diff --git a/compiler/ast.nim b/compiler/ast.nim
index 97f48b2531..172dd1fce4 100644
--- a/compiler/ast.nim
+++ b/compiler/ast.nim
@@ -597,7 +597,7 @@ const
     mIntToStr, mInt64ToStr, mFloatToStr, mCStrToStr, mStrToStr, mEnumToStr, 
     mAnd, mOr, mEqStr, mLeStr, mLtStr, mEqSet, mLeSet, mLtSet, mMulSet, 
     mPlusSet, mMinusSet, mSymDiffSet, mConStrStr, mConArrArr, mConArrT, 
-    mConTArr, mConTT, mSlice, 
+    mConTArr, mConTT,
     mAppendStrCh, mAppendStrStr, mAppendSeqElem, 
     mInRange, mInSet, mRepr,
     mRand, 
diff --git a/compiler/ccgcalls.nim b/compiler/ccgcalls.nim
index 84c5bf4199..a7840305dd 100644
--- a/compiler/ccgcalls.nim
+++ b/compiler/ccgcalls.nim
@@ -77,18 +77,38 @@ proc isInCurrentFrame(p: BProc, n: PNode): bool =
 
 proc openArrayLoc(p: BProc, n: PNode): PRope =
   var a: TLoc
-  initLocExpr(p, n, a)
-  case skipTypes(a.t, abstractVar).kind
-  of tyOpenArray, tyVarargs:
-    result = ropef("$1, $1Len0", [rdLoc(a)])
-  of tyString, tySequence:
-    if skipTypes(n.typ, abstractInst).kind == tyVar:
-      result = ropef("(*$1)->data, (*$1)->$2", [a.rdLoc, lenField()])
-    else:
-      result = ropef("$1->data, $1->$2", [a.rdLoc, lenField()])
-  of tyArray, tyArrayConstr:
-    result = ropef("$1, $2", [rdLoc(a), toRope(lengthOrd(a.t))])
-  else: internalError("openArrayLoc: " & typeToString(a.t))
+
+  let q = skipConv(n)
+  if getMagic(q) == mSlice:
+    # magic: pass slice to openArray:
+    var b, c: TLoc
+    initLocExpr(p, q[1], a)
+    initLocExpr(p, q[2], b)
+    initLocExpr(p, q[3], c)
+    let fmt =
+      case skipTypes(a.t, abstractVar).kind
+      of tyOpenArray, tyVarargs, tyArray, tyArrayConstr:
+        "($1)+($2), ($3)-($2)+1"
+      of tyString, tySequence:
+        if skipTypes(n.typ, abstractInst).kind == tyVar:
+          "(*$1)->data+($2), ($3)-($2)+1"
+        else:
+          "$1->data+($2), ($3)-($2)+1"
+      else: (internalError("openArrayLoc: " & typeToString(a.t)); "")
+    result = ropef(fmt, [rdLoc(a), rdLoc(b), rdLoc(c)])
+  else:
+    initLocExpr(p, n, a)
+    case skipTypes(a.t, abstractVar).kind
+    of tyOpenArray, tyVarargs:
+      result = ropef("$1, $1Len0", [rdLoc(a)])
+    of tyString, tySequence:
+      if skipTypes(n.typ, abstractInst).kind == tyVar:
+        result = ropef("(*$1)->data, (*$1)->$2", [a.rdLoc, lenField()])
+      else:
+        result = ropef("$1->data, $1->$2", [a.rdLoc, lenField()])
+    of tyArray, tyArrayConstr:
+      result = ropef("$1, $2", [rdLoc(a), toRope(lengthOrd(a.t))])
+    else: internalError("openArrayLoc: " & typeToString(a.t))
 
 proc genArgStringToCString(p: BProc, 
                            n: PNode): PRope {.inline.} =
diff --git a/compiler/parampatterns.nim b/compiler/parampatterns.nim
index e94068776c..bbdba8c225 100644
--- a/compiler/parampatterns.nim
+++ b/compiler/parampatterns.nim
@@ -10,7 +10,7 @@
 ## This module implements the pattern matching features for term rewriting
 ## macro support.
 
-import strutils, ast, astalgo, types, msgs, idents, renderer, wordrecg
+import strutils, ast, astalgo, types, msgs, idents, renderer, wordrecg, trees
 
 # we precompile the pattern here for efficiency into some internal
 # stack based VM :-) Why? Because it's fun; I did no benchmarks to see if that
@@ -215,6 +215,9 @@ proc isAssignable*(owner: PSym, n: PNode): TAssignableResult =
     result = arLValue
   of nkObjUpConv, nkObjDownConv, nkCheckedFieldExpr: 
     result = isAssignable(owner, n.sons[0])
+  of nkCallKinds:
+    # builtin slice keeps lvalue-ness:
+    if getMagic(n) == mSlice: result = isAssignable(owner, n.sons[1])
   else:
     discard
 
diff --git a/compiler/vmdef.nim b/compiler/vmdef.nim
index d0c38a2ad4..c391d8415f 100644
--- a/compiler/vmdef.nim
+++ b/compiler/vmdef.nim
@@ -207,7 +207,7 @@ const
   largeInstrs* = { # instructions which use 2 int32s instead of 1:
     opcSubStr, opcConv, opcCast, opcNewSeq, opcOf}
   slotSomeTemp* = slotTempUnknown
-  relativeJumps* = {opcTJmp, opcFJmp, opcJmp}
+  relativeJumps* = {opcTJmp, opcFJmp, opcJmp, opcJmpBack}
 
 template opcode*(x: TInstr): TOpcode {.immediate.} = TOpcode(x.uint32 and 0xff'u32)
 template regA*(x: TInstr): TRegister {.immediate.} = TRegister(x.uint32 shr 8'u32 and 0xff'u32)
diff --git a/compiler/vmgen.nim b/compiler/vmgen.nim
index 84577bb229..c5eb670251 100644
--- a/compiler/vmgen.nim
+++ b/compiler/vmgen.nim
@@ -1622,7 +1622,7 @@ proc genProc(c: PCtx; s: PSym): int =
     c.gABC(body, opcEof, eofInstr.regA)
     c.optimizeJumps(result)
     s.offset = c.prc.maxSlots
-    #if s.name.s == "addStuff":
+    #if s.name.s == "parse_until_symbol":
     #  echo renderTree(body)
     #  c.echoCode(result)
     c.prc = oldPrc
diff --git a/lib/system.nim b/lib/system.nim
index 6263f7b246..cfc8ceb6f4 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -2620,7 +2620,7 @@ proc `[]=`*[Idx, T](a: var array[Idx, T], x: TSlice[int], b: openArray[T]) =
   if L == b.len:
     for i in 0 .. <L: a[i+x.a] = b[i]
   else:
-    sysFatal(EOutOfRange, "differing lengths for slice assignment")
+    sysFatal(EOutOfRange, "different lengths for slice assignment")
 
 proc `[]`*[Idx, T](a: array[Idx, T], x: TSlice[Idx]): seq[T] =
   ## slice operation for arrays. Negative indexes are **not** supported
@@ -2642,7 +2642,7 @@ proc `[]=`*[Idx, T](a: var array[Idx, T], x: TSlice[Idx], b: openArray[T]) =
       a[j] = b[i]
       inc(j)
   else:
-    sysFatal(EOutOfRange, "differing lengths for slice assignment")
+    sysFatal(EOutOfRange, "different lengths for slice assignment")
 
 proc `[]`*[T](s: seq[T], x: TSlice[int]): seq[T] = 
   ## slice operation for sequences. Negative indexes are supported.
diff --git a/lib/system/gc_ms.nim b/lib/system/gc_ms.nim
index 410243528e..05bcdcc82c 100644
--- a/lib/system/gc_ms.nim
+++ b/lib/system/gc_ms.nim
@@ -313,6 +313,7 @@ proc mark(gch: var TGcHeap, c: PCell) =
       if not containsOrIncl(gch.marked, d):
         forAllChildren(d, waMarkPrecise)
   else:
+    # XXX no 'if c.refCount != rcBlack' here?
     c.refCount = rcBlack
     gcAssert gch.tempStack.len == 0, "stack not empty!"
     forAllChildren(c, waMarkPrecise)