Strange formatted comments behind if let in a new line

[CYBAI]

$ rustfmt --version
rustfmt 1.4.11-nightly (1838235 2019-12-03)

---

I'm not sure if this is duplicate with #3937 so filed this one.

Code:

fn main() {
    let o_num = Some(123);
    
    let x = if let Some(n) =
        // this is a test comment
        // to see if rustfmt will break
        // after using the lateset version
        o_num {
            n * 2
        } else {
            0
        };
    
    println!("Number: {}", x);
}

Actual Formatted:

fn main() {
    let o_num = Some(123);

    let x = if let Some(n) =
        // this is a test comment
    // to see if rustfmt will break
    // after using the lateset version
        o_num
    {
        n * 2
    } else {
        0
    };

    println!("Number: {}", x);
}

Personal Expected Formatted:

fn main() {
    let o_num = Some(123);

    let x = if let Some(n) =
        // this is a test comment
        // to see if rustfmt will break
        // after using the lateset version
        o_num
    {
        n * 2
    } else {
        0
    };

    println!("Number: {}", x);
}

[SimonSapin]

Per servo/servo#25371 it looks like this regressed in 33e3667...1838235

$ rustfmt +nightly-2019-12-05 -V
rustfmt 1.4.9-nightly (33e3667 2019-10-07)
$ rustfmt +nightly-2019-12-25 -V
rustfmt 1.4.11-nightly (1838235 2019-12-03)