template <typename, typename = int> struct basic_ostream {}; namespace N { template <typename Char, typename CharTraits, typename T> void operator<<(basic_ostream<Char, CharTraits>, T); } basic_ostream<char> os; template<typename T> void foo (T value) { using N::operator<<; os << value; } void bar() { foo (1); } gives $ ./cc1plus -quiet ceph.C ceph.C: In instantiation of ‘void foo(T) [with T = int]’: ceph.C:14:20: required from here ceph.C:12:6: error: no match for ‘operator<<’ (operand types are ‘basic_ostream<char>’ and ‘int’) 12 | os << value; | ~~~^~~~~~~~ Started with r11-4690.
This seems to work... --- a/gcc/cp/name-lookup.c +++ b/gcc/cp/name-lookup.c @@ -9279,4 +9279,14 @@ push_operator_bindings () } } +/* Wrapper around push_local_binding to push the bindings for + a non-member USING_DECL that were found during template parsing. */ + +void +push_using_decl_bindings (tree decl) +{ + push_local_binding (DECL_NAME (decl), USING_DECL_DECLS (decl), + /*using*/true); +} + #include "gt-cp-name-lookup.h" diff --git a/gcc/cp/name-lookup.h b/gcc/cp/name-lookup.h index 7172079b274..bac3fa71fc9 100644 --- a/gcc/cp/name-lookup.h +++ b/gcc/cp/name-lookup.h @@ -478,6 +478,7 @@ extern void push_to_top_level (void); extern void pop_from_top_level (void); extern void maybe_save_operator_binding (tree); extern void push_operator_bindings (void); +extern void push_using_decl_bindings (tree); extern void discard_operator_bindings (tree); /* Lower level interface for modules. */ diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index 100c35f053c..c27ef6d9fe0 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -18133,6 +18133,9 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl, tree scope = USING_DECL_SCOPE (decl); gcc_checking_assert (scope == tsubst (scope, args, complain, in_decl)); + /* We still need to push the bindings so that we can look up + this name later. */ + push_using_decl_bindings (decl); } else if (is_capture_proxy (decl) && !DECL_TEMPLATE_INSTANTIATION (current_function_decl))
The master branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>: https://gcc.gnu.org/g:796ead19f85372e59217c9888db688a2fe11b54f commit r11-6652-g796ead19f85372e59217c9888db688a2fe11b54f Author: Marek Polacek <polacek@redhat.com> Date: Wed Jan 13 11:09:14 2021 -0500 c++: Failure to lookup using-decl name [PR98231] In r11-4690 we removed the call to finish_nonmember_using_decl in tsubst_expr/DECL_EXPR in the USING_DECL block. This was done not to perform name lookup twice for a non-dependent using-decl, which sounds sensible. However, finish_nonmember_using_decl also pushes the decl's bindings which we still have to do so that we can find the USING_DECL's name later. In this case, we've got a USING_DECL N::operator<< that we are tsubstituting. We already looked it up while parsing the template "foo", and lookup_using_decl stashed the OVERLOAD it found into USING_DECL_DECLS. Now we just have to update the IDENTIFIER_BINDING of the identifier for operator<< with the overload the name is bound to. I didn't want to export push_local_binding so I've introduced a new wrapper. gcc/cp/ChangeLog: PR c++/98231 * name-lookup.c (push_using_decl_bindings): New. * name-lookup.h (push_using_decl_bindings): Declare. * pt.c (tsubst_expr): Call push_using_decl_bindings. gcc/testsuite/ChangeLog: PR c++/98231 * g++.dg/lookup/using63.C: New test.
Fixed.