From 9778eca9b2dfe8a54ca1cd412a43318cd9ee4ecf Mon Sep 17 00:00:00 2001
From: Leonardo de Moura <leonardo@microsoft.com>
Date: Mon, 19 Oct 2020 11:50:42 -0700
Subject: [PATCH] chore: move to new frontend

---
 src/Lean/Meta/KAbstract.lean | 60 ++++++++++++++++++------------------
 1 file changed, 30 insertions(+), 30 deletions(-)

diff --git a/src/Lean/Meta/KAbstract.lean b/src/Lean/Meta/KAbstract.lean
index 065c32452e..41ba80b640 100644
--- a/src/Lean/Meta/KAbstract.lean
+++ b/src/Lean/Meta/KAbstract.lean
@@ -1,3 +1,4 @@
+#lang lean4
 /-
 Copyright (c) 2020 Microsoft Corporation. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
@@ -7,38 +8,37 @@ import Lean.Data.Occurrences
 import Lean.HeadIndex
 import Lean.Meta.ExprDefEq
 
-namespace Lean
-namespace Meta
-
-private partial def kabstractAux (occs : Occurrences) (p : Expr) (pHeadIdx : HeadIndex) (pNumArgs : Nat) : Expr → Nat → StateRefT Nat MetaM Expr
-| e, offset =>
-  let visitChildren : Unit → StateRefT Nat MetaM Expr := fun _ =>
-    match e with
-    | Expr.app f a _       => do f ← kabstractAux f offset; a ← kabstractAux a offset; pure $ e.updateApp! f a
-    | Expr.mdata _ b _     => do b ← kabstractAux b offset; pure $ e.updateMData! b
-    | Expr.proj _ _ b _    => do b ← kabstractAux b offset; pure $ e.updateProj! b
-    | Expr.letE _ t v b _  => do t ← kabstractAux t offset; v ← kabstractAux v offset; b ← kabstractAux b (offset+1); pure $ e.updateLet! t v b
-    | Expr.lam _ d b _     => do d ← kabstractAux d offset; b ← kabstractAux b (offset+1); pure $ e.updateLambdaE! d b
-    | Expr.forallE _ d b _ => do d ← kabstractAux d offset; b ← kabstractAux b (offset+1); pure $ e.updateForallE! d b
-    | e                    => pure e;
-  if e.hasLooseBVars then visitChildren ()
-  else if e.toHeadIndex == pHeadIdx && e.headNumArgs == pNumArgs then
-    condM (isDefEq e p)
-      (do i ← get;
-          set (i+1);
-          if occs.contains i then
-            pure (mkBVar offset)
-          else
-            visitChildren ())
-      (visitChildren ())
-  else
-    visitChildren ()
+namespace Lean.Meta
 
 def kabstract {m} [MonadLiftT MetaM m] (e : Expr) (p : Expr) (occs : Occurrences := Occurrences.all) : m Expr := liftMetaM do
 if p.isFVar && occs == Occurrences.all then
-  pure $ e.abstract #[p] -- Easy case
+  return e.abstract #[p] -- Easy case
 else
-  (kabstractAux occs p p.toHeadIndex p.headNumArgs e 0).run' 1
+  let pHeadIdx := p.toHeadIndex
+  let pNumArgs := p.headNumArgs
+  let rec visit (e : Expr) (offset : Nat) : StateRefT Nat MetaM Expr := do
+    let visitChildren : Unit → StateRefT Nat MetaM Expr := fun _ => do
+      match e with
+      | Expr.app f a _       => return e.updateApp! (← visit f offset) (← visit a offset)
+      | Expr.mdata _ b _     => return e.updateMData! (← visit b offset)
+      | Expr.proj _ _ b _    => return e.updateProj! (← visit b offset)
+      | Expr.letE _ t v b _  => return e.updateLet! (← visit t offset) (← visit v offset) (← visit b (offset+1))
+      | Expr.lam _ d b _     => return e.updateLambdaE! (← visit d offset) (← visit b (offset+1))
+      | Expr.forallE _ d b _ => return e.updateForallE! (← visit d offset) (← visit b (offset+1))
+      | e                    => return e
+    if e.hasLooseBVars then
+      visitChildren ()
+    else if e.toHeadIndex != pHeadIdx || e.headNumArgs != pNumArgs then
+      visitChildren ()
+    else if (← isDefEq e p) then
+      let i ← get
+      set (i+1)
+      if occs.contains i then
+        pure (mkBVar offset)
+      else
+        visitChildren ()
+    else
+      visitChildren ()
+  (visit e 0).run' 1
 
-end Meta
-end Lean
+end Lean.Meta