gvergnaud/ts-pattern v3.3.1 on GitHub

Features

Add a __.NaN pattern, matching only NaNs values. Thanks @mhintz for adding this

const res = match<number | null>(NaN)
      .with(null, () => 'null!')
      .with(__.NaN, () => 'NaN!')
      .with(__.number, (x) => 'a number!')
      .exhaustive();

console.log(res)
// => 'NaN!'

Bugfix

Update the __.number pattern to also match on NaN values.

Since NaN has type number in TypeScript, there is no way to distinguish a NaN from a regular number at the type level. This was causing an issue where .exhaustive() considered all numbers handled by the __.number pattern even though NaN wasn't matched by it, resulting in possible runtime errors.

const res = match<number | null>(NaN)
      .with(null, () => 'null!')
      .with(__.number, (x) => 'a number!')
      // This used to throw at runtime because NaN wasn't matched by __.number
      .exhaustive();

console.log(res)
// => 'a number!'