Type guard fails to determine non null tuple property

[irdkwmnsb]

🔎 Search Terms

"ts2322" "tuples" "null type guard"

🕗 Version & Regression Information

Typescript version 5.5.4

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.7.0-dev.20240828#code/C4TwDgpgBAIghsCAlOA7A5hAKuaBeKAbXkSgB8pUBXAGxoBpYFoLq6BdAKE4GMB7VAGdgUAE5pMALiaIUGbLigFCqCAHcZEABQBKRqo0ltO9gG5u-ISMTClUXUoB8UAN6coHqAEsAZvfHyhAAM7Ep4BGw05BQBmIQAjKHhEbQ0Oq7unlmiEMBUoqjmWQC+mR6WtgBG0sTMjEZJYhIQplAA9G1QWADKUABMAMx9fZzFQA

💻 Code

type DateRangeType = [Date | null, Date | null]

const range: DateRangeType = [new Date(), new Date()];

const test = () => {
    if (range[0] === null || range[1] === null) {
        return;
    }
    const b: [Date, Date] = range; // TS 2322
}

🙁 Actual behavior

Error on line const b: [Date, Date] = range; // TS 2322

🙂 Expected behavior

Type of range would be narrowed down to [Date, Date]

Additional information about the issue

No response

[jcalz]

Duplicate of #42384