fixes #12820 (#12828)

compiler/liftdestructors.nim

@@ -702,6 +702,12 @@ template inst(field, t) =
 proc isTrival(s: PSym): bool {.inline.} =
   s == nil or (s.ast != nil and s.ast[bodyPos].len == 0)
 
+
+proc isEmptyContainer(g: ModuleGraph, t: PType): bool =
+  (t.kind == tyArray and lengthOrd(g.config, t[0]) == 0) or 
+    (t.kind == tySequence and t[0].kind == tyError)
+
+
 proc createTypeBoundOps(g: ModuleGraph; c: PContext; orig: PType; info: TLineInfo) =
   ## In the semantic pass this is called in strategic places
   ## to ensure we lift assignment, destructors and moves properly.
@@ -710,6 +716,7 @@ proc createTypeBoundOps(g: ModuleGraph; c: PContext; orig: PType; info: TLineInf
   incl orig.flags, tfCheckedForDestructor
 
   let skipped = orig.skipTypes({tyGenericInst, tyAlias, tySink})
+  if isEmptyContainer(skipped): return
 
   let h = sighashes.hashType(skipped, {CoType, CoConsiderOwned, CoDistinct})
   var canon = g.canonTypes.getOrDefault(h)

tests/destructor/t12037.nim

@@ -16,3 +16,10 @@ proc test() =
   doAssert cast[int](sq1[0].unsafeAddr) != 0
 
 test()
+
+
+#############################################
+### bug 12820
+import tables
+var t = initTable[string, seq[ptr int]]()
+discard t.hasKeyOrPut("f1", @[])