{"ast_node_type":"function","tokens":[{"end":93,"kind":"keyword","start":0,"text":"fn"}]}
    fn into_diagnostic(self, expr: ExprId, expr_ty: Ty, cast_ty: Ty) -> InferenceDiagnostic {
impl CastError {
        InferenceDiagnostic::InvalidCast { expr, error: self, expr_ty, cast_ty }