Error message for invalid string literal type could be improved

TypeScript Version: 2.0 Beta

Code

// A *self-contained* demonstration of the problem follows...
interface Foo {

    method(value: 'aa'): void;
    method(value: 'bb'): void;
    method(value: 'zz'): void;
    method(value: 'last'): void;
}

const x: Foo = {} as any;

x.method('bar'); // Error line

Expected behavior:

A more meaningful error message, e.g.

Argument of type "'bar'" is not assignable to parameter of type "'aa' | 'bb'|...|'last'"

Actual behavior:

Argument of type "'bar'" is not assignable to parameter of type "'last'"

I am finding this error message confusing, because the compiler picks the value of the last overload in order to report the error, and there is nothing special about the last value.