fixes #12092

compiler/semstmts.nim

@@ -1595,7 +1595,7 @@ proc semOverride(c: PContext, s: PSym, n: PNode) =
         else: break
       if obj.kind in {tyObject, tyDistinct, tySequence, tyString}:
         obj = canonType(c, obj)
-        if obj.destructor.isNil:
+        if obj.destructor.isNil and tfCheckedForDestructor notin obj.flags:
           obj.attachedOps[attachedDestructor] = s
         else:
           prevDestructor(c, obj.destructor, obj, n.info)
@@ -1660,7 +1660,7 @@ proc semOverride(c: PContext, s: PSym, n: PNode) =
         obj = canonType(c, obj)
         #echo "ATTACHING TO ", obj.id, " ", s.name.s, " ", cast[int](obj)
         let k = if name == "=": attachedAsgn else: attachedSink
-        if obj.attachedOps[k].isNil:
+        if obj.attachedOps[k].isNil and tfCheckedForDestructor notin obj.flags:
           obj.attachedOps[k] = s
         else:
           prevDestructor(c, obj.attachedOps[k], obj, n.info)

tests/destructor/tdestructor_too_late.nim

@@ -0,0 +1,14 @@
+discard """
+  errmsg: "cannot bind another '=destroy' to: Obj; previous declaration was constructed here implicitly: tdestructor_too_late.nim(7, 16)"
+"""
+type Obj* = object
+  v*: int
+
+proc something(this: sink Obj) = 
+  discard
+
+proc `=destroy`(this: var Obj) =
+  echo "igotdestroyed"
+  this.v = -1
+
+var test* = Obj(v: 42)