expression must have pointer-to-object type

Following compiles with gcc but fails with Intel compiler, any idea?

typedef float __attribute__ ( ( vector_size( 4*sizeof(float) ) ) ) Vec4F;
float x(Vec4F const & v){return  v[0];}

>icpc -v
icpc version 15.0.0 (gcc version 4.8.1 compatibility)>icpc -c foo.cc
Y/src/foo.cc(2): error: expression must have pointer-to-object type
  float x(Vec4F const & v){return  v[0];}
                                   ^

compilation aborted for foo.cc (code 2)