Should this proposal instead follow proposed Immutable ArrayBuffer pattern?

[erights]

The current state of this proposal would have .snapshot() of a mutable collection make an immutable copy. Without special implementation tricks(*), this would be expensive.

By contrast, https://github.com/tc39/proposal-immutable-arraybuffer has a zero-copy .toImmutable(), that "detaches" the data from the original collection, so the creation of the derived immutable collection is zero-copy without special implementation tricks.

(*) such as copy-on-write. At least for ArrayBuffers (including proposed Immutable ArrayBuffers) some implementations have expressed strong reluctance to implement such tricks. However, we don't yet know whether this reluctance would apply to other collections.