fixes #14495 [backport:1.2] (#14496)

compiler/liftdestructors.nim

@@ -534,8 +534,8 @@ proc atomicRefOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
     body.add genIf(c, cond, actions)
     body.add newAsgnStmt(x, y)
   of attachedDestructor:
-    actions.add newAsgnStmt(x, newNodeIT(nkNilLit, body.info, t))
     body.add genIf(c, cond, actions)
+    body.add newAsgnStmt(x, newNodeIT(nkNilLit, body.info, t))
   of attachedDeepCopy: assert(false, "cannot happen")
   of attachedTrace:
     if isFinal(elemType):
@@ -583,8 +583,8 @@ proc atomicClosureOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
     body.add genIf(c, cond, actions)
     body.add newAsgnStmt(x, y)
   of attachedDestructor:
-    actions.add newAsgnStmt(xenv, newNodeIT(nkNilLit, body.info, xenv.typ))
     body.add genIf(c, cond, actions)
+    body.add newAsgnStmt(xenv, newNodeIT(nkNilLit, body.info, xenv.typ))
   of attachedDeepCopy: assert(false, "cannot happen")
   of attachedTrace:
     body.add callCodegenProc(c.g, "nimTraceRefDyn", c.info, genAddrOf(xenv), y)
@@ -641,8 +641,8 @@ proc ownedRefOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
     body.add genIf(c, x, actions)
     body.add newAsgnStmt(x, y)
   of attachedDestructor:
-    actions.add newAsgnStmt(x, newNodeIT(nkNilLit, body.info, t))
     body.add genIf(c, x, actions)
+    body.add newAsgnStmt(x, newNodeIT(nkNilLit, body.info, t))
   of attachedDeepCopy: assert(false, "cannot happen")
   of attachedTrace, attachedDispose: discard
 
@@ -694,8 +694,8 @@ proc ownedClosureOp(c: var TLiftCtx; t: PType; body, x, y: PNode) =
     body.add genIf(c, xx, actions)
     body.add newAsgnStmt(x, y)
   of attachedDestructor:
-    actions.add newAsgnStmt(xx, newNodeIT(nkNilLit, body.info, xx.typ))
     body.add genIf(c, xx, actions)
+    body.add newAsgnStmt(xx, newNodeIT(nkNilLit, body.info, xx.typ))
   of attachedDeepCopy: assert(false, "cannot happen")
   of attachedTrace, attachedDispose: discard
 

tests/arc/tarcmisc.nim

@@ -4,6 +4,17 @@ discard """
 destroyed: false
 destroyed: false
 1
+(x: "0")
+(x: "1")
+(x: "2")
+(x: "3")
+(x: "4")
+(x: "5")
+(x: "6")
+(x: "7")
+(x: "8")
+(x: "9")
+(x: "10")
 closed
 destroying variable
 '''
@@ -99,10 +110,10 @@ type
   MyType = object
     a: seq[int]
 
-proc re(x: static[string]): static MyType = 
+proc re(x: static[string]): static MyType =
   MyType()
 
-proc match(inp: string, rg: static MyType) = 
+proc match(inp: string, rg: static MyType) =
   doAssert rg.a.len == 0
 
 match("ac", re"a(b|c)")
@@ -125,13 +136,40 @@ var game*: Game
 #------------------------------------------------------------------------------
 # issue #14333
 
-type  
+type
   SimpleLoop = object
-  
+
   Lsg = object
     loops: seq[ref SimpleLoop]
     root: ref SimpleLoop
 
 var lsg: Lsg
 lsg.loops.add lsg.root
-echo lsg.loops.len
+echo lsg.loops.len
+
+# bug #14495
+type
+  Gah = ref object
+    x: string
+
+proc bug14495 =
+  var owners: seq[Gah]
+  for i in 0..10:
+    owners.add Gah(x: $i)
+
+  var x: seq[Gah]
+  for i in 0..10:
+    x.add owners[i]
+
+  for i in 0..100:
+    setLen(x, 0)
+    setLen(x, 10)
+
+  for i in 0..x.len-1:
+    if x[i] != nil:
+      echo x[i][]
+
+  for o in owners:
+    echo o[]
+
+bug14495()