diff --git a/js/js2/icodegenerator.cpp b/js/js2/icodegenerator.cpp
index 28a04cfa2285..dc9352645380 100644
--- a/js/js2/icodegenerator.cpp
+++ b/js/js2/icodegenerator.cpp
@@ -75,16 +75,14 @@ Formatter& operator<<(Formatter &f, ICodeModule &i)
 
 ICodeGenerator::ICodeGenerator(Context *cx, JSClass *aClass, ICodeGeneratorFlags flags)
     :   mTopRegister(0), 
-        mParameterCount(0),
         mExceptionRegister(TypedRegister(NotARegister, &None_Type)),
         variableList(new VariableList()),
+        parameterList(new ParameterList()),
         mContext(cx),
         mInstructionMap(new InstructionMap()),
         mClass(aClass),
         mFlags(flags),
         pLabels(NULL),
-        mHasRestParameter(false),
-        mHasNamedRestParameter(false),
         mInitName(cx->getWorld().identifiers["__init__"])
 { 
     iCode = new InstructionStream();
@@ -106,7 +104,7 @@ JSType *ICodeGenerator::findType(const StringAtom& typeName)
     -Theoretically, mPermanentRegister[n] can be become false when a scope ends and
      the registers allocated to contained variables are then available for re-use.
     -Mostly the need is to handle overlapping allocation of temps & permanents as the
-     variables declarations are encountered. This wouldn't be necessary if a function
+     variables' declarations are encountered. This wouldn't be necessary if a function
      presented a list of all variables, or a pre-pass executed to discover same.
 */
 TypedRegister ICodeGenerator::allocateRegister(const StringAtom& name, JSType *type) 
@@ -122,27 +120,11 @@ TypedRegister ICodeGenerator::allocateRegister(const StringAtom& name, JSType *t
     mPermanentRegister[r] = true;
 
     TypedRegister result(r, type); 
-    variableList->add(name, result);
     mTopRegister = ++r;
     return result;
 }
 
 
-TypedRegister ICodeGenerator::allocateVariable(const StringAtom& name, const StringAtom& typeName) 
-{ 
-    return allocateRegister(name, findType(typeName)); 
-}
-
-TypedRegister ICodeGenerator::allocateVariable(const StringAtom& name) 
-{ 
-    return allocateRegister(name, &Any_Type); 
-}
-
-TypedRegister ICodeGenerator::allocateVariable(const StringAtom& name, JSType *type) 
-{ 
-    return allocateRegister(name, type); 
-}
-
 ICodeModule *ICodeGenerator::complete(JSType *resultType)
 {
 #ifdef DEBUG
@@ -188,16 +170,13 @@ ICodeModule *ICodeGenerator::complete(JSType *resultType)
     */
     ICodeModule* module = new ICodeModule(iCode, 
                                             variableList, 
+                                            parameterList,
                                             mPermanentRegister.size(), 
-                                            mParameterCount, 
                                             mInstructionMap, 
-                                            mHasRestParameter, 
-                                            mHasNamedRestParameter,
                                             resultType);
     if (pLabels) {
         uint32 i;
         uint32 parameterInits = pLabels->size() - 1;        // there's an extra label at the end for the actual entryPoint
-        module->mNonOptionalParameterCount -= parameterInits;
         module->mParameterInit = new uint32[parameterInits];
         for (i = 0; i < parameterInits; i++) {
             module->mParameterInit[i] = (*pLabels)[i]->mOffset;
@@ -742,6 +721,8 @@ ICodeGenerator::LValueKind ICodeGenerator::resolveIdentifier(const StringAtom &n
 {
     if (!isWithinWith()) {
         v = variableList->findVariable(name);
+        if (v.first == NotARegister)
+            v = parameterList->findVariable(name);
         if (v.first != NotARegister)
             return Var;
         else {
@@ -1218,12 +1199,11 @@ TypedRegister ICodeGenerator::genExpr(ExprNode *p,
                     if (p->field && (p->field->getKind() == ExprNode::string))
                         args->push_back(Argument(genExpr(p->value), &mContext->getWorld().identifiers[(static_cast<StringExprNode *>(p->field))->str]));
                     else {
-/*  do this for new argument style to provide default 'positional' name
                         s << count;
                         args->push_back(Argument(genExpr(p->value), &mContext->getWorld().identifiers[s] ));
                         s.clear();
-*/
-                        args->push_back(Argument(genExpr(p->value), NULL ));
+
+//                        args->push_back(Argument(genExpr(p->value), NULL ));
                     }
                 count++;
                 p = p->next;
@@ -1561,15 +1541,16 @@ TypedRegister ICodeGenerator::genExpr(ExprNode *p,
         }
         break;
 
-    case ExprNode::functionLiteral:
+    case ExprNode::functionLiteral:     // XXX FIXME!! This needs to handled by calling genFunction !!!
+                                        // - the parameter handling is all wrong
         {
             FunctionExprNode *f = static_cast<FunctionExprNode *>(p);
             ICodeGenerator icg(mContext);
-            icg.allocateParameter(mContext->getWorld().identifiers["this"]);   // always parameter #0
+            icg.allocateParameter(mContext->getWorld().identifiers["this"], false);   // always parameter #0
             VariableBinding *v = f->function.parameters;
             while (v) {
                 if (v->name && (v->name->getKind() == ExprNode::identifier))
-                    icg.allocateParameter((static_cast<IdentifierExprNode *>(v->name))->name);
+                    icg.allocateParameter((static_cast<IdentifierExprNode *>(v->name))->name, false, &Any_Type);
                 v = v->next;
             }
             icg.genStmt(f->function.body);
@@ -1649,21 +1630,54 @@ ICodeModule *ICodeGenerator::genFunction(FunctionStmtNode *f, bool isConstructor
     ICodeGeneratorFlags flags = (isStatic) ? kIsStaticMethod : kNoFlags;
     
     ICodeGenerator icg(mContext, mClass, flags);
-    icg.allocateParameter(mContext->getWorld().identifiers["this"], (mClass) ? mClass : &Any_Type);   // always parameter #0
+    icg.allocateParameter(mContext->getWorld().identifiers["this"], false, (mClass) ? mClass : &Any_Type);   // always parameter #0
     VariableBinding *v = f->function.parameters;
+    bool unnamed = true;
+    uint32 positionalCount = 0;
+    StringFormatter s;
     while (v) {
-        if (v->name && (v->name->getKind() == ExprNode::identifier)) {
-            JSType *pType;
-            if ((v == f->function.restParameter) && (v->type == NULL))
-                pType = &Array_Type;
-            else
-                pType = extractType(v->type);
-            icg.allocateParameter((static_cast<IdentifierExprNode *>(v->name))->name, pType);
+        if (unnamed && (v == f->function.namedParameters)) { // Track when we hit the first named parameter.
+            icg.parameterList->setPositionalCount(positionalCount);
+            unnamed = false;
+        }
+        positionalCount++;
+
+        // The rest parameter is ignored in this processing - we push it to the end of the list.
+        // But we need to track whether it comes before or after the |
+        if (v == f->function.restParameter) {
+            icg.parameterList->setRestParameter( (unnamed) ? ParameterList::HasRestParameterBeforeBar : ParameterList::HasRestParameterAfterBar );
+        }
+        else {
+            if (v->name && (v->name->getKind() == ExprNode::identifier)) {
+                JSType *pType = extractType(v->type);
+                TypedRegister r = icg.allocateParameter((static_cast<IdentifierExprNode *>(v->name))->name, (v->initializer != NULL), pType);
+                IdentifierList *a = v->aliases;
+                while (a) {
+                    icg.parameterList->add(a->name, r, (v->initializer != NULL));
+                    a = a->next;
+                }
+                // every unnamed parameter is also named with it's positional name
+                if (unnamed) {
+                    s << r.first - 1;  // the first positional parameter is '0'
+                    icg.parameterList->add(mContext->getWorld().identifiers[s], r, (v->initializer != NULL));
+                    s.clear();
+                }
+            }
         }
-        else
-            NOT_REACHED("qualified or un-named parameters not handled; bugger off.");
         v = v->next;
     }
+
+    // now allocate the rest parameter
+    if (f->function.restParameter) {
+        v = f->function.restParameter;
+        JSType *pType = (v->type == NULL) ? &Array_Type : extractType(v->type);
+        if (v->name && (v->name->getKind() == ExprNode::identifier))
+            icg.allocateParameter((static_cast<IdentifierExprNode *>(v->name))->name, (v->initializer != NULL), pType);
+        else
+            icg.parameterList->setRestParameter(ParameterList::HasUnnamedRestParameter);
+    }
+
+    // generate the code for optional initializers
     v = f->function.optParameters;
     if (v) {
         while (v) {    // include the rest parameter, as it may have an initializer
@@ -1689,13 +1703,7 @@ ICodeModule *ICodeGenerator::genFunction(FunctionStmtNode *f, bool isConstructor
         }
         icg.addParameterLabel(icg.setLabel(icg.getLabel()));    // to provide the entry-point for the default case
     }
-    v = f->function.restParameter;
-    if (v) {
-        icg.mHasRestParameter = true;
-        if (v->name && (v->name->getKind() == ExprNode::identifier)) {
-            icg.mHasNamedRestParameter = true;
-        }
-    }
+
     if (isConstructor) {
         /*
            See if the first statement is an expression statement consisting
@@ -1851,7 +1859,7 @@ TypedRegister ICodeGenerator::genStmt(StmtNode *p, LabelSet *currentLabelSet)
                       // constructor code generator. Slot variable
                       // initializers get added to this function.
                     ccg = new ICodeGenerator(classContext, thisClass, kNoFlags);   
-                    ccg->allocateParameter(mContext->getWorld().identifiers["this"], thisClass);   // always parameter #0
+                    ccg->allocateParameter(mContext->getWorld().identifiers["this"], false, thisClass);   // always parameter #0
                 }
                 
                 ICodeGenerator scg(classContext, thisClass, kIsStaticMethod);   // static initializer code generator.
@@ -1939,7 +1947,7 @@ TypedRegister ICodeGenerator::genStmt(StmtNode *p, LabelSet *currentLabelSet)
                     TypedRegister thisValue = TypedRegister(0, thisClass);
                     ArgumentList *args = new ArgumentList();
                     ICodeGenerator icg(classContext, thisClass, kIsStaticMethod);
-                    icg.allocateParameter(mContext->getWorld().identifiers["this"], thisClass);   // always parameter #0
+                    icg.allocateParameter(mContext->getWorld().identifiers["this"], false, thisClass);   // always parameter #0
                     if (superclass)
                         icg.call(icg.getStatic(superclass, superclass->getName()), thisValue, args);
                     if (thisClass->hasStatic(mInitName))
@@ -2325,7 +2333,6 @@ TypedRegister ICodeGenerator::genStmt(StmtNode *p, LabelSet *currentLabelSet)
                     // Bind the incoming exception ...
                     if (mExceptionRegister.first == NotABanana)
                         mExceptionRegister = allocateRegister(mContext->getWorld().identifiers["__exceptionObject__"], &Any_Type);
-                    variableList->setRegisterForVariable(c->name, mExceptionRegister);
 
                     genStmt(c->stmt);
                     if (finallyLabel)
@@ -2419,7 +2426,7 @@ void ICodeGenerator::readICode(const char *fileName)
             Context *classContext = new Context(mContext->getWorld(), thisScope);
             ICodeGenerator scg(classContext, thisClass, kIsStaticMethod);
             ICodeGenerator ccg(classContext, thisClass, kNoFlags);
-            ccg.allocateParameter(mContext->getWorld().identifiers["this"], thisClass);
+            ccg.allocateParameter(mContext->getWorld().identifiers["this"], false, thisClass);
             thisClass->defineStatic(mInitName, &Function_Type);
 
             mContext->getGlobalObject()->defineVariable(className, &Type_Type, JSValue(thisClass));
@@ -2433,8 +2440,8 @@ void ICodeGenerator::readICode(const char *fileName)
                     String methodName, resultTypeName;
                     element->getValue(widenCString("name"), methodName);
                     element->getValue(widenCString("type"), resultTypeName);
-                    VariableList *theVariableList = new VariableList();
-                    theVariableList->add(mContext->getWorld().identifiers["this"], TypedRegister(0, thisClass));
+                    ParameterList *theParameterList = new ParameterList();
+                    theParameterList->add(mContext->getWorld().identifiers["this"], TypedRegister(0, thisClass), false);
                     uint32 pCount = 1;
                     XMLNodeList &parameters = element->children();
                     for (XMLNodeList::const_iterator k = parameters.begin(); k != parameters.end(); k++) {
@@ -2445,7 +2452,7 @@ void ICodeGenerator::readICode(const char *fileName)
                             element->getValue(widenCString("name"), parameterName);
                             element->getValue(widenCString("type"), parameterTypeName);
                             JSType *parameterType = findType(mContext->getWorld().identifiers[parameterTypeName]);
-                            theVariableList->add(mContext->getWorld().identifiers[parameterName], TypedRegister(pCount++, parameterType));
+                            theParameterList->add(mContext->getWorld().identifiers[parameterName], TypedRegister(pCount++, parameterType), false);
                         }
                     }
                     
@@ -2461,12 +2468,10 @@ void ICodeGenerator::readICode(const char *fileName)
                         icp.ParseSourceFromString(str);
 
                         ICodeModule *icm = new ICodeModule(icp.mInstructions, 
-                                                            theVariableList,       /* VariableList *variables */
+                                                            NULL,                   /* VariableList *variables */
+                                                            theParameterList,       /* ParameterList *parameters */
                                                             icp.mMaxRegister, 
-                                                            pCount,                 /* uint32 maxParameter, */
                                                             NULL,                   /* InstructionMap *instructionMap */
-                                                            false,                  /* bool hasRestParameter, */
-                                                            false,                  /* bool hasNamedRestParameter */
                                                             resultType);
                         thisClass->defineMethod(methodName, new JSFunction(icm));
                     }
@@ -2493,7 +2498,7 @@ void ICodeGenerator::readICode(const char *fileName)
                 TypedRegister thisValue = TypedRegister(0, thisClass);
                 ArgumentList *args = new ArgumentList(0);
                 ICodeGenerator icg(mContext, thisClass, kIsStaticMethod);
-                icg.allocateParameter(mContext->getWorld().identifiers["this"], thisClass);   // always parameter #0
+                icg.allocateParameter(mContext->getWorld().identifiers["this"], false, thisClass);   // always parameter #0
                 if (superclass)
                     icg.call(icg.getStatic(superclass, superclass->getName()), thisValue, args);
                 if (thisClass->hasStatic(mInitName))
diff --git a/js/js2/icodegenerator.h b/js/js2/icodegenerator.h
index 800161760c35..69abe8984e36 100644
--- a/js/js2/icodegenerator.h
+++ b/js/js2/icodegenerator.h
@@ -51,59 +51,92 @@ namespace ICG {
     using namespace JSClasses;
     
 
-    struct VariableList {
+    struct VariableList {       // Maps from variable (parameter) name to a TypedRegister.
+                                // But because we also want to map from a register number to
+                                // it's type, we keep the TypedRegsters in a separate array and
+                                // just store the index in the name map.
 
         typedef std::map<String, uint32, std::less<String> > VariableMap;
+        typedef VariableMap::value_type MapValue;
+
         VariableMap variableMap;
-
-        std::vector<TypedRegister> registerMap;
+        std::vector<TypedRegister> registerList;
     
-        void setRegisterForVariable(const StringAtom& name, TypedRegister r) 
-        {
-            VariableMap::iterator i = variableMap.find(name);
-            ASSERT(i != variableMap.end());
-            registerMap[(*i).second] = r;
-        }
-
         TypedRegister findVariable(const StringAtom& name)
         {
             VariableMap::iterator i = variableMap.find(name);
-            return (i == variableMap.end()) ? TypedRegister(NotARegister, &None_Type) : registerMap[(*i).second];
+            return (i == variableMap.end()) 
+                        ? TypedRegister(NotARegister, &None_Type) 
+                        : registerList[i->second];
         }
 
         void add(const StringAtom& name, TypedRegister r)
         {
-            variableMap[name] = r.first;
-            registerMap.resize(r.first + 1);
-            registerMap[r.first] = r;
+            variableMap.insert(MapValue(name, r.first));
+            registerList.resize(r.first + 1);
+            registerList[r.first] = r;
         }
 
         TypedRegister getRegister(uint32 i)
         {
-            ASSERT(i < registerMap.size());
-            return registerMap[i];
+            ASSERT(i < registerList.size());
+            return registerList[i];
         }
 
+
     };
 
+    struct ParameterList : public VariableList {
+        typedef enum { 
+            NoRestParameter, 
+            HasRestParameterBeforeBar, 
+            HasRestParameterAfterBar, 
+            HasUnnamedRestParameter 
+        } RestParameterStatus;
+
+        
+        
+        std::vector<bool> mOptionalParameters;      // whether or not a parameter has an optional value
+                                                    // ordered by lexical ordering === register number.
+        RestParameterStatus mRestParameter;
+        uint32 mPositionalCount;                    // number of positional parameters
+
+
+
+
+        ParameterList() : mRestParameter(NoRestParameter), mPositionalCount(0) { }
+
+        void add(const StringAtom& name, TypedRegister r, bool isOptional)
+        {
+            VariableList::add(name, r);
+            mOptionalParameters.resize(r.first + 1);
+            mOptionalParameters[r.first] = isOptional;
+        }
+
+        uint32 size()   { return registerList.size(); }     // the variableMap may be larger since it contains aliases
+
+        bool isOptional(uint32 i)   { ASSERT(i < mOptionalParameters.size()); return mOptionalParameters[i]; }
+
+        void setRestParameter(RestParameterStatus rs)   { mRestParameter = rs; }
+        void setPositionalCount(uint32 x)               { mPositionalCount = x; }
+
+    };
+
+
     typedef std::map<uint32, uint32, std::less<uint32> > InstructionMap;
-   
 
     class ICodeModule {
     public:
         ICodeModule(InstructionStream *iCode, VariableList *variables,
-                    uint32 maxRegister, uint32 maxParameter,
+                    ParameterList *parameters,
+                    uint32 maxRegister,
                     InstructionMap *instructionMap, 
-                    bool hasRestParameter, bool hasNamedRestParameter,
                     JSType *resultType) :
-            its_iCode(iCode), itsVariables(variables),
-            mParameterCount(maxParameter), itsMaxRegister(maxRegister),
+            its_iCode(iCode), itsVariables(variables), itsParameters(parameters),
+            itsMaxRegister(maxRegister),
             mID(++sMaxID), mInstructionMap(instructionMap), 
             mParameterInit(NULL), 
-            mNonOptionalParameterCount(maxParameter),
             mEntryPoint(0),
-            mHasRestParameter(hasRestParameter),
-            mHasNamedRestParameter(hasNamedRestParameter),
             mResultType(resultType)
         {
         }
@@ -122,16 +155,13 @@ namespace ICG {
         
         InstructionStream *its_iCode;
         VariableList *itsVariables;
-        uint32 mParameterCount;
+        ParameterList *itsParameters;
         uint32 itsMaxRegister;
         uint32 mID;
         InstructionMap *mInstructionMap;
         String mFileName;
         uint32 *mParameterInit;
-        uint32 mNonOptionalParameterCount;
         uint32 mEntryPoint;
-        bool mHasRestParameter;
-        bool mHasNamedRestParameter;
         JSType *mResultType;
 
         static uint32 sMaxID;
@@ -172,10 +202,10 @@ namespace ICG {
         LabelList labels;
         
         Register mTopRegister;              // highest (currently) allocated register
-        uint32   mParameterCount;           // number of parameters declared for the function
-                                            // these must come before any variables declared.
         TypedRegister mExceptionRegister;   // reserved to carry the exception object.
         VariableList *variableList;         // name|register pair for each variable
+        ParameterList *parameterList;       // name|register pair for each parameter
+                                            // (with #0 reserved for 'this' regardless of scope)
         
         Context *mContext;                  // the world and global object
         LabelStack mLabelStack;             // stack of LabelEntry objects, one per nested looping construct
@@ -185,8 +215,6 @@ namespace ICG {
         JSClass *mClass;                    // enclosing class when generating code for methods
         ICodeGeneratorFlags mFlags;         // assorted flags
         LabelList *pLabels;                 // label for each parameter initialization entry point
-        bool mHasRestParameter;             // true if this function has a ... parameter
-        bool mHasNamedRestParameter;        // true if this function has a named ... parameter
 
         const StringAtom &mInitName;
 
@@ -204,7 +232,7 @@ namespace ICG {
             return mTopRegister++;
         }
 
-        void resetTopRegister() { mTopRegister = mParameterCount; }
+        void resetTopRegister() { mTopRegister = 0; }
         void resetStatement()   { resetTopRegister(); }
 
         TypedRegister allocateRegister(const StringAtom& name, JSType *type);
@@ -280,15 +308,40 @@ namespace ICG {
         void throwStmt(TypedRegister r)         { iCode->push_back(new Throw(r)); }
         void debuggerStmt()                     { iCode->push_back(new Debugger()); }
 
-        TypedRegister allocateVariable(const StringAtom& name);
-        TypedRegister allocateVariable(const StringAtom& name, const StringAtom& typeName);
-        TypedRegister allocateVariable(const StringAtom& name, JSType *type) ;
+        TypedRegister allocateVariable(const StringAtom& name)
+        { 
+            return allocateVariable(name, &Any_Type);
+        }
         
-        TypedRegister allocateParameter(const StringAtom& name)         { mParameterCount++; return allocateRegister(name, &Any_Type); }
-        TypedRegister allocateParameter(const StringAtom& name, const StringAtom& typeName) 
-                                                                        { mParameterCount++; return allocateRegister(name, findType(typeName)); }
-        TypedRegister allocateParameter(const StringAtom& name, JSType *type) 
-                                                                        { mParameterCount++; return allocateRegister(name, type); }
+        TypedRegister allocateVariable(const StringAtom& name, const StringAtom& typeName)
+        {
+            return allocateVariable(name, findType(typeName));
+        }
+        
+        TypedRegister allocateVariable(const StringAtom& name, JSType *type)
+        { 
+            TypedRegister r = allocateRegister(name, type);
+            variableList->add(name, r);
+            return r;
+        }
+        
+        TypedRegister allocateParameter(const StringAtom& name, bool isOptional)
+        { 
+            return allocateParameter(name, isOptional, &Any_Type);
+        }
+        
+        TypedRegister allocateParameter(const StringAtom& name, bool isOptional, const StringAtom& typeName)
+        {
+            return allocateParameter(name, isOptional, findType(typeName));
+        }
+        
+        TypedRegister allocateParameter(const StringAtom& name, bool isOptional, JSType *type)
+        { 
+            TypedRegister r = allocateRegister(name, type);
+            parameterList->add(name, r, isOptional);
+            return r;
+        }
+
         
         Formatter& print(Formatter& f);
         
diff --git a/js/js2/interpreter.cpp b/js/js2/interpreter.cpp
index a42f484feb6e..20e10310fcb6 100644
--- a/js/js2/interpreter.cpp
+++ b/js/js2/interpreter.cpp
@@ -160,11 +160,11 @@ ICodeModule* Context::compileFunction(const String &source)
     ICodeGenerator icg(this);
     ASSERT(e->getKind() == ExprNode::functionLiteral);
     FunctionExprNode* f = static_cast<FunctionExprNode*>(e);
-    icg.allocateParameter(getWorld().identifiers["this"]);   // always parameter #0
+    icg.allocateParameter(getWorld().identifiers["this"], false);   // always parameter #0
     VariableBinding* v = f->function.parameters;
     while (v) {
         if (v->name && (v->name->getKind() == ExprNode::identifier))
-            icg.allocateParameter((static_cast<IdentifierExprNode*>(v->name))->name);
+            icg.allocateParameter((static_cast<IdentifierExprNode*>(v->name))->name, false);
         v = v->next;
     }
     icg.genStmt(f->function.body);
@@ -719,97 +719,85 @@ JSValue Context::interpret(ICodeModule* iCode, const JSValues& args)
                         ICodeModule *icm = target->getICode();
                         ArgumentList *args = op4(call);
 
-                        // mParameterCount includes 'this' and also 1 for a named rest parameter
+                        // the parameter count includes 'this' and any named rest parameter
                         //
-                        uint32 pCount = icm->mParameterCount - 1;
+                        uint32 pCount = icm->itsParameters->size() - 1;   // we won't be passing 'this' via the arg list array
+                        // callArgs will be the actual args passed to the target, put into correct register order.
+                        // It has room for the rest parameter.
                         ArgumentList *callArgs = new ArgumentList(pCount, Argument(TypedRegister(NotARegister, &Null_Type), NULL));
-                        if (icm->mHasNamedRestParameter) pCount--;
 
-/*
-
-    For new style, there must be enough un-named parameters to satisfy #unnamed-positional, but no
-    more than #total positional (unless there's a rest parameter). Extras go to the optional parameters first, then to rest.
-
-    Named parameters 
-
-*/
-
-
-                        // walk along the given arguments, handling each.
-                        // might be good to optimize the case of calls without named arguments and/or rest parameters
-                        JSArray *restArg = NULL;
-                        uint32 restIndex = 0;
+                        // don't want to count the rest parameter while processing the others 
+                        if (icm->itsParameters->mRestParameter != ParameterList::NoRestParameter) pCount--;
+                        
+                        
                         uint32 i;
+                        JSArray *restArg = NULL;
+                        
+                        // first match all named arguments with their intended target locations
                         for (i = 0; i < args->size(); i++) {
-                            if ((*args)[i].second) {       // a named argument
-                                TypedRegister r = icm->itsVariables->findVariable(*((*args)[i].second));
-                                bool isParameter = false;
-                                if (r.first != NotABanana) {   // we found the name in the target's list of variables
-                                    if (r.first < icm->mParameterCount) { // make sure we didn't match a local var                                            
-                                        ASSERT(r.first <= callArgs->size());
-                                        // the named argument is arriving in slot i, but needs to be r instead
-                                        // r.first is the intended target register, we subtract 1 since the callArgs array doesn't include 'this'
-                                        // here's where we could detect over-writing a positional arg with a named one if that is illegal
-                                        // if (callArgs[r.first - 1].first.first != NotARegister)...
-                                        (*registers)[(*args)[i].first.first] = (*registers)[(*args)[i].first.first].convert(r.second);
-                                        (*callArgs)[r.first - 1] = Argument((*args)[i].first, NULL);   // no need to copy the name through?
-                                        isParameter = true;
-                                    }
-                                }
-                                if (!isParameter) {     // wasn't a parameter, make it a property of the rest parameter (if there is one) 
-                                    if (icm->mHasRestParameter) {
-                                        if (icm->mHasNamedRestParameter) {
-                                            if (restArg == NULL) {
-                                                restArg = new JSArray();
-                                                restArg->setProperty(*(*args)[i].second, (*registers)[(*args)[i].first.first]);
-                                                (*registers)[(*args)[i].first.first] = restArg;
-                                                (*callArgs)[pCount] = Argument(TypedRegister((*args)[i].first.first, &Array_Type), NULL);
-                                            }
-                                            else
-                                                restArg->setProperty(*(*args)[i].second, (*registers)[(*args)[i].first.first]);
+                            
+                            const StringAtom *argName = (*args)[i].second;
 
+                            TypedRegister parameter = icm->itsParameters->findVariable(*argName);
+                            if (parameter.first == NotARegister) {  
+                                // arg name doesn't match any parameter name, it's a candidate
+                                // for the rest parameter (if there is one)
+                                if (icm->itsParameters->mRestParameter == ParameterList::NoRestParameter)
+                                    throw new JSException("Named argument doesn't match parameter name in call with no rest parameter");
+                                else {
+                                    if (icm->itsParameters->mRestParameter != ParameterList::HasUnnamedRestParameter) {
+                                        // if the name is a numeric literal >= 0, use it as an array index
+                                        // otherwise just set the named property.
+                                        const char16 *c = argName->c_str();
+                                        const char16 *end;
+                                        double d = stringToDouble(c, c + argName->length(), end);
+
+                                        if ((d != d) || (d < 0) || (d != (int)d)) { // a non-numeric or negative value                                             
+                                            if (icm->itsParameters->mRestParameter == ParameterList::HasRestParameterBeforeBar)
+                                                throw new JSException("Non-numeric or negative argument name for positional rest parameter");
                                         }
-                                        // else just throw it away 
+                                        else {  // shift the index value down by the number of positional parameters
+                                            StringFormatter s;
+                                            s << ((int)d - icm->itsParameters->mPositionalCount);
+                                            argName = &mWorld.identifiers[s];
+                                        }
+                                        
+                                        TypedRegister argument = (*args)[i].first;   // this is the argument whose name didn't match
+
+                                        if (restArg == NULL) {
+                                            // allocate the rest argument and then subvert the register being used for the
+                                            // argument under consideration to hold the newly created rest argument.
+                                            restArg = new JSArray();
+                                            restArg->setProperty(*argName, (*registers)[argument.first]);   // put it into the rest argument
+                                            (*registers)[argument.first] = restArg;
+                                            // The callArgs for the rest parameter position gets loaded from that slot 
+                                            (*callArgs)[pCount] = Argument(TypedRegister(argument.first, &Array_Type), NULL);
+                                        }
+                                        else
+                                            restArg->setProperty(*argName, (*registers)[argument.first]);
                                     }
-                                    else 
-                                        throw new JSException("Named argument doesn't match parameter name in call with no rest parameter");
-                                        // what about matching the named rest parameter ? aaarrggh!
+                                    // else just throw it away 
                                 }
                             }
                             else {
-                                if (i >= pCount) {  // more args than expected
-                                    if (icm->mHasRestParameter) {
-                                        if (icm->mHasNamedRestParameter) {
-                                            if (restArg == NULL) {
-                                                restArg = new JSArray();
-                                                (*restArg)[restIndex++] = (*registers)[(*args)[i].first.first];
-                                                (*registers)[(*args)[i].first.first] = restArg;
-                                                (*callArgs)[pCount] = Argument(TypedRegister((*args)[i].first.first, &Array_Type), NULL);
-                                            }
-                                            else
-                                                (*restArg)[restIndex++] = (*registers)[(*args)[i].first.first];
-                                        }
-                                        // else just throw it away 
-                                    }
-                                    else
-                                        throw new JSException("Too many arguments in call");
-                                }
-                                else {
-                                    TypedRegister r = icm->itsVariables->getRegister(i + 1);    // the variable list includes 'this'
-                                    (*registers)[(*args)[i].first.first] = (*registers)[(*args)[i].first.first].convert(r.second);
-                                    (*callArgs)[i] = (*args)[i];  // it's a positional, just slap it in place
-                                }
+                                uint32 targetIndex = parameter.first - 1;           // this is the register number we're targetting
+                                TypedRegister targetParameter = (*callArgs)[targetIndex].first;
+                                if (targetParameter.first != NotARegister)          // uh oh, some other argument wants this parameter
+                                    throw new JSException("Two (or more) arguments have the same name");
+                                (*callArgs)[targetIndex] = (*args)[i];
                             }
                         }
-                        uint32 contiguousArgs = 0;
-                        for (i = 0; i < args->size(); i++) {
-                            Argument &arg = (*args)[i];
-                            if (arg.first.first == NotARegister) break;
-                            contiguousArgs++;
+
+
+                        // make sure that all non-optional parameters have values
+                        for (i = 0; i < pCount; i++) {
+                            TypedRegister parameter = (*callArgs)[i].first;
+                            if (parameter.first == NotARegister) {  // doesn't have an assigned argument
+                                if (!icm->itsParameters->isOptional(i + 1))     // and parameter (allowing for 'this') doesn't have an optional value
+                                    throw new JSException("No argument supplied for non-optional parameter");
+                            }
                         }
-                        if ((contiguousArgs + 1) < icm->mNonOptionalParameterCount) // there's always a 'this' in R0 (even though it might be null)
-                            throw new JSException("Too few arguments in call");
-                        
+
                         mLinkage = new Linkage(mLinkage, ++mPC, mActivation, mGlobal, op1(call));
                         mActivation = new Activation(icm, mActivation, (*registers)[op3(call).first], callArgs);
                         registers = &mActivation->mRegisters;
diff --git a/js/js2/xmlparser.h b/js/js2/xmlparser.h
index 6232a19d0236..9aafebfdd2ef 100644
--- a/js/js2/xmlparser.h
+++ b/js/js2/xmlparser.h
@@ -63,7 +63,7 @@ public:
     XMLTag(String name) : mName(name), mFlag(Tag)  { }
     
     void addAttribute(const String &name, const String &value)    { mAttributeList.insert(AttributeValue(name, value) ); }
-    bool getValue(const String &name, String &value);
+    bool getValue(const String &name, String &value);   // returns the value of the most newly inserted attribute 'name'.
     bool hasAttribute(const String &name)                 { return (mAttributeList.find(name) != mAttributeList.end()); }
 
     String &name()      { return mName; }
diff --git a/js2/src/icodegenerator.cpp b/js2/src/icodegenerator.cpp
index 28a04cfa2285..dc9352645380 100644
--- a/js2/src/icodegenerator.cpp
+++ b/js2/src/icodegenerator.cpp
@@ -75,16 +75,14 @@ Formatter& operator<<(Formatter &f, ICodeModule &i)
 
 ICodeGenerator::ICodeGenerator(Context *cx, JSClass *aClass, ICodeGeneratorFlags flags)
     :   mTopRegister(0), 
-        mParameterCount(0),
         mExceptionRegister(TypedRegister(NotARegister, &None_Type)),
         variableList(new VariableList()),
+        parameterList(new ParameterList()),
         mContext(cx),
         mInstructionMap(new InstructionMap()),
         mClass(aClass),
         mFlags(flags),
         pLabels(NULL),
-        mHasRestParameter(false),
-        mHasNamedRestParameter(false),
         mInitName(cx->getWorld().identifiers["__init__"])
 { 
     iCode = new InstructionStream();
@@ -106,7 +104,7 @@ JSType *ICodeGenerator::findType(const StringAtom& typeName)
     -Theoretically, mPermanentRegister[n] can be become false when a scope ends and
      the registers allocated to contained variables are then available for re-use.
     -Mostly the need is to handle overlapping allocation of temps & permanents as the
-     variables declarations are encountered. This wouldn't be necessary if a function
+     variables' declarations are encountered. This wouldn't be necessary if a function
      presented a list of all variables, or a pre-pass executed to discover same.
 */
 TypedRegister ICodeGenerator::allocateRegister(const StringAtom& name, JSType *type) 
@@ -122,27 +120,11 @@ TypedRegister ICodeGenerator::allocateRegister(const StringAtom& name, JSType *t
     mPermanentRegister[r] = true;
 
     TypedRegister result(r, type); 
-    variableList->add(name, result);
     mTopRegister = ++r;
     return result;
 }
 
 
-TypedRegister ICodeGenerator::allocateVariable(const StringAtom& name, const StringAtom& typeName) 
-{ 
-    return allocateRegister(name, findType(typeName)); 
-}
-
-TypedRegister ICodeGenerator::allocateVariable(const StringAtom& name) 
-{ 
-    return allocateRegister(name, &Any_Type); 
-}
-
-TypedRegister ICodeGenerator::allocateVariable(const StringAtom& name, JSType *type) 
-{ 
-    return allocateRegister(name, type); 
-}
-
 ICodeModule *ICodeGenerator::complete(JSType *resultType)
 {
 #ifdef DEBUG
@@ -188,16 +170,13 @@ ICodeModule *ICodeGenerator::complete(JSType *resultType)
     */
     ICodeModule* module = new ICodeModule(iCode, 
                                             variableList, 
+                                            parameterList,
                                             mPermanentRegister.size(), 
-                                            mParameterCount, 
                                             mInstructionMap, 
-                                            mHasRestParameter, 
-                                            mHasNamedRestParameter,
                                             resultType);
     if (pLabels) {
         uint32 i;
         uint32 parameterInits = pLabels->size() - 1;        // there's an extra label at the end for the actual entryPoint
-        module->mNonOptionalParameterCount -= parameterInits;
         module->mParameterInit = new uint32[parameterInits];
         for (i = 0; i < parameterInits; i++) {
             module->mParameterInit[i] = (*pLabels)[i]->mOffset;
@@ -742,6 +721,8 @@ ICodeGenerator::LValueKind ICodeGenerator::resolveIdentifier(const StringAtom &n
 {
     if (!isWithinWith()) {
         v = variableList->findVariable(name);
+        if (v.first == NotARegister)
+            v = parameterList->findVariable(name);
         if (v.first != NotARegister)
             return Var;
         else {
@@ -1218,12 +1199,11 @@ TypedRegister ICodeGenerator::genExpr(ExprNode *p,
                     if (p->field && (p->field->getKind() == ExprNode::string))
                         args->push_back(Argument(genExpr(p->value), &mContext->getWorld().identifiers[(static_cast<StringExprNode *>(p->field))->str]));
                     else {
-/*  do this for new argument style to provide default 'positional' name
                         s << count;
                         args->push_back(Argument(genExpr(p->value), &mContext->getWorld().identifiers[s] ));
                         s.clear();
-*/
-                        args->push_back(Argument(genExpr(p->value), NULL ));
+
+//                        args->push_back(Argument(genExpr(p->value), NULL ));
                     }
                 count++;
                 p = p->next;
@@ -1561,15 +1541,16 @@ TypedRegister ICodeGenerator::genExpr(ExprNode *p,
         }
         break;
 
-    case ExprNode::functionLiteral:
+    case ExprNode::functionLiteral:     // XXX FIXME!! This needs to handled by calling genFunction !!!
+                                        // - the parameter handling is all wrong
         {
             FunctionExprNode *f = static_cast<FunctionExprNode *>(p);
             ICodeGenerator icg(mContext);
-            icg.allocateParameter(mContext->getWorld().identifiers["this"]);   // always parameter #0
+            icg.allocateParameter(mContext->getWorld().identifiers["this"], false);   // always parameter #0
             VariableBinding *v = f->function.parameters;
             while (v) {
                 if (v->name && (v->name->getKind() == ExprNode::identifier))
-                    icg.allocateParameter((static_cast<IdentifierExprNode *>(v->name))->name);
+                    icg.allocateParameter((static_cast<IdentifierExprNode *>(v->name))->name, false, &Any_Type);
                 v = v->next;
             }
             icg.genStmt(f->function.body);
@@ -1649,21 +1630,54 @@ ICodeModule *ICodeGenerator::genFunction(FunctionStmtNode *f, bool isConstructor
     ICodeGeneratorFlags flags = (isStatic) ? kIsStaticMethod : kNoFlags;
     
     ICodeGenerator icg(mContext, mClass, flags);
-    icg.allocateParameter(mContext->getWorld().identifiers["this"], (mClass) ? mClass : &Any_Type);   // always parameter #0
+    icg.allocateParameter(mContext->getWorld().identifiers["this"], false, (mClass) ? mClass : &Any_Type);   // always parameter #0
     VariableBinding *v = f->function.parameters;
+    bool unnamed = true;
+    uint32 positionalCount = 0;
+    StringFormatter s;
     while (v) {
-        if (v->name && (v->name->getKind() == ExprNode::identifier)) {
-            JSType *pType;
-            if ((v == f->function.restParameter) && (v->type == NULL))
-                pType = &Array_Type;
-            else
-                pType = extractType(v->type);
-            icg.allocateParameter((static_cast<IdentifierExprNode *>(v->name))->name, pType);
+        if (unnamed && (v == f->function.namedParameters)) { // Track when we hit the first named parameter.
+            icg.parameterList->setPositionalCount(positionalCount);
+            unnamed = false;
+        }
+        positionalCount++;
+
+        // The rest parameter is ignored in this processing - we push it to the end of the list.
+        // But we need to track whether it comes before or after the |
+        if (v == f->function.restParameter) {
+            icg.parameterList->setRestParameter( (unnamed) ? ParameterList::HasRestParameterBeforeBar : ParameterList::HasRestParameterAfterBar );
+        }
+        else {
+            if (v->name && (v->name->getKind() == ExprNode::identifier)) {
+                JSType *pType = extractType(v->type);
+                TypedRegister r = icg.allocateParameter((static_cast<IdentifierExprNode *>(v->name))->name, (v->initializer != NULL), pType);
+                IdentifierList *a = v->aliases;
+                while (a) {
+                    icg.parameterList->add(a->name, r, (v->initializer != NULL));
+                    a = a->next;
+                }
+                // every unnamed parameter is also named with it's positional name
+                if (unnamed) {
+                    s << r.first - 1;  // the first positional parameter is '0'
+                    icg.parameterList->add(mContext->getWorld().identifiers[s], r, (v->initializer != NULL));
+                    s.clear();
+                }
+            }
         }
-        else
-            NOT_REACHED("qualified or un-named parameters not handled; bugger off.");
         v = v->next;
     }
+
+    // now allocate the rest parameter
+    if (f->function.restParameter) {
+        v = f->function.restParameter;
+        JSType *pType = (v->type == NULL) ? &Array_Type : extractType(v->type);
+        if (v->name && (v->name->getKind() == ExprNode::identifier))
+            icg.allocateParameter((static_cast<IdentifierExprNode *>(v->name))->name, (v->initializer != NULL), pType);
+        else
+            icg.parameterList->setRestParameter(ParameterList::HasUnnamedRestParameter);
+    }
+
+    // generate the code for optional initializers
     v = f->function.optParameters;
     if (v) {
         while (v) {    // include the rest parameter, as it may have an initializer
@@ -1689,13 +1703,7 @@ ICodeModule *ICodeGenerator::genFunction(FunctionStmtNode *f, bool isConstructor
         }
         icg.addParameterLabel(icg.setLabel(icg.getLabel()));    // to provide the entry-point for the default case
     }
-    v = f->function.restParameter;
-    if (v) {
-        icg.mHasRestParameter = true;
-        if (v->name && (v->name->getKind() == ExprNode::identifier)) {
-            icg.mHasNamedRestParameter = true;
-        }
-    }
+
     if (isConstructor) {
         /*
            See if the first statement is an expression statement consisting
@@ -1851,7 +1859,7 @@ TypedRegister ICodeGenerator::genStmt(StmtNode *p, LabelSet *currentLabelSet)
                       // constructor code generator. Slot variable
                       // initializers get added to this function.
                     ccg = new ICodeGenerator(classContext, thisClass, kNoFlags);   
-                    ccg->allocateParameter(mContext->getWorld().identifiers["this"], thisClass);   // always parameter #0
+                    ccg->allocateParameter(mContext->getWorld().identifiers["this"], false, thisClass);   // always parameter #0
                 }
                 
                 ICodeGenerator scg(classContext, thisClass, kIsStaticMethod);   // static initializer code generator.
@@ -1939,7 +1947,7 @@ TypedRegister ICodeGenerator::genStmt(StmtNode *p, LabelSet *currentLabelSet)
                     TypedRegister thisValue = TypedRegister(0, thisClass);
                     ArgumentList *args = new ArgumentList();
                     ICodeGenerator icg(classContext, thisClass, kIsStaticMethod);
-                    icg.allocateParameter(mContext->getWorld().identifiers["this"], thisClass);   // always parameter #0
+                    icg.allocateParameter(mContext->getWorld().identifiers["this"], false, thisClass);   // always parameter #0
                     if (superclass)
                         icg.call(icg.getStatic(superclass, superclass->getName()), thisValue, args);
                     if (thisClass->hasStatic(mInitName))
@@ -2325,7 +2333,6 @@ TypedRegister ICodeGenerator::genStmt(StmtNode *p, LabelSet *currentLabelSet)
                     // Bind the incoming exception ...
                     if (mExceptionRegister.first == NotABanana)
                         mExceptionRegister = allocateRegister(mContext->getWorld().identifiers["__exceptionObject__"], &Any_Type);
-                    variableList->setRegisterForVariable(c->name, mExceptionRegister);
 
                     genStmt(c->stmt);
                     if (finallyLabel)
@@ -2419,7 +2426,7 @@ void ICodeGenerator::readICode(const char *fileName)
             Context *classContext = new Context(mContext->getWorld(), thisScope);
             ICodeGenerator scg(classContext, thisClass, kIsStaticMethod);
             ICodeGenerator ccg(classContext, thisClass, kNoFlags);
-            ccg.allocateParameter(mContext->getWorld().identifiers["this"], thisClass);
+            ccg.allocateParameter(mContext->getWorld().identifiers["this"], false, thisClass);
             thisClass->defineStatic(mInitName, &Function_Type);
 
             mContext->getGlobalObject()->defineVariable(className, &Type_Type, JSValue(thisClass));
@@ -2433,8 +2440,8 @@ void ICodeGenerator::readICode(const char *fileName)
                     String methodName, resultTypeName;
                     element->getValue(widenCString("name"), methodName);
                     element->getValue(widenCString("type"), resultTypeName);
-                    VariableList *theVariableList = new VariableList();
-                    theVariableList->add(mContext->getWorld().identifiers["this"], TypedRegister(0, thisClass));
+                    ParameterList *theParameterList = new ParameterList();
+                    theParameterList->add(mContext->getWorld().identifiers["this"], TypedRegister(0, thisClass), false);
                     uint32 pCount = 1;
                     XMLNodeList &parameters = element->children();
                     for (XMLNodeList::const_iterator k = parameters.begin(); k != parameters.end(); k++) {
@@ -2445,7 +2452,7 @@ void ICodeGenerator::readICode(const char *fileName)
                             element->getValue(widenCString("name"), parameterName);
                             element->getValue(widenCString("type"), parameterTypeName);
                             JSType *parameterType = findType(mContext->getWorld().identifiers[parameterTypeName]);
-                            theVariableList->add(mContext->getWorld().identifiers[parameterName], TypedRegister(pCount++, parameterType));
+                            theParameterList->add(mContext->getWorld().identifiers[parameterName], TypedRegister(pCount++, parameterType), false);
                         }
                     }
                     
@@ -2461,12 +2468,10 @@ void ICodeGenerator::readICode(const char *fileName)
                         icp.ParseSourceFromString(str);
 
                         ICodeModule *icm = new ICodeModule(icp.mInstructions, 
-                                                            theVariableList,       /* VariableList *variables */
+                                                            NULL,                   /* VariableList *variables */
+                                                            theParameterList,       /* ParameterList *parameters */
                                                             icp.mMaxRegister, 
-                                                            pCount,                 /* uint32 maxParameter, */
                                                             NULL,                   /* InstructionMap *instructionMap */
-                                                            false,                  /* bool hasRestParameter, */
-                                                            false,                  /* bool hasNamedRestParameter */
                                                             resultType);
                         thisClass->defineMethod(methodName, new JSFunction(icm));
                     }
@@ -2493,7 +2498,7 @@ void ICodeGenerator::readICode(const char *fileName)
                 TypedRegister thisValue = TypedRegister(0, thisClass);
                 ArgumentList *args = new ArgumentList(0);
                 ICodeGenerator icg(mContext, thisClass, kIsStaticMethod);
-                icg.allocateParameter(mContext->getWorld().identifiers["this"], thisClass);   // always parameter #0
+                icg.allocateParameter(mContext->getWorld().identifiers["this"], false, thisClass);   // always parameter #0
                 if (superclass)
                     icg.call(icg.getStatic(superclass, superclass->getName()), thisValue, args);
                 if (thisClass->hasStatic(mInitName))
diff --git a/js2/src/icodegenerator.h b/js2/src/icodegenerator.h
index 800161760c35..69abe8984e36 100644
--- a/js2/src/icodegenerator.h
+++ b/js2/src/icodegenerator.h
@@ -51,59 +51,92 @@ namespace ICG {
     using namespace JSClasses;
     
 
-    struct VariableList {
+    struct VariableList {       // Maps from variable (parameter) name to a TypedRegister.
+                                // But because we also want to map from a register number to
+                                // it's type, we keep the TypedRegsters in a separate array and
+                                // just store the index in the name map.
 
         typedef std::map<String, uint32, std::less<String> > VariableMap;
+        typedef VariableMap::value_type MapValue;
+
         VariableMap variableMap;
-
-        std::vector<TypedRegister> registerMap;
+        std::vector<TypedRegister> registerList;
     
-        void setRegisterForVariable(const StringAtom& name, TypedRegister r) 
-        {
-            VariableMap::iterator i = variableMap.find(name);
-            ASSERT(i != variableMap.end());
-            registerMap[(*i).second] = r;
-        }
-
         TypedRegister findVariable(const StringAtom& name)
         {
             VariableMap::iterator i = variableMap.find(name);
-            return (i == variableMap.end()) ? TypedRegister(NotARegister, &None_Type) : registerMap[(*i).second];
+            return (i == variableMap.end()) 
+                        ? TypedRegister(NotARegister, &None_Type) 
+                        : registerList[i->second];
         }
 
         void add(const StringAtom& name, TypedRegister r)
         {
-            variableMap[name] = r.first;
-            registerMap.resize(r.first + 1);
-            registerMap[r.first] = r;
+            variableMap.insert(MapValue(name, r.first));
+            registerList.resize(r.first + 1);
+            registerList[r.first] = r;
         }
 
         TypedRegister getRegister(uint32 i)
         {
-            ASSERT(i < registerMap.size());
-            return registerMap[i];
+            ASSERT(i < registerList.size());
+            return registerList[i];
         }
 
+
     };
 
+    struct ParameterList : public VariableList {
+        typedef enum { 
+            NoRestParameter, 
+            HasRestParameterBeforeBar, 
+            HasRestParameterAfterBar, 
+            HasUnnamedRestParameter 
+        } RestParameterStatus;
+
+        
+        
+        std::vector<bool> mOptionalParameters;      // whether or not a parameter has an optional value
+                                                    // ordered by lexical ordering === register number.
+        RestParameterStatus mRestParameter;
+        uint32 mPositionalCount;                    // number of positional parameters
+
+
+
+
+        ParameterList() : mRestParameter(NoRestParameter), mPositionalCount(0) { }
+
+        void add(const StringAtom& name, TypedRegister r, bool isOptional)
+        {
+            VariableList::add(name, r);
+            mOptionalParameters.resize(r.first + 1);
+            mOptionalParameters[r.first] = isOptional;
+        }
+
+        uint32 size()   { return registerList.size(); }     // the variableMap may be larger since it contains aliases
+
+        bool isOptional(uint32 i)   { ASSERT(i < mOptionalParameters.size()); return mOptionalParameters[i]; }
+
+        void setRestParameter(RestParameterStatus rs)   { mRestParameter = rs; }
+        void setPositionalCount(uint32 x)               { mPositionalCount = x; }
+
+    };
+
+
     typedef std::map<uint32, uint32, std::less<uint32> > InstructionMap;
-   
 
     class ICodeModule {
     public:
         ICodeModule(InstructionStream *iCode, VariableList *variables,
-                    uint32 maxRegister, uint32 maxParameter,
+                    ParameterList *parameters,
+                    uint32 maxRegister,
                     InstructionMap *instructionMap, 
-                    bool hasRestParameter, bool hasNamedRestParameter,
                     JSType *resultType) :
-            its_iCode(iCode), itsVariables(variables),
-            mParameterCount(maxParameter), itsMaxRegister(maxRegister),
+            its_iCode(iCode), itsVariables(variables), itsParameters(parameters),
+            itsMaxRegister(maxRegister),
             mID(++sMaxID), mInstructionMap(instructionMap), 
             mParameterInit(NULL), 
-            mNonOptionalParameterCount(maxParameter),
             mEntryPoint(0),
-            mHasRestParameter(hasRestParameter),
-            mHasNamedRestParameter(hasNamedRestParameter),
             mResultType(resultType)
         {
         }
@@ -122,16 +155,13 @@ namespace ICG {
         
         InstructionStream *its_iCode;
         VariableList *itsVariables;
-        uint32 mParameterCount;
+        ParameterList *itsParameters;
         uint32 itsMaxRegister;
         uint32 mID;
         InstructionMap *mInstructionMap;
         String mFileName;
         uint32 *mParameterInit;
-        uint32 mNonOptionalParameterCount;
         uint32 mEntryPoint;
-        bool mHasRestParameter;
-        bool mHasNamedRestParameter;
         JSType *mResultType;
 
         static uint32 sMaxID;
@@ -172,10 +202,10 @@ namespace ICG {
         LabelList labels;
         
         Register mTopRegister;              // highest (currently) allocated register
-        uint32   mParameterCount;           // number of parameters declared for the function
-                                            // these must come before any variables declared.
         TypedRegister mExceptionRegister;   // reserved to carry the exception object.
         VariableList *variableList;         // name|register pair for each variable
+        ParameterList *parameterList;       // name|register pair for each parameter
+                                            // (with #0 reserved for 'this' regardless of scope)
         
         Context *mContext;                  // the world and global object
         LabelStack mLabelStack;             // stack of LabelEntry objects, one per nested looping construct
@@ -185,8 +215,6 @@ namespace ICG {
         JSClass *mClass;                    // enclosing class when generating code for methods
         ICodeGeneratorFlags mFlags;         // assorted flags
         LabelList *pLabels;                 // label for each parameter initialization entry point
-        bool mHasRestParameter;             // true if this function has a ... parameter
-        bool mHasNamedRestParameter;        // true if this function has a named ... parameter
 
         const StringAtom &mInitName;
 
@@ -204,7 +232,7 @@ namespace ICG {
             return mTopRegister++;
         }
 
-        void resetTopRegister() { mTopRegister = mParameterCount; }
+        void resetTopRegister() { mTopRegister = 0; }
         void resetStatement()   { resetTopRegister(); }
 
         TypedRegister allocateRegister(const StringAtom& name, JSType *type);
@@ -280,15 +308,40 @@ namespace ICG {
         void throwStmt(TypedRegister r)         { iCode->push_back(new Throw(r)); }
         void debuggerStmt()                     { iCode->push_back(new Debugger()); }
 
-        TypedRegister allocateVariable(const StringAtom& name);
-        TypedRegister allocateVariable(const StringAtom& name, const StringAtom& typeName);
-        TypedRegister allocateVariable(const StringAtom& name, JSType *type) ;
+        TypedRegister allocateVariable(const StringAtom& name)
+        { 
+            return allocateVariable(name, &Any_Type);
+        }
         
-        TypedRegister allocateParameter(const StringAtom& name)         { mParameterCount++; return allocateRegister(name, &Any_Type); }
-        TypedRegister allocateParameter(const StringAtom& name, const StringAtom& typeName) 
-                                                                        { mParameterCount++; return allocateRegister(name, findType(typeName)); }
-        TypedRegister allocateParameter(const StringAtom& name, JSType *type) 
-                                                                        { mParameterCount++; return allocateRegister(name, type); }
+        TypedRegister allocateVariable(const StringAtom& name, const StringAtom& typeName)
+        {
+            return allocateVariable(name, findType(typeName));
+        }
+        
+        TypedRegister allocateVariable(const StringAtom& name, JSType *type)
+        { 
+            TypedRegister r = allocateRegister(name, type);
+            variableList->add(name, r);
+            return r;
+        }
+        
+        TypedRegister allocateParameter(const StringAtom& name, bool isOptional)
+        { 
+            return allocateParameter(name, isOptional, &Any_Type);
+        }
+        
+        TypedRegister allocateParameter(const StringAtom& name, bool isOptional, const StringAtom& typeName)
+        {
+            return allocateParameter(name, isOptional, findType(typeName));
+        }
+        
+        TypedRegister allocateParameter(const StringAtom& name, bool isOptional, JSType *type)
+        { 
+            TypedRegister r = allocateRegister(name, type);
+            parameterList->add(name, r, isOptional);
+            return r;
+        }
+
         
         Formatter& print(Formatter& f);
         
diff --git a/js2/src/interpreter.cpp b/js2/src/interpreter.cpp
index a42f484feb6e..20e10310fcb6 100644
--- a/js2/src/interpreter.cpp
+++ b/js2/src/interpreter.cpp
@@ -160,11 +160,11 @@ ICodeModule* Context::compileFunction(const String &source)
     ICodeGenerator icg(this);
     ASSERT(e->getKind() == ExprNode::functionLiteral);
     FunctionExprNode* f = static_cast<FunctionExprNode*>(e);
-    icg.allocateParameter(getWorld().identifiers["this"]);   // always parameter #0
+    icg.allocateParameter(getWorld().identifiers["this"], false);   // always parameter #0
     VariableBinding* v = f->function.parameters;
     while (v) {
         if (v->name && (v->name->getKind() == ExprNode::identifier))
-            icg.allocateParameter((static_cast<IdentifierExprNode*>(v->name))->name);
+            icg.allocateParameter((static_cast<IdentifierExprNode*>(v->name))->name, false);
         v = v->next;
     }
     icg.genStmt(f->function.body);
@@ -719,97 +719,85 @@ JSValue Context::interpret(ICodeModule* iCode, const JSValues& args)
                         ICodeModule *icm = target->getICode();
                         ArgumentList *args = op4(call);
 
-                        // mParameterCount includes 'this' and also 1 for a named rest parameter
+                        // the parameter count includes 'this' and any named rest parameter
                         //
-                        uint32 pCount = icm->mParameterCount - 1;
+                        uint32 pCount = icm->itsParameters->size() - 1;   // we won't be passing 'this' via the arg list array
+                        // callArgs will be the actual args passed to the target, put into correct register order.
+                        // It has room for the rest parameter.
                         ArgumentList *callArgs = new ArgumentList(pCount, Argument(TypedRegister(NotARegister, &Null_Type), NULL));
-                        if (icm->mHasNamedRestParameter) pCount--;
 
-/*
-
-    For new style, there must be enough un-named parameters to satisfy #unnamed-positional, but no
-    more than #total positional (unless there's a rest parameter). Extras go to the optional parameters first, then to rest.
-
-    Named parameters 
-
-*/
-
-
-                        // walk along the given arguments, handling each.
-                        // might be good to optimize the case of calls without named arguments and/or rest parameters
-                        JSArray *restArg = NULL;
-                        uint32 restIndex = 0;
+                        // don't want to count the rest parameter while processing the others 
+                        if (icm->itsParameters->mRestParameter != ParameterList::NoRestParameter) pCount--;
+                        
+                        
                         uint32 i;
+                        JSArray *restArg = NULL;
+                        
+                        // first match all named arguments with their intended target locations
                         for (i = 0; i < args->size(); i++) {
-                            if ((*args)[i].second) {       // a named argument
-                                TypedRegister r = icm->itsVariables->findVariable(*((*args)[i].second));
-                                bool isParameter = false;
-                                if (r.first != NotABanana) {   // we found the name in the target's list of variables
-                                    if (r.first < icm->mParameterCount) { // make sure we didn't match a local var                                            
-                                        ASSERT(r.first <= callArgs->size());
-                                        // the named argument is arriving in slot i, but needs to be r instead
-                                        // r.first is the intended target register, we subtract 1 since the callArgs array doesn't include 'this'
-                                        // here's where we could detect over-writing a positional arg with a named one if that is illegal
-                                        // if (callArgs[r.first - 1].first.first != NotARegister)...
-                                        (*registers)[(*args)[i].first.first] = (*registers)[(*args)[i].first.first].convert(r.second);
-                                        (*callArgs)[r.first - 1] = Argument((*args)[i].first, NULL);   // no need to copy the name through?
-                                        isParameter = true;
-                                    }
-                                }
-                                if (!isParameter) {     // wasn't a parameter, make it a property of the rest parameter (if there is one) 
-                                    if (icm->mHasRestParameter) {
-                                        if (icm->mHasNamedRestParameter) {
-                                            if (restArg == NULL) {
-                                                restArg = new JSArray();
-                                                restArg->setProperty(*(*args)[i].second, (*registers)[(*args)[i].first.first]);
-                                                (*registers)[(*args)[i].first.first] = restArg;
-                                                (*callArgs)[pCount] = Argument(TypedRegister((*args)[i].first.first, &Array_Type), NULL);
-                                            }
-                                            else
-                                                restArg->setProperty(*(*args)[i].second, (*registers)[(*args)[i].first.first]);
+                            
+                            const StringAtom *argName = (*args)[i].second;
 
+                            TypedRegister parameter = icm->itsParameters->findVariable(*argName);
+                            if (parameter.first == NotARegister) {  
+                                // arg name doesn't match any parameter name, it's a candidate
+                                // for the rest parameter (if there is one)
+                                if (icm->itsParameters->mRestParameter == ParameterList::NoRestParameter)
+                                    throw new JSException("Named argument doesn't match parameter name in call with no rest parameter");
+                                else {
+                                    if (icm->itsParameters->mRestParameter != ParameterList::HasUnnamedRestParameter) {
+                                        // if the name is a numeric literal >= 0, use it as an array index
+                                        // otherwise just set the named property.
+                                        const char16 *c = argName->c_str();
+                                        const char16 *end;
+                                        double d = stringToDouble(c, c + argName->length(), end);
+
+                                        if ((d != d) || (d < 0) || (d != (int)d)) { // a non-numeric or negative value                                             
+                                            if (icm->itsParameters->mRestParameter == ParameterList::HasRestParameterBeforeBar)
+                                                throw new JSException("Non-numeric or negative argument name for positional rest parameter");
                                         }
-                                        // else just throw it away 
+                                        else {  // shift the index value down by the number of positional parameters
+                                            StringFormatter s;
+                                            s << ((int)d - icm->itsParameters->mPositionalCount);
+                                            argName = &mWorld.identifiers[s];
+                                        }
+                                        
+                                        TypedRegister argument = (*args)[i].first;   // this is the argument whose name didn't match
+
+                                        if (restArg == NULL) {
+                                            // allocate the rest argument and then subvert the register being used for the
+                                            // argument under consideration to hold the newly created rest argument.
+                                            restArg = new JSArray();
+                                            restArg->setProperty(*argName, (*registers)[argument.first]);   // put it into the rest argument
+                                            (*registers)[argument.first] = restArg;
+                                            // The callArgs for the rest parameter position gets loaded from that slot 
+                                            (*callArgs)[pCount] = Argument(TypedRegister(argument.first, &Array_Type), NULL);
+                                        }
+                                        else
+                                            restArg->setProperty(*argName, (*registers)[argument.first]);
                                     }
-                                    else 
-                                        throw new JSException("Named argument doesn't match parameter name in call with no rest parameter");
-                                        // what about matching the named rest parameter ? aaarrggh!
+                                    // else just throw it away 
                                 }
                             }
                             else {
-                                if (i >= pCount) {  // more args than expected
-                                    if (icm->mHasRestParameter) {
-                                        if (icm->mHasNamedRestParameter) {
-                                            if (restArg == NULL) {
-                                                restArg = new JSArray();
-                                                (*restArg)[restIndex++] = (*registers)[(*args)[i].first.first];
-                                                (*registers)[(*args)[i].first.first] = restArg;
-                                                (*callArgs)[pCount] = Argument(TypedRegister((*args)[i].first.first, &Array_Type), NULL);
-                                            }
-                                            else
-                                                (*restArg)[restIndex++] = (*registers)[(*args)[i].first.first];
-                                        }
-                                        // else just throw it away 
-                                    }
-                                    else
-                                        throw new JSException("Too many arguments in call");
-                                }
-                                else {
-                                    TypedRegister r = icm->itsVariables->getRegister(i + 1);    // the variable list includes 'this'
-                                    (*registers)[(*args)[i].first.first] = (*registers)[(*args)[i].first.first].convert(r.second);
-                                    (*callArgs)[i] = (*args)[i];  // it's a positional, just slap it in place
-                                }
+                                uint32 targetIndex = parameter.first - 1;           // this is the register number we're targetting
+                                TypedRegister targetParameter = (*callArgs)[targetIndex].first;
+                                if (targetParameter.first != NotARegister)          // uh oh, some other argument wants this parameter
+                                    throw new JSException("Two (or more) arguments have the same name");
+                                (*callArgs)[targetIndex] = (*args)[i];
                             }
                         }
-                        uint32 contiguousArgs = 0;
-                        for (i = 0; i < args->size(); i++) {
-                            Argument &arg = (*args)[i];
-                            if (arg.first.first == NotARegister) break;
-                            contiguousArgs++;
+
+
+                        // make sure that all non-optional parameters have values
+                        for (i = 0; i < pCount; i++) {
+                            TypedRegister parameter = (*callArgs)[i].first;
+                            if (parameter.first == NotARegister) {  // doesn't have an assigned argument
+                                if (!icm->itsParameters->isOptional(i + 1))     // and parameter (allowing for 'this') doesn't have an optional value
+                                    throw new JSException("No argument supplied for non-optional parameter");
+                            }
                         }
-                        if ((contiguousArgs + 1) < icm->mNonOptionalParameterCount) // there's always a 'this' in R0 (even though it might be null)
-                            throw new JSException("Too few arguments in call");
-                        
+
                         mLinkage = new Linkage(mLinkage, ++mPC, mActivation, mGlobal, op1(call));
                         mActivation = new Activation(icm, mActivation, (*registers)[op3(call).first], callArgs);
                         registers = &mActivation->mRegisters;
diff --git a/js2/src/xmlparser.h b/js2/src/xmlparser.h
index 6232a19d0236..9aafebfdd2ef 100644
--- a/js2/src/xmlparser.h
+++ b/js2/src/xmlparser.h
@@ -63,7 +63,7 @@ public:
     XMLTag(String name) : mName(name), mFlag(Tag)  { }
     
     void addAttribute(const String &name, const String &value)    { mAttributeList.insert(AttributeValue(name, value) ); }
-    bool getValue(const String &name, String &value);
+    bool getValue(const String &name, String &value);   // returns the value of the most newly inserted attribute 'name'.
     bool hasAttribute(const String &name)                 { return (mAttributeList.find(name) != mAttributeList.end()); }
 
     String &name()      { return mName; }