fix #19435; don't create TypeBoundOps for tyOpenArray, tyVarargs [backport: 1.6] (#19723)

* fix #19435; openArray wronyly registers typebounds

* add testcase

* don't create TypeBoundOps for tyOpenArray, tyVarargs

compiler/sempass2.nim

@@ -1054,7 +1054,7 @@ proc track(tracked: PEffects, n: PNode) =
     addAsgnFact(tracked.guards, n[0], n[1])
     notNilCheck(tracked, n[1], n[0].typ)
     when false: cstringCheck(tracked, n)
-    if tracked.owner.kind != skMacro:
+    if tracked.owner.kind != skMacro and n[0].typ.kind notin {tyOpenArray, tyVarargs}:
       createTypeBoundOps(tracked, n[0].typ, n.info)
     if n[0].kind != nkSym or not isLocalVar(tracked, n[0].sym):
       checkForSink(tracked.config, tracked.c.idgen, tracked.owner, n[1])

tests/arc/t19435.nim

@@ -0,0 +1,29 @@
+discard """
+  matrix: "--gc:arc"
+"""
+
+# bug #19435
+{.experimental: "views".}
+
+type
+  Bar = object
+    placeholder: int
+  Foo = object
+    placeholder: int
+    c: seq[Bar] # remove this line to make things right
+
+func children*(s: var seq[Foo]): openArray[Foo] =
+  s.toOpenArray(0, s.len-1)
+
+proc test =
+  var foos = @[Foo(), Foo()]
+
+  assert foos.children.len == 2
+  var flag = true
+  for a in foos.children:
+    flag = false
+
+  if flag:
+    doAssert false
+
+test()