infer of selective types

[Akimotorakiyu]

Search Terms

infer of selective types

Suggestion

infer of selective types

Use Cases

interface FunInterface {
  < R,P>(params: P): R;
}

let fun: FunInterface ;

let p ="123";
fun<number>("123");
// should be equivalent with `fun<number, typeof p>(p)`
// should be equivalent with `fun<number, string>(p)`

one more thing, Generics by default

function name(p){
  return p
}
// should be  equivalent with
// function name<P>(p:P){
//  return p
// }

const aName = name("someName")
// type of aName is string
const aNumber = name(123)
// type of aNumber is number

Examples

function deal<A extends unknown[], E>(event: E){
  return {
    event,
    fun:(fn:(...args:A))=>{
      eventBus.on(event,fn);
    }
  }
}

const eventName = "notify" as SomeEventType;

deal<[number]>(eventName );
// should be equivalent with `fun<[number], typeof eventName>(eventName );`
// should be equivalent with `fun<[number], SomeEventType>(eventName );`

one more thing, Generics by default

function name<A extends unknown[], B extends SomeType>(p1, a:A, p2:AKindType,  b: B){
  return {p1,a,p2,b}
}
// should be  equivalent with
// function name<A extends unknown[], B extends SomeType,T>(p1:T, a:A, p2:AKindType,  b: B){
//  return {p1,a,p2,b}
// }

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, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

[MartinJohns]

Sounds like a duplicate of #26242.

[Akimotorakiyu]

@MartinJohns not the same.

[purplesyringa]

The first example looks like a duplicate, the second one might be new.

[RyanCavanaugh]

The other part is a duplicate of #17428

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.