Generating a list of size N where each element is distinct.

I'm proposing something like:

def sizedDistinctListOf[T](size: Int, gen: Gen[T], eq: (T, T) => Boolean): Gen[List[T]]

In my own codebase, I've got something similar where T is constrained by the Eq typeclass from Cats. This allows me to define what distinctiveness means. From my understanding, ScalaCheck has no dependency on Cats.

For instance, you may have a case class Person(name: String, age: Int) and for a specific scenario, you might want to generate List[Person] where each element contains a different name and age pair, whereas for some other cases, you might want to generate List[Person] where each element has a different age.

Happy to submit a PR if people find this useful.

Start by reviewing ScalaCheck's existing Gen and List-generation APIs, then compare the proposed sizedDistinctListOf signature with current generator conventions. Done means a generator can produce lists of the requested size while enforcing distinctness through the supplied equality function, with tests covering different notions of distinctness.