syntax_data: {"ast_node_type":"other","tokens":[{"end":96,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // FIXME: If this span comes from a `derive` macro but it points at code the user wrote,
context_before:         !self.from_expansion()
context_after:         // the callsite span and the span will be pointing at different places. It also means that