pattern-matching typescript algebraic-data-types

How do you emulate ADTs and pattern matching in TypeScript?

Unfortunately, as of 0.9.5, TypeScript doesn't (yet) have algebraic data types (union types) and pattern matching (to destructure them). What's more, it doesn't even support instanceof on interfaces. Which pattern do you use to emulate these language features with maximal type safety and minimal boilerplate code?

Solution

TypeScript 1.4 adds union types and type guards.

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