syntax_data: {"ast_node_type":"variable","tokens":[{"end":81,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:     let unique_symbols_rev: &mut FxIndexMap<(Namespace, Symbol), Option<DefId>> =
context_before:     // non-unique pairs will have a `None` entry.
context_after:         &mut FxIndexMap::default();