syntax_data: {"ast_node_type":"other","tokens":[{"end":99,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// Collisions are possible and processed in `maybe_use_metavar_location` on best effort basis.
context_before:     /// Maps a macro argument token into use of the corresponding metavariable in the macro body.
context_after:     metavar_spans: MetavarSpansMap,