Introducing Hack

on YouTube ↗55m

" summary

Hack adds a static type checker to HHVM that runs as a background server, scales to thousands of files, and returns mass error results in under 200 ms (demo shows 7,000 lines of errors and a 160 ms turnaround). It supports incremental adoption via file-level strict / partial / decl modes, nullable types and generics, and defers resolution with unresolved types so common PHP patterns remain valid. Tooling includes HH client pings, editor plugins, a color mode showing checked regions, shared‑memory caching, parallel workers and fine‑grained dependency tracking.

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" chapters (5)

1. 0:00Start
2. 8:51Hack Type System What must be annotated Class members Function parameters Return types What is inferred? All the rest
3. 25:14Hack Type Inference (2) How does a type system normally work? Type variables are introduced A unification algorithm solves the type-variables usually noted
4. 29:22Error Messages We can't expect the user to understand all the type inference The solution keep the reason why we deduced a type and expose it to the user
5. 36:20Working at Scale: The Solution How do we make this work We parallelize We cache We do things incrementally

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