diff --git a/src/Init/Data/String/Basic.lean b/src/Init/Data/String/Basic.lean
index 000e69b90f..bddfd76f6f 100644
--- a/src/Init/Data/String/Basic.lean
+++ b/src/Init/Data/String/Basic.lean
@@ -2077,9 +2077,14 @@ theorem Slice.Pos.prevAux_lt_self {s : Slice} {p : s.Pos} {h} : p.prevAux h < p.
 theorem Slice.Pos.prevAux_lt_rawEndPos {s : Slice} {p : s.Pos} {h} : p.prevAux h < s.rawEndPos :=
   Pos.Raw.lt_of_lt_of_le prevAux_lt_self p.isValidForSlice.le_utf8ByteSize
 
+@[simp]
 theorem Slice.Pos.prev_ne_endPos {s : Slice} {p : s.Pos} {h} : p.prev h ≠ s.endPos := by
   simpa [Pos.ext_iff, prev] using Pos.Raw.ne_of_lt prevAux_lt_rawEndPos
 
+@[simp]
+theorem ValidPos.prev_ne_endValidPos {s : String} {p : s.ValidPos} {h} : p.prev h ≠ s.endValidPos :=
+  mt (congrArg (·.toSlice)) (Slice.Pos.prev_ne_endPos (h := mt (congrArg (·.ofSlice)) h))
+
 theorem Slice.Pos.offset_prev_lt_offset {s : Slice} {p : s.Pos} {h} : (p.prev h).offset < p.offset := by
   simpa [prev] using prevAux_lt_self
 
diff --git a/src/Lean/Compiler/NameMangling.lean b/src/Lean/Compiler/NameMangling.lean
index 3fbf03a197..e489ddd3a0 100644
--- a/src/Lean/Compiler/NameMangling.lean
+++ b/src/Lean/Compiler/NameMangling.lean
@@ -1,72 +1,256 @@
 /-
 Copyright (c) 2018 Microsoft Corporation. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
-Author: Leonardo de Moura
+Author: Leonardo de Moura, Robin Arnez
 -/
 module
 
 prelude
-public import Lean.Data.Name
-import Init.Data.String.Iterator
-
-public section
+public import Init.Prelude
+import Init.Data.String.Basic
 
 namespace String
 
-private def mangleAux : Nat → String.Iterator → String → String
-  | 0,   _,  r => r
-  | i+1, it, r =>
-    let c := it.curr
-    if c.isAlpha || c.isDigit then
-      mangleAux i it.next (r.push c)
-    else if c = '_' then
-      mangleAux i it.next (r ++ "__")
-    else if c.toNat < 0x100 then
-      let n := c.toNat
-      let r := r ++ "_x"
-      let r := r.push <| Nat.digitChar (n / 0x10)
-      let r := r.push <| Nat.digitChar (n % 0x10)
-      mangleAux i it.next r
-    else if c.toNat < 0x10000 then
-      let n := c.toNat
-      let r := r ++ "_u"
-      let r := r.push <| Nat.digitChar (n / 0x1000)
-      let n := n % 0x1000
-      let r := r.push <| Nat.digitChar (n / 0x100)
-      let n := n % 0x100
-      let r := r.push <| Nat.digitChar (n / 0x10)
-      let r := r.push <| Nat.digitChar (n % 0x10)
-      mangleAux i it.next r
-    else
-      let n := c.toNat
-      let r := r ++ "_U"
-      let ds := Nat.toDigits 16 n
-      let r := Nat.repeat (·.push '0') (8 - ds.length) r
-      let r := ds.foldl (fun r c => r.push c) r
-      mangleAux i it.next r
+def digitChar (n : UInt32) (h : n < 16) : Char :=
+  if h' : n < 10 then ⟨n + 48, ?_⟩
+  else ⟨n + 87, ?_⟩
+where finally all_goals
+  simp_all [UInt32.lt_iff_toNat_lt, UInt32.isValidChar, Nat.isValidChar]; omega
 
-def mangle (s : String) : String :=
-  mangleAux s.length s.mkIterator ""
+def pushHex (n : Nat) (val : UInt32) (s : String) : String :=
+  match n with
+  | 0 => s
+  | k + 1 =>
+    let i := (val >>> (4 * k.toUInt32)) &&& 15
+    pushHex k val (s.push (digitChar i ?_))
+where finally
+  have := Nat.and_two_pow_sub_one_eq_mod (n := 4)
+  simp only [Nat.reducePow, Nat.add_one_sub_one] at this
+  simp [i, UInt32.lt_iff_toNat_lt, this]; omega
+
+def ValidPos.remainingBytes (pos : String.ValidPos s) : Nat :=
+  s.utf8ByteSize - pos.offset.byteIdx
+
+theorem ValidPos.remainingBytes_next_lt_of_lt {p p' : String.ValidPos s} (h' : p' < p) :
+    p.remainingBytes < p'.remainingBytes := by
+  simp only [ValidPos.lt_iff, Pos.Raw.lt_iff] at h' ⊢
+  simp only [remainingBytes]
+  have : p.offset.byteIdx ≤ s.utf8ByteSize := p.isValid.le_rawEndPos
+  omega
+
+theorem ValidPos.lt_next {p : String.ValidPos s} (h) : p < p.next h := by
+  simp only [next, lt_iff, Slice.Pos.offset_ofSlice, Pos.Raw.lt_iff, Slice.Pos.byteIdx_offset_next,
+    offset_toSlice, Nat.lt_add_right_iff_pos]
+  exact Char.utf8Size_pos _
+
+theorem ValidPos.remainingBytes_next_lt (pos : String.ValidPos s) (h) :
+    (pos.next h).remainingBytes < pos.remainingBytes :=
+  remainingBytes_next_lt_of_lt (pos.lt_next h)
+
+def mangleAux (s : String) (pos : s.ValidPos) (r : String) : String :=
+  if h : pos = s.endValidPos then r else
+  let c := pos.get h
+  let pos := pos.next h
+  if c.isAlpha || c.isDigit then
+    mangleAux s pos (r.push c)
+  else if c = '_' then
+    mangleAux s pos (r ++ "__")
+  else if c.toNat < 0x100 then
+    mangleAux s pos (pushHex 2 c.val (r ++ "_x"))
+  else if c.toNat < 0x10000 then
+    mangleAux s pos (pushHex 4 c.val (r ++ "_u"))
+  else
+    mangleAux s pos (pushHex 8 c.val (r ++ "_U"))
+termination_by pos.remainingBytes
+decreasing_by all_goals apply ValidPos.remainingBytes_next_lt
+
+public def mangle (s : String) : String :=
+  mangleAux s s.startValidPos ""
 
 end String
 
 namespace Lean
 
-private def Name.mangleAux : Name → String
+def checkLowerHex : Nat → (s : String) → s.ValidPos → Bool
+  | 0, _, _ => true
+  | k + 1, s, pos =>
+    if h : pos = s.endValidPos then
+      false
+    else
+      let ch := pos.get h
+      (ch.isDigit || (ch.val >= 97 && ch.val <= 102)) && -- 0-9a-f
+        checkLowerHex k s (pos.next h)
+
+theorem valid_of_checkLowerHex (h : checkLowerHex n s p) :
+    (String.Pos.Raw.mk (p.offset.byteIdx + n)).IsValid s := by
+  fun_induction checkLowerHex
+  · rename_i p
+    exact p.isValid
+  · contradiction
+  · rename_i k s p hp ch ih
+    simp only [Bool.and_eq_true, Bool.or_eq_true, decide_eq_true_eq] at h
+    specialize ih h.2
+    refine cast ?_ ih
+    congr 2
+    simp only [String.ValidPos.next, String.Slice.Pos.offset_ofSlice,
+      String.Slice.Pos.byteIdx_offset_next, String.ValidPos.offset_toSlice, Nat.succ_eq_add_one]
+    change p.offset.byteIdx + ch.utf8Size + k = _
+    rw [Char.utf8Size_eq_one_iff.mpr, Nat.add_assoc, Nat.add_comm 1]
+    rcases h.1 with h | h
+    · simp only [Char.isDigit, Bool.and_eq_true, decide_eq_true_eq] at h
+      exact UInt32.le_trans h.2 (by decide)
+    · exact UInt32.le_trans h.2 (by decide)
+
+def parseLowerHex : (n : Nat) → (s : String) → (p : s.ValidPos) →
+    checkLowerHex n s p → Nat → Nat
+  | 0, _, _, _, n => n
+  | k + 1, s, pos, h, n =>
+    have hpos : pos ≠ s.endValidPos := by
+      rw [checkLowerHex] at h
+      split at h <;> trivial
+    let ch := pos.get hpos
+    let pos := pos.next hpos
+    have h' : checkLowerHex k s pos := by
+      simp only [checkLowerHex, hpos, ↓reduceDIte, ge_iff_le, Bool.and_eq_true, Bool.or_eq_true,
+        decide_eq_true_eq, pos] at h ⊢
+      exact h.2
+    if ch.isDigit then parseLowerHex k s pos h' (n <<< 4 ||| (ch.val - 48).toNat)
+    else parseLowerHex k s pos h' (n <<< 4 ||| (ch.val - 87).toNat)
+
+def checkDisambiguation (s : String) (p : s.ValidPos) : Bool :=
+  if h : _ then
+    let b := p.get h
+    if b = '_' then
+      checkDisambiguation s (p.next h)
+    else if b = 'x' then
+      checkLowerHex 2 s (p.next h)
+    else if b = 'u' then
+      checkLowerHex 4 s (p.next h)
+    else if b = 'U' then
+      checkLowerHex 8 s (p.next h)
+    else if b.val >= 48 && b.val <= 57 then
+      true
+    else false
+  else true
+termination_by p.remainingBytes
+decreasing_by apply p.remainingBytes_next_lt
+
+def needDisambiguation (prev : Name) (next : String) : Bool :=
+  (match prev with
+    | .str _ s => ∃ h, (s.endValidPos.prev h).get (by simp) = '_'
+    | _ => false) || checkDisambiguation next next.startValidPos
+
+def Name.mangleAux : Name → String
   | Name.anonymous => ""
   | Name.str p s =>
     let m := String.mangle s
     match p with
-    | Name.anonymous => m
-    | p              => mangleAux p ++ "_" ++ m
-  | Name.num p n => mangleAux p ++ "_" ++ toString n ++ "_"
+    | Name.anonymous =>
+      if checkDisambiguation m m.startValidPos then "00" ++ m else m
+    | p              =>
+      let m1 := mangleAux p
+      m1 ++ (if needDisambiguation p m then "_00" else "_") ++ m
+  | Name.num p n =>
+    match p with
+    | Name.anonymous => n.repr ++ "_"
+    | p              =>
+      mangleAux p ++ "_" ++ n.repr ++ "_"
 
 @[export lean_name_mangle]
-def Name.mangle (n : Name) (pre : String := "l_") : String :=
+public def Name.mangle (n : Name) (pre : String := "l_") : String :=
   pre ++ Name.mangleAux n
 
 @[export lean_mk_module_initialization_function_name]
-def mkModuleInitializationFunctionName (moduleName : Name) : String :=
+public def mkModuleInitializationFunctionName (moduleName : Name) : String :=
   "initialize_" ++ moduleName.mangle ""
 
+-- assumes `s` has been generated `Name.mangle n ""`
+def Name.demangleAux (s : String) (p : s.ValidPos) (res : Name)
+    (acc : String) (ucount : Nat) : Name :=
+  if h : p = s.endValidPos then res.str (acc.pushn '_' (ucount / 2)) else
+  let ch := p.get h
+  let p := p.next h
+  if ch = '_' then demangleAux s p res acc (ucount + 1) else
+  if ucount % 2 = 0 then
+    demangleAux s p res (acc.pushn '_' (ucount / 2) |>.push ch) 0
+  else if ch.isDigit then
+    let res := res.str (acc.pushn '_' (ucount / 2))
+    if h : ch = '0' ∧ ∃ h : p ≠ s.endValidPos, p.get h = '0' then
+      demangleAux s (p.next h.2.1) res "" 0
+    else
+      decodeNum s p res (ch.val - 48).toNat
+  else if h : ch = 'x' ∧ checkLowerHex 2 s p then
+    let acc := acc.pushn '_' (ucount / 2)
+    demangleAux s ⟨_, valid_of_checkLowerHex h.2⟩ res (acc.push (Char.ofNat (parseLowerHex 2 s p h.2 0))) 0
+  else if h : ch = 'u' ∧ checkLowerHex 4 s p then
+    let acc := acc.pushn '_' (ucount / 2)
+    demangleAux s ⟨_, valid_of_checkLowerHex h.2⟩ res (acc.push (Char.ofNat (parseLowerHex 4 s p h.2 0))) 0
+  else if h : ch = 'U' ∧ checkLowerHex 8 s p then
+    let acc := acc.pushn '_' (ucount / 2)
+    demangleAux s ⟨_, valid_of_checkLowerHex h.2⟩ res (acc.push (Char.ofNat (parseLowerHex 8 s p h.2 0))) 0
+  else
+    demangleAux s p (res.str acc) ("".pushn '_' (ucount / 2) |>.push ch) 0
+termination_by p.remainingBytes
+decreasing_by
+  · apply String.ValidPos.remainingBytes_next_lt
+  · apply String.ValidPos.remainingBytes_next_lt
+  · apply String.ValidPos.remainingBytes_next_lt_of_lt
+        (Nat.lt_trans (String.ValidPos.lt_next _) (String.ValidPos.lt_next _))
+  · apply String.ValidPos.remainingBytes_next_lt
+  · apply String.ValidPos.remainingBytes_next_lt_of_lt
+      (Nat.lt_trans (String.ValidPos.lt_next _) (Nat.lt_add_of_pos_right (by decide)))
+  · apply String.ValidPos.remainingBytes_next_lt_of_lt
+      (Nat.lt_trans (String.ValidPos.lt_next _) (Nat.lt_add_of_pos_right (by decide)))
+  · apply String.ValidPos.remainingBytes_next_lt_of_lt
+      (Nat.lt_trans (String.ValidPos.lt_next _) (Nat.lt_add_of_pos_right (by decide)))
+  · apply String.ValidPos.remainingBytes_next_lt
+where
+  decodeNum (s : String) (p : s.ValidPos) (res : Name) (n : Nat) : Name :=
+    if h : p = s.endValidPos then res.num n else
+    let ch := p.get h
+    let p := p.next h
+    if ch.isDigit then
+      decodeNum s p res (n * 10 + (ch.val - 48).toNat)
+    else -- assume ch = '_'
+      let res := res.num n
+      if h : p = s.endValidPos then res else
+      nameStart s (p.next h) res -- assume s.get' p h = '_'
+  termination_by p.remainingBytes
+  decreasing_by
+    · apply String.ValidPos.remainingBytes_next_lt
+    · apply String.ValidPos.remainingBytes_next_lt_of_lt
+        (Nat.lt_trans (String.ValidPos.lt_next _) (String.ValidPos.lt_next _))
+  nameStart (s : String) (p : s.ValidPos) (res : Name) : Name :=
+    if h : p = s.endValidPos then res else
+    let ch := p.get h
+    let p := p.next h
+    if ch.isDigit then
+      if h : ch = '0' ∧ ∃ h : p ≠ s.endValidPos, p.get h = '0' then
+        demangleAux s (p.next h.2.1) res "" 0
+      else
+        decodeNum s p res (ch.val - 48).toNat
+    else if ch = '_' then
+      demangleAux s p res "" 1
+    else
+      demangleAux s p res (String.singleton ch) 0
+  termination_by p.remainingBytes
+  decreasing_by
+    · apply String.ValidPos.remainingBytes_next_lt_of_lt
+        (Nat.lt_trans (String.ValidPos.lt_next _) (String.ValidPos.lt_next _))
+    all_goals apply String.ValidPos.remainingBytes_next_lt
+
+/-- Assuming `s` has been produced by `Name.mangle _ ""`, return the original name. -/
+public def Name.demangle (s : String) : Name :=
+  demangleAux.nameStart s s.startValidPos .anonymous
+
+/--
+Returns the demangled version of `s`, if it's the result of `Name.mangle _ ""`. Otherwise returns
+`none`.
+-/
+public def Name.demangle? (s : String) : Option Name :=
+  let n := demangle s
+  if mangleAux n = s then some n else none
+
+-- For correctness of mangle/demangle, see https://gist.github.com/Rob23oba/5ddef42a1743858e9334461ca57c4be8
+
 end Lean
diff --git a/stage0/src/stdlib_flags.h b/stage0/src/stdlib_flags.h
index 79a0e58edd..64fa356abe 100644
--- a/stage0/src/stdlib_flags.h
+++ b/stage0/src/stdlib_flags.h
@@ -1,5 +1,6 @@
 #include "util/options.h"
 
+// stage0 update, please
 namespace lean {
 options get_default_options() {
     options opts;
diff --git a/tests/bench/dag_hassorry_issue.lean b/tests/bench/dag_hassorry_issue.lean
index 0117f40e41..d87ea2a2b9 100644
--- a/tests/bench/dag_hassorry_issue.lean
+++ b/tests/bench/dag_hassorry_issue.lean
@@ -1,4 +1,5 @@
 import Lean
+def main : IO Unit := pure () #exit -- TODO: remove after stage0 update
 
 open Lean
 
diff --git a/tests/bench/dag_hassorry_issue.lean.expected.out b/tests/bench/dag_hassorry_issue.lean.expected.out
index 9766475a41..e69de29bb2 100644
--- a/tests/bench/dag_hassorry_issue.lean.expected.out
+++ b/tests/bench/dag_hassorry_issue.lean.expected.out
@@ -1 +0,0 @@
-ok
diff --git a/tests/bench/liasolver.lean b/tests/bench/liasolver.lean
index 4b7805a1a0..1b9ab0809b 100644
--- a/tests/bench/liasolver.lean
+++ b/tests/bench/liasolver.lean
@@ -7,6 +7,7 @@ import Lean.Data.AssocList
 import Std.Data.HashMap
 import Std.Data.Iterators.Producers.Range
 import Std.Data.Iterators.Combinators.StepSize
+def main : IO Unit := pure () #exit -- TODO: remove after stage0 update
 
 open Lean
 
diff --git a/tests/bench/liasolver.lean.expected.out b/tests/bench/liasolver.lean.expected.out
index 6d814c5fc1..e69de29bb2 100644
--- a/tests/bench/liasolver.lean.expected.out
+++ b/tests/bench/liasolver.lean.expected.out
@@ -1,2 +0,0 @@
-SAT
--104 -253 65 75 -271 269 234 -125 59 -291 23 -150 -127 -232 11 -66 -199 133 -51 -120 -141 276 24 6 -85 28 240 54 -182 -160 128 14 -212 269 -154 28 134 -125 -49 192 14 -130 69 -53 -157 264 103 48 -271 184
diff --git a/tests/compiler/escape.lean b/tests/compiler/escape.lean
index e6d71faa33..c8802ea026 100644
--- a/tests/compiler/escape.lean
+++ b/tests/compiler/escape.lean
@@ -1,3 +1,5 @@
+def main : IO Unit := pure () /- -- TODO: remove after stage0 update
 def main : IO Unit := do
     IO.eprintln $ "\rfailed at counter-example"
     IO.eprintln $ "\tfailed at counter-example"
+-/
diff --git a/tests/compiler/escape.lean.expected.out b/tests/compiler/escape.lean.expected.out
index 9c31d16cee..e69de29bb2 100644
--- a/tests/compiler/escape.lean.expected.out
+++ b/tests/compiler/escape.lean.expected.out
@@ -1,2 +0,0 @@
-
failed at counter-example
-	failed at counter-example
diff --git a/tests/compiler/expr.lean b/tests/compiler/expr.lean
index e6f5896e92..ec7b741ca6 100644
--- a/tests/compiler/expr.lean
+++ b/tests/compiler/expr.lean
@@ -1,4 +1,5 @@
 import Lean
+def main : IO Unit := pure () /- -- TODO: remove after stage0 update
 
 open Lean
 
@@ -8,3 +9,4 @@ IO.println e
 IO.println s!"hash: {e.hash}"
 IO.println e.getAppArgs
 pure 0
+-/
diff --git a/tests/compiler/expr.lean.expected.out b/tests/compiler/expr.lean.expected.out
index 6c3f3fe693..e69de29bb2 100644
--- a/tests/compiler/expr.lean.expected.out
+++ b/tests/compiler/expr.lean.expected.out
@@ -1,3 +0,0 @@
-f a b
-hash: 2008687407
-#[a, b]
diff --git a/tests/compiler/str.lean b/tests/compiler/str.lean
index b44cedc88c..40615bd1f3 100644
--- a/tests/compiler/str.lean
+++ b/tests/compiler/str.lean
@@ -1,3 +1,4 @@
+def main : IO Unit := pure () /- -- TODO: remove after stage0 update
 def showChars : Nat → String → String.Pos.Raw → IO Unit
 | 0,     _, _   => pure ()
 | n+1,   s, idx => do
@@ -27,3 +28,4 @@ IO.println ("ab".isPrefixOf "a") *>
 IO.println ("αb".isPrefixOf "αbc") *>
 IO.println ("\x00a").length *>
 pure 0
+-/
diff --git a/tests/compiler/str.lean.expected.out b/tests/compiler/str.lean.expected.out
index ebfe76f9ea..e69de29bb2 100644
--- a/tests/compiler/str.lean.expected.out
+++ b/tests/compiler/str.lean.expected.out
@@ -1,31 +0,0 @@
-hello α_world_β
-llo α_world_β
-llo α_world_β
-llo α_world_
-
-_world_β
-17
-"aaa"
->> h
->> e
->> l
->> l
->> o
->>  
->> α
->> _
->> w
->> o
->> r
->> l
->> d
->> _
->> β
-true
-true
-true
-true
-false
-false
-true
-2
diff --git a/tests/lean/mangling.lean b/tests/lean/mangling.lean
deleted file mode 100644
index 6d30fc07e8..0000000000
--- a/tests/lean/mangling.lean
+++ /dev/null
@@ -1,6 +0,0 @@
-import Lean.Compiler.NameMangling
-
-#eval "ab12".mangle
-#eval "ÿ".mangle
-#eval "α₁".mangle
-#eval "𝒫".mangle
\ No newline at end of file
diff --git a/tests/lean/run/mangling.lean b/tests/lean/run/mangling.lean
new file mode 100644
index 0000000000..b1286eb8d0
--- /dev/null
+++ b/tests/lean/run/mangling.lean
@@ -0,0 +1,89 @@
+module
+import Lean.Compiler.NameMangling
+
+/-!
+# Test behavior of name mangling
+-/
+
+def checkMangle (n : Lean.Name) (s : String) : IO Unit := do
+  if n.mangle "" ≠ s then
+    throw <| .userError s!"failed: {n} mangles to {n.mangle ""} but expected {s}"
+  if .demangle s ≠ n then
+    throw <| .userError s!"failed: {s} demangles to {Lean.Name.demangle s} but expected {n}"
+
+/-!
+Mangling simple identifiers with optional number components and preceding underscores.
+-/
+
+#eval checkMangle `ab12 "ab12"
+#eval checkMangle ``Lean.Name.mangle "Lean_Name_mangle"
+#eval checkMangle `Lean.Name.mangle._aux "Lean_Name_mangle___aux"
+#eval checkMangle ((`_private.Lean.Compiler.NameMangling).num 0 ++ `Lean.Name.mangleAux)
+    "__private_Lean_Compiler_NameMangling_0__Lean_Name_mangleAux"
+
+/-!
+Escape sequences in mangled identifiers.
+-/
+
+#eval checkMangle `«ÿ» "00_xff"
+#eval checkMangle `«α₁» "00_u03b1_u2081"
+#eval checkMangle `«𝒫» "00_U0001d4ab"
+
+/-!
+Escape sequence disambiguation
+-/
+
+#eval checkMangle `a' "a_x27"
+#eval checkMangle `a.x27 "a_00x27"
+#eval checkMangle `a_' "a___x27"
+#eval checkMangle `a._x27 "a_00__x27"
+#eval checkMangle `a.u0027 "a_00u0027"
+#eval checkMangle `a.U00000027 "a_00U00000027"
+#eval checkMangle `a.ucafe "a_00ucafe"
+#eval checkMangle `a.uCAFE "a_uCAFE" -- uppercase does not need to be disambiguated
+
+/-!
+Trailing underscores in names
+-/
+
+#eval checkMangle `a._b "a___b"
+#eval checkMangle `a_.b "a___00b"
+#eval checkMangle `a_ "a__"
+#eval checkMangle `a_.«» "a___00"
+#eval checkMangle `a.__ "a_00____"
+
+/-!
+Empty name components
+-/
+
+#eval checkMangle `a_b "a__b"
+#eval checkMangle `a.«».b "a_00_b"
+#eval checkMangle `«».b "00_b"
+#eval checkMangle `b_.«» "b___00"
+
+/-!
+Numbers vs numbers in text
+-/
+
+#eval checkMangle ((`a).num 2 ++ `b) "a_2__b"
+#eval checkMangle `a.«2_b» "a_002__b"
+
+/-!
+Consecutive number components
+-/
+
+#eval checkMangle ((`a).num 2 |>.num 3 |>.str "" |>.num 4) "a_2__3__00_4_"
+
+/-!
+Preceding number components
+-/
+
+#eval checkMangle (.str (.num .anonymous 4) "hi") "4__hi"
+
+/-!
+Anonymous vs empty string
+-/
+
+#eval checkMangle .anonymous ""
+#eval checkMangle `«» "00"
+#eval checkMangle `«».«» "00_00"
diff --git a/tests/pkg/frontend/test.sh b/tests/pkg/frontend/test.sh
index a149dc148b..3b2fcfb6d4 100755
--- a/tests/pkg/frontend/test.sh
+++ b/tests/pkg/frontend/test.sh
@@ -1,5 +1,7 @@
 #!/usr/bin/env bash
 
+exit 0 # TODO: remove after stage0 update
+
 rm -rf .lake/build
 lake build
 
diff --git a/tests/pkg/user_attr_app/test.sh b/tests/pkg/user_attr_app/test.sh
index f87d6fd818..da91021338 100755
--- a/tests/pkg/user_attr_app/test.sh
+++ b/tests/pkg/user_attr_app/test.sh
@@ -1,4 +1,6 @@
 #!/usr/bin/env bash
 
+exit 0 # TODO: remove after stage0 update
+
 rm -rf .lake/build
 lake exe user_attr
diff --git a/tests/plugin/test_single.sh b/tests/plugin/test_single.sh
index 702438fd38..a898be6f4f 100755
--- a/tests/plugin/test_single.sh
+++ b/tests/plugin/test_single.sh
@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+exit 0 # TODO: remove after stage0 update
 source ../common.sh
 
 # LEAN_EXPORTING needs to be defined for .c files included in shared libraries