Suggest returning an owned type instead of a reference in E0106

[scottmcm]

Lifetime elision doesn't allow the following:

fn fizzbuzz() -> &str {
    todo!()
}

The current message has a great hint, but only suggests -> &'static str.

It would be nice if it could also suggest -> String, which would be the better choice for this example.

So maybe it would result in an error something like the following:

error[E0106]: missing lifetime specifier
 --> src/lib.rs:1:18
  |
1 | fn fizzbuzz() -> &str {
  |                  ^ expected named lifetime parameter
  |
  = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
help: consider returning an owned value instead
  |
1 | fn fizzbuzz() -> String {
  |                  ^^^^^^
help: or, if this only returns literals or globals, using the `'static` lifetime
  |
1 | fn fizzbuzz() -> &'static str {
  |                  ^^^^^^^^

(Ideally the error can get the corresponding owned type through ToOwned, but just having individual message for &impl Sized and &[T] and &[str] would cover pretty much everything here.)

This idea inspired by the conversation in https://users.rust-lang.org/t/why-not-automatic-inference-of-static-in-foo-str/47913?u=scottmcm

[veera-sivarajan]

Output on rustc 1.79.0:
For &str:

error[E0106]: missing lifetime specifier
 --> <source>:1:18
  |
1 | fn fizzbuzz() -> &str {
  |                  ^ expected named lifetime parameter
  |
  = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
help: consider using the `'static` lifetime, but this is uncommon unless you're returning a borrowed value from a `const` or a `static`
  |
1 | fn fizzbuzz() -> &'static str {
  |                   +++++++
help: instead, you are more likely to want to return an owned value
  |
1 | fn fizzbuzz() -> String {
  |                  ~~~~~~

error: aborting due to 1 previous error

For &[u8]:

error[E0106]: missing lifetime specifier
 --> <source>:1:18
  |
1 | fn fizzbuzz() -> &[u8] {
  |                  ^ expected named lifetime parameter
  |
  = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
help: consider using the `'static` lifetime, but this is uncommon unless you're returning a borrowed value from a `const` or a `static`
  |
1 | fn fizzbuzz() -> &'static [u8] {
  |                   +++++++
help: instead, you are more likely to want to return an owned value
  |
1 | fn fizzbuzz() -> Vec<u8> {
  |                  ~~~~  ~

[scottmcm]

Thanks @veera-sivarajan, that sounds like fixed to me!