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I'm declaring TypeScript 7 for Ember: ready At work, on the 3 million line monolithic package, I'm seeing ~ 4m40s -> 12s a ✨ 23x ✨ speed boost

23x!? What are you passing to --checkers?

yea, it's wild, I can only assume the better-than-10x improvement is due to all the abstractions / monkey patching needed for custom file formats in TS < 7. > checkers I'm unfamiliar with this? what is it?

TypeScript 7 does everything with maximum parallelism, with the exception of more modest parallelism in type-checking.

We can't check files independently, because they reach into each other and we don't have thread-safe checker state. We can spawn multiple threads with their own type-checker state, but that has a lot of overhead and duplication of work.

So we picked a reasonable default for type-checker parallelism and said "4 threads per program". But you can increase/decrease parallelism with the --checkers flag. devblogs.microsoft.com/typescript/a...