TypeScript 5.7: Pattern Matching and Beyond

TypeScript 5.7 shipped with the feature developers have been requesting since 2018: native pattern matching. Combined with exhaustiveness checking and improved type narrowing, this release fundamentally changes how we write conditional logic.

Pattern Matching Syntax

The new match expression replaces nested ternaries and switch statements with a declarative, type-safe construct:

type Shape =
  | { kind: "circle"; radius: number }
  | { kind: "rectangle"; width: number; height: number };

function area(shape: Shape): number {
  return match(shape) {
    { kind: "circle", radius: r }: Math.PI * r ** 2,
    { kind: "rectangle", width: w, height: h }: w * h,
  };
}

The compiler enforces exhaustiveness — missing a case is a compile error, not a runtime crash.

Why This Matters

Pattern matching eliminates entire categories of bugs. The exhaustive checking means your code cannot silently fail when a new variant is added. Refactoring becomes safer because the compiler tells you exactly which match expressions need updating.

Migration Path

The feature is backward compatible. Existing switch statements continue to work. Start with discriminated unions, then expand to more complex patterns as the team gets comfortable.

Performance Impact

Pattern matching compiles to optimized if-else chains — there is no runtime overhead compared to hand-written conditionals. The real win is developer productivity and code clarity.