rustfmt inserts two closing brackets when missing closing paren

[mikecargal]

Describe the bug

The accidental omission of a closing paren, as in:
println!("answer: {}", a_func();
causes Rustfmt to insert two closing brackets, obscuring the actual error.

To Reproduce

create main.rs

fn main() {
    if true {
        println!("answer: {}", a_func();
    } else {
        println!("don't think so.");
    }
}

fn a_func() -> i32 {
    42
}

run rustfmt (in my case implicitly in VS Code with the format on save capability). Result is:

fn main() {
    if true {
        println!("answer: {}", a_func();
        }
        }
    } else {
        println!("don't think so.");
    }
}

fn a_func() -> i32 {
    42
}

This results in the following errors (obscuring the actual error):

error: unexpected closing delimiter: `}`
 --> src/main.rs:6:5
  |
1 | fn main() {
  |           - this opening brace...
...
5 |         }
  |         - ...matches this closing brace
6 |     } else {
  |     ^ unexpected closing delimiter

error: mismatched closing delimiter: `}`
 --> src/main.rs:4:9
  |
3 |         println!("answer: {}", a_func();
  |                 - unclosed delimiter
4 |         }
  |         ^ mismatched closing delimiter

error: aborting due to 2 previous errors

error: could not compile `fmt_bug`.

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

Expected behavior

Don't insert closing brackets, so the missing closing paren is reported as the actual error.

Meta

• rustfmt version: rustfmt 1.4.20-stable (48f6c32 2020-08-09)
• From where did you install rustfmt?: rustup
• How do you run rustfmt: VS Code Rust plugin