Goto definition after field exclusion should go to prop signature

[cevek]

TypeScript Version: master

Code

type OmitKeys<A, B> = {[P in Exclude<keyof A, B>]: A[P]}
interface Foo {
    a: number;
    b: string;
    c: boolean;
}
var c: OmitKeys<Foo, 'c'>;
c.a // goto definition doesn't work

Expected behavior:
Goto definition on c.a takes me to the Foo.a property

Actual behavior:
Goto definition doesn't work

[mhegazy]

At this point the compiler really can not track the key back to its declaration. Exclude<keyof A, B> just returns a list of literal types, then the map type generates a new type with properties of the same name..

[cevek]

I know that is not possible for everything, but maybe you can track some information where from came this symbol if it possible?

In the example above we definitely know that a symbol came from keyof Foo with defined position in the code.

[cevek]

Conditional types is very powerful feature, but with this behaviour without go to definition you also cannot rename refactor

[mhegazy]

The probable is once it goes through literal types, context is lost.. We would be happy to discuss a proposal on how this can be added.

interface I { a: number; }
declare const mapped: { [K in "a"]: I[K] };
mapped.a;

It seems like it should be possible to realize that we're taking I["a"] and therefore the property is derived from I.a? Seems like we could make getRootSymbols work here. Nathan Shively-Sanders (@sandersn)

[cevek]

Andy (Andrewkraft) (@Andy-MS) Here is corner case example where it doesn't work as we expected,
but anyway your solution is good and simple

interface I { a: number; }
interface X { a: string; }
declare const mapped: { [K in keyof X]: I[K] };
mapped.a;

[typescript-bot]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.

[sandersn]

Andy (Andrewkraft) (@Andy-MS) It's a matter of setting up a trail of synthetic symbols with pointers back to their original symbol. I don't know if getIndexAccessType do this when it is working on 0-order properties. If not, that's the place that would need to change.