From 065a6af2dea252818bd58af066378ee54be2c3f8 Mon Sep 17 00:00:00 2001
From: Andreas Rumpf <rumpf_a@web.de>
Date: Mon, 27 Apr 2020 22:20:14 +0200
Subject: [PATCH] fixes a critical =trace generation bug (see test case)
 (#14140)

---
 compiler/liftdestructors.nim |  6 +++++-
 compiler/types.nim           |  2 +-
 tests/destructor/tcycle2.nim | 16 ++++++++++++++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/compiler/liftdestructors.nim b/compiler/liftdestructors.nim
index 61034ef033..5959e24c5e 100644
--- a/compiler/liftdestructors.nim
+++ b/compiler/liftdestructors.nim
@@ -253,9 +253,13 @@ proc newOpCall(op: PSym; x: PNode): PNode =
 proc newDeepCopyCall(op: PSym; x, y: PNode): PNode =
   result = newAsgnStmt(x, newOpCall(op, y))
 
+proc usesBuiltinArc(t: PType): bool =
+  proc wrap(t: PType): bool {.nimcall.} = ast.isGCedMem(t)
+  result = types.searchTypeFor(t, wrap)
+
 proc useNoGc(c: TLiftCtx; t: PType): bool {.inline.} =
   result = optSeqDestructors in c.g.config.globalOptions and
-    ({tfHasGCedMem, tfHasOwned} * t.flags != {} or t.isGCedMem)
+    ({tfHasGCedMem, tfHasOwned} * t.flags != {} or usesBuiltinArc(t))
 
 proc requiresDestructor(c: TLiftCtx; t: PType): bool {.inline.} =
   result = optSeqDestructors in c.g.config.globalOptions and
diff --git a/compiler/types.nim b/compiler/types.nim
index cf3f7117aa..241229df61 100644
--- a/compiler/types.nim
+++ b/compiler/types.nim
@@ -253,7 +253,7 @@ proc searchTypeForAux(t: PType, predicate: TTypePredicate,
   else:
     discard
 
-proc searchTypeFor(t: PType, predicate: TTypePredicate): bool =
+proc searchTypeFor*(t: PType, predicate: TTypePredicate): bool =
   var marker = initIntSet()
   result = searchTypeForAux(t, predicate, marker)
 
diff --git a/tests/destructor/tcycle2.nim b/tests/destructor/tcycle2.nim
index 843c7cf1cd..7b03101fea 100644
--- a/tests/destructor/tcycle2.nim
+++ b/tests/destructor/tcycle2.nim
@@ -13,8 +13,24 @@ proc main(x: int) =
   let m = n
   n.kids.add m
 
+type
+  NodeA = ref object
+    s: char
+    a: array[3, NodeA]
+
+proc m: NodeA =
+  result = NodeA(s: 'a')
+  result.a[0] = result
+  result.a[1] = result
+  result.a[2] = result
+
+proc mainA =
+  for i in 0..10:
+    discard m()
+
 let mem = getOccupiedMem()
 main(90)
+mainA()
 GC_fullCollect()
 
 echo "MEM ", getOccupiedMem() - mem