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Awaiting More FeedbackThis means we'd like to hear from more people who would be helped by this featureThis means we'd like to hear from more people who would be helped by this featureSuggestionAn idea for TypeScriptAn idea for TypeScript
Description
Suggestion
π Search Terms
variant accessors index signatures record
β Viability Checklist
My suggestion meets these guidelines:
- This wouldn't be a breaking change in existing TypeScript/JavaScript code
- This wouldn't change the runtime behavior of existing JavaScript code
- This could be implemented without emitting different JS based on the types of the expressions
- This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
- This feature would agree with the rest of TypeScript's Design Goals.
β Suggestion
Support for having Variant Accessors with index signature.
π Motivating Example
// Simple usage
interface NumberMap {
get [k: string](): number;
set [k: string](val: string | number);
}
const a: NumberMap = {}
a.test = '1';
a.test === 1;
// more complex
// makes number properties of an object to allow set `string`
type MakeStringAsNumber<T extends Record<string, any>> = {
get [ K in keyof T]: T[K]
set [ K in keyof T]: T[K] extends number ? T[K] | string : T[K]
}
declare const a: MakeStringAsNumber<{ a: boolean, b: number, c: string }>
a.b = '42'; // I want to have this avalible
a.c = '112'
// @ts-expect-error 'a' is boolean
a.a = '2'
π» Use Cases
The use case for this feature is vue 3 reactivity.
In Vue 3 there's Ref<T>
(simplified as { value: T}
) and Reactive<UnwrappedRef<T>>
(unwraps {value: T}
to T
, recursive)
This feature would allow us to generate a type which can accept a Ref<T> | T
Basically:
const r = ref({ a: 1} )
r.value.a = 1
const a = reactive(r)
a.a // 1
On a reactive
/ref
object the set in typescript must be UnwrappedRef<T>
which is not true, because when you assign to a reactive
it will unwrap the value:
const r = ref({a:1});
const a = ref({
r
}) // results in `{ r: { a: 1 } }`
a.r = r; // typescript error because `r` is `Ref<T>` instead of `UnwrappedRef<T>`, but it works at runtime.
fardolieri, rozzzly, AlexGalays, whzx5byb, MathisBullinger and 99 moreExE-Boss and jetjoyaquawa, ztiromoritz, schelmo, osnoser1, reslear and 16 moreExE-Boss, jetjo and rrain0
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Awaiting More FeedbackThis means we'd like to hear from more people who would be helped by this featureThis means we'd like to hear from more people who would be helped by this featureSuggestionAn idea for TypeScriptAn idea for TypeScript