Flow stuff

Flowtype.md

Flow

• website: https://flowtype.org/
• original announcment: https://code.facebook.com/posts/1505962329687926/flow-a-new-static-type-checker-for-javascript/
• paper: http://www.cs.umd.edu/~avik/papers/iogti.pdf
• inspection utility: https://github.com/flowtype/flow-inspect

Extrinsic type system (Curry style)

Contrast with intrinsic type systems (ML, Haskell, Java, Scala).

Try it!

https://flowtype.org/try/

• function type annotation
• type aliases
• Unions, Intersections
• dynamic type tests
• Exact types
• any vs mixed
• map types
• typeof types
• $Keys<O>
• $ObjMap<O, F>

Secret sauce

Inference

Instead of typing unannotated terms with any, aka supertype and subtype of all types, try to infer types.

"Lazy"

Instead of eagerly assigning types to terms, record all inflows and check for consistency among flows as information grows.

Video

https://www.youtube.com/watch?v=VEaDsKyDxkY