Using generic argument that extends something, stops inferring super keys when Exclude is used in addition to keyof and Pick

TypeScript Version: 3.1.0

Search Terms:
keyof extends pick exclude

Code

interface Base {
    base1: number;
    base2: number;
}

class Data<T extends Base> {
   alpha(k:keyof Pick<T, Exclude<keyof T, "base1">>) {   }
    beta(k:keyof Pick<T, keyof T>) {   }
}

function wrapped<T extends Base>() {
    let d = new Data<T>();
    d.alpha("base2"); // Argument of type '"base2"' is not assignable to parameter of type 'Exclude<keyof T, "base1">'. 
    d.beta("base2");  // works
}

Expected behavior:

Both alpha and beta should work.

Actual behavior:

Alpha does not work: ` Argument of type '"base2"' is not assignable to parameter of type 'Exclude<keyof T, "base1">'.

Playground Link:

Playground link

Related Issues:

Wesley Wigham (@weswigham)

Any thoughts on this one Wesley Wigham (@weswigham) Anders Hejlsberg (@ahejlsberg)?

I'm not sure, but I think I've found the same issue in v3.3.1. Please let me know if I'm wrong and I can open a new issue. This is a minimal reproduction, my real use case has the Exclude<Exclude type generated from nested react higher order components.

playground

interface Base {
    a: number;
    b: number;
    c: number;
    d: number;
    e: number;
    f: number;
}

type BaseA = Exclude<keyof Base, "a" | "c" | "b" | "d">;
type BaseB = Exclude<Exclude<keyof Base, "a" | "b">, "c" | "d">;

function testingBase(a: BaseA): BaseB {
    return a; // works, as expected
}

type A<T> = Exclude<keyof T, "a" | "c" | "b" | "d">;
type B<T> = Exclude<Exclude<keyof T, "a" | "b">, "c" | "d">;

function testing<T>(a: A<T>): B<T> {
    return a; // fails unexpectedly with "Type 'Exclude<keyof T, "a" | "b" | "c" | "d">' is not assignable to type 'Exclude<Exclude<keyof T, "a" | "b">, "c" | "d">'."
}

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Using generic argument that extends something, stops inferring super keys when Exclude is used in addition to keyof and Pick #27928

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Using generic argument that extends something, stops inferring super keys when Exclude is used in addition to keyof and Pick #27928

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DanielRosenwasser commented on Oct 25, 2018

apexskier commented on Feb 7, 2019

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