Function structural_diff 

pub fn structural_diff(
    old_source: &str,
    new_source: &str,
    lang: Language,
) -> Vec<StructuralChange>

Compare two versions of source code and return structural changes.

Returns an empty list if either side has no grammar or the parse deadline fires. Prefer [try_structural_diff] when timeout must fail closed instead of looking like “no structural changes”.