Omit properties from generic type which set by default and have extend

[Vardner]

TypeScript Version: 3.6.3
Omit extended generic type, type has no properties in common with type Pick Exclude

interface Bar {
    type: string;
    id?: string;
}

class Foo\<T extends Bar = Bar> {
    getParam (param: keyof Omit<T, 'type'>) {}

    test () {
        this.getParam('id');
    }
}

Expected behavior:
exclude the "type" property, and get in the available properties for the parameter "param" id and the rest that will be present in the interface because Bar is default param for T

Actual behavior:
Error "Type 'type' has no properties in common with type Pick <T, Exclude , 'type'>"

Playground Link:
https://stackblitz.com/edit/typescript-8zyjig

Related Issues: #24791

[RyanCavanaugh]

Operations like keyof Omit are higher-order and can't be related to concrete types like "id". From inspection we (humans) can say that "id" should be assignable to that type, but there's no way for TS to represent keyof Omit<T, 'type'>'s type in this format in order to answer that question.

[Vardner]

@RyanCavanaugh Maybe you should indicate this in the documentation so as not to mislead beginners like me? I expected that TypeScript would understand that a universal type expanding by a certain interface would be able to get keys from it. Expected behavior was that omit will get all keys from Bar because T is extending him

[Vardner]

@RyanCavanaugh I just want to note that if you extend a given class with a subclass of some kind and pass in a prepared object that is expanded by the Bar interface, then it begins to understand which keys need to be sorted out. That is, this problem can be fixed with a crutch by increasing the chain of inheritance by 1. You can see that in file index2.ts https://stackblitz.com/edit/typescript-8zyjig

[RyanCavanaugh]

Which documentation pages had you referred to before logging this? I'm trying to figure out which one to potentially add the information to.

[Vardner]

@RyanCavanaugh this one https://www.typescriptlang.org/docs/handbook/utility-types.html

[vipcxj]

@RyanCavanaugh what does high-order mean?
why TS know how to deal with keyof Omit<Bar, 'type'>
playground
Is there some limits on generic type or Omit?

[mykwillis]

Something seems a little fishy here, because it seems TypeScript is able to properly build a list of a generic type's properties with keyof (i.e., if that generic type is specified to extend from another type), but it is not able to do the same thing with Exclude. It wouldn't seem (to an outsider) that these should be different problems.

See for example this example from https://stackoverflow.com/questions/64920228/using-typescript-exclude-with-generic-type