Formatting an `impl` with a trailing comment is impossible

**Describe the bug**

If there is a comment between the end of the last function and the end of an impl, the impl cannot be formatted.

**To Reproduce**
Steps to reproduce the behavior:
1. Format
```
struct MyStruct{}

impl MyStruct {
fn my_function() -> u32 { u32:3 }
// Format
}
```
2. See error

```
Formatting failed: Error: INTERNAL: Formatting was skipped because a comment at (filename) would be deleted by the formatter: // Format
This is probably due to a bug (which may not have been reported yet). To complete formatting, try moving the comment to a different line.
```

**Expected behavior**
It formats it