Speed improvements

TypeScript 3.5 introduces several optimizations around type-checking and incremental builds.

Type-checking speed-ups

TypeScript 3.5 contains certain optimizations over TypeScript 3.4 for type-checking more efficiently.These improvements are significantly more pronounced in editor scenarios where type-checking drives operations like code completion lists.

—incremental improvements

TypeScript 3.5 improves on 3.4’s —incremental build mode, by saving information about how the state of the world was calculated - compiler settings, why files were looked up, where files were found, etc.In scenarios involving hundreds of projects using TypeScript’s project references in —build mode, we’ve found that the amount of time rebuilding can be reduced by as much as 68% compared to TypeScript 3.4!

For more details, you can see the pull requests to

• cache module resolution
• cache settings calculated from tsconfig.json