syntax_data: {"ast_node_type":"function","tokens":[{"end":78,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
context_before:     #[track_caller]
context_after:         Diag::new(dcx, level, self.explain).with_span(self.span).with_code(E0658)