`Pattern.nonNullable` does not behave as expected

[ItaiYosephi]

Describe the bug Pattern.nonNullable behave the same Pattern.not(Pattern.nullish)

Code Sandbox with a minimal reproduction case https://codesandbox.io/p/sandbox/thirsty-frog-9965h3?file=%2Fsrc%2Findex.ts%3A20%2C14

provided this code

enum AnimalType {
  Dog = "dog",
  Cat = "cat",
}

interface Animal {
  type?: AnimalType;
  name: string;
}

const animal: Animal = { name: "Bobbie" };

match(animal)
  .with(
    // replace the next line with:
    // { type: Pattern.not(Pattern.nullish) },
    { type: Pattern.nonNullable },
    ({ name, type }) => `${name} the ${type}`
  )
  .with({ type: Pattern.optional(Pattern.nullish) }, ({ name }) => name)
  .exhaustive();

match(animal)
  .with(
    { type: Pattern.not(Pattern.nullish) },
    { type: Pattern.nonNullable },
    ({ name, type }) => `${name} the ${type}`
  )
  // without `Optional` - there's no TS error, but there is runtime error
  .with({ type: Pattern.nullish }, ({ name }) => name)
  .exhaustive();

I get this ts error

Versions

• TypeScript version: 5.4.3
• ts-pattern version: 5.1.1
• environment: browser

[gvergnaud]

That's indeed a bug. I'll take a closer look when I get some time. In the meantime using P.not(P.nullish) instead of P.nonNullable is the alternative I'd recommend if you run into this issue

TS Playground for reference

[gvergnaud]

Fixed in 5.1.2!