zig fmt idempotency: fn param doc comment not properly formatted in one go

Zig Version

0.11.0-dev.1586+2d017f379

Steps to Reproduce and Observed Behavior

$ cat b.zig
pub fn x(a: u32,
    /// aaa
b: u32, y: u32) void {
    _ = a;
    _ = b;
    _ = y;
}
$ zig fmt b.zig
b.zig
$ zig fmt b.zig
b.zig:1:18: error: same line documentation comment
pub fn x(a: u32, /// aaa
                 ^~~~~~~

Expected Behavior

If there should ultimately be any error, it should happen in the first zig fmt, not in any after that if I haven't changed the file.