diff --git a/src/librustc/infer/mod.rs b/src/librustc/infer/mod.rs
index 46074f6c1f3c..24716c479513 100644
--- a/src/librustc/infer/mod.rs
+++ b/src/librustc/infer/mod.rs
@@ -1657,7 +1657,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     {
         if let InferTables::Local(tables) = self.tables {
             if let Some(ty) = tables.borrow().closure_tys.get(&def_id) {
-                return ty.subst(self.tcx, substs.func_substs);
+                return ty.subst(self.tcx, substs.substs);
             }
         }
 
diff --git a/src/librustc/lib.rs b/src/librustc/lib.rs
index fa49e5c72895..8c0d70c6d602 100644
--- a/src/librustc/lib.rs
+++ b/src/librustc/lib.rs
@@ -40,6 +40,7 @@
 #![feature(rustc_private)]
 #![feature(slice_patterns)]
 #![feature(staged_api)]
+#![feature(unboxed_closures)]
 #![cfg_attr(stage0, feature(question_mark))]
 #![cfg_attr(test, feature(test))]
 
diff --git a/src/librustc/traits/select.rs b/src/librustc/traits/select.rs
index 3944c7e09c0b..6f6534cb2064 100644
--- a/src/librustc/traits/select.rs
+++ b/src/librustc/traits/select.rs
@@ -1912,16 +1912,16 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 tys.to_vec()
             }
 
-            ty::TyClosure(_, ref substs) => {
+            ty::TyClosure(def_id, ref substs) => {
                 // FIXME(#27086). We are invariant w/r/t our
-                // substs.func_substs, but we don't see them as
+                // func_substs, but we don't see them as
                 // constituent types; this seems RIGHT but also like
                 // something that a normal type couldn't simulate. Is
                 // this just a gap with the way that PhantomData and
                 // OIBIT interact? That is, there is no way to say
                 // "make me invariant with respect to this TYPE, but
                 // do not act as though I can reach it"
-                substs.upvar_tys.to_vec()
+                substs.upvar_tys(def_id, self.tcx()).collect()
             }
 
             // for `PhantomData<T>`, we pass `T`
diff --git a/src/librustc/ty/contents.rs b/src/librustc/ty/contents.rs
index 7ed4de38be97..9f80c2487fb2 100644
--- a/src/librustc/ty/contents.rs
+++ b/src/librustc/ty/contents.rs
@@ -98,10 +98,11 @@ impl TypeContents {
         TC::OwnsOwned | (*self & TC::OwnsAll)
     }
 
-    pub fn union<T, F>(v: &[T], mut f: F) -> TypeContents where
-        F: FnMut(&T) -> TypeContents,
+    pub fn union<I, T, F>(v: I, mut f: F) -> TypeContents where
+        I: IntoIterator<Item=T>,
+        F: FnMut(T) -> TypeContents,
     {
-        v.iter().fold(TC::None, |tc, ty| tc | f(ty))
+        v.into_iter().fold(TC::None, |tc, ty| tc | f(ty))
     }
 
     pub fn has_dtor(&self) -> bool {
@@ -215,8 +216,10 @@ impl<'a, 'tcx> ty::TyS<'tcx> {
                 }
                 ty::TyStr => TC::None,
 
-                ty::TyClosure(_, ref substs) => {
-                    TypeContents::union(&substs.upvar_tys, |ty| tc_ty(tcx, &ty, cache))
+                ty::TyClosure(def_id, ref substs) => {
+                    TypeContents::union(
+                        substs.upvar_tys(def_id, tcx),
+                        |ty| tc_ty(tcx, &ty, cache))
                 }
 
                 ty::TyTuple(ref tys) => {
diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index ac1c4fc6a191..45450456e8a6 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -1446,12 +1446,10 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 
     pub fn mk_closure(self,
                       closure_id: DefId,
-                      substs: &'tcx Substs<'tcx>,
-                      tys: &[Ty<'tcx>])
+                      substs: &'tcx Substs<'tcx>)
                       -> Ty<'tcx> {
         self.mk_closure_from_closure_substs(closure_id, ClosureSubsts {
-            func_substs: substs,
-            upvar_tys: self.intern_type_list(tys)
+            substs: substs
         })
     }
 
@@ -1574,4 +1572,3 @@ impl<T, R, E> InternIteratorElement<T, R> for Result<T, E> {
         Ok(f(&iter.collect::<Result<AccumulateVec<[_; 8]>, _>>()?))
     }
 }
-
diff --git a/src/librustc/ty/flags.rs b/src/librustc/ty/flags.rs
index 649d78f9d9e2..2c09b89beb23 100644
--- a/src/librustc/ty/flags.rs
+++ b/src/librustc/ty/flags.rs
@@ -88,8 +88,7 @@ impl FlagComputation {
             &ty::TyClosure(_, ref substs) => {
                 self.add_flags(TypeFlags::HAS_TY_CLOSURE);
                 self.add_flags(TypeFlags::HAS_LOCAL_NAMES);
-                self.add_substs(&substs.func_substs);
-                self.add_tys(&substs.upvar_tys);
+                self.add_substs(&substs.substs);
             }
 
             &ty::TyInfer(infer) => {
diff --git a/src/librustc/ty/layout.rs b/src/librustc/ty/layout.rs
index 5ce43d905ec7..5ee1c3678d67 100644
--- a/src/librustc/ty/layout.rs
+++ b/src/librustc/ty/layout.rs
@@ -631,7 +631,9 @@ impl<'a, 'gcx, 'tcx> Struct {
 
             // Perhaps one of the upvars of this closure is non-zero
             // Let's recurse and find out!
-            (_, &ty::TyClosure(_, ty::ClosureSubsts { upvar_tys: tys, .. })) |
+            (_, &ty::TyClosure(def_id, ref substs)) => {
+                Struct::non_zero_field_path(infcx, substs.upvar_tys(def_id, tcx))
+            }
             // Can we use one of the fields in this tuple?
             (_, &ty::TyTuple(tys)) => {
                 Struct::non_zero_field_path(infcx, tys.iter().cloned())
@@ -961,7 +963,13 @@ impl<'a, 'gcx, 'tcx> Layout {
             }
 
             // Tuples and closures.
-            ty::TyClosure(_, ty::ClosureSubsts { upvar_tys: tys, .. }) |
+            ty::TyClosure(def_id, ref substs) => {
+                let mut st = Struct::new(dl, false);
+                let tys = substs.upvar_tys(def_id, tcx);
+                st.extend(dl, tys.map(|ty| ty.layout(infcx)), ty)?;
+                Univariant { variant: st, non_zero: false }
+            }
+
             ty::TyTuple(tys) => {
                 let mut st = Struct::new(dl, false);
                 st.extend(dl, tys.iter().map(|ty| ty.layout(infcx)), ty)?;
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 3db705140411..1de54f49a552 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -2544,12 +2544,12 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         // tables by typeck; else, it will be retreived from
         // the external crate metadata.
         if let Some(ty) = self.tables.borrow().closure_tys.get(&def_id) {
-            return ty.subst(self, substs.func_substs);
+            return ty.subst(self, substs.substs);
         }
 
         let ty = self.sess.cstore.closure_ty(self.global_tcx(), def_id);
         self.tables.borrow_mut().closure_tys.insert(def_id, ty.clone());
-        ty.subst(self, substs.func_substs)
+        ty.subst(self, substs.substs)
     }
 
     /// Given the def_id of an impl, return the def_id of the trait it implements.
diff --git a/src/librustc/ty/outlives.rs b/src/librustc/ty/outlives.rs
index 51feab9d40c9..e3d13f593954 100644
--- a/src/librustc/ty/outlives.rs
+++ b/src/librustc/ty/outlives.rs
@@ -72,7 +72,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         // in the `subtys` iterator (e.g., when encountering a
         // projection).
         match ty.sty {
-            ty::TyClosure(_, ref substs) => {
+            ty::TyClosure(def_id, ref substs) => {
                 // FIXME(#27086). We do not accumulate from substs, since they
                 // don't represent reachable data. This means that, in
                 // practice, some of the lifetime parameters might not
@@ -110,7 +110,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                 // what func/type parameters are used and unused,
                 // taking into consideration UFCS and so forth.
 
-                for &upvar_ty in substs.upvar_tys {
+                for upvar_ty in substs.upvar_tys(def_id, *self) {
                     self.compute_components(upvar_ty, out);
                 }
             }
diff --git a/src/librustc/ty/relate.rs b/src/librustc/ty/relate.rs
index cb90e6392cf0..2a01bad33c52 100644
--- a/src/librustc/ty/relate.rs
+++ b/src/librustc/ty/relate.rs
@@ -534,13 +534,8 @@ impl<'tcx> Relate<'tcx> for ty::ClosureSubsts<'tcx> {
                            -> RelateResult<'tcx, ty::ClosureSubsts<'tcx>>
         where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
     {
-        let substs = relate_substs(relation, None, a.func_substs, b.func_substs)?;
-        assert_eq!(a.upvar_tys.len(), b.upvar_tys.len());
-        Ok(ty::ClosureSubsts {
-            func_substs: substs,
-            upvar_tys: relation.tcx().mk_type_list(
-                a.upvar_tys.iter().zip(b.upvar_tys).map(|(a, b)| relation.relate(a, b)))?
-        })
+        let substs = relate_substs(relation, None, a.substs, b.substs)?;
+        Ok(ty::ClosureSubsts { substs: substs })
     }
 }
 
diff --git a/src/librustc/ty/structural_impls.rs b/src/librustc/ty/structural_impls.rs
index 282cb9f80f51..e73be23a42c7 100644
--- a/src/librustc/ty/structural_impls.rs
+++ b/src/librustc/ty/structural_impls.rs
@@ -198,11 +198,8 @@ impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::Binder<T> {
 impl<'a, 'tcx> Lift<'tcx> for ty::ClosureSubsts<'a> {
     type Lifted = ty::ClosureSubsts<'tcx>;
     fn lift_to_tcx<'b, 'gcx>(&self, tcx: TyCtxt<'b, 'gcx, 'tcx>) -> Option<Self::Lifted> {
-        tcx.lift(&(self.func_substs, self.upvar_tys)).map(|(substs, upvar_tys)| {
-            ty::ClosureSubsts {
-                func_substs: substs,
-                upvar_tys: upvar_tys
-            }
+        tcx.lift(&self.substs).map(|substs| {
+            ty::ClosureSubsts { substs: substs }
         })
     }
 }
@@ -654,13 +651,12 @@ impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Region {
 impl<'tcx> TypeFoldable<'tcx> for ty::ClosureSubsts<'tcx> {
     fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
         ty::ClosureSubsts {
-            func_substs: self.func_substs.fold_with(folder),
-            upvar_tys: self.upvar_tys.fold_with(folder),
+            substs: self.substs.fold_with(folder),
         }
     }
 
     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
-        self.func_substs.visit_with(visitor) || self.upvar_tys.visit_with(visitor)
+        self.substs.visit_with(visitor)
     }
 }
 
diff --git a/src/librustc/ty/sty.rs b/src/librustc/ty/sty.rs
index 7d209093ec77..56466d596829 100644
--- a/src/librustc/ty/sty.rs
+++ b/src/librustc/ty/sty.rs
@@ -11,6 +11,7 @@
 //! This module contains TypeVariants and its major components
 
 use hir::def_id::DefId;
+
 use middle::region;
 use ty::subst::Substs;
 use ty::{self, AdtDef, ToPredicate, TypeFlags, Ty, TyCtxt, TypeFoldable};
@@ -254,15 +255,23 @@ pub enum TypeVariants<'tcx> {
 /// handle). Plus it fixes an ICE. :P
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub struct ClosureSubsts<'tcx> {
-    /// Lifetime and type parameters from the enclosing function.
+    /// Lifetime and type parameters from the enclosing function,
+    /// concatenated with the types of the upvars.
+    ///
     /// These are separated out because trans wants to pass them around
     /// when monomorphizing.
-    pub func_substs: &'tcx Substs<'tcx>,
+    pub substs: &'tcx Substs<'tcx>,
+}
 
-    /// The types of the upvars. The list parallels the freevars and
-    /// `upvar_borrows` lists. These are kept distinct so that we can
-    /// easily index into them.
-    pub upvar_tys: &'tcx Slice<Ty<'tcx>>
+impl<'a, 'gcx, 'acx, 'tcx> ClosureSubsts<'tcx> {
+    #[inline]
+    pub fn upvar_tys(self, def_id: DefId, tcx: TyCtxt<'a, 'gcx, 'acx>) ->
+        impl Iterator<Item=Ty<'tcx>> + 'tcx
+    {
+        let generics = tcx.item_generics(def_id);
+        self.substs[self.substs.len()-generics.own_count()..].iter().map(
+            |t| t.as_type().expect("unexpected region in upvars"))
+    }
 }
 
 #[derive(Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
@@ -1234,7 +1243,7 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> {
                 substs.regions().collect()
             }
             TyClosure(_, ref substs) => {
-                substs.func_substs.regions().collect()
+                substs.substs.regions().collect()
             }
             TyProjection(ref data) => {
                 data.trait_ref.substs.regions().collect()
diff --git a/src/librustc/ty/subst.rs b/src/librustc/ty/subst.rs
index 15f4437ed0aa..76d512a20b26 100644
--- a/src/librustc/ty/subst.rs
+++ b/src/librustc/ty/subst.rs
@@ -274,6 +274,20 @@ impl<'a, 'gcx, 'tcx> Substs<'tcx> {
         let defs = tcx.item_generics(source_ancestor);
         tcx.mk_substs(target_substs.iter().chain(&self[defs.own_count()..]).cloned())
     }
+
+    pub fn extend_with_types(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>,
+                             types: &[Ty<'tcx>])
+                             -> &'tcx Substs<'tcx> {
+        tcx.mk_substs(
+            self[..].iter().cloned().chain(
+                types.iter().map(|a| Kind::from(*a)))
+        )
+    }
+
+    pub fn truncate_to(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, generics: &ty::Generics<'tcx>)
+                       -> &'tcx Substs<'tcx> {
+        tcx.mk_substs(self.iter().take(generics.count()).cloned())
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for &'tcx Substs<'tcx> {
diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs
index b1aeaeb48d14..7d3e380a3b59 100644
--- a/src/librustc/ty/util.rs
+++ b/src/librustc/ty/util.rs
@@ -11,6 +11,7 @@
 //! misc. type-system utilities too small to deserve their own file
 
 use hir::def_id::DefId;
+use hir::map::DefPathData;
 use infer::InferCtxt;
 use hir::map as ast_map;
 use hir::pat_util;
@@ -390,6 +391,16 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         // (e.g. calling `foo.0.clone()` of `Foo<T:Clone>`).
         return !self.has_attr(dtor_method, "unsafe_destructor_blind_to_params");
     }
+
+    pub fn closure_base_def_id(&self, def_id: DefId) -> DefId {
+        let mut def_id = def_id;
+        while self.def_key(def_id).disambiguated_data.data == DefPathData::ClosureExpr {
+            def_id = self.parent_def_id(def_id).unwrap_or_else(|| {
+                bug!("closure {:?} has no parent", def_id);
+            });
+        }
+        def_id
+    }
 }
 
 /// When hashing a type this ends up affecting properties like symbol names. We
diff --git a/src/librustc/ty/walk.rs b/src/librustc/ty/walk.rs
index bebdebf127a5..a6ecfd2fb706 100644
--- a/src/librustc/ty/walk.rs
+++ b/src/librustc/ty/walk.rs
@@ -97,8 +97,7 @@ fn push_subtypes<'tcx>(stack: &mut Vec<Ty<'tcx>>, parent_ty: Ty<'tcx>) {
             stack.extend(substs.types().rev());
         }
         ty::TyClosure(_, ref substs) => {
-            stack.extend(substs.func_substs.types().rev());
-            stack.extend(substs.upvar_tys.iter().cloned().rev());
+            stack.extend(substs.substs.types().rev());
         }
         ty::TyTuple(ts) => {
             stack.extend(ts.iter().cloned().rev());
diff --git a/src/librustc/util/ppaux.rs b/src/librustc/util/ppaux.rs
index 3ed4580336aa..a63c7ba6a25c 100644
--- a/src/librustc/util/ppaux.rs
+++ b/src/librustc/util/ppaux.rs
@@ -907,13 +907,14 @@ impl<'tcx> fmt::Display for ty::TypeVariants<'tcx> {
             }
             TyStr => write!(f, "str"),
             TyClosure(did, substs) => ty::tls::with(|tcx| {
+                let upvar_tys = substs.upvar_tys(did, tcx);
                 write!(f, "[closure")?;
 
                 if let Some(node_id) = tcx.map.as_local_node_id(did) {
                     write!(f, "@{:?}", tcx.map.span(node_id))?;
                     let mut sep = " ";
                     tcx.with_freevars(node_id, |freevars| {
-                        for (freevar, upvar_ty) in freevars.iter().zip(substs.upvar_tys) {
+                        for (freevar, upvar_ty) in freevars.iter().zip(upvar_tys) {
                             let def_id = freevar.def.def_id();
                             let node_id = tcx.map.as_local_node_id(def_id).unwrap();
                             write!(f,
@@ -930,7 +931,7 @@ impl<'tcx> fmt::Display for ty::TypeVariants<'tcx> {
                     // visible in trans bug reports, I imagine.
                     write!(f, "@{:?}", did)?;
                     let mut sep = " ";
-                    for (index, upvar_ty) in substs.upvar_tys.iter().enumerate() {
+                    for (index, upvar_ty) in upvar_tys.enumerate() {
                         write!(f, "{}{}:{}", sep, index, upvar_ty)?;
                         sep = ", ";
                     }
diff --git a/src/librustc_borrowck/borrowck/mir/elaborate_drops.rs b/src/librustc_borrowck/borrowck/mir/elaborate_drops.rs
index eced5d1eb1b8..cdb19d164bf2 100644
--- a/src/librustc_borrowck/borrowck/mir/elaborate_drops.rs
+++ b/src/librustc_borrowck/borrowck/mir/elaborate_drops.rs
@@ -709,9 +709,11 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
             ty::TyAdt(def, substs) => {
                 self.open_drop_for_adt(c, def, substs)
             }
-            ty::TyTuple(tys) | ty::TyClosure(_, ty::ClosureSubsts {
-                upvar_tys: tys, ..
-            }) => {
+            ty::TyClosure(def_id, substs) => {
+                let tys : Vec<_> = substs.upvar_tys(def_id, self.tcx).collect();
+                self.open_drop_for_tuple(c, &tys)
+            }
+            ty::TyTuple(tys) => {
                 self.open_drop_for_tuple(c, tys)
             }
             ty::TyBox(ty) => {
diff --git a/src/librustc_metadata/encoder.rs b/src/librustc_metadata/encoder.rs
index f169ad664808..4d7aa43ce42d 100644
--- a/src/librustc_metadata/encoder.rs
+++ b/src/librustc_metadata/encoder.rs
@@ -1059,7 +1059,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             ty: None,
             inherent_impls: LazySeq::empty(),
             variances: LazySeq::empty(),
-            generics: None,
+            generics: Some(self.encode_generics(def_id)),
             predicates: None,
 
             ast: None,
diff --git a/src/librustc_mir/hair/cx/expr.rs b/src/librustc_mir/hair/cx/expr.rs
index ba0d3b49a6c1..24c1ca574a01 100644
--- a/src/librustc_mir/hair/cx/expr.rs
+++ b/src/librustc_mir/hair/cx/expr.rs
@@ -521,8 +521,8 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
             };
             let upvars = cx.tcx.with_freevars(expr.id, |freevars| {
                 freevars.iter()
-                    .enumerate()
-                    .map(|(i, fv)| capture_freevar(cx, expr, fv, substs.upvar_tys[i]))
+                    .zip(substs.upvar_tys(def_id, cx.tcx))
+                    .map(|(fv, ty)| capture_freevar(cx, expr, fv, ty))
                     .collect()
             });
             ExprKind::Closure {
diff --git a/src/librustc_mir/transform/type_check.rs b/src/librustc_mir/transform/type_check.rs
index ad525d210694..79bb14b7336c 100644
--- a/src/librustc_mir/transform/type_check.rs
+++ b/src/librustc_mir/transform/type_check.rs
@@ -274,9 +274,15 @@ impl<'a, 'b, 'gcx, 'tcx> TypeVerifier<'a, 'b, 'gcx, 'tcx> {
                 ty::TyAdt(adt_def, substs) if adt_def.is_univariant() => {
                         (&adt_def.variants[0], substs)
                     }
-                ty::TyTuple(tys) | ty::TyClosure(_, ty::ClosureSubsts {
-                    upvar_tys: tys, ..
-                }) => {
+                ty::TyClosure(def_id, substs) => {
+                    return match substs.upvar_tys(def_id, tcx).nth(field.index()) {
+                        Some(ty) => Ok(ty),
+                        None => Err(FieldAccessError::OutOfRange {
+                            field_count: substs.upvar_tys(def_id, tcx).count()
+                        })
+                    }
+                }
+                ty::TyTuple(tys) => {
                     return match tys.get(field.index()) {
                         Some(&ty) => Ok(ty),
                         None => Err(FieldAccessError::OutOfRange {
diff --git a/src/librustc_trans/adt.rs b/src/librustc_trans/adt.rs
index d028dd7e7b5a..c3340281d073 100644
--- a/src/librustc_trans/adt.rs
+++ b/src/librustc_trans/adt.rs
@@ -108,9 +108,9 @@ fn compute_fields<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>, t: Ty<'tcx>,
             }).collect::<Vec<_>>()
         },
         ty::TyTuple(fields) => fields.to_vec(),
-        ty::TyClosure(_, substs) => {
+        ty::TyClosure(def_id, substs) => {
             if variant_index > 0 { bug!("{} is a closure, which only has one variant", t);}
-            substs.upvar_tys.to_vec()
+            substs.upvar_tys(def_id, cx.tcx()).collect()
         },
         _ => bug!("{} is not a type that can have fields.", t)
     }
diff --git a/src/librustc_trans/closure.rs b/src/librustc_trans/closure.rs
index a1d645fb993b..0cefc49cb425 100644
--- a/src/librustc_trans/closure.rs
+++ b/src/librustc_trans/closure.rs
@@ -49,7 +49,7 @@ fn get_or_create_closure_declaration<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
     // duplicate declarations
     let tcx = ccx.tcx();
     let substs = tcx.erase_regions(&substs);
-    let instance = Instance::new(closure_id, substs.func_substs);
+    let instance = Instance::new(closure_id, substs.substs);
 
     if let Some(&llfn) = ccx.instances().borrow().get(&instance) {
         debug!("get_or_create_closure_declaration(): found closure {:?}: {:?}",
@@ -99,8 +99,7 @@ pub fn trans_closure_body_via_mir<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
     let tcx = ccx.tcx();
     let _icx = push_ctxt("closure::trans_closure_expr");
 
-    let param_substs = closure_substs.func_substs;
-    let instance = Instance::new(closure_def_id, param_substs);
+    let instance = Instance::new(closure_def_id, closure_substs.substs);
 
     // If we have not done so yet, translate this closure's body
     if  !ccx.instances().borrow().contains_key(&instance) {
@@ -138,7 +137,7 @@ pub fn trans_closure_body_via_mir<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 
         trans_closure(ccx,
                       llfn,
-                      Instance::new(closure_def_id, param_substs),
+                      instance,
                       &sig,
                       Abi::RustCall);
 
diff --git a/src/librustc_trans/collector.rs b/src/librustc_trans/collector.rs
index 41071057274f..a79719a4d227 100644
--- a/src/librustc_trans/collector.rs
+++ b/src/librustc_trans/collector.rs
@@ -452,7 +452,7 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
 
                 let concrete_substs = monomorphize::apply_param_substs(self.scx,
                                                                        self.param_substs,
-                                                                       &substs.func_substs);
+                                                                       &substs.substs);
                 let concrete_substs = self.scx.tcx().erase_regions(&concrete_substs);
 
                 let visitor = MirNeighborCollector {
@@ -797,8 +797,8 @@ fn find_drop_glue_neighbors<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
                 }
             }
         }
-        ty::TyClosure(_, substs) => {
-            for upvar_ty in substs.upvar_tys {
+        ty::TyClosure(def_id, substs) => {
+            for upvar_ty in substs.upvar_tys(def_id, scx.tcx()) {
                 let upvar_ty = glue::get_drop_glue_type(scx.tcx(), upvar_ty);
                 if glue::type_needs_drop(scx.tcx(), upvar_ty) {
                     output.push(TransItem::DropGlue(DropGlueKind::Ty(upvar_ty)));
diff --git a/src/librustc_trans/common.rs b/src/librustc_trans/common.rs
index d238cf7bb458..6f3a72621520 100644
--- a/src/librustc_trans/common.rs
+++ b/src/librustc_trans/common.rs
@@ -109,7 +109,16 @@ pub fn type_pair_fields<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, ty: Ty<'tcx>)
             Some([monomorphize::field_ty(ccx.tcx(), substs, &fields[0]),
                   monomorphize::field_ty(ccx.tcx(), substs, &fields[1])])
         }
-        ty::TyClosure(_, ty::ClosureSubsts { upvar_tys: tys, .. }) |
+        ty::TyClosure(def_id, substs) => {
+            let mut tys = substs.upvar_tys(def_id, ccx.tcx());
+            tys.next().and_then(|first_ty| tys.next().and_then(|second_ty| {
+                if tys.next().is_some() {
+                    None
+                } else {
+                    Some([first_ty, second_ty])
+                }
+            }))
+        }
         ty::TyTuple(tys) => {
             if tys.len() != 2 {
                 return None;
diff --git a/src/librustc_trans/debuginfo/metadata.rs b/src/librustc_trans/debuginfo/metadata.rs
index 679e308c3454..5b9ef78ddc22 100644
--- a/src/librustc_trans/debuginfo/metadata.rs
+++ b/src/librustc_trans/debuginfo/metadata.rs
@@ -574,10 +574,11 @@ pub fn type_metadata<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
             MetadataCreationResult::new(pointer_type_metadata(cx, t, fn_metadata), false)
 
         }
-        ty::TyClosure(_, ref substs) => {
+        ty::TyClosure(def_id, substs) => {
+            let upvar_tys : Vec<_> = substs.upvar_tys(def_id, cx.tcx()).collect();
             prepare_tuple_metadata(cx,
                                    t,
-                                   &substs.upvar_tys,
+                                   &upvar_tys,
                                    unique_type_id,
                                    usage_site_span).finalize(cx)
         }
diff --git a/src/librustc_trans/debuginfo/mod.rs b/src/librustc_trans/debuginfo/mod.rs
index 45b8ec1dc80b..482275d298bc 100644
--- a/src/librustc_trans/debuginfo/mod.rs
+++ b/src/librustc_trans/debuginfo/mod.rs
@@ -25,7 +25,6 @@ use llvm::{ModuleRef, ContextRef, ValueRef};
 use llvm::debuginfo::{DIFile, DIType, DIScope, DIBuilderRef, DISubprogram, DIArray,
                       FlagPrototyped};
 use rustc::hir::def_id::DefId;
-use rustc::hir::map::DefPathData;
 use rustc::ty::subst::Substs;
 
 use abi::Abi;
@@ -248,21 +247,19 @@ pub fn create_function_debug_context<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
     };
 
     // Find the enclosing function, in case this is a closure.
-    let mut fn_def_id = instance.def;
-    let mut def_key = cx.tcx().def_key(fn_def_id);
+    let def_key = cx.tcx().def_key(instance.def);
     let mut name = def_key.disambiguated_data.data.to_string();
     let name_len = name.len();
-    while def_key.disambiguated_data.data == DefPathData::ClosureExpr {
-        fn_def_id.index = def_key.parent.expect("closure without a parent?");
-        def_key = cx.tcx().def_key(fn_def_id);
-    }
+
+    let fn_def_id = cx.tcx().closure_base_def_id(instance.def);
 
     // Get_template_parameters() will append a `<...>` clause to the function
     // name if necessary.
     let generics = cx.tcx().item_generics(fn_def_id);
+    let substs = instance.substs.truncate_to(cx.tcx(), generics);
     let template_parameters = get_template_parameters(cx,
                                                       &generics,
-                                                      instance.substs,
+                                                      substs,
                                                       file_metadata,
                                                       &mut name);
 
diff --git a/src/librustc_trans/glue.rs b/src/librustc_trans/glue.rs
index 648dd9f3e3ae..d6d4d33923f1 100644
--- a/src/librustc_trans/glue.rs
+++ b/src/librustc_trans/glue.rs
@@ -531,8 +531,8 @@ fn drop_structural_ty<'blk, 'tcx>(cx: Block<'blk, 'tcx>,
 
     let mut cx = cx;
     match t.sty {
-        ty::TyClosure(_, ref substs) => {
-            for (i, upvar_ty) in substs.upvar_tys.iter().enumerate() {
+        ty::TyClosure(def_id, substs) => {
+            for (i, upvar_ty) in substs.upvar_tys(def_id, cx.tcx()).enumerate() {
                 let llupvar = adt::trans_field_ptr(cx, t, value, Disr(0), i);
                 cx = drop_ty(cx, llupvar, upvar_ty, DebugLoc::None);
             }
diff --git a/src/librustc_trans/mir/mod.rs b/src/librustc_trans/mir/mod.rs
index d2adf88c9168..12b17c26cbc4 100644
--- a/src/librustc_trans/mir/mod.rs
+++ b/src/librustc_trans/mir/mod.rs
@@ -470,8 +470,8 @@ fn arg_local_refs<'bcx, 'tcx>(bcx: &BlockAndBuilder<'bcx, 'tcx>,
             } else {
                 (arg_ty, false)
             };
-            let upvar_tys = if let ty::TyClosure(_, ref substs) = closure_ty.sty {
-                &substs.upvar_tys[..]
+            let upvar_tys = if let ty::TyClosure(def_id, substs) = closure_ty.sty {
+                substs.upvar_tys(def_id, tcx)
             } else {
                 bug!("upvar_decls with non-closure arg0 type `{}`", closure_ty);
             };
diff --git a/src/librustc_trans/trans_item.rs b/src/librustc_trans/trans_item.rs
index 93790cc27bca..16bc7e212cf5 100644
--- a/src/librustc_trans/trans_item.rs
+++ b/src/librustc_trans/trans_item.rs
@@ -477,12 +477,14 @@ pub fn push_unique_type_name<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                 push_unique_type_name(tcx, sig.output, output);
             }
         },
-        ty::TyClosure(def_id, ref closure_substs) => {
+        ty::TyClosure(def_id, closure_substs) => {
             push_item_name(tcx, def_id, output);
             output.push_str("{");
             output.push_str(&format!("{}:{}", def_id.krate, def_id.index.as_usize()));
             output.push_str("}");
-            push_type_params(tcx, closure_substs.func_substs, &[], output);
+            let generics = tcx.item_generics(tcx.closure_base_def_id(def_id));
+            let substs = closure_substs.substs.truncate_to(tcx, generics);
+            push_type_params(tcx, substs, &[], output);
         }
         ty::TyError |
         ty::TyInfer(_) |
diff --git a/src/librustc_typeck/check/closure.rs b/src/librustc_typeck/check/closure.rs
index af834f3f84d4..d48a129dfe1c 100644
--- a/src/librustc_typeck/check/closure.rs
+++ b/src/librustc_typeck/check/closure.rs
@@ -14,10 +14,13 @@ use super::{check_fn, Expectation, FnCtxt};
 
 use astconv::AstConv;
 use rustc::ty::{self, ToPolyTraitRef, Ty};
+use rustc::util::common::MemoizationMap;
 use std::cmp;
 use syntax::abi::Abi;
 use rustc::hir;
 
+use syntax::parse::token;
+
 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
     pub fn check_expr_closure(&self,
                               expr: &hir::Expr,
@@ -48,6 +51,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                      expected_sig: Option<ty::FnSig<'tcx>>)
                      -> Ty<'tcx> {
         let expr_def_id = self.tcx.map.local_def_id(expr.id);
+        let base_def_id = self.tcx.closure_base_def_id(expr_def_id);
 
         debug!("check_closure opt_kind={:?} expected_sig={:?}",
                opt_kind,
@@ -62,16 +66,42 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         // Create type variables (for now) to represent the transformed
         // types of upvars. These will be unified during the upvar
         // inference phase (`upvar.rs`).
-        let num_upvars = self.tcx.with_freevars(expr.id, |fv| fv.len());
+        let base_generics = self.tcx.item_generics(base_def_id);
+        // provide junk type parameter defs - the only place that
+        // cares about anything but the length is instantiation,
+        // and we don't do that for closures.
+        let upvar_decls : Vec<_> = self.tcx.with_freevars(expr.id, |fv| {
+            fv.iter().enumerate().map(|(i, _)| ty::TypeParameterDef {
+                index: (base_generics.count() as u32) + (i as u32),
+                name: token::intern("<upvar>"),
+                def_id: expr_def_id,
+                default_def_id: base_def_id,
+                default: None,
+                object_lifetime_default: ty::ObjectLifetimeDefault::BaseDefault,
+                pure_wrt_drop: false,
+            }).collect()
+        });
+        let num_upvars = upvar_decls.len();
+
+        self.tcx.generics.memoize(expr_def_id, || self.tcx.alloc_generics(ty::Generics {
+            parent: Some(base_def_id),
+            parent_regions: base_generics.parent_regions + (base_generics.regions.len() as u32),
+            parent_types: base_generics.parent_types + (base_generics.types.len() as u32),
+            regions: vec![],
+            types: upvar_decls,
+            has_self: false,
+        }));
+
         let upvar_tys = self.next_ty_vars(num_upvars);
 
         debug!("check_closure: expr.id={:?} upvar_tys={:?}",
                expr.id,
                upvar_tys);
 
-        let closure_type = self.tcx.mk_closure(expr_def_id,
-                                               self.parameter_environment.free_substs,
-                                               &upvar_tys);
+        let closure_type = self.tcx.mk_closure(
+            expr_def_id,
+            self.parameter_environment.free_substs.extend_with_types(self.tcx, &upvar_tys)
+        );
 
         let fn_sig = self.tcx
             .liberate_late_bound_regions(self.tcx.region_maps.call_site_extent(expr.id, body.id),
diff --git a/src/librustc_typeck/check/dropck.rs b/src/librustc_typeck/check/dropck.rs
index 8657b30bf8ee..09e1f6592c17 100644
--- a/src/librustc_typeck/check/dropck.rs
+++ b/src/librustc_typeck/check/dropck.rs
@@ -482,8 +482,14 @@ fn iterate_over_potentially_unsafe_regions_in_type<'a, 'b, 'gcx, 'tcx>(
             Ok(())
         }
 
-        ty::TyTuple(tys) |
-        ty::TyClosure(_, ty::ClosureSubsts { upvar_tys: tys, .. }) => {
+        ty::TyClosure(def_id, substs) => {
+            for ty in substs.upvar_tys(def_id, tcx) {
+                iterate_over_potentially_unsafe_regions_in_type(cx, context, ty, depth+1)?
+            }
+            Ok(())
+        }
+
+        ty::TyTuple(tys) => {
             for ty in tys {
                 iterate_over_potentially_unsafe_regions_in_type(cx, context, ty, depth+1)?
             }
diff --git a/src/librustc_typeck/check/upvar.rs b/src/librustc_typeck/check/upvar.rs
index 2fea86cb2120..1ea47107c3b1 100644
--- a/src/librustc_typeck/check/upvar.rs
+++ b/src/librustc_typeck/check/upvar.rs
@@ -183,8 +183,8 @@ impl<'a, 'gcx, 'tcx> AdjustBorrowKind<'a, 'gcx, 'tcx> {
         // inference algorithm will reject it).
 
         // Extract the type variables UV0...UVn.
-        let closure_substs = match self.fcx.node_ty(id).sty {
-            ty::TyClosure(_, ref substs) => substs,
+        let (def_id, closure_substs) = match self.fcx.node_ty(id).sty {
+            ty::TyClosure(def_id, substs) => (def_id, substs),
             ref t => {
                 span_bug!(
                     span,
@@ -197,7 +197,9 @@ impl<'a, 'gcx, 'tcx> AdjustBorrowKind<'a, 'gcx, 'tcx> {
         let final_upvar_tys = self.final_upvar_tys(id);
         debug!("analyze_closure: id={:?} closure_substs={:?} final_upvar_tys={:?}",
                id, closure_substs, final_upvar_tys);
-        for (&upvar_ty, final_upvar_ty) in closure_substs.upvar_tys.iter().zip(final_upvar_tys) {
+        for (upvar_ty, final_upvar_ty) in
+            closure_substs.upvar_tys(def_id, self.fcx.tcx).zip(final_upvar_tys)
+        {
             self.fcx.demand_eqtype(span, final_upvar_ty, upvar_ty);
         }