Failed function argument type inference inside nested object passed as argument

[beshanoe]

TypeScript Version: 2.7.1

Search Terms: infer

Code

interface IFooOptions<K extends string> {
  name?: string;
  value?: number;
  allFoos?: {[key in K]?: boolean }
  fn?: (allFoos: {[key in K]: string }) => void;
}

class Bar<T> {
  constructor(foos: {[key in keyof T]: IFooOptions<keyof T> }) {
    // ...
  }
}

const bar = new Bar({
  firstFoo: {
    name: "john",
    value: 3,
    allFoos: { // here allFoos infered
      firstFoo: true,
      nonexist: 'yep'
    }
  },
  secondFoo: {
    name: 'sandra',
    fn: allFoos => { // but here allFoos is any though the type of "fn" is infered correctly
      allFoos.nonexist = 2
    }
  }
});

const myFoo: IFooOptions<'one' | 'two'> = {
  name: 'adas',
  fn: allFoos => { //allFoos is infered right
    allFoos.nonexist = 2
  }
}

Expected behavior:

The allFoos argument inside fn field in the new Bar argument should have a type of

{
  firstFoo: string
  secondFoo: string
}

Actual behavior:

allFoos type is implicit any
Also it repoduces without using a class, just with plain generic function

Playground Link:
https://www.typescriptlang.org/play/index.html#src=interface%20IFooOptions%3CK%20extends%20string%3E%20%7B%0A%20%20name%3F%3A%20string%3B%0A%20%20value%3F%3A%20number%3B%0A%20%20allFoos%3F%3A%20%7B%5Bkey%20in%20K%5D%3F%3A%20boolean%20%7D%0A%20%20fn%3F%3A%20(allFoos%3A%20%7B%5Bkey%20in%20K%5D%3A%20string%20%7D)%20%3D%3E%20void%3B%0A%7D%0A%0Aclass%20Bar%3CT%3E%20%7B%0A%20%20constructor(foos%3A%20%7B%5Bkey%20in%20keyof%20T%5D%3A%20IFooOptions%3Ckeyof%20T%3E%20%7D)%20%7B%0A%20%20%20%20%2F%2F%20...%0A%20%20%7D%0A%7D%0A%0Aconst%20bar%20%3D%20new%20Bar(%7B%0A%20%20firstFoo%3A%20%7B%0A%20%20%20%20name%3A%20%22john%22%2C%0A%20%20%20%20value%3A%203%2C%0A%20%20%20%20allFoos%3A%20%7B%20%2F%2F%20here%20allFoos%20infered%0A%20%20%20%20%20%20firstFoo%3A%20true%2C%0A%20%20%20%20%20%20nonexist%3A%20'yep'%0A%20%20%20%20%7D%0A%20%20%7D%2C%0A%20%20secondFoo%3A%20%7B%0A%20%20%20%20name%3A%20'sandra'%2C%0A%20%20%20%20fn%3A%20allFoos%20%3D%3E%20%7B%20%2F%2F%20but%20here%20allFoos%20is%20any%20though%20the%20type%20of%20%22fn%22%20is%20infered%20correctly%0A%20%20%20%20%20%20allFoos.nonexist%20%3D%202%0A%20%20%20%20%7D%0A%20%20%7D%0A%7D)%3B%0A%0Aconst%20myFoo%3A%20IFooOptions%3C'one'%20%7C%20'two'%3E%20%3D%20%7B%0A%20%20name%3A%20'adas'%2C%0A%20%20fn%3A%20allFoos%20%3D%3E%20%7B%20%2F%2FallFoos%20is%20infered%20right%0A%20%20%20%20allFoos.nonexist%20%3D%202%0A%20%20%7D%0A%7D

[RyanCavanaugh]

@sandersn is this a duplicate of #22362 ?

This looks like a separate bug. The type parameter is escaping!

declare function f<T>(obj: { [key in keyof T]: { x?: number } }): T;
const t = f({ a: "a" }); // T is of type `T`

@beshanoe To fix the issue for now you should provide an explicit type argument. I'm don't think we should be able to infer T if we only ever see its keys anyway. At the comment at // here allFoos infered, there actually was no type argument inference, but if you hover over it you will still see a type -- that is just telling you the type of that object literal.

[beshanoe]

@Andy-MS regarding argument, I was saying about this place:

secondFoo: {
    name: 'sandra',
    fn: allFoos => { // but here allFoos is any though the type of "fn" is infered correctly
      allFoos.nonexist = 2
    }
  }

if you remove error line "nonexistent": "yep", you will see that fn's type is inferred when I hover it, however allFoos argument is any

I was confused by not getting errors (#22790). Now that I look at the original example again, there is a type error at nonexist: 'yep', so this may not actually be a bug.

[beshanoe]

@Andy-MS could you please explain your latest statement? Is it a bug? To me it looks like it is :)
I've encountered the same thing again, and it really prevents me from doing good typing in my app.
It's reproduced in 2.8.1 version
Here's is another example:
https://www.typescriptlang.org/play/index.html#src=class%20RouterProps%3CP%3E%20%7B%0D%0A%20%20props%3A%20P%0D%0A%7D%0D%0A%0D%0Aclass%20Component%3CP%3E%20%7B%0D%0A%20%20props%3A%20P%0D%0A%7D%0D%0A%0D%0A%2F%2F%20in%20'resolve'%20field%20I%20want%20to%20pass%20an%20object%20with%20keys%20from%20passed%20component's%20props%20and%20with%20functions%20as%20values%0D%0Ainterface%20IRoute%3CP%20%3D%20any%2C%20RP%20%3D%20any%3E%20%7B%0D%0A%20%20name%3A%20string%0D%0A%20%20component%3A%20Component%3CP%20%26%20RouterProps%3CRP%3E%3E%2C%0D%0A%20%20resolve%3F%3A%20%7B%20%5Bname%20in%20keyof%20P%5D%3F%3A%20(params%3A%20RP)%20%3D%3E%20Promise%3CP%5Bname%5D%3E%20%7D%0D%0A%7D%0D%0A%0D%0Afunction%20route%3CP%2C%20RP%3E(route%3A%20IRoute%3CP%2C%20RP%3E)%20%7B%0D%0A%20%20return%20route%0D%0A%7D%0D%0A%0D%0Aconst%20cmp%20%3D%20new%20Component%3C%7B%20foo%3A%20number%2C%20bar%3A%20string%20%7D%20%26%20RouterProps%3C%7B%20id%3A%20string%20%7D%3E%3E()%0D%0A%0D%0A%0D%0A%2F%2F%20if%20you%20hover%20'resolve'%20or%20'foo'%20object's%20field%2C%20the%20type%20is%20inferred%20correctly%2C%20saying%20that%20'params'%20arg%20is%20of%20type%20%7Bid%3A%20string%7D%0D%0A%2F%2F%20but%20when%20you%20hover%20'params'%2C%20it%20says%20that%20it's%20'any'%0D%0Aroute(%7B%0D%0A%20%20name%3A%20'sample-route'%2C%0D%0A%20%20component%3A%20cmp%2C%0D%0A%20%20resolve%3A%20%7B%0D%0A%20%20%20%20foo%3A%20params%20%3D%3E%20%7B%0D%0A%20%20%20%20%20%20alert(params.nonexistent)%20%2F%2F%20no%20error%20here%2C%20but%20should%20be%0D%0A%20%20%20%20%20%20return%20Promise.resolve(10)%20%2F%2F%20notice%20that%20the%20type%20of%20return%20value%20is%20enforced%2C%20namely%20change%2010%20to%20%22somestring%22%20and%20there%20will%20be%20an%20error%0D%0A%20%20%20%20%7D%0D%0A%20%20%7D%0D%0A%7D)

@beshanoe Try turning on --noImplicitAny -- no type was inferred for params. It looks like you need to explicitly provide type arguments to route. However, I did file an issue based on this at #23429.

[beshanoe]

@Andy-MS cool thanks, do you think this issue is a "good first issue"? Or it's too complicated? I just want to try to start contributing to TS :)

That seems like a pretty tough issue to me, since it involves type inference, and contextual typing of lambdas, and mapped types, all together.