rustfmt fails to format braceless closure that starts with a comment

This code from where I was doing exercism rust exercises

pub fn brackets_are_balanced(string: &str) -> bool {
    let mut ret = None;
    let mut stack = Vec::new();
    string.chars().for_each(|c|
        // remember opened brackets
        if ['[','{','('].contains(&c) {
            stack.push(c);
    } else if 
        // if we encounter closing brackets
            [']','}',')'].contains(&c) {
                let pair = (stack.pop(), c) ;
          
                match pair {
                    // make sure we have a corresponding bracket at the stack 
                    (Some('['), ']')|   (Some('{'), '}') |       (Some('('), ')')  =>  {},
                    // if this is not the case, return false
                _ => {ret = Some(false);},
                }
        }
   
   
    );
    if let Some(ret) = ret {
        ret
    } else {
        stack.is_empty()
    }
}

rustfmt really did not like that code:

 --> /home/matthias/exercism/rust/matching-brackets/src/lib.rs:8:8:14
  |
8 |     } else if 
  |              ^
  |

error[internal]: left behind trailing whitespace
  --> /home/matthias/exercism/rust/matching-brackets/src/lib.rs:12:12:1
   |
12 |           
   | ^^^^^^^^^^
   |

error[internal]: left behind trailing whitespace
  --> /home/matthias/exercism/rust/matching-brackets/src/lib.rs:20:20:1
   |
20 |    
   | ^^^
   |

error[internal]: left behind trailing whitespace
  --> /home/matthias/exercism/rust/matching-brackets/src/lib.rs:21:21:1
   |
21 |    
   | ^^^
   |

warning: rustfmt has failed to format. See previous 4 errors.

rustfmt 1.4.37-nightly (f58631b 2021-05-28)

Start by reproducing the supplied braceless-closure example with the reported rustfmt version and inspect how comments and trailing whitespace are handled around the closure conditions. Done means rustfmt formats the example without internal errors or leftover trailing whitespace; the issue does not name a source file or test to update.