syntax_data: {"ast_node_type":"other","tokens":[{"end":40,"kind":"keyword","start":0,"text":".map(|alt|"}]}
source_snippet:                 .map(|alt| alt.prune(f))
context_before:                 .into_iter()
context_after:                 .fold(Tree::uninhabited(), |alts, alt| alts.or(alt)),