TypeScript · correctness

require-assert-never

eslint:require-assert-never

Require an empty switch default to call `assertNever` so discriminated unions remain exhaustive at compile time.

Why

An empty default silently accepts new union members instead of making the compiler identify the missing case.

Call `assertNever` with the discriminant in the exhaustive switch default.

Executed by this rule’s unit tests.

Before

src/render.ts · focus

declare const kind: 'a' | 'b';
switch (kind) { case 'a': break; case 'b': break; default: }

After

src/render.ts · focus

declare const kind: 'a' | 'b';
switch (kind) { case 'a': break; case 'b': break; default: assertNever(kind); }

missingAssertNever