@@ -7170,26 +7170,68 @@ unify_bound_ttp_args (tree tparms, tree targs, tree parm, tree& arg,
parmvec = expand_template_argument_pack (parmvec);
argvec = expand_template_argument_pack (argvec);
- tree nparmvec = parmvec;
if (flag_new_ttp)
{
/* In keeping with P0522R0, adjust P's template arguments
to apply to A's template; then flatten it again. */
+ tree nparmvec = parmvec;
nparmvec = coerce_ttp_args_for_tta (arg, parmvec, tf_none);
nparmvec = expand_template_argument_pack (nparmvec);
+
+ if (unify (tparms, targs, nparmvec, argvec,
+ UNIFY_ALLOW_NONE, explain_p))
+ return 1;
+
+ /* If the P0522 adjustment eliminated a pack expansion, deduce
+ empty packs. */
+ if (flag_new_ttp
+ && TREE_VEC_LENGTH (nparmvec) < TREE_VEC_LENGTH (parmvec)
+ && unify_pack_expansion (tparms, targs, parmvec, argvec,
+ DEDUCE_EXACT, /*sub*/true, explain_p))
+ return 1;
}
+ else
+ {
+ /* Deduce arguments T, i from TT<T> or TT<i>.
+ We check each element of PARMVEC and ARGVEC individually
+ rather than the whole TREE_VEC since they can have
+ different number of elements, which is allowed under N2555. */
+
+ int len = TREE_VEC_LENGTH (parmvec);
+
+ /* Check if the parameters end in a pack, making them
+ variadic. */
+ int parm_variadic_p = 0;
+ if (len > 0
+ && PACK_EXPANSION_P (TREE_VEC_ELT (parmvec, len - 1)))
+ parm_variadic_p = 1;
- if (unify (tparms, targs, nparmvec, argvec,
- UNIFY_ALLOW_NONE, explain_p))
- return 1;
-
- /* If the P0522 adjustment eliminated a pack expansion, deduce
- empty packs. */
- if (flag_new_ttp
- && TREE_VEC_LENGTH (nparmvec) < TREE_VEC_LENGTH (parmvec)
- && unify_pack_expansion (tparms, targs, parmvec, argvec,
- DEDUCE_EXACT, /*sub*/true, explain_p))
- return 1;
+ for (int i = 0; i < len - parm_variadic_p; ++i)
+ /* If the template argument list of P contains a pack
+ expansion that is not the last template argument, the
+ entire template argument list is a non-deduced
+ context. */
+ if (PACK_EXPANSION_P (TREE_VEC_ELT (parmvec, i)))
+ return unify_success (explain_p);
+
+ if (TREE_VEC_LENGTH (argvec) < len - parm_variadic_p)
+ return unify_too_few_arguments (explain_p,
+ TREE_VEC_LENGTH (argvec), len);
+
+ for (int i = 0; i < len - parm_variadic_p; ++i)
+ if (unify (tparms, targs,
+ TREE_VEC_ELT (parmvec, i),
+ TREE_VEC_ELT (argvec, i),
+ UNIFY_ALLOW_NONE, explain_p))
+ return 1;
+
+ if (parm_variadic_p
+ && unify_pack_expansion (tparms, targs,
+ parmvec, argvec,
+ DEDUCE_EXACT,
+ /*subr=*/true, explain_p))
+ return 1;
+ }
return 0;
}
new file mode 100644
@@ -0,0 +1,16 @@
+// PR c++/81215
+// { dg-do compile { target c++11 } }
+
+template<typename U> struct X { };
+template<typename T, typename U = void> struct set { };
+
+template <typename V, template <typename...> class C>
+void bar (const X<C<V>>&)
+{
+}
+
+void
+foo (X<set<int>>& x)
+{
+ bar (x);
+}
For the C++17 changes to handling of template template parameter matching, I replaced a lot of the old code. But it seems that this piece is still necessary when we aren't in C++17 mode, to handle the case where we are comparing C<V> to set<int,void>, with different numbers of arguments. This is handled in C++17 mode by coerce_ttp_args_for_tta, but that has other effects that we want to limit to C++17 mode, at least for now. Tested x86_64-pc-linux-gnu, applying to trunk and 7. commit 6de84fdaef34cd48649ed501958aa3c93b289f7e Author: Jason Merrill <jason@redhat.com> Date: Mon Jun 26 14:35:52 2017 -0400 PR c++/81215 - deduction failure with variadic TTP. * pt.c (unify_bound_ttp_args): Restore old logic for C++14 and down.