Suggest replacing str::split with empty pattern with str::chars

[Ravenslofty]

What it does

I was helping a friend learn Rust by going through Advent of Code 2020, and they needed to split a &str into a Vec<char>. They found the str::split method, and wrote string.split("").collect::<Vec<char>>(). While reviewing their code, this tripped me up a bit, since I would think of string.chars().collect::<Vec<char>>() instead. I think this would be a good candidate for a lint.

Advantage

• I think this is more intuitive than splitting with an empty pattern

Drawbacks

• as this playground shows, this is not a one-to-one replacement because str::split("") has leading and trailing empty strings.

Example

"hello world".split(""); 

The above should trigger a suggestion of replacing with

"hello world".chars();

[Vrajs16]

@rustbot claim