support native Set and Map values

[davidchambers]

Insertion order is respected, so show (new Set ([1, 2, 3])) ≠ show (new Set ([3, 2, 1])).

Sorting would be unnecessarily restrictive: Set a would satisfy Showable only if a satisfies Ord.

In various test suites we define eq which asserts that show (actual) = show (expected) before asserting that equals (actual) (expected) = true. We will now need to ensure that actual and expected have the same insertion order anywhere we apply eq to native Set or Map values.

[Avaq]

We will now need to ensure that actual and expected have the same insertion order anywhere we apply eq to native Set or Map values.

That's just a side-effect of how eq has been defined in terms of show, and not necessarily indicative of an implementation fault of show. I think it's perfectly acceptable.