I need to split a `String` (not `&str`) by another `String`:

```
use std::str::Split;

fn main() {
    let x = "".to_string().split("".to_string());
}

```

Why do I get this error and how to avoid it if I already have to operate on strings?

```none
error[E0277]: the trait bound `std::string::String: std::ops::FnMut<(char,)>` is not satisfied
 --> src/main.rs:4:32
  |
4 |         let x = "".to_string().split("".to_string());
  |                                ^^^^^ the trait `std::ops::FnMut<(char,)>` is not implemented for `std::string::String`
  |
  = note: required because of the requirements on the impl of `std::str::pattern::Pattern<'_>` for `std::string::String`

```

According to the #rust-beginners IRC channel, this might be an example of `Deref` failing in 1.20.0-nightly. [How to split a string in Rust?](https://stackoverflow.com/questions/26643688/how-to-split-a-string-in-rust) doesn't address the problem of splitting by `String`, not `&str`.