syntax_data: {"ast_node_type":"import","tokens":[{"end":67,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// first and then resolved later), so we use an `Option` here.
context_before:     /// between creation of an expansion ID and obtaining its data (e.g. macros are collected
context_after:     local_expn_data: IndexVec<LocalExpnId, Option<ExpnData>>,