Typing Erlang with eqWAlizer
summary
WhatsApp adopts eqWAlizer as a static type checker and gets 100% of the codebase checked within a year, progressing from 63% in July to 94% in December and finishing the last 6% in three months. eqWAlizer uses local type inference with a Dynamic type to mix typed and untyped code, runs in CI and blocks landing on type failures, complements incremental Dialyzer (3–7x faster) and reports many real bugs, so the rollout proves practical at scale.
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chapters (17)
- 0:00Introduction
- 1:04WhatsApp Code Base History
- 2:30Why add specs
- 4:01Problems with specs
- 6:05equalizer
- 6:27dialysis
- 7:15Gradle typing
- 8:03PHP
- 9:33Dynamic Type
- 10:42Type Checkers
- 11:56Development Goals
- 18:44Graduality
- 20:17Types
- 21:15Gradle
- 21:27Timeline
- 22:27Conclusions
- 22:53Questions
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