There are three (and only three) places where types can be explicitly annotated in Hack.

# Function and Method Returns

# Function and Method Parameters

# Class Properties

There are three (and only three) places where types can be explicitly annotated in Hack.

# Function and Method Returns

# Function and Method Parameters

# Class Properties

## Abstract class constants

In addition to typing properties with their datatype, you can also declare constants abstract in an abstract class

Add reminder about abstract class constants
Add reminder about abstract class constants
