syntax_data: {"ast_node_type":"other","tokens":[{"end":54,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// would have collisions without a disambiguator.
context_before:     /// This is used by `update_disambiguator` to keep track of which `ExpnData`s
context_after:     /// The keys of this map are always computed with `ExpnData.disambiguator`