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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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@sceutre

Description

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">'.

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    Domain: Conditional TypesThe issue relates to conditional typesNeeds ProposalThis issue needs a plan that clarifies the finer details of how it could be implemented.SuggestionAn idea for TypeScript

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