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unique symbol type lost after property is extracted from an object #43657
Description
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
Activity
RyanCavanaugh commentedon Apr 22, 2021
This is the intended widening behavior of
unique symbol, shown in a simpler example:A
unique symboltype is never transferred from one declaration to another through inference.typescript-bot commentedon Apr 24, 2021
This issue has been marked 'Working as Intended' and has seen no recent activity. It has been automatically closed for house-keeping purposes.