- Improved stack traces

- Removed class Evaluator.Levels
- Replaced Variable.Context by Variable.Argument & Variable.Local
- Added Evaluator.EvaluationStack

8 files changed, 204 insertions, 195 deletions

diff --git a/sources/scala/tools/scalai/Code.java b/sources/scala/tools/scalai/Code.java
index ac917211f9..44ae45d8c3 100644
--- a/sources/scala/tools/scalai/Code.java
+++ b/sources/scala/tools/scalai/Code.java
@@ -22,7 +22,7 @@ public class Code {
     public case Label(Symbol symbol, Variable[] variables, Code expression);
 
     public case Create(ScalaTemplate template); // !!! remove ?
-    public case Invoke(Code target, Function function, Code[] parameters, int pos, Symbol method);
+    public case Invoke(Code target, Function function, Code[] arguments, int pos);
     public case Load(Code target, Variable variable);
     public case Store(Code target, Variable variable, Code expression);
 
@@ -68,12 +68,12 @@ public class Code {
         case Create(ScalaTemplate template):
             return "Create(" + template + ")";
 
-        case Invoke(Code target, Function function, Code[] parameters, int pos, Symbol method):
+        case Invoke(Code target, Function function, Code[] arguments, int pos):
             StringBuffer buffer = new StringBuffer();
             buffer.append("Invoke(" + target + "," + function + "," + "[\n");
-            for (int i = 0; i < parameters.length; i++) {
+            for (int i = 0; i < arguments.length; i++) {
                 if (i > 0) buffer.append(",\n");
-                buffer.append(parameters[i]);
+                buffer.append(arguments[i]);
             }
             buffer.append("])");
             return buffer.toString();
diff --git a/sources/scala/tools/scalai/Compiler.java b/sources/scala/tools/scalai/Compiler.java
index f25fe10c6e..be58832dc8 100644
--- a/sources/scala/tools/scalai/Compiler.java
+++ b/sources/scala/tools/scalai/Compiler.java
@@ -30,6 +30,7 @@ import scalac.symtab.Symbol;
 import scalac.symtab.TermSymbol;
 import scalac.util.Debug;
 import scalac.util.Name;
+import scalac.util.Names;
 import scalac.util.Position;
 
 public class Compiler {
@@ -83,22 +84,25 @@ public class Compiler {
         } catch (Exception exception) {
             throw Debug.abort("equals", exception);
         }
+        // !!! should we have a symbol Any.equals as for hashcode and toString?
+        Symbol equals_symbol =
+            definitions.JAVA_OBJECT_CLASS.lookup(Names.equals);
+        assert equals_symbol != Symbol.NONE;
         CodePromise equals_code = new CodePromise(
             new CodeContainer(
-                null, // !!!
+                equals_symbol,
                 Code.Invoke(
                     Code.Invoke(
                         Code.Null,
                         Function.JavaMethod(getInvocationHandler_method),
                         new Code[] {
                             Code.Self},
-                        Position.NOPOS, null // !!!
-                    ),
+                        Position.NOPOS),
                     Function.JavaMethod(equals_method),
                     new Code[] {
                         Code.Load(
-                            Code.Null, Variable.Context(Evaluator.Levels.ARGS, 0))},
-                    Position.NOPOS, null), // !!!
+                            Code.Null, Variable.Argument(0))},
+                    Position.NOPOS),
                 0));
         // !!! any_methods.put(_, equals_code);
         any_methods.put(equals_method, equals_code);
@@ -118,7 +122,7 @@ public class Compiler {
                 definitions.HASHCODE,
                 Code.Invoke(
                     Code.Self, Function.HashCode, new Code[0],
-                    Position.NOPOS, definitions.HASHCODE),
+                    Position.NOPOS),
                 0));
         any_methods.put(definitions.HASHCODE, hashCode_code);
         any_methods.put(hashCode_method, hashCode_code);
@@ -142,7 +146,7 @@ public class Compiler {
                 definitions.TOSTRING,
                 Code.Invoke(
                     Code.Self, Function.ToString, new Code[0],
-                    Position.NOPOS, definitions.TOSTRING),
+                    Position.NOPOS),
                 0));
         any_methods.put(definitions.TOSTRING, toString_code);
         any_methods.put(toString_method, toString_code);
@@ -171,8 +175,8 @@ public class Compiler {
                     Code.Self, Function.JavaMethod(equals_method), new Code[] {
                         Code.Load(
                             Code.Null,
-                            Variable.Context(Evaluator.Levels.ARGS, 0)) },
-                    Position.NOPOS, definitions.EQEQ),
+                            Variable.Argument(0)) },
+                    Position.NOPOS),
                 0));
         any_methods.put(definitions.EQEQ, eqeq_code);
         environment.insertFunction(definitions.EQEQ, Function.EqEq);
@@ -188,11 +192,11 @@ public class Compiler {
                             Code.Self, Function.EqEq, new Code[] {
                                 Code.Load(
                                     Code.Null,
-                                    Variable.Context(Evaluator.Levels.ARGS, 0)) },
-                            Position.NOPOS, definitions.BANGEQ)),
+                                    Variable.Argument(0)) },
+                            Position.NOPOS)),
                     Function.JavaMethod(bang_method),
                     new Code[0],
-                    Position.NOPOS, definitions.BANGEQ),
+                    Position.NOPOS),
                 0));
         any_methods.put(definitions.BANGEQ, bangeq_code);
         environment.insertFunction(definitions.BANGEQ, Function.BangEq);
diff --git a/sources/scala/tools/scalai/Evaluator.java b/sources/scala/tools/scalai/Evaluator.java
index cdf1288390..9e5b98f6d8 100644
--- a/sources/scala/tools/scalai/Evaluator.java
+++ b/sources/scala/tools/scalai/Evaluator.java
@@ -17,7 +17,6 @@ import java.lang.reflect.Field;
 import java.lang.reflect.InvocationTargetException;
 
 import scala.runtime.RunTime;
-import scala.MatchError;
 
 import scalac.symtab.Symbol;
 import scalac.util.Debug;
@@ -25,16 +24,6 @@ import scalac.util.Debug;
 public class Evaluator {
 
     //########################################################################
-    // Public Interfaces
-
-    // !!! remove
-    public static interface Levels {
-        public static final int CLASS = 0;
-        public static final int ARGS = 1; // !!! use PARAM ?
-        public static final int BODY = 2;
-    }
-
-    //########################################################################
     // Private Classes
 
     // !!! remove ?
@@ -50,33 +39,44 @@ public class Evaluator {
         }
     }
 
+    public static class EvaluationStack {
+
+        public final EvaluationStack stack;
+        public final Symbol symbol;
+        public final Object self;
+        public final Object[] args;
+        public final Object[] vars;
+
+        public EvaluationStack(EvaluationStack stack, CodeContainer code,
+            Object self, Object[] args)
+        {
+            this.stack = stack;
+            this.symbol = code.symbol;
+            this.self = self;
+            this.args = args;
+            this.vars = new Object[code.stacksize];
+        }
+
+    }
+
     //########################################################################
     // Private Fields
 
-    private final Object[][] variables;
-    private Object self;
+    private EvaluationStack stack;
+    private EvaluatorException trace;
 
     //########################################################################
     // Public Constructors
 
     public Evaluator() {
-        this.variables = new Object[3][];
-        this.variables[Levels.CLASS] = null;
-        this.variables[Levels.ARGS] = null;
-        this.variables[Levels.BODY] = null;
-        this.self = null;
+        this.stack = null;
+        this.trace = null;
     }
 
     //########################################################################
     // Public Methods
 
     public Object evaluate(CodeContainer code) {
-        // !!! System.out.println("!!! EVALUATE");
-        // !!! System.out.println("!!! size           = " + size);
-        // !!! System.out.println("!!! code.symbol    = " +Debug.show(code.symbol));
-        // !!! System.out.println("!!! code.stacksize = " + code.stacksize);
-        // !!! System.out.println("!!! code.code      = " + code.code);
-        // !!! System.out.println("!!! ");
         return evaluate(code, null, new Object[0]);
     }
 
@@ -86,37 +86,10 @@ public class Evaluator {
 
     public Object evaluate(CodeContainer code, Object object, Object[] args) {
         try {
-        // !!! System.out.println("!!! EVALUATE");
-        // !!! System.out.println("!!! code.symbol    = " +Debug.show(code.symbol));
-        // !!! for (int i = 0; i < args.length; i++) {
-        // !!!     System.out.println("!!! arg" + i + "           = " + Debug.show(args[i]));
-        // !!! }
-        // !!! System.out.println("!!! code.stacksize = " + code.stacksize);
-        // !!! System.out.println("!!! code.code      = " + code.code);
-        // !!! System.out.println("!!! ");
-
-        Object backup_self = self;
-        Object[] backup_args = variables[Levels.ARGS];
-        Object[] backup_body = variables[Levels.BODY];
-        self = object;
-        variables[Levels.ARGS] = args;
-        variables[Levels.BODY] = new Object[code.stacksize];
-        Object result = evaluate(code.code);
-        self = backup_self;
-        variables[Levels.ARGS] = backup_args;
-        variables[Levels.BODY] = backup_body;
-
-        // !!! System.out.println("!!! RETURN");
-        // !!! System.out.println("!!! code.symbol    = " +Debug.show(code.symbol));
-        // !!! System.out.println("!!! result.class   = " + Debug.show(result));
-
-        return result;
-        } catch (EvaluatorException exception) {
-            throw exception;
-        } catch (Error exception) {
-            throw exception;
-        } catch (Throwable exception) {
-            throw Debug.abort(exception);
+            stack = new EvaluationStack(stack, code, object, args);
+            return evaluate(code.code);
+        } finally {
+            stack = stack.stack;
         }
     }
 
@@ -157,16 +130,15 @@ public class Evaluator {
             store(evaluate(target), variable, evaluate(expression));
             return RunTime.box();
 
-        case Invoke(Code target, Function function, Code[] parameters, int pos, Symbol method):
+        case Invoke(Code target, Function function, Code[] arguments, int pos):
             Object object = evaluate(target);
-            Object[] args = new Object[parameters.length];
-            for (int i = 0; i < args.length; i++) {
-                args[i] = evaluate(parameters[i]);
-            }
-            try { // !!! indent
+            Object[] args = new Object[arguments.length];
+            for (int i = 0; i < args.length; i++)
+                args[i] = evaluate(arguments[i]);
+            try {
                 return invoke(object, function, args);
             } catch (EvaluatorException exception) {
-                exception.addCall(pos, method);
+                if (stack.symbol != null) exception.addScalaCall(stack.symbol, pos); // !!! remove test
                 throw exception;
             }
 
@@ -205,8 +177,7 @@ public class Evaluator {
             return null;
 
         case Self:
-            // !!! System.out.println("!!! Self: " + Debug.show(self));
-            return self;
+            return stack.self;
 
         default:
             throw Debug.abort("illegal code", code);
@@ -223,7 +194,6 @@ public class Evaluator {
             return evaluate(code, object, args);
 
         case Member(Symbol symbol):
-            // !!! handle case where object is null
             return getScalaObject(object).invoke(object, symbol, args);
 
         case Label(Symbol symbol):
@@ -268,7 +238,7 @@ public class Evaluator {
         case Throw:
             assert args.length == 0 : Debug.show(args);
             assert object instanceof Throwable : object.getClass();
-            throw new EvaluatorException((Throwable)object);
+            return throw_((Throwable)object);
 
         case StringPlus:
             assert args.length == 1 : Debug.show(args);
@@ -285,11 +255,11 @@ public class Evaluator {
 
         case HashCode:
             assert args.length == 0 : Debug.show(args);
-            return new Integer(getScalaObject(object).hashCode());
+            return new Integer(getHandlerObject(object).hashCode());
 
         case ToString:
             assert args.length == 0 : Debug.show(args);
-            return getScalaObject(object).toString();
+            return getHandlerObject(object).toString();
 
         default:
             throw Debug.abort("illegal function", function);
@@ -298,16 +268,11 @@ public class Evaluator {
 
     private Object invoke(Object object, Constructor constructor,Object[]args){
         try {
-            // !!! System.out.println("!!! object " + (object == null ? "null" : object.getClass().getName()));
-            // !!! System.out.println("!!! constr " + constructor);
-            // !!! System.out.println("!!! nbargs " + args.length);
             return constructor.newInstance(args);
-        } catch (MatchError exception) {
-            return exception(exception);
         } catch (ExceptionInInitializerError exception) {
-            return exception(exception.getException());
+            return throw_(exception);
         } catch (InvocationTargetException exception) {
-            return exception(exception.getTargetException());
+            return throw_(exception);
         } catch (InstantiationException exception) {
             String msg1 = "\n  object = " + Debug.show(object);
             String msg2 = "\n  constr = " + Debug.show(constructor);
@@ -329,14 +294,12 @@ public class Evaluator {
     private Object invoke(Object object, Method method, Object[] args) {
         try {
             return method.invoke(object, args);
-        } catch (MatchError exception) {
-            return exception(exception);
         } catch (NullPointerException exception) {
-            return exception(exception);
+            return throw_(exception);
         } catch (ExceptionInInitializerError exception) {
-            return exception(exception.getException());
+            return throw_(exception);
         } catch (InvocationTargetException exception) {
-            return exception(exception.getTargetException());
+            return throw_(exception);
         } catch (IllegalAccessException exception) {
             String msg1 = "\n  object = " + Debug.show(object);
             String msg2 = "\n  method = " + Debug.show(method);
@@ -353,25 +316,24 @@ public class Evaluator {
     //########################################################################
     // Private Methods - store
 
-    // !!! return void ?
     private Object store(Object object, Variable variable, Object value) {
         switch (variable) {
 
         case Global(_):
             return ((Variable.Global)variable).value = value;
 
-        case Context(int level, int index):
-            // !!! System.out.println("!!! store Context: level = " + level + ", index = " + index);
-            return variables[level][index] = value;
-
         case Module(_, _):
             return ((Variable.Module)variable).value = value;
 
         case Member(int index):
-            // !!! handle case where object is null
-            // !!! System.out.println("!!! store Member: index = " + index + ", length = " + getScalaObject(object).variables.length);
             return getScalaObject(object).variables[index] = value;
 
+        case Argument(int index):
+            return stack.args[index] = value;
+
+        case Local(int index):
+            return stack.vars[index] = value;
+
         case JavaField(Field field):
             return store(object, field, value);
 
@@ -385,9 +347,9 @@ public class Evaluator {
             field.set(object, value);
             return value;
         } catch (NullPointerException exception) {
-            return exception(exception);
+            return throw_(exception);
         } catch (ExceptionInInitializerError exception) {
-            return exception(exception.getException());
+            return throw_(exception);
         } catch (IllegalAccessException exception) {
             String msg1 = "\n  object = " + Debug.show(object);
             String msg2 = "\n  field  = " + Debug.show(field);
@@ -410,9 +372,6 @@ public class Evaluator {
         case Global(Object value):
             return value;
 
-        case Context(int level, int index):
-            return variables[level][index];
-
         case Module(CodePromise body, Object value):
             if (value != null) return value;
             ((Variable.Module)variable).body = null;
@@ -420,11 +379,14 @@ public class Evaluator {
             return load(object, variable);
 
         case Member(int index):
-            // !!! handle case where object is null
-            // !!! System.out.println("!!! loadScala: self  = " + Debug.show(object) + ", index = " + index);
-            // !!! System.out.println("!!! loadScala: value = " + Debug.show(getScalaObject(object).variables[index]));
             return getScalaObject(object).variables[index];
 
+        case Argument(int index):
+            return stack.args[index];
+
+        case Local(int index):
+            return stack.vars[index];
+
         case JavaField(Field field):
             return load(object, field);
 
@@ -437,9 +399,9 @@ public class Evaluator {
         try {
             return field.get(object);
         } catch (NullPointerException exception) {
-            return exception(exception);
+            return throw_(exception);
         } catch (ExceptionInInitializerError exception) {
-            return exception(exception.getException());
+            return throw_(exception);
         } catch (IllegalAccessException exception) {
             String msg1 = "\n  object = " + Debug.show(object);
             String msg2 = "\n  field  = " + Debug.show(field);
@@ -452,6 +414,20 @@ public class Evaluator {
     }
 
     //########################################################################
+    // Private Methods - throw
+
+    private Object throw_(Throwable exception) {
+        if (exception.getCause() != null && (
+                exception instanceof ExceptionInInitializerError ||
+                exception instanceof InvocationTargetException))
+            exception = exception.getCause();
+        if (trace == null || trace.getCause() != exception)
+            trace = new EvaluatorException(exception);
+        trace.addScalaLeavePoint();
+        throw trace;
+    }
+
+    //########################################################################
     // Private Methods - box
 
     // !!!
@@ -518,30 +494,15 @@ public class Evaluator {
     }
 
     private ScalaObject getScalaObject(Object object) {
-        if (object == null)
-            return (ScalaObject)exception(new NullPointerException()); // !!!
-        assert object instanceof Proxy : object.getClass();
-        return (ScalaObject)Proxy.getInvocationHandler(object);
+        Object handler = getHandlerObject(object);
+        assert handler instanceof ScalaObject : handler.getClass();
+        return (ScalaObject)handler;
     }
 
-    private Object exception(Throwable exception) {
-        // !!! return an exception result
-        if (exception instanceof EvaluatorException) {
-            throw (EvaluatorException)exception;
-        }
-        if (exception instanceof MatchError) {
-            throw new EvaluatorException(exception, new Error());
-        }
-        if (exception instanceof Error) {
-            throw (Error)exception;
-        }
-        throw new EvaluatorException(exception, new Error());
-    }
-
-    // !!! remove ?
-    private Error abort(Exception exception) {
-        // !!! return an abort result ?
-        return Debug.abort(exception);
+    private Object getHandlerObject(Object object) {
+        if (object == null) return throw_(new NullPointerException());
+        assert object instanceof Proxy : object.getClass();
+        return Proxy.getInvocationHandler(object);
     }
 
     //########################################################################
diff --git a/sources/scala/tools/scalai/EvaluatorException.java b/sources/scala/tools/scalai/EvaluatorException.java
index 4853bbcc9f..b262eac367 100644
--- a/sources/scala/tools/scalai/EvaluatorException.java
+++ b/sources/scala/tools/scalai/EvaluatorException.java
@@ -8,7 +8,8 @@
 
 package scalai;
 
-import java.util.Stack;
+import java.util.List;
+import java.util.ArrayList;
 
 import scalac.Global;
 import scalac.ast.parser.Sourcefile;
@@ -20,66 +21,101 @@ public class EvaluatorException extends RuntimeException {
     //########################################################################
     // Private Fields
 
-    private final Throwable exception;
-    private final Throwable cut;
-    private final Stack stack; // !!! rename ?
-    private final Stack symbols;
+    private final StackTraceElement[] trace;
+    private final List stack;
+
+    private int stop;
 
     //########################################################################
     // Public Constructors
 
-    public EvaluatorException(Throwable exception) {
-        this(exception, null);
-    }
-
-    public EvaluatorException(Throwable exception, Throwable cut) {
-        this.exception = exception;
-        this.cut = cut;
-        this.stack = new Stack();
-        this.symbols = new Stack();
+    public EvaluatorException(Throwable cause) {
+        super(cause);
+        this.trace = getTraceOf(cause);
+        this.stack = new ArrayList();
+        this.stop = trace.length;
     }
 
     //########################################################################
     // Public Methods
 
-    public void addCall(int pos, Symbol symbol) {
-        stack.push(new Integer(pos));
-        symbols.push(symbol);
+    public void addScalaCall(Symbol method, int pos) {
+        StringBuffer buffer = new StringBuffer();
+        buffer.append(method.owner().fullNameString());
+        buffer.append('.');
+        buffer.append(method.nameString());
+        buffer.append('(');
+        buffer.append(Sourcefile.files[Position.file(pos)]);
+        buffer.append(':');
+        buffer.append(Position.line(pos));
+        buffer.append(")");
+        stack.add(buffer.toString());
     }
 
-    public String mkString(Global global) {
-        StringBuffer buffer = new StringBuffer();
-        // !!! if (exception != null)buffer.append(Strings.stackTrace(exception));
-        buffer.append(exception.toString());
-        for (int i = 0; i < stack.size(); i++) {
-            buffer.append('\n');
-            int pos = ((Integer)stack.elementAt(i)).intValue();
-            buffer.append("        at " +
-                context(global, (Symbol)symbols.elementAt(i)) +
-                "(" + Sourcefile.files[Position.file(pos)] + ":" +
-                Position.line(pos) + ")");
-        }
-        return buffer.toString();
+    public void addScalaEntryPoint() {
+        StackTraceElement[] current = getCurrentTrace();
+        // find entry point
+        int length = Math.min(trace.length, current.length);
+        int entry = 0;
+        while (entry < length && trace[entry].equals(current[entry])) entry++;
+        assert entry <= stop : "entry = " + entry + " > " + stop + " = stop";
+        // skip calls through proxy class
+        while (entry > 0 && traceAtStartsWith(entry - 1, "$Proxy")) entry--;
+        // save new trace end
+        stop = entry;
+    }
+
+    public void addScalaLeavePoint() {
+        StackTraceElement[] current = getCurrentTrace();
+        // find leave point
+        int length = Math.min(trace.length, current.length);
+        int leave = 0;
+        while (leave < length && trace[leave].equals(current[leave])) leave++;
+        // skip calls through interpreter & reflection
+        int start = leave;
+        while (traceAtStartsWith(start, "scalai.")) start++;
+        while (traceAtStartsWith(start, "java.lang.reflect.")) start++;
+        while (traceAtStartsWith(start, "sun.reflect.")) start++;
+        // complete stack with java trace
+        for (int i = stop - 1; start <= i; i--) stack.add(trace[i]);
+        // save new trace end
+        stop = leave;
     }
 
-    // !!! remove ? modify ?
-    public String toString() {
-        return getClass().getName() + ": " + exception;
+    public Object[] getScalaStackTrace() {
+        return stack.toArray();
+    }
+
+    public String getScalaErrorMessage(boolean withTrace) {
+        String line = System.getProperty("line.separator", "\n");
+        StringBuffer buffer = new StringBuffer();
+        buffer.append(getCause().toString());
+        if (withTrace)
+            for (int i = 0; i < stack.size(); i++)
+                buffer.append(line).append("        at ").append(stack.get(i));
+        return buffer.toString();
     }
 
     //########################################################################
     // Private Methods
 
-    private String context(Global global, Symbol symbol) {
-        if (symbol == null) return "<top-level>";
-        assert !symbol.isClass() : symbol.defString();
-        Symbol owner = symbol.owner();
-        if (owner == global.definitions.ROOT_CLASS
-            || symbol.owner() == Symbol.NONE) // !!! || ...
-        {
-            return symbol.name.toString();
+    private boolean traceAtStartsWith(int index, String prefix) {
+        if (trace.length <= index) return false;
+        return trace[index].getClassName().startsWith(prefix);
+    }
+
+    private StackTraceElement[] getCurrentTrace() {
+        return getTraceOf(new Error());
+    }
+
+    private StackTraceElement[] getTraceOf(Throwable exception) {
+        StackTraceElement[] trace = exception.getStackTrace();
+        for (int i = 0; i < trace.length / 2; i++) {
+            StackTraceElement element = trace[i];
+            trace[i] = trace[trace.length - i - 1];
+            trace[trace.length - i - 1] = element;
         }
-        return owner.fullName() + "." + symbol.name;
+        return trace;
     }
 
     //########################################################################
diff --git a/sources/scala/tools/scalai/ExpressionCompiler.java b/sources/scala/tools/scalai/ExpressionCompiler.java
index 3283f01773..e77e94a5d1 100644
--- a/sources/scala/tools/scalai/ExpressionCompiler.java
+++ b/sources/scala/tools/scalai/ExpressionCompiler.java
@@ -34,9 +34,8 @@ public class ExpressionCompiler {
         this.definitions = definitions;
         this.constants = constants;
         this.context = context;
-        for (int i = 0; i < params.length; i++) {
-            context.insertVariable(params[i], Variable.Context(Evaluator.Levels.ARGS,i));
-        }
+        for (int i = 0; i < params.length; i++)
+            context.insertVariable(params[i], Variable.Argument(i));
     }
 
     //########################################################################
@@ -70,7 +69,7 @@ public class ExpressionCompiler {
 
         case ValDef(_, _, _, Tree body):
             Symbol symbol = tree.symbol();
-            Variable variable = Variable.Context(Evaluator.Levels.BODY, context.push());
+            Variable variable = Variable.Local(context.push());
             context.insertVariable(symbol, variable);
             // !!! this should be done in an earlier phase
             Code value = body != Tree.Empty ?
@@ -102,7 +101,10 @@ public class ExpressionCompiler {
             for (int i = 0; i < params.length; i++) {
                 vars[i] = context.lookupVariable(params[i].symbol());
                 // !!!
-                assert vars[i] instanceof Variable.Context:Debug.show(vars[i]);
+                assert
+                    vars[i] instanceof Variable.Argument ||
+                    vars[i] instanceof Variable.Local :
+                    Debug.show(vars[i]);
             }
             context.insertLabel(symbol);
             return Code.Label(symbol, vars, compute(body));
@@ -252,7 +254,7 @@ public class ExpressionCompiler {
             }
         }
         Code[] args = compute(trees);
-        return Code.Invoke(object, function, args, target.pos,context.owner());
+        return Code.Invoke(object, function, args, target.pos);
     }
 
     //########################################################################
diff --git a/sources/scala/tools/scalai/Interpreter.java b/sources/scala/tools/scalai/Interpreter.java
index df92fa362a..17f2bbeb04 100644
--- a/sources/scala/tools/scalai/Interpreter.java
+++ b/sources/scala/tools/scalai/Interpreter.java
@@ -287,7 +287,7 @@ public class Interpreter {
             if (interactive) writer.println(value + ": " + type);
             return;
         case Error(EvaluatorException exception):
-            writer.println(exception.mkString(global));
+            writer.println(exception.getScalaErrorMessage(true));
             return;
         }
     }
diff --git a/sources/scala/tools/scalai/ScalaObject.java b/sources/scala/tools/scalai/ScalaObject.java
index 0d9f65c7c9..21df3f6da2 100644
--- a/sources/scala/tools/scalai/ScalaObject.java
+++ b/sources/scala/tools/scalai/ScalaObject.java
@@ -41,8 +41,15 @@ public class ScalaObject implements InvocationHandler {
     //########################################################################
     // Public Methods - InvocationHandler interface
 
-    public Object invoke(Object self, Method method, Object[] args) {
-        return template.invoke(self, method, args);
+    public Object invoke(Object self, Method method, Object[] args)
+        throws Throwable
+    {
+        try {
+            return template.invoke(self, method, args);
+        } catch (EvaluatorException exception) {
+            exception.addScalaEntryPoint();
+            throw exception.getCause();
+        }
     }
 
     //########################################################################
diff --git a/sources/scala/tools/scalai/Variable.java b/sources/scala/tools/scalai/Variable.java
index 42e2c4d4b5..df9e6f8804 100644
--- a/sources/scala/tools/scalai/Variable.java
+++ b/sources/scala/tools/scalai/Variable.java
@@ -18,15 +18,11 @@ public class Variable {
     //########################################################################
     // Public Cases
 
-    // !!! Object/Field(int index)
-    // !!! Frame/Local(int index)
-    // !!! Stack(int index)
-    // !!! Java(Field field)
-
     public case Global(Object value);
     public case Module(CodePromise body, Object value);
-    public case Context(int level, int index);
     public case Member(int index);
+    public case Argument(int index);
+    public case Local(int index);
     public case JavaField(Field field);
 
     //########################################################################
@@ -41,12 +37,15 @@ public class Variable {
         case Module(CodePromise body, Object value):
             return "Module(" + body + "," + Debug.show(value) + ")";
 
-        case Context(int level, int index):
-            return "Context(" + level + "," + index + ")";
-
         case Member(int index):
             return "Member(" + index + ")";
 
+        case Argument(int index):
+            return "Context(" + index + ")";
+
+        case Local(int index):
+            return "Variable(" + index + ")";
+
         case JavaField(Field field):
             return "Java(" + field + ")";