Repository navigation
never cannot be spread into object, but it can be spread into JSX props #48556
Description
Bug Report
🔎 Search Terms
- props
- never
- spread
🕗 Version & Regression Information
- This is the behavior in every version I tried, and I reviewed the FAQ for entries about jsx,
never, and spreads. This seems like a design limitation.
⏯ Playground Link
Playground link with relevant code
💻 Code
// @ts-ignore
const obj: never = {}
const obj2 = {...obj}
const el = <div {...obj} />🙁 Actual behavior
As seen in kiliman/remix-params-helper#19, never is able to be spread into JSX props, even though never cannot be spread into objects. This seems odd to me as both compile to Object.assign. See screenshots:
TypeScript prevents spreading never into an object:
But spreading never into props works fine:
🙂 Expected behavior
never should be prevented from spreading into jsx props, just like it cannot be spread into objects.
Activity
Josh-Cena commentedon Apr 15, 2022
I wish spreading
neveris allowed—if anything it should be allowed in objects as well.neverextendsobjector any object type, so from a soundness perspective, I don't think this is unsafe. If it is compiled toObject.assign({}, obj), thenobjbeingneveris also fine because it's simply a top-type in parameter. From an ergonomics perspective, I often use...(props as never)in cases where TS can't reason the type properly, like a simple polymorphic component:The
neverhere reads well to me because props can be naturally seen as function parameters in the context of functional components. Ifneveris disallowed here, I'd have to do(props as any), which is undesirable because (a) it's less safe (though not so much) compared toneverand (b) it's banned by ESLint for good reason and I don't want to disable it for this particular case.