Same bug as this?
I don't think it's right for EQ to compare rawValues instead of enumeration tags, we had a thread on this recently. As a workaround I'd suggest to always override "==" when you adding RawRepresentable conformance, in this case:
public static func == (lhs: Self, rhs: Self) -> Bool {
switch (lhs, rhs) {
case (.a, .a), (.b, .b): true
case (.a, .b), (.b, .a): false
}
}