`unique symbol` type lost after property is extracted from an object

[targos]

Bug Report

Found while working on nodejs/node#38198

🔎 Search Terms

unique symbol object

⏯ Playground Link

Playground link with relevant code

💻 Code

declare const kSomeConstant: unique symbol;
declare function test(value: typeof kSomeConstant): void;
declare function getExports(): {
    kSomeConstant: typeof kSomeConstant;
    test: typeof test;
}

/*
    const exp: {
        kSomeConstant: typeof kSomeConstant;
        test: typeof test;
    }
*/
const exp = getExports()

// (property) kSomeConstant: typeof kSomeConstant
exp.test(exp.kSomeConstant)

// const constant: symbol
const constant = exp.kSomeConstant;
exp.test(constant);

🙁 Actual behavior

exp.test(constant) is an error, because constant's type is inferred to symbol instead of typeof kSomeConstant.

🙂 Expected behavior

The extracted variable should have the same type

[RyanCavanaugh]

This is the intended widening behavior of unique symbol, shown in a simpler example:

declare const kSomeConstant: unique symbol;
declare function test(value: typeof kSomeConstant): void;
const p = kSomeConstant;
test(p);

A unique symbol type is never transferred from one declaration to another through inference.

[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.