syntax_data: {"ast_node_type":"variable","tokens":[{"end":21,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let mut err =
context_before:     fn report_op(&mut self, fun_ty: Ty<'_>, args: &[ExprId], fn_span: Span, expr: &Expr<'_>) {
context_after:             self.tcx.dcx().struct_span_err(fn_span, "`become` does not support operators");