{"ast_node_type":"function","tokens":[{"end":66,"kind":"keyword","start":0,"text":"fn"}]}
    fn create_coercion_graph(&self) -> VecGraph<ty::TyVid, true> {
    /// an edge `?A -> ?B` indicates that the variable `?A` is coerced to `?B`.
        let pending_obligations = self.fulfillment_cx.borrow_mut().pending_obligations();