This is the first time I hear of property-based testing, and I am intrigued. What is the difference between this and a sufficiently expressive structural type system?
The generators of T, typically called an Arbitrary<T> can be constrained, e.g Arbitrary<number> could generate any float or just non-negative integers. Ideally we would define an Arbitrary<float64> or Arbitrary<u64>.
A sufficiently expressive type system makes it easier to narrow the gap between what is generated and what is assignable to type T, making it clearer what the valid input domain to the SUT is.
It seems to me that this is more or less the same thing, but Monte Carlo. Like MCMC vs symbolic Bayesian inference.