unifyCompound is not commutative when applied to pseudo classes of pseudo elements

[mattrberry]

The following produces .y.x::scrollbar:vertical as expected

print(unifyCompound(
  CompoundSelector.parse('.x'),
  CompoundSelector.parse('.y::scrollbar:vertical'),
));

However, swapping the operands produces .x.y:vertical::scrollbar

print(unifyCompound(
  CompoundSelector.parse('.y::scrollbar:vertical'),
  CompoundSelector.parse('.x'),
));

[Goodwine]

To clarify, because I was confused, the issue is not that .x and .y switched places. The issue is that :vertical and ::scrollbar switched places