Type inference error with generics and function 'this' typing

[use-strict]

TypeScript Version: [email protected]

Code

interface JQuery {
    each<T>(
        collection: T[],
        callback: (this: T, indexInArray: number, valueOfElement: T) => any
    ): any;
}

let $: JQuery;
let list: string[];
$.each(list, function() {
    return this != 'abc';
});

Expected behavior:
No errors
Actual behavior:
Operator '!=' cannot be applied to types 'T' and 'string'.

Notes:

• Explicit 'string' type parameter fixes the error: $.each<string>(...), although the type is correctly inferred to string even without it.

[sandersn]

Also, replacing return this != 'abc' with return this.indexOf('x') != 0 works. It seems related specifically to the binary operator with this.

[sandersn]

Well, that's only VS Code apparently. Now that I'm running a test case from the command line, this.indexOf('x') fails with the same error.

[sandersn]

A fix is up at #9746, although I need some expert help to make sure it's the correct fix (it's hacky, so it's probably not correct yet).