2 files changed, 31 insertions, 2 deletions
diff --git a/lib/pure/collections/tables.nim b/lib/pure/collections/tables.nim
index b5fc1737a..ce9df09e1 100644
--- a/lib/pure/collections/tables.nim
+++ b/lib/pure/collections/tables.nim
@@ -146,6 +146,14 @@ proc mget*[A, B](t: var TTable[A, B], key: A): var B =
   if index >= 0: result = t.data[index].val
   else: raise newException(EInvalidKey, "key not found: " & $key)
 
+iterator allValues*[A, B](t: TTable[A, B]; key: A): B =
+  ## iterates over any value in the table `t` that belongs to the given `key`.
+  var h: THash = hash(key) and high(t.data)
+  while t.data[h].slot != seEmpty:
+    if t.data[h].key == key and t.data[h].slot == seFilled:
+      yield t.data[h].val
+    h = nextTry(h, high(t.data))
+
 proc hasKey*[A, B](t: TTable[A, B], key: A): bool =
   ## returns true iff `key` is in the table `t`.
   result = rawGet(t, key) >= 0
@@ -314,8 +322,7 @@ proc newTable*[A, B](initialSize=64): PTable[A, B] =
   new(result)
   result[] = initTable[A, B](initialSize)
 
-proc newTable*[A, B](pairs: openArray[tuple[key: A, 
-                    val: B]]): PTable[A, B] =
+proc newTable*[A, B](pairs: openArray[tuple[key: A, val: B]]): PTable[A, B] =
   ## creates a new hash table that contains the given `pairs`.
   new(result)
   result[] = toTable[A, B](pairs)
diff --git a/lib/system/chcks.nim b/lib/system/chcks.nim
index f29e222e8..387b54ef1 100644
--- a/lib/system/chcks.nim
+++ b/lib/system/chcks.nim
@@ -67,6 +67,28 @@ proc chckObjAsgn(a, b: PNimType) {.compilerproc, inline.} =
   if a != b:
     sysFatal(EInvalidObjectAssignment, "invalid object assignment")
 
+type ObjCheckCache = array[0..1, PNimType]
+
+proc isObjSlowPath(obj, subclass: PNimType;
+                   cache: var ObjCheckCache): bool {.noinline.} =
+  # checks if obj is of type subclass:
+  var x = obj.base
+  while x != subclass:
+    if x == nil:
+      cache[0] = obj
+      return false
+    x = x.base
+  cache[1] = obj
+  return true
+
+proc isObjWithCache(obj, subclass: PNimType;
+                    cache: var ObjCheckCache): bool {.compilerProc, inline.} =
+  if obj == subclass: return true
+  if obj.base == subclass: return true
+  if cache[0] == obj: return false
+  if cache[1] == obj: return true
+  return isObjSlowPath(obj, subclass, cache)
+
 proc isObj(obj, subclass: PNimType): bool {.compilerproc.} =
   # checks if obj is of type subclass:
   var x = obj