Prefer constraint type for object literal completion

[asvetliakov]

Fixes #9900
Fixes #12968

Store constraint type when inferring and prefer it when resolving contextual type for completion.
I'm not sure what i'm doing it by correct way, anyway i just want to move these issues forward 😃

[DanielRosenwasser]

I feel like a better fix would be for the language service to use the apparent type of the contextual type when it comes to completions (but only if the contextual type is not a primitive type).

It used to be the case that the language service's concept of getContextualType was intermingled with the apparent type (and was made explicit with d8d72aa).

[DanielRosenwasser]

This actually won't work for intersection types or type parameters that are constrained by other type parameters.

[asvetliakov]

Can you provide me few cases?
I tried following:

interface X {
  a?: string;
  b?: string;
  abc?: string;
  // k: number;
}

interface X2 {
  e?: string;
  k?: number;
}
interface Complex<T> {
  a?: number;
  b?: T;
}

declare function foo<T extends X & X2>(x: T): any
declare function goo<K, T extends Complex<K>>(a: K, b: T): any;

foo({ // OK });
goo("", { // OK });

[asvetliakov]

The completion flow is already calling getApparentType in few places, but they don't return constraint type because object literal is being created as totally new anonymous type object. Not sure how to get correct type in this case.

[asvetliakov]

@DanielRosenwasser
I tried to use getApparentType approach, but object literals in function arguments are being created with new anonymous object type and don't contain necessary flag TypeVariable with resolvedBaseConstraint property. I tried to fill this information in createObjectLiteralType() or in getInferredType() but this broke checker completely - looks like it doesn't expect constraint type inferring for these object literals. (it even was not able to compile)
Let me know if you have any ideas

[mhegazy]

This is stale by now. @andy-ms was looking into something similar recently.