[Bug c++/51738] New: C++11 initializer list does not work correctly with operator[]

[akrzemi1 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51738

             Bug #: 51738
           Summary: C++11 initializer list does not work correctly with
                    operator[]
    Classification: Unclassified
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: akrze...@gmail.com


I compile the following code:

~~~~
struct Index{
  Index(unsigned, unsigned){}
};

struct Matrix{
  void operator[](Index){}
};

int main() {
  Matrix m;
  m[{0,1}];
  //m.operator[]({0,1}); -- this is valid
  //m[Index{0,1}]; -- this is valid
}
~~~~

I use the following command:

g++ main.cpp -Wall -Wextra -fno-strict-aliasing -fwrapv -std=c++0x -o brace.exe 

I get the following reply:

main.cpp: In function ‘int main()’:
main.cpp:11:5: error: expected primary-expression before ‘{’ token
main.cpp:11:5: error: expected ‘]’ before ‘{’ token
main.cpp:11:5: error: expected ‘;’ before ‘{’ token
main.cpp:11:10: error: expected primary-expression before ‘]’ token
main.cpp:11:10: error: expected ‘;’ before ‘]’ token

This is a bug because my program is valid C++11 code, and if I write:
m.operator[]({0,1});
instead of
m[{0,1}];

my program compiles.

This has been already reported in bug report 39901, but 39901 has been
incorrectly put into "RESOLVED INVALID"state. Code:

m[{0,1}];

should be equivalent to:

m[Index{0,1}];

Regards,
&rzej