fixes a critical =trace generation bug (see test case) (#14140)

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

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)
 

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