ndarray-rand doesn't work with rand 0.7

[ngoldbaum]

The test program in the ndarray-rand documentation doesn't compile with rand 0.7:

main.rs:

use ndarray::Array;
use ndarray_rand::RandomExt;
use rand::distributions::Uniform;

fn main() {
    let a = Array::random((2, 5), Uniform::new(0., 10.));
    println!("{:8.4}", a);
}

cargo.toml:

[package]
name = "rand-test"
version = "0.1.0"
authors = ["Nathan Goldbaum <nathan12343@gmail.com>"]
edition = "2018"

[dependencies]
ndarray = { version = "0.12", features = ["blas"] }
ndarray-rand = "0.9"
rand = "0.7"

compile error:

    Updating crates.io index
   Compiling rand-test v0.1.0 (/home/goldbaum/Documents/rand-test)
error[E0277]: the trait bound `rand::distributions::uniform::Uniform<{float}>: rand::distributions::Distribution<_>` is not satisfied
 --> src/main.rs:6:13
  |
6 |     let a = Array::random((2, 5), Uniform::new(0., 10.));
  |             ^^^^^^^^^^^^^ the trait `rand::distributions::Distribution<_>` is not implemented for `rand::distributions::uniform::Uniform<{float}>`
  |
  = note: required by `ndarray_rand::RandomExt::random`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.
error: Could not compile `rand-test`.

It works if I specify rand = "0.6" in cargo.toml.

Apologies if this issue is documented already and I've missed it.

[ngoldbaum]

perhaps i'm hitting rust-lang/rust#22750. I guess if ndarray-rand doesn't support rand 0.7 that should be encoded in ndarray-rand's cargo.toml?

[ngoldbaum]

Ah I see it does specify 0.6 explicitly:

ndarray/ndarray-rand/Cargo.toml

Line 15 in 98bf3b6

rand = "0.6.0"

[LukeMathWalker]

I had the exact same issue a couple of hours ago when working on rust-ndarray/ndarray-linalg#166 - I am little bit surprised by cargo's behavior here, because ndarray-rand does indeed specify 0.6.

I guess, overall, we should aim to keep close to the latest release of rand - #659 goes in the right direction.

[max-sixty]

Any ideas why cargo doesn't use 0.6.0?

Is there some complexity with there being a workspace?

Seems unlikely but @ngoldbaum if the cargo.toml above includes the full semver version rand = "0.6.0" (with the trailing patch version included), does that work?

[ngoldbaum]

Argh, I'm sorry, I copy/pasted the cargo.toml that works. It does work if I explicitly depend on rand 0.6 and fails if I use rand 0.7. I've edited the issue to reflect that.

[max-sixty]

Ah OK that makes sense.

I had thought cargo would use the necessary version for each crate... Or at least state that there were conflicting versions - not sure why this silently breaks...

[jturner314]

Yeah, the bad error messages are an instance of rust-lang/rust#22750. Hopefully that'll get fixed at some point. This kind of issue has come up in the past with ndarray-rand (e.g. #530).

We should update ndarray-rand to use the latest version of rand (#659).