diff --git a/compiler/semexprs.nim b/compiler/semexprs.nim
index 2d8d0e621..95a90463c 100644
--- a/compiler/semexprs.nim
+++ b/compiler/semexprs.nim
@@ -385,7 +385,8 @@ proc isOpImpl(c: PContext, n: PNode): PNode =
       result = newIntNode(nkIntLit, ord(t.kind == tyProc and
                                         t.callConv == ccClosure and
                                         tfIterator notin t.flags))
-    else: discard
+    else:
+      result = newIntNode(nkIntLit, 0)
   else:
     var t2 = n[2].typ.skipTypes({tyTypeDesc})
     maybeLiftType(t2, c, n.info)
@@ -1434,20 +1435,15 @@ proc semYield(c: PContext, n: PNode): PNode =
     var iterType = c.p.owner.typ
     let restype = iterType.sons[0]
     if restype != nil:
-      let adjustedRes = if restype.kind == tyIter: restype.base
-                        else: restype
-      if adjustedRes.kind != tyExpr:
-        n.sons[0] = fitNode(c, adjustedRes, n.sons[0])
+      if restype.kind != tyExpr:
+        n.sons[0] = fitNode(c, restype, n.sons[0])
       if n.sons[0].typ == nil: internalError(n.info, "semYield")
 
-      if resultTypeIsInferrable(adjustedRes):
+      if resultTypeIsInferrable(restype):
         let inferred = n.sons[0].typ
-        if restype.kind == tyIter:
-          restype.sons[0] = inferred
-        else:
-          iterType.sons[0] = inferred
+        iterType.sons[0] = inferred
 
-      semYieldVarResult(c, n, adjustedRes)
+      semYieldVarResult(c, n, restype)
     else:
       localError(n.info, errCannotReturnExpr)
   elif c.p.owner.typ.sons[0] != nil:
@@ -2184,7 +2180,7 @@ proc semExpr(c: PContext, n: PNode, flags: TExprFlags = {}): PNode =
     message(n.info, warnDeprecated, "bind")
     result = semExpr(c, n.sons[0], flags)
   of nkTypeOfExpr, nkTupleTy, nkTupleClassTy, nkRefTy..nkEnumTy, nkStaticTy:
-    var typ = semTypeNode(c, n, nil).skipTypes({tyTypeDesc, tyIter})
+    var typ = semTypeNode(c, n, nil).skipTypes({tyTypeDesc})
     result.typ = makeTypeDesc(c, typ)
     #result = symNodeFromType(c, typ, n.info)
   of nkCall, nkInfix, nkPrefix, nkPostfix, nkCommand, nkCallStrLit:
@@ -2257,7 +2253,7 @@ proc semExpr(c: PContext, n: PNode, flags: TExprFlags = {}): PNode =
       var tupexp = semTuplePositionsConstr(c, n, flags)
       if isTupleType(tupexp):
         # reinterpret as type
-        var typ = semTypeNode(c, n, nil).skipTypes({tyTypeDesc, tyIter})
+        var typ = semTypeNode(c, n, nil).skipTypes({tyTypeDesc})
         result.typ = makeTypeDesc(c, typ)
       else:
         result = tupexp
diff --git a/compiler/semstmts.nim b/compiler/semstmts.nim
index ebea2dd67..e80f1cfda 100644
--- a/compiler/semstmts.nim
+++ b/compiler/semstmts.nim
@@ -540,7 +540,7 @@ proc symForVar(c: PContext, n: PNode): PSym =
 proc semForVars(c: PContext, n: PNode): PNode =
   result = n
   var length = sonsLen(n)
-  let iterBase = n.sons[length-2].typ.skipTypes({tyIter})
+  let iterBase = n.sons[length-2].typ
   var iter = skipTypes(iterBase, {tyGenericInst})
   # length == 3 means that there is one for loop variable
   # and thus no tuple unpacking:
@@ -594,8 +594,7 @@ proc semFor(c: PContext, n: PNode): PNode =
       result.kind = nkParForStmt
     else:
       result = semForFields(c, n, call.sons[0].sym.magic)
-  elif (isCallExpr and call.sons[0].typ.callConv == ccClosure) or
-      call.typ.kind == tyIter:
+  elif isCallExpr and call.sons[0].typ.callConv == ccClosure:
     # first class iterator:
     result = semForVars(c, n)
   elif not isCallExpr or call.sons[0].kind != nkSym or
diff --git a/compiler/semtypes.nim b/compiler/semtypes.nim
index 683b6455f..65edb756f 100644
--- a/compiler/semtypes.nim
+++ b/compiler/semtypes.nim
@@ -832,15 +832,6 @@ proc liftParamType(c: PContext, procKind: TSymKind, genericParams: PNode,
     result = newTypeWithSons(c, tyCompositeTypeClass, @[paramType, result])
     result = addImplicitGeneric(result)
 
-  of tyIter:
-    if paramType.callConv == ccInline:
-      if procKind notin {skTemplate, skMacro, skIterator}:
-        localError(info, errInlineIteratorsAsProcParams)
-      if paramType.len == 1:
-        let lifted = liftingWalk(paramType.base)
-        if lifted != nil: paramType.sons[0] = lifted
-      result = addImplicitGeneric(paramType)
-
   of tyGenericInst:
     if paramType.lastSon.kind == tyUserTypeClass:
       var cp = copyType(paramType, getCurrOwner(), false)
@@ -998,7 +989,6 @@ proc semProcTypeNode(c: PContext, n, genericParams: PNode,
           # in cases like iterator foo(it: iterator): type(it)
           # we don't need to change the return type to iter[T]
           result.flags.incl tfIterator
-          #if not r.isInlineIterator: r = newTypeWithSons(c, tyIter, @[r])
           # XXX Would be nice if we could get rid of this
       result.sons[0] = r
       result.n.typ = r
@@ -1154,7 +1144,7 @@ proc semTypeNode(c: PContext, n: PNode, prev: PType): PType =
     # for ``type(countup(1,3))``, see ``tests/ttoseq``.
     checkSonsLen(n, 1)
     let typExpr = semExprWithType(c, n.sons[0], {efInTypeof})
-    result = typExpr.typ.skipTypes({tyIter})
+    result = typExpr.typ
   of nkPar:
     if sonsLen(n) == 1: result = semTypeNode(c, n.sons[0], prev)
     else:
@@ -1220,7 +1210,7 @@ proc semTypeNode(c: PContext, n: PNode, prev: PType): PType =
       elif op.id == ord(wType):
         checkSonsLen(n, 2)
         let typExpr = semExprWithType(c, n.sons[1], {efInTypeof})
-        result = typExpr.typ.skipTypes({tyIter})
+        result = typExpr.typ
       else:
         result = semTypeExpr(c, n)
   of nkWhenStmt:
@@ -1301,14 +1291,16 @@ proc semTypeNode(c: PContext, n: PNode, prev: PType): PType =
     result.flags.incl tfHasStatic
   of nkIteratorTy:
     if n.sonsLen == 0:
-      result = newConstraint(c, tyIter)
+      result = newTypeS(tyBuiltInTypeClass, c)
+      let child = newTypeS(tyProc, c)
+      child.flags.incl tfIterator
+      result.addSonSkipIntLit(child)
     else:
       result = semProcTypeWithScope(c, n, prev, skClosureIterator)
+      result.flags.incl(tfIterator)
       if n.lastSon.kind == nkPragma and hasPragma(n.lastSon, wInline):
-        result.kind = tyIter
         result.callConv = ccInline
       else:
-        result.flags.incl(tfIterator)
         result.callConv = ccClosure
   of nkProcTy:
     if n.sonsLen == 0:
diff --git a/compiler/semtypinst.nim b/compiler/semtypinst.nim
index 7957ac50a..20b60a88d 100644
--- a/compiler/semtypinst.nim
+++ b/compiler/semtypinst.nim
@@ -77,7 +77,7 @@ proc cacheTypeInst*(inst: PType) =
   #      update the refcount
   let gt = inst.sons[0]
   let t = if gt.kind == tyGenericBody: gt.lastSon else: gt
-  if t.kind in {tyStatic, tyGenericParam, tyIter} + tyTypeClasses:
+  if t.kind in {tyStatic, tyGenericParam} + tyTypeClasses:
     return
   gt.sym.typeInstCache.safeAdd(inst)
 
@@ -390,7 +390,7 @@ proc replaceTypeVarsTAux(cl: var TReplTypeVars, t: PType): PType =
   result = t
   if t == nil: return
 
-  if t.kind in {tyStatic, tyGenericParam, tyIter} + tyTypeClasses:
+  if t.kind in {tyStatic, tyGenericParam} + tyTypeClasses:
     let lookup = PType(idTableGet(cl.typeMap, t))
     if lookup != nil: return lookup
 
diff --git a/compiler/sigmatch.nim b/compiler/sigmatch.nim
index 9fda8c860..aee42e021 100644
--- a/compiler/sigmatch.nim
+++ b/compiler/sigmatch.nim
@@ -1256,10 +1256,6 @@ proc localConvMatch(c: PContext, m: var TCandidate, f, a: PType,
       result.typ = getInstantiatedType(c, arg, m, base(f))
     m.baseTypeMatch = true
 
-proc isInlineIterator*(t: PType): bool =
-  result = t.kind == tyIter or
-          (t.kind == tyBuiltInTypeClass and t.base.kind == tyIter)
-
 proc incMatches(m: var TCandidate; r: TTypeRelation; convMatch = 1) =
   case r
   of isConvertible, isIntConv: inc(m.convMatches, convMatch)
@@ -1323,13 +1319,6 @@ proc paramTypesMatchAux(m: var TCandidate, f, argType: PType,
     else:
       return argSemantized # argOrig
 
-  if r != isNone and f.isInlineIterator:
-    var inlined = newTypeS(tyStatic, c)
-    inlined.sons = @[argType]
-    inlined.n = argSemantized
-    put(m.bindings, f, inlined)
-    return argSemantized
-
   # If r == isBothMetaConvertible then we rerun typeRel.
   # bothMetaCounter is for safety to avoid any infinite loop,
   #  I don't have any example when it is needed.
diff --git a/compiler/transf.nim b/compiler/transf.nim
index 3d78a6b92..3a5ff982e 100644
--- a/compiler/transf.nim
+++ b/compiler/transf.nim
@@ -478,9 +478,8 @@ proc transformFor(c: PTransf, n: PNode): PTransNode =
     result[1] = newNode(nkEmpty).PTransNode
     return result
   c.breakSyms.add(labl)
-  if call.typ.kind != tyIter and
-    (call.kind notin nkCallKinds or call.sons[0].kind != nkSym or
-      call.sons[0].sym.kind != skIterator):
+  if call.kind notin nkCallKinds or call.sons[0].kind != nkSym or
+      call.sons[0].sym.kind != skIterator:
     n.sons[length-1] = transformLoopBody(c, n.sons[length-1]).PNode
     result[1] = lambdalifting.liftForLoop(n).PTransNode
     discard c.breakSyms.pop
@@ -512,7 +511,6 @@ proc transformFor(c: PTransf, n: PNode): PTransNode =
   for i in countup(1, sonsLen(call) - 1):
     var arg = transform(c, call.sons[i]).PNode
     var formal = skipTypes(iter.typ, abstractInst).n.sons[i].sym
-    if arg.typ.kind == tyIter: continue
     case putArgInto(arg, formal.typ)
     of paDirectMapping:
       idNodeTablePut(newC.mapping, formal, arg)
diff --git a/doc/manual/generics.txt b/doc/manual/generics.txt
index a73e22988..07d98b289 100644
--- a/doc/manual/generics.txt
+++ b/doc/manual/generics.txt
@@ -213,7 +213,7 @@ Concepts are written in the following form:
 
     Container[T] = concept c
       c.len is Ordinal
-      items(c) is iterator
+      items(c) is T
       for value in c:
         type(value) is T
 
diff --git a/lib/system/gc2.nim b/lib/system/gc2.nim
index 705812b56..e68a8586e 100644
--- a/lib/system/gc2.nim
+++ b/lib/system/gc2.nim
@@ -13,6 +13,8 @@
 # and sweep GC to free cycles. It is hard realtime in that if you play
 # according to its rules, no deadline will ever be missed.
 
+# XXX Ensure by smart color masking that the object is not in the ZCT.
+
 when defined(nimCoroutines):
   import arch
 
diff --git a/tests/concepts/tmanual.nim b/tests/concepts/tmanual.nim
index 7cf08af06..43290a6ad 100644
--- a/tests/concepts/tmanual.nim
+++ b/tests/concepts/tmanual.nim
@@ -23,7 +23,7 @@ template reject(e: expr) =
 type
   Container[T] = concept c
     c.len is Ordinal
-    items(c) is iterator
+    items(c) is T
     for value in c:
       type(value) is T
 
diff --git a/web/news.txt b/web/news.txt
index 7765733a9..67a7782cb 100644
--- a/web/news.txt
+++ b/web/news.txt
@@ -16,6 +16,9 @@ News
     actually work with the bool datatype.
   - when compiling to JS, ``Node``, ``NodeType`` and ``Document`` are no longer
     defined. Use the types defined in ``dom.nim`` instead.
+  - The check ``x is iterator`` (used for instance in concepts) was always a
+    weird special case (you could not use ``x is proc``) and was removed from
+    the language.
 
 
 2015-10-27 Version 0.12.0 released