int3/cdlre — comment on commit 68aa5fd5f9ef31678833f3e4fda937ee9e8aa1b2
File:  line 0
By int3:

We would have to replace all Set instances in CharacterSet with our wrapper type, though, because we would need to be able to union() any two sets -- inverted and non-inverted. If the plain Set object is not going to be used anywhere else in the code, then it might not be useful to maintain it as a separate underlying type.