candidate expects %d argument, %d provided",
+                 "  candidate expects %d arguments, %d provided",
+                 wanted, have);
+    }
   return 1;
 }
 
@@ -5534,9 +5542,10 @@ unify_too_many_arguments (bool explain_p, int have
 }
 
 static int
-unify_too_few_arguments (bool explain_p, int have, int wanted)
+unify_too_few_arguments (bool explain_p, int have, int wanted,
+                        bool least_p = false)
 {
-  return unify_arity (explain_p, have, wanted);
+  return unify_arity (explain_p, have, wanted, least_p);
 }
 
 static int
@@ -16617,18 +16626,33 @@ type_unification_real (tree tparms,
      are present, and the parm list isn't variadic.  */
   if (ia < nargs && parms == void_list_node)
     return unify_too_many_arguments (explain_p, nargs, ia);
-  /* Fail if parms are left and they don't have default values.  */
+  /* Fail if parms are left and they don't have default values and
+     they aren't all deduced as empty packs, eg (c++/57397):
+
+     template<class T1, class... Tn, class... Tm>
+     void foo(T1, Tn..., Tm...);
+
+     int main()
+     {
+       foo(1);
+     }  */
   if (parms && parms != void_list_node
       && TREE_PURPOSE (parms) == NULL_TREE)
     {
       unsigned int count = nargs;
       tree p = parms;
-      while (p && p != void_list_node)
+      bool type_pack_p;
+      do
        {
-         count++;
+         type_pack_p = TREE_CODE (TREE_VALUE (p)) == TYPE_PACK_EXPANSION;
+         if (!type_pack_p)
+           count++;
          p = TREE_CHAIN (p);
        }
-      return unify_too_few_arguments (explain_p, ia, count);
+      while (p && p != void_list_node);
+      if (count != nargs)
+       return unify_too_few_arguments (explain_p, ia, count,
+                                       type_pack_p);
     }
 
   if (!subr)
Index: testsuite/g++.dg/cpp0x/vt-57397-1.C
===================================================================
--- testsuite/g++.dg/cpp0x/vt-57397-1.C (revision 0)
+++ testsuite/g++.dg/cpp0x/vt-57397-1.C (working copy)
@@ -0,0 +1,22 @@
+// PR c++/57397
+// { dg-do compile { target c++11 } }
+
+template<class T1, class... Tn>
+void foo(T1, Tn...);
+
+template<class T1, class T2, class... Tn>
+void bar(T1, T2, Tn...);
+
+int main()
+{
+  foo();   // { dg-error "no matching" }
+  // { dg-message "candidate expects at least 1 argument, 0 provided" "" { 
target *-*-* } 12 }
+  foo(1);
+  foo(1, 2);
+  bar();   // { dg-error "no matching" }
+  // { dg-message "candidate expects at least 2 arguments, 0 provided" "" { 
target *-*-* } 16 }
+  bar(1);  // { dg-error "no matching" }
+  // { dg-message "candidate expects at least 2 arguments, 1 provided" "" { 
target *-*-* } 18 }
+  bar(1, 2);
+  bar(1, 2, 3);
+}
Index: testsuite/g++.dg/cpp0x/vt-57397-2.C
===================================================================
--- testsuite/g++.dg/cpp0x/vt-57397-2.C (revision 0)
+++ testsuite/g++.dg/cpp0x/vt-57397-2.C (working copy)
@@ -0,0 +1,24 @@
+// PR c++/57397
+// { dg-do compile { target c++11 } }
+
+template<class T1, class... Tn, class... Tm>
+void foo(T1, Tn..., Tm...);
+
+template<class T1, class T2, class... Tn, class... Tm>
+void bar(T1, T2, Tn..., Tm...);
+
+int main()
+{
+  foo();   // { dg-error "no matching" }
+  // { dg-message "candidate expects at least 1 argument, 0 provided" "" { 
target *-*-* } 12 }
+  foo(1);
+  foo(1, 2);
+  foo(1, 2, 3);
+  bar();   // { dg-error "no matching" }
+  // { dg-message "candidate expects at least 2 arguments, 0 provided" "" { 
target *-*-* } 17 }
+  bar(1);  // { dg-error "no matching" }
+  // { dg-message "candidate expects at least 2 arguments, 1 provided" "" { 
target *-*-* } 19 }
+  bar(1, 2);
+  bar(1, 2, 3);
+  bar(1, 2, 3, 4);
+}