Shadow variable not working in Rust, gives lifetime errors

Question

Here is my snippet:

pub fn abbreviate(mut phrase: &str) -> String {
    let mut tla = String::new();
    phrase = phrase.replace("-", "");
}

Gives this error

1 | pub fn abbreviate(mut phrase: &str) -> String {
  |                               ---- expected due to this parameter type
...
4 |     phrase = phrase.replace("-", "");
  |              ^^^^^^^^^^^^^^^^^^^^^^^
  |              |
  |              expected `&str`, found struct `String`
  |              help: consider borrowing here: `&phrase.replace("-", "")`

if I follow the suggestion

pub fn abbreviate(mut phrase: &str) -> String {
    let mut tla = String::new();
    phrase = &phrase.replace("-", "");
}

I get this lifetime compile error

1 | pub fn abbreviate(mut phrase: &str) -> String {
  |                               - let's call the lifetime of this reference `'1`
...
4 |     phrase = &phrase.replace("-", "");
  |     ----------^^^^^^^^^^^^^^^^^^^^^^^- temporary value is freed at the end of this statement
  |     |         |
  |     |         creates a temporary which is freed while still in use
  |     assignment requires that borrow lasts for `'1`

This works but is ugly:

pub fn abbreviate(mut phrase: &str) -> String {
    let mut tla = String::new();
    let phrase2 = &phrase.replace("-", "");
}

Why can I not shawdow the phrase variable? Can somebody please explain the above compiler error about lifetimes?