A Tour of New Hack Language and Library Features

Explore new features added to Hack, including generics, short lambda syntax, and the Collections API in this comprehensive talk from Meta's Hack Dev Day. Dive into type annotations at runtime, PHP closure expressions, Hack lambda expressions, and their benefits. Examine Hack Collections, static typing, immutable collections, and async/await functionality. Learn about constructor promotion, trailing commas, error detection in traits, and trait interfaces. Gain insights into future directions for Hack development from software engineers Drew Paroski and Eugene Letuchy.

Intro
Type Annotations at Run Time
PHP Closure Expressions
Hack Lambda Expressions
Benefits of Lambda Expressions
More Examples
Hack Collections
map/filter example
Design
array_merge() example
Downsides of one-size-fits-all
Static Typing
PHP arrays have value-type semantics
Immutable Collections
Code example: Sync = Async
Awaitable
Parallel async/await
Mid-execution
Entering async
Goodies!: Constructor Promotion
Goodies!: Trailing Commas
Detecting Errors in Traits
Trait requirements: solution
Goodies!: Trait Interfaces
Future Directions