[Bug c++/70610] New: [6 regression] error: invalid initialization of non-const reference of type

[david.abdurachmanov at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70610

            Bug ID: 70610
           Summary: [6 regression] error: invalid initialization of
                    non-const reference of type
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: david.abdurachmanov at gmail dot com
  Target Milestone: ---

This is a follow up of comment:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=21802#c8

Caused by:

d175f0193ed47b61eafd213ca2d3dde73f8f5996 is the first bad commit
commit d175f0193ed47b61eafd213ca2d3dde73f8f5996
Author: ppalka <ppalka@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Tue Dec 15 03:33:53 2015 +0000

    Fix PR c++/21802 (two-stage name lookup fails for operators)

Works fine with GCC 5.3.0, Clang 3.7.0 and ICC (16.0.2 20160204).

Minimal reproducer by Patrick Palka:

struct A { };

A operator+ (A &) { return A (); }
A operator+ (const A &) { return A (); }


template <typename T>
void
foo ()
{
  +A ();
}

void
bar ()
{
  foo<int> ();
}

$ g++ -c -ansi test.cc
test.cc: In instantiation of 'void foo() [with T = int]':
test.cc:17:13:   required from here
test.cc:11:3: error: invalid initialization of non-const reference of type 'A&'
from an rvalue of type 'A'
   +A ();
   ^~~~~
test.cc:3:3: note:   initializing argument 1 of 'A operator+(A&)'
 A operator+ (A &) { return A (); }
   ^~~~~~~~

Note, that removing -ansi solves the issue.