diff --git a/src/Init/Data/Hashable.lean b/src/Init/Data/Hashable.lean
index 5420c44255..4a41888514 100644
--- a/src/Init/Data/Hashable.lean
+++ b/src/Init/Data/Hashable.lean
@@ -42,42 +42,4 @@ instance : Hashable Int where
     | Int.negSucc n => UInt64.ofNat (2 * n + 1)
 
 instance (P : Prop) : Hashable P where
-  hash := Function.const P 0
-
--- TO DELETE
-
-instance : HashableUSize Nat where
-  hashUSize n := USize.ofNat n
-
-instance [HashableUSize α] [HashableUSize β] : HashableUSize (α × β) where
-  hashUSize | (a, b) => mixUSizeHash (hashUSize a) (hashUSize b)
-
-instance : HashableUSize Bool where
-  hashUSize
-    | true  => 11
-    | false => 13
-
-instance [HashableUSize α] : HashableUSize (Option α) where
-  hashUSize
-    | none   => 11
-    | some a => mixUSizeHash (hashUSize a) 13
-
-instance [HashableUSize α] : HashableUSize (List α) where
-  hashUSize as := as.foldl (fun r a => mixUSizeHash r (hashUSize a)) 7
-
-instance : HashableUSize UInt32 where
-  hashUSize n := n.toUSize
-
-instance : HashableUSize UInt64 where
-  hashUSize n := n.toUSize
-
-instance : HashableUSize USize where
-  hashUSize n := n
-
-instance : HashableUSize Int where
-  hashUSize
-    | Int.ofNat n => USize.ofNat (2 * n)
-    | Int.negSucc n => USize.ofNat (2 * n + 1)
-
-instance (P : Prop) : HashableUSize P where
-  hashUSize := Function.const P 0
+  hash p := 0
diff --git a/src/Lean/Compiler/IR/Basic.lean b/src/Lean/Compiler/IR/Basic.lean
index f3a03fa022..8931dcb121 100644
--- a/src/Lean/Compiler/IR/Basic.lean
+++ b/src/Lean/Compiler/IR/Basic.lean
@@ -35,12 +35,12 @@ abbrev Index.lt (a b : Index) : Bool := a < b
 instance : BEq VarId := ⟨fun a b => a.idx == b.idx⟩
 instance : ToString VarId := ⟨fun a => "x_" ++ toString a.idx⟩
 instance : ToFormat VarId := ⟨fun a => toString a⟩
-instance : HashableUSize VarId := ⟨fun a => hashUSize a.idx⟩
+instance : Hashable VarId := ⟨fun a => hash a.idx⟩
 
 instance : BEq JoinPointId := ⟨fun a b => a.idx == b.idx⟩
 instance : ToString JoinPointId := ⟨fun a => "block_" ++ toString a.idx⟩
 instance : ToFormat JoinPointId := ⟨fun a => toString a⟩
-instance : HashableUSize JoinPointId := ⟨fun a => hashUSize a.idx⟩
+instance : Hashable JoinPointId := ⟨fun a => hash a.idx⟩
 
 abbrev MData := KVMap
 abbrev MData.empty : MData := {}
diff --git a/src/Lean/Compiler/IR/Borrow.lean b/src/Lean/Compiler/IR/Borrow.lean
index 4cdf9f439b..71c49ebc39 100644
--- a/src/Lean/Compiler/IR/Borrow.lean
+++ b/src/Lean/Compiler/IR/Borrow.lean
@@ -19,9 +19,9 @@ def beq : Key → Key → Bool
 
 instance : BEq Key := ⟨beq⟩
 
-def getHash : Key → USize
-  | (f, x) => mixUSizeHash (hashUSize f) (hashUSize x)
-instance : HashableUSize Key := ⟨getHash⟩
+def getHash : Key → UInt64
+  | (f, x) => mixHash (hash f) (hash x)
+instance : Hashable Key := ⟨getHash⟩
 end OwnedSet
 
 open OwnedSet (Key) in
@@ -40,11 +40,11 @@ inductive Key where
   | jp   (name : FunId) (jpid : JoinPointId)
   deriving BEq
 
-def getHash : Key → USize
-  | Key.decl n  => hashUSize n
-  | Key.jp n id => mixUSizeHash (hashUSize n) (hashUSize id)
+def getHash : Key → UInt64
+  | Key.decl n  => hash n
+  | Key.jp n id => mixHash (hash n) (hash id)
 
-instance : HashableUSize Key := ⟨getHash⟩
+instance : Hashable Key := ⟨getHash⟩
 end ParamMap
 
 open ParamMap (Key)
diff --git a/src/Lean/Elab/Deriving/Hashable.lean b/src/Lean/Elab/Deriving/Hashable.lean
index 9f5f5cc723..f2b55effd7 100644
--- a/src/Lean/Elab/Deriving/Hashable.lean
+++ b/src/Lean/Elab/Deriving/Hashable.lean
@@ -86,5 +86,5 @@ def mkHashableHandler (declNames : Array Name) : CommandElabM Bool := do
     return false
 
 builtin_initialize
-  registerBuiltinDerivingHandler ``HashableUSize mkHashableHandler
+  registerBuiltinDerivingHandler ``Hashable mkHashableHandler
   registerTraceClass `Elab.Deriving.hashable
diff --git a/src/Lean/HeadIndex.lean b/src/Lean/HeadIndex.lean
index fa7bf42d47..6fa3e28d83 100644
--- a/src/Lean/HeadIndex.lean
+++ b/src/Lean/HeadIndex.lean
@@ -20,17 +20,17 @@ inductive HeadIndex where
 
 namespace HeadIndex
 
-protected def HeadIndex.hash : HeadIndex → USize
-  | fvar fvarId         => mixUSizeHash 11 $ hashUSize fvarId
-  | mvar mvarId         => mixUSizeHash 13 $ hashUSize mvarId
-  | const constName     => mixUSizeHash 17 $ hashUSize constName
-  | proj structName idx => mixUSizeHash 19 $ mixUSizeHash (hashUSize structName) (hashUSize idx)
-  | lit litVal          => mixUSizeHash 23 $ hashUSize litVal
+protected def HeadIndex.hash : HeadIndex → UInt64
+  | fvar fvarId         => mixHash 11 $ hash fvarId
+  | mvar mvarId         => mixHash 13 $ hash mvarId
+  | const constName     => mixHash 17 $ hash constName
+  | proj structName idx => mixHash 19 $ mixHash (hash structName) (hash idx)
+  | lit litVal          => mixHash 23 $ hash litVal
   | sort                => 29
   | lam                 => 31
   | forallE             => 37
 
-instance : HashableUSize HeadIndex := ⟨HeadIndex.hash⟩
+instance : Hashable HeadIndex := ⟨HeadIndex.hash⟩
 
 end HeadIndex
 
diff --git a/src/Lean/Meta/Basic.lean b/src/Lean/Meta/Basic.lean
index 7e6183d74a..fea3d4c869 100644
--- a/src/Lean/Meta/Basic.lean
+++ b/src/Lean/Meta/Basic.lean
@@ -80,8 +80,8 @@ structure InfoCacheKey where
   deriving Inhabited, BEq
 
 namespace InfoCacheKey
-instance : HashableUSize InfoCacheKey :=
-  ⟨fun ⟨transparency, expr, nargs⟩ => mixUSizeHash (hashUSize transparency) <| mixUSizeHash (hashUSize expr) (hashUSize nargs)⟩
+instance : Hashable InfoCacheKey :=
+  ⟨fun ⟨transparency, expr, nargs⟩ => mixHash (hash transparency) <| mixHash (hash expr) (hash nargs)⟩
 end InfoCacheKey
 
 open Std (PersistentArray PersistentHashMap)
diff --git a/src/Lean/Meta/DiscrTreeTypes.lean b/src/Lean/Meta/DiscrTreeTypes.lean
index 655893cf99..460991be47 100644
--- a/src/Lean/Meta/DiscrTreeTypes.lean
+++ b/src/Lean/Meta/DiscrTreeTypes.lean
@@ -20,15 +20,15 @@ inductive Key where
   | arrow : Key
   deriving Inhabited, BEq
 
-protected def Key.hash : Key → USize
-  | Key.const n a => mixUSizeHash 5237 $ mixUSizeHash (hashUSize n) (hashUSize a)
-  | Key.fvar n a  => mixUSizeHash 3541 $ mixUSizeHash (hashUSize n) (hashUSize a)
-  | Key.lit v     => mixUSizeHash 1879 $ hashUSize v
+protected def Key.hash : Key → UInt64
+  | Key.const n a => mixHash 5237 $ mixHash (hash n) (hash a)
+  | Key.fvar n a  => mixHash 3541 $ mixHash (hash n) (hash a)
+  | Key.lit v     => mixHash 1879 $ hash v
   | Key.star      => 7883
   | Key.other     => 2411
   | Key.arrow     => 17
 
-instance : HashableUSize Key := ⟨Key.hash⟩
+instance : Hashable Key := ⟨Key.hash⟩
 
 inductive Trie (α : Type) where
   | node (vs : Array α) (children : Array (Key × Trie α)) : Trie α
diff --git a/src/Lean/Meta/TransparencyMode.lean b/src/Lean/Meta/TransparencyMode.lean
index 7988bccadc..3a36af4b7f 100644
--- a/src/Lean/Meta/TransparencyMode.lean
+++ b/src/Lean/Meta/TransparencyMode.lean
@@ -11,13 +11,13 @@ inductive TransparencyMode where
 
 namespace TransparencyMode
 
-def hash : TransparencyMode → USize
+def hash : TransparencyMode → UInt64
   | all       => 7
   | default   => 11
   | reducible => 13
   | instances => 17
 
-instance : HashableUSize TransparencyMode := ⟨hash⟩
+instance : Hashable TransparencyMode := ⟨hash⟩
 
 def lt : TransparencyMode → TransparencyMode → Bool
   | reducible, default   => true