diff --git a/src/librustc/hir/check_attr.rs b/src/librustc/hir/check_attr.rs
index d525f364593..75f78104b48 100644
--- a/src/librustc/hir/check_attr.rs
+++ b/src/librustc/hir/check_attr.rs
@@ -5,6 +5,7 @@
 //! item.
 
 use crate::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use crate::hir::map::Map;
 use crate::lint::builtin::UNUSED_ATTRIBUTES;
 use crate::ty::query::Providers;
 use crate::ty::TyCtxt;
@@ -519,7 +520,9 @@ impl CheckAttrVisitor<'tcx> {
 }
 
 impl Visitor<'tcx> for CheckAttrVisitor<'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, Self::Map> {
         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
     }
 
diff --git a/src/librustc/hir/intravisit.rs b/src/librustc/hir/intravisit.rs
index 9d6acbda62e..13b5be08d8a 100644
--- a/src/librustc/hir/intravisit.rs
+++ b/src/librustc/hir/intravisit.rs
@@ -31,8 +31,6 @@
 //! This order consistency is required in a few places in rustc, for
 //! example generator inference, and possibly also HIR borrowck.
 
-use crate::hir::map::Map;
-
 use rustc_hir::itemlikevisit::{ItemLikeVisitor, ParItemLikeVisitor};
 use rustc_hir::*;
 use rustc_span::Span;
@@ -42,10 +40,7 @@ pub struct DeepVisitor<'v, V> {
     visitor: &'v mut V,
 }
 
-impl<'v, 'hir, V> DeepVisitor<'v, V>
-where
-    V: Visitor<'hir> + 'v,
-{
+impl<'v, V> DeepVisitor<'v, V> {
     pub fn new(base: &'v mut V) -> Self {
         DeepVisitor { visitor: base }
     }
@@ -122,6 +117,14 @@ impl<'a> FnKind<'a> {
     }
 }
 
+/// An abstract representation of the HIR `rustc::hir::map::Map`.
+pub trait Map<'hir> {
+    fn body(&self, id: BodyId) -> &'hir Body<'hir>;
+    fn item(&self, id: HirId) -> &'hir Item<'hir>;
+    fn trait_item(&self, id: TraitItemId) -> &'hir TraitItem<'hir>;
+    fn impl_item(&self, id: ImplItemId) -> &'hir ImplItem<'hir>;
+}
+
 /// Specifies what nested things a visitor wants to visit. The most
 /// common choice is `OnlyBodies`, which will cause the visitor to
 /// visit fn bodies for fns that it encounters, but skip over nested
@@ -129,7 +132,7 @@ impl<'a> FnKind<'a> {
 ///
 /// See the comments on `ItemLikeVisitor` for more details on the overall
 /// visit strategy.
-pub enum NestedVisitorMap<'this, 'tcx> {
+pub enum NestedVisitorMap<'this, M> {
     /// Do not visit any nested things. When you add a new
     /// "non-nested" thing, you will want to audit such uses to see if
     /// they remain valid.
@@ -146,20 +149,20 @@ pub enum NestedVisitorMap<'this, 'tcx> {
     /// to use `visit_all_item_likes()` as an outer loop,
     /// and to have the visitor that visits the contents of each item
     /// using this setting.
-    OnlyBodies(&'this Map<'tcx>),
+    OnlyBodies(&'this M),
 
     /// Visits all nested things, including item-likes.
     ///
     /// **This is an unusual choice.** It is used when you want to
     /// process everything within their lexical context. Typically you
     /// kick off the visit by doing `walk_krate()`.
-    All(&'this Map<'tcx>),
+    All(&'this M),
 }
 
-impl<'this, 'tcx> NestedVisitorMap<'this, 'tcx> {
+impl<'this, M> NestedVisitorMap<'this, M> {
     /// Returns the map to use for an "intra item-like" thing (if any).
     /// E.g., function body.
-    fn intra(self) -> Option<&'this Map<'tcx>> {
+    fn intra(self) -> Option<&'this M> {
         match self {
             NestedVisitorMap::None => None,
             NestedVisitorMap::OnlyBodies(map) => Some(map),
@@ -169,7 +172,7 @@ impl<'this, 'tcx> NestedVisitorMap<'this, 'tcx> {
 
     /// Returns the map to use for an "item-like" thing (if any).
     /// E.g., item, impl-item.
-    fn inter(self) -> Option<&'this Map<'tcx>> {
+    fn inter(self) -> Option<&'this M> {
         match self {
             NestedVisitorMap::None => None,
             NestedVisitorMap::OnlyBodies(_) => None,
@@ -195,6 +198,8 @@ impl<'this, 'tcx> NestedVisitorMap<'this, 'tcx> {
 /// to monitor future changes to `Visitor` in case a new method with a
 /// new default implementation gets introduced.)
 pub trait Visitor<'v>: Sized {
+    type Map: Map<'v>;
+
     ///////////////////////////////////////////////////////////////////////////
     // Nested items.
 
@@ -214,7 +219,7 @@ pub trait Visitor<'v>: Sized {
     /// `panic!()`. This way, if a new `visit_nested_XXX` variant is
     /// added in the future, we will see the panic in your code and
     /// fix it appropriately.
-    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, 'v>;
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map>;
 
     /// Invoked when a nested item is encountered. By default does
     /// nothing unless you override `nested_visit_map` to return other than
@@ -496,21 +501,16 @@ pub fn walk_lifetime<'v, V: Visitor<'v>>(visitor: &mut V, lifetime: &'v Lifetime
     }
 }
 
-pub fn walk_poly_trait_ref<'v, V>(
+pub fn walk_poly_trait_ref<'v, V: Visitor<'v>>(
     visitor: &mut V,
     trait_ref: &'v PolyTraitRef<'v>,
     _modifier: TraitBoundModifier,
-) where
-    V: Visitor<'v>,
-{
+) {
     walk_list!(visitor, visit_generic_param, trait_ref.bound_generic_params);
     visitor.visit_trait_ref(&trait_ref.trait_ref);
 }
 
-pub fn walk_trait_ref<'v, V>(visitor: &mut V, trait_ref: &'v TraitRef<'v>)
-where
-    V: Visitor<'v>,
-{
+pub fn walk_trait_ref<'v, V: Visitor<'v>>(visitor: &mut V, trait_ref: &'v TraitRef<'v>) {
     visitor.visit_id(trait_ref.hir_ref_id);
     visitor.visit_path(&trait_ref.path, trait_ref.hir_ref_id)
 }
diff --git a/src/librustc/hir/map/collector.rs b/src/librustc/hir/map/collector.rs
index 7dca5451a30..6aa1b6da368 100644
--- a/src/librustc/hir/map/collector.rs
+++ b/src/librustc/hir/map/collector.rs
@@ -1,7 +1,7 @@
 use crate::dep_graph::{DepGraph, DepKind, DepNode, DepNodeIndex};
 use crate::hir::intravisit::{self, NestedVisitorMap, Visitor};
 use crate::hir::map::definitions::{self, DefPathHash};
-use crate::hir::map::{Entry, HirEntryMap};
+use crate::hir::map::{Entry, HirEntryMap, Map};
 use crate::ich::StableHashingContext;
 use crate::middle::cstore::CrateStore;
 use rustc_data_structures::fingerprint::Fingerprint;
@@ -336,11 +336,13 @@ impl<'a, 'hir> NodeCollector<'a, 'hir> {
 }
 
 impl<'a, 'hir> Visitor<'hir> for NodeCollector<'a, 'hir> {
+    type Map = Map<'hir>;
+
     /// Because we want to track parent items and so forth, enable
     /// deep walking so that we walk nested items in the context of
     /// their outer items.
 
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'hir> {
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, Self::Map> {
         panic!("`visit_nested_xxx` must be manually implemented in this visitor");
     }
 
diff --git a/src/librustc/hir/map/hir_id_validator.rs b/src/librustc/hir/map/hir_id_validator.rs
index 63299707592..2499acae5e6 100644
--- a/src/librustc/hir/map/hir_id_validator.rs
+++ b/src/librustc/hir/map/hir_id_validator.rs
@@ -133,7 +133,9 @@ impl<'a, 'hir> HirIdValidator<'a, 'hir> {
 }
 
 impl<'a, 'hir> intravisit::Visitor<'hir> for HirIdValidator<'a, 'hir> {
-    fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'hir> {
+    type Map = Map<'hir>;
+
+    fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, Self::Map> {
         intravisit::NestedVisitorMap::OnlyBodies(self.hir_map)
     }
 
diff --git a/src/librustc/hir/map/mod.rs b/src/librustc/hir/map/mod.rs
index 69978efd81d..f7b654eae1e 100644
--- a/src/librustc/hir/map/mod.rs
+++ b/src/librustc/hir/map/mod.rs
@@ -1093,6 +1093,24 @@ impl<'hir> Map<'hir> {
     }
 }
 
+impl<'hir> intravisit::Map<'hir> for Map<'hir> {
+    fn body(&self, id: BodyId) -> &'hir Body<'hir> {
+        self.body(id)
+    }
+
+    fn item(&self, id: HirId) -> &'hir Item<'hir> {
+        self.item(id)
+    }
+
+    fn trait_item(&self, id: TraitItemId) -> &'hir TraitItem<'hir> {
+        self.trait_item(id)
+    }
+
+    fn impl_item(&self, id: ImplItemId) -> &'hir ImplItem<'hir> {
+        self.impl_item(id)
+    }
+}
+
 pub struct NodesMatchingSuffix<'a> {
     map: &'a Map<'a>,
     item_name: &'a String,
diff --git a/src/librustc/hir/upvars.rs b/src/librustc/hir/upvars.rs
index df02a79ef4c..b61a54a643f 100644
--- a/src/librustc/hir/upvars.rs
+++ b/src/librustc/hir/upvars.rs
@@ -1,6 +1,7 @@
 //! Upvar (closure capture) collection from cross-body HIR uses of `Res::Local`s.
 
 use crate::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use crate::hir::map::Map;
 use crate::ty::query::Providers;
 use crate::ty::TyCtxt;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
@@ -43,7 +44,9 @@ struct LocalCollector {
 }
 
 impl Visitor<'tcx> for LocalCollector {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, Self::Map> {
         NestedVisitorMap::None
     }
 
@@ -70,7 +73,9 @@ impl CaptureCollector<'_, '_> {
 }
 
 impl Visitor<'tcx> for CaptureCollector<'a, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, Self::Map> {
         NestedVisitorMap::None
     }
 
diff --git a/src/librustc/infer/error_reporting/need_type_info.rs b/src/librustc/infer/error_reporting/need_type_info.rs
index 4dedf0a23e8..9c7bf261d9b 100644
--- a/src/librustc/infer/error_reporting/need_type_info.rs
+++ b/src/librustc/infer/error_reporting/need_type_info.rs
@@ -66,7 +66,9 @@ impl<'a, 'tcx> FindLocalByTypeVisitor<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for FindLocalByTypeVisitor<'a, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, Self::Map> {
         NestedVisitorMap::OnlyBodies(&self.hir_map)
     }
 
diff --git a/src/librustc/infer/error_reporting/nice_region_error/find_anon_type.rs b/src/librustc/infer/error_reporting/nice_region_error/find_anon_type.rs
index 6edf8f1e787..6ec956f15dd 100644
--- a/src/librustc/infer/error_reporting/nice_region_error/find_anon_type.rs
+++ b/src/librustc/infer/error_reporting/nice_region_error/find_anon_type.rs
@@ -1,4 +1,5 @@
 use crate::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use crate::hir::map::Map;
 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use crate::middle::resolve_lifetime as rl;
 use crate::ty::{self, Region, TyCtxt};
@@ -90,7 +91,9 @@ struct FindNestedTypeVisitor<'tcx> {
 }
 
 impl Visitor<'tcx> for FindNestedTypeVisitor<'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, Self::Map> {
         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
     }
 
@@ -207,7 +210,9 @@ struct TyPathVisitor<'tcx> {
 }
 
 impl Visitor<'tcx> for TyPathVisitor<'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, Map<'tcx>> {
         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
     }
 
diff --git a/src/librustc/middle/weak_lang_items.rs b/src/librustc/middle/weak_lang_items.rs
index e9e35b7617c..71abbd8bcb1 100644
--- a/src/librustc/middle/weak_lang_items.rs
+++ b/src/librustc/middle/weak_lang_items.rs
@@ -5,6 +5,7 @@ use crate::session::config;
 
 use crate::hir::intravisit;
 use crate::hir::intravisit::{NestedVisitorMap, Visitor};
+use crate::hir::map::Map;
 use crate::ty::TyCtxt;
 use errors::struct_span_err;
 use rustc_data_structures::fx::FxHashSet;
@@ -136,7 +137,9 @@ impl<'a, 'tcx> Context<'a, 'tcx> {
 }
 
 impl<'a, 'tcx, 'v> Visitor<'v> for Context<'a, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
+    type Map = Map<'v>;
+
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, Map<'v>> {
         NestedVisitorMap::None
     }
 
diff --git a/src/librustc_ast_lowering/lib.rs b/src/librustc_ast_lowering/lib.rs
index 8b79d9b4f47..6c4d7ec3a8a 100644
--- a/src/librustc_ast_lowering/lib.rs
+++ b/src/librustc_ast_lowering/lib.rs
@@ -37,7 +37,8 @@
 use rustc::arena::Arena;
 use rustc::dep_graph::DepGraph;
 use rustc::hir::intravisit;
-use rustc::hir::map::{DefKey, DefPathData, Definitions};
+use rustc::hir::map::definitions::{DefKey, DefPathData, Definitions};
+use rustc::hir::map::Map;
 use rustc::lint;
 use rustc::lint::builtin::{self, ELIDED_LIFETIMES_IN_PATHS};
 use rustc::middle::cstore::CrateStore;
@@ -1484,7 +1485,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }
 
         impl<'r, 'a, 'v, 'hir> intravisit::Visitor<'v> for ImplTraitLifetimeCollector<'r, 'a, 'hir> {
-            fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'v> {
+            type Map = Map<'v>;
+
+            fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
                 intravisit::NestedVisitorMap::None
             }
 
diff --git a/src/librustc_incremental/assert_dep_graph.rs b/src/librustc_incremental/assert_dep_graph.rs
index 64547845e74..e59a52923d9 100644
--- a/src/librustc_incremental/assert_dep_graph.rs
+++ b/src/librustc_incremental/assert_dep_graph.rs
@@ -37,6 +37,7 @@ use graphviz as dot;
 use rustc::dep_graph::debug::{DepNodeFilter, EdgeFilter};
 use rustc::dep_graph::{DepGraphQuery, DepKind, DepNode};
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::ty::TyCtxt;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::graph::implementation::{Direction, NodeIndex, INCOMING, OUTGOING};
@@ -159,7 +160,9 @@ impl IfThisChanged<'tcx> {
 }
 
 impl Visitor<'tcx> for IfThisChanged<'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, Self::Map> {
         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
     }
 
diff --git a/src/librustc_incremental/persist/dirty_clean.rs b/src/librustc_incremental/persist/dirty_clean.rs
index 40dd4c88a02..a7f915b833d 100644
--- a/src/librustc_incremental/persist/dirty_clean.rs
+++ b/src/librustc_incremental/persist/dirty_clean.rs
@@ -15,6 +15,7 @@
 
 use rustc::dep_graph::{label_strs, DepNode};
 use rustc::hir::intravisit;
+use rustc::hir::map::Map;
 use rustc::ty::TyCtxt;
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::FxHashSet;
@@ -547,7 +548,9 @@ impl FindAllAttrs<'tcx> {
 }
 
 impl intravisit::Visitor<'tcx> for FindAllAttrs<'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, Self::Map> {
         intravisit::NestedVisitorMap::All(&self.tcx.hir())
     }
 
diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index c2e20d5cf75..213ca308d56 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -25,6 +25,7 @@ use std::fmt::Write;
 
 use lint::{EarlyContext, EarlyLintPass, LateLintPass, LintPass};
 use lint::{LateContext, LintArray, LintContext};
+use rustc::hir::map::Map;
 use rustc::lint;
 use rustc::lint::FutureIncompatibleInfo;
 use rustc::traits::misc::can_type_implement_copy;
@@ -1093,7 +1094,9 @@ impl TypeAliasBounds {
             err: &'a mut DiagnosticBuilder<'db>,
         }
         impl<'a, 'db, 'v> Visitor<'v> for WalkAssocTypes<'a, 'db> {
-            fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'v> {
+            type Map = Map<'v>;
+
+            fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
                 intravisit::NestedVisitorMap::None
             }
 
diff --git a/src/librustc_lint/late.rs b/src/librustc_lint/late.rs
index 2e0a201fa98..da27e9225d7 100644
--- a/src/librustc_lint/late.rs
+++ b/src/librustc_lint/late.rs
@@ -16,6 +16,7 @@
 
 use rustc::hir::intravisit as hir_visit;
 use rustc::hir::intravisit::Visitor;
+use rustc::hir::map::Map;
 use rustc::lint::LateContext;
 use rustc::lint::LintPass;
 use rustc::lint::{LateLintPass, LateLintPassObject};
@@ -86,10 +87,12 @@ impl<'a, 'tcx, T: LateLintPass<'a, 'tcx>> LateContextAndPass<'a, 'tcx, T> {
 impl<'a, 'tcx, T: LateLintPass<'a, 'tcx>> hir_visit::Visitor<'tcx>
     for LateContextAndPass<'a, 'tcx, T>
 {
+    type Map = Map<'tcx>;
+
     /// Because lints are scoped lexically, we want to walk nested
     /// items in the context of the outer item, so enable
     /// deep-walking.
-    fn nested_visit_map<'this>(&'this mut self) -> hir_visit::NestedVisitorMap<'this, 'tcx> {
+    fn nested_visit_map<'this>(&'this mut self) -> hir_visit::NestedVisitorMap<'this, Self::Map> {
         hir_visit::NestedVisitorMap::All(&self.context.tcx.hir())
     }
 
diff --git a/src/librustc_lint/levels.rs b/src/librustc_lint/levels.rs
index e060d6b551c..f6f1ae2a08a 100644
--- a/src/librustc_lint/levels.rs
+++ b/src/librustc_lint/levels.rs
@@ -1,4 +1,5 @@
 use rustc::hir::intravisit;
+use rustc::hir::map::Map;
 use rustc::lint::{LintLevelMap, LintLevelSets, LintLevelsBuilder, LintStore};
 use rustc::ty::query::Providers;
 use rustc::ty::TyCtxt;
@@ -50,7 +51,9 @@ impl LintLevelMapBuilder<'_, '_> {
 }
 
 impl<'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'_, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, Self::Map> {
         intravisit::NestedVisitorMap::All(&self.tcx.hir())
     }
 
diff --git a/src/librustc_metadata/rmeta/encoder.rs b/src/librustc_metadata/rmeta/encoder.rs
index 92bfc51d9d5..390472940c7 100644
--- a/src/librustc_metadata/rmeta/encoder.rs
+++ b/src/librustc_metadata/rmeta/encoder.rs
@@ -2,6 +2,7 @@ use crate::rmeta::table::FixedSizeEncoding;
 use crate::rmeta::*;
 
 use rustc::hir::map::definitions::DefPathTable;
+use rustc::hir::map::Map;
 use rustc::middle::cstore::{EncodedMetadata, ForeignModule, LinkagePreference, NativeLibrary};
 use rustc::middle::dependency_format::Linkage;
 use rustc::middle::exported_symbols::{metadata_symbol_name, ExportedSymbol, SymbolExportLevel};
@@ -1520,7 +1521,9 @@ impl EncodeContext<'tcx> {
 
 // FIXME(eddyb) make metadata encoding walk over all definitions, instead of HIR.
 impl Visitor<'tcx> for EncodeContext<'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
     }
     fn visit_expr(&mut self, ex: &'tcx hir::Expr<'tcx>) {
diff --git a/src/librustc_mir/hair/pattern/check_match.rs b/src/librustc_mir/hair/pattern/check_match.rs
index 07bb87f7b54..ab76f010a0f 100644
--- a/src/librustc_mir/hair/pattern/check_match.rs
+++ b/src/librustc_mir/hair/pattern/check_match.rs
@@ -5,6 +5,7 @@ use super::_match::{expand_pattern, is_useful, MatchCheckCtxt, Matrix, PatStack}
 use super::{PatCtxt, PatKind, PatternError};
 
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::lint;
 use rustc::session::Session;
 use rustc::ty::subst::{InternalSubsts, SubstsRef};
@@ -49,7 +50,9 @@ struct MatchVisitor<'a, 'tcx> {
 }
 
 impl<'tcx> Visitor<'tcx> for MatchVisitor<'_, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::None
     }
 
@@ -730,7 +733,9 @@ fn check_legality_of_bindings_in_at_patterns(cx: &MatchVisitor<'_, '_>, pat: &Pa
     }
 
     impl<'v> Visitor<'v> for AtBindingPatternVisitor<'_, '_, '_> {
-        fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
+        type Map = Map<'v>;
+
+        fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
             NestedVisitorMap::None
         }
 
diff --git a/src/librustc_mir/transform/check_unsafety.rs b/src/librustc_mir/transform/check_unsafety.rs
index 5cf5c54dd48..830609f7911 100644
--- a/src/librustc_mir/transform/check_unsafety.rs
+++ b/src/librustc_mir/transform/check_unsafety.rs
@@ -1,4 +1,5 @@
 use rustc::hir::intravisit;
+use rustc::hir::map::Map;
 use rustc::lint::builtin::{SAFE_PACKED_BORROWS, UNUSED_UNSAFE};
 use rustc::mir::visit::{MutatingUseContext, PlaceContext, Visitor};
 use rustc::mir::*;
@@ -475,7 +476,9 @@ struct UnusedUnsafeVisitor<'a> {
 }
 
 impl<'a, 'tcx> intravisit::Visitor<'tcx> for UnusedUnsafeVisitor<'a> {
-    fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, Self::Map> {
         intravisit::NestedVisitorMap::None
     }
 
diff --git a/src/librustc_mir/transform/mod.rs b/src/librustc_mir/transform/mod.rs
index 82c31a09ce3..50abf919f9d 100644
--- a/src/librustc_mir/transform/mod.rs
+++ b/src/librustc_mir/transform/mod.rs
@@ -1,5 +1,6 @@
 use crate::{build, shim};
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::mir::{BodyAndCache, ConstQualifs, MirPhase, Promoted};
 use rustc::ty::query::Providers;
 use rustc::ty::steal::Steal;
@@ -85,7 +86,8 @@ fn mir_keys(tcx: TyCtxt<'_>, krate: CrateNum) -> &DefIdSet {
             }
             intravisit::walk_struct_def(self, v)
         }
-        fn nested_visit_map<'b>(&'b mut self) -> NestedVisitorMap<'b, 'tcx> {
+        type Map = Map<'tcx>;
+        fn nested_visit_map<'b>(&'b mut self) -> NestedVisitorMap<'b, Self::Map> {
             NestedVisitorMap::None
         }
     }
diff --git a/src/librustc_passes/check_const.rs b/src/librustc_passes/check_const.rs
index f6a9d1cace1..072a51391c8 100644
--- a/src/librustc_passes/check_const.rs
+++ b/src/librustc_passes/check_const.rs
@@ -200,7 +200,9 @@ impl<'tcx> CheckConstVisitor<'tcx> {
 }
 
 impl<'tcx> Visitor<'tcx> for CheckConstVisitor<'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
     }
 
diff --git a/src/librustc_passes/dead.rs b/src/librustc_passes/dead.rs
index 0c435a16663..5441a8bf717 100644
--- a/src/librustc_passes/dead.rs
+++ b/src/librustc_passes/dead.rs
@@ -3,6 +3,7 @@
 // from live codes are live, and everything else is dead.
 
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::lint;
 use rustc::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc::middle::privacy;
@@ -210,7 +211,9 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for MarkSymbolVisitor<'a, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::None
     }
 
@@ -563,11 +566,13 @@ impl DeadVisitor<'tcx> {
 }
 
 impl Visitor<'tcx> for DeadVisitor<'tcx> {
+    type Map = Map<'tcx>;
+
     /// Walk nested items in place so that we don't report dead-code
     /// on inner functions when the outer function is already getting
     /// an error. We could do this also by checking the parents, but
     /// this is how the code is setup and it seems harmless enough.
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::All(&self.tcx.hir())
     }
 
diff --git a/src/librustc_passes/hir_stats.rs b/src/librustc_passes/hir_stats.rs
index 3eca602cf86..2c36181ce4b 100644
--- a/src/librustc_passes/hir_stats.rs
+++ b/src/librustc_passes/hir_stats.rs
@@ -3,6 +3,7 @@
 // completely accurate (some things might be counted twice, others missed).
 
 use rustc::hir::intravisit as hir_visit;
+use rustc::hir::map::Map;
 use rustc::util::common::to_readable_str;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir as hir;
@@ -92,7 +93,9 @@ impl<'v> hir_visit::Visitor<'v> for StatCollector<'v> {
         hir_visit::walk_param(self, param)
     }
 
-    fn nested_visit_map<'this>(&'this mut self) -> hir_visit::NestedVisitorMap<'this, 'v> {
+    type Map = Map<'v>;
+
+    fn nested_visit_map(&mut self) -> hir_visit::NestedVisitorMap<'_, Self::Map> {
         panic!("visit_nested_xxx must be manually implemented in this visitor")
     }
 
diff --git a/src/librustc_passes/intrinsicck.rs b/src/librustc_passes/intrinsicck.rs
index 2b9a692117c..68d9ba7f90e 100644
--- a/src/librustc_passes/intrinsicck.rs
+++ b/src/librustc_passes/intrinsicck.rs
@@ -1,12 +1,12 @@
 use errors::struct_span_err;
+use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::ty::layout::{LayoutError, Pointer, SizeSkeleton, VariantIdx};
 use rustc::ty::query::Providers;
 use rustc::ty::{self, Ty, TyCtxt};
+use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::DefId;
-
-use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
-use rustc_hir as hir;
 use rustc_index::vec::Idx;
 use rustc_span::{sym, Span};
 use rustc_target::spec::abi::Abi::RustIntrinsic;
@@ -124,7 +124,9 @@ impl ExprVisitor<'tcx> {
 }
 
 impl Visitor<'tcx> for ItemVisitor<'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::None
     }
 
@@ -139,7 +141,9 @@ impl Visitor<'tcx> for ItemVisitor<'tcx> {
 }
 
 impl Visitor<'tcx> for ExprVisitor<'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::None
     }
 
diff --git a/src/librustc_passes/lib_features.rs b/src/librustc_passes/lib_features.rs
index df56bcff81f..9d5e8080055 100644
--- a/src/librustc_passes/lib_features.rs
+++ b/src/librustc_passes/lib_features.rs
@@ -6,6 +6,7 @@
 
 use errors::struct_span_err;
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::middle::lib_features::LibFeatures;
 use rustc::ty::query::Providers;
 use rustc::ty::TyCtxt;
@@ -113,7 +114,9 @@ impl LibFeatureCollector<'tcx> {
 }
 
 impl Visitor<'tcx> for LibFeatureCollector<'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::All(&self.tcx.hir())
     }
 
diff --git a/src/librustc_passes/liveness.rs b/src/librustc_passes/liveness.rs
index 3ae5e4f72b7..4b5b2148cd9 100644
--- a/src/librustc_passes/liveness.rs
+++ b/src/librustc_passes/liveness.rs
@@ -98,6 +98,7 @@ use self::VarKind::*;
 
 use errors::Applicability;
 use rustc::hir::intravisit::{self, FnKind, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::lint;
 use rustc::ty::query::Providers;
 use rustc::ty::{self, TyCtxt};
@@ -153,7 +154,9 @@ fn live_node_kind_to_string(lnk: LiveNodeKind, tcx: TyCtxt<'_>) -> String {
 }
 
 impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
     }
 
@@ -1348,7 +1351,9 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
 // Checking for error conditions
 
 impl<'a, 'tcx> Visitor<'tcx> for Liveness<'a, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::None
     }
 
diff --git a/src/librustc_passes/loops.rs b/src/librustc_passes/loops.rs
index 262f2382da3..54ea73f1d3d 100644
--- a/src/librustc_passes/loops.rs
+++ b/src/librustc_passes/loops.rs
@@ -44,7 +44,9 @@ pub(crate) fn provide(providers: &mut Providers<'_>) {
 }
 
 impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'hir> {
+    type Map = Map<'hir>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::OnlyBodies(&self.hir_map)
     }
 
diff --git a/src/librustc_passes/reachable.rs b/src/librustc_passes/reachable.rs
index 9b529401049..016cab9d114 100644
--- a/src/librustc_passes/reachable.rs
+++ b/src/librustc_passes/reachable.rs
@@ -7,6 +7,7 @@
 
 use rustc::hir::intravisit;
 use rustc::hir::intravisit::{NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
 use rustc::middle::privacy;
 use rustc::session::config;
@@ -82,7 +83,9 @@ struct ReachableContext<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for ReachableContext<'a, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::None
     }
 
diff --git a/src/librustc_passes/region.rs b/src/librustc_passes/region.rs
index 75c74c4f923..a8a56ee7f09 100644
--- a/src/librustc_passes/region.rs
+++ b/src/librustc_passes/region.rs
@@ -7,6 +7,7 @@
 //! [rustc guide]: https://rust-lang.github.io/rustc-guide/mir/borrowck.html
 
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::middle::region::*;
 use rustc::ty::query::Providers;
 use rustc::ty::TyCtxt;
@@ -695,7 +696,9 @@ impl<'tcx> RegionResolutionVisitor<'tcx> {
 }
 
 impl<'tcx> Visitor<'tcx> for RegionResolutionVisitor<'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::None
     }
 
diff --git a/src/librustc_passes/stability.rs b/src/librustc_passes/stability.rs
index 33c985bd66b..7891fab0aa6 100644
--- a/src/librustc_passes/stability.rs
+++ b/src/librustc_passes/stability.rs
@@ -3,6 +3,7 @@
 
 use errors::struct_span_err;
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::lint;
 use rustc::middle::privacy::AccessLevels;
 use rustc::middle::stability::{DeprecationEntry, Index};
@@ -204,7 +205,9 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
     /// Because stability levels are scoped lexically, we want to walk
     /// nested items in the context of the outer item, so enable
     /// deep-walking.
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::All(&self.tcx.hir())
     }
 
@@ -293,7 +296,9 @@ impl<'a, 'tcx> MissingStabilityAnnotations<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for MissingStabilityAnnotations<'a, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
     }
 
@@ -429,10 +434,12 @@ struct Checker<'tcx> {
 }
 
 impl Visitor<'tcx> for Checker<'tcx> {
+    type Map = Map<'tcx>;
+
     /// Because stability levels are scoped lexically, we want to walk
     /// nested items in the context of the outer item, so enable
     /// deep-walking.
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
     }
 
diff --git a/src/librustc_privacy/lib.rs b/src/librustc_privacy/lib.rs
index 17e56129247..3d0d4070a25 100644
--- a/src/librustc_privacy/lib.rs
+++ b/src/librustc_privacy/lib.rs
@@ -5,6 +5,7 @@
 
 use rustc::bug;
 use rustc::hir::intravisit::{self, DeepVisitor, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::lint;
 use rustc::middle::privacy::{AccessLevel, AccessLevels};
 use rustc::ty::fold::TypeVisitor;
@@ -372,7 +373,9 @@ struct PubRestrictedVisitor<'tcx> {
 }
 
 impl Visitor<'tcx> for PubRestrictedVisitor<'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::All(&self.tcx.hir())
     }
     fn visit_vis(&mut self, vis: &'tcx hir::Visibility<'tcx>) {
@@ -670,9 +673,11 @@ impl EmbargoVisitor<'tcx> {
 }
 
 impl Visitor<'tcx> for EmbargoVisitor<'tcx> {
+    type Map = Map<'tcx>;
+
     /// We want to visit items in the context of their containing
     /// module and so forth, so supply a crate for doing a deep walk.
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::All(&self.tcx.hir())
     }
 
@@ -1039,9 +1044,11 @@ impl<'a, 'tcx> NamePrivacyVisitor<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for NamePrivacyVisitor<'a, 'tcx> {
+    type Map = Map<'tcx>;
+
     /// We want to visit items in the context of their containing
     /// module and so forth, so supply a crate for doing a deep walk.
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::All(&self.tcx.hir())
     }
 
@@ -1179,9 +1186,11 @@ impl<'a, 'tcx> TypePrivacyVisitor<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for TypePrivacyVisitor<'a, 'tcx> {
+    type Map = Map<'tcx>;
+
     /// We want to visit items in the context of their containing
     /// module and so forth, so supply a crate for doing a deep walk.
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::All(&self.tcx.hir())
     }
 
@@ -1437,7 +1446,9 @@ impl<'a, 'tcx> ObsoleteVisiblePrivateTypesVisitor<'a, 'tcx> {
 }
 
 impl<'a, 'b, 'tcx, 'v> Visitor<'v> for ObsoleteCheckTypeForPrivatenessVisitor<'a, 'b, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
+    type Map = Map<'v>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::None
     }
 
@@ -1463,9 +1474,11 @@ impl<'a, 'b, 'tcx, 'v> Visitor<'v> for ObsoleteCheckTypeForPrivatenessVisitor<'a
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for ObsoleteVisiblePrivateTypesVisitor<'a, 'tcx> {
+    type Map = Map<'tcx>;
+
     /// We want to visit items in the context of their containing
     /// module and so forth, so supply a crate for doing a deep walk.
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::All(&self.tcx.hir())
     }
 
@@ -1906,7 +1919,9 @@ impl<'a, 'tcx> PrivateItemsInPublicInterfacesVisitor<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for PrivateItemsInPublicInterfacesVisitor<'a, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
     }
 
diff --git a/src/librustc_resolve/lifetimes.rs b/src/librustc_resolve/lifetimes.rs
index 15858f7d8ab..215ab0fde02 100644
--- a/src/librustc_resolve/lifetimes.rs
+++ b/src/librustc_resolve/lifetimes.rs
@@ -361,7 +361,9 @@ fn sub_items_have_self_param(node: &hir::ItemKind<'_>) -> bool {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::All(&self.tcx.hir())
     }
 
@@ -1086,7 +1088,9 @@ fn extract_labels(ctxt: &mut LifetimeContext<'_, '_>, body: &hir::Body<'_>) {
     gather.visit_body(body);
 
     impl<'v, 'a, 'tcx> Visitor<'v> for GatherLabels<'a, 'tcx> {
-        fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
+        type Map = Map<'v>;
+
+        fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
             NestedVisitorMap::None
         }
 
@@ -2129,7 +2133,9 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
             }
 
             impl<'a> Visitor<'a> for SelfVisitor<'a> {
-                fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'a> {
+                type Map = Map<'a>;
+
+                fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
                     NestedVisitorMap::None
                 }
 
@@ -2217,7 +2223,9 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
         }
 
         impl<'v, 'a> Visitor<'v> for GatherLifetimes<'a> {
-            fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
+            type Map = Map<'v>;
+
+            fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
                 NestedVisitorMap::None
             }
 
@@ -2802,7 +2810,9 @@ fn insert_late_bound_lifetimes(
     }
 
     impl<'v> Visitor<'v> for ConstrainedCollector {
-        fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
+        type Map = Map<'v>;
+
+        fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
             NestedVisitorMap::None
         }
 
@@ -2843,7 +2853,9 @@ fn insert_late_bound_lifetimes(
     }
 
     impl<'v> Visitor<'v> for AllCollector {
-        fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
+        type Map = Map<'v>;
+
+        fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
             NestedVisitorMap::None
         }
 
diff --git a/src/librustc_traits/lowering/mod.rs b/src/librustc_traits/lowering/mod.rs
index 47009ac4123..647d32d45f6 100644
--- a/src/librustc_traits/lowering/mod.rs
+++ b/src/librustc_traits/lowering/mod.rs
@@ -2,6 +2,7 @@ mod environment;
 
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
 use rustc::hir::map::definitions::DefPathData;
+use rustc::hir::map::Map;
 use rustc::traits::{
     Clause, Clauses, DomainGoal, FromEnv, GoalKind, PolyDomainGoal, ProgramClause,
     ProgramClauseCategory, WellFormed, WhereClause,
@@ -600,7 +601,9 @@ impl ClauseDumper<'tcx> {
 }
 
 impl Visitor<'tcx> for ClauseDumper<'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, Self::Map> {
         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
     }
 
diff --git a/src/librustc_typeck/check/compare_method.rs b/src/librustc_typeck/check/compare_method.rs
index e1f2950469b..031f6e15d0d 100644
--- a/src/librustc_typeck/check/compare_method.rs
+++ b/src/librustc_typeck/check/compare_method.rs
@@ -1,5 +1,6 @@
 use errors::{pluralize, struct_span_err, Applicability, DiagnosticId};
 use rustc::hir::intravisit;
+use rustc::hir::map::Map;
 use rustc::infer::{self, InferOk};
 use rustc::traits::{self, ObligationCause, ObligationCauseCode, Reveal};
 use rustc::ty::error::{ExpectedFound, TypeError};
@@ -890,9 +891,10 @@ fn compare_synthetic_generics<'tcx>(
                                     }
                                 }
                             }
-                            fn nested_visit_map<'this>(
-                                &'this mut self,
-                            ) -> intravisit::NestedVisitorMap<'this, 'v>
+                            type Map = Map<'v>;
+                            fn nested_visit_map(
+                                &mut self,
+                            ) -> intravisit::NestedVisitorMap<'_, Self::Map>
                             {
                                 intravisit::NestedVisitorMap::None
                             }
diff --git a/src/librustc_typeck/check/generator_interior.rs b/src/librustc_typeck/check/generator_interior.rs
index f004d04fdfe..5936fe9b2a4 100644
--- a/src/librustc_typeck/check/generator_interior.rs
+++ b/src/librustc_typeck/check/generator_interior.rs
@@ -5,6 +5,7 @@
 
 use super::FnCtxt;
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::middle::region::{self, YieldData};
 use rustc::ty::{self, Ty};
 use rustc_data_structures::fx::FxHashMap;
@@ -193,7 +194,9 @@ pub fn resolve_interior<'a, 'tcx>(
 // librustc/middle/region.rs since `expr_count` is compared against the results
 // there.
 impl<'a, 'tcx> Visitor<'tcx> for InteriorVisitor<'a, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::None
     }
 
diff --git a/src/librustc_typeck/check/method/suggest.rs b/src/librustc_typeck/check/method/suggest.rs
index 8bf9f488e59..35e5588273b 100644
--- a/src/librustc_typeck/check/method/suggest.rs
+++ b/src/librustc_typeck/check/method/suggest.rs
@@ -7,6 +7,7 @@ use crate::namespace::Namespace;
 use errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder};
 use rustc::hir::intravisit;
 use rustc::hir::map as hir_map;
+use rustc::hir::map::Map;
 use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc::traits::Obligation;
 use rustc::ty::print::with_crate_prefix;
@@ -1124,7 +1125,9 @@ impl intravisit::Visitor<'tcx> for UsePlacementFinder<'tcx> {
         }
     }
 
-    fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
         intravisit::NestedVisitorMap::None
     }
 }
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index e6fbae09ba1..a977ecd8daf 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -92,6 +92,7 @@ use crate::middle::lang_items;
 use crate::namespace::Namespace;
 use errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, DiagnosticId};
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
 use rustc::infer::error_reporting::TypeAnnotationNeeded::E0282;
 use rustc::infer::opaque_types::OpaqueTypeDecl;
@@ -1170,7 +1171,9 @@ impl<'a, 'tcx> GatherLocalsVisitor<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::None
     }
 
diff --git a/src/librustc_typeck/check/regionck.rs b/src/librustc_typeck/check/regionck.rs
index 3b2f3d17e8d..b4fed3fe4e2 100644
--- a/src/librustc_typeck/check/regionck.rs
+++ b/src/librustc_typeck/check/regionck.rs
@@ -77,6 +77,7 @@ use crate::check::FnCtxt;
 use crate::mem_categorization as mc;
 use crate::middle::region;
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::infer::outlives::env::OutlivesEnvironment;
 use rustc::infer::{self, RegionObligation, SuppressRegionErrors};
 use rustc::ty::adjustment;
@@ -414,7 +415,9 @@ impl<'a, 'tcx> Visitor<'tcx> for RegionCtxt<'a, 'tcx> {
     // hierarchy, and in particular the relationships between free
     // regions, until regionck, as described in #3238.
 
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::None
     }
 
diff --git a/src/librustc_typeck/check/upvar.rs b/src/librustc_typeck/check/upvar.rs
index be912b6bcaf..8c107db2150 100644
--- a/src/librustc_typeck/check/upvar.rs
+++ b/src/librustc_typeck/check/upvar.rs
@@ -36,6 +36,7 @@ use crate::expr_use_visitor as euv;
 use crate::mem_categorization as mc;
 use crate::mem_categorization::PlaceBase;
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::infer::UpvarRegion;
 use rustc::ty::{self, Ty, TyCtxt, UpvarSubsts};
 use rustc_data_structures::fx::FxIndexMap;
@@ -59,7 +60,9 @@ struct InferBorrowKindVisitor<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for InferBorrowKindVisitor<'a, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::None
     }
 
diff --git a/src/librustc_typeck/check/writeback.rs b/src/librustc_typeck/check/writeback.rs
index ad9a2f2e2b4..f03bc21aef7 100644
--- a/src/librustc_typeck/check/writeback.rs
+++ b/src/librustc_typeck/check/writeback.rs
@@ -5,6 +5,7 @@
 use crate::check::FnCtxt;
 
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::infer::error_reporting::TypeAnnotationNeeded::E0282;
 use rustc::infer::InferCtxt;
 use rustc::ty::adjustment::{Adjust, Adjustment, PointerCast};
@@ -242,7 +243,9 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 // traffic in node-ids or update tables in the type context etc.
 
 impl<'cx, 'tcx> Visitor<'tcx> for WritebackCx<'cx, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::None
     }
 
diff --git a/src/librustc_typeck/collect.rs b/src/librustc_typeck/collect.rs
index 35c380612d2..50cd059fe8d 100644
--- a/src/librustc_typeck/collect.rs
+++ b/src/librustc_typeck/collect.rs
@@ -22,6 +22,7 @@ use crate::middle::resolve_lifetime as rl;
 use crate::middle::weak_lang_items;
 use errors::{struct_span_err, Applicability, StashKey};
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc::hir::map::Map;
 use rustc::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
 use rustc::mir::mono::Linkage;
 use rustc::traits;
@@ -104,7 +105,9 @@ pub struct ItemCtxt<'tcx> {
 crate struct PlaceholderHirTyCollector(crate Vec<Span>);
 
 impl<'v> Visitor<'v> for PlaceholderHirTyCollector {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
+    type Map = Map<'v>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::None
     }
     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
@@ -185,7 +188,9 @@ fn reject_placeholder_type_signatures_in_item(tcx: TyCtxt<'tcx>, item: &'tcx hir
 }
 
 impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
     }
 
@@ -885,7 +890,9 @@ fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<S
     }
 
     impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
-        fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+        type Map = Map<'tcx>;
+
+        fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
             NestedVisitorMap::None
         }
 
@@ -1715,7 +1722,9 @@ fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
     }
 
     impl<'tcx> intravisit::Visitor<'tcx> for ConstraintLocator<'tcx> {
-        fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
+        type Map = Map<'tcx>;
+
+        fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
             intravisit::NestedVisitorMap::All(&self.tcx.hir())
         }
         fn visit_item(&mut self, it: &'tcx Item<'tcx>) {
diff --git a/src/librustdoc/test.rs b/src/librustdoc/test.rs
index d94e940a7f7..cbef4f8ae69 100644
--- a/src/librustdoc/test.rs
+++ b/src/librustdoc/test.rs
@@ -899,7 +899,9 @@ impl<'a, 'hir> HirCollector<'a, 'hir> {
 }
 
 impl<'a, 'hir> intravisit::Visitor<'hir> for HirCollector<'a, 'hir> {
-    fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'hir> {
+    type Map = Map<'hir>;
+
+    fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
         intravisit::NestedVisitorMap::All(&self.map)
     }