Array.prototype.includes type definition issue

[amerllica]

Bug Report

🔎 Search Terms

I saw a but in Array.prototype.includes type:

interface Array<T> {
    /**
     * Determines whether an array includes a certain element, returning true or false as appropriate.
     * @param searchElement The element to search for.
     * @param fromIndex The position in this array at which to begin searching for searchElement.
     */
    includes(searchElement: T, fromIndex?: number): boolean;
}

The above type definition comes from microsoft/TypeScript, and this is not a true generic type, you must not pass T to the searchElement, because the searchElement could be anything.

🕗 Version & Regression Information

version: 4.2.4

💻 Code

type name = 'amer' | 'saeed' | 'ahmad';
const arr = ['amer', 'saeed'].includes(name); // here it returns this error, which is not correct
//// TS2345: Argument of type '"amer" | "saeed" | "ahmad"' is not assignable to parameter of type '"amer" | "saeed"'.   Type '"ahmad"' is not assignable to type '"amer" | "saeed"'.

🙁 Actual behavior

it returns a type error, told developer the type of argument in includes function must be the type of items in array.

🙂 Expected behavior

It should allow developer to insert anything in includes function.

[jcalz]

Duplicate #48247 and others.

You forgot to fill out the “search terms” part of the template showing how you searched for existing issues before filing a new issue.

[amerllica]

I just closed this issue because of duplicated #48247