myers/middle_snake: correct safety doc

[jonathantanmy]

Hello, one last thing that my colleague noticed. This PR is assuming that bounds_check is correct - I haven't scrutinized the algorithm enough to determine what the exact bounds are.

Again, feel free to change to meet your project's style. (This passes cargo fmt, but I don't know how long you prefer your documentation lines to be.)

Commit message follows:

In the documentation for MiddleSnakeSearch::new, the safety constraints described on the data pointer do not exactly match how the class uses it. It is stored as the kvec field, and looking at the write_xpos_at_diagonal, x_pos_at_diagonal, and pos_at_diagonal functions (a search of kvec in the source code revealing that all access to kvec go through one of these functions):

• writes could happen, not only reads
• the range of access is as described in the bounds_check function

Therefore, update the documentation accordingly.

[pascalkuthe]

I think I wrote this safety comment very early when I started working on this and then didn't update it as the code evolved (as it's just an internal function). I did a patch release for the last fix since that could feasibly have negative effects but since this is just internal documentation and doesn't affect users I will merge this without cutting a release

[jonathantanmy]

Makes sense. Thanks for taking a look.