syntax_data: {"ast_node_type":"impl","tokens":[{"end":69,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // but whether it or any field has a Drop impl (`needs_drop`)
context_before:         // FIXME: this should not be checking for `Drop` impls,
context_after:         // as fields' Drop impls may make this observable, too.