c418f00536
Some time ago, a refactor (1153dc960) broke completion for assigning settings
values (`settings set`). This was most annoying for enum settings, where you'd
have to get the valid enum names separately.
This restores the logic in the post-refactor completion function, as well as
adding a test to catch future regressions.
Differential Revision: https://reviews.llvm.org/D134515