Bad diagnostic for bad lifetime syntax

[steveklabnik]

Consider this function:

fn hello() -> &str {
    "hello"
}

This gives a help note:

help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
help: consider giving it a 'static lifetime

This doesn't demonstrate how to do the syntax. So, if you screw it up:

fn hello() -> '&str {
    "hello"
}

(which you are likely to do if you are new because the lifetime syntax is foreign...)

Rust will give a very confusing diagnostic:

error: character literal may only contain one codepoint: '&
 --> <anon>:1:15
  |>
1 |> fn hello() -> '&str {
  |>               ^^

This seems like something we could improve.

[estebank]

Current output (since #55173) suggests the appropriate syntax:

error[E0106]: missing lifetime specifier
 --> src/lib.rs:1:15
  |
1 | fn hello() -> &str {
  |               ^ help: consider giving it a 'static lifetime: `&'static`
  |
  = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from