Merge branch 'devel' of https://github.com/Araq/Nimrod into devel

16 files changed, 231 insertions, 98 deletions

diff --git a/compiler/c2nim/cparse.nim b/compiler/c2nim/cparse.nim
index ffab05788..e4abe11a0 100644
--- a/compiler/c2nim/cparse.nim
+++ b/compiler/c2nim/cparse.nim
@@ -540,7 +540,7 @@ proc typeAtom(p: var TParser): PNode =
       if p.tok.s == "unsigned":
         isUnsigned = true
       elif p.tok.s == "signed" or p.tok.s == "int":
-        nil
+        discard
       else:
         add(x, p.tok.s)
       getTok(p, nil)
@@ -746,7 +746,7 @@ proc directDeclarator(p: var TParser, a: PNode, ident: ptr PNode): PNode =
       result = declarator(p, a, ident)
       eat(p, pxParRi, result)
   else:
-    nil
+    discard
   return parseTypeSuffix(p, a)
 
 proc declarator(p: var TParser, a: PNode, ident: ptr PNode): PNode =
@@ -1165,7 +1165,7 @@ proc enumSpecifier(p: var TParser): PNode =
 
 proc setBaseFlags(n: PNode, base: TNumericalBase) = 
   case base
-  of base10: nil
+  of base10: discard
   of base2: incl(n.flags, nfBase2)
   of base8: incl(n.flags, nfBase8)
   of base16: incl(n.flags, nfBase16)
@@ -1686,7 +1686,7 @@ proc switchStatement(p: var TParser): PNode =
       break
     of "case", "default":
       break
-    else: nil
+    else: discard
     addSon(result, statement(p))
   if sonsLen(result) == 0:
     # translate empty statement list to Nimrod's ``nil`` statement
diff --git a/compiler/c2nim/cpp.nim b/compiler/c2nim/cpp.nim
index 1707b75db..84b4c4dfb 100644
--- a/compiler/c2nim/cpp.nim
+++ b/compiler/c2nim/cpp.nim
@@ -103,7 +103,7 @@ proc parseDefBody(p: var TParser, m: var TMacro, params: seq[string]) =
       m.body.add(tok)
     of pxDirConc: 
       # just ignore this token: this implements token merging correctly
-      nil
+      discard
     else:
       m.body.add(p.tok)
     # we do not want macro expansion here:
@@ -166,7 +166,7 @@ proc parseStmtList(p: var TParser): PNode =
     of pxDirectiveParLe, pxDirective: 
       case p.tok.s
       of "else", "endif", "elif": break
-    else: nil
+    else: discard
     addSon(result, statement(p))
   
 proc eatEndif(p: var TParser) =
diff --git a/compiler/msgs.nim b/compiler/msgs.nim
index 61336aa87..0140d1ac4 100644
--- a/compiler/msgs.nim
+++ b/compiler/msgs.nim
@@ -88,7 +88,8 @@ type
     errTemplateInstantiationTooNested, errInstantiationFrom, 
     errInvalidIndexValueForTuple, errCommandExpectsFilename,
     errMainModuleMustBeSpecified,
-    errXExpected, 
+    errXExpected,
+    errTIsNotAConcreteType,
     errInvalidSectionStart, errGridTableNotImplemented, errGeneralParseError, 
     errNewSectionExpected, errWhitespaceExpected, errXisNoValidIndexFile, 
     errCannotRenderX, errVarVarTypeNotAllowed, errInstantiateXExplicitely,
@@ -103,6 +104,7 @@ type
     errXhasSideEffects, errIteratorExpected, errLetNeedsInit,
     errThreadvarCannotInit, errWrongSymbolX, errIllegalCaptureX,
     errXCannotBeClosure, errXMustBeCompileTime,
+    errCannotInferTypeOfTheLiteral,
     errUser,
     warnCannotOpenFile, 
     warnOctalEscape, warnXIsNeverRead, warnXmightNotBeenInit, 
@@ -312,6 +314,7 @@ const
     errCommandExpectsFilename: "command expects a filename argument",
     errMainModuleMustBeSpecified: "please, specify a main module in the project configuration file",
     errXExpected: "\'$1\' expected", 
+    errTIsNotAConcreteType: "\'$1\' is not a concrete type.",
     errInvalidSectionStart: "invalid section start",
     errGridTableNotImplemented: "grid table is not implemented", 
     errGeneralParseError: "general parse error",
@@ -346,6 +349,7 @@ const
     errIllegalCaptureX: "illegal capture '$1'",
     errXCannotBeClosure: "'$1' cannot have 'closure' calling convention",
     errXMustBeCompileTime: "'$1' can only be used in compile-time context",
+    errCannotInferTypeOfTheLiteral: "cannot infer the type of the $1",
     errUser: "$1", 
     warnCannotOpenFile: "cannot open \'$1\' [CannotOpenFile]",
     warnOctalEscape: "octal escape sequences do not exist; leading zero is ignored [OctalEscape]", 
diff --git a/compiler/pas2nim/paslex.nim b/compiler/pas2nim/paslex.nim
index 67473e71f..f24b0c420 100644
--- a/compiler/pas2nim/paslex.nim
+++ b/compiler/pas2nim/paslex.nim
@@ -342,7 +342,7 @@ proc getSymbol(L: var TLexer, tok: var TToken) =
       h = h +% ord(c)
       h = h +% h shl 10
       h = h xor (h shr 6)
-    of '_': nil
+    of '_': discard
     else: break
     inc(pos)
   h = h +% h shl 3
diff --git a/compiler/pas2nim/pasparse.nim b/compiler/pas2nim/pasparse.nim
index 928896338..a6f8363f6 100644
--- a/compiler/pas2nim/pasparse.nim
+++ b/compiler/pas2nim/pasparse.nim
@@ -335,7 +335,7 @@ proc exprColonEqExprList(p: var TParser, kind, elemKind: TNodeKind,
 
 proc setBaseFlags(n: PNode, base: TNumericalBase) = 
   case base
-  of base10: nil
+  of base10: discard
   of base2: incl(n.flags, nfBase2)
   of base8: incl(n.flags, nfBase8)
   of base16: incl(n.flags, nfBase16)
@@ -466,7 +466,7 @@ proc lowestExprAux(p: var TParser, v: var PNode, limit: int): TTokKind =
         eat(p, pxCurlyDirRi)
         opNode.ident = getIdent("&")
       else: 
-        nil
+        discard
     of pxMinus: 
       if p.tok.xkind == pxPer: 
         getTok(p)
@@ -477,7 +477,7 @@ proc lowestExprAux(p: var TParser, v: var PNode, limit: int): TTokKind =
     of pxNeq: 
       opNode.ident = getIdent("!=")
     else: 
-      nil
+      discard
     skipCom(p, opNode)        # read sub-expression with higher priority
     nextop = lowestExprAux(p, v2, opPred)
     addSon(node, opNode)
@@ -505,7 +505,7 @@ proc fixExpr(n: PNode): PNode =
             (n.sons[2].kind in {nkCharLit, nkStrLit}): 
           n.sons[0].ident = getIdent("&") # fix operator
   else: 
-    nil
+    discard
   if not (n.kind in {nkEmpty..nkNilLit}): 
     for i in countup(0, sonsLen(n) - 1): result.sons[i] = fixExpr(n.sons[i])
   
@@ -603,7 +603,7 @@ proc parseStmtList(p: var TParser): PNode =
     of pxCurlyDirLe, pxStarDirLe: 
       if not isHandledDirective(p): break 
     else: 
-      nil
+      discard
     addSon(result, parseStmt(p))
   if sonsLen(result) == 1: result = result.sons[0]
   
@@ -732,7 +732,7 @@ proc parseRepeat(p: var TParser): PNode =
   addSon(b, c)
   addSon(a, b)
   if b.sons[0].kind == nkIdent and b.sons[0].ident.id == getIdent("false").id: 
-    nil
+    discard
   else: 
     addSon(s, a)
   addSon(result, s)
@@ -840,7 +840,7 @@ proc parseParam(p: var TParser): PNode =
     getTok(p)
     v = newNodeP(nkVarTy, p)
   else: 
-    nil
+    discard
   while true: 
     case p.tok.xkind
     of pxSymbol: a = createIdentNodeP(p.tok.ident, p)
@@ -1133,7 +1133,7 @@ proc parseRecordPart(p: var TParser): PNode =
 proc exSymbol(n: var PNode) = 
   case n.kind
   of nkPostfix: 
-    nil
+    discard
   of nkPragmaExpr: 
     exSymbol(n.sons[0])
   of nkIdent, nkAccQuoted: 
@@ -1154,7 +1154,7 @@ proc fixRecordDef(n: var PNode) =
     for i in countup(0, sonsLen(n) - 1): fixRecordDef(n.sons[i])
   of nkIdentDefs: 
     for i in countup(0, sonsLen(n) - 3): exSymbol(n.sons[i])
-  of nkNilLit, nkEmpty: nil
+  of nkNilLit, nkEmpty: discard
   else: internalError(n.info, "fixRecordDef(): " & $n.kind)
   
 proc addPragmaToIdent(ident: var PNode, pragma: PNode) = 
@@ -1191,7 +1191,7 @@ proc parseRecordBody(p: var TParser, result, definition: PNode) =
     if definition != nil: addPragmaToIdent(definition.sons[0], parseCommand(p))
     else: internalError(result.info, "anonymous record is not supported")
   else: 
-    nil
+    discard
   opt(p, pxSemicolon)
   skipCom(p, result)
 
@@ -1399,7 +1399,7 @@ proc fixVarSection(p: var TParser, counter: PNode) =
 
 proc exSymbols(n: PNode) = 
   case n.kind
-  of nkEmpty..nkNilLit: nil
+  of nkEmpty..nkNilLit: discard
   of nkProcDef..nkIteratorDef: exSymbol(n.sons[namePos])
   of nkWhenStmt, nkStmtList: 
     for i in countup(0, sonsLen(n) - 1): exSymbols(n.sons[i])
@@ -1410,7 +1410,7 @@ proc exSymbols(n: PNode) =
       exSymbol(n.sons[i].sons[0])
       if n.sons[i].sons[2].kind == nkObjectTy: 
         fixRecordDef(n.sons[i].sons[2])
-  else: nil
+  else: discard
 
 proc parseBegin(p: var TParser, result: PNode) = 
   getTok(p)
diff --git a/compiler/pragmas.nim b/compiler/pragmas.nim
index d9ed50cfe..75c16f6cd 100644
--- a/compiler/pragmas.nim
+++ b/compiler/pragmas.nim
@@ -97,8 +97,25 @@ proc makeExternImport(s: PSym, extname: string) =
   incl(s.flags, sfImportc)
   excl(s.flags, sfForward)
 
-proc makeExternExport(s: PSym, extname: string) = 
+const invalidIdentChars = AllChars - IdentChars
+
+proc validateExternCName(s: PSym, info: TLineInfo) =
+  ## Validates that the symbol name in s.loc.r is a valid C identifier.
+  ##
+  ## Valid identifiers are those alphanumeric including the underscore not
+  ## starting with a number. If the check fails, a generic error will be
+  ## displayed to the user.
+  let target = ropeToStr(s.loc.r)
+  if target.len < 1 or (not (target[0] in IdentStartChars)) or
+      (not target.allCharsInSet(IdentChars)):
+    localError(info, errGenerated, "invalid exported symbol")
+
+proc makeExternExport(s: PSym, extname: string, info: TLineInfo) =
   setExternName(s, extname)
+  case gCmd
+  of cmdCompileToC, cmdCompileToCpp, cmdCompileToOC:
+    validateExternCName(s, info)
+  else: discard
   incl(s.flags, sfExportc)
 
 proc processImportCompilerProc(s: PSym, extname: string) =
@@ -515,7 +532,7 @@ proc singlePragma(c: PContext, sym: PSym, n: PNode, i: int,
       if k in validPragmas: 
         case k
         of wExportc: 
-          makeExternExport(sym, getOptionalStr(c, it, "$1"))
+          makeExternExport(sym, getOptionalStr(c, it, "$1"), it.info)
           incl(sym.flags, sfUsed) # avoid wrong hints
         of wImportc: makeExternImport(sym, getOptionalStr(c, it, "$1"))
         of wImportCompilerProc:
@@ -601,7 +618,7 @@ proc singlePragma(c: PContext, sym: PSym, n: PNode, i: int,
           processDynLib(c, it, sym)
         of wCompilerproc: 
           noVal(it)           # compilerproc may not get a string!
-          makeExternExport(sym, "$1")
+          makeExternExport(sym, "$1", it.info)
           incl(sym.flags, sfCompilerProc)
           incl(sym.flags, sfUsed) # suppress all those stupid warnings
           registerCompilerProc(sym)
diff --git a/compiler/sem.nim b/compiler/sem.nim
index 140687721..09b2511f1 100644
--- a/compiler/sem.nim
+++ b/compiler/sem.nim
@@ -333,6 +333,7 @@ proc myOpen(module: PSym): PPassContext =
   c.semOperand = semOperand
   c.semConstBoolExpr = semConstBoolExpr
   c.semOverloadedCall = semOverloadedCall
+  c.semInferredLambda = semInferredLambda
   c.semGenerateInstance = generateInstance
   c.semTypeNode = semTypeNode
   pushProcCon(c, module)
diff --git a/compiler/semdata.nim b/compiler/semdata.nim
index 234526054..df58c896f 100644
--- a/compiler/semdata.nim
+++ b/compiler/semdata.nim
@@ -81,6 +81,7 @@ type
     semOverloadedCall*: proc (c: PContext, n, nOrig: PNode,
                               filter: TSymKinds): PNode {.nimcall.}
     semTypeNode*: proc(c: PContext, n: PNode, prev: PType): PType {.nimcall.}
+    semInferredLambda*: proc(c: PContext, pt: TIdTable, n: PNode): PNode
     semGenerateInstance*: proc (c: PContext, fn: PSym, pt: TIdTable,
                                 info: TLineInfo): PSym
     includedFiles*: TIntSet    # used to detect recursive include files
diff --git a/compiler/semexprs.nim b/compiler/semexprs.nim
index f09ee1295..c271911ab 100644
--- a/compiler/semexprs.nim
+++ b/compiler/semexprs.nim
@@ -1829,8 +1829,8 @@ proc semExpr(c: PContext, n: PNode, flags: TExprFlags = {}): PNode =
       result = symChoice(c, n, s, scClosed)
       if result.kind == nkSym:
         markIndirect(c, result.sym)
-        if isGenericRoutine(result.sym):
-          localError(n.info, errInstantiateXExplicitely, s.name.s)
+        # if isGenericRoutine(result.sym):
+        #   localError(n.info, errInstantiateXExplicitely, s.name.s)
   of nkSym:
     # because of the changed symbol binding, this does not mean that we
     # don't have to check the symbol for semantics here again!
diff --git a/compiler/semstmts.nim b/compiler/semstmts.nim
index 0871b7fb7..6c4e29f29 100644
--- a/compiler/semstmts.nim
+++ b/compiler/semstmts.nim
@@ -143,10 +143,11 @@ proc discardCheck(c: PContext, result: PNode) =
       while n.kind in skipForDiscardable:
         n = n.lastSon
         n.typ = nil
-    elif c.inTypeClass > 0 and result.typ.kind == tyBool:
-      let verdict = semConstExpr(c, result)
-      if verdict.intVal == 0:
-        localError(result.info, "type class predicate failed")
+    elif c.inTypeClass > 0:
+      if result.typ.kind == tyBool:
+        let verdict = semConstExpr(c, result)
+        if verdict.intVal == 0:
+          localError(result.info, "type class predicate failed")
     elif result.typ.kind != tyError and gCmd != cmdInteractive:
       if result.typ.kind == tyNil:
         fixNilType(result)
@@ -349,7 +350,12 @@ proc semVarOrLet(c: PContext, n: PNode, symkind: TSymKind): PNode =
       # BUGFIX: ``fitNode`` is needed here!
       # check type compability between def.typ and typ:
       if typ != nil: def = fitNode(c, typ, def)
-      else: typ = skipIntLit(def.typ)
+      else:
+        typ = skipIntLit(def.typ)
+        if typ.kind in {tySequence, tyArray, tySet} and
+           typ.lastSon.kind == tyEmpty:
+          localError(def.info, errCannotInferTypeOfTheLiteral,
+                     ($typ.kind).substr(2).toLower)
     else:
       def = ast.emptyNode
       if symkind == skLet: localError(a.info, errLetNeedsInit)
@@ -764,6 +770,29 @@ proc typeSectionRightSidePass(c: PContext, n: PNode) =
       s.ast = a
       popOwner()
 
+proc checkForMetaFields(n: PNode) =
+  template checkMeta(t) =
+    if t != nil and t.isMetaType and tfGenericTypeParam notin t.flags:
+      localError(n.info, errTIsNotAConcreteType, t.typeToString)
+  
+  case n.kind
+  of nkRecList, nkRecCase:
+    for s in n: checkForMetaFields(s)
+  of nkOfBranch, nkElse:
+    checkForMetaFields(n.lastSon)
+  of nkSym:
+    let t = n.sym.typ
+    case t.kind
+    of tySequence, tySet, tyArray, tyOpenArray, tyVar, tyPtr, tyRef,
+       tyProc, tyGenericInvokation, tyGenericInst:
+      let start = ord(t.kind in {tyGenericInvokation, tyGenericInst})
+      for i in start .. <t.sons.len:
+        checkMeta(t.sons[i])
+    else:
+      checkMeta(t)
+  else:
+    internalAssert false
+
 proc typeSectionFinalPass(c: PContext, n: PNode) = 
   for i in countup(0, sonsLen(n) - 1): 
     var a = n.sons[i]
@@ -780,6 +809,8 @@ proc typeSectionFinalPass(c: PContext, n: PNode) =
           assignType(s.typ, t)
           s.typ.id = t.id     # same id
       checkConstructedType(s.info, s.typ)
+      if s.typ.kind in {tyObject, tyTuple}:
+        checkForMetaFields(s.typ.n)
     let aa = a.sons[2]
     if aa.kind in {nkRefTy, nkPtrTy} and aa.len == 1 and
        aa.sons[0].kind == nkObjectTy:
@@ -883,12 +914,19 @@ proc semLambda(c: PContext, n: PNode, flags: TExprFlags): PNode =
     s = n[namePos].sym
   pushOwner(s)
   openScope(c)
-  if n.sons[genericParamsPos].kind != nkEmpty:
-    illFormedAst(n)           # process parameters:
+  var gp: PNode
+  if n.sons[genericParamsPos].kind != nkEmpty: 
+    n.sons[genericParamsPos] = semGenericParamList(c, n.sons[genericParamsPos])
+    gp = n.sons[genericParamsPos]
+  else:
+    gp = newNodeI(nkGenericParams, n.info)
+
   if n.sons[paramsPos].kind != nkEmpty:
-    var gp = newNodeI(nkGenericParams, n.info)
     semParamList(c, n.sons[paramsPos], gp, s)
-    paramsTypeCheck(c, s.typ)
+    # paramsTypeCheck(c, s.typ)
+    if sonsLen(gp) > 0 and n.sons[genericParamsPos].kind == nkEmpty:
+      # we have a list of implicit type parameters:
+      n.sons[genericParamsPos] = gp
   else:
     s.typ = newTypeS(tyProc, c)
     rawAddSon(s.typ, nil)
@@ -900,12 +938,13 @@ proc semLambda(c: PContext, n: PNode, flags: TExprFlags): PNode =
       localError(n.sons[bodyPos].info, errImplOfXNotAllowed, s.name.s)
     #if efDetermineType notin flags:
     # XXX not good enough; see tnamedparamanonproc.nim
-    pushProcCon(c, s)
-    addResult(c, s.typ.sons[0], n.info, skProc)
-    let semBody = hloBody(c, semProcBody(c, n.sons[bodyPos]))
-    n.sons[bodyPos] = transformBody(c.module, semBody, s)
-    addResultNode(c, n)
-    popProcCon(c)
+    if n.sons[genericParamsPos].kind == nkEmpty:
+      pushProcCon(c, s)
+      addResult(c, s.typ.sons[0], n.info, skProc)
+      let semBody = hloBody(c, semProcBody(c, n.sons[bodyPos]))
+      n.sons[bodyPos] = transformBody(c.module, semBody, s)
+      addResultNode(c, n)
+      popProcCon(c)
     sideEffectsCheck(c, s)
   else:
     localError(n.info, errImplOfXexpected, s.name.s)
@@ -913,6 +952,34 @@ proc semLambda(c: PContext, n: PNode, flags: TExprFlags): PNode =
   popOwner()
   result.typ = s.typ
 
+proc semInferredLambda(c: PContext, pt: TIdTable, n: PNode): PNode =
+  var n = n
+  
+  n = replaceTypesInBody(c, pt, n)
+  result = n
+  
+  n.sons[genericParamsPos] = emptyNode
+  n.sons[paramsPos] = n.typ.n
+  
+  openScope(c)
+  var s = n.sons[namePos].sym
+  addParams(c, n.typ.n, skProc)
+  pushProcCon(c, s)
+  addResult(c, n.typ.sons[0], n.info, skProc)
+  let semBody = hloBody(c, semProcBody(c, n.sons[bodyPos]))
+  n.sons[bodyPos] = transformBody(c.module, semBody, n.sons[namePos].sym)
+  addResultNode(c, n)
+  popProcCon(c)
+  closeScope(c)
+  
+  s.ast = result
+
+  # alternative variant (not quite working):
+  # var prc = arg[0].sym
+  # let inferred = c.semGenerateInstance(c, prc, m.bindings, arg.info)
+  # result = inferred.ast
+  # result.kind = arg.kind
+
 proc activate(c: PContext, n: PNode) =
   # XXX: This proc is part of my plan for getting rid of
   # forward declarations. stay tuned.
@@ -1263,8 +1330,8 @@ proc semStmtList(c: PContext, n: PNode, flags: TExprFlags): PNode =
         let (outer, inner) = insertDestructors(c, n.sons[i])
         if outer != nil:
           n.sons[i] = outer
-          for j in countup(i+1, length-1):
-            inner.addSon(semStmt(c, n.sons[j]))
+          var rest = newNode(nkStmtList, n.info, n.sons[i+1 .. length-1])
+          inner.addSon(semStmtList(c, rest, flags))
           n.sons.setLen(i+1)
           return
       of LastBlockStmts: 
diff --git a/compiler/semtypes.nim b/compiler/semtypes.nim
index 184aca4f8..0eba602cc 100644
--- a/compiler/semtypes.nim
+++ b/compiler/semtypes.nim
@@ -669,7 +669,7 @@ proc liftParamType(c: PContext, procKind: TSymKind, genericParams: PNode,
   of tyTypeDesc:
     if tfUnresolved notin paramType.flags:
       # naked typedescs are not bindOnce types
-      if paramType.sonsLen == 0 and paramTypId != nil and
+      if paramType.base.kind == tyNone and paramTypId != nil and
          paramTypId.id == typedescId.id: paramTypId = nil
       result = addImplicitGeneric(c.newTypeWithSons(tyTypeDesc, paramType.sons))
   
@@ -705,7 +705,6 @@ proc liftParamType(c: PContext, procKind: TSymKind, genericParams: PNode,
       # result.rawAddSon(copyType(paramType.sons[i], getCurrOwner(), true))
     result = instGenericContainer(c, paramType.sym.info, result,
                                   allowMetaTypes = true)
-    result.lastSon.shouldHaveMeta
     result = newTypeWithSons(c, tyCompositeTypeClass, @[paramType, result])
     result = addImplicitGeneric(result)
   
@@ -1011,7 +1010,8 @@ proc semTypeNode(c: PContext, n: PNode, prev: PType): PType =
     of mOrdinal: result = semOrdinal(c, n, prev)
     of mSeq: result = semContainer(c, n, tySequence, "seq", prev)
     of mVarargs: result = semVarargs(c, n, prev)
-    of mExpr, mTypeDesc:
+    of mTypeDesc: result = makeTypeDesc(c, semTypeNode(c, n[1], nil))
+    of mExpr:
       result = semTypeNode(c, n.sons[0], nil)
       if result != nil:
         result = copyType(result, getCurrOwner(), false)
diff --git a/compiler/semtypinst.nim b/compiler/semtypinst.nim
index 73b618f46..22edc6e32 100644
--- a/compiler/semtypinst.nim
+++ b/compiler/semtypinst.nim
@@ -29,6 +29,7 @@ proc checkConstructedType*(info: TLineInfo, typ: PType) =
     localError(info, errVarVarTypeNotAllowed)
   elif computeSize(t) == szIllegalRecursion:
     localError(info, errIllegalRecursionInTypeX, typeToString(t))
+  
   when false:
     if t.kind == tyObject and t.sons[0] != nil:
       if t.sons[0].kind != tyObject or tfFinal in t.sons[0].flags: 
@@ -219,7 +220,7 @@ proc handleGenericInvokation(cl: var TReplTypeVars, t: PType): PType =
   # is difficult to handle: 
   var body = t.sons[0]
   if body.kind != tyGenericBody: internalError(cl.info, "no generic body")
-  var header: PType = nil
+  var header: PType = t
   # search for some instantiation here:
   if cl.allowMetaTypes:
     result = PType(idTableGet(cl.localCache, t))
@@ -231,11 +232,13 @@ proc handleGenericInvokation(cl: var TReplTypeVars, t: PType): PType =
     if x.kind == tyGenericParam:
       x = lookupTypeVar(cl, x)
       if x != nil:
-        if header == nil: header = instCopyType(cl, t)
+        if header == t: header = instCopyType(cl, t)
         header.sons[i] = x
         propagateToOwner(header, x)
+    else:
+      propagateToOwner(header, x)
   
-  if header != nil:
+  if header != t:
     # search again after first pass:
     result = searchInstTypes(header)
     if result != nil: return
@@ -243,6 +246,7 @@ proc handleGenericInvokation(cl: var TReplTypeVars, t: PType): PType =
     header = instCopyType(cl, t)
   
   result = newType(tyGenericInst, t.sons[0].owner)
+  result.flags = header.flags
   # be careful not to propagate unnecessary flags here (don't use rawAddSon)
   result.sons = @[header.sons[0]]
   # ugh need another pass for deeply recursive generic types (e.g. PActor)
@@ -409,14 +413,22 @@ proc replaceTypeVarsTAux(cl: var TReplTypeVars, t: PType): PType =
       
       else: discard
 
+proc initTypeVars(p: PContext, pt: TIdTable, info: TLineInfo): TReplTypeVars =
+  initIdTable(result.symMap)
+  copyIdTable(result.typeMap, pt)
+  initIdTable(result.localCache)
+  result.info = info
+  result.c = p
+
+proc replaceTypesInBody*(p: PContext, pt: TIdTable, n: PNode): PNode =
+  var cl = initTypeVars(p, pt, n.info)
+  pushInfoContext(n.info)
+  result = replaceTypeVarsN(cl, n)
+  popInfoContext()
+  
 proc generateTypeInstance*(p: PContext, pt: TIdTable, info: TLineInfo,
                            t: PType): PType =
-  var cl: TReplTypeVars
-  initIdTable(cl.symMap)
-  copyIdTable(cl.typeMap, pt)
-  initIdTable(cl.localCache)
-  cl.info = info
-  cl.c = p
+  var cl = initTypeVars(p, pt, info)
   pushInfoContext(info)
   result = replaceTypeVarsT(cl, t)
   popInfoContext()
diff --git a/compiler/sigmatch.nim b/compiler/sigmatch.nim
index fce0bdf48..240145118 100644
--- a/compiler/sigmatch.nim
+++ b/compiler/sigmatch.nim
@@ -343,53 +343,57 @@ proc allowsNil(f: PType): TTypeRelation {.inline.} =
 proc inconsistentVarTypes(f, a: PType): bool {.inline.} =
   result = f.kind != a.kind and (f.kind == tyVar or a.kind == tyVar)
 
-proc procParamTypeRel(c: var TCandidate, f, a: PType,
-                      result: var TTypeRelation) =
-  var
-    m: TTypeRelation
-    f = f
-    
+proc procParamTypeRel(c: var TCandidate, f, a: PType): TTypeRelation =
+  var f = f
+
   if a.isMetaType:
     if f.isMetaType:
-      # we are matching a generic proc (as proc param)
+      # We are matching a generic proc (as proc param)
       # to another generic type appearing in the proc
-      # sigunature. there is a change that the target
+      # signature. There is a change that the target
       # type is already fully-determined, so we are 
       # going to try resolve it
       f = generateTypeInstance(c.c, c.bindings, c.call.info, f)
       if f == nil or f.isMetaType:
         # no luck resolving the type, so the inference fails
-        result = isNone
-        return
+        return isNone
     let reverseRel = typeRel(c, a, f)
     if reverseRel == isGeneric:
-      m = isInferred
+      result = isInferred
+      inc c.genericMatches
   else:
-    m = typeRel(c, f, a)
+    result = typeRel(c, f, a)
 
-  if m <= isSubtype or inconsistentVarTypes(f, a):
+  if result <= isSubtype or inconsistentVarTypes(f, a):
     result = isNone
-    return
-  else:
-    result = minRel(m, result)
-
+ 
+  if result == isEqual:
+    inc c.exactMatches
+    
 proc procTypeRel(c: var TCandidate, f, a: PType): TTypeRelation =
   case a.kind
   of tyProc:
     if sonsLen(f) != sonsLen(a): return
-    # Note: We have to do unification for the parameters before the
-    # return type!
     result = isEqual      # start with maximum; also correct for no
                           # params at all
-    for i in countup(1, sonsLen(f)-1):
-      procParamTypeRel(c, f.sons[i], a.sons[i], result)
+    
+    template checkParam(f, a) =
+      result = minRel(result, procParamTypeRel(c, f, a))
+      if result == isNone: return
+
+    # Note: We have to do unification for the parameters before the
+    # return type!
+    for i in 1 .. <f.sonsLen:
+      checkParam(f.sons[i], a.sons[i])
+    
     if f.sons[0] != nil:
       if a.sons[0] != nil:
-        procParamTypeRel(c, f.sons[0], a.sons[0], result)
+        checkParam(f.sons[0], a.sons[0])
       else:
         return isNone
     elif a.sons[0] != nil:
       return isNone
+
     if tfNoSideEffect in f.flags and tfNoSideEffect notin a.flags:
       return isNone
     elif tfThread in f.flags and a.flags * {tfThread, tfNoSideEffect} == {}:
@@ -896,20 +900,27 @@ proc typeRel(c: var TCandidate, f, aOrig: PType, doBind = true): TTypeRelation =
       result = isNone
 
   of tyTypeDesc:
-    if a.kind != tyTypeDesc: return isNone
-    
     var prev = PType(idTableGet(c.bindings, f))
     if prev == nil:
+      # proc foo(T: typedesc, x: T)
+      # when `f` is an unresolved typedesc, `a` could be any
+      # type, so we should not perform this check earlier
+      if a.kind != tyTypeDesc: return isNone
+    
       if f.base.kind == tyNone:
         result = isGeneric
       else:
         result = typeRel(c, f.base, a.base)
+      
       if result != isNone:
         put(c.bindings, f, a)
     else:
-      let toMatch = if tfUnresolved in f.flags: a
-                    else: a.base
-      result = typeRel(c, prev.base, toMatch)
+      if tfUnresolved in f.flags:
+        result = typeRel(c, prev.base, a)
+      elif a.kind == tyTypeDesc:
+        result = typeRel(c, prev.base, a.base)
+      else:
+        result = isNone
   
   of tyStmt:
     result = isGeneric
@@ -1035,10 +1046,11 @@ proc paramTypesMatchAux(m: var TCandidate, f, argType: PType,
     #result = copyTree(arg)
     result = implicitConv(nkHiddenStdConv, f, copyTree(arg), m, c)
   of isInferred, isInferredConvertible:
-    var prc = if arg.kind in nkLambdaKinds: arg[0].sym
-              else: arg.sym
-    let inferred = c.semGenerateInstance(c, prc, m.bindings, arg.info)
-    result = newSymNode(inferred, arg.info)
+    if arg.kind in {nkProcDef, nkIteratorDef} + nkLambdaKinds:
+      result = c.semInferredLambda(c, m.bindings, arg)
+    else:
+      let inferred = c.semGenerateInstance(c, arg.sym, m.bindings, arg.info)
+      result = newSymNode(inferred, arg.info)
     if r == isInferredConvertible:
       result = implicitConv(nkHiddenStdConv, f, result, m, c)
   of isGeneric:
@@ -1101,6 +1113,7 @@ proc paramTypesMatch*(m: var TCandidate, f, a: PType,
     # incorrect to simply use the first fitting match. However, to implement
     # this correctly is inefficient. We have to copy `m` here to be able to
     # roll back the side effects of the unification algorithm.
+
     let c = m.c
     var x, y, z: TCandidate
     initCandidate(c, x, m.callee)
@@ -1122,10 +1135,10 @@ proc paramTypesMatch*(m: var TCandidate, f, a: PType,
             x.state = csMatch
           of csMatch: 
             var cmp = cmpCandidates(x, z)
-            if cmp < 0: 
+            if cmp < 0:
               best = i
               x = z
-            elif cmp == 0: 
+            elif cmp == 0:
               y = z           # z is as good as x
     if x.state == csEmpty: 
       result = nil
diff --git a/compiler/types.nim b/compiler/types.nim
index 55a89920a..d7148f110 100644
--- a/compiler/types.nim
+++ b/compiler/types.nim
@@ -1042,7 +1042,8 @@ proc typeAllowedAux(marker: var TIntSet, typ: PType, kind: TSymKind,
   of tyEmpty:
     result = taField in flags
   of tyTypeClasses:
-    result = true
+    result = tfGenericTypeParam in t.flags or
+             taField notin flags
   of tyGenericBody, tyGenericParam, tyGenericInvokation,
      tyNone, tyForward, tyFromExpr, tyFieldAccessor:
     result = false
diff --git a/compiler/vm.nim b/compiler/vm.nim
index 81e712047..0929e072b 100644
--- a/compiler/vm.nim
+++ b/compiler/vm.nim
@@ -1025,7 +1025,7 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): PNode =
       regs[ra].sons[0].flags.incl nfIsRef
     of opcNCopyNimNode:
       decodeB(nkMetaNode)
-      setMeta(regs[ra], copyNode(regs[rb]))
+      setMeta(regs[ra], copyNode(regs[rb].skipMeta))
     of opcNCopyNimTree:
       decodeB(nkMetaNode)
       setMeta(regs[ra], copyTree(regs[rb]))
diff --git a/compiler/vmgen.nim b/compiler/vmgen.nim
index a6d044e24..206cca0d7 100644
--- a/compiler/vmgen.nim
+++ b/compiler/vmgen.nim
@@ -321,9 +321,18 @@ proc genAndOr(c: PCtx; n: PNode; opc: TOpcode; dest: var TDest) =
   c.gen(n.sons[2], dest)
   c.patch(L1)
 
+proc nilLiteral(n: PNode): PNode =
+  if n.kind == nkNilLit and n.typ.sym != nil and
+       n.typ.sym.magic == mPNimrodNode:
+    let nilo = newNodeIT(nkNilLit, n.info, n.typ)
+    result = newNodeIT(nkMetaNode, n.info, n.typ)
+    result.add nilo
+  else:
+    result = n
+
 proc rawGenLiteral(c: PCtx; n: PNode): int =
   result = c.constants.len
-  c.constants.add n
+  c.constants.add n.nilLiteral
   internalAssert result < 0x7fff
 
 proc sameConstant*(a, b: PNode): bool =
@@ -907,17 +916,20 @@ proc requiresCopy(n: PNode): bool =
 proc unneededIndirection(n: PNode): bool =
   n.typ.skipTypes(abstractInst-{tyTypeDesc}).kind == tyRef
 
-proc skipDeref(n: PNode): PNode =
-  if n.kind in {nkDerefExpr, nkHiddenDeref} and unneededIndirection(n.sons[0]):
-    result = n.sons[0]
-  else:
-    result = n
-
 proc genAddrDeref(c: PCtx; n: PNode; dest: var TDest; opc: TOpcode;
                   flags: TGenFlags) = 
   # a nop for certain types
   let flags = if opc == opcAddr: flags+{gfAddrOf} else: flags
-  if unneededIndirection(n.sons[0]):
+  # consider:
+  # proc foo(f: var ref int) =
+  #   f = new(int)
+  # proc blah() =
+  #   var x: ref int
+  #   foo x
+  #
+  # The type of 'f' is 'var ref int' and of 'x' is 'ref int'. Hence for
+  # nkAddr we must not use 'unneededIndirection', but for deref we use it.
+  if opc != opcAddr and unneededIndirection(n.sons[0]):
     gen(c, n.sons[0], dest, flags)
   else:
     let tmp = c.genx(n.sons[0], flags)
@@ -1109,7 +1121,12 @@ proc getNullValue(typ: PType, info: TLineInfo): PNode =
     result = newNodeIT(nkFloatLit, info, t)
   of tyVar, tyPointer, tyPtr, tyCString, tySequence, tyString, tyExpr,
      tyStmt, tyTypeDesc, tyStatic, tyRef:
-    result = newNodeIT(nkNilLit, info, t)
+    if t.sym != nil and t.sym.magic == mPNimrodNode:
+      let nilo = newNodeIT(nkNilLit, info, t)
+      result = newNodeIT(nkMetaNode, info, t)
+      result.add nilo
+    else:
+      result = newNodeIT(nkNilLit, info, t)
   of tyProc:
     if t.callConv != ccClosure:
       result = newNodeIT(nkNilLit, info, t)