syntax_data: {"ast_node_type":"variable","tokens":[{"end":66,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:     let mut diag = tcx.dcx().create_err(NegativePositiveConflict {
context_before: ) -> ErrorGuaranteed {
context_after:         impl_span: tcx.def_span(local_impl_def_id),