Template literals as keys in object literals loosing type information

[falsyvalues]

Template literals as keys in object literals loosing type information, even with explicite type literals (works only with one exact type).

TypeScript Version: 4.1.2, 4.2.0-dev.20201210

Search Terms: Template literal types literal keys object keys literal types

Code

const template = <T extends string>(name: T) => ({
    [`${name}` as const]: name
});

Expected behavior:

const value = template ('TEST'); // const value: { TEST: "TEST"; }

Actual behavior:

const value = template ('TEST'); // const value: { [x: string]: "TEST"; }

Playground Link: https://www.typescriptlang.org/play?ts=4.2.0-dev.20201210&ssl=13&ssc=26&pln=13&pc=44#code/MYewdgzgLgBFCmBbADgGwIYIPphFLA7iAE4DWAlmAOZboRanwCeMAvDADwAqM8AHgjAATCDGjFKVAHwAKMOkTwAXDC4BKNlJgyA3gCgYhmAG0ABgBId8xQF9TMOjFCQoAXRXX4em2oDcevWdoGAA3dFQAV3gcPEISCmo2OCQ0TGjcfCIySVp6RiYZAHIuAFEAZS5CvxgAehqncGCwyOUYHRM+FXFJdxgAIlKKvt8YGwCg2AQUDGwMuOzqQnIoAAssVGX4YnCsKCZkeCTuXgF4YVFu6llPFWLyypgAHxhCgHkAJUKnl4A5V8qNKwtLoDEYzJZPHYHKIJr1PN4-ONGrBmlEYpl4jkNghtqgklNUrNYlkEjQCMs1titjs9gcioMASM6g0XKFwlEVO1jJ0xFAJNRegN7sNRkjWQSZtESZIjjx+IIRLz+dI5ApWncKlVNNp9EYTBYrGqoY5YR41Qj-IFkWyWvNSfiUpK7ZJ6fcqkz6hMbRy2qp7iohUMRmMgA

Related Issues: Might be related to #41631

[RyanCavanaugh]

This is correct behavior, since you could write template<"foo" | "bar">("foo") and would not get back an object with a bar property

[falsyvalues]

This is correct behavior, since you could write template<"foo" | "bar">("foo") and would not get back an object with a bar property

@RyanCavanaugh But this will not produce expected result either I won't get // const value: { foo: "foo"; } even if value is there.

[RyanCavanaugh]

I don't understand what you mean by that.

[typescript-bot]

This issue has been marked 'Working as Intended' and has seen no recent activity. It has been automatically closed for house-keeping purposes.

[falsyvalues]

@RyanCavanaugh Sorry I wasn't clear enough. Here is a example of expected behavior.

https://www.typescriptlang.org/play?ts=4.2.0-dev.20201210#code/MYewdgzgLgBFCmBbADgGwIYJgXhgCjHUXgC4YByAMxBHJgB8KAjdAJ3IEocA+fAbwBQMYTADaAAwAkfQsQC+4mOggxQkKAF0ys+ALkcA3AOMC10GADd0qAK7wA+gHcQrANYBLMAHMccJGkx4PAAiahBgwxgAeiiYAFEADQAFOIBhABU4gBFVcHMrWwdnN08vMj4YMLJQmmCDGDkgA

[dishuostec]

@falsyvalues I'v tried this, it seems work.

const template = <T extends string>(name: T): Record<`${T}`, `${T}`> => ({
    [`${name}`]: name,
} as any);

https://www.typescriptlang.org/play?ts=4.2.0-dev.20201210&ssl=7&ssc=11&pln=5&pc=1#code/PTDGHsDsGcBcAJYFMC2AHANgQ2fAvPABSRYpIBc8A5AGbjhXwA+1ARlgE5UCU+AfEQDeAKBDxx8ANoADACSCSZAL7T4WaPAgxYAXUqKko4Eu4BuYcK1xEqTDiT54AHgAq8JAA9kkACYa4HACWkADmfMSkFPAu3JQASkgQHD5OcoIuKgA08GkZ0gJ4AoQiElJpBip68AaZwkpqGliQAJ5mFlYIAG5YGACuSAD6AO7gHADWwSGOyOjYyIQARHTgC2bwYgCiABoAChsAwi4bACKaUNbdfYMj45OUgvDLlEv0C6bwSsJAA

[falsyvalues]

Hi @dishuostec!

Thanks for that. Looks returning type and as any did the job but would be nice achieve that without casting to any. @RyanCavanaugh Please take a look on example above.