Switch to quickcheck 1.0

[ziutech]

As far as I understand the only breaking change was published in this commit.

I found two significant differences:

1. signature for Arbitrary::arbitrary changed
2. it's no longer possible to call RngCore::next_u32

I changed every call to RngCore::next_u32 to u32::arbitrary. It was based purely on intuition, and seems to be wrong. The tests build, but don't pass — somewhere it tries to allocate more memory than max of u32. As I am writing this I'm not sure how to solve this. I would have to get more insight into how quickcheck works and why the tests are implemented the way they are.

[danjl1100]

Looking at this from the stream's mention of #8, the failing test seems to be the with_cap function in tests/quick.rs

fn with_cap(cap: usize) -> bool {
    let vs: Vc<u8> = Vc::with_capacity(cap); // <-- attempts to allocate for arbitrary `usize`
    println!("wish: {}, got: {} (diff: {})", cap, vs.capacity(), vs.capacity() as isize - cap as isize);
    vs.capacity() >= cap
}

It seems like before this PR, in quickcheck 9.2, the only cap sizes tested were powers of 2, ending below 256. Unclear to me where this upper bound was coming from.
Note: I found this by adding a panic before the allocation if the size is too large (println/eprintln did not seem to come through?).
I understand quickcheck is RNG-driven, but I'm not seeing any fails before this PR with this diagnostic added:

 fn with_cap(cap: usize) -> bool {
+    if cap > 256 {
+        panic!("{}", format!("about to test cap {cap}...")); // Rust pre-2021 edition feels odd :)
+    }
     let vs: Vc<u8> = Vc::with_capacity(cap);
     println!("wish: {}, got: {} (diff: {})", cap, vs.capacity(), vs.capacity() as isize - cap as isize);
     vs.capacity() >= cap
 }

But now in quickcheck >=1.0, the sizes tested are more what we would expect for an arbitrary usize. The test aborts when trying to allocate ~100GB (more than local RAM), before quickcheck gets to try finding a miminal failing size.

Echoing @ziutech's sentiment, I am not sure what range of input this specific Vc::with_capacity test is meant to accept.

[d2weber]

The behaviour of quickcheck changed in a way, that the size parameter does not anymore limit the range of the generated values. It now is only used for the number of values generated. The default size is 100.
BurntSushi/quickcheck@71d743a

Edit: there is an unresolved issue asking for a way to specify the generated range: BurntSushi/quickcheck#267

[jonhoo]

Ah, that test is arguably a little silly, but I would do something like use a u8::arbitrary(g) and then just cast it to usize. That tests as much as we care about for that call I believe.

[jonhoo]

This looks great now, thanks!