Unhelpful error when array elements aren't separated by commas

[adamchalmers]

Given the following code (playground):

fn main() {
    let all_tests = [
        ("C200B40A82", 3)
        ("C200B40A82", 3)
    ];
}

The current output is:

error[E0618]: expected function, found `(&'static str, {integer})`
 --> src/main.rs:3:9
  |
3 |           ("C200B40A82", 3)
  |  _________-^^^^^^^^^^^^^^^^
4 | |         ("C200B40A82", 3)
  | |_________________________- call expression requires function

For more information about this error, try `rustc --explain E0618`.
error: could not compile `playground` due to previous error

Ideally the output should look like:

Items in arrays, vec![] or tuples need to be separated by commas

and the compiler would preview the fix, by adding the commas in green.

[hkmatsumoto]

@rustbot claim

[hkmatsumoto]

This week I'm busier than I thought ;)
@rustbot release-assignment

[BGR360]

@rustbot label +A-parser

[terrarier2111]

@rustbot claim