isolatedDeclarations should not have warning for functions that have no return statements #58330

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1. jakebailey commented on Apr 26, 2024

   

   Jake Bailey (jakebailey)

   on Apr 26, 2024

   Last edited by jakebailey

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   This error is intentional; a function without a return may not always be void.

   declare function fail(): never;
   export function f() {
   	fail();
   }
   export const g = () => {
   	fail();
   }

   Is:

   export declare function f(): void;
   export declare const g: () => never;

   This can't be determined without type analysis, so is disallowed under isolatedDeclarations.

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2. RyanCavanaugh commented on Apr 26, 2024

   

   Ryan Cavanaugh (RyanCavanaugh)

   on Apr 26, 2024

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   Correct error for function expressions, but not function declarations - declarations won't infer never
3. jakebailey commented on Apr 26, 2024

   

   Jake Bailey (jakebailey)

   on Apr 26, 2024

   Last edited by jakebailey

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   #58331 is indiscriminate in what it affects; if we want to allow this for function declarations only, that may be possible, but it sure seems like an extra inconsistency just to avoid writing : void (and how often do people define a noop function?).
4. Jack-Works commented on Apr 26, 2024

   

   Jack Works (Jack-Works)

   on Apr 26, 2024

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   hmm, I didn't think of never, so the function expression part is wrong. But I find it annoying to write : void for obviously clear function declarations.
5. Ryan Cavanaugh (RyanCavanaugh)

   added

   SuggestionAn idea for TypeScriptAn idea for TypeScript

   In DiscussionNot yet reached consensusNot yet reached consensus

   DeclinedThe issue was declined as something which matches the TypeScript visionThe issue was declined as something which matches the TypeScript vision

   and removed

   In DiscussionNot yet reached consensusNot yet reached consensus

   on May 2, 2024
6. RyanCavanaugh commented on May 3, 2024

   

   Ryan Cavanaugh (RyanCavanaugh)

   on May 3, 2024

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   Discussed and we don't want to make it untenable to, in the future, change the rules around function declaration return type inference. For example, it's maybe preferable that

   function dofail() {
     Debug.fail("oops");
   }

   have an inferred return type of never (as it would if written as a function expression) rather than void.
7. Ryan Cavanaugh (RyanCavanaugh)

   closed this as completedon May 3, 2024