Understanding TypeScript 6.0 Features

TypeScript 6.0 introduces some massive improvements to type inference, runtime safety, and developer ergonomics. Let's dive into the most highly anticipated features.

Pattern Matching

One of the most requested features for years, native pattern matching, finally makes its way into TS. This drastically reduces boilerplate and eliminates the need for complex switch statements and clunky type guards.

type Shape = 
  | { type: 'circle', radius: number }
  | { type: 'square', width: number }
  | { type: 'rectangle', width: number, height: number };

function getArea(shape: Shape) {
  // New pattern matching syntax
  return match(shape)
    .with({ type: 'circle' }, c => Math.PI * c.radius ** 2)
    .with({ type: 'square' }, s => s.width ** 2)
    .with({ type: 'rectangle' }, r => r.width * r.height)
    .exhaustive(); // Compiler error if we forget a case!
}

Improved Type Inference for Generics

TypeScript 6.0 brings a smarter inference engine. In the past, passing deeply nested generic objects would often result in the dreaded any or unknown types creeping into your codebase.

With the new engine, the compiler recursively evaluates generic bounds much more efficiently, resulting in a 30% reduction in compile times for large monorepos. The days of fighting the TS compiler to prove a type is safe are slowly coming to an end.