IsExact fails with string enum item and string

Hi,

I can't make `IsExact` work with enums.

```ts
const foo = 'Foo';
enum A {
A1 = 'A1',
A2 = 'A2',
}

export const t1 = [foo, ['A1']] as const;
export type T1 = typeof t1[number];

export type T2 = typeof foo | readonly [A.A1]

assert>(true);
```

In the example above

- `T1` is `"Foo" | readonly ["A1"]`
- `T2` is `"Foo" | readonly [A.A1]`

I presume the issue is that for the type system `"A1"` is not exact to `A.A1`

Edit.
Following [your _another option_ approach](https://stackoverflow.com/a/55046618/1355416) (that doesn't require this library), I can see the origin of the error, which is extremely helpful.