diff --git a/src/Lean/Elab/Do.lean b/src/Lean/Elab/Do.lean
index 2541fb0ea5..8573e6e150 100644
--- a/src/Lean/Elab/Do.lean
+++ b/src/Lean/Elab/Do.lean
@@ -15,29 +15,17 @@ open Meta
 
 namespace Do
 
+/- A `doMatch` alternative. `vars` is the array of variables declared by `patterns`. -/
 structure Alt (σ : Type) :=
-(ref : Syntax) (patterns : Array Syntax) (rhs : σ)
-
-structure VarDecl :=
-(ref : Syntax) (name : Name) (pure : Bool) (letDecl : Syntax)
-
-structure JPDecl (σ : Type) :=
-(ref : Syntax) (name : Name) (params : Array Name) (body : σ)
+(ref : Syntax) (vars : Array Name) (patterns : Array Syntax) (rhs : σ)
 
 /-
-  Auxiliary datastructure for representing a `do` code block.
+  Auxiliary datastructure for representing a `do` code block, and compiling "reassignments" (e.g., `x := x + 1`).
   We convert `Code` into a `Syntax` term representing the:
   - `do`-block, or
   - the visitor argument for the `forIn` combinator.
 
-  We have 2 kinds of declaration
-  - `vdecl`: variable declaration
-  - `jdecl`: join-point declaration
-
-  and actions (e.g., `IO.println "hello"`)
-  - `action`
-
-  We have 6 terminals
+  We say the following constructors are terminals:
   - `break`:    for interrupting a `for x in s`
   - `continue`: for interrupting the current iteration of a `for x in s`
   - `return`:   returning the result of the computation.
@@ -45,23 +33,34 @@ structure JPDecl (σ : Type) :=
   - `match`:    pattern matching
   - `jmp`       a goto to a join-point
 
-  We say `break`, `continue` and `return` are "exit points"
+  We say the terminals `break`, `continue` and `return` are "exit points"
 
   The terminal `return` also contains the name of the variable containing the result of the computation.
   We ignore this value when inside a `for x in s`.
 
+  - `decl` represents all declaration-like `doElem`s (e.g., `let`, `have`, `let rec`). The field `stx` is the actual `doElem`,
+     `vars` is the array of variables declared by it, and `cont` is the next instruction in the `do` code block.
+     `vars` is an array since we have declarations such as `let (a, b) := s`.
+
+  - `reassign` is an reassignment-like `doElem` (e.g., `x := x + 1`).
+
+  - `jointpoint` is a join point declaration: an auxiliary `let`-declaration used to represent the control-flow.
+
+  - `action` is an action-like `doElem` (e.g., `IO.println "hello"`, `dbgTrace! "foo"`).
+
   A code block `C` is well-formed if
-  - For every `jmp r j as` in `C`, there is a `jdecl r j ps b k` s.t. `jmp r j` is in `k`, and
-    `ps.size == as.size`
--/
+  - For every `jmp ref j as` in `C`, there is a `jointpoint j ps b k` and `jmp ref j as` is in `k`, and
+    `ps.size == as.size` -/
 inductive Code
-| vdecl      (decl : VarDecl) (reassignment : Bool) (cont : Code)
-| jdecl      (decl : JPDecl Code) (cont : Code)
-| action     (term : Syntax) (cond : Code)
+| decl       (xs : Array Name) (stx : Syntax) (cont : Code)
+| reassign   (xs : Array Name) (stx : Syntax) (cont : Code)
+| jointpoint (name : Name) (params : Array Name) (body : Code) (cont : Code)
+| action     (stx : Syntax) (cond : Code)
 | «break»    (ref : Syntax)
 | «continue» (ref : Syntax)
-| «return»   (ref : Syntax) (var? : Option Name)
-| ite        (ref : Syntax) (cond : Syntax) (thenBranch : Code) (elseBranch : Code)
+| «return»   (ref : Syntax) (x? : Option Name)
+/- Recall that an if-then-else may declare a variable using `optIdent` for the branches `thenBranch` and `elseBranch`. We store the variable name at `var?`. -/
+| ite        (ref : Syntax) (h? : Option Name) (optIdent : Syntax) (cond : Syntax) (thenBranch : Code) (elseBranch : Code)
 | «match»    (ref : Syntax) (discrs : Array Syntax) (type? : Option Syntax) (alts : Array (Alt Code))
 | jmp        (ref : Syntax) (jpName : Name) (args : Array Name)
 
@@ -69,20 +68,24 @@ instance Code.inhabited : Inhabited Code :=
 ⟨Code.«break» (arbitrary _)⟩
 
 instance Alt.inhabited : Inhabited (Alt Code) :=
-⟨{ ref := arbitrary _, patterns := #[], rhs := arbitrary _ }⟩
+⟨{ ref := arbitrary _, vars := #[], patterns := #[], rhs := arbitrary _ }⟩
 
 /- A code block, and the collection of variables updated by it. -/
 structure CodeBlock :=
 (code  : Code)
 (uvars : NameSet := {}) -- set of variables updated by `code`
 
+private def varsToMessageData (vars : Array Name) : MessageData :=
+MessageData.joinSep (vars.toList.map fun n => MessageData.ofName (n.simpMacroScopes)) " "
+
 partial def toMessageDataAux (updateVars : MessageData) : Code → MessageData
-| Code.vdecl d r k          =>
-  (if r then "" else "let ") ++ d.name ++ " " ++ (if d.pure then ":=" else "←") ++ " ... " ++ Format.line ++ toMessageDataAux k
-| Code.jdecl d k            =>
-  "let " ++ d.name.simpMacroScopes ++ " " ++ toString d.params.toList ++ ":=" ++ indentD (toMessageDataAux d.body) ++ Format.line ++ toMessageDataAux k
+| Code.decl xs _ k            => "let " ++ varsToMessageData xs ++ " := ... " ++ Format.line ++ toMessageDataAux k
+| Code.reassign xs _ k        => varsToMessageData xs ++ " := ... " ++ Format.line ++ toMessageDataAux k
+| Code.jointpoint n ps body k =>
+  "let " ++ n.simpMacroScopes ++ " " ++ varsToMessageData ps ++ " := " ++ indentD (toMessageDataAux body)
+  ++ Format.line ++ toMessageDataAux k
 | Code.action e k           => e ++ Format.line ++ toMessageDataAux k
-| Code.ite _ c t e          => "if " ++ c ++ " then " ++ indentD (toMessageDataAux t) ++ Format.line ++ "else " ++ indentD (toMessageDataAux e)
+| Code.ite _ _ _ c t e      => "if " ++ c ++ " then " ++ indentD (toMessageDataAux t) ++ Format.line ++ "else " ++ indentD (toMessageDataAux e)
 | Code.jmp _ j xs           => "jmp " ++ j.simpMacroScopes ++ " " ++ toString xs.toList
 | Code.«break» _            => "break " ++ updateVars
 | Code.«continue» _         => "continue " ++ updateVars
@@ -104,22 +107,12 @@ def CodeBlock.toMessageData (c : CodeBlock) : MessageData :=
 let us := (nameSetToArray c.uvars).toList.map MessageData.ofName;
 toMessageDataAux (MessageData.ofList us) c.code
 
-partial def getSomeRef : Code → Syntax
-| Code.vdecl d _ _       => d.ref
-| Code.jdecl d _         => d.ref
-| Code.action e _        => e
-| Code.ite ref _ _ _     => ref
-| Code.jmp ref _ _       => ref
-| Code.«break» ref       => ref
-| Code.«continue» ref    => ref
-| Code.«return» ref _    => ref
-| Code.«match» ref _ _ _ => ref
-
 partial def hasExitPoint : Code → Bool
-| Code.vdecl _ _ k        => hasExitPoint k
-| Code.jdecl d k          => hasExitPoint d.body || hasExitPoint k
+| Code.decl _ _ k         => hasExitPoint k
+| Code.reassign _ _ k     => hasExitPoint k
+| Code.jointpoint _ _ b k => hasExitPoint b || hasExitPoint k
 | Code.action _ k         => hasExitPoint k
-| Code.ite _ _ t e        => hasExitPoint t || hasExitPoint e
+| Code.ite _ _ _ _ t e    => hasExitPoint t || hasExitPoint e
 | Code.jmp _ _ _          => false
 | Code.«break» _          => true
 | Code.«continue» _       => true
@@ -127,10 +120,11 @@ partial def hasExitPoint : Code → Bool
 | Code.«match» _ _ _ alts => alts.any fun alt => hasExitPoint alt.rhs
 
 partial def convertReturnIntoJmpAux (jp : Name) (xs : Array Name) : Code → Code
-| Code.vdecl d r k           => Code.vdecl d r $ convertReturnIntoJmpAux k
-| Code.jdecl d k             => Code.jdecl { d with body := convertReturnIntoJmpAux d.body } $ convertReturnIntoJmpAux k
+| Code.decl xs stx k         => Code.decl xs stx $ convertReturnIntoJmpAux k
+| Code.reassign xs stx k     => Code.reassign xs stx $ convertReturnIntoJmpAux k
+| Code.jointpoint n ps b k   => Code.jointpoint n ps (convertReturnIntoJmpAux b) (convertReturnIntoJmpAux k)
 | Code.action e k            => Code.action e $ convertReturnIntoJmpAux k
-| Code.ite ref c t e         => Code.ite ref c (convertReturnIntoJmpAux t) (convertReturnIntoJmpAux e)
+| Code.ite ref x? h c t e    => Code.ite ref x? h c (convertReturnIntoJmpAux t) (convertReturnIntoJmpAux e)
 | Code.«match» ref ds t alts => Code.«match» ref ds t $ alts.map fun alt => { alt with rhs := convertReturnIntoJmpAux alt.rhs }
 | Code.«return» ref _        => Code.jmp ref jp xs
 | c                          => c
@@ -139,30 +133,48 @@ partial def convertReturnIntoJmpAux (jp : Name) (xs : Array Name) : Code → Cod
 def convertReturnIntoJmp (c : Code) (jp : Name) (xs : Array Name) : Code :=
 convertReturnIntoJmpAux jp xs c
 
-def mkJPDecls (jpDecls : Array (JPDecl Code)) (k : Code) : Code :=
-jpDecls.foldr (fun jp r => Code.jdecl jp r) k
+structure JPDecl :=
+(name : Name) (params : Array Name) (body : Code)
 
-def mkFreshJP (ref : Syntax) (ps : Array Name) (body : Code) : TermElabM (JPDecl Code) := do
+def attachJP (jpDecl : JPDecl) (k : Code) : Code :=
+Code.jointpoint jpDecl.name jpDecl.params jpDecl.body k
+
+def attachJPs (jpDecls : Array JPDecl) (k : Code) : Code :=
+jpDecls.foldr attachJP k
+
+def mkFreshJP (ps : Array Name) (body : Code) : TermElabM JPDecl := do
 name ← mkFreshUserName `jp;
-pure { ref := ref, name := name, params := ps, body := body }
+pure { name := name, params := ps, body := body }
 
-def addFreshJP (ref : Syntax) (ps : Array Name) (body : Code) : StateRefT (Array (JPDecl Code)) TermElabM Name := do
-jp ← liftM $ mkFreshJP ref ps body;
-modify fun (jps : Array (JPDecl Code)) => jps.push jp;
+def addFreshJP (ps : Array Name) (body : Code) : StateRefT (Array JPDecl) TermElabM Name := do
+jp ← liftM $ mkFreshJP ps body;
+modify fun (jps : Array JPDecl) => jps.push jp;
 pure jp.name
 
+def insertVars (rs : NameSet) (xs : Array Name) : NameSet :=
+xs.foldl (fun (rs : NameSet) x => rs.insert x) rs
+
+def eraseVars (rs : NameSet) (xs : Array Name) : NameSet :=
+xs.foldl (fun (rs : NameSet) x => rs.erase x) rs
+
+def eraseOptVar (rs : NameSet) (x? : Option Name) : NameSet :=
+match x? with
+| none   => rs
+| some x => rs.insert x
+
 /- `pullExitPointsAux rs c` auxiliary method for `pullExitPoints`, `rs` is the set of update variable in the current path.  -/
-partial def pullExitPointsAux : NameSet → Code → StateRefT (Array (JPDecl Code)) TermElabM Code
-| rs, Code.vdecl d false k   => Code.vdecl d false <$> pullExitPointsAux (rs.erase d.name) k
-| rs, Code.vdecl d true k    => Code.vdecl d true <$> pullExitPointsAux (rs.insert d.name) k
-| rs, Code.jdecl d k         => do b ← pullExitPointsAux rs d.body; Code.jdecl { d with body := b } <$> pullExitPointsAux rs k
-| rs, Code.action e k        => Code.action e <$> pullExitPointsAux rs k
-| rs, Code.ite ref c t e     => Code.ite ref c <$> pullExitPointsAux rs t <*> pullExitPointsAux rs e
-| rs, Code.«match» ref ds t alts => Code.«match» ref ds t <$> alts.mapM fun alt => do rhs ← pullExitPointsAux rs alt.rhs; pure { alt with rhs := rhs }
+partial def pullExitPointsAux : NameSet → Code → StateRefT (Array JPDecl) TermElabM Code
+| rs, Code.decl xs stx k         => Code.decl xs stx <$> pullExitPointsAux (eraseVars rs xs) k
+| rs, Code.reassign xs stx k     => Code.reassign xs stx <$> pullExitPointsAux (insertVars rs xs) k
+| rs, Code.jointpoint j ps b k   => Code.jointpoint j ps <$> pullExitPointsAux rs b <*> pullExitPointsAux rs k
+| rs, Code.action e k            => Code.action e <$> pullExitPointsAux rs k
+| rs, Code.ite ref x? o c t e    => Code.ite ref x? o c <$> pullExitPointsAux (eraseOptVar rs x?) t <*> pullExitPointsAux (eraseOptVar rs x?) e
+| rs, Code.«match» ref ds t alts => Code.«match» ref ds t <$> alts.mapM fun alt => do
+  rhs ← pullExitPointsAux (eraseVars rs alt.vars) alt.rhs; pure { alt with rhs := rhs }
 | rs, c@(Code.jmp _ _ _)     => pure c
-| rs, Code.«break» ref       => do let xs := nameSetToArray rs; jp ← addFreshJP ref xs (Code.«break» ref); pure $ Code.jmp ref jp xs
-| rs, Code.«continue» ref    => do let xs := nameSetToArray rs; jp ← addFreshJP ref xs (Code.«continue» ref); pure $ Code.jmp ref jp xs
-| rs, Code.«return» ref y?   => do
+| rs, Code.«break» ref           => do let xs := nameSetToArray rs; jp ← addFreshJP xs (Code.«break» ref); pure $ Code.jmp ref jp xs
+| rs, Code.«continue» ref        => do let xs := nameSetToArray rs; jp ← addFreshJP xs (Code.«continue» ref); pure $ Code.jmp ref jp xs
+| rs, Code.«return» ref y?       => do
   let xs := nameSetToArray rs;
   (ps, xs) ← match y? with
     | none   => pure (xs, xs)
@@ -172,7 +184,7 @@ partial def pullExitPointsAux : NameSet → Code → StateRefT (Array (JPDecl Co
         yFresh ← mkFreshUserName y;
         pure (xs.push y, xs.push yFresh)
       };
-  jp ← addFreshJP ref ps (Code.«return» ref y?);
+  jp ← addFreshJP ps (Code.«return» ref y?);
   pure $ Code.jmp ref jp xs
 
 /-
@@ -227,23 +239,35 @@ We implement the method as follows. Let `us` be `c.uvars`, then
 def pullExitPoints (c : Code) : TermElabM Code :=
 if hasExitPoint c then do
   (c, jpDecls) ← (pullExitPointsAux {} c).run #[];
-  pure $ mkJPDecls jpDecls c
+  pure $ attachJPs jpDecls c
 else
   pure c
 
 partial def extendUpdatedVarsAux (ws : NameSet) : Code → TermElabM Code
-| Code.jdecl d k             => do b ← extendUpdatedVarsAux d.body; Code.jdecl { d with body := b } <$> extendUpdatedVarsAux k
-| Code.action e k            => Code.action e <$> extendUpdatedVarsAux k
-| Code.ite ref c t e         => Code.ite ref c <$> extendUpdatedVarsAux t <*> extendUpdatedVarsAux e
-| Code.«match» ref ds t alts => Code.«match» ref ds t <$> alts.mapM fun alt => do rhs ← extendUpdatedVarsAux alt.rhs; pure { alt with rhs := rhs }
-| Code.vdecl d true k        => Code.vdecl d true <$> extendUpdatedVarsAux k
-| c@(Code.vdecl d false k)   =>
-  if ws.contains d.name then
-    -- This `let` declaration is shadowing a variable in ws
+| Code.jointpoint j ps b k       => Code.jointpoint j ps <$> extendUpdatedVarsAux b <*> extendUpdatedVarsAux k
+| Code.action e k                => Code.action e <$> extendUpdatedVarsAux k
+| c@(Code.«match» ref ds t alts) =>
+  if alts.any fun alt => alt.vars.any fun x => ws.contains x then
+    -- If a pattern variable is shadowing a variable in ws, we `pullExitPoints`
     pullExitPoints c
   else
-    Code.vdecl d false <$> extendUpdatedVarsAux k
-| c                          => pure c
+    Code.«match» ref ds t <$> alts.mapM fun alt => do rhs ← extendUpdatedVarsAux alt.rhs; pure { alt with rhs := rhs }
+| Code.ite ref none o c t e =>
+  Code.ite ref none o c <$> extendUpdatedVarsAux t <*> extendUpdatedVarsAux e
+| c@(Code.ite ref (some h) o cond t e) =>
+  if ws.contains h then
+    -- if the `h` at `if h:c then t else e` shadows a variable in `ws`, we `pullExitPoints`
+    pullExitPoints c
+  else
+    Code.ite ref (some h) o cond <$> extendUpdatedVarsAux t <*> extendUpdatedVarsAux e
+| Code.reassign xs stx k => Code.reassign xs stx <$> extendUpdatedVarsAux k
+| c@(Code.decl xs stx k) =>
+  if xs.any fun x => ws.contains x then
+    -- One the declared variables is shadowing a variable in `ws`
+    pullExitPoints c
+  else
+    Code.decl xs stx <$> extendUpdatedVarsAux k
+| c => pure c
 
 /-
 Extend the set of updated variables. It assumes `ws` is a super set of `c.uvars`.
@@ -275,21 +299,26 @@ pure (c₁, c₂)
 /-
 Extending code blocks with variable declarations: `let x : t := v` and `let x : t ← v`.
 We remove `x` from the collection of updated varibles.
+Remark: `stx` is the syntax for the declaration (e.g., `letDecl`), and `xs` are the variables
+declared by it. It is an array because we have let-declarations that declare multiple variables.
+Example: `let (x, y) := t`
 -/
-def mkVarDecl (d : VarDecl) (c : CodeBlock) : CodeBlock :=
-let x := d.name;
-{ code := Code.vdecl d false c.code, uvars := c.uvars.erase x }
+def mkVarDeclCore (xs : Array Name) (stx : Syntax) (c : CodeBlock) : CodeBlock :=
+{ code := Code.decl xs stx c.code, uvars := eraseVars c.uvars xs }
 
 /-
 Extending code blocks with reassignments: `x : t := v` and `x : t ← v`.
+Remark: `stx` is the syntax for the declaration (e.g., `letDecl`), and `xs` are the variables
+declared by it. It is an array because we have let-declarations that declare multiple variables.
+Example: `(x, y) ← t`
 -/
-def mkReassign (d : VarDecl) (c : CodeBlock) : TermElabM CodeBlock := do
-let x  := d.name;
-let ws := c.uvars.insert x;
--- We must pull "exit points" IF `x` is not in `c.uvars`, but is shadowed by a declaration in `c`
+def mkReassignCore (xs : Array Name) (stx : Syntax) (c : CodeBlock) : TermElabM CodeBlock := do
+let us := c.uvars;
+let ws := insertVars us xs;
+-- If `xs` contains a new updated variable, then we must use `extendUpdatedVars`.
 -- See discussion at `pullExitPoints`
-code ← if !c.uvars.contains x then extendUpdatedVarsAux ws c.code else pure c.code;
-pure { code := Code.vdecl d true code, uvars := ws }
+code ← if xs.any fun x => !us.contains x then extendUpdatedVarsAux ws c.code else pure c.code;
+pure { code := Code.reassign xs stx code, uvars := ws }
 
 def mkAction (action : Syntax) (c : CodeBlock) : CodeBlock :=
 { c with code := Code.action action c.code }
@@ -303,10 +332,11 @@ def mkBreak (ref : Syntax) : CodeBlock :=
 def mkContinue (ref : Syntax) : CodeBlock :=
 { code := Code.«continue» ref }
 
-def mkIte (ref : Syntax) (c : Syntax) (thenBranch : CodeBlock) (elseBranch : CodeBlock) : TermElabM CodeBlock := do
+def mkIte (ref : Syntax) (optIdent : Syntax) (cond : Syntax) (thenBranch : CodeBlock) (elseBranch : CodeBlock) : TermElabM CodeBlock := do
+let x? := if optIdent.isNone then none else some (optIdent.getArg 0).getId;
 (thenBranch, elseBranch) ← homogenize thenBranch elseBranch;
 pure {
-  code  := Code.ite ref c thenBranch.code elseBranch.code,
+  code  := Code.ite ref x? optIdent cond thenBranch.code elseBranch.code,
   uvars := thenBranch.uvars,
 }
 
@@ -315,18 +345,18 @@ pure {
 def concat (terminal : CodeBlock) (k : CodeBlock) : TermElabM CodeBlock := do
 (terminal, k) ← homogenize terminal k;
 let xs := nameSetToArray k.uvars;
-jpDecl ← mkFreshJP (getSomeRef k.code) xs k.code;
+jpDecl ← mkFreshJP xs k.code;
 let jp := jpDecl.name;
 pure {
-  code  := Code.jdecl jpDecl (convertReturnIntoJmp terminal.code jp xs),
+  code  := attachJP jpDecl (convertReturnIntoJmp terminal.code jp xs),
   uvars := terminal.uvars,
 }
 
 def mkWhen (ref : Syntax) (cond : Syntax) (c : CodeBlock) : CodeBlock :=
-{ c with code := Code.ite ref cond c.code (Code.«return» ref none) }
+{ c with code := Code.ite ref none mkNullNode cond c.code (Code.«return» ref none) }
 
 def mkUnless (ref : Syntax) (cond : Syntax) (c : CodeBlock) : CodeBlock :=
-{ c with code := Code.ite ref cond (Code.«return» ref none) c.code }
+{ c with code := Code.ite ref none mkNullNode cond (Code.«return» ref none) c.code }
 
 private def mkTuple (elems : Array Syntax) : MacroM Syntax :=
 if elems.size == 1 then pure (elems.get! 0)
diff --git a/tests/lean/run/doCodeBlock.lean b/tests/lean/run/doCodeBlock.lean
index b35ec87b90..4b6b287778 100644
--- a/tests/lean/run/doCodeBlock.lean
+++ b/tests/lean/run/doCodeBlock.lean
@@ -6,8 +6,11 @@ namespace Lean.Elab.Term.Do
 
 def ref := Syntax.missing
 
-def vdecl (name : Name) (pure := true) : VarDecl :=
-{ ref := ref, name := name, pure := pure, letDecl := Syntax.missing }
+def mkVarDecl (x : Name) (k : CodeBlock) : CodeBlock :=
+mkVarDeclCore #[x] Syntax.missing k
+
+def mkReassign (x : Name) (k : CodeBlock) : TermElabM CodeBlock :=
+mkReassignCore #[x] Syntax.missing k
 
 def print (c : CodeBlock) : TermElabM Unit := do
 let msg := c.toMessageData
@@ -17,14 +20,14 @@ pure ()
 
 def tst : TermElabM Unit := do
 let x := mkIdentFrom ref `x
-let c ← mkIte ref (← `($x < 1))
-  (mkVarDecl (vdecl `w) (mkVarDecl (vdecl `z) (← mkReassign (vdecl `x) (mkReturn ref))))
-  (mkVarDecl (vdecl `x) (← mkReassign (vdecl `y) (mkBreak ref)))
+let c ← mkIte ref mkNullNode (← `($x < 1))
+  (mkVarDecl `w (mkVarDecl `z (← mkReassign `x (mkReturn ref))))
+  (mkVarDecl `x (← mkReassign `y (mkBreak ref)))
 print c
 IO.println "-----"
-let c ← concat c (mkVarDecl (vdecl `w) (← mkReassign (vdecl `z) (mkReturn ref)))
+let c ← concat c (mkVarDecl `w (← mkReassign `z (mkReturn ref)))
 print c
-let c ← mkReassign (vdecl `w) c
+let c ← mkReassign `w c
 IO.println "-----"
 print c
 pure ()