Is your feature request related to a real problem or use-case?

I'm building a redux state type from other existing types. For some of the child types, we'll want to use DeepReadonly to make them immutable. Then, at the very top level (the combined state) I want to use DeepReadonly again to ensure that everything is actually immutable.

Unfortunately, this double application causes issues in some instances:

const foo: DeepReadonly<DeepReadonly<{bar: any[]}>> = {bar: ['hi']}
;[...foo.bar] // This errors with:
// Type '_DeepReadonlyObject<_DeepReadonlyArray<any>>' must have a '[Symbol.iterator]()' method that returns an iterator.

Describe a solution including usage in code example

Though the above example is contrived, it's sufficient to demonstrate the issue.

Who does this impact? Who is this for?

All who are combining multiple potentially readonly things into one readonly thing.

Describe alternatives you've considered (optional)

Only applying DeepReadonly at the very top, which is what I'm doing for now, but makes for more work.

Additional context (optional)

N/A