From f44a7882a1d4a538ec90ccef291ac12c63625742 Mon Sep 17 00:00:00 2001
From: Sebastian Ullrich <sebasti@nullri.ch>
Date: Thu, 28 Mar 2019 17:32:14 +0100
Subject: [PATCH] refactor(library/init/lean/): store Syntax.node children in
 array

---
 library/init/data/array/basic.lean        | 53 ++++++++++++++++-
 library/init/lean/elaborator.lean         |  6 +-
 library/init/lean/expander.lean           |  4 +-
 library/init/lean/parser/combinators.lean | 72 +++++++++++------------
 library/init/lean/parser/module.lean      |  2 +-
 library/init/lean/parser/syntax.lean      | 24 +++++---
 library/init/lean/parser/term.lean        |  2 +-
 library/init/lean/parser/token.lean       |  9 +--
 src/frontends/lean/elaborator.cpp         | 20 +++----
 9 files changed, 123 insertions(+), 69 deletions(-)

diff --git a/library/init/data/array/basic.lean b/library/init/data/array/basic.lean
index 09dcd6fc3e60..1c225007fd2c 100644
--- a/library/init/data/array/basic.lean
+++ b/library/init/data/array/basic.lean
@@ -46,9 +46,15 @@ mkEmpty ()
 instance : HasEmptyc (Array α) :=
 ⟨Array.empty⟩
 
+instance : Inhabited (Array α) :=
+⟨Array.empty⟩
+
 def isEmpty (a : Array α) : Bool :=
 a.size = 0
 
+def singleton (v : α) : Array α :=
+mkArray 1 v
+
 @[extern cpp inline "lean::array_index(#2, #3)"]
 def index (a : @& Array α) (i : @& Fin a.sz) : α :=
 a.data i
@@ -65,6 +71,9 @@ a.index ⟨i.toNat, h⟩
 def get [Inhabited α] (a : @& Array α) (i : @& Nat) : α :=
 if h : i < a.sz then a.index ⟨i, h⟩ else default α
 
+def oget (a : @& Array α) (i : @& Nat) : Option α :=
+if h : i < a.size then some (a.index ⟨i, h⟩) else none
+
 @[extern cpp inline "lean::array_update(#2, #3, #4)"]
 def update (a : Array α) (i : @& Fin a.sz) (v : α) : Array α :=
 { sz   := a.sz,
@@ -111,6 +120,25 @@ iterateAux a f 0 b
 @[inline] def foldl (a : Array α) (f : α → β → β) (b : β) : β :=
 iterate a b (λ _, f)
 
+section
+variables {m : Type v → Type v} [Monad m] [Inhabited β]
+local attribute [instance] monadInhabited
+
+-- TODO(Leo): justify termination using wf-rec
+@[specialize] partial def miterateAux (a : Array α) (f : Π i : Fin a.sz, α → β → m β) : Nat → β → m β
+| i b :=
+  if h : i < a.sz then
+     let idx : Fin a.sz := ⟨i, h⟩ in
+     f idx (a.index idx) b >>= miterateAux (i+1)
+  else pure b
+
+@[inline] def miterate (a : Array α) (b : β) (f : Π i : Fin a.sz, α → β → m β) : m β :=
+miterateAux a f 0 b
+
+@[inline] def mfoldl (a : Array α) (b : β) (f : α → β → m β) : m β :=
+miterate a b (λ _, f)
+end
+
 @[specialize] private def revIterateAux (a : Array α) (f : Π i : Fin a.sz, α → β → β) : Π (i : Nat), i ≤ a.sz → β → β
 | 0     h b := b
 | (j+1) h b :=
@@ -151,11 +179,32 @@ if h : a.size ≤ b.size
 then foreach a (λ ⟨i, h'⟩, f (b.index ⟨i, Nat.ltOfLtOfLe h' h⟩))
 else foreach b (λ ⟨i, h'⟩, f (a.index ⟨i, Nat.ltTrans h' (Nat.gtOfNotLe h)⟩))
 
+section
+variables {m : Type u → Type u} [Monad m]
+local attribute [instance] monadInhabited
+
+def mforeachAuxInh (a : Array α) : Inhabited { a' : Array α // a'.sz = a.sz } :=
+⟨⟨a, rfl⟩⟩
+local attribute [instance] mforeachAuxInh
+
+@[inline] private def mforeachAux (a : Array α) (f : Π i : Fin a.sz, α → m α) : m { a' : Array α // a'.sz = a.sz } :=
+miterate a ⟨a, rfl⟩ $ λ i v ⟨a', h⟩, do
+  let i' : Fin a'.sz := Eq.recOn h.symm i,
+  x ← f i v,
+  pure $ ⟨a'.update i' x, (szUpdateEq a' i' x) ▸ h⟩
+
+@[inline] def mforeach (a : Array α) (f : Π i : Fin a.sz, α → m α) : m (Array α) :=
+Subtype.val <$> mforeachAux a f
+
+@[inline] def mmap (f : α → m α) (a : Array α) : m (Array α) :=
+mforeach a (λ _, f)
+end
+
 end Array
 
-def List.toArrayAux {α : Type u} : List α → Array α → Array α
+@[inlineIfReduce] def List.toArrayAux {α : Type u} : List α → Array α → Array α
 | []      r := r
 | (a::as) r := List.toArrayAux as (r.push a)
 
-def List.toArray {α : Type u} (l : List α) : Array α :=
+@[inline] def List.toArray {α : Type u} (l : List α) : Array α :=
 l.toArrayAux ∅
diff --git a/library/init/lean/elaborator.lean b/library/init/lean/elaborator.lean
index 9ea22928f9b2..1e125f22f339 100644
--- a/library/init/lean/elaborator.lean
+++ b/library/init/lean/elaborator.lean
@@ -282,9 +282,9 @@ partial def toPexpr : Syntax → ElaboratorM Expr
     let v := view stringLit stx,
     pure $ Expr.lit $ Literal.strVal (v.value.getOrElse "NOTAString")
   | @choice := do
-    last::rev ← List.reverse <$> args.mmap (λ a, toPexpr a)
+    last::rev ← List.reverse <$> args.toList.mmap (λ a, toPexpr a)
       | error stx "ill-formed choice",
-    pure $ Expr.mdata (MData.empty.setNat `choice args.length) $
+    pure $ Expr.mdata (MData.empty.setNat `choice args.size) $
       rev.reverse.foldr Expr.app last
   | @structInst := do
     let v := view structInst stx,
@@ -856,7 +856,7 @@ def setOption.elaborate : Elaborator :=
 def noKind.elaborate : Elaborator := λ stx, do
   some n ← pure stx.asNode
     | error stx "noKind.elaborate: unreachable",
-  n.args.mmap' command.elaborate
+  n.args.toList.mmap' command.elaborate
 
 def end.elaborate : Elaborator :=
 λ cmd, do
diff --git a/library/init/lean/expander.lean b/library/init/lean/expander.lean
index a377bf2e8c88..55206232ea5b 100644
--- a/library/init/lean/expander.lean
+++ b/library/init/lean/expander.lean
@@ -113,7 +113,7 @@ def mkNotationTransformer (nota : NotationMacro) : transformer :=
 λ stx, do
   some {args := stxArgs, ..} ← pure stx.asNode
     | error stx "mkNotationTransformer: unreachable",
-  flip StateT.run' {NotationTransformerState . stx := stx, stxArgs := stxArgs} $ do
+  flip StateT.run' {NotationTransformerState . stx := stx, stxArgs := stxArgs.toList} $ do
     let spec := nota.nota.spec,
     -- Walk through the notation specification, consuming `stx` args and building up substitutions
     -- for the notation RHS.
@@ -471,7 +471,7 @@ def Subtype.transform : transformer :=
 def universes.transform : transformer :=
 λ stx, do
   let v := view «universes» stx,
-  pure $ Syntax.list $ v.ids.map (λ id, review «universe» {id := id})
+  pure $ Syntax.list $ List.toArray $ v.ids.map (λ id, review «universe» {id := id})
 
 def sorry.transform : transformer :=
 λ stx, pure $ mkApp (globId `sorryAx) [review hole {}, globId `Bool.false]
diff --git a/library/init/lean/parser/combinators.lean b/library/init/lean/parser/combinators.lean
index 1a9a801f1dd6..7626f4ae2f33 100644
--- a/library/init/lean/parser/combinators.lean
+++ b/library/init/lean/parser/combinators.lean
@@ -20,17 +20,17 @@ local notation `Parser` := m Syntax
 variables [Monad m] [MonadExcept (Parsec.Message Syntax) m] [MonadParsec Syntax m] [Alternative m]
 
 def node (k : SyntaxNodeKind) (rs : List Parser) : Parser :=
-do args ← rs.mfoldl (λ (args : List Syntax) r, do
+do args ← rs.mfoldl (λ (args : Array Syntax) r, do
      -- on error, append partial Syntax tree to previous successful parses and rethrow
-     a ← catch r $ λ msg, match args with
-       -- do not wrap an error in the first argument to uphold the invariant documented at `SyntaxNode`
-       | [] := throw msg
-       | _  :=
-         let args := msg.custom.get :: args in
-         throw {msg with custom := Syntax.mkNode k args.reverse},
-     pure (a::args)
-   ) [],
-   pure $ Syntax.mkNode k args.reverse
+     a ← catch r $ λ msg, if args.isEmpty then
+         -- do not wrap an error in the first argument to uphold the invariant documented at `SyntaxNode`
+         throw msg
+       else
+         let args := args.push msg.custom.get in
+         throw {msg with custom := Syntax.mkNode k args},
+     pure $ args.push a
+   ) Array.empty,
+   pure $ Syntax.mkNode k args
 
 @[reducible] def seq : List Parser → Parser := node noKind
 
@@ -42,28 +42,29 @@ instance node.view (k) (rs : List Parser) [i : HasView α k] : Parser.HasView α
 
 -- Each Parser Combinator comes equipped with `HasView` and `HasTokens` instances
 
-private def many1Aux (p : Parser) : List Syntax → Nat → Parser
+private def many1Aux (p : Parser) : Array Syntax → Nat → Parser
 | as 0     := error "unreachable"
 | as (n+1) := do
   a ← catch p (λ msg, throw {msg with custom :=
     -- append `Syntax.missing` to make clear that List is incomplete
-    Syntax.list (Syntax.missing::msg.custom.get::as).reverse}),
-  many1Aux (a::as) n <|> pure (Syntax.list (a::as).reverse)
+    Syntax.list $ (as.push msg.custom.get).push Syntax.missing}),
+  many1Aux (as.push a) n <|> pure (Syntax.list $ as.push a)
 
 def many1 (r : Parser) : Parser :=
-do rem ← remaining, many1Aux r [] (rem+1)
+do rem ← remaining, many1Aux r Array.empty (rem+1)
 
 instance many1.tokens (r : Parser) [Parser.HasTokens r] : Parser.HasTokens (many1 r) :=
 ⟨tokens r⟩
 
+--TODO(Sebastian): should this be an `Array` as well?
 instance many1.view (r : Parser) [Parser.HasView α r] : Parser.HasView (List α) (many1 r) :=
 { view := λ stx, match stx.asNode with
-    | some n := n.args.map (HasView.view r)
+    | some n := n.args.toList.map (HasView.view r)
     | _ := [HasView.view r Syntax.missing],
-  review := λ as, Syntax.list $ as.map (review r) }
+  review := λ as, Syntax.list $ List.toArray $ as.map (review r) }
 
 def many (r : Parser) : Parser :=
-many1 r <|> pure (Syntax.list [])
+many1 r <|> pure (Syntax.list Array.empty)
 
 instance many.tokens (r : Parser) [Parser.HasTokens r] : Parser.HasTokens (many r) :=
 ⟨tokens r⟩
@@ -72,25 +73,25 @@ instance many.view (r : Parser) [HasView α r] : Parser.HasView (List α) (many
 /- Remark: `many1.view` can handle empty list. -/
 {..many1.view r}
 
-private def sepByAux (p : m Syntax) (sep : Parser) (allowTrailingSep : Bool) : Bool → List Syntax → Nat → Parser
+private def sepByAux (p : m Syntax) (sep : Parser) (allowTrailingSep : Bool) : Bool → Array Syntax → Nat → Parser
 | pOpt as 0     := error "unreachable"
 | pOpt as (n+1) := do
   let p := if pOpt then some <$> p <|> pure none else some <$> p,
   some a ← catch p (λ msg, throw {msg with custom :=
     -- append `Syntax.missing` to make clear that List is incomplete
-    Syntax.list (Syntax.missing::msg.custom.get::as).reverse})
-    | pure (Syntax.list as.reverse),
+    Syntax.list $ (as.push msg.custom.get).push Syntax.missing})
+    | pure (Syntax.list as),
   -- I don't want to think about what the output on a failed separator parse should look like
   let sep := try sep,
   some s ← some <$> sep <|> pure none
-    | pure (Syntax.list (a::as).reverse),
-  sepByAux allowTrailingSep (s::a::as) n
+    | pure (Syntax.list (as.push a)),
+  sepByAux allowTrailingSep ((as.push s).push a) n
 
 def sepBy (p sep : Parser) (allowTrailingSep := true) : Parser :=
-do rem ← remaining, sepByAux p sep allowTrailingSep true [] (rem+1)
+do rem ← remaining, sepByAux p sep allowTrailingSep true Array.empty (rem+1)
 
 def sepBy1 (p sep : Parser) (allowTrailingSep := true) : Parser :=
-do rem ← remaining, sepByAux p sep allowTrailingSep false [] (rem+1)
+do rem ← remaining, sepByAux p sep allowTrailingSep false Array.empty (rem+1)
 
 instance sepBy.tokens (p sep : Parser) (a) [Parser.HasTokens p] [Parser.HasTokens sep] :
   Parser.HasTokens (sepBy p sep a) :=
@@ -112,9 +113,9 @@ private def sepBy.viewAux {α β} (p sep : Parser) [Parser.HasView α p] [Parser
 instance sepBy.view {α β} (p sep : Parser) (a) [Parser.HasView α p] [Parser.HasView β sep] :
   Parser.HasView (List (SepBy.Elem.View α β)) (sepBy p sep a) :=
 { view := λ stx, match stx.asNode with
-    | some n := sepBy.viewAux p sep n.args
+    | some n := sepBy.viewAux p sep n.args.toList
     | _ := [⟨view p Syntax.missing, none⟩],
-  review := λ as, Syntax.list $ as.bind (λ a, match a with
+  review := λ as, Syntax.list $ List.toArray $ as.bind (λ a, match a with
     | ⟨v, some vsep⟩ := [review p v, review sep vsep]
     | ⟨v, none⟩      := [review p v]) }
 
@@ -132,21 +133,20 @@ def optional (r : Parser) (require := false) : Parser :=
 if require then r else
 do r ← optional $
      -- on error, wrap in "some"
-     catch r (λ msg, throw {msg with custom := Syntax.list [msg.custom.get]}),
+     catch r (λ msg, throw {msg with custom := Syntax.list $ Array.singleton msg.custom.get}),
    pure $ match r with
-   | some r := Syntax.list [r]
-   | none   := Syntax.list []
+   | some r := Syntax.list $ Array.singleton r
+   | none   := Syntax.list $ Array.empty
 
 instance optional.tokens (r : Parser) [Parser.HasTokens r] (req) : Parser.HasTokens (optional r req) :=
 ⟨tokens r⟩
 instance optional.view (r : Parser) [Parser.HasView α r] (req) : Parser.HasView (Option α) (optional r req) :=
 { view := λ stx, match stx.asNode with
-    | some {args := [], ..} := none
-    | some {args := [stx], ..} := some $ HasView.view r stx
+    | some n := HasView.view r <$> n.args.oget 0
     | _ := some $ view r Syntax.missing,
   review := λ a, match a with
-    | some a := Syntax.list [review r a]
-    | none   := Syntax.list [] }
+    | some a := Syntax.list $ Array.singleton $ review r a
+    | none   := Syntax.list $ Array.empty }
 instance optional.viewDefault (r : Parser) [Parser.HasView α r] (req) : Parser.HasViewDefault (optional r req) (Option α) none := ⟨⟩
 
 /-- Parse a List `[p1, ..., pn]` of parsers as `p1 <|> ... <|> pn`.
@@ -169,7 +169,7 @@ def longestMatch (rs : List Parser) : Parser :=
 do stxs ← MonadParsec.longestMatch rs,
    match stxs with
    | [stx] := pure stx
-   | _     := pure $ Syntax.mkNode choice stxs
+   | _     := pure $ Syntax.mkNode choice stxs.toArray
 
 instance longestMatch.tokens (rs : List Parser) [Parser.HasTokens rs] : Parser.HasTokens (longestMatch rs) :=
 ⟨tokens rs⟩
@@ -179,7 +179,7 @@ def choiceAux : List Parser → Nat → Parser
 | []      _ := error "choice: Empty List"
 | (r::rs) i :=
   do { stx ← r,
-       pure $ Syntax.mkNode ⟨Name.mkNumeral Name.anonymous i⟩ [stx] }
+       pure $ Syntax.mkNode ⟨Name.mkNumeral Name.anonymous i⟩ $ Array.singleton stx }
   <|> choiceAux rs (i+1)
 
 /-- Parse a List `[p1, ..., pn]` of parsers as `p1 <|> ... <|> pn`.
@@ -198,7 +198,7 @@ instance choice.tokens (rs : List Parser) [Parser.HasTokens rs] : Parser.HasToke
 def longestChoice (rs : List Parser) : Parser :=
 do stx::stxs ← MonadParsec.longestMatch $ rs.enum.map $ λ ⟨i, r⟩, do {
      stx ← r,
-     pure $ Syntax.mkNode ⟨Name.mkNumeral Name.anonymous i⟩ [stx]
+     pure $ Syntax.mkNode ⟨Name.mkNumeral Name.anonymous i⟩ $ Array.singleton stx
    } | error "unreachable",
    pure stx
 
diff --git a/library/init/lean/parser/module.lean b/library/init/lean/parser/module.lean
index 0e6aca004974..025543014298 100644
--- a/library/init/lean/parser/module.lean
+++ b/library/init/lean/parser/module.lean
@@ -68,7 +68,7 @@ def eoi.Parser : moduleParser := do
   it ← leftOver,
   -- add `eoi` Node for left-over input
   let stop := it.toEnd,
-  pure $ Syntax.mkNode eoi [Syntax.atom ⟨some ⟨⟨stop, stop⟩, stop.offset, ⟨stop, stop⟩⟩, ""⟩]
+  pure $ Syntax.mkNode eoi [Syntax.atom ⟨some ⟨⟨stop, stop⟩, stop.offset, ⟨stop, stop⟩⟩, ""⟩].toArray
 
 /-- Read command, recovering from errors inside commands (attach partial Syntax tree)
     as well as unknown commands (skip input). -/
diff --git a/library/init/lean/parser/syntax.lean b/library/init/lean/parser/syntax.lean
index dd756745bf2e..69a3cc4d508d 100644
--- a/library/init/lean/parser/syntax.lean
+++ b/library/init/lean/parser/syntax.lean
@@ -4,7 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Author: Sebastian Ullrich
 -/
 prelude
-import init.lean.name init.lean.parser.parsec
+import init.lean.name init.lean.parser.parsec init.data.array
 
 namespace Lean
 namespace Parser
@@ -53,7 +53,7 @@ Remark: We do create `SyntaxNode`'s with an Empty `args` field (e.g. for represe
 -/
 structure SyntaxNode (Syntax : Type) :=
 (kind : SyntaxNodeKind)
-(args : List Syntax)
+(args : Array Syntax)
 -- Lazily propagated scopes. Scopes are pushed inwards when a Node is destructed via `Syntax.asNode`,
 -- until an ident or an atom (in which the scopes vanish) is reached.
 -- Scopes are stored in a stack with the most recent Scope at the top.
@@ -106,7 +106,7 @@ def flipScopes (scopes : macroScopes) : Syntax → Syntax
 | (Syntax.rawNode n) := Syntax.rawNode {n with scopes := n.scopes.flip scopes}
 | stx := stx
 
-def mkNode (kind : SyntaxNodeKind) (args : List Syntax) :=
+def mkNode (kind : SyntaxNodeKind) (args : Array Syntax) :=
 Syntax.rawNode { kind := kind, args := args }
 
 /-- Match against `Syntax.rawNode`, propagating lazy macro scopes. -/
@@ -114,7 +114,13 @@ def asNode : Syntax → Option (SyntaxNode Syntax)
 | (Syntax.rawNode n) := some {n with args := n.args.map (flipScopes n.scopes), scopes := []}
 | _                   := none
 
-protected def list (args : List Syntax) :=
+-- helper function used by the `node!` macro, to make sure its `view` function is branch-less
+@[noinline] def args (stx : Syntax) : Array Syntax :=
+match stx.asNode with
+| some n := n.args
+| _      := Array.empty
+
+protected def list (args : Array Syntax) :=
 mkNode noKind args
 
 def kind : Syntax → Option SyntaxNodeKind
@@ -173,7 +179,7 @@ def updateLeading (source : String) : Syntax → Syntax :=
 partial def getHeadInfo : Syntax → Option SourceInfo
 | (atom a)    := a.info
 | (ident id)  := id.info
-| (rawNode n) := n.args.foldr (λ s r, getHeadInfo s <|> r) none
+| (rawNode n) := n.args.foldl (λ s r, getHeadInfo s <|> r) none
 | _           := none
 
 def getPos (stx : Syntax) : Option Parsec.Position :=
@@ -190,7 +196,7 @@ partial def reprint : Syntax → Option String
 | (ident id@{info := some info, ..}) := pure $ info.leading.toString ++ id.rawVal.toString ++ info.trailing.toString
 | (ident id@{info := none,      ..}) := pure id.rawVal.toString
 | (rawNode n) :=
-  if n.kind.name = choice.name then match n.args with
+  if n.kind.name = choice.name then match n.args.toList with
   -- should never happen
   | [] := failure
   -- check that every choice prints the same
@@ -199,7 +205,7 @@ partial def reprint : Syntax → Option String
     ss ← ns.mmap reprint,
     guard $ ss.all (= s),
     pure s
-  else String.join <$> n.args.mmap reprint
+  else String.join <$> n.args.toList.mmap reprint
 | missing := ""
 
 protected partial def toFormat : Syntax → Format
@@ -210,9 +216,9 @@ protected partial def toFormat : Syntax → Format
   toFmt "`" ++ toFmt id.val ++ scopes
 | stx@(rawNode n) :=
   let scopes := match n.scopes with [] := toFmt "" | _ := bracket "{" (joinSep n.scopes.reverse ", ") "}" in
-  if n.kind.name = `Lean.Parser.noKind then sbracket $ scopes ++ joinSep (n.args.map toFormat) line
+  if n.kind.name = `Lean.Parser.noKind then sbracket $ scopes ++ joinSep (n.args.toList.map toFormat) line
   else let shorterName := n.kind.name.replacePrefix `Lean.Parser Name.anonymous
-       in paren $ joinSep ((toFmt shorterName ++ scopes) :: n.args.map toFormat) line
+       in paren $ joinSep ((toFmt shorterName ++ scopes) :: n.args.toList.map toFormat) line
 | missing := "<missing>"
 
 instance : HasToFormat Syntax := ⟨Syntax.toFormat⟩
diff --git a/library/init/lean/parser/term.lean b/library/init/lean/parser/term.lean
index a92f69cbccb4..1aea4390a989 100644
--- a/library/init/lean/parser/term.lean
+++ b/library/init/lean/parser/term.lean
@@ -396,7 +396,7 @@ def app.Parser : trailingTermParser :=
 node! app [fn: getLeading, Arg: Term.Parser maxPrec]
 
 def mkApp (fn : Syntax) (args : List Syntax) : Syntax :=
-args.foldl (λ fn Arg, Syntax.mkNode app [fn, Arg]) fn
+args.foldl (λ fn Arg, Syntax.mkNode app [fn, Arg].toArray) fn
 
 @[derive Parser.HasTokens Parser.HasView]
 def arrow.Parser : trailingTermParser :=
diff --git a/library/init/lean/parser/token.lean b/library/init/lean/parser/token.lean
index 77268a70735a..6405b32fd9e1 100644
--- a/library/init/lean/parser/token.lean
+++ b/library/init/lean/parser/token.lean
@@ -70,10 +70,11 @@ do start ← leftOver,
 
 variables [monadBasicParser m]
 
-@[specialize] def updateLast (f : Syntax → Syntax) (trailing : Substring) : List Syntax → List Syntax
-| []          := []
-| [stx]       := [f stx]
-| (stx::stxs) := stx :: updateLast stxs
+@[specialize] def updateLast (f : Syntax → Syntax) (trailing : Substring) (args : Array Syntax) : Array Syntax :=
+if args.isEmpty then args
+else
+  let i := args.size - 1 in
+  args.set i (f $ args.get i)
 
 private partial def updateTrailing : Substring → Syntax → Syntax
 | trailing (Syntax.atom a@⟨some info, _⟩) := Syntax.atom {a with info := some {info with trailing := trailing}}
diff --git a/src/frontends/lean/elaborator.cpp b/src/frontends/lean/elaborator.cpp
index b3dbad303543..7c2b004b76a4 100644
--- a/src/frontends/lean/elaborator.cpp
+++ b/src/frontends/lean/elaborator.cpp
@@ -3270,7 +3270,7 @@ expr elaborator::visit_node_macro(expr const & e, optional<expr> const & expecte
 
             binds << "let (stxs, stx) := match stxs : _ -> Prod (List Syntax) Syntax with (stx::stxs) := (stxs, stx) | _ := (stxs, Syntax.missing) in\n"
             << "let a" << i << " := Parser.HasView.view (" << pp(r) << " : " << pp(exp) << ")" << " stx in\n";
-            mk_args << "a" << i << " ";
+            mk_args << "(Parser.HasView.view (" << pp(r) << " : " << pp(exp) << ") (args.get " << i << ")) ";
             if (i != 0)
                 view_pat << ", ";
             view_pat << "a" << i;
@@ -3284,7 +3284,7 @@ expr elaborator::visit_node_macro(expr const & e, optional<expr> const & expecte
             new_args.push_back(add_field(r));
         } else {// try block
             binds << "let stxs := match stxs with stx::stxs := (match stx.asNode with some n := n.args ++ stxs | _ := stxs) | _ := stxs in\n";
-            reviews << "Syntax.list [";
+            reviews << "Syntax.list $ List.toArray [";
             buffer<expr> new_try_args;
             for (expr args = app_arg(app_arg(r)); is_app(args); args = app_arg(args)) {
                 expr r = app_arg(app_fn(args));
@@ -3297,11 +3297,9 @@ expr elaborator::visit_node_macro(expr const & e, optional<expr> const & expecte
         }
     }
     struc << "def " << macro.to_string() << ".HasView' " << params.str() << " : HasView " << macro.to_string() << ".View (" << esc_macro.to_string() << args.str() << ") :=\n"
-            << "{ view := fun stx, let stxs : List Syntax := match stx.asNode with"
-            << "| some n := n.args | _ := [] in\n"
-            << binds.str()
+            << "{ view := fun stx, let args := stx.args in "
             << macro.to_string() << ".View.mk " << mk_args.str() << ",\n"
-            << "review := fun ⟨" << view_pat.str() << "⟩, Syntax.mkNode " << esc_macro.to_string() << " [" << reviews.str() << "] }";
+            << "review := fun ⟨" << view_pat.str() << "⟩, Syntax.mkNode " << esc_macro.to_string() << "(List.toArray [" << reviews.str() << "])}";
     struc << "instance " << macro.to_string() << ".HasView  := @" << macro.to_string() << ".HasView'";
     trace_elab_detail(tout() << "expansion of node! macro:\n" << struc.str(););
     std::istringstream in(struc.str());
@@ -3369,23 +3367,23 @@ expr elaborator::visit_node_choice_macro(expr const & e, bool longest_match, opt
                 << " : " << pp(exp) << ") stx\n";
         review_cases << "| " << macro.to_string() << ".View." << fname << " a := "
                 << "Syntax.mkNode (SyntaxNodeKind.mk (Name.mkNumeral Name.anonymous " << i << ")) "
-                << "[review (" << pp(r) << " : " << pp(exp) << ") a]\n";
+                << "$ Array.singleton $ review (" << pp(r) << " : " << pp(exp) << ") a\n";
         i++;
         new_args.push_back(mk_as_is(r));
     }
     struc << "def " << macro.to_string() << ".HasView' " << params.str() << " : HasView " << macro.to_string() << ".View ("
           << esc_macro.to_string() << " " << pargs.str() << ") :=\n"
           << "{ view := fun stx, let (stx, i) := match stx.asNode : _ -> Prod Syntax Nat with\n"
-          << "| some {kind := @" << esc_macro.to_string() << " " << pargs.str() << ", args := [stx], ..} := (match stx.asNode  : _ -> Prod Syntax Nat with\n"
-          << "  | some {kind := SyntaxNodeKind.mk (Name.mkNumeral Name.anonymous i), args := [stx], ..} := (stx, i)\n"
+          << "| some {kind := @" << esc_macro.to_string() << " " << pargs.str() << ", args := args, ..} := (match (args.get 0).asNode  : _ -> Prod Syntax Nat with\n"
+          << "  | some {kind := SyntaxNodeKind.mk (Name.mkNumeral Name.anonymous i), args := args, ..} := (args.get 0, i)\n"
           << "  | _ := (Syntax.missing, 0))\n"
           << "| _ := (Syntax.missing, 0) in\n"
           << "match i with\n"
           << view_cases.str() << ",\n"
           << "review := fun v, Syntax.mkNode (" << esc_macro.to_string() << " " << pargs.str() << ")"
-          << " [match v with\n"
+          << " $ Array.singleton $ match v with\n"
           << review_cases.str()
-          << "] }";
+          << "}";
     struc << "instance " << macro.to_string() << ".HasView := @" << macro.to_string() << ".HasView'";
     trace_elab_detail(tout() << "expansion of nodeChoice! macro:\n" << struc.str(););
     std::istringstream in(struc.str());