Domain: BinderHelp WantedPossible Improvement
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Description
🔎 Search Terms
Parameter cannot reference identifier declared after it, ts(2373)
🕗 Version & Regression Information
This is the behavior in every version I tried, and I reviewed the FAQ for entries about anything related (and found nothing).
⏯ Playground Link
💻 Code
/**
* This function throws `ReferenceError: Cannot access 'length' before initialization` at runtime.
*
* TS correctly reports `ts(2373)`. 👍
*/
export const truePositive = <const T>({ [length - 1]: finalItem, length }: readonly T[]): T | undefined => {
return finalItem;
};
/**
* This function works fine at runtime.
*
* TS **in**correctly reports `ts(2373)`. 👎
*/
export const falsePositive = <const T>({ length, [length - 1]: finalItem }: readonly T[]): T | undefined => {
return finalItem;
};
🙁 Actual behavior
A false positive ts(2373) is being reported in a situation where we can determine statically that what the report warns about is not taking place.
Ironically, the false positive ts(2373) might represent a real bug in TS' own modeling of declaration order.
🙂 Expected behavior
No false positive ts(2373) being reported.
Additional information about the issue
To be clear:
In the falsePositive case, we can statically determine that length is declared prior to being used.