syntax_data: {"ast_node_type":"other","tokens":[{"end":67,"kind":"keyword","start":0,"text":"for"}]}
source_snippet:     for ((_, symbol), opt_def_id) in unique_symbols_rev.drain(..) {
context_before:     let mut map: DefIdMap<Symbol> = Default::default();
context_after:         use std::collections::hash_map::Entry::{Occupied, Vacant};