chore: add deprecations for duplicated theorems

src/Init/Control/Lawful/Basic.lean

@@ -170,6 +170,7 @@ theorem bind_pure_unit [Monad m] [LawfulMonad m] {x : m PUnit} : (x >>= fun _ =>
 theorem map_congr [Functor m] {x : m α} {f g : α → β} (h : ∀ a, f a = g a) : (f <$> x : m β) = g <$> x := by
   simp [funext h]
 
+@[deprecated seq_eq_bind_map (since := "2025-10-26")]
 theorem seq_eq_bind {α β : Type u} [Monad m] [LawfulMonad m] (mf : m (α → β)) (x : m α) : mf <*> x = mf >>= fun f => f <$> x := by
   rw [bind_map]
 
@@ -256,14 +257,3 @@ instance : LawfulMonad Id := by
 @[simp] theorem run_seq (f : Id (α → β)) (x : Id α) : (f <*> x).run = f.run x.run := rfl
 
 end Id
-
-/-! # Option -/
-
-instance : LawfulMonad Option := LawfulMonad.mk'
-  (id_map := fun x => by cases x <;> rfl)
-  (pure_bind := fun _ _ => rfl)
-  (bind_assoc := fun x _ _ => by cases x <;> rfl)
-  (bind_pure_comp := fun _ x => by cases x <;> rfl)
-
-instance : LawfulApplicative Option := inferInstance
-instance : LawfulFunctor Option := inferInstance

src/Init/Control/Lawful/Instances.lean

@@ -189,12 +189,12 @@ instance [Monad m] [LawfulMonad m] : LawfulMonad (OptionT m) where
 
 @[simp] theorem run_seq [Monad m] [LawfulMonad m] (f : OptionT m (α → β)) (x : OptionT m α) :
     (f <*> x).run = Option.elimM f.run (pure none) (fun f => Option.map f <$> x.run) := by
-  simp [seq_eq_bind, Option.elimM, Option.elim]
+  simp [seq_eq_bind_map, Option.elimM, Option.elim]
 
 @[simp] theorem run_seqLeft [Monad m] [LawfulMonad m] (x : OptionT m α) (y : OptionT m β) :
     (x <* y).run = Option.elimM x.run (pure none)
       (fun x => Option.map (Function.const β x) <$> y.run) := by
-  simp [seqLeft_eq, seq_eq_bind, Option.elimM, OptionT.run_bind]
+  simp [seqLeft_eq, seq_eq_bind_map, Option.elimM, OptionT.run_bind]
 
 @[simp] theorem run_seqRight [Monad m] [LawfulMonad m] (x : OptionT m α) (y : OptionT m β) :
     (x *> y).run = Option.elimM x.run (pure none) (Function.const α y.run) := by
@@ -219,7 +219,7 @@ instance : LawfulMonad Option := LawfulMonad.mk'
   (id_map := fun x => by cases x <;> rfl)
   (pure_bind := fun _ _ => by rfl)
   (bind_assoc := fun a _ _ => by cases a <;> rfl)
-  (bind_pure_comp := bind_pure_comp)
+  (bind_pure_comp := fun _ x => by cases x <;> rfl)
 
 instance : LawfulApplicative Option := inferInstance
 instance : LawfulFunctor Option := inferInstance

src/Init/Control/Lawful/MonadLift/Lemmas.lean

@@ -23,7 +23,7 @@ theorem monadLift_map [LawfulMonad m] [LawfulMonad n] (f : α → β) (ma : m α
 
 theorem monadLift_seq [LawfulMonad m] [LawfulMonad n] (mf : m (α → β)) (ma : m α) :
     monadLift (mf <*> ma) = monadLift mf <*> (monadLift ma : n α) := by
-  simp only [seq_eq_bind, monadLift_map, monadLift_bind]
+  simp only [seq_eq_bind_map, monadLift_map, monadLift_bind]
 
 theorem monadLift_seqLeft [LawfulMonad m] [LawfulMonad n] (x : m α) (y : m β) :
     monadLift (x <* y) = (monadLift x : n α) <* (monadLift y : n β) := by

src/Init/Core.lean

@@ -1348,8 +1348,12 @@ namespace Subtype
 theorem exists_of_subtype {α : Type u} {p : α → Prop} : { x // p x } → Exists (fun x => p x)
   | ⟨a, h⟩ => ⟨a, h⟩
 
-variable {α : Type u} {p : α → Prop}
+variable {α : Sort u} {p : α → Prop}
 
+protected theorem ext : ∀ {a1 a2 : {x // p x}}, val a1 = val a2 → a1 = a2
+  | ⟨_, _⟩, ⟨_, _⟩, rfl => rfl
+
+@[deprecated Subtype.ext (since := "2025-10-26")]
 protected theorem eq : ∀ {a1 a2 : {x // p x}}, val a1 = val a2 → a1 = a2
   | ⟨_, _⟩, ⟨_, _⟩, rfl => rfl
 
@@ -1364,9 +1368,9 @@ instance {α : Type u} {p : α → Prop} [BEq α] [ReflBEq α] : ReflBEq {x : α
   rfl {x} := BEq.refl x.1
 
 instance {α : Type u} {p : α → Prop} [BEq α] [LawfulBEq α] : LawfulBEq {x : α // p x} where
-  eq_of_beq h := Subtype.eq (eq_of_beq h)
+  eq_of_beq h := Subtype.ext (eq_of_beq h)
 
-instance {α : Type u} {p : α → Prop} [DecidableEq α] : DecidableEq {x : α // p x} :=
+instance {α : Sort u} {p : α → Prop} [DecidableEq α] : DecidableEq {x : α // p x} :=
   fun ⟨a, h₁⟩ ⟨b, h₂⟩ =>
     if h : a = b then isTrue (by subst h; exact rfl)
     else isFalse (fun h' => Subtype.noConfusion h' (fun h' => absurd h' h))
@@ -1483,20 +1487,24 @@ protected theorem PSigma.eta {α : Sort u} {β : α → Sort v} {a₁ a₂ : α}
 
 /-! # Universe polymorphic unit -/
 
+theorem PUnit.ext (a b : PUnit) : a = b := by
+  cases a; cases b; exact rfl
+
+@[deprecated PUnit.ext (since := "2025-10-26")]
 theorem PUnit.subsingleton (a b : PUnit) : a = b := by
   cases a; cases b; exact rfl
 
 theorem PUnit.eq_punit (a : PUnit) : a = ⟨⟩ :=
-  PUnit.subsingleton a ⟨⟩
+  PUnit.ext a ⟨⟩
 
 instance : Subsingleton PUnit :=
-  Subsingleton.intro PUnit.subsingleton
+  Subsingleton.intro PUnit.ext
 
 instance : Inhabited PUnit where
   default := ⟨⟩
 
 instance : DecidableEq PUnit :=
-  fun a b => isTrue (PUnit.subsingleton a b)
+  fun a b => isTrue (PUnit.ext a b)
 
 /-! # Setoid -/
 

src/Init/Data/Array/Bootstrap.lean

@@ -31,7 +31,7 @@ theorem foldlM_toList.aux [Monad m]
   · cases Nat.not_le_of_gt ‹_› (Nat.zero_add _ ▸ H)
   · rename_i i; rw [Nat.succ_add] at H
     simp [foldlM_toList.aux (j := j+1) H]
-    rw (occs := [2]) [← List.getElem_cons_drop_succ_eq_drop ‹_›]
+    rw (occs := [2]) [← List.getElem_cons_drop ‹_›]
     simp
   · rw [List.drop_of_length_le (Nat.ge_of_not_lt ‹_›)]; simp
 

src/Init/Data/Array/GetLit.lean

@@ -50,6 +50,6 @@ where
   getLit_eq (xs : Array α) (i : Nat) (h₁ : xs.size = n) (h₂ : i < n) : xs.getLit i h₁ h₂ = getElem xs.toList i ((id (α := xs.toList.length = n) h₁) ▸ h₂) :=
     rfl
   go (i : Nat) (hi : i ≤ xs.size) : toListLitAux xs n hsz i hi (xs.toList.drop i) = xs.toList := by
-    induction i <;> simp only [List.drop, toListLitAux, getLit_eq, List.getElem_cons_drop_succ_eq_drop, *]
+    induction i <;> simp only [List.drop, toListLitAux, getLit_eq, List.getElem_cons_drop, *]
 
 end Array

src/Init/Data/Array/Lemmas.lean

@@ -265,8 +265,6 @@ theorem push_eq_push {a b : α} {xs ys : Array α} : xs.push a = ys.push b ↔ a
   · rintro ⟨rfl, rfl⟩
     rfl
 
-theorem push_eq_append_singleton {as : Array α} {x : α} : as.push x = as ++ #[x] := rfl
-
 theorem exists_push_of_ne_empty {xs : Array α} (h : xs ≠ #[]) :
     ∃ (ys : Array α) (a : α), xs = ys.push a := by
   rcases xs with ⟨xs⟩
@@ -817,6 +815,11 @@ theorem contains_eq_true_of_mem [BEq α] [ReflBEq α] {a : α} {as : Array α} (
 theorem elem_iff [BEq α] [LawfulBEq α] {a : α} {xs : Array α} :
     elem a xs = true ↔ a ∈ xs := ⟨mem_of_contains_eq_true, contains_eq_true_of_mem⟩
 
+@[grind =]
+theorem contains_iff_mem [BEq α] [LawfulBEq α] {a : α} {xs : Array α} :
+    xs.contains a = true ↔ a ∈ xs := ⟨mem_of_contains_eq_true, contains_eq_true_of_mem⟩
+
+@[deprecated contains_iff_mem (since := "2025-10-26")]
 theorem contains_iff [BEq α] [LawfulBEq α] {a : α} {xs : Array α} :
     xs.contains a = true ↔ a ∈ xs := ⟨mem_of_contains_eq_true, contains_eq_true_of_mem⟩
 
@@ -1139,7 +1142,7 @@ where
   aux (i bs) :
       mapM.map f xs i bs = (xs.toList.drop i).foldlM (fun bs a => bs.push <$> f a) bs := by
     unfold mapM.map; split
-    · rw [← List.getElem_cons_drop_succ_eq_drop ‹_›]
+    · rw [← List.getElem_cons_drop ‹_›]
       simp only [aux (i + 1), map_eq_pure_bind, List.foldlM_cons, bind_assoc,
         pure_bind]
       rfl
@@ -1853,6 +1856,9 @@ theorem getElem_of_append {xs ys zs : Array α} (eq : xs = ys.push a ++ zs) (h :
 
 theorem push_eq_append {a : α} {as : Array α} : as.push a = as ++ #[a] := rfl
 
+@[deprecated push_eq_append (since := "2025-10-26")]
+theorem push_eq_append_singleton {as : Array α} {x : α} : as.push x = as ++ #[x] := rfl
+
 theorem append_inj {xs₁ xs₂ ys₁ ys₂ : Array α} (h : xs₁ ++ ys₁ = xs₂ ++ ys₂) (hl : xs₁.size = xs₂.size) :
     xs₁ = xs₂ ∧ ys₁ = ys₂ := by
   rcases xs₁ with ⟨s₁⟩
@@ -2053,11 +2059,22 @@ theorem append_eq_map_iff {f : α → β} :
   | nil => simp
   | cons as => induction as.toList <;> simp [*]
 
-@[simp] theorem flatten_toArray_map {L : List (List α)} :
+@[simp] theorem flatten_toArray_map_toArray {L : List (List α)} :
     (L.map List.toArray).toArray.flatten = L.flatten.toArray := by
   apply ext'
   simp [Function.comp_def]
 
+@[deprecated flatten_toArray_map_toArray (since := "2025-10-26")]
+theorem flatten_toArray_map {L : List (List α)} :
+    (L.map List.toArray).toArray.flatten = L.flatten.toArray := by
+  simp
+
+@[grind =]
+theorem flatten_map_toArray_toArray {L : List (List α)} :
+    (L.toArray.map List.toArray).flatten = L.flatten.toArray := by
+  simp
+
+@[deprecated flatten_map_toArray_toArray (since := "2025-10-26")]
 theorem flatten_map_toArray {L : List (List α)} :
     (L.toArray.map List.toArray).flatten = L.flatten.toArray := by
   simp
@@ -2104,32 +2121,33 @@ theorem forall_mem_flatten {p : α → Prop} {xss : Array (Array α)} :
 
 theorem flatten_eq_flatMap {xss : Array (Array α)} : flatten xss = xss.flatMap id := by
   induction xss using array₂_induction
-  rw [flatten_toArray_map, List.flatten_eq_flatMap]
+  rw [flatten_toArray_map_toArray, List.flatten_eq_flatMap]
   simp [List.flatMap_map]
 
 @[simp, grind _=_] theorem map_flatten {f : α → β} {xss : Array (Array α)} :
     (flatten xss).map f = (map (map f) xss).flatten := by
   induction xss using array₂_induction with
   | of xss =>
-    simp only [flatten_toArray_map, List.map_toArray, List.map_flatten, List.map_map,
+    simp only [flatten_toArray_map_toArray, List.map_toArray, List.map_flatten, List.map_map,
       Function.comp_def]
-    rw [← Function.comp_def, ← List.map_map, flatten_toArray_map]
+    rw [← Function.comp_def, ← List.map_map, flatten_toArray_map_toArray]
 
 @[simp, grind =] theorem filterMap_flatten {f : α → Option β} {xss : Array (Array α)} {stop : Nat} (w : stop = xss.flatten.size) :
     filterMap f (flatten xss) 0 stop = flatten (map (filterMap f) xss) := by
   subst w
   induction xss using array₂_induction
-  simp only [flatten_toArray_map, List.size_toArray, List.length_flatten, List.filterMap_toArray',
-    List.filterMap_flatten, List.map_toArray, List.map_map, Function.comp_def]
-  rw [← Function.comp_def, ← List.map_map, flatten_toArray_map]
+  simp only [flatten_toArray_map_toArray, List.size_toArray, List.length_flatten,
+    List.filterMap_toArray', List.filterMap_flatten, List.map_toArray, List.map_map,
+    Function.comp_def]
+  rw [← Function.comp_def, ← List.map_map, flatten_toArray_map_toArray]
 
 @[simp, grind =] theorem filter_flatten {p : α → Bool} {xss : Array (Array α)} {stop : Nat} (w : stop = xss.flatten.size) :
     filter p (flatten xss) 0 stop = flatten (map (filter p) xss) := by
   subst w
   induction xss using array₂_induction
-  simp only [flatten_toArray_map, List.size_toArray, List.length_flatten, List.filter_toArray',
-    List.filter_flatten, List.map_toArray, List.map_map, Function.comp_def]
-  rw [← Function.comp_def, ← List.map_map, flatten_toArray_map]
+  simp only [flatten_toArray_map_toArray, List.size_toArray, List.length_flatten,
+    List.filter_toArray', List.filter_flatten, List.map_toArray, List.map_map, Function.comp_def]
+  rw [← Function.comp_def, ← List.map_map, flatten_toArray_map_toArray]
 
 theorem flatten_filter_not_isEmpty {xss : Array (Array α)} :
     flatten (xss.filter fun xs => !xs.isEmpty) = xss.flatten := by
@@ -2152,23 +2170,23 @@ theorem flatten_filter_ne_empty [DecidablePred fun xs : Array α => xs ≠ #[]]
   induction xss using array₂_induction
   rcases xs with ⟨l⟩
   have this : [l.toArray] = [l].map List.toArray := by simp
-  simp only [List.push_toArray, flatten_toArray_map, List.append_toArray]
-  rw [this, ← List.map_append, flatten_toArray_map]
+  simp only [List.push_toArray, flatten_toArray_map_toArray, List.append_toArray]
+  rw [this, ← List.map_append, flatten_toArray_map_toArray]
   simp
 
 theorem flatten_flatten {xss : Array (Array (Array α))} : flatten (flatten xss) = flatten (map flatten xss) := by
   induction xss using array₃_induction with
   | of xss =>
-    rw [flatten_toArray_map]
+    rw [flatten_toArray_map_toArray]
     have : (xss.map (fun xs => xs.map List.toArray)).flatten = xss.flatten.map List.toArray := by
       induction xss with
       | nil => simp
       | cons xs xss ih =>
         simp only [List.map_cons, List.flatten_cons, ih, List.map_append]
-    rw [this, flatten_toArray_map, List.flatten_flatten, ← List.map_toArray, Array.map_map,
+    rw [this, flatten_toArray_map_toArray, List.flatten_flatten, ← List.map_toArray, Array.map_map,
       ← List.map_toArray, map_map, Function.comp_def]
-    simp only [Function.comp_apply, flatten_toArray_map]
-    rw [List.map_toArray, ← Function.comp_def, ← List.map_map, flatten_toArray_map]
+    simp only [Function.comp_apply, flatten_toArray_map_toArray]
+    rw [List.map_toArray, ← Function.comp_def, ← List.map_map, flatten_toArray_map_toArray]
 
 theorem flatten_eq_push_iff {xss : Array (Array α)} {ys : Array α} {y : α} :
     xss.flatten = ys.push y ↔
@@ -2177,13 +2195,13 @@ theorem flatten_eq_push_iff {xss : Array (Array α)} {ys : Array α} {y : α} :
   induction xss using array₂_induction with
   | of xs =>
     rcases ys with ⟨ys⟩
-    rw [flatten_toArray_map, List.push_toArray, mk.injEq, List.flatten_eq_append_iff]
+    rw [flatten_toArray_map_toArray, List.push_toArray, mk.injEq, List.flatten_eq_append_iff]
     constructor
     · rintro (⟨as, bs, rfl, rfl, h⟩ | ⟨as, bs, c, cs, ds, rfl, rfl, h⟩)
       · rw [List.singleton_eq_flatten_iff] at h
         obtain ⟨xs, ys, rfl, h₁, h₂⟩ := h
         exact ⟨((as ++ xs).map List.toArray).toArray, #[], (ys.map List.toArray).toArray, by simp,
-          by simpa using h₂, by rw [flatten_toArray_map]; simpa⟩
+          by simpa using h₂, by rw [flatten_toArray_map_toArray]; simpa⟩
       · rw [List.singleton_eq_append_iff] at h
         obtain (⟨h₁, h₂⟩ | ⟨h₁, h₂⟩) := h
         · simp at h₁
@@ -2228,10 +2246,6 @@ theorem eq_iff_flatten_eq {xss₁ xss₂ : Array (Array α)} :
       rw [List.map_inj_right]
       simp +contextual
 
-theorem flatten_toArray_map_toArray {xss : List (List α)} :
-    (xss.map List.toArray).toArray.flatten = xss.flatten.toArray := by
-  simp
-
 /-! ### flatMap -/
 
 theorem flatMap_def {xs : Array α} {f : α → Array β} : xs.flatMap f = flatten (map f xs) := by
@@ -2535,8 +2549,8 @@ theorem getElem?_swap {xs : Array α} {i j : Nat} (hi hj) {k : Nat} : (xs.swap i
         split <;> rename_i h₃
         · simp only [← h₃, Nat.not_le.2 (Nat.lt_succ_self _), Nat.le_refl, false_and]
           exact (List.getElem?_reverse' (Eq.trans (by simp +arith) h)).symm
-        simp only [Nat.succ_le, Nat.lt_iff_le_and_ne.trans (and_iff_left h₃),
-          Nat.lt_succ.symm.trans (Nat.lt_iff_le_and_ne.trans (and_iff_left (Ne.symm h₂)))]
+        simp only [Nat.succ_le_iff, Nat.lt_iff_le_and_ne.trans (and_iff_left h₃),
+          Nat.lt_succ_iff.symm.trans (Nat.lt_iff_le_and_ne.trans (and_iff_left (Ne.symm h₂)))]
     · rw [H]; split <;> rename_i h₂
       · cases Nat.le_antisymm (Nat.not_lt.1 h₁) (Nat.le_trans h₂.1 h₂.2)
         cases Nat.le_antisymm h₂.1 h₂.2
@@ -2551,7 +2565,7 @@ theorem getElem?_swap {xs : Array α} {i j : Nat} (hi hj) {k : Nat} : (xs.swap i
     split
     · rfl
     · rename_i h
-      simp only [← show k < _ + 1 ↔ _ from Nat.lt_succ (n := xs.size - 1), this, Nat.zero_le,
+      simp only [← show k < _ + 1 ↔ _ from Nat.lt_succ_iff (n := xs.size - 1), this, Nat.zero_le,
         true_and, Nat.not_lt] at h
       rw [List.getElem?_eq_none_iff.2 ‹_›, List.getElem?_eq_none_iff.2 (xs.toList.length_reverse ▸ ‹_›)]
 
@@ -2699,8 +2713,8 @@ theorem extract_loop_eq_aux {xs ys : Array α} {size start : Nat} :
   | zero => rw [extract_loop_zero, extract_loop_zero, append_empty]
   | succ size ih =>
     if h : start < xs.size then
-      rw [extract_loop_succ (h := h), ih, push_eq_append_singleton]
-      rw [extract_loop_succ (h := h), ih (ys := #[].push _), push_eq_append_singleton, empty_append]
+      rw [extract_loop_succ (h := h), ih, push_eq_append]
+      rw [extract_loop_succ (h := h), ih (ys := #[].push _), push_eq_append, empty_append]
       rw [append_assoc]
     else
       rw [extract_loop_of_ge (h := Nat.le_of_not_lt h)]
@@ -3622,11 +3636,6 @@ theorem contains_iff_exists_mem_beq [BEq α] {xs : Array α} {a : α} :
 -- With `LawfulBEq α`, it would be better to use `contains_iff_mem` directly.
 grind_pattern contains_iff_exists_mem_beq => xs.contains a
 
-@[grind =]
-theorem contains_iff_mem [BEq α] [LawfulBEq α] {xs : Array α} {a : α} :
-    xs.contains a ↔ a ∈ xs := by
-  simp
-
 @[simp, grind =]
 theorem contains_toList [BEq α] {xs : Array α} {x : α} :
     xs.toList.contains x = xs.contains x := by
@@ -4276,6 +4285,7 @@ theorem getElem_fin_eq_getElem_toList {xs : Array α} {i : Fin xs.size} : xs[i]
 @[simp] theorem ugetElem_eq_getElem {xs : Array α} {i : USize} (h : i.toNat < xs.size) :
   xs[i] = xs[i.toNat] := rfl
 
+@[deprecated getElem?_eq_none (since := "2025-10-26")]
 theorem getElem?_size_le {xs : Array α} {i : Nat} (h : xs.size ≤ i) : xs[i]? = none := by
   simp [getElem?_neg, h]
 
@@ -4295,6 +4305,7 @@ theorem getElem?_push_lt {xs : Array α} {x : α} {i : Nat} (h : i < xs.size) :
     (xs.push x)[i]? = some xs[i] := by
   rw [getElem?_pos (xs.push x) i (size_push _ ▸ Nat.lt_succ_of_lt h), getElem_push_lt]
 
+@[deprecated getElem?_push_size (since := "2025-10-26")]
 theorem getElem?_push_eq {xs : Array α} {x : α} : (xs.push x)[xs.size]? = some x := by
   rw [getElem?_pos (xs.push x) xs.size (size_push _ ▸ Nat.lt_succ_self xs.size), getElem_push_eq]
 
@@ -4426,7 +4437,8 @@ theorem uset_toArray {l : List α} {i : USize} {a : α} {h : i.toNat < l.toArray
   apply ext'
   simp
 
-@[simp, grind =] theorem flatten_toArray {L : List (List α)} :
+@[deprecated Array.flatten_map_toArray_toArray (since := "2025-10-26")]
+theorem flatten_toArray {L : List (List α)} :
     (L.toArray.map List.toArray).flatten = L.flatten.toArray := by
   apply ext'
   simp

src/Init/Data/Array/Lex/Lemmas.lean

@@ -34,7 +34,18 @@ grind_pattern _root_.List.le_toArray => l₁.toArray ≤ l₂.toArray
 grind_pattern lt_toList => xs.toList < ys.toList
 grind_pattern le_toList => xs.toList ≤ ys.toList
 
+@[simp]
+protected theorem not_lt [LT α] {xs ys : Array α} : ¬ xs < ys ↔ ys ≤ xs := Iff.rfl
+
+@[deprecated Array.not_lt (since := "2025-10-26")]
 protected theorem not_lt_iff_ge [LT α] {xs ys : Array α} : ¬ xs < ys ↔ ys ≤ xs := Iff.rfl
+
+@[simp]
+protected theorem not_le [LT α] {xs ys : Array α} :
+    ¬ xs ≤ ys ↔ ys < xs :=
+  Classical.not_not
+
+@[deprecated Array.not_le (since := "2025-10-26")]
 protected theorem not_le_iff_gt [LT α] {xs ys : Array α} :
     ¬ xs ≤ ys ↔ ys < xs :=
   Classical.not_not
@@ -178,12 +189,6 @@ protected theorem le_total [LT α]
     [i : Std.Asymm (· < · : α → α → Prop)] (xs ys : Array α) : xs ≤ ys ∨ ys ≤ xs :=
   List.le_total xs.toList ys.toList
 
-@[simp] protected theorem not_lt [LT α]
-    {xs ys : Array α} : ¬ xs < ys ↔ ys ≤ xs := Iff.rfl
-
-@[simp] protected theorem not_le [LT α]
-    {xs ys : Array α} : ¬ ys ≤ xs ↔ xs < ys := Classical.not_not
-
 protected theorem le_of_lt [LT α]
     [i : Std.Asymm (· < · : α → α → Prop)]
     {xs ys : Array α} (h : xs < ys) : xs ≤ ys :=