From 2384826933593c5ddaa787c3708f4193414f088e Mon Sep 17 00:00:00 2001
From: Leonardo de Moura <leonardo@microsoft.com>
Date: Tue, 13 Apr 2021 15:46:47 -0700
Subject: [PATCH] chore: add loop prenvention code at do-expander

---
 src/Lean/Elab/Do.lean | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/Lean/Elab/Do.lean b/src/Lean/Elab/Do.lean
index a62cd4143b..f254f0f4d9 100644
--- a/src/Lean/Elab/Do.lean
+++ b/src/Lean/Elab/Do.lean
@@ -1451,7 +1451,8 @@ mutual
 
   partial def doSeqToCode : List Syntax → M CodeBlock
     | [] => do liftMacroM mkPureUnitAction
-    | doElem::doElems => withRef doElem do
+    | doElem::doElems => withIncRecDepth <| withRef doElem do
+      checkMaxHeartbeats "'do'-expander"
       match (← liftMacroM <| expandMacro? doElem) with
       | some doElem => doSeqToCode (doElem::doElems)
       | none =>