diff --git a/compiler/ccgtypes.nim b/compiler/ccgtypes.nim
index 26c0242f5c..6d9533dd1d 100755
--- a/compiler/ccgtypes.nim
+++ b/compiler/ccgtypes.nim
@@ -641,20 +641,16 @@ proc genObjectInfo(m: BModule, typ: PType, name: PRope) =
   genObjectFields(m, typ, typ.n, tmp)
   appf(m.s[cfsTypeInit3], "$1->node = &$2;$n", [name, tmp])
 
-proc genTupleInfo(m: BModule, typ: PType, name: PRope) = 
-  var 
-    tmp, expr, tmp2: PRope
-    length: int
-    a: PType
+proc genTupleInfo(m: BModule, typ: PType, name: PRope) =
   genTypeInfoAuxBase(m, typ, name, toRope("0"))
-  expr = getNimNode(m)
-  length = sonsLen(typ)
+  var expr = getNimNode(m)
+  var length = sonsLen(typ)
   if length > 0: 
-    tmp = getTempName()
+    var tmp = getTempName()
     appf(m.s[cfsTypeInit1], "static TNimNode* $1[$2];$n", [tmp, toRope(length)])
     for i in countup(0, length - 1): 
-      a = typ.sons[i]
-      tmp2 = getNimNode(m)
+      var a = typ.sons[i]
+      var tmp2 = getNimNode(m)
       appf(m.s[cfsTypeInit3], "$1[$2] = &$3;$n", [tmp, toRope(i), tmp2])
       appf(m.s[cfsTypeInit3], "$1.kind = 1;$n" &
           "$1.offset = offsetof($2, Field$3);$n" & "$1.typ = $4;$n" &
@@ -665,7 +661,7 @@ proc genTupleInfo(m: BModule, typ: PType, name: PRope) =
   else: 
     appf(m.s[cfsTypeInit3], "$1.len = $2; $1.kind = 2;$n", 
          [expr, toRope(length)])
-  appf(m.s[cfsTypeInit3], "$1->node = &$2;$n", [name, tmp])
+  appf(m.s[cfsTypeInit3], "$1->node = &$2;$n", [name, expr])
 
 proc genEnumInfo(m: BModule, typ: PType, name: PRope) =
   # Type information for enumerations is quite heavy, so we do some
diff --git a/compiler/seminst.nim b/compiler/seminst.nim
index e37c6e0fc8..6d2eaa6d12 100755
--- a/compiler/seminst.nim
+++ b/compiler/seminst.nim
@@ -36,9 +36,8 @@ proc GenericCacheGet(c: PContext, genericSym, instSym: PSym): PSym =
     var a = c.generics.sons[i].sons[0].sym
     if genericSym.id == a.id: 
       var b = c.generics.sons[i].sons[1].sym
-      if equalParams(b.typ.n, instSym.typ.n) == paramsEqual: 
-        #if gVerbosity > 0 then 
-        #  MessageOut('found in cache: ' + getProcHeader(instSym));
+      if equalParams(b.typ.n, instSym.typ.n) == paramsEqual:
+        #echo "found in cache: ", getProcHeader(instSym)
         return b
 
 proc GenericCacheAdd(c: PContext, genericSym, instSym: PSym) = 
@@ -66,20 +65,17 @@ proc removeDefaultParamValues(n: PNode) =
 proc generateInstance(c: PContext, fn: PSym, pt: TIdTable, 
                       info: TLineInfo): PSym = 
   # generates an instantiated proc
-  var 
-    oldPrc, oldMod: PSym
-    n: PNode
   if c.InstCounter > 1000: InternalError(fn.ast.info, "nesting too deep")
   inc(c.InstCounter)
   # NOTE: for access of private fields within generics from a different module
   # and other identifiers we fake the current module temporarily!
   # XXX bad hack!
-  oldMod = c.module
+  var oldMod = c.module
   c.module = getModule(fn)
   result = copySym(fn, false)
   incl(result.flags, sfFromGeneric)
   result.owner = getCurrOwner().owner
-  n = copyTree(fn.ast)
+  var n = copyTree(fn.ast)
   result.ast = n
   pushOwner(result)
   openScope(c.tab)
@@ -98,7 +94,7 @@ proc generateInstance(c: PContext, fn: PSym, pt: TIdTable,
     result.typ = newTypeS(tyProc, c)
     addSon(result.typ, nil)
   result.typ.callConv = fn.typ.callConv
-  oldPrc = GenericCacheGet(c, fn, result)
+  var oldPrc = GenericCacheGet(c, fn, result)
   if oldPrc == nil: 
     # add it here, so that recursive generic procs are possible:
     GenericCacheAdd(c, fn, result)
@@ -110,6 +106,7 @@ proc generateInstance(c: PContext, fn: PSym, pt: TIdTable,
         addResultNode(c, n)
       n.sons[codePos] = semStmtScope(c, n.sons[codePos])
       popProcCon(c)
+      #echo "code instantiated ", result.name.s
   else:
     result = oldPrc
   popInfoContext()
diff --git a/compiler/semtypinst.nim b/compiler/semtypinst.nim
index b6126e2852..e5f573248b 100755
--- a/compiler/semtypinst.nim
+++ b/compiler/semtypinst.nim
@@ -32,7 +32,7 @@ proc containsGenericType*(t: PType): bool =
 proc searchInstTypes(tab: TIdTable, key: PType): PType = 
   # returns nil if we need to declare this type
   result = PType(IdTableGet(tab, key))
-  if (result == nil) and (tab.counter > 0): 
+  if result == nil and tab.counter > 0: 
     # we have to do a slow linear search because types may need
     # to be compared by their structure:
     for h in countup(0, high(tab.data)): 
@@ -127,13 +127,13 @@ proc ReplaceTypeVarsT*(cl: var TReplTypeVars, t: PType): PType =
   of tyGenericBody: 
     InternalError(cl.info, "ReplaceTypeVarsT: tyGenericBody")
     result = ReplaceTypeVarsT(cl, lastSon(t))
-  else: 
-    if containsGenericType(t): 
+  else:
+    if containsGenericType(t):
       result = copyType(t, t.owner, false)
-      for i in countup(0, sonsLen(result) - 1): 
+      for i in countup(0, sonsLen(result) - 1):
         result.sons[i] = ReplaceTypeVarsT(cl, result.sons[i])
       result.n = ReplaceTypeVarsN(cl, result.n)
-      if result.Kind in GenericTypes: 
+      if result.Kind in GenericTypes:
         LocalError(cl.info, errCannotInstantiateX, TypeToString(t, preferName))
         #writeln(output, ropeToStr(Typetoyaml(result)))
         #checkConstructedType(cl.info, result)
diff --git a/compiler/transf.nim b/compiler/transf.nim
index f301a3717e..4031e6eb45 100755
--- a/compiler/transf.nim
+++ b/compiler/transf.nim
@@ -514,10 +514,10 @@ proc transformFor(c: PTransf, n: PNode): PTransNode =
   popTransCon(c)
 
 proc getMagicOp(call: PNode): TMagic = 
-  if (call.sons[0].kind == nkSym) and
-      (call.sons[0].sym.kind in {skProc, skMethod, skConverter}): 
+  if call.sons[0].kind == nkSym and
+      call.sons[0].sym.kind in {skProc, skMethod, skConverter}: 
     result = call.sons[0].sym.magic
-  else: 
+  else:
     result = mNone
   
 proc gatherVars(c: PTransf, n: PNode, marked: var TIntSet, owner: PSym, 
@@ -528,10 +528,10 @@ proc gatherVars(c: PTransf, n: PNode, marked: var TIntSet, owner: PSym,
     var s = n.sym
     var found = false
     case s.kind
-    of skVar: found = not (sfGlobal in s.flags)
+    of skVar: found = sfGlobal notin s.flags
     of skTemp, skForVar, skParam: found = true
     else: nil
-    if found and (owner.id != s.owner.id) and not ContainsOrIncl(marked, s.id): 
+    if found and owner.id != s.owner.id and not ContainsOrIncl(marked, s.id): 
       incl(s.flags, sfInClosure)
       addSon(container, copyNode(n)) # DON'T make a copy of the symbol!
   of nkEmpty..pred(nkSym), succ(nkSym)..nkNilLit: 
@@ -559,7 +559,7 @@ proc indirectAccess(a, b: PSym): PNode =
 proc transformLambda(c: PTransf, n: PNode): PNode = 
   var marked = initIntSet()
   result = n
-  if (n.sons[namePos].kind != nkSym): InternalError(n.info, "transformLambda")
+  if n.sons[namePos].kind != nkSym: InternalError(n.info, "transformLambda")
   var s = n.sons[namePos].sym
   var closure = newNodeI(nkRecList, n.sons[codePos].info)
   gatherVars(c, n.sons[codePos], marked, s, closure) 
diff --git a/lib/system/assign.nim b/lib/system/assign.nim
index 798409ba50..943d1f9bd3 100755
--- a/lib/system/assign.nim
+++ b/lib/system/assign.nim
@@ -7,6 +7,43 @@
 #    distribution, for details about the copyright.
 #
 
+proc checkTypeInfo*(dest: Pointer, src: int, mt: pointer)
+proc checkTypeInfo(dest: Pointer, src: int, n: ptr TNimNode) =
+  var
+    d = cast[TAddress](dest)
+    s = cast[TAddress](src)
+  case n.kind
+  of nkSlot: checkTypeInfo(cast[pointer](d +% n.offset), src, n.typ)
+  of nkList:
+    for i in 0..n.len-1: checkTypeInfo(dest, src, n.sons[i])
+  of nkCase:
+    var m = selectBranch(dest, n)
+    if m != nil: checkTypeInfo(dest, src, m)
+  else:
+    c_fprintf(cstdout, "ugh memory corruption! in check type info %ld\n", src)
+    quit 1
+  #of nkNone: assert(false)
+
+proc checkTypeInfo(dest: Pointer, src: int, mt: pointer) =
+  var mt = cast[PNimType](mt)
+  var
+    d = cast[TAddress](dest)
+    s = cast[TAddress](src)
+  assert(mt != nil)
+  case mt.Kind
+  of tyString: nil
+  of tySequence: nil
+  of tyObject, tyTuple, tyPureObject:
+    checkTypeInfo(dest, src, mt.node)
+  of tyArray, tyArrayConstr:
+    for i in 0..(mt.size div mt.base.size)-1:
+      checkTypeInfo(cast[pointer](d +% i*% mt.base.size),
+                    src, mt.base)
+  of tyRef: nil
+  else:
+    nil # copy raw bits
+
+
 proc genericAssignAux(dest, src: Pointer, mt: PNimType, shallow: bool)
 proc genericAssignAux(dest, src: Pointer, n: ptr TNimNode, shallow: bool) =
   var
diff --git a/tests/accept/compile/titer2.nim b/tests/accept/compile/titer2.nim
index 878ddf5e34..19c7298b0a 100644
--- a/tests/accept/compile/titer2.nim
+++ b/tests/accept/compile/titer2.nim
@@ -13,13 +13,24 @@ type
     data: TKeyValuePairSeq[A, B]
     counter: int
 
-proc len*[A, B](t: TTable[A, B]): int = 
-  result = t.counter
+iterator mycountup(a, b: int): int =
+  var res = a
+  while res <= b:
+    yield res
+    inc(res)
 
 iterator pairs*[A, B](t: TTable[A, B]): tuple[key: A, val: B] =
   ## iterates over any (key, value) pair in the table `t`.
-  for h in 0..high(t.data):
-    if t.data[h].slot == seFilled: yield (t.data[h].key, t.data[h].val)
+  var h = 0
+  while h <= high(t.data):
+    var k = t.data[h].key
+    if t.data[h].slot == seFilled: yield (k, t.data[h].val)
+    inc(h)
+  
+  when false:
+    for h in mycountup(0, high(t.data)):
+      var k = t.data[h].key
+      if t.data[h].slot == seFilled: yield (k, t.data[h].val)
 
 proc initTable*[A, B](initialSize=64): TTable[A, B] =
   ## creates a new hash table that is empty. `initialSize` needs to be
diff --git a/todo.txt b/todo.txt
index 068068bebb..424a32b103 100755
--- a/todo.txt
+++ b/todo.txt
@@ -1,14 +1,14 @@
 High priority (version 0.8.12)
 ==============================
-* implement message passing built-ins
-
-* add --deadlock_prevention:on|off switch? timeout for locks?
-* built-in serialization
-- bug: invoking a generic iterator twice triggers a code gen bug (titer2)
-- sorting with leads to a strange memory corruption!
+- sorting with leads to a strange memory corruption: tsimplesort
   --> system.swap or genericAssign is broken! And indeed, if reference counts
       are not modified and the GC is triggered in between a swap, bad things
       may happen!
+- bug: invoking a generic iterator twice triggers a code gen bug (titer2)
+* implement message passing built-ins
+* add --deadlock_prevention:on|off switch? timeout for locks?
+* built-in serialization
+
 
 
 version 0.9.0