We have introduced many different flavors of types. Let's now talk about some type-based features that enrich our use of types and typed values.

• as and into for explicit conversion or reinterpretation of values from one type to another. Where subtyping is in play, values will implicitly coerce to their supertype.
• typedef, which enables the creation of a named alias for some type signature.
• extend, which allows an existing type to be extended to support additional methods.