diff --git a/compiler/sempass2.nim b/compiler/sempass2.nim
index aa04f7451e..3528714128 100644
--- a/compiler/sempass2.nim
+++ b/compiler/sempass2.nim
@@ -514,25 +514,26 @@ proc notNilCheck(tracked: PEffects, n: PNode, paramType: PType) =
   #elif n.kind in nkSymChoices:
   #  echo "came here"
   let paramType = paramType.skipTypesOrNil(abstractInst)
-  if paramType != nil and tfNotNil in paramType.flags and
-      n.typ != nil and tfNotNil notin n.typ.flags:
-    if isAddrNode(n):
-      # addr(x[]) can't be proven, but addr(x) can:
-      if not containsNode(n, {nkDerefExpr, nkHiddenDeref}): return
-    elif (n.kind == nkSym and n.sym.kind in routineKinds) or
-         (n.kind in procDefs+{nkObjConstr, nkBracket, nkClosure, nkStrLit..nkTripleStrLit}) or
-         (n.kind in nkCallKinds and n[0].kind == nkSym and n[0].sym.magic == mArrToSeq) or
-         n.typ.kind == tyTypeDesc:
-      # 'p' is not nil obviously:
-      return
-    case impliesNotNil(tracked.guards, n)
-    of impUnknown:
-      message(tracked.config, n.info, errGenerated,
-              "cannot prove '$1' is not nil" % n.renderTree)
-    of impNo:
-      message(tracked.config, n.info, errGenerated,
-              "'$1' is provably nil" % n.renderTree)
-    of impYes: discard
+  if paramType != nil and tfNotNil in paramType.flags and n.typ != nil:
+    let ntyp = n.typ.skipTypesOrNil({tyVar, tyLent, tySink})
+    if ntyp != nil and tfNotNil notin ntyp.flags:
+      if isAddrNode(n):
+        # addr(x[]) can't be proven, but addr(x) can:
+        if not containsNode(n, {nkDerefExpr, nkHiddenDeref}): return
+      elif (n.kind == nkSym and n.sym.kind in routineKinds) or
+          (n.kind in procDefs+{nkObjConstr, nkBracket, nkClosure, nkStrLit..nkTripleStrLit}) or
+          (n.kind in nkCallKinds and n[0].kind == nkSym and n[0].sym.magic == mArrToSeq) or
+          n.typ.kind == tyTypeDesc:
+        # 'p' is not nil obviously:
+        return
+      case impliesNotNil(tracked.guards, n)
+      of impUnknown:
+        message(tracked.config, n.info, errGenerated,
+                "cannot prove '$1' is not nil" % n.renderTree)
+      of impNo:
+        message(tracked.config, n.info, errGenerated,
+                "'$1' is provably nil" % n.renderTree)
+      of impYes: discard
 
 proc assumeTheWorst(tracked: PEffects; n: PNode; op: PType) =
   addRaiseEffect(tracked, createRaise(tracked.graph, n), nil)
diff --git a/lib/pure/collections/tableimpl.nim b/lib/pure/collections/tableimpl.nim
index df9cb75176..c66da513c5 100644
--- a/lib/pure/collections/tableimpl.nim
+++ b/lib/pure/collections/tableimpl.nim
@@ -27,7 +27,7 @@ proc rawGetDeep[X, A](t: X, key: A, hc: var Hash): int {.inline.} =
   rawGetDeepImpl()
 
 proc rawInsert[X, A, B](t: var X, data: var KeyValuePairSeq[A, B],
-                     key: A, val: B, hc: Hash, h: Hash) =
+                     key: A, val: sink B, hc: Hash, h: Hash) =
   rawInsertImpl()
 
 template checkIfInitialized() =
diff --git a/lib/pure/collections/tables.nim b/lib/pure/collections/tables.nim
index 85440bd2ba..bd46bdd279 100644
--- a/lib/pure/collections/tables.nim
+++ b/lib/pure/collections/tables.nim
@@ -300,7 +300,7 @@ proc initTable*[A, B](initialSize = defaultInitialSize): Table[A, B] =
       b = initTable[char, seq[int]]()
   initImpl(result, initialSize)
 
-proc `[]=`*[A, B](t: var Table[A, B], key: A, val: B) =
+proc `[]=`*[A, B](t: var Table[A, B], key: A, val: sink B) =
   ## Inserts a ``(key, value)`` pair into ``t``.
   ##
   ## See also:
@@ -484,7 +484,7 @@ proc len*[A, B](t: Table[A, B]): int =
 
   result = t.counter
 
-proc add*[A, B](t: var Table[A, B], key: A, val: B) {.deprecated:
+proc add*[A, B](t: var Table[A, B], key: A, val: sink B) {.deprecated:
     "Deprecated since v1.4; it was more confusing than useful, use `[]=`".} =
   ## Puts a new ``(key, value)`` pair into ``t`` even if ``t[key]`` already exists.
   ##
@@ -839,7 +839,7 @@ proc `[]`*[A, B](t: TableRef[A, B], key: A): var B =
 
   result = t[][key]
 
-proc `[]=`*[A, B](t: TableRef[A, B], key: A, val: B) =
+proc `[]=`*[A, B](t: TableRef[A, B], key: A, val: sink B) =
   ## Inserts a ``(key, value)`` pair into ``t``.
   ##
   ## See also:
@@ -968,7 +968,7 @@ proc len*[A, B](t: TableRef[A, B]): int =
 
   result = t.counter
 
-proc add*[A, B](t: TableRef[A, B], key: A, val: B) {.deprecated:
+proc add*[A, B](t: TableRef[A, B], key: A, val: sink B) {.deprecated:
     "Deprecated since v1.4; it was more confusing than useful, use `[]=`".} =
   ## Puts a new ``(key, value)`` pair into ``t`` even if ``t[key]`` already exists.
   ##
@@ -1217,7 +1217,7 @@ proc rawGet[A, B](t: OrderedTable[A, B], key: A, hc: var Hash): int =
 
 proc rawInsert[A, B](t: var OrderedTable[A, B],
                      data: var OrderedKeyValuePairSeq[A, B],
-                     key: A, val: B, hc: Hash, h: Hash) =
+                     key: A, val: sink B, hc: Hash, h: Hash) =
   rawInsertImpl()
   data[h].next = -1
   if t.first < 0: t.first = h
@@ -1268,7 +1268,7 @@ proc initOrderedTable*[A, B](initialSize = defaultInitialSize): OrderedTable[A,
       b = initOrderedTable[char, seq[int]]()
   initImpl(result, initialSize)
 
-proc `[]=`*[A, B](t: var OrderedTable[A, B], key: A, val: B) =
+proc `[]=`*[A, B](t: var OrderedTable[A, B], key: A, val: sink B) =
   ## Inserts a ``(key, value)`` pair into ``t``.
   ##
   ## See also:
@@ -1455,7 +1455,7 @@ proc len*[A, B](t: OrderedTable[A, B]): int {.inline.} =
 
   result = t.counter
 
-proc add*[A, B](t: var OrderedTable[A, B], key: A, val: B) {.deprecated:
+proc add*[A, B](t: var OrderedTable[A, B], key: A, val: sink B) {.deprecated:
     "Deprecated since v1.4; it was more confusing than useful, use `[]=`".} =
   ## Puts a new ``(key, value)`` pair into ``t`` even if ``t[key]`` already exists.
   ##
@@ -1810,7 +1810,7 @@ proc `[]`*[A, B](t: OrderedTableRef[A, B], key: A): var B =
       echo a['z']
   result = t[][key]
 
-proc `[]=`*[A, B](t: OrderedTableRef[A, B], key: A, val: B) =
+proc `[]=`*[A, B](t: OrderedTableRef[A, B], key: A, val: sink B) =
   ## Inserts a ``(key, value)`` pair into ``t``.
   ##
   ## See also:
@@ -1939,7 +1939,7 @@ proc len*[A, B](t: OrderedTableRef[A, B]): int {.inline.} =
 
   result = t.counter
 
-proc add*[A, B](t: OrderedTableRef[A, B], key: A, val: B) {.deprecated:
+proc add*[A, B](t: OrderedTableRef[A, B], key: A, val: sink B) {.deprecated:
     "Deprecated since v1.4; it was more confusing than useful, use `[]=`".} =
   ## Puts a new ``(key, value)`` pair into ``t`` even if ``t[key]`` already exists.
   ##