-use rustc::hir;
-use rustc::hir::def_id::DefId;
use rustc::infer::at::ToTrace;
use rustc::infer::canonical::{Canonical, QueryResponse};
use rustc::infer::InferCtxt;
use rustc::ty::{
FnSig, Lift, ParamEnv, ParamEnvAnd, PolyFnSig, Predicate, Ty, TyCtxt, TypeFoldable, Variance,
};
+use rustc_hir as hir;
+use rustc_hir::def_id::DefId;
use rustc_span::DUMMY_SP;
use std::fmt;