diff --git a/src/librustc/ich/impls_ty.rs b/src/librustc/ich/impls_ty.rs
index fc0a9ac9d18..eddb73e7239 100644
--- a/src/librustc/ich/impls_ty.rs
+++ b/src/librustc/ich/impls_ty.rs
@@ -753,34 +753,23 @@ impl<'a> HashStable<StableHashingContext<'a>> for ty::Generics {
     }
 }
 
-impl_stable_hash_for!(enum ty::GenericParamDef {
+impl_stable_hash_for!(enum ty::GenericParamDefKind {
     Lifetime(lt),
     Type(ty)
 });
 
-impl<'a> HashStable<StableHashingContext<'a>>
-for ty::RegionParamDef {
-    fn hash_stable<W: StableHasherResult>(&self,
-                                          hcx: &mut StableHashingContext<'a>,
-                                          hasher: &mut StableHasher<W>) {
-        let ty::RegionParamDef {
-            name,
-            def_id,
-            index,
-            pure_wrt_drop
-        } = *self;
-
-        name.hash_stable(hcx, hasher);
-        def_id.hash_stable(hcx, hasher);
-        index.hash_stable(hcx, hasher);
-        pure_wrt_drop.hash_stable(hcx, hasher);
-    }
-}
-
-impl_stable_hash_for!(struct ty::TypeParamDef {
+impl_stable_hash_for!(struct ty::GenericParamDef {
     name,
     def_id,
     index,
+    kind
+});
+
+impl_stable_hash_for!(struct ty::RegionParamDef {
+    pure_wrt_drop
+});
+
+impl_stable_hash_for!(struct ty::TypeParamDef {
     has_default,
     object_lifetime_default,
     pure_wrt_drop,
diff --git a/src/librustc/infer/anon_types/mod.rs b/src/librustc/infer/anon_types/mod.rs
index a83eb7fd354..0af95a74686 100644
--- a/src/librustc/infer/anon_types/mod.rs
+++ b/src/librustc/infer/anon_types/mod.rs
@@ -14,7 +14,7 @@ use infer::outlives::free_region_map::FreeRegionRelations;
 use rustc_data_structures::fx::FxHashMap;
 use syntax::ast;
 use traits::{self, PredicateObligation};
-use ty::{self, Ty, TyCtxt, GenericParamDef};
+use ty::{self, Ty, TyCtxt, GenericParamDefKind};
 use ty::fold::{BottomUpFolder, TypeFoldable, TypeFolder};
 use ty::outlives::Component;
 use ty::subst::{Kind, Substs, UnpackedKind};
@@ -313,16 +313,14 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         // `['a]` for the first impl trait and `'b` for the
         // second.
         let mut least_region = None;
-        for region_def in abstract_type_generics.params.iter().filter_map(|param| {
-            if let GenericParamDef::Lifetime(lt) = param {
-                Some(lt)
+        for index in abstract_type_generics.params.iter().filter_map(|param| {
+            if let GenericParamDefKind::Lifetime(_) = param.kind {
+                // Find the index of this region in the list of substitutions.
+                Some(param.index as usize)
             } else {
                 None
             }
         }) {
-            // Find the index of this region in the list of substitutions.
-            let index = region_def.index as usize;
-
             // Get the value supplied for this region from the substs.
             let subst_arg = anon_defn.substs.region_at(index);
 
diff --git a/src/librustc/infer/mod.rs b/src/librustc/infer/mod.rs
index a594231441a..8dd661d0403 100644
--- a/src/librustc/infer/mod.rs
+++ b/src/librustc/infer/mod.rs
@@ -909,7 +909,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     /// region parameter definition.
     pub fn region_var_for_def(&self,
                               span: Span,
-                              def: &ty::RegionParamDef)
+                              def: &ty::GenericParamDef)
                               -> ty::Region<'tcx> {
         self.next_region_var(EarlyBoundRegion(span, def.name))
     }
@@ -924,7 +924,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     /// as the substitutions for the default, `(T, U)`.
     pub fn type_var_for_def(&self,
                             span: Span,
-                            def: &ty::TypeParamDef)
+                            def: &ty::GenericParamDef)
                             -> Ty<'tcx> {
         let ty_var_id = self.type_variables
                             .borrow_mut()
diff --git a/src/librustc/middle/resolve_lifetime.rs b/src/librustc/middle/resolve_lifetime.rs
index a45e2f98310..bed5ee91800 100644
--- a/src/librustc/middle/resolve_lifetime.rs
+++ b/src/librustc/middle/resolve_lifetime.rs
@@ -20,7 +20,7 @@ use hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
 use hir::map::Map;
 use hir::ItemLocalId;
 use hir::LifetimeName;
-use ty::{self, TyCtxt, GenericParamDef};
+use ty::{self, TyCtxt, GenericParamDefKind};
 
 use errors::DiagnosticBuilder;
 use rustc::lint;
@@ -1662,9 +1662,11 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                             .params
                             .iter()
                             .filter_map(|param| {
-                                match *param {
-                                    GenericParamDef::Type(ty) => Some(ty.object_lifetime_default),
-                                    GenericParamDef::Lifetime(_) => None,
+                                match param.kind {
+                                    GenericParamDefKind::Type(ty) => {
+                                        Some(ty.object_lifetime_default)
+                                    }
+                                    GenericParamDefKind::Lifetime(_) => None,
                                 }
                             })
                             .collect()
diff --git a/src/librustc/traits/error_reporting.rs b/src/librustc/traits/error_reporting.rs
index ccaecdafa01..2f0691d241e 100644
--- a/src/librustc/traits/error_reporting.rs
+++ b/src/librustc/traits/error_reporting.rs
@@ -35,7 +35,8 @@ use infer::type_variable::TypeVariableOrigin;
 use std::fmt;
 use syntax::ast;
 use session::DiagnosticMessageId;
-use ty::{self, AdtKind, ToPredicate, ToPolyTraitRef, Ty, TyCtxt, TypeFoldable, GenericParamDef};
+use ty::{self, AdtKind, ToPredicate, ToPolyTraitRef, Ty, TyCtxt, TypeFoldable};
+use ty::GenericParamDefKind;
 use ty::error::ExpectedFound;
 use ty::fast_reject;
 use ty::fold::TypeFolder;
@@ -378,10 +379,10 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
             flags.push(("_Self".to_string(), Some(self.tcx.type_of(def.did).to_string())));
         }
 
-        for param in generics.params.iter().filter_map(|param| {
-            match *param {
-                GenericParamDef::Type(ty) => Some(ty),
-                GenericParamDef::Lifetime(_) => None,
+        for param in generics.params.iter().filter(|param| {
+            match param.kind {
+                GenericParamDefKind::Type(_) => true,
+                GenericParamDefKind::Lifetime(_) => false,
             }
         }) {
             let name = param.name.to_string();
diff --git a/src/librustc/traits/on_unimplemented.rs b/src/librustc/traits/on_unimplemented.rs
index c84e03e35f4..e15542cb2c0 100644
--- a/src/librustc/traits/on_unimplemented.rs
+++ b/src/librustc/traits/on_unimplemented.rs
@@ -11,7 +11,7 @@
 use fmt_macros::{Parser, Piece, Position};
 
 use hir::def_id::DefId;
-use ty::{self, TyCtxt, GenericParamDef};
+use ty::{self, TyCtxt, GenericParamDefKind};
 use util::common::ErrorReported;
 use util::nodemap::FxHashMap;
 
@@ -254,9 +254,9 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedFormatString {
                     Position::ArgumentNamed(s) if s == name => (),
                     // So is `{A}` if A is a type parameter
                     Position::ArgumentNamed(s) => match generics.params.iter().find(|param| {
-                        match *param {
-                            GenericParamDef::Type(ty) => ty.name == s,
-                            GenericParamDef::Lifetime(_) => false,
+                        match param.kind {
+                            GenericParamDefKind::Type(_) => param.name == s,
+                            GenericParamDefKind::Lifetime(_) => false,
                         }
                     }) {
                         Some(_) => (),
@@ -291,11 +291,12 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedFormatString {
         let trait_str = tcx.item_path_str(trait_ref.def_id);
         let generics = tcx.generics_of(trait_ref.def_id);
         let generic_map = generics.params.iter().filter_map(|param| {
-            match *param {
-                GenericParamDef::Type(ty) => {
-                    Some((ty.name.to_string(), trait_ref.substs.type_for_def(&ty).to_string()))
+            match param.kind {
+                GenericParamDefKind::Type(_) => {
+                    Some((param.name.to_string(),
+                         trait_ref.substs.type_for_def(&param).to_string()))
                 },
-                GenericParamDef::Lifetime(_) => None
+                GenericParamDefKind::Lifetime(_) => None
             }
         }).collect::<FxHashMap<String, String>>();
 
diff --git a/src/librustc/traits/util.rs b/src/librustc/traits/util.rs
index 3c62f04afc5..f5a9d2a7f00 100644
--- a/src/librustc/traits/util.rs
+++ b/src/librustc/traits/util.rs
@@ -213,7 +213,7 @@ impl<'cx, 'gcx, 'tcx> Elaborator<'cx, 'gcx, 'tcx> {
                            },
 
                            Component::Param(p) => {
-                               let ty = tcx.mk_param(p.idx, p.name);
+                               let ty = tcx.mk_ty_param(p.idx, p.name);
                                Some(ty::Predicate::TypeOutlives(
                                    ty::Binder::dummy(ty::OutlivesPredicate(ty, r_min))))
                            },
diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index 7391d187252..6eb85cfb307 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -2457,18 +2457,18 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         self.mk_ty(TyInfer(it))
     }
 
-    pub fn mk_param(self,
+    pub fn mk_ty_param(self,
                     index: u32,
                     name: InternedString) -> Ty<'tcx> {
         self.mk_ty(TyParam(ParamTy { idx: index, name: name }))
     }
 
     pub fn mk_self_type(self) -> Ty<'tcx> {
-        self.mk_param(0, keywords::SelfType.name().as_interned_str())
+        self.mk_ty_param(0, keywords::SelfType.name().as_interned_str())
     }
 
-    pub fn mk_param_from_def(self, def: &ty::TypeParamDef) -> Ty<'tcx> {
-        self.mk_param(def.index, def.name)
+    pub fn mk_ty_param_from_def(self, def: &ty::GenericParamDef) -> Ty<'tcx> {
+        self.mk_ty_param(def.index, def.name)
     }
 
     pub fn mk_anon(self, def_id: DefId, substs: &'tcx Substs<'tcx>) -> Ty<'tcx> {
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 37a6533fb61..3c4c326578a 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -709,11 +709,8 @@ pub enum IntVarValue {
 #[derive(Clone, Copy, PartialEq, Eq)]
 pub struct FloatVarValue(pub ast::FloatTy);
 
-#[derive(Copy, Clone, RustcEncodable, RustcDecodable)]
+#[derive(Copy, Clone, Debug, RustcEncodable, RustcDecodable)]
 pub struct TypeParamDef {
-    pub name: InternedString,
-    pub def_id: DefId,
-    pub index: u32,
     pub has_default: bool,
     pub object_lifetime_default: ObjectLifetimeDefault,
 
@@ -725,32 +722,14 @@ pub struct TypeParamDef {
     pub synthetic: Option<hir::SyntheticTyParamKind>,
 }
 
-#[derive(Copy, Clone, RustcEncodable, RustcDecodable)]
+#[derive(Copy, Clone, Debug, RustcEncodable, RustcDecodable)]
 pub struct RegionParamDef {
-    pub name: InternedString,
-    pub def_id: DefId,
-    pub index: u32,
-
     /// `pure_wrt_drop`, set by the (unsafe) `#[may_dangle]` attribute
     /// on generic parameter `'a`, asserts data of lifetime `'a`
     /// won't be accessed during the parent type's `Drop` impl.
     pub pure_wrt_drop: bool,
 }
 
-impl RegionParamDef {
-    pub fn to_early_bound_region_data(&self) -> ty::EarlyBoundRegion {
-        ty::EarlyBoundRegion {
-            def_id: self.def_id,
-            index: self.index,
-            name: self.name,
-        }
-    }
-
-    pub fn to_bound_region(&self) -> ty::BoundRegion {
-        self.to_early_bound_region_data().to_bound_region()
-    }
-}
-
 impl ty::EarlyBoundRegion {
     pub fn to_bound_region(&self) -> ty::BoundRegion {
         ty::BoundRegion::BrNamed(self.def_id, self.name)
@@ -758,23 +737,53 @@ impl ty::EarlyBoundRegion {
 }
 
 #[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
-pub enum GenericParamDef {
+pub enum GenericParamDefKind {
     Lifetime(RegionParamDef),
     Type(TypeParamDef),
 }
 
+#[derive(Clone, RustcEncodable, RustcDecodable)]
+pub struct GenericParamDef {
+    pub name: InternedString,
+    pub def_id: DefId,
+    pub index: u32,
+    pub kind: GenericParamDefKind,
+}
+
 impl GenericParamDef {
-    pub fn index(&self) -> u32 {
-        match self {
-            GenericParamDef::Lifetime(lt) => lt.index,
-            GenericParamDef::Type(ty) => ty.index,
+    pub fn to_lifetime(&self) -> RegionParamDef {
+        match self.kind {
+            GenericParamDefKind::Lifetime(lt) => lt,
+            _ => bug!("cannot convert a non-lifetime to a lifetime")
         }
     }
 
-    pub fn def_id(&self) -> DefId {
-        match self {
-            GenericParamDef::Lifetime(lt) => lt.def_id,
-            GenericParamDef::Type(ty) => ty.def_id,
+    pub fn to_type(&self) -> TypeParamDef {
+        match self.kind {
+            GenericParamDefKind::Type(ty) => ty,
+            _ => bug!("cannot convert a non-type to a type")
+        }
+    }
+
+    pub fn to_early_bound_region_data(&self) -> ty::EarlyBoundRegion {
+        match self.kind {
+            GenericParamDefKind::Lifetime(_) => {
+                ty::EarlyBoundRegion {
+                    def_id: self.def_id,
+                    index: self.index,
+                    name: self.name,
+                }
+            }
+            _ => bug!("cannot convert a non-lifetime parameter def to an early bound region")
+        }
+    }
+
+    pub fn to_bound_region(&self) -> ty::BoundRegion {
+        match self.kind {
+            GenericParamDefKind::Lifetime(_) => {
+                self.to_early_bound_region_data().to_bound_region()
+            }
+            _ => bug!("cannot convert a non-lifetime parameter def to an early bound region")
         }
     }
 }
@@ -817,9 +826,9 @@ impl<'a, 'gcx, 'tcx> Generics {
         };
 
         for param in self.params.iter() {
-            match param {
-                GenericParamDef::Lifetime(_) => param_counts.lifetimes += 1,
-                GenericParamDef::Type(_) => param_counts.types += 1,
+            match param.kind {
+                GenericParamDefKind::Lifetime(_) => param_counts.lifetimes += 1,
+                GenericParamDefKind::Type(_) => param_counts.types += 1,
             };
         }
 
@@ -828,9 +837,9 @@ impl<'a, 'gcx, 'tcx> Generics {
 
     pub fn requires_monomorphization(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> bool {
         if self.params.iter().any(|param| {
-            match *param {
-                GenericParamDef::Type(_) => true,
-                GenericParamDef::Lifetime(_) => false
+            match param.kind {
+                GenericParamDefKind::Type(_) => true,
+                GenericParamDefKind::Lifetime(_) => false
             }
         }) {
             return true;
@@ -846,11 +855,12 @@ impl<'a, 'gcx, 'tcx> Generics {
     pub fn region_param(&'tcx self,
                         param: &EarlyBoundRegion,
                         tcx: TyCtxt<'a, 'gcx, 'tcx>)
-                        -> &'tcx RegionParamDef
+                        -> &'tcx GenericParamDef
     {
         if let Some(index) = param.index.checked_sub(self.parent_count as u32) {
-            match self.params[index as usize] {
-                ty::GenericParamDef::Lifetime(ref lt) => lt,
+            let ref param = self.params[index as usize];
+            match param.kind {
+                ty::GenericParamDefKind::Lifetime(_) => param,
                 _ => bug!("expected region parameter, but found another generic parameter")
             }
         } else {
@@ -863,7 +873,7 @@ impl<'a, 'gcx, 'tcx> Generics {
     pub fn type_param(&'tcx self,
                       param: &ParamTy,
                       tcx: TyCtxt<'a, 'gcx, 'tcx>)
-                      -> &TypeParamDef {
+                      -> &'tcx GenericParamDef {
         if let Some(index) = param.idx.checked_sub(self.parent_count as u32) {
             // non-Self type parameters are always offset by exactly
             // `self.regions.len()`. In the absence of a Self, this is obvious,
@@ -899,14 +909,16 @@ impl<'a, 'gcx, 'tcx> Generics {
 
             if let Some(_) = (index as usize).checked_sub(type_param_offset) {
                 assert!(!is_separated_self, "found a Self after type_param_offset");
-                match self.params[index as usize] {
-                    ty::GenericParamDef::Type(ref ty) => ty,
+                let ref param = self.params[index as usize];
+                match param.kind {
+                    ty::GenericParamDefKind::Type(_) => param,
                     _ => bug!("expected type parameter, but found another generic parameter")
                 }
             } else {
                 assert!(is_separated_self, "non-Self param before type_param_offset");
-                match self.params[type_param_offset] {
-                    ty::GenericParamDef::Type(ref ty) => ty,
+                let ref param = self.params[type_param_offset];
+                match param.kind {
+                    ty::GenericParamDefKind::Type(_) => param,
                     _ => bug!("expected type parameter, but found another generic parameter")
                 }
             }
diff --git a/src/librustc/ty/sty.rs b/src/librustc/ty/sty.rs
index 01ebf3666f9..792a6bfaedf 100644
--- a/src/librustc/ty/sty.rs
+++ b/src/librustc/ty/sty.rs
@@ -928,12 +928,12 @@ impl<'a, 'gcx, 'tcx> ParamTy {
         ParamTy::new(0, keywords::SelfType.name().as_interned_str())
     }
 
-    pub fn for_def(def: &ty::TypeParamDef) -> ParamTy {
+    pub fn for_def(def: &ty::GenericParamDef) -> ParamTy {
         ParamTy::new(def.index, def.name)
     }
 
     pub fn to_ty(self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
-        tcx.mk_param(self.idx, self.name)
+        tcx.mk_ty_param(self.idx, self.name)
     }
 
     pub fn is_self(&self) -> bool {
diff --git a/src/librustc/ty/subst.rs b/src/librustc/ty/subst.rs
index 4f69776721e..a14045b43f2 100644
--- a/src/librustc/ty/subst.rs
+++ b/src/librustc/ty/subst.rs
@@ -183,7 +183,7 @@ impl<'a, 'gcx, 'tcx> Substs<'tcx> {
                              -> &'tcx Substs<'tcx> {
         Substs::for_item(tcx, def_id, |def, _| {
             tcx.mk_region(ty::ReEarlyBound(def.to_early_bound_region_data()))
-        }, |def, _| tcx.mk_param_from_def(def))
+        }, |def, _| tcx.mk_ty_param_from_def(def))
     }
 
     /// Creates a Substs for generic parameter definitions,
@@ -196,8 +196,8 @@ impl<'a, 'gcx, 'tcx> Substs<'tcx> {
                             mut mk_region: FR,
                             mut mk_type: FT)
                             -> &'tcx Substs<'tcx>
-    where FR: FnMut(&ty::RegionParamDef, &[Kind<'tcx>]) -> ty::Region<'tcx>,
-          FT: FnMut(&ty::TypeParamDef, &[Kind<'tcx>]) -> Ty<'tcx> {
+    where FR: FnMut(&ty::GenericParamDef, &[Kind<'tcx>]) -> ty::Region<'tcx>,
+          FT: FnMut(&ty::GenericParamDef, &[Kind<'tcx>]) -> Ty<'tcx> {
         let defs = tcx.generics_of(def_id);
         let mut substs = Vec::with_capacity(defs.count());
         Substs::fill_item(&mut substs, tcx, defs, &mut mk_region, &mut mk_type);
@@ -210,8 +210,8 @@ impl<'a, 'gcx, 'tcx> Substs<'tcx> {
                              mut mk_region: FR,
                              mut mk_type: FT)
                              -> &'tcx Substs<'tcx>
-    where FR: FnMut(&ty::RegionParamDef, &[Kind<'tcx>]) -> ty::Region<'tcx>,
-          FT: FnMut(&ty::TypeParamDef, &[Kind<'tcx>]) -> Ty<'tcx>
+    where FR: FnMut(&ty::GenericParamDef, &[Kind<'tcx>]) -> ty::Region<'tcx>,
+          FT: FnMut(&ty::GenericParamDef, &[Kind<'tcx>]) -> Ty<'tcx>
     {
         let defs = tcx.generics_of(def_id);
         let mut result = Vec::with_capacity(defs.count());
@@ -225,8 +225,8 @@ impl<'a, 'gcx, 'tcx> Substs<'tcx> {
                              defs: &ty::Generics,
                              mk_region: &mut FR,
                              mk_type: &mut FT)
-    where FR: FnMut(&ty::RegionParamDef, &[Kind<'tcx>]) -> ty::Region<'tcx>,
-          FT: FnMut(&ty::TypeParamDef, &[Kind<'tcx>]) -> Ty<'tcx> {
+    where FR: FnMut(&ty::GenericParamDef, &[Kind<'tcx>]) -> ty::Region<'tcx>,
+          FT: FnMut(&ty::GenericParamDef, &[Kind<'tcx>]) -> Ty<'tcx> {
 
         if let Some(def_id) = defs.parent {
             let parent_defs = tcx.generics_of(def_id);
@@ -239,15 +239,15 @@ impl<'a, 'gcx, 'tcx> Substs<'tcx> {
                            defs: &ty::Generics,
                            mk_region: &mut FR,
                            mk_type: &mut FT)
-    where FR: FnMut(&ty::RegionParamDef, &[Kind<'tcx>]) -> ty::Region<'tcx>,
-          FT: FnMut(&ty::TypeParamDef, &[Kind<'tcx>]) -> Ty<'tcx> {
-        for def in &defs.params {
-            let param = match def {
-                ty::GenericParamDef::Lifetime(ref lt) => mk_region(lt, substs).into(),
-                ty::GenericParamDef::Type(ref ty) => mk_type(ty, substs).into(),
+    where FR: FnMut(&ty::GenericParamDef, &[Kind<'tcx>]) -> ty::Region<'tcx>,
+          FT: FnMut(&ty::GenericParamDef, &[Kind<'tcx>]) -> Ty<'tcx> {
+        for param in &defs.params {
+            let kind = match param.kind {
+                ty::GenericParamDefKind::Lifetime(_) => mk_region(param, substs).into(),
+                ty::GenericParamDefKind::Type(_) => mk_type(param, substs).into(),
             };
-            assert_eq!(def.index() as usize, substs.len());
-            substs.push(param);
+            assert_eq!(param.index as usize, substs.len());
+            substs.push(kind);
         }
     }
 
@@ -296,12 +296,12 @@ impl<'a, 'gcx, 'tcx> Substs<'tcx> {
     }
 
     #[inline]
-    pub fn type_for_def(&self, ty_param_def: &ty::TypeParamDef) -> Ty<'tcx> {
+    pub fn type_for_def(&self, ty_param_def: &ty::GenericParamDef) -> Ty<'tcx> {
         self.type_at(ty_param_def.index as usize)
     }
 
     #[inline]
-    pub fn region_for_def(&self, def: &ty::RegionParamDef) -> ty::Region<'tcx> {
+    pub fn region_for_def(&self, def: &ty::GenericParamDef) -> ty::Region<'tcx> {
         self.region_at(def.index as usize)
     }
 
diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs
index fdd0754730f..db11f465972 100644
--- a/src/librustc/ty/util.rs
+++ b/src/librustc/ty/util.rs
@@ -505,12 +505,12 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             .filter(|&(_, &k)| {
                 match k.unpack() {
                     UnpackedKind::Lifetime(&ty::RegionKind::ReEarlyBound(ref ebr)) => {
-                        !impl_generics.region_param(ebr, self).pure_wrt_drop
+                        !impl_generics.region_param(ebr, self).to_lifetime().pure_wrt_drop
                     }
                     UnpackedKind::Type(&ty::TyS {
                         sty: ty::TypeVariants::TyParam(ref pt), ..
                     }) => {
-                        !impl_generics.type_param(pt, self).pure_wrt_drop
+                        !impl_generics.type_param(pt, self).to_type().pure_wrt_drop
                     }
                     UnpackedKind::Lifetime(_) | UnpackedKind::Type(_) => {
                         // not a type or region param - this should be reported
diff --git a/src/librustc/util/ppaux.rs b/src/librustc/util/ppaux.rs
index 603e6e03246..47315c7243f 100644
--- a/src/librustc/util/ppaux.rs
+++ b/src/librustc/util/ppaux.rs
@@ -19,7 +19,7 @@ use ty::{TyError, TyStr, TyArray, TySlice, TyFloat, TyFnDef, TyFnPtr};
 use ty::{TyParam, TyRawPtr, TyRef, TyNever, TyTuple};
 use ty::{TyClosure, TyGenerator, TyGeneratorWitness, TyForeign, TyProjection, TyAnon};
 use ty::{TyDynamic, TyInt, TyUint, TyInfer};
-use ty::{self, Ty, TyCtxt, TypeFoldable, GenericParamCount, GenericParamDef};
+use ty::{self, Ty, TyCtxt, TypeFoldable, GenericParamCount, GenericParamDefKind};
 use util::nodemap::FxHashSet;
 
 use std::cell::Cell;
@@ -338,20 +338,21 @@ impl PrintContext {
             if !verbose {
                 let mut type_params =
                     generics.params.iter().rev().filter_map(|param| {
-                        match *param {
-                            GenericParamDef::Type(ty) => Some(ty),
-                            GenericParamDef::Lifetime(_) => None,
+                        match param.kind {
+                            GenericParamDefKind::Type(ty) => Some((param.def_id, ty.has_default)),
+                            GenericParamDefKind::Lifetime(_) => None,
                         }
                     });
                 if let Some(last_ty) = type_params.next() {
-                    if last_ty.has_default {
+                    let (_, has_default) = last_ty;
+                    if has_default {
                         if let Some(substs) = tcx.lift(&substs) {
-                            let mut tps = substs.types().rev().skip(child_types);
-                            let zipped = iter::once((last_ty, tps.next().unwrap()))
-                                              .chain(type_params.zip(tps));
-                            for (ty, actual) in zipped {
-                                if !ty.has_default ||
-                                        tcx.type_of(ty.def_id).subst(tcx, substs) != actual {
+                            let mut types = substs.types().rev().skip(child_types);
+                            let zipped = iter::once((last_ty, types.next().unwrap()))
+                                              .chain(type_params.zip(types));
+                            for ((def_id, has_default), actual) in zipped {
+                                if !has_default ||
+                                        tcx.type_of(def_id).subst(tcx, substs) != actual {
                                     break;
                                 }
                                 num_supplied_defaults += 1;
@@ -600,18 +601,14 @@ define_print! {
     }
 }
 
-impl fmt::Debug for ty::TypeParamDef {
+impl fmt::Debug for ty::GenericParamDef {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "TypeParamDef({}, {:?}, {})",
-               self.name,
-               self.def_id,
-               self.index)
-    }
-}
-
-impl fmt::Debug for ty::RegionParamDef {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "RegionParamDef({}, {:?}, {})",
+        let type_name = match self.kind {
+            ty::GenericParamDefKind::Lifetime(_) => "Region",
+            ty::GenericParamDefKind::Type(_) => "Type",
+        };
+        write!(f, "{}({}, {:?}, {})",
+               type_name,
                self.name,
                self.def_id,
                self.index)
diff --git a/src/librustc_driver/test.rs b/src/librustc_driver/test.rs
index 7ae26e9e979..78c95a5ce05 100644
--- a/src/librustc_driver/test.rs
+++ b/src/librustc_driver/test.rs
@@ -308,7 +308,7 @@ impl<'a, 'gcx, 'tcx> Env<'a, 'gcx, 'tcx> {
 
     pub fn t_param(&self, index: u32) -> Ty<'tcx> {
         let name = format!("T{}", index);
-        self.infcx.tcx.mk_param(index, Symbol::intern(&name).as_interned_str())
+        self.infcx.tcx.mk_ty_param(index, Symbol::intern(&name).as_interned_str())
     }
 
     pub fn re_early_bound(&self, index: u32, name: &'static str) -> ty::Region<'tcx> {
diff --git a/src/librustc_privacy/lib.rs b/src/librustc_privacy/lib.rs
index 56ffadc882a..1b2ec481a1c 100644
--- a/src/librustc_privacy/lib.rs
+++ b/src/librustc_privacy/lib.rs
@@ -27,7 +27,7 @@ use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
 use rustc::hir::itemlikevisit::DeepVisitor;
 use rustc::lint;
 use rustc::middle::privacy::{AccessLevel, AccessLevels};
-use rustc::ty::{self, TyCtxt, Ty, TypeFoldable, GenericParamDef};
+use rustc::ty::{self, TyCtxt, Ty, TypeFoldable, GenericParamDefKind};
 use rustc::ty::fold::TypeVisitor;
 use rustc::ty::maps::Providers;
 use rustc::ty::subst::UnpackedKind;
@@ -399,14 +399,14 @@ impl<'a, 'tcx> Visitor<'tcx> for EmbargoVisitor<'a, 'tcx> {
 
 impl<'b, 'a, 'tcx> ReachEverythingInTheInterfaceVisitor<'b, 'a, 'tcx> {
     fn generics(&mut self) -> &mut Self {
-        for def in self.ev.tcx.generics_of(self.item_def_id).params.iter() {
-            match def {
-                GenericParamDef::Type(ty) => {
+        for param in self.ev.tcx.generics_of(self.item_def_id).params.iter() {
+            match param.kind {
+                GenericParamDefKind::Type(ty) => {
                     if ty.has_default {
-                        self.ev.tcx.type_of(ty.def_id).visit_with(self);
+                        self.ev.tcx.type_of(param.def_id).visit_with(self);
                     }
                 }
-                GenericParamDef::Lifetime(_) => {}
+                GenericParamDefKind::Lifetime(_) => {}
             }
         }
         self
@@ -1340,14 +1340,14 @@ struct SearchInterfaceForPrivateItemsVisitor<'a, 'tcx: 'a> {
 
 impl<'a, 'tcx: 'a> SearchInterfaceForPrivateItemsVisitor<'a, 'tcx> {
     fn generics(&mut self) -> &mut Self {
-        for def in self.tcx.generics_of(self.item_def_id).params.iter() {
-            match def {
-                GenericParamDef::Type(ty) => {
+        for param in self.tcx.generics_of(self.item_def_id).params.iter() {
+            match param.kind {
+                GenericParamDefKind::Type(ty) => {
                     if ty.has_default {
-                        self.tcx.type_of(ty.def_id).visit_with(self);
+                        self.tcx.type_of(param.def_id).visit_with(self);
                     }
                 }
-                GenericParamDef::Lifetime(_) => {}
+                GenericParamDefKind::Lifetime(_) => {}
             }
         }
         self
diff --git a/src/librustc_traits/dropck_outlives.rs b/src/librustc_traits/dropck_outlives.rs
index da38081a602..6c2128de272 100644
--- a/src/librustc_traits/dropck_outlives.rs
+++ b/src/librustc_traits/dropck_outlives.rs
@@ -13,7 +13,7 @@ use rustc::hir::def_id::DefId;
 use rustc::traits::{FulfillmentContext, Normalized, ObligationCause};
 use rustc::traits::query::{CanonicalTyGoal, NoSolution};
 use rustc::traits::query::dropck_outlives::{DtorckConstraint, DropckOutlivesResult};
-use rustc::ty::{self, ParamEnvAnd, Ty, TyCtxt, GenericParamDef};
+use rustc::ty::{self, ParamEnvAnd, Ty, TyCtxt};
 use rustc::ty::subst::Subst;
 use rustc::util::nodemap::FxHashSet;
 use rustc_data_structures::sync::Lrc;
@@ -278,13 +278,11 @@ crate fn adt_dtorck_constraint<'a, 'tcx>(
     debug!("dtorck_constraint: {:?}", def);
 
     if def.is_phantom_data() {
-        let type_param = match tcx.generics_of(def_id).params[0] {
-            GenericParamDef::Type(ty) => ty,
-            GenericParamDef::Lifetime(_) => unreachable!(),
-        };
+        // The first generic parameter here is guaranteed to be a type because it's `PhantomData`.
+        let param = &tcx.generics_of(def_id).params[0];
         let result = DtorckConstraint {
             outlives: vec![],
-            dtorck_types: vec![tcx.mk_param_from_def(&type_param)],
+            dtorck_types: vec![tcx.mk_ty_param_from_def(param)],
             overflows: vec![],
         };
         debug!("dtorck_constraint: {:?} => {:?}", def, result);
diff --git a/src/librustc_trans/debuginfo/mod.rs b/src/librustc_trans/debuginfo/mod.rs
index 31ef1eddfcb..2039a90a043 100644
--- a/src/librustc_trans/debuginfo/mod.rs
+++ b/src/librustc_trans/debuginfo/mod.rs
@@ -26,7 +26,6 @@ use llvm::debuginfo::{DIFile, DIType, DIScope, DIBuilderRef, DISubprogram, DIArr
 use rustc::hir::TransFnAttrFlags;
 use rustc::hir::def_id::{DefId, CrateNum};
 use rustc::ty::subst::{Substs, UnpackedKind};
-use rustc::ty::GenericParamDef;
 
 use abi::Abi;
 use common::CodegenCx;
@@ -425,12 +424,7 @@ pub fn create_function_debug_context<'a, 'tcx>(cx: &CodegenCx<'a, 'tcx>,
         let mut names = generics.parent.map_or(vec![], |def_id| {
             get_parameter_names(cx, cx.tcx.generics_of(def_id))
         });
-        names.extend(generics.params.iter().map(|param| {
-            match param {
-                GenericParamDef::Lifetime(lt) => lt.name,
-                GenericParamDef::Type(ty) => ty.name,
-            }
-        }));
+        names.extend(generics.params.iter().map(|param| param.name));
         names
     }
 
diff --git a/src/librustc_typeck/astconv.rs b/src/librustc_typeck/astconv.rs
index 84d94539f74..3d77c9d39a5 100644
--- a/src/librustc_typeck/astconv.rs
+++ b/src/librustc_typeck/astconv.rs
@@ -43,7 +43,7 @@ pub trait AstConv<'gcx, 'tcx> {
                                  -> ty::GenericPredicates<'tcx>;
 
     /// What lifetime should we use when a lifetime is omitted (and not elided)?
-    fn re_infer(&self, span: Span, _def: Option<&ty::RegionParamDef>)
+    fn re_infer(&self, span: Span, _def: Option<&ty::GenericParamDef>)
                 -> Option<ty::Region<'tcx>>;
 
     /// What type should we use when a type is omitted?
@@ -51,7 +51,7 @@ pub trait AstConv<'gcx, 'tcx> {
 
     /// Same as ty_infer, but with a known type parameter definition.
     fn ty_infer_for_def(&self,
-                        _def: &ty::TypeParamDef,
+                        _def: &ty::GenericParamDef,
                         span: Span) -> Ty<'tcx> {
         self.ty_infer(span)
     }
@@ -95,7 +95,7 @@ const TRAIT_OBJECT_DUMMY_SELF: ty::TypeVariants<'static> = ty::TyInfer(ty::Fresh
 impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
     pub fn ast_region_to_region(&self,
         lifetime: &hir::Lifetime,
-        def: Option<&ty::RegionParamDef>)
+        def: Option<&ty::GenericParamDef>)
         -> ty::Region<'tcx>
     {
         let tcx = self.tcx();
@@ -228,7 +228,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
             let type_params_without_defaults = {
                 let mut count = 0;
                 for param in decl_generics.params.iter() {
-                    if let ty::GenericParamDef::Type(ty) = param {
+                    if let ty::GenericParamDefKind::Type(ty) = param.kind {
                         if !ty.has_default {
                             count += 1
                         }
@@ -245,9 +245,9 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
         }
 
         let is_object = self_ty.map_or(false, |ty| ty.sty == TRAIT_OBJECT_DUMMY_SELF);
-        let default_needs_object_self = |p: &ty::TypeParamDef| {
-            if is_object && p.has_default {
-                if tcx.at(span).type_of(p.def_id).has_self_ty() {
+        let default_needs_object_self = |param: &ty::GenericParamDef| {
+            if is_object && param.to_type().has_default {
+                if tcx.at(span).type_of(param.def_id).has_self_ty() {
                     // There is no suitable inference default for a type parameter
                     // that references self, in an object type.
                     return true;
@@ -284,7 +284,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
                     self.ty_infer(span)
                 };
                 ty_var
-            } else if def.has_default {
+            } else if def.to_type().has_default {
                 // No type parameter provided, but a default exists.
 
                 // If we are converting an object type, then the
@@ -998,7 +998,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
                 let item_def_id = tcx.hir.local_def_id(item_id);
                 let generics = tcx.generics_of(item_def_id);
                 let index = generics.param_def_id_to_index[&tcx.hir.local_def_id(node_id)];
-                tcx.mk_param(index, tcx.hir.name(node_id).as_interned_str())
+                tcx.mk_ty_param(index, tcx.hir.name(node_id).as_interned_str())
             }
             Def::SelfTy(_, Some(def_id)) => {
                 // Self in impl (we know the concrete type).
@@ -1146,7 +1146,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
                 &mut substs, tcx, parent_generics,
                 &mut |def, _| tcx.mk_region(
                     ty::ReEarlyBound(def.to_early_bound_region_data())),
-                &mut |def, _| tcx.mk_param_from_def(def)
+                &mut |def, _| tcx.mk_ty_param_from_def(def)
             );
 
             // Replace all lifetimes with 'static
diff --git a/src/librustc_typeck/check/compare_method.rs b/src/librustc_typeck/check/compare_method.rs
index d1978ceb30b..11f421da714 100644
--- a/src/librustc_typeck/check/compare_method.rs
+++ b/src/librustc_typeck/check/compare_method.rs
@@ -10,7 +10,7 @@
 
 use rustc::hir::{self, ImplItemKind, TraitItemKind};
 use rustc::infer::{self, InferOk};
-use rustc::ty::{self, TyCtxt, GenericParamDef};
+use rustc::ty::{self, TyCtxt, GenericParamDefKind};
 use rustc::ty::util::ExplicitSelf;
 use rustc::traits::{self, ObligationCause, ObligationCauseCode, Reveal};
 use rustc::ty::error::{ExpectedFound, TypeError};
@@ -729,19 +729,19 @@ fn compare_synthetic_generics<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let impl_m_generics = tcx.generics_of(impl_m.def_id);
     let trait_m_generics = tcx.generics_of(trait_m.def_id);
     let impl_m_type_params = impl_m_generics.params.iter().filter_map(|param| {
-        match *param {
-            GenericParamDef::Type(ty) => Some(ty),
-            GenericParamDef::Lifetime(_) => None,
+        match param.kind {
+            GenericParamDefKind::Type(_) => Some(param),
+            GenericParamDefKind::Lifetime(_) => None,
         }
     });
     let trait_m_type_params = trait_m_generics.params.iter().filter_map(|param| {
-        match *param {
-            GenericParamDef::Type(ty) => Some(ty),
-            GenericParamDef::Lifetime(_) => None,
+        match param.kind {
+            GenericParamDefKind::Type(_) => Some(param),
+            GenericParamDefKind::Lifetime(_) => None,
         }
     });
     for (impl_ty, trait_ty) in impl_m_type_params.zip(trait_m_type_params) {
-        if impl_ty.synthetic != trait_ty.synthetic {
+        if impl_ty.to_type().synthetic != trait_ty.to_type().synthetic {
             let impl_node_id = tcx.hir.as_local_node_id(impl_ty.def_id).unwrap();
             let impl_span = tcx.hir.span(impl_node_id);
             let trait_span = tcx.def_span(trait_ty.def_id);
diff --git a/src/librustc_typeck/check/intrinsic.rs b/src/librustc_typeck/check/intrinsic.rs
index 1817b4aba19..d852a865174 100644
--- a/src/librustc_typeck/check/intrinsic.rs
+++ b/src/librustc_typeck/check/intrinsic.rs
@@ -76,7 +76,7 @@ fn equate_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 /// and in libcore/intrinsics.rs
 pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                       it: &hir::ForeignItem) {
-    let param = |n| tcx.mk_param(n, Symbol::intern(&format!("P{}", n)).as_interned_str());
+    let param = |n| tcx.mk_ty_param(n, Symbol::intern(&format!("P{}", n)).as_interned_str());
     let name = it.name.as_str();
     let (n_tps, inputs, output) = if name.starts_with("atomic_") {
         let split : Vec<&str> = name.split('_').collect();
@@ -342,7 +342,7 @@ pub fn check_platform_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                                it: &hir::ForeignItem) {
     let param = |n| {
         let name = Symbol::intern(&format!("P{}", n)).as_interned_str();
-        tcx.mk_param(n, name)
+        tcx.mk_ty_param(n, name)
     };
 
     let def_id = tcx.hir.local_def_id(it.id);
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index f860c1358a6..e5dffeed560 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -1730,7 +1730,7 @@ impl<'a, 'gcx, 'tcx> AstConv<'gcx, 'tcx> for FnCtxt<'a, 'gcx, 'tcx> {
         }
     }
 
-    fn re_infer(&self, span: Span, def: Option<&ty::RegionParamDef>)
+    fn re_infer(&self, span: Span, def: Option<&ty::GenericParamDef>)
                 -> Option<ty::Region<'tcx>> {
         let v = match def {
             Some(def) => infer::EarlyBoundRegion(span, def.name),
@@ -1744,7 +1744,7 @@ impl<'a, 'gcx, 'tcx> AstConv<'gcx, 'tcx> for FnCtxt<'a, 'gcx, 'tcx> {
     }
 
     fn ty_infer_for_def(&self,
-                        ty_param_def: &ty::TypeParamDef,
+                        ty_param_def: &ty::GenericParamDef,
                         span: Span) -> Ty<'tcx> {
         self.type_var_for_def(span, ty_param_def)
     }
@@ -4805,7 +4805,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             if let Some(ast_ty) = types.get(i) {
                 // A provided type parameter.
                 self.to_ty(ast_ty)
-            } else if !infer_types && def.has_default {
+            } else if !infer_types && def.to_type().has_default {
                 // No type parameter provided, but a default exists.
                 let default = self.tcx.type_of(def.def_id);
                 self.normalize_ty(
@@ -4928,7 +4928,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                 let type_params_without_defaults = {
                     let mut count = 0;
                     for param in generics.params.iter() {
-                        if let ty::GenericParamDef::Type(ty) = param {
+                        if let ty::GenericParamDefKind::Type(ty) = param.kind {
                             if !ty.has_default {
                                 count += 1
                             }
@@ -5025,7 +5025,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         let segment = segment.map(|(path_segment, generics)| {
             let explicit = !path_segment.infer_types;
             let impl_trait = generics.params.iter().any(|param| {
-                if let ty::GenericParamDef::Type(ty) = param {
+                if let ty::GenericParamDefKind::Type(ty) = param.kind {
                     if let Some(hir::SyntheticTyParamKind::ImplTrait) = ty.synthetic {
                         return true;
                     }
diff --git a/src/librustc_typeck/check/wfcheck.rs b/src/librustc_typeck/check/wfcheck.rs
index 75380c685da..cc20a7c28d3 100644
--- a/src/librustc_typeck/check/wfcheck.rs
+++ b/src/librustc_typeck/check/wfcheck.rs
@@ -11,7 +11,7 @@
 use check::{Inherited, FnCtxt};
 use constrained_type_params::{identify_constrained_type_params, Parameter};
 
-use ty::GenericParamDef;
+use ty::GenericParamDefKind;
 
 use hir::def_id::DefId;
 use rustc::traits::{self, ObligationCauseCode};
@@ -370,8 +370,8 @@ fn check_where_clauses<'a, 'gcx, 'fcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'gcx>,
     let mut substituted_predicates = Vec::new();
 
     let generics = tcx.generics_of(def_id);
-    let is_our_default = |def: &ty::TypeParamDef| {
-        def.has_default && def.index >= generics.parent_count as u32
+    let is_our_default = |def: &ty::GenericParamDef| {
+        def.to_type().has_default && def.index >= generics.parent_count as u32
     };
 
     // Check that concrete defaults are well-formed. See test `type-check-defaults.rs`.
@@ -379,9 +379,9 @@ fn check_where_clauses<'a, 'gcx, 'fcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'gcx>,
     // struct Foo<T = Vec<[u32]>> { .. }
     // Here the default `Vec<[u32]>` is not WF because `[u32]: Sized` does not hold.
     for d in generics.params.iter().filter_map(|param| {
-        if let GenericParamDef::Type(ty) = *param {
-            if is_our_default(&ty) {
-                return Some(ty.def_id);
+        if let GenericParamDefKind::Type(_) = param.kind {
+            if is_our_default(&param) {
+                return Some(param.def_id);
             }
         }
         None
@@ -654,21 +654,18 @@ fn reject_shadowing_parameters(tcx: TyCtxt, def_id: DefId) {
     let impl_params: FxHashMap<_, _> =
         parent.params.iter()
                      .flat_map(|param| {
-                         match param {
-                             GenericParamDef::Lifetime(_) => None,
-                             GenericParamDef::Type(ty) => Some((ty.name, ty.def_id)),
+                         match param.kind {
+                             GenericParamDefKind::Lifetime(_) => None,
+                             GenericParamDefKind::Type(_) => Some((param.name, param.def_id)),
                          }
                      })
                      .collect();
 
     for method_param in generics.params.iter() {
-        // Shadowing is checked in resolve_lifetime.
-        if let GenericParamDef::Lifetime(_) = method_param {
-            continue;
-        }
-        let (name, def_id) = match method_param {
-            GenericParamDef::Lifetime(_) => continue,
-            GenericParamDef::Type(ty) => (ty.name, ty.def_id),
+        let (name, def_id) = match method_param.kind {
+            // Shadowing is checked in resolve_lifetime.
+            GenericParamDefKind::Lifetime(_) => continue,
+            GenericParamDefKind::Type(_) => (method_param.name, method_param.def_id),
         };
         if impl_params.contains_key(&name) {
             // Tighten up the span to focus on only the shadowing type
diff --git a/src/librustc_typeck/collect.rs b/src/librustc_typeck/collect.rs
index b8c78c7b36a..d41f7e60727 100644
--- a/src/librustc_typeck/collect.rs
+++ b/src/librustc_typeck/collect.rs
@@ -181,7 +181,7 @@ impl<'a, 'tcx> AstConv<'tcx, 'tcx> for ItemCtxt<'a, 'tcx> {
         self.tcx.at(span).type_param_predicates((self.item_def_id, def_id))
     }
 
-    fn re_infer(&self, _span: Span, _def: Option<&ty::RegionParamDef>)
+    fn re_infer(&self, _span: Span, _def: Option<&ty::GenericParamDef>)
                 -> Option<ty::Region<'tcx>> {
         None
     }
@@ -244,7 +244,7 @@ fn type_param_predicates<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let param_owner_def_id = tcx.hir.local_def_id(param_owner);
     let generics = tcx.generics_of(param_owner_def_id);
     let index = generics.param_def_id_to_index[&def_id];
-    let ty = tcx.mk_param(index, tcx.hir.ty_param_name(param_id).as_interned_str());
+    let ty = tcx.mk_ty_param(index, tcx.hir.ty_param_name(param_id).as_interned_str());
 
     // Don't look for bounds where the type parameter isn't in scope.
     let parent = if item_def_id == param_owner_def_id {
@@ -840,14 +840,16 @@ fn generics_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                     // the node id for the Self type parameter.
                     let param_id = item.id;
 
-                    opt_self = Some(ty::TypeParamDef {
+                    opt_self = Some(ty::GenericParamDef {
                         index: 0,
                         name: keywords::SelfType.name().as_interned_str(),
                         def_id: tcx.hir.local_def_id(param_id),
-                        has_default: false,
-                        object_lifetime_default: rl::Set1::Empty,
-                        pure_wrt_drop: false,
-                        synthetic: None,
+                        kind: ty::GenericParamDefKind::Type(ty::TypeParamDef {
+                            has_default: false,
+                            object_lifetime_default: rl::Set1::Empty,
+                            pure_wrt_drop: false,
+                            synthetic: None,
+                        }),
                     });
 
                     allow_defaults = true;
@@ -885,12 +887,14 @@ fn generics_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     });
 
     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
-    let regions = early_lifetimes.enumerate().map(|(i, l)| {
-        ty::RegionParamDef {
+    let lifetimes = early_lifetimes.enumerate().map(|(i, l)| {
+        ty::GenericParamDef {
             name: l.lifetime.name.name().as_interned_str(),
             index: own_start + i as u32,
             def_id: tcx.hir.local_def_id(l.lifetime.id),
-            pure_wrt_drop: l.pure_wrt_drop,
+            kind: ty::GenericParamDefKind::Lifetime(ty::RegionParamDef {
+                pure_wrt_drop: l.pure_wrt_drop,
+            }),
         }
     }).collect::<Vec<_>>();
 
@@ -898,7 +902,7 @@ fn generics_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
 
     // Now create the real type parameters.
-    let type_start = own_start + regions.len() as u32;
+    let type_start = own_start + lifetimes.len() as u32;
     let types = ast_generics.ty_params().enumerate().map(|(i, p)| {
         if p.name == keywords::SelfType.name() {
             span_bug!(p.span, "`Self` should not be the name of a regular parameter");
@@ -915,15 +919,17 @@ fn generics_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             }
         }
 
-        ty::TypeParamDef {
+        ty::GenericParamDef {
             index: type_start + i as u32,
             name: p.name.as_interned_str(),
             def_id: tcx.hir.local_def_id(p.id),
-            has_default: p.default.is_some(),
-            object_lifetime_default:
-                object_lifetime_defaults.as_ref().map_or(rl::Set1::Empty, |o| o[i]),
-            pure_wrt_drop: p.pure_wrt_drop,
-            synthetic: p.synthetic,
+            kind: ty::GenericParamDefKind::Type(ty::TypeParamDef {
+                has_default: p.default.is_some(),
+                object_lifetime_default:
+                    object_lifetime_defaults.as_ref().map_or(rl::Set1::Empty, |o| o[i]),
+                pure_wrt_drop: p.pure_wrt_drop,
+                synthetic: p.synthetic,
+            }),
         }
     });
 
@@ -940,41 +946,43 @@ fn generics_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         };
 
         for (i, &arg) in dummy_args.iter().enumerate() {
-            types.push(ty::TypeParamDef {
+            types.push(ty::GenericParamDef {
                 index: type_start + i as u32,
                 name: Symbol::intern(arg).as_interned_str(),
                 def_id,
-                has_default: false,
-                object_lifetime_default: rl::Set1::Empty,
-                pure_wrt_drop: false,
-                synthetic: None,
+                kind: ty::GenericParamDefKind::Type(ty::TypeParamDef {
+                    has_default: false,
+                    object_lifetime_default: rl::Set1::Empty,
+                    pure_wrt_drop: false,
+                    synthetic: None,
+                }),
             });
         }
 
         tcx.with_freevars(node_id, |fv| {
             types.extend(fv.iter().zip((dummy_args.len() as u32)..).map(|(_, i)| {
-                ty::TypeParameterDef {
+                ty::GenericParamDef {
                     index: type_start + i,
                     name: Symbol::intern("<upvar>").as_interned_str(),
                     def_id,
-                    has_default: false,
-                    object_lifetime_default: rl::Set1::Empty,
-                    pure_wrt_drop: false,
-                    synthetic: None,
+                    kind: ty::GenericParamDefKind::Type(ty::TypeParamDef {
+                        has_default: false,
+                        object_lifetime_default: rl::Set1::Empty,
+                        pure_wrt_drop: false,
+                        synthetic: None,
+                    }),
                 }
             }));
         });
     }
 
-    let opt_self = opt_self.into_iter().map(|ty| ty::GenericParamDef::Type(ty));
-    let lifetimes = regions.into_iter().map(|lt| ty::GenericParamDef::Lifetime(lt));
-    let types = types.into_iter().map(|ty| ty::GenericParamDef::Type(ty));
-    let params: Vec<_> = opt_self.chain(lifetimes)
+    let params: Vec<_> = opt_self.into_iter()
+                                 .chain(lifetimes)
                                  .chain(types)
                                  .collect();
 
     let param_def_id_to_index = params.iter()
-                                      .map(|param| (param.def_id(), param.index()))
+                                      .map(|param| (param.def_id, param.index))
                                       .collect();
 
     tcx.alloc_generics(ty::Generics {
@@ -1101,7 +1109,7 @@ fn type_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                         let region = def.to_early_bound_region_data();
                         tcx.mk_region(ty::ReEarlyBound(region))
                     },
-                    |def, _| tcx.mk_param_from_def(def)
+                    |def, _| tcx.mk_ty_param_from_def(def)
                 )
             };
 
diff --git a/src/librustc_typeck/impl_wf_check.rs b/src/librustc_typeck/impl_wf_check.rs
index 1922a48d04a..f3645142e4b 100644
--- a/src/librustc_typeck/impl_wf_check.rs
+++ b/src/librustc_typeck/impl_wf_check.rs
@@ -117,24 +117,24 @@ fn enforce_impl_params_are_constrained<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
     for (ty_param, hir_param) in impl_generics.params.iter()
                                               .zip(impl_hir_generics.params.iter()) {
-        match (ty_param, hir_param) {
+        match (&ty_param.kind, hir_param) {
             // Disallow ANY unconstrained type parameters.
-            (ty::GenericParamDef::Type(ty_ty), hir::GenericParam::Type(hir_ty)) => {
-                let param_ty = ty::ParamTy::for_def(ty_ty);
+            (&ty::GenericParamDefKind::Type(_), hir::GenericParam::Type(hir_ty)) => {
+                let param_ty = ty::ParamTy::for_def(ty_param);
                 if !input_parameters.contains(&ctp::Parameter::from(param_ty)) {
                     report_unused_parameter(tcx, hir_ty.span, "type", &param_ty.to_string());
                 }
             }
-            (ty::GenericParamDef::Lifetime(ty_lt), hir::GenericParam::Lifetime(hir_lt)) => {
-                let param = ctp::Parameter::from(ty_lt.to_early_bound_region_data());
+            (&ty::GenericParamDefKind::Lifetime(_), hir::GenericParam::Lifetime(hir_lt)) => {
+                let param = ctp::Parameter::from(ty_param.to_early_bound_region_data());
                 if lifetimes_in_associated_types.contains(&param) && // (*)
                     !input_parameters.contains(&param) {
                     report_unused_parameter(tcx, hir_lt.lifetime.span,
                                             "lifetime", &hir_lt.lifetime.name.name().to_string());
                 }
             }
-            (ty::GenericParamDef::Type(_), _) => continue,
-            (ty::GenericParamDef::Lifetime(_), _) => continue,
+            (&ty::GenericParamDefKind::Type(_), _) => continue,
+            (&ty::GenericParamDefKind::Lifetime(_), _) => continue,
         }
     }
 
diff --git a/src/librustc_typeck/outlives/implicit_infer.rs b/src/librustc_typeck/outlives/implicit_infer.rs
index 5a9539a8bad..e711598c944 100644
--- a/src/librustc_typeck/outlives/implicit_infer.rs
+++ b/src/librustc_typeck/outlives/implicit_infer.rs
@@ -353,7 +353,7 @@ fn insert_outlives_predicate<'tcx>(
                         // Vec<U>`.  Decomposing `Vec<U>` into
                         // components would yield `U`, and we add the
                         // where clause that `U: 'a`.
-                        let ty: Ty<'tcx> = tcx.mk_param(param_ty.idx, param_ty.name);
+                        let ty: Ty<'tcx> = tcx.mk_ty_param(param_ty.idx, param_ty.name);
                         required_predicates
                             .insert(ty::OutlivesPredicate(ty.into(), outlived_region));
                     }
diff --git a/src/librustdoc/clean/auto_trait.rs b/src/librustdoc/clean/auto_trait.rs
index dc49cfcbc2b..88784aab90e 100644
--- a/src/librustdoc/clean/auto_trait.rs
+++ b/src/librustdoc/clean/auto_trait.rs
@@ -228,12 +228,12 @@ impl<'a, 'tcx, 'rcx> AutoTraitFinder<'a, 'tcx, 'rcx> {
         let mut types = vec![];
 
         for param in generics.params.iter() {
-            match param {
-                ty::GenericParamDef::Lifetime(lt) => {
-                    let name = if lt.name == "" {
+            match param.kind {
+                ty::GenericParamDefKind::Lifetime(_) => {
+                    let name = if param.name == "" {
                         hir::LifetimeName::Static
                     } else {
-                        hir::LifetimeName::Name(lt.name.as_symbol())
+                        hir::LifetimeName::Name(param.name.as_symbol())
                     };
 
                     lifetimes.push(hir::Lifetime {
@@ -242,8 +242,8 @@ impl<'a, 'tcx, 'rcx> AutoTraitFinder<'a, 'tcx, 'rcx> {
                         name,
                     });
                 }
-                ty::GenericParamDef::Type(ty) => {
-                    types.push(P(self.ty_param_to_ty(ty.clone())));
+                ty::GenericParamDefKind::Type(_) => {
+                    types.push(P(self.ty_param_to_ty(param.clone())));
                 }
             }
         }
@@ -256,7 +256,7 @@ impl<'a, 'tcx, 'rcx> AutoTraitFinder<'a, 'tcx, 'rcx> {
         }
     }
 
-    fn ty_param_to_ty(&self, param: ty::TypeParamDef) -> hir::Ty {
+    fn ty_param_to_ty(&self, param: ty::GenericParamDef) -> hir::Ty {
         debug!("ty_param_to_ty({:?}) {:?}", param, param.def_id);
         hir::Ty {
             id: ast::DUMMY_NODE_ID,
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index cb48d790f60..35a7b27670a 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1336,14 +1336,14 @@ impl Clean<TyParam> for hir::TyParam {
     }
 }
 
-impl<'tcx> Clean<TyParam> for ty::TypeParamDef {
+impl<'tcx> Clean<TyParam> for ty::GenericParamDef {
     fn clean(&self, cx: &DocContext) -> TyParam {
         cx.renderinfo.borrow_mut().external_typarams.insert(self.def_id, self.name.clean(cx));
         TyParam {
             name: self.name.clean(cx),
             did: self.def_id,
             bounds: vec![], // these are filled in from the where-clauses
-            default: if self.has_default {
+            default: if self.to_type().has_default {
                 Some(cx.tcx.type_of(self.def_id).clean(cx))
             } else {
                 None
@@ -1577,8 +1577,8 @@ impl Clean<Lifetime> for hir::LifetimeDef {
     }
 }
 
-impl Clean<Lifetime> for ty::RegionParamDef {
-    fn clean(&self, _: &DocContext) -> Lifetime {
+impl<'tcx> Clean<Lifetime> for ty::GenericParamDef {
+    fn clean(&self, _cx: &DocContext) -> Lifetime {
         Lifetime(self.name.to_string())
     }
 }
@@ -1800,17 +1800,17 @@ impl<'a, 'tcx> Clean<Generics> for (&'a ty::Generics,
         // predicates field (see rustc_typeck::collect::ty_generics), so remove
         // them.
         let stripped_typarams = gens.params.iter().filter_map(|param| {
-            if let ty::GenericParamDef::Type(ty) = param {
-                if ty.name == keywords::SelfType.name().as_str() {
-                    assert_eq!(ty.index, 0);
+            if let ty::GenericParamDefKind::Type(_) = param.kind {
+                if param.name == keywords::SelfType.name().as_str() {
+                    assert_eq!(param.index, 0);
                     None
                 } else {
-                    Some(ty.clean(cx))
+                    Some(param.clean(cx))
                 }
             } else {
                 None
             }
-        }).collect::<Vec<_>>();
+        }).collect::<Vec<TyParam>>();
 
         let mut where_predicates = preds.predicates.to_vec().clean(cx);
 
@@ -1855,8 +1855,8 @@ impl<'a, 'tcx> Clean<Generics> for (&'a ty::Generics,
             params: gens.params
                         .iter()
                         .flat_map(|param| {
-                            if let ty::GenericParamDef::Lifetime(lt) = param {
-                                Some(GenericParamDef::Lifetime(lt.clean(cx)))
+                            if let ty::GenericParamDefKind::Lifetime(_) = param.kind {
+                                Some(GenericParamDef::Lifetime(param.clean(cx)))
                             } else {
                                 None
                             }