syntax_data: {"ast_node_type":"function","tokens":[{"end":72,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
context_before: impl<'tcx> Subdiagnostic for AdtDefinedHere<'tcx> {
context_after:         diag.arg("ty", self.ty);