{"ast_node_type":"variable","tokens":[{"end":79,"kind":"keyword","start":0,"text":"if"}]}
        if let &ty::Infer(ty::TyVar(generalized_vid)) = generalized_ty.kind() {
        // Constrain `b_vid` to the generalized type `generalized_ty`.
            self.inner.borrow_mut().type_variables().equate(target_vid, generalized_vid);