Usage
    propertyName:*

Specifies that a property is untyped. Use of the asterisk symbol for a type annotation is equivalent to using no type annotation. Expressions that read from untyped properties are considered untyped expressions. Use of untyped expressions or properties is recommended in the following circumstances:

• When you want to defer type checking to runtime. You can use an untyped property or expression to circumvent compile-time type checking in strict mode. Note, however, that runtime type checking of assignment statements occurs whether you use strict mode or not.
• When you want to store the value undefined in a property. Unlike previous versions of ActionScript, the value undefined is not a member of the Object data type. You must used an untyped property to store the value undefined.

Usage
    functionName():void {}

Specifies that a function cannot return any value. The void type is a special type that contains exactly one value: undefined. It is special in that its use is limited to the return type of a function. You cannot use void as a type annotation for a property.

A special data type that represents the lack of a value. The Null data type includes only one value: null. The Null data type is special in that it is not associated with a class. This means that you cannot use the Null data type as a type annotation for a property.