[Bug c++/98231] New: [11 Regression] bogus error: no match for ‘operator<<’

[Bug c++/98231] New: [11 Regression] bogus error: no match for ‘operator<<’

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98231

            Bug ID: 98231
           Summary: [11 Regression] bogus error: no match for ‘operator<<’
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mpolacek at gcc dot gnu.org
  Target Milestone: ---

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.

[Bug c++/98231] [11 Regression] bogus error: no match for ‘operator<<’

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98231

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Target Milestone|---                         |11.0
           Priority|P3                          |P1
   Last reconfirmed|                            |2020-12-11
     Ever confirmed|0                           |1
           Keywords|                            |rejects-valid
                 CC|                            |nathan at gcc dot gnu.org

[Bug c++/98231] [11 Regression] bogus error: no match for ‘operator<<’

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98231

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
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))

[Bug c++/98231] [11 Regression] bogus error: no match for ‘operator<<’

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98231

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org

[Bug c++/98231] [11 Regression] bogus error: no match for ‘operator<<’

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98231

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
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.

[Bug c++/98231] [11 Regression] bogus error: no match for ‘operator<<’

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98231

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed.