Suggest `.collect()` when `Expected: FromIterator<Item>` and `<Found as FromIterator<Item>`

[estebank]

Code

fn main() {
    let input = "lowercase";
    let uppercase: String = input.chars().map(|c| c.to_ascii_uppercase());
}

Current output

error[E0308]: mismatched types
  --> $DIR/string-from-char-iterator-without-collect.rs:10:29
   |
LL |     let uppercase: String = input.chars().map(|c| c.to_ascii_uppercase());
   |                    ------   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `String`, found `Map<Chars<'_>, {closure@...}>`
   |                    |
   |                    expected due to this
   |
   = note: expected struct `String`
              found struct `Map<Chars<'_>, {closure@$DIR/string-from-char-iterator-without-collect.rs:10:47: 10:50}>`

Desired output

error[E0308]: mismatched types
  --> $DIR/string-from-char-iterator-without-collect.rs:10:29
   |
LL |     let uppercase: String = input.chars().map(|c| c.to_ascii_uppercase());
   |                    ------   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `String`, found `Map<Chars<'_>, {closure@...}>`
   |                    |
   |                    expected due to this
   |
   = note: expected struct `String`
              found struct `Map<Chars<'_>, {closure@$DIR/string-from-char-iterator-without-collect.rs:10:47: 10:50}>`
help: you can collect the `Iterator<Item = char>` into a `String`
   |
LL |     let uppercase: String = input.chars().map(|c| c.to_ascii_uppercase()).collect();
   |                                                                          ++++++++++

Rationale and extra context

No response

Other cases

Rust Version

1.97

Anything else?

No response

[mejrs]

Fixed in #156121