Fixed semicolon getting moved into comment (fixes rust-lang#4646)

Author: vallentin

src/formatting/items.rs

@@ -434,6 +434,10 @@ impl<'a> FmtVisitor<'a> {
             FnBraceStyle::None,
         )?;
 
+        if last_line_contains_single_line_comment(&result) {
+            result.push('\n');
+        }
+
         // Re-attach semicolon
         result.push(';');