Clippy "explicit_iter_loop" suggestion doesn't compile.

[SuperCuber]

I have the following code:

const GRID_SIZE: usize = 100;
const BYTES_PER_COLOR: usize = 3;

fn flatten(grid: [[[u8; BYTES_PER_COLOR]; GRID_SIZE]; GRID_SIZE]) -> Vec<u8> {
    let mut flat = Vec::new();

    for row in grid.into_iter() {
        for color in row.iter() {
            flat.extend_from_slice(color);
        }
    }

    flat
}

Clippy gives the following lint:

warning: it is more idiomatic to loop over references to containers instead of using explicit iteration methods
  --> src/pixel_render.rs:33:16
   |
33 |     for row in grid.into_iter() {
   |                ^^^^^^^^^^^^^^^^ help: to write this more concisely, try: `&grid`
   |
   = note: #[warn(explicit_iter_loop)] on by default
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.166/index.html#explicit_iter_loop

After changing the code to the suggestion, it does not compile:

error[E0277]: the trait bound `&[[[u8; 3]; 100]; 100]: std::iter::Iterator` is not satisfied
  --> src/pixel_render.rs:33:5
   |
33 | /     for row in &grid {
34 | |         for color in row.iter() {
35 | |             flat.extend_from_slice(color);
36 | |         }
37 | |     }
   | |_____^ `&[[[u8; 3]; 100]; 100]` is not an iterator; maybe try calling `.iter()` or a similar method
   |
   = help: the trait `std::iter::Iterator` is not implemented for `&[[[u8; 3]; 100]; 100]`
   = note: required by `std::iter::IntoIterator::into_iter`

The real solution here is grid.iter().

My suggestion: somehow check that the suggestion compiles before making it.

[oli-obk]

We should just bail out on arrays with more than 32 elements, they don't implement any traits

My suggestion: somehow check that the suggestion compiles before making it.

That would be nice, but is really really hard

[SuperCuber]

@oli-obk yeah figured so, I guess the alternative is to not have lints that suggest noncompiling code :)

Didn't know arrays bigger than 32 didn't implement traits though, I think that's the thing that can be fixed by introducing integer parameters to generics?

[oli-obk]

I guess the alternative is to not have lints that suggest noncompiling code :)

Yea I'm working on automating the detecting of bad suggestions ;) But it's nontrivial. See rust-lang/rust#45516 for some thoughts

I think that's the thing that can be fixed by introducing integer parameters to generics?

jup

[lukasstevens]

Unfortunately I am unable to reproduce this issue with the newest version of clippy. Can anyone confirm that this occurs with the newest version?

EDIT: Never mind, I forgot the #![plugin(clippy)] directive. I am having a look at this issue now.