Comment affects whether `return expr` fmts to `return expr;`

adding a comment here caused an unrelated diff in a semicolon formatting:

                     ArgValue::Lit(other) => {
+                        // FIXME: add a ui test for this
                         return Err(syn::Error::new(
                             other.span(),
                             "expected boolean, path, or string literal",
-                        ))
+                        ));
                     }

at least it doesn't depend much on the exact position of the comment, just whether it sees one?

             e => {
                 return Err(syn::Error::new(
+                    // FIXME: add a UI test for this
                     input.span(),
                     format!("Invalid option `{e}` inside `{ident} {input}`"),
-                ))
+                ));
            }

This sort of thing should not matter.

Start by reproducing the formatting change with the two Rust snippets shown in the issue, comparing versions with and without comments. Trace the formatter behavior responsible for semicolon insertion and add a regression test showing that comments do not change whether return expr is formatted with a semicolon.