Better error for missing tuple pattern in args

[Xion]

Playground link

fn main() {
    let v = vec![1, 2, 3];
    let v2: Vec<_> = v.into_iter().enumerate().map(|i, x| i).collect();
    println!("{:?}", v2);
}

Currently, this produces a somewhat confusing error:

error[E0593]: closure takes 2 arguments but 1 argument is required
 --> src/main.rs:3:48
  |
3 |     let v2: Vec<_> = v.into_iter().enumerate().map(|i, x| i).collect();
  |                                                ^^^ -------- takes 2 arguments
  |                                                |
  |                                                expected closure that takes 1 argument

which could potentially be improved for this common case (an N-tuple was expected, but the closure takes N arguments instead). This could extend to other cases where there is a tuple : multiple arguments mismatch.

[estebank]

The original error is now handled, but leaving open to keep track of the following case that still needs to be handled:

 18 |     f(|(x, y)| x + y);
    |     ^ -------- takes a single tuple as an argument
    |     | |
    |     | help: consider changing to: `|x, y|`
    |     |
    |     expected closure that takes 2 arguments