Confusing error message when trait bound is "satisfied" from different version of same crate

[bugadani]

Hi!

I was trying to make the following extension to heapless in my project:

use heapless::spsc::Consumer;
use heapless::spsc::MultiCore;
use generic_array::ArrayLength;
pub trait ConsumerExt {
    fn flush(&mut self);
}

impl<T, N> ConsumerExt for Consumer<'_, T, N, usize, MultiCore>
where
    N: ArrayLength<T>,
{
    fn flush(&mut self) {
        while self.dequeue().is_some() {}
    }
}

In this case, the compatible type is reexported as heapless::ArrayLength;
I now understand that my generic_array::ArrayLength was from a mismatching version of generic_array. Regardless, the error message is extremely confusing:

error[E0277]: the trait bound `N: generic_array::ArrayLength<T>` is not satisfied
  --> src\utils\mod.rs:58:14
   |
58 |     fn flush(&mut self) {
   |              ^^^^^^^^^ the trait `generic_array::ArrayLength<T>` is not implemented for `N`
   | 
  ::: C:\Users\bugad\.cargo\registry\src\github.com-1285ae84e5963aae\heapless-0.5.5\src\spsc\split.rs:35:8
   |
35 |     N: ArrayLength<T>,
   |        -------------- required by this bound in `heapless::spsc::split::Consumer`
   |
help: consider further restricting this bound
   |
56 |     N: ArrayLength<T> + generic_array::ArrayLength<T>,

[estebank]

Current output in stable mentions the right re-export:

error[E0277]: the trait bound `N: heapless::ArrayLength<T>` is not satisfied
  --> src/main.rs:8:28
   |
8  | impl<T, N> ConsumerExt for Consumer<'_, T, N, usize, MultiCore>
   |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `heapless::ArrayLength<T>` is not implemented for `N`
   |
note: required by a bound in `Consumer`
  --> /home/gh-estebank/.cargo/registry/src/index.crates.io-6f17d22bba15001f/heapless-0.5.6/src/spsc/split.rs:35:8
   |
33 | pub struct Consumer<'a, T, N, U = usize, C = MultiCore>
   |            -------- required by a bound in this struct
34 | where
35 |     N: ArrayLength<T>,
   |        ^^^^^^^^^^^^^^ required by this bound in `Consumer`
help: consider further restricting this bound
   |
10 |     N: ArrayLength<T> + heapless::ArrayLength<T>,
   |                       ++++++++++++++++++++++++++

error[E0277]: the trait bound `N: heapless::ArrayLength<T>` is not satisfied
  --> src/main.rs:12:19
   |
12 |     fn flush(&mut self) {
   |                   ^^^^ the trait `heapless::ArrayLength<T>` is not implemented for `N`
   |
note: required by a bound in `Consumer`
  --> /home/gh-estebank/.cargo/registry/src/index.crates.io-6f17d22bba15001f/heapless-0.5.6/src/spsc/split.rs:35:8
   |
33 | pub struct Consumer<'a, T, N, U = usize, C = MultiCore>
   |            -------- required by a bound in this struct
34 | where
35 |     N: ArrayLength<T>,
   |        ^^^^^^^^^^^^^^ required by this bound in `Consumer`
help: consider further restricting this bound
   |
10 |     N: ArrayLength<T> + heapless::ArrayLength<T>,
   |                       ++++++++++++++++++++++++++

error[E0599]: the method `dequeue` exists for mutable reference `&mut Consumer<'_, T, N>`, but its trait bounds were not satisfied
  --> src/main.rs:13:20
   |
13 |         while self.dequeue().is_some() {}
   |                    ^^^^^^^ method cannot be called on `&mut Consumer<'_, T, N>` due to unsatisfied trait bounds
   |
   = note: the following trait bounds were not satisfied:
           `N: heapless::ArrayLength<T>`