New lint: Suggest str::strip_* over str::{starts,ends}_with and slicing it

[tesuji]

Categories: Performance, Correctness, complexity

Using str::strip removes the panic code inserted by slicing with pattern length.
Also it removes the need for duplicating/storing pattern used by str::{starts,ends}_with and (str[len..] or str[..len]).
Which it may removes the typing mistakes (do not repeat yourself).

Auto-apply suggestion ability

• Unspecified
• It's hard to make correct suggestion because:
  • it requires changing code/block structure.
  • it introduces a new binding which you have to give a name.

What it does

Suggest using strip_{prefix,suffix} over str::{starts,ends}_with and slicing by pattern's length.

Known problems

None.

Example

let s = "hello, world!";
if s.starts_with("hello, ") {
    // Or s[7..] ...
    assert_eq!(s["hello, ".len()..].to_uppercase(), "WORLD!");
}

Could be written as:

let s = "hello, world!";
if let Some(tail) = s.strip_prefix("hello, ") {
    assert_eq!(tail.to_uppercase(), "WORLD!");
}

[ghost]

I started on this. I should have a pull request ready sometime soon.