avoid calling `mk_region` unnecessarily

this improves typeck & trans performance by 1%. This looked hotter on
callgrind than it is on a CPU.

src/librustc/infer/freshen.rs

@@ -99,7 +99,7 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for TypeFreshener<'a, 'gcx, 'tcx> {
             ty::ReEmpty |
             ty::ReErased => {
                 // replace all free regions with 'erased
-                self.tcx().mk_region(ty::ReErased)
+                self.tcx().types.re_erased
             }
         }
     }

src/librustc/infer/region_inference/mod.rs

@@ -948,7 +948,7 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> {
                 } else {
                     // otherwise, we don't know what the free region is,
                     // so we must conservatively say the LUB is static:
-                    self.tcx.mk_region(ReStatic)
+                    self.tcx.types.re_static
                 }
             }
 
@@ -971,7 +971,7 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> {
                 if a == b {
                     a
                 } else {
-                    self.tcx.mk_region(ReStatic)
+                    self.tcx.types.re_static
                 }
             }
         }
@@ -1018,7 +1018,7 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> {
 
     fn construct_var_data(&self) -> Vec<VarValue<'tcx>> {
         (0..self.num_vars() as usize)
-            .map(|_| Value(self.tcx.mk_region(ty::ReEmpty)))
+            .map(|_| Value(self.tcx.types.re_empty))
             .collect()
     }
 
@@ -1493,7 +1493,7 @@ fn lookup<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
                           -> &'tcx ty::Region {
     match values[rid.index as usize] {
         Value(r) => r,
-        ErrorValue => tcx.mk_region(ReStatic), // Previously reported error.
+        ErrorValue => tcx.types.re_static, // Previously reported error.
     }
 }
 

src/librustc/middle/expr_use_visitor.rs

@@ -426,7 +426,7 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
 
             hir::ExprMatch(ref discr, ref arms, _) => {
                 let discr_cmt = return_if_err!(self.mc.cat_expr(&discr));
-                let r = self.tcx().mk_region(ty::ReEmpty);
+                let r = self.tcx().types.re_empty;
                 self.borrow_expr(&discr, r, ty::ImmBorrow, MatchDiscriminant);
 
                 // treatment of the discriminant is handled while walking the arms.

src/librustc/middle/mem_categorization.rs

@@ -871,8 +871,8 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
         // we can promote to a constant, otherwise equal to enclosing temp
         // lifetime.
         let (re, old_re) = if promotable {
-            (self.tcx().mk_region(ty::ReStatic),
-             self.tcx().mk_region(ty::ReStatic))
+            (self.tcx().types.re_static,
+             self.tcx().types.re_static)
         } else {
             self.temporary_scope(id)
         };

src/librustc/traits/fulfill.rs

@@ -443,7 +443,7 @@ fn process_predicate<'a, 'gcx, 'tcx>(
                         // Otherwise, we have something of the form
                         // `for<'a> T: 'a where 'a not in T`, which we can treat as `T: 'static`.
                         Some(t_a) => {
-                            let r_static = selcx.tcx().mk_region(ty::ReStatic);
+                            let r_static = selcx.tcx().types.re_static;
                             register_region_obligation(t_a, r_static,
                                                        obligation.cause.clone(),
                                                        region_obligations);

src/librustc/traits/mod.rs

@@ -629,7 +629,7 @@ pub fn get_vtable_methods<'a, 'tcx>(
             // the method may have some early-bound lifetimes, add
             // regions for those
             let substs = Substs::for_item(tcx, def_id,
-                                          |_, _| tcx.mk_region(ty::ReErased),
+                                          |_, _| tcx.types.re_erased,
                                           |def, _| trait_ref.substs().type_for_def(def));
 
             // the trait type may have higher-ranked lifetimes in it;

src/librustc/ty/context.rs

@@ -190,6 +190,10 @@ pub struct CommonTypes<'tcx> {
     pub f64: Ty<'tcx>,
     pub never: Ty<'tcx>,
     pub err: Ty<'tcx>,
+
+    pub re_empty: &'tcx Region,
+    pub re_static: &'tcx Region,
+    pub re_erased: &'tcx Region,
 }
 
 #[derive(RustcEncodable, RustcDecodable)]
@@ -360,6 +364,14 @@ impl<'tcx> TypeckTables<'tcx> {
 impl<'tcx> CommonTypes<'tcx> {
     fn new(interners: &CtxtInterners<'tcx>) -> CommonTypes<'tcx> {
         let mk = |sty| interners.intern_ty(sty, None);
+        let mk_region = |r| {
+            if let Some(r) = interners.region.borrow().get(&r) {
+                return r.0;
+            }
+            let r = interners.arena.alloc(r);
+            interners.region.borrow_mut().insert(Interned(r));
+            &*r
+        };
         CommonTypes {
             bool: mk(TyBool),
             char: mk(TyChar),
@@ -379,6 +391,10 @@ impl<'tcx> CommonTypes<'tcx> {
             u128: mk(TyUint(ast::UintTy::U128)),
             f32: mk(TyFloat(ast::FloatTy::F32)),
             f64: mk(TyFloat(ast::FloatTy::F64)),
+
+            re_empty: mk_region(Region::ReEmpty),
+            re_static: mk_region(Region::ReStatic),
+            re_erased: mk_region(Region::ReErased),
         }
     }
 }
@@ -1232,7 +1248,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     }
 
     pub fn mk_static_str(self) -> Ty<'tcx> {
-        self.mk_imm_ref(self.mk_region(ty::ReStatic), self.mk_str())
+        self.mk_imm_ref(self.types.re_static, self.mk_str())
     }
 
     pub fn mk_adt(self, def: &'tcx AdtDef, substs: &'tcx Substs<'tcx>) -> Ty<'tcx> {

src/librustc/ty/fold.rs

@@ -410,7 +410,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     pub fn erase_late_bound_regions<T>(self, value: &Binder<T>) -> T
         where T : TypeFoldable<'tcx>
     {
-        self.replace_late_bound_regions(value, |_| self.mk_region(ty::ReErased)).0
+        self.replace_late_bound_regions(value, |_| self.types.re_erased).0
     }
 
     /// Rewrite any late-bound regions so that they are anonymous.  Region numbers are
@@ -538,7 +538,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                 // whenever a substitution occurs.
                 match *r {
                     ty::ReLateBound(..) => r,
-                    _ => self.tcx().mk_region(ty::ReErased)
+                    _ => self.tcx().types.re_erased
                 }
             }
         }
@@ -565,6 +565,22 @@ pub fn shift_region(region: ty::Region, amount: u32) -> ty::Region {
     }
 }
 
+pub fn shift_region_ref<'a, 'gcx, 'tcx>(
+    tcx: TyCtxt<'a, 'gcx, 'tcx>,
+    region: &'tcx ty::Region,
+    amount: u32)
+    -> &'tcx ty::Region
+{
+    match region {
+        &ty::ReLateBound(debruijn, br) if amount > 0 => {
+            tcx.mk_region(ty::ReLateBound(debruijn.shifted(amount), br))
+        }
+        _ => {
+            region
+        }
+    }
+}
+
 pub fn shift_regions<'a, 'gcx, 'tcx, T>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
                                         amount: u32, value: &T) -> T
     where T: TypeFoldable<'tcx>
@@ -573,7 +589,7 @@ pub fn shift_regions<'a, 'gcx, 'tcx, T>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
            value, amount);
 
     value.fold_with(&mut RegionFolder::new(tcx, &mut false, &mut |region, _current_depth| {
-        tcx.mk_region(shift_region(*region, amount))
+        shift_region_ref(tcx, region, amount)
     }))
 }
 

src/librustc/ty/mod.rs

@@ -2499,15 +2499,13 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     /// Construct a parameter environment suitable for static contexts or other contexts where there
     /// are no free type/lifetime parameters in scope.
     pub fn empty_parameter_environment(self) -> ParameterEnvironment<'tcx> {
-
-        // for an empty parameter environment, there ARE no free
-        // regions, so it shouldn't matter what we use for the free id
-        let free_id_outlive = self.region_maps.node_extent(ast::DUMMY_NODE_ID);
         ty::ParameterEnvironment {
             free_substs: self.intern_substs(&[]),
             caller_bounds: Vec::new(),
-            implicit_region_bound: self.mk_region(ty::ReEmpty),
-            free_id_outlive: free_id_outlive,
+            implicit_region_bound: self.types.re_empty,
+            // for an empty parameter environment, there ARE no free
+            // regions, so it shouldn't matter what we use for the free id
+            free_id_outlive: ROOT_CODE_EXTENT,
             is_copy_cache: RefCell::new(FxHashMap()),
             is_sized_cache: RefCell::new(FxHashMap()),
             is_freeze_cache: RefCell::new(FxHashMap()),
@@ -2760,4 +2758,3 @@ pub fn provide_extern(providers: &mut ty::maps::Providers) {
 pub struct CrateInherentImpls {
     pub inherent_impls: DefIdMap<Rc<Vec<DefId>>>,
 }
-

src/librustc/ty/subst.rs

@@ -539,6 +539,9 @@ impl<'a, 'gcx, 'tcx> SubstFolder<'a, 'gcx, 'tcx> {
     }
 
     fn shift_region_through_binders(&self, region: &'tcx ty::Region) -> &'tcx ty::Region {
+        if self.region_binders_passed == 0 || !region.has_escaping_regions() {
+            return region;
+        }
         self.tcx().mk_region(ty::fold::shift_region(*region, self.region_binders_passed))
     }
 }

src/librustc/ty/util.rs

@@ -412,7 +412,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     /// a suitable "empty substs" for it.
     pub fn empty_substs_for_def_id(self, item_def_id: DefId) -> &'tcx ty::Substs<'tcx> {
         ty::Substs::for_item(self, item_def_id,
-                             |_, _| self.mk_region(ty::ReErased),
+                             |_, _| self.types.re_erased,
                              |_, _| {
             bug!("empty_substs_for_def_id: {:?} has type parameters", item_def_id)
         })

src/librustc_borrowck/borrowck/gather_loans/lifetime.rs

@@ -120,7 +120,7 @@ impl<'a, 'tcx> GuaranteeLifetimeContext<'a, 'tcx> {
             }
             Categorization::StaticItem |
             Categorization::Deref(.., mc::UnsafePtr(..)) => {
-                self.bccx.tcx.mk_region(ty::ReStatic)
+                self.bccx.tcx.types.re_static
             }
             Categorization::Deref(.., mc::BorrowedPtr(_, r)) |
             Categorization::Deref(.., mc::Implicit(_, r)) => {

src/librustc_driver/test.rs

@@ -343,12 +343,12 @@ impl<'a, 'gcx, 'tcx> Env<'a, 'gcx, 'tcx> {
     }
 
     pub fn t_rptr_static(&self) -> Ty<'tcx> {
-        self.infcx.tcx.mk_imm_ref(self.infcx.tcx.mk_region(ty::ReStatic),
+        self.infcx.tcx.mk_imm_ref(self.infcx.tcx.types.re_static,
                                   self.tcx().types.isize)
     }
 
     pub fn t_rptr_empty(&self) -> Ty<'tcx> {
-        self.infcx.tcx.mk_imm_ref(self.infcx.tcx.mk_region(ty::ReEmpty),
+        self.infcx.tcx.mk_imm_ref(self.infcx.tcx.types.re_empty,
                                   self.tcx().types.isize)
     }
 

src/librustc_mir/build/matches/test.rs

@@ -280,7 +280,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                     assert!(ty.is_slice());
 
                     let array_ty = tcx.mk_array(tcx.types.u8, bytes.len());
-                    let array_ref = tcx.mk_imm_ref(tcx.mk_region(ty::ReStatic), array_ty);
+                    let array_ref = tcx.mk_imm_ref(tcx.types.re_static, array_ty);
                     let array = self.literal_operand(test.span, array_ref, Literal::Value {
                         value: value.clone()
                     });

src/librustc_mir/shim.rs

@@ -308,10 +308,9 @@ fn build_call_shim<'a, 'tcx>(tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
         Adjustment::Deref => Operand::Consume(rcvr_l.deref()),
         Adjustment::RefMut => {
             // let rcvr = &mut rcvr;
-            let re_erased = tcx.mk_region(ty::ReErased);
             let ref_rcvr = local_decls.push(temp_decl(
                 Mutability::Not,
-                tcx.mk_ref(re_erased, ty::TypeAndMut {
+                tcx.mk_ref(tcx.types.re_erased, ty::TypeAndMut {
                     ty: sig.inputs()[0],
                     mutbl: hir::Mutability::MutMutable
                 }),
@@ -321,7 +320,7 @@ fn build_call_shim<'a, 'tcx>(tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
                 source_info: source_info,
                 kind: StatementKind::Assign(
                     Lvalue::Local(ref_rcvr),
-                    Rvalue::Ref(re_erased, BorrowKind::Mut, rcvr_l)
+                    Rvalue::Ref(tcx.types.re_erased, BorrowKind::Mut, rcvr_l)
                 )
             });
             Operand::Consume(Lvalue::Local(ref_rcvr))

src/librustc_mir/transform/erase_regions.rs

@@ -13,7 +13,7 @@
 //! care erasing regions all over the place.
 
 use rustc::ty::subst::Substs;
-use rustc::ty::{Ty, TyCtxt, ReErased, ClosureSubsts};
+use rustc::ty::{Ty, TyCtxt, ClosureSubsts};
 use rustc::mir::*;
 use rustc::mir::visit::MutVisitor;
 use rustc::mir::transform::{MirPass, MirSource, Pass};
@@ -43,7 +43,7 @@ impl<'a, 'tcx> MutVisitor<'tcx> for EraseRegionsVisitor<'a, 'tcx> {
     fn visit_rvalue(&mut self, rvalue: &mut Rvalue<'tcx>, location: Location) {
         match *rvalue {
             Rvalue::Ref(ref mut r, _, _) => {
-                *r = self.tcx.mk_region(ReErased);
+                *r = self.tcx.types.re_erased;
             }
             Rvalue::Use(..) |
             Rvalue::Repeat(..) |

src/librustc_mir/transform/inline.rs

@@ -497,7 +497,7 @@ impl<'a, 'tcx> Inliner<'a, 'tcx> {
                 let dest = if dest_needs_borrow(&destination.0) {
                     debug!("Creating temp for return destination");
                     let dest = Rvalue::Ref(
-                        self.tcx.mk_region(ty::ReErased),
+                        self.tcx.types.re_erased,
                         BorrowKind::Mut,
                         destination.0);
 
@@ -582,7 +582,7 @@ impl<'a, 'tcx> Inliner<'a, 'tcx> {
     fn cast_box_free_arg(&self, arg: Lvalue<'tcx>, ptr_ty: Ty<'tcx>,
                          callsite: &CallSite<'tcx>, caller_mir: &mut Mir<'tcx>) -> Operand<'tcx> {
         let arg = Rvalue::Ref(
-            self.tcx.mk_region(ty::ReErased),
+            self.tcx.types.re_erased,
             BorrowKind::Mut,
             arg.deref());
 

src/librustc_mir/util/elaborate_drops.rs

@@ -506,8 +506,7 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
         let ty = self.lvalue_ty(self.lvalue);
         let substs = tcx.mk_substs(iter::once(Kind::from(ty)));
 
-        let re_erased = tcx.mk_region(ty::ReErased);
-        let ref_ty = tcx.mk_ref(re_erased, ty::TypeAndMut {
+        let ref_ty = tcx.mk_ref(tcx.types.re_erased, ty::TypeAndMut {
             ty: ty,
             mutbl: hir::Mutability::MutMutable
         });
@@ -519,7 +518,7 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
                 source_info: self.source_info,
                 kind: StatementKind::Assign(
                     Lvalue::Local(ref_lvalue),
-                    Rvalue::Ref(re_erased, BorrowKind::Mut, self.lvalue.clone())
+                    Rvalue::Ref(tcx.types.re_erased, BorrowKind::Mut, self.lvalue.clone())
                 )
             }],
             terminator: Some(Terminator {

src/librustc_trans/mir/constant.rs

@@ -708,7 +708,7 @@ impl<'a, 'tcx> MirConstContext<'a, 'tcx> {
                 let tr_lvalue = self.const_lvalue(lvalue, span)?;
 
                 let ty = tr_lvalue.ty;
-                let ref_ty = tcx.mk_ref(tcx.mk_region(ty::ReErased),
+                let ref_ty = tcx.mk_ref(tcx.types.re_erased,
                     ty::TypeAndMut { ty: ty, mutbl: bk.to_mutbl_lossy() });
 
                 let base = match tr_lvalue.base {

src/librustc_trans/mir/rvalue.rs

@@ -329,7 +329,7 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
 
                 let ty = tr_lvalue.ty.to_ty(bcx.tcx());
                 let ref_ty = bcx.tcx().mk_ref(
-                    bcx.tcx().mk_region(ty::ReErased),
+                    bcx.tcx().types.re_erased,
                     ty::TypeAndMut { ty: ty, mutbl: bk.to_mutbl_lossy() }
                 );
 

src/librustc_typeck/astconv.rs

@@ -109,7 +109,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
         let tcx = self.tcx();
         let r = match tcx.named_region_map.defs.get(&lifetime.id) {
             Some(&rl::Region::Static) => {
-                tcx.mk_region(ty::ReStatic)
+                tcx.types.re_static
             }
 
             Some(&rl::Region::LateBound(debruijn, id)) => {
@@ -171,7 +171,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
                     .emit();
 
                 return Substs::for_item(tcx, def_id, |_, _| {
-                    tcx.mk_region(ty::ReStatic)
+                    tcx.types.re_static
                 }, |_, _| {
                     tcx.types.err
                 });
@@ -254,7 +254,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
             if let Some(lifetime) = lifetimes.get(i) {
                 self.ast_region_to_region(lifetime, Some(def))
             } else {
-                tcx.mk_region(ty::ReStatic)
+                tcx.types.re_static
             }
         }, |def, substs| {
             let i = def.index as usize;
@@ -715,7 +715,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
                         span_err!(tcx.sess, span, E0228,
                                   "the lifetime bound for this object type cannot be deduced \
                                    from context; please supply an explicit bound");
-                        tcx.mk_region(ty::ReStatic)
+                        tcx.types.re_static
                     })
                 }
             })
@@ -1357,7 +1357,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
         // If any of the derived region bounds are 'static, that is always
         // the best choice.
         if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
-            return Some(tcx.mk_region(ty::ReStatic));
+            return Some(tcx.types.re_static);
         }
 
         // Determine whether there is exactly one unique region in the set

src/librustc_typeck/check/_match.rs

@@ -55,7 +55,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                         let expected_ty = self.structurally_resolved_type(pat.span, expected);
                         if let ty::TyRef(_, mt) = expected_ty.sty {
                             if let ty::TySlice(_) = mt.ty.sty {
-                                pat_ty = tcx.mk_imm_ref(tcx.mk_region(ty::ReStatic),
+                                pat_ty = tcx.mk_imm_ref(tcx.types.re_static,
                                                          tcx.mk_slice(tcx.types.u8))
                             }
                         }

src/librustc_typeck/check/dropck.rs

@@ -626,7 +626,7 @@ fn revise_self_ty<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
             let impl_self_orig = self_substs.region_for_def(def);
             let r = if let ty::Region::ReEarlyBound(ref ebr) = *impl_self_orig {
                 if impl_bindings.region_param(ebr).pure_wrt_drop {
-                    tcx.mk_region(ty::ReStatic)
+                    tcx.types.re_static
                 } else {
                     r_orig
                 }

src/librustc_typeck/check/intrinsic.rs

@@ -36,7 +36,7 @@ fn equate_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let def_id = tcx.hir.local_def_id(it.id);
 
     let substs = Substs::for_item(tcx, def_id,
-                                  |_, _| tcx.mk_region(ty::ReErased),
+                                  |_, _| tcx.types.re_erased,
                                   |def, _| tcx.mk_param_from_def(def));
 
     let fty = tcx.mk_fn_def(def_id, substs, ty::Binder(tcx.mk_fn_sig(

src/librustc_typeck/check/method/probe.rs

@@ -1063,7 +1063,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
 
         // In general, during probing we erase regions. See
         // `impl_self_ty()` for an explanation.
-        let region = tcx.mk_region(ty::ReErased);
+        let region = tcx.types.re_erased;
 
         // Search through mutabilities in order to find one where pick works:
         [hir::MutImmutable, hir::MutMutable]
@@ -1325,7 +1325,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
                 } else {
                     // In general, during probe we erase regions. See
                     // `impl_self_ty()` for an explanation.
-                    self.tcx.mk_region(ty::ReErased)
+                    self.tcx.types.re_erased
                 }
             }, |def, cur_substs| {
                 let i = def.index as usize;
@@ -1345,7 +1345,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
 
         let substs = Substs::for_item(self.tcx,
                                       impl_def_id,
-                                      |_, _| self.tcx.mk_region(ty::ReErased),
+                                      |_, _| self.tcx.types.re_erased,
                                       |_, _| self.next_ty_var(
                                         TypeVariableOrigin::SubstitutionPlaceholder(
                                             self.tcx.def_span(impl_def_id))));

src/librustc_typeck/check/mod.rs

@@ -1954,7 +1954,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         //
         // FIXME(#27579) all uses of this should be migrated to register_wf_obligation eventually
         let cause = traits::ObligationCause::new(span, self.body_id, code);
-        self.register_region_obligation(ty, self.tcx.mk_region(ty::ReEmpty), cause);
+        self.register_region_obligation(ty, self.tcx.types.re_empty, cause);
     }
 
     /// Registers obligations that all types appearing in `substs` are well-formed.
@@ -2513,7 +2513,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         match lit.node {
             ast::LitKind::Str(..) => tcx.mk_static_str(),
             ast::LitKind::ByteStr(ref v) => {
-                tcx.mk_imm_ref(tcx.mk_region(ty::ReStatic),
+                tcx.mk_imm_ref(tcx.types.re_static,
                                 tcx.mk_array(tcx.types.u8, v.len()))
             }
             ast::LitKind::Byte(_) => tcx.types.u8,

src/librustc_typeck/check/writeback.rs

@@ -288,8 +288,8 @@ impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
             let outside_ty = gcx.fold_regions(&inside_ty, &mut false, |r, _| {
                 match *r {
                     // 'static is valid everywhere.
-                    ty::ReStatic |
-                    ty::ReEmpty => gcx.mk_region(*r),
+                    ty::ReStatic => gcx.types.re_static,
+                    ty::ReEmpty => gcx.types.re_empty,
 
                     // Free regions that come from early-bound regions are valid.
                     ty::ReFree(ty::FreeRegion {
@@ -307,7 +307,7 @@ impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
                         span_err!(self.tcx().sess, span, E0564,
                                   "only named lifetimes are allowed in `impl Trait`, \
                                    but `{}` was found in the type `{}`", r, inside_ty);
-                        gcx.mk_region(ty::ReStatic)
+                        gcx.types.re_static
                     }
 
                     ty::ReVar(_) |
@@ -526,7 +526,7 @@ impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for Resolver<'cx, 'gcx, 'tcx> {
         match self.infcx.fully_resolve(&r) {
             Ok(r) => r,
             Err(_) => {
-                self.tcx.mk_region(ty::ReStatic)
+                self.tcx.types.re_static
             }
         }
     }