Flat typedef: type instantiation is excessively deep and possibly infinite

Problem in src/__spec__/flat.spec.ts:

// flat(0, iterable)
assert<{
  'depth = 0': IterableIterator<0 | 1 | 2>
  // ...
}>({
  'depth = 0': iter.flat(0, [0, 1, 2] as [0, 1, 2]), // Type instantiation is excessively deep and possibly infinite
  // ...
})

@KSXGitHub says this is an underlying issue in typescript-tuple

[conartist6]

I think we should follow the lead of the official typescript defs: https://github.com/microsoft/TypeScript/blob/d484163d0f8445aa7e1e7b944550922e99cf8305/lib/lib.es2019.array.d.ts#L45

I think any overload that has shouldFlat should return Iterable<any>.

The only tricky thing will be that we’ll need even more duplication than we have to support our curried/uncurried versions.

[conartist6]

Fixed in 7.x