E0308 error message does not suggest `to_string()` for converting from `&str` to `String`

[feadoor]

This snippet:

fn foo(s: String) {}

fn main() {
    let s = "this is a &str";
    foo(s);
}

results in the following compiler error:

error[E0308]: mismatched types
 --> src/main.rs:6:9
  |
6 |     foo(s);
  |         ^ expected struct `std::string::String`, found &str
  |
  = note: expected type `std::string::String`
             found type `&str`
  = help: here are some functions which might fulfill your needs:
          - .escape_debug()
          - .escape_default()
          - .escape_unicode()
          - .to_lowercase()
          - .to_uppercase()

error: aborting due to previous error

error: Could not compile `playground`.

To learn more, run the command again with --verbose.

It would be nice if this error message suggested the function which is actually most likely to be helpful here, which is to_string().

[arielb1]

I think it just never looks up traits in scope, because the traits in scope list is empty. cc @jseyfried again for re-running resolution during method lookup.

[zackmdavis]

(related: #45777, #42929)

[estebank]

Current output:

error[E0308]: mismatched types
 --> src/main.rs:5:9
  |
5 |     foo(s);
  |         ^
  |         |
  |         expected struct `std::string::String`, found &str
  |         help: try using a conversion method: `s.to_string()`
  |
  = note: expected type `std::string::String`
             found type `&str`