The art of correctly matching related types to functions

I'm currently exploring the intricacies of type inference rules, and I've encountered a challenging scenario:

Here's the scenario:

interface Model{
    label?: string;
}

interface View<T>{
    cid?: string;
    model?: T;
}

class Foo {
    findWithModel<TModel extends Model, TView extends View<TModel>>(value: TModel): TView;
    findWithModel(value: string): any {
        return {cid: "2"};
    }
}

class AModel implements Model{
    constructor(public label: string){}
}

class AView<T extends Model> implements View<T>{
    cid = "1";
    model = null;
}

let f = new Foo();
let model = new AModel("test");

Essentially, I have an overload called findWithModel, where in one case it returns any and in another case it should return something like SomeView<SomeModel>. The problem arises when trying to achieve this as follows:

let trial1 = f.findWithModel<AView<AModel>, AModel>(model);
let trial2: AView<AModel> = f.findWithModel(model);

The first trial works fine but appears overly verbose. It feels redundant to pass AModel twice.

My assumption led me to believe that I should only provide type information in the result declaration for trial2, however, typescript interprets it as:

Foo.findWithModel<AModel, {}>(value: AModel): {}

This obviously results in an error:

Property 'cid' is missing in type '{}'

Is there a way to achieve this without using the excessively verbose method of passing AModel twice?

Answer №1

Are you open to receiving a return value of View<T> instead of the specific type defined in the generic constraint? If so, you can simply implement it as follows:

retrieveViewModel<TModel extends Model>(data: TModel): View<TModel> {
    ...
}

let result = example.retrieveViewModel(model); // result will have the type View<AModel>

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