Can't assign to partial of intersection with mapped type over generic · Microsoft/TypeScript#56905

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Domain: Mapped TypesHelp WantedPossible Improvement

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Description

🔎 Search Terms

"mapped type", "mapped generic type", "intersection", "partial"

🕗 Version & Regression Information

Current version of Typescript, not sure if it's a regression

⏯ Playground Link

No response

💻 Code

Simple to reproduce:

type X = 'a' | 'b' | 'c'
const foo = <T extends X>() => {
    const result: Partial<{d:number} & {[P in T]: boolean}> = {
       // error: Type '{ d: number; }' is not assignable to type 'Partial<{ d: number; } & { [P in T]: boolean; }>'
        d: 1
    }
}

🙁 Actual behavior

I get an error

🙂 Expected behavior

I am able to use this type in general; I expect to be able to use a partial of it as well. The only thing I've found that satisfies the type is an empty object

Additional information about the issue