syntax_data: {"ast_node_type":"other","tokens":[{"end":84,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // Otherwise, `expn_id` is a macros 1.0 definition and the call site is in a
context_after:         // macros 2.0 expansion, i.e., a macros 1.0 invocation is in a macros 2.0 definition.