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Explicitly annotated unique symbols are widened in return positionsΒ #55361
Description
π Search Terms
widening return unique symbol
π Version & Regression Information
- This is the behavior in every version I tried
β― Playground Link
π» Code
export const test = Symbol()
export function fn() {
const alias: typeof test = test;
return alias
}π Actual behavior
this declaration file is emitted:
export declare const test: unique symbol;
export declare function fn(): symbol;π Expected behavior
this declaration file to be emitted:
export declare const test: unique symbol;
export declare function fn(): typeof test;Additional information
getWidenedLiteralLikeTypeForContextualReturnTypeIfNeeded calls getWidenedLiteralLikeTypeForContextualType and that calls getWidenedUniqueESSymbolType when there is no contextual type provided.
some issues that are (partially~) related:
#32242
#35896 (comment)
#36876
Activity
fatcerberus commentedon Aug 14, 2023
I think you may have just found the underlying cause of #53276 π
Andarist commentedon Aug 14, 2023
This issue is actually different and I'm already fixing it here: #54778 π Different code paths handle widening from initializers and widening at return positions.
RyanCavanaugh commentedon Aug 15, 2023
I'm not sure I'd call the existing behavior wrong, but it seems like a safe change to make
ssalbdivad commentedon Aug 15, 2023
Ryan Cavanaugh (@RyanCavanaugh) Are there other situations where casting the only return statement of a function doesn't dictate how it's inferred?
Could even be simplified down to just:
Andarist commentedon Aug 15, 2023
Are there any other cases in the compiler where an explicit type annotation like this gets stomped by the compiler and the type gets widened? I'm really curious about this. I assume that there is no place like this and that's why I'm calling this a bug. I also understand that symbols are somewhat special but as long as the symbol is publicly available (so the declaration emit can actually reference it) I think the annotation should be preserved.