[Bug c++/59960] New: accepts ill-formed 'auto a1 = t1, a2 = t2;' where t1 and t2 have different template types

["gcc at abeckmann dot de" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59960

            Bug ID: 59960
           Summary: accepts ill-formed 'auto a1 = t1, a2 = t2;' where t1
                    and t2 have different template types
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gcc at abeckmann dot de

The following code is accepted by g++ in c++11 mode (tested 4.7, 4.8, 4.9):

===== 8< =====
#include <iostream>
#include <typeinfo>

template <typename T1, typename T2>
void f(T1 & t1, T2 & t2)
{
        auto a1 = t1, a2 = t2;
        std::cout << typeid(a1).name() << std::endl;
        std::cout << typeid(a2).name() << std::endl;
}

int main ()
{
        int i(23);
        double d(42.);
        f(i, d);
}
===== >8 =====
the output id generates is
----- 8< -----
i
d
----- >8 -----

But the standard says in [dcl.spec.auto] clause 7: If the list [...] contains
more than one declarator, the type of each declared variable is determined as
described above. If the type deduced [...] is not the same in each deduction,
the program is ill-formed.

clang fails compilation with

auto2.cpp:7:2: error: 'auto' deduced as 'int' in declaration of 'a1' and
deduced as 'double' in declaration of 'a2'
        auto a1 = t1, a2 = t2;
        ^         ~~       ~~