New lint: function takes slice and treats it as an array

What it does

Finds functions expecting a contiguous view of items of a const length taking a slice instead of an array.

Real world case: https://github.com/image-rs/jpeg-decoder/pull/215/files

Lint Name

fn_slice_param_is_array

Category

pedantic

Advantage

• Removes bounds checks/panics by giving the caller the responsibility to give the correct size
• Removes potential programming mistakes

Drawbacks

• Possible false positives?

Example

const LEN: usize = 64;

fn foo(items: &[u8]) {
    assert_eq!(items.len(), LEN);
    // or...
    debug_assert_eq!(items.len(), LEN);
    // or...
    let items = &items[..LEN];
}

Could be written as:

const LEN: usize = 64;

fn foo(items: &[u8; LEN]) {
}

Start by reviewing the proposed fn_slice_param_is_array lint and its Rust examples, including the jpeg-decoder case linked in the issue. Define detection around a constant-length slice used as an array, then validate the behavior against false positives and confirm the lint's pedantic categorization.