Hack Language Reference

• The Hack Language
  • What is Hack?
  • Hack Background
  • Summary
• Type Annotations
  • Introductory Example
  • Why?
  • What types can be used?
  • How to type annotate
  • Examples
  • Type Casting
  • Annotating Arrays
  • Annotating Closures
  • Annotating Constructors
  • Annotating with this
  • Mixed Types
  • Passing By Reference
  • Typing Generators
  • Summary
• Hack Modes
  • Strict
  • Partial
  • Decl
  • Unsafe
• Generics
  • Introductory Example
  • Writing a Generic Class
  • Writing a Generic Trait and Interface
  • Writing a Generic Method
  • Generics and Type Inference
  • Override on Return Type
  • T<mixed> Compatibility
  • Constraints
  • Open and Closed Types
  • Style Guidelines
• Nullable
  • Why Nullable?
  • Why Not Always Use Nullable?
  • Case Study
  • Examples
  • Various Null Handling Scenarios
• Collections
  • Goals
  • Vector
  • Map
  • Set
  • Pair
  • Immutable Collections
  • Collection Interfaces
  • Square Bracket Syntax
  • Literal Syntax
  • Basic PHP operators and Collections
  • PHP Builtin Support
  • Examples
  • Limitations
  • Future work on collections
• Arrays
• Shapes
  • Simple Shape Example
  • Shapes Across Files
  • Shapes and Generics
  • Summary
• Type Aliasing
  • Type Aliasing
  • Opaque Type Aliasing
  • Opaque Type Aliases with Constraints
  • Examples
  • Summary
• Async
  • async and await
  • Type Annotating Async Functions
  • Example: Coalesced Fetching
  • Signature Examples
  • Awaitables vs Continuations
• Continuations
• Traits
  • Trait Requirements
• Trait Requirements
• Lambda Expressions
  • Design
  • Why ==>?
  • Examples
• Tuples
  • Use Cases
  • Tuples Are Implemented As Arrays
  • Type Annotating With Tuples
  • Returning a Tuple From a Method
  • Initializer Expressions
• Override Attribute
  • In Traits
• Method Dispatch
• Typing XHP
  • XHP Types
  • XHPChild
  • Returning XHP Elements
  • Other XHP Information
  • Future Plans
• Constructor Argument Promotion
• Other Hack Rules and Features
  • Variable Number of Arguments
  • Number Handling
  • Type Inference
  • Class Initialization
  • Callbacks and fun
  • Overriding on Return Type
  • invariant()
  • Function Signature Ordering
  • Calling Non-Private Methods During Initialization
  • Union Types
  • Heredocs
  • Nowdocs
  • Casting
  • Class Name Resolution
• Unsupported PHP Features in Hack
  • Top-level code
  • Collisions
  • Parent Static Methods
  • Calling Static Methods
• Predefined Interfaces and Classes
  • Traversable<Tv> — The Traversable<Tv> interface
  • Indexish<Tk,Tv> — The Indexish<Tk, Tv> interface
  • KeyedTraversable<Tk,Tv> — The KeyedTraversable<Tk, Tv> interface
  • Iterator<Tv> — The Iterator<Tv> interface
  • KeyedIterator<Tk, Tv> — The KeyedIterator<Tk, Tv> interface
  • IteratorAggregate<Tv> — The IteratorAggregate<Tv> interface
  • Iterable<Tv> — The Iterable<Tv> interface
  • KeyedIterable<Tk, Tv> — The KeyedIterable<Tk, Tv> interface
  • ArrayAccess<Tk, Tv> — The ArrayAccess<Tk, Tv> interface
  • Awaitable<T> — The Awaitable<T> class
  • Continuation<Tv> — The Continuation<Tv> class
  • XHPChild — The XHPChild interface