Tested on Gnu/Linux, 64-bit, DMD-2.057

--------------------------8<----------------------------8<--------------------------------------

struct A(int r, int c){

public:
  alias r R;
  alias c C;
  alias float[R * C] Data;
  Data _data;
  alias _data this;

  this(Data ar){ _data = ar; }

  pure ref float opIndex(size_t rr, size_t cc){ return _data[cc + rr * C]; }
}

void main(){

  A!(2, 2) a = A!(2, 2)([8, 3, 2, 9]);
  a[0,0] -= a[0,0] * 2.0;
}

-------------------------->8---------------------------->8--------------------------------------

workaround: avoid compound assignment operators.