declare function func(): void;
function returnsMethod(): (this: Foo) => void {
    return func; // Error
}

declare function takesMethod(method: (this: Foo, s: string) => string);
takesMethod(s => s); // Works - lambda will transpile with a dummy parameter

function returnsMethod(): (this: Foo, s: string) => string {
    return s => s; // Works
}

declare class Foo {}
interface Method {
    (this: Foo, s: string): string;
}
const a: Method[] = [s => s]; // Error - cannot convert function to method
const b: Method[] = [function(this: Foo, s) { return s; }]; // Workaround