TypeScript 2.0 borrows from Rust and Swift

With the TypeScript 2.0 release candidate, Microsoft's typed superset of JavaScript mimics a tagged unions type capability featured in languages like Rust and Swift. Through this feature, developers can cut down on writing boilerplate code.
Daniel Rosenwasser, Microsoft program manager for TypeScript, used an example in which two types, "Circle" and "Square," have a union type, "Shape." In TypeScript 1.8, writing a function to get the area of Shape required a type assertions for each type, wher