syntax_data: {"ast_node_type":"variable","tokens":[{"end":49,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let mut err = self.dcx().create_err(err);
context_before:     pub fn create_feature_err<'a>(&'a self, err: impl Diagnostic<'a>, feature: Symbol) -> Diag<'a> {
context_after:         if err.code.is_none() {