syntax_data: {"ast_node_type":"other","tokens":[{"end":49,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:     // non-unique pairs will have a `None` entry.
context_before:     // Once constructed, unique namespace+symbol pairs will have a `Some(_)` entry, while
context_after:     let unique_symbols_rev: &mut FxIndexMap<(Namespace, Symbol), Option<DefId>> =