Merge remote-tracking branch 'origin/master'

src/main/java/abstractSyntaxTree/Class/FieldDecl.java

@@ -4,6 +4,7 @@ import TypeCheck.AbstractType;
 import TypeCheck.TypeCheckException;
 import TypeCheck.TypeCheckHelper;
 import TypeCheck.TypeCheckResult;
+import abstractSyntaxTree.Expression.IExpression;
 import abstractSyntaxTree.Node;
 import abstractSyntaxTree.Program;
 import org.objectweb.asm.ClassWriter;
@@ -18,11 +19,13 @@ import java.util.Objects;
 public class FieldDecl extends AbstractType implements Node {
 
     public String type; // from parser
-    public String identifier; // from parser
+    public String identifier;// from parser
+    public IExpression expression; // value of the field
 
-    public FieldDecl(String type, String identifier){
+    public FieldDecl(String type, String identifier, IExpression expression){
         this.type = type;
         this.identifier = identifier;
+        this.expression = expression;
     }
     public TypeCheckResult typeCheck(HashMap<String, HashMap<String, String>> typeContext) throws TypeCheckException {
 
@@ -46,7 +49,6 @@ public class FieldDecl extends AbstractType implements Node {
     }
 
     public void codeGen(ClassWriter cw) {
-        //TODO: Do we have fields with initial values? --> No dont think so --> assign
         FieldVisitor fv = cw.visitField(Opcodes.ACC_PUBLIC, identifier, getFieldDescriptor(), null, null);
         fv.visitEnd();
     }

src/main/java/abstractSyntaxTree/Class/MethodDecl.java

@@ -53,12 +53,10 @@ public class MethodDecl implements Node {
         return result;
     }
 
-
-    //TODO: Es wird kein Bytecode für Standardkonstruktoren für die Klassen generiert
-    //TODO: Stack computing schlägt fehl --> Reihenfolge aufruf? --> Sobald if-else / if / while drin sind? --> vllt auch schon bei MethodenDecl
     //Need to get the returnType of the method if it is an object
     // methodContext (class, (returnType, (identifier, parameter)))
-    public void codeGen(ClassWriter cw, HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext, HashMap<String, HashMap<String, String>> typeContext) throws Exception {
+    // typeContext (class, (type, identifier))
+    public void codeGen(ClassWriter cw, HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext, HashMap<String, HashMap<String, String>> typeContext, List<FieldDecl> fieldDecls) throws Exception {
 
         localVars.put("this", classThatContainsMethod);
         for (Parameter param : parameters.parameterList) {
@@ -73,18 +71,40 @@ public class MethodDecl implements Node {
 
             //Call the superclass constructor
             mv.visitVarInsn(Opcodes.ALOAD, 0);
+            mv.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);
+
+            HashMap<String, String> classFields = typeContext.get(classThatContainsMethod);
+
+            for (Map.Entry<String, String> entry : classFields.entrySet()) {
+                String fieldName = entry.getKey();
+                for (FieldDecl field : fieldDecls) {
+                    if (field.identifier.equals(fieldName)) {
+                        mv.visitVarInsn(Opcodes.ALOAD, 0);
+                        field.expression.codeGen(mv, localVars, typeContext, methodContext);
+                        descriptor = getFieldDescriptor(field.type);
+                        mv.visitFieldInsn(Opcodes.PUTFIELD, classThatContainsMethod, fieldName, descriptor);
+                    } else {
+                        throw new Exception("Field " + fieldName + " not found");
+                    }
+                }
+            }
 
             //Load the parameters onto the stack
             int localVarIndex = 1;
             for (Parameter param : parameters.parameterList) {
                 String paramType = param.type;
                 switch(paramType) {
-                    case "int", "boolean", "char" -> mv.visitVarInsn(Opcodes.ILOAD, localVarIndex);
+                    case "int", "boolean", "char" -> {
-                    default -> mv.visitVarInsn(Opcodes.ALOAD, localVarIndex);
+                        mv.visitVarInsn(Opcodes.ILOAD, localVarIndex);
+                        mv.visitVarInsn(Opcodes.ISTORE, localVarIndex);
+                    }
+                    default -> {
+                        mv.visitVarInsn(Opcodes.ALOAD, localVarIndex);
+                        mv.visitVarInsn(Opcodes.ASTORE, localVarIndex);
+                    }
                 }
                 localVarIndex++;
             }
-            mv.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/Object", "<init>", descriptor, false);
 
             mv.visitCode();
             codeBlock.codeGen(mv, localVars, typeContext, methodContext);
@@ -171,6 +191,19 @@ public class MethodDecl implements Node {
         return descriptor.toString();
     }
 
+    private String getFieldDescriptor(String type) {
+        switch (type) {
+            case "int":
+                return "I";
+            case "boolean":
+                return "Z";
+            case "char":
+                return "C";
+            default:
+                return "L" + type + ";";
+        }
+    }
+
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;

src/main/java/abstractSyntaxTree/Class/RefType.java

@@ -6,6 +6,7 @@ import TypeCheck.TypeCheckResult;
 import abstractSyntaxTree.Expression.IExpression;
 import abstractSyntaxTree.Node;
 import abstractSyntaxTree.Parameter.ParameterList;
+import abstractSyntaxTree.Statement.BlockStatement;
 import org.objectweb.asm.ClassWriter;
 import org.objectweb.asm.Opcodes;
 
@@ -79,7 +80,7 @@ public class RefType extends AbstractType implements Node {
     // Method for code generation which iterates over all the field declarations
     // and method declarations and calls their CodeGen methods
 
-        public void codeGen(ClassWriter cw, HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext, HashMap<String, HashMap<String, String>> typeContext) throws Exception {
+    public void codeGen(ClassWriter cw, HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext, HashMap<String, HashMap<String, String>> typeContext) throws Exception {
 
         cw.visit(Opcodes.V1_8, Opcodes.ACC_PUBLIC, name, null,
                 "java/lang/Object", null);
@@ -88,8 +89,21 @@ public class RefType extends AbstractType implements Node {
             field.codeGen(cw);
         }
 
+        boolean hasCustomConstructor = false;
         for (MethodDecl method : methodDecls) {
-           method.codeGen(cw, methodContext, typeContext);
+            if (method.name.equals(name) && method.returnType == null) {
+                hasCustomConstructor = true;
+                break;
+            }
+        }
+
+        if (!hasCustomConstructor) {
+            MethodDecl standardConstructor = new MethodDecl(name, null, name, new ParameterList(new ArrayList<>()), new BlockStatement(new ArrayList<>(), "void"));
+            standardConstructor.codeGen(cw, methodContext, typeContext, fieldDecls);
+        }
+
+        for (MethodDecl method : methodDecls) {
+           method.codeGen(cw, methodContext, typeContext, fieldDecls);
         }
         cw.visitEnd();
     }

src/main/java/abstractSyntaxTree/Expression/BinaryExpression.java

@@ -76,105 +76,96 @@ public class BinaryExpression extends AbstractType implements IExpression{
         Label expressionEnd = new Label();     //End of the whole expression
 
         // Bytecode for the binary operation
-        switch (operator) {
+        if (operator.equals("+") || operator.equals("-") || operator.equals("*") || operator.equals("/")) {
-            case "&&":
+            switch (operator) {
-                left.codeGen(mv, localVars, typeContext, methodContext);
+                case "+" -> {
-                mv.visitJumpInsn(Opcodes.IFEQ, operationFalse); // IFEQ --> "if equals to zero" (false) --> if left exp is false
+                    left.codeGen(mv, localVars, typeContext, methodContext);
+                    right.codeGen(mv, localVars, typeContext, methodContext);
+                    mv.visitInsn(Opcodes.IADD);
+                }
+                case "-" -> {
+                    left.codeGen(mv, localVars, typeContext, methodContext);
+                    right.codeGen(mv, localVars, typeContext, methodContext);
+                    mv.visitInsn(Opcodes.ISUB);
+                }
+                case "*" -> {
+                    left.codeGen(mv, localVars, typeContext, methodContext);
+                    right.codeGen(mv, localVars, typeContext, methodContext);
+                    mv.visitInsn(Opcodes.IMUL);
+                }
+                case "/" -> {
+                    left.codeGen(mv, localVars, typeContext, methodContext);
+                    right.codeGen(mv, localVars, typeContext, methodContext);
+                    mv.visitInsn(Opcodes.IDIV);
+                }
+            }
+        } else {
+            switch (operator) {
+                case "&&" -> {
+                    left.codeGen(mv, localVars, typeContext, methodContext);
+                    mv.visitJumpInsn(Opcodes.IFEQ, operationFalse); // IFEQ --> "if equals to zero" (false) --> if left exp is false
 
-                right.codeGen(mv, localVars, typeContext, methodContext);
+                    right.codeGen(mv, localVars, typeContext, methodContext);
-                mv.visitJumpInsn(Opcodes.IFEQ, operationFalse); // If right exp is false, jump to the end of the whole expression
+                    mv.visitJumpInsn(Opcodes.IFEQ, operationFalse);
 
-                mv.visitJumpInsn(Opcodes.GOTO, operationTrue); // If it reaches this point, the right exp is true
+                    mv.visitJumpInsn(Opcodes.GOTO, operationTrue); // If it reaches this point, the right exp is true
-                break;
+                }
+                case "||" -> {
+                    left.codeGen(mv, localVars, typeContext, methodContext);
+                    mv.visitJumpInsn(Opcodes.IFNE, operationTrue); // IFNE --> "if not equals to zero" (true) --> if left exp is true
 
-            case "||":
+                    right.codeGen(mv, localVars, typeContext, methodContext);
-                left.codeGen(mv, localVars, typeContext, methodContext);
+                    mv.visitJumpInsn(Opcodes.IFNE, operationTrue);
-                mv.visitJumpInsn(Opcodes.IFNE, operationTrue); // IFNE --> "if not equals to zero" (true) --> if left exp is true
+                }
+                case "==" -> {
+                    // Keep in mind that only primitive types are allowed in this case (at this time)
 
-                right.codeGen(mv, localVars, typeContext, methodContext);
+                    left.codeGen(mv, localVars, typeContext, methodContext);
-                mv.visitJumpInsn(Opcodes.IFNE, operationTrue);
+                    right.codeGen(mv, localVars, typeContext, methodContext);
-                break;
 
-            case "==":
+                    mv.visitJumpInsn(Opcodes.IF_ICMPEQ, operationTrue); // If the two values are equal, jump to the end of the expression
-                // Keep in mind that only primitive types are allowed in this case (at this time)
+                }
+                case "<" -> {
+                    left.codeGen(mv, localVars, typeContext, methodContext);
+                    right.codeGen(mv, localVars, typeContext, methodContext);
 
-                left.codeGen(mv, localVars, typeContext, methodContext);
+                    mv.visitJumpInsn(Opcodes.IF_ICMPLT, operationTrue); // Checks only on less than, not equal
-                right.codeGen(mv, localVars, typeContext, methodContext);
+                }
+                case ">" -> {
+                    left.codeGen(mv, localVars, typeContext, methodContext);
+                    right.codeGen(mv, localVars, typeContext, methodContext);
 
-                mv.visitJumpInsn(Opcodes.IF_ICMPEQ, operationTrue); // If the two values are equal, jump to the end of the expression
+                    mv.visitJumpInsn(Opcodes.IF_ICMPGT, operationTrue); // Checks only on greater than, not equal
-                break;
+                }
+                case "<=" -> {
+                    left.codeGen(mv, localVars, typeContext, methodContext);
+                    right.codeGen(mv, localVars, typeContext, methodContext);
 
-            case "<":
+                    mv.visitJumpInsn(Opcodes.IF_ICMPLE, operationTrue); // Checks on less than OR equal
-                left.codeGen(mv, localVars, typeContext, methodContext);
+                }
-                right.codeGen(mv, localVars, typeContext, methodContext);
+                case ">=" -> {
+                    left.codeGen(mv, localVars, typeContext, methodContext);
+                    right.codeGen(mv, localVars, typeContext, methodContext);
 
-                mv.visitJumpInsn(Opcodes.IF_ICMPLT, operationTrue); // Checks only on less than, not equal
+                    mv.visitJumpInsn(Opcodes.IF_ICMPGE, operationTrue); // Checks on greater than OR equal
-                break;
+                }
+                case "!=" -> {
+                    left.codeGen(mv, localVars, typeContext, methodContext);
+                    right.codeGen(mv, localVars, typeContext, methodContext);
 
-            case ">":
+                    mv.visitJumpInsn(Opcodes.IF_ICMPNE, operationTrue); // Checks on not equal
-                left.codeGen(mv, localVars, typeContext, methodContext);
+                }
-                right.codeGen(mv, localVars, typeContext, methodContext);
+                default -> throw new TypeCheckException("The operator " + operator + " is not known.");
+            }
+            mv.visitLabel(operationFalse);
+            mv.visitInsn(Opcodes.ICONST_0); // Push false on the stack
+            mv.visitJumpInsn(Opcodes.GOTO, expressionEnd); // Jump to the end of the expression (skip the true push)
 
-                mv.visitJumpInsn(Opcodes.IF_ICMPGT, operationTrue); // Checks only on greater than, not equal
+            mv.visitLabel(operationTrue);
-                break;
+            mv.visitInsn(Opcodes.ICONST_1); // Push true on the stack
 
-            case "<=":
+            mv.visitLabel(expressionEnd);
-                left.codeGen(mv, localVars, typeContext, methodContext);
-                right.codeGen(mv, localVars, typeContext, methodContext);
-
-                mv.visitJumpInsn(Opcodes.IF_ICMPLE, operationTrue); // Checks on less than OR equal
-                break;
-
-            case ">=":
-                left.codeGen(mv, localVars, typeContext, methodContext);
-                right.codeGen(mv, localVars, typeContext, methodContext);
-
-                mv.visitJumpInsn(Opcodes.IF_ICMPGE, operationTrue); // Checks on greater than OR equal
-                break;
-
-            case "!=":
-                left.codeGen(mv, localVars, typeContext, methodContext);
-                right.codeGen(mv, localVars, typeContext, methodContext);
-
-                mv.visitJumpInsn(Opcodes.IF_ICMPNE, operationTrue); // Checks on not equal
-                break;
-
-            case "+":
-                left.codeGen(mv, localVars, typeContext, methodContext);
-                right.codeGen(mv, localVars, typeContext, methodContext);
-                mv.visitInsn(Opcodes.IADD);
-                break;
-
-            case "-":
-                left.codeGen(mv, localVars, typeContext, methodContext);
-                right.codeGen(mv, localVars, typeContext, methodContext);
-                mv.visitInsn(Opcodes.ISUB);
-                break;
-
-            case "*":
-                left.codeGen(mv, localVars, typeContext, methodContext);
-                right.codeGen(mv, localVars, typeContext, methodContext);
-                mv.visitInsn(Opcodes.IMUL);
-                break;
-
-            case "/":
-                left.codeGen(mv, localVars, typeContext, methodContext);
-                right.codeGen(mv, localVars, typeContext, methodContext);
-                mv.visitInsn(Opcodes.IDIV);
-                break;
-
-            default:
-                throw new TypeCheckException("The operator " + operator + " is not known.");
         }
-
-        mv.visitLabel(operationFalse);
-        mv.visitInsn(Opcodes.ICONST_0); // Push false on the stack
-        mv.visitJumpInsn(Opcodes.GOTO, expressionEnd); // Jump to the end of the expression (skip the true push)
-
-        mv.visitLabel(operationTrue);
-        mv.visitInsn(Opcodes.ICONST_1); // Push true on the stack
-
-        mv.visitLabel(expressionEnd);
     }
 
     @Override

src/main/java/abstractSyntaxTree/Expression/LocalVarIdentifier.java

@@ -46,40 +46,60 @@ public class LocalVarIdentifier extends AbstractType implements IExpression{
 
     @Override
     public void codeGen(MethodVisitor mv, LinkedHashMap<String, String> localVars, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext) throws Exception {
-        // Check if the variable is in the list of local variables
+        String type = null;
-        String type = localVars.get(identifier);
-        if (type == null){
-            throw new Exception("Variable " + identifier + " not declared");
-        }
 
-        // Find the index of the variable
+        // if it's a local variable
-        int index = -1;
+        if (localVars.containsKey(identifier)) {
-        int counter = 0;
+            type = localVars.get(identifier);
-        for (String key : localVars.keySet()){
+            // Find the index of the variable
-            if (key.equals(identifier)){
+            int index = -1;
-                index = counter+1; // +1 because the first local variable is at index 1, 0 is used for "this"
+            int counter = 0;
-                break;
+            for (String key : localVars.keySet()) {
+                if (key.equals(identifier)) {
+                    index = counter + 1; // +1 because the first local variable is at index 1, 0 is used for "this"
+                    break;
+                }
+                counter++;
             }
-            counter++;
-        }
 
-        if (index == -1){
+            if (index == -1) {
+                throw new Exception("Variable " + identifier + " not found");
+            }
+
+            // Load the variable onto the stack
+            switch (type) {
+                case "int", "boolean", "char":
+                    mv.visitVarInsn(Opcodes.ILOAD, index);
+                    break;
+                case "void":
+                    break;
+                default:
+                    mv.visitVarInsn(Opcodes.ALOAD, index);
+                    break;
+            }
+            // If it's a field
+        } else if (typeContext.get(thisClass).get(identifier) != null){
+            type = typeContext.get(thisClass).get(identifier);
+
+            // Load "this" onto the stack
+            mv.visitVarInsn(Opcodes.ALOAD, 0);
+            // Get the field from "this"
+            mv.visitFieldInsn(Opcodes.GETFIELD, thisClass, identifier, getFieldDescriptor(type));
+        } else
             throw new Exception("Variable " + identifier + " not found");
-        }
+    }
 
-        // Load the variable onto the stack
+    //TODO move this to a helper class and remove the doubled code in MethodDecl and in other places
-        switch (type){
+    private String getFieldDescriptor(String type) {
+        switch (type) {
             case "int":
-                mv.visitVarInsn(Opcodes.ILOAD, index);
+                return "I";
-                break;
             case "boolean":
-                mv.visitVarInsn(Opcodes.ILOAD, index);
+                return "Z";
-                break;
+            case "char":
-            case "void":
+                return "C";
-                break;
             default:
-                mv.visitVarInsn(Opcodes.ALOAD, index);
+                return "L" + type + ";";
-                break;
         }
     }
 

src/main/java/abstractSyntaxTree/Program.java

@@ -42,6 +42,7 @@ public class Program implements Node {
             typeContext.put(oneClass.name, classVars);
 
             // build method context
+
             HashMap<String, HashMap<String, ParameterList>> identifierAndMethod = new HashMap<>();
             for (MethodDecl methodDecl : oneClass.methodDecls){
                 if(methodDecl.returnType == null) continue;
@@ -52,15 +53,14 @@ public class Program implements Node {
             methodContext.put(oneClass.name, identifierAndMethod);
         }
 
-
         int mainCounter = 0;
         // check if main exists
         for(RefType oneClass : classes){
             if(oneClass.hasMain)
                 mainCounter++;
         }
-//        if(mainCounter != 1)
+        if(mainCounter != 1)
-//            throw new TypeCheckException("There is not 1 Main method.");
+            throw new TypeCheckException("There is not 1 Main method.");
 
         // typecheck each class
         TypeCheckResult result = new TypeCheckResult();
@@ -72,7 +72,7 @@ public class Program implements Node {
     }
 
     public void codeGen() throws Exception{
-        try (JarOutputStream jos = new JarOutputStream(new FileOutputStream("output.jar"))) {
+        try {
             for (RefType oneClass : classes) {
                 ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
                 cw.visit(Opcodes.V1_8, Opcodes.ACC_PUBLIC, oneClass.name, null, "java/lang/Object", null);
@@ -88,30 +88,9 @@ public class Program implements Node {
                     e.printStackTrace();
                 }
             }
+        } catch (Exception e) {
+            throw new RuntimeException(e);
         }
-
-
-                /*// Write the bytecode to a .class file in the .jar file
-                JarEntry entry = new JarEntry(oneClass.name + ".class");
-                jos.putNextEntry(entry);
-                jos.write(bytecode);
-                jos.closeEntry();
-            }
-        } catch (IOException e) {
-            e.printStackTrace();
-        }*/
-
-        /*
-        for(RefType oneClass : classes){
-            ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
-            cw.visit(Opcodes.V1_8, Opcodes.ACC_PUBLIC,oneClass.name, null,
-                    "java/lang/Object", null);
-            oneClass.codeGen(cw);
-
-            cw.visitEnd();
-            byte[] bytecode = cw.toByteArray();
-        }
-        */
     }
 
     @Override

src/main/java/abstractSyntaxTree/Statement/IfElseStatement.java

@@ -54,7 +54,7 @@ public class IfElseStatement extends AbstractType implements IStatement{
     }
 
 
-
+    //TODO: There are 2 NOPs and one athrow on the stack between the if-Block and else-Block execution --> I have no idea why
     @Override
     public void codeGen(MethodVisitor mv, LinkedHashMap<String, String> localVars, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext) throws Exception {
 
@@ -67,7 +67,8 @@ public class IfElseStatement extends AbstractType implements IStatement{
 
         mv.visitJumpInsn(Opcodes.IFEQ, conditionFalse); //Checks if the condition is false (0)
         ifStatement.codeGen(mv, blockLocalVars, typeContext, methodContext); //If the condition is true, execute the ifBlock
-        mv.visitJumpInsn(Opcodes.GOTO, statementEnd); //Jump to the end of the if-else statement
+
+        mv.visitJumpInsn(Opcodes.GOTO, statementEnd); //Jump to the end of the else statement
 
         mv.visitLabel(conditionFalse);
         elseStatement.codeGen(mv, blockLocalVars, typeContext, methodContext); //If the condition is false, execute the elseBlock

src/main/java/abstractSyntaxTree/Statement/LocalVarDecl.java

@@ -55,7 +55,19 @@ public class LocalVarDecl extends AbstractType implements IStatement{
     public void codeGen(MethodVisitor mv, LinkedHashMap<String, String> localVars, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext) throws Exception {
         localVars.put(identifier, type);
 
-        int index = localVars.size() - 1;
+        int index = -1;
+        int counter = 0;
+        for (String key : localVars.keySet()){
+            if (key.equals(identifier)){
+                index = counter+1; // +1 because the first local variable is at index 1, 0 is used for "this"
+                break;
+            }
+            counter++;
+        }
+
+        if (index == -1){
+            throw new Exception("Variable " + identifier + " not found");
+        }
 
         if (expression != null) {
             expression.codeGen(mv, localVars, typeContext,methodContext);
@@ -72,11 +84,7 @@ public class LocalVarDecl extends AbstractType implements IStatement{
 
             // Set a default value for the variable --> less problems
             switch (type) {
-                case "int":
+                case "int", "boolean", "char":
-                    mv.visitInsn(Opcodes.ICONST_1);
-                    mv.visitVarInsn(Opcodes.ISTORE, index);
-                    break;
-                case "boolean":
                     mv.visitInsn(Opcodes.ICONST_0);
                     mv.visitVarInsn(Opcodes.ISTORE, index);
                     break;

src/main/java/abstractSyntaxTree/Statement/WhileStatement.java

@@ -55,7 +55,6 @@ public class WhileStatement extends AbstractType implements IStatement {
         mv.visitJumpInsn(Opcodes.IFEQ, conditionFalse); // Checks if the condition is false (0)
 
         statement.codeGen(mv, blockLocalVars, typeContext, methodContext);
-        //statement.codeGen(mv);
         //TODO: If the block ends with a return statement, we might have to pop it from the stack
         //      So the next iteration starts with a clean stack
         mv.visitJumpInsn(Opcodes.GOTO, LoopStart); // Jump to the start of the while loop

src/main/java/astGenerator/ASTGenerator.java

@@ -56,7 +56,12 @@ public class ASTGenerator extends DecafBaseVisitor<Node> {
     }
 
     public Node generateFieldDecl(DecafParser.LocalVarDeclContext ctx) {
-        return new FieldDecl(ctx.type().getText(), ctx.Identifier().getText());
+        if (ctx.expression() != null) {
+            IExpression expression = (IExpression) visit(ctx.expression());
+            return new FieldDecl(ctx.type().getText(), ctx.Identifier().getText(), expression);
+        } else {
+            return new FieldDecl(ctx.type().getText(), ctx.Identifier().getText(), null);
+        }
     }
 
     @Override
@@ -198,7 +203,6 @@ public class ASTGenerator extends DecafBaseVisitor<Node> {
         return new AssignStatementExpression(ctx.Assign().getText(),(IExpression) left, (IExpression) right);
     }
 
-    //
     @Override
     public Node visitMethodCall(DecafParser.MethodCallContext ctx) {
         String methodName = ctx.Identifier().getText();