TypeScript: Control flow analysis for destructured discriminated unions

• TypeScript

  1,303 97,944 9.9 TypeScript

  TypeScript is a superset of JavaScript that compiles to clean JavaScript output.

  

The above is caught in Flow when exact types are enabled but not in TS.

TS issue https://github.com/microsoft/TypeScript/issues/12936

TS has a concept of "freshness" which catches some of these mistakes when you construct y right in the arguments of x, but it gets easily broken by accident and without a warning.

2. Nominal types, so you can have for example "Id" type that is a number but not to be mixed with other numbers, you can't just call a function that expects an Id with literal 42. Classes are nominal too, which I think is a solid choise.

3. Type variance & related safeguards

    function x(y: { foo: string | number}) {

• type-fest

  32 13,184 9.0 TypeScript

  A collection of essential TypeScript types

I know you're entirely right, but sometimes I see things like this in Typescript and although I can walk through it with enough pause, it kinda makes my head implode when I glance at it:

https://github.com/sindresorhus/type-fest/blob/main/source/r...

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