🔎 Search Terms

noUncheckedIndexedAccess, findIndex, undefined

🕗 Version & Regression Information

Tried 5.8.2 and nightly (5.9.0-dev.20250310).

⏯ Playground Link

https://www.typescriptlang.org/play/?noUncheckedIndexedAccess=true&ts=5.8.2#code/MYewdgzgLgBAhgJwQLhmArgWwEYFMEDaAujALwwECMANDAEy0DMRA3AFCiSwCWAJgB5l4SAHQAzbmF4BJKbn4AKQaQB8MZeToBKdtzEwFfQQEJyAWkpaYAbzYx7MTtHWoMOfEMSEjrOw6cgADa4IoEgAOZKOmwAvmxAA

💻 Code

const arr: number[] = [1, 2, 3];
const idx = arr.findIndex(x => x == 2);
if (idx != -1) {
    const x: number = arr[idx];
    console.log(x);
}

🙁 Actual behavior

Type 'number | undefined' is not assignable to type 'number'.
  Type 'undefined' is not assignable to type 'number'.

🙂 Expected behavior

Code 'compiles' without errors.

Additional information about the issue

No response