Hi,
in this diagnostic issue Jon noticed that for testcases like:
template<class T1, class... Tn>
void foo(T1, Tn...);
int main()
{
foo();
}
we provide diagnostic saying "candidate expects 2 arguments, 0
provided", whereas of course we want to say something like "candidate
expects at least 1 argument, 0 provided". The below simply tries to
refine the existing logic in type_unification_real. Note that while
handling this bug, I noticed that we don't appear to be up to date wrt
cases like:
template<class T1, class... Tn, class... Un>
void bar(T1, Tn..., Un...);
int main()
{
bar(1);
}
which we do reject and very recently clang started accepting. On the
other hand we accept:
int main()
{
bar(1, 2);
}
which clang rejects. My patch doesn't even try to cope with that (do be
honest, I didn't lookup the relevant DRs and resolutions), that seems to
me an unrelated issue, definitely not just a diagnostic one.
Thanks,
Paolo.
///////////////////////
/cp
2014-07-29 Paolo Carlini <paolo.carl...@oracle.com>
PR c++/57397
* pt.c (unify_arity): Add boolean parameter.
(unify_too_few_arguments): Likewise.
(type_unification_real): Diagnose correctly insufficient arguments
in the presence of trailing variadic parameters.
/testsuite
2014-07-29 Paolo Carlini <paolo.carl...@oracle.com>
PR c++/57397
* g++.dg/cpp0x/vt-57397.C: New.
Index: cp/pt.c
===================================================================
--- cp/pt.c (revision 213123)
+++ 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 lb_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 (lb_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 lb_p = false)
{
- return unify_arity (explain_p, have, wanted);
+ return unify_arity (explain_p, have, wanted, lb_p);
}
static int
@@ -16546,6 +16555,7 @@ type_unification_real (tree tparms,
const tree *args;
unsigned int nargs;
unsigned int ia;
+ bool remaining_pack_p = false;
gcc_assert (TREE_CODE (tparms) == TREE_VEC);
gcc_assert (xparms == NULL_TREE || TREE_CODE (xparms) == TREE_LIST);
@@ -16598,6 +16608,8 @@ type_unification_real (tree tparms,
tree argvec;
tree parmvec = make_tree_vec (1);
+ remaining_pack_p = true;
+
/* Allocate a TREE_VEC and copy in all of the arguments */
argvec = make_tree_vec (nargs - ia);
for (i = 0; ia < nargs; ++ia, ++i)
@@ -16622,13 +16634,20 @@ type_unification_real (tree tparms,
&& TREE_PURPOSE (parms) == NULL_TREE)
{
unsigned int count = nargs;
+ unsigned int excess_packs_count = 0;
tree p = parms;
while (p && p != void_list_node)
{
count++;
+ excess_packs_count
+ += TREE_CODE (TREE_VALUE (p)) == TYPE_PACK_EXPANSION;
p = TREE_CHAIN (p);
}
- return unify_too_few_arguments (explain_p, ia, count);
+
+ if (excess_packs_count)
+ count -= excess_packs_count - remaining_pack_p;
+ return unify_too_few_arguments (explain_p, ia, count,
+ excess_packs_count);
}
if (!subr)
Index: testsuite/g++.dg/cpp0x/vt-57397.C
===================================================================
--- testsuite/g++.dg/cpp0x/vt-57397.C (revision 0)
+++ testsuite/g++.dg/cpp0x/vt-57397.C (working copy)
@@ -0,0 +1,16 @@
+// 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 }
+ bar(1); // { dg-error "no matching" }
+ // { dg-message "candidate expects at least 2 arguments, 1 provided" "" {
target *-*-* } 14 }
+}
