With coords having type int[], passing an argument of type double[] fails to compile from the type mismatch, but it also fails to compile when passed an int[], since it can't implicitly convert the int[] to a double[] when assigning to the _coords member.
For example, using either the second or third lines below was causing an error.

auto line = new CanvasLine([0.0, 0.0, 9.0, 9.0]);
line.setCoords([0.0, 0.0, 9.0, 9.0]);
line.setCoords([0, 0, 9, 9]);