See KT-21493
It's hard to maintain staticRef in cached AST. In fact, we don't need
it in this optimization. We'll get excessive names in used set,
which is ok: non-function names don't matter, they'll be simply ignored.
One possible concern: there's more chance to get name same to
some function's name and it won't be removed. First, it's not fatal,
it won't break the code (but put some excessive code that will likely
be removed by DCE). Second, there's same chance of two functions
having same names, and we manage to avoid this (otherwise we'll get
many problems).
Anton Bannykh