root/types.js is very large and difficult to find things in without using grep. It's also annoying to keep properly "sorted," since we have some conflicts of interest there (keeping them in alphabetical order vs. keeping related types together).

Ideally we'd move related types into smaller files and import them from root/types.js (or add them to the flowconfig). There are probably even cases where a type doesn't need to be global, and can be moved closer to the module(s) where it's used.