this is no longer any in functions of object literal assigned to prototype

[dragomirtitian]

Steps to reproduce

function Stream() {
}

Stream.prototype = {
    endOfStream: function (): boolean {
        return !this.tokens.length;
    },
};

Playground Link

Behavior with typescript@5.8

this was any so this.tokens was not an error.

Behavior with tsgo

this is typed as { endOfStream: () => any; } resulting in an error on this.tokens