syntax_data: {"ast_node_type":"function","tokens":[{"end":100,"kind":"keyword","start":0,"text":"pub"}]}
source_snippet:     pub fn create_feature_err<'a>(&'a self, err: impl Diagnostic<'a>, feature: Symbol) -> Diag<'a> {
context_before:     #[track_caller]
context_after:         let mut err = self.dcx().create_err(err);