The doc comment for PatternMatcher is incorrect. it states it is threadsafe when it is not. SPecifically, internally for each 'chunk' of the pattern it breaks out, it keeps a 'similarity cache' of hte last thing it was matched against. this is so that checking it repeatedly against the same name (common with things like overloads, or candidate strings with similar portions) can jsut return the previously computed result. this cache is mutable and is not safe for concurrent mutation.

I have audited all users and have seen that no one does actually use this across threads. However, the docs shouldn't convey the wrong info here.