syntax_data: {"ast_node_type":"other","tokens":[{"end":95,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:     // Flatten is bad perf-vise, we could probably implement a special case here that is better
context_before: fn maybe_iter<I: Iterator>(i: Option<I>) -> impl Iterator<Item = I::Item> {
context_after:     i.into_iter().flatten()