Warn on all slice methods that are panicky

What it does

This would be like clippy::indexing_slicing except that it would complain about all methods that are panicky based on an index out of bounds, not just the indexing operator.

Examples of methods that would be captured:

• slice::split_at and friends like slice::split_at_mut, slice::split_array_ref, ...
• slice::rotate_left and slice::rotate_right
• slice::swap

Lint Name

unchecked_index_out_of_bounds

Category

restriction

Advantage

• clippy::indexing_slicing covers many cases where it's desirable to avoid panics, but it is limited
• From experience reviewing code, index-out-of-bounds is a uniquely common class of errors, more so than other panic conditions
• A generic name like unchecked_index_out_of_bounds means that we could easily add more functions to the lint in the future

Drawbacks

• Slippery slope: where do we draw the line for what panics should be linted?
• clippy::indexing_slicing already exists, and perhaps a second, very similar lint would be confusing; should we add these functions to the same lint?

Example

let foo = my_slice.split_at(i);

Could be written as:

let foo = my_slice.checked_split_at(i).ok_or(...)?;

Note: checked_split_at doesn't exist yet, so in the mean time, code could be written as

if i > my_slice.len() {
    return Err(...);
}
#[allow(clippy::unchecked_index_out_of_bounds)] // checked above
let foo = my_slice.split_at(i);

Start by comparing the proposed lint with clippy::indexing_slicing and review the listed slice methods, including split_at, rotate_left, rotate_right, and swap. Done means agreeing whether this should be a separate lint or an extension of the existing one, defining its scope, and accounting for the absence of checked_split_at.