rmap / *recursion-limit* not respected through custom generators

In all cases where a custom generator is used, the recursion limit is not respected.

This limitation becomes clear when one tries to build a recursive spec around e. g. s/coll-of because it uses a custom generator via s/coll-gen. Running s/exercise on it quickly blows the stack.

Here is an example for illustration with s/map-of

Even though s/or implements recursion checking, it is deceived here and not able to detect itself being called subsequently because the custom generator of s/coll-of (used in s/map-of) doesn't/can't pass rmap (keeping track of recursion calls) through to s/or's gen*.

For the concrete case, coll-of-impl could be implemented that would implement a gen* that passes on rmap.

For the general case of custom generators the challenge would be that test.check generators don't take and pass on rmap to generators of specs they potentially reuse and that there is no well-defined behavior for what they themselves should do when the recursion-limit has been reached. Ideas are:

• reduce generator size when recursion is detected (this is the strategy used in recursive specs of test.check use(d)?)

• expose the recursion-limit / rmap mechanism to the user so that custom generators can pass it on to subsequent calls of specs. E. g. a custom generator is passed a context object that it should pass to s/gen as an optional argument