31: Add void type

src/main/antlr4/de/hsrm/compiler/Klang/Klang.g4

@@ -33,7 +33,7 @@ parameter
   ;
 
 braced_block
-  : OBRK statement+ CBRK
+  : OBRK (statement | functionCall SCOL)+ CBRK
   ;
 
 
@@ -73,7 +73,7 @@ field_assignment
   ;
 
 return_statement
-  : RETURN expression SCOL
+  : RETURN expression? SCOL
   ;
 
 destroy_statement
@@ -120,6 +120,7 @@ type
   | BOOLEAN
   | FLOAT
   | IDENT
+  | VOID
   ;
 
 functionCall
@@ -186,6 +187,7 @@ DIV: '/';
 BOOLEAN: 'bool';
 INTEGER: 'int';
 FLOAT: 'float';
+VOID: 'void';
 
 INTEGER_LITERAL
   : [0-9]+

src/main/java/de/hsrm/compiler/Klang/ContextAnalysis.java

@@ -186,6 +186,11 @@ public class ContextAnalysis extends KlangBaseVisitor<Node> {
     var line = ctx.start.getLine();
     var col = ctx.start.getCharPositionInLine();
 
+    if (declaredType.equals(Type.getVoidType())) {
+      var error = "Type " + declaredType.getName() + " can not be used to declare variables.";
+      throw new RuntimeException(Helper.getErrorPrefix(line, col) + error);
+    }
+
     if (!declaredType.isPrimitiveType() && !structDefs.containsKey(declaredType.getName()) && !enumDefs.containsKey(declaredType.getName())) {
       var error = "Type " + declaredType.getName() + " not defined.";
       throw new RuntimeException(Helper.getErrorPrefix(line, col) + error);
@@ -266,6 +271,18 @@ public class ContextAnalysis extends KlangBaseVisitor<Node> {
 
   @Override
   public Node visitReturn_statement(KlangParser.Return_statementContext ctx) {
+    if (currentDeclaredReturnType.equals(Type.getVoidType())) {
+      ReturnStatement result = new ReturnStatement();
+      result.type = Type.getVoidType();
+      result.line = ctx.start.getLine();
+      result.col = ctx.start.getCharPositionInLine();
+      if (ctx.expression() != null) {
+        String error = "Cannot return an expression from a void function.";
+        throw new RuntimeException(Helper.getErrorPrefix(result.line, result.col) + error);
+      }
+      return result;
+    }
+
     Expression expression = (Expression) this.visit(ctx.expression());
     ReturnStatement result = new ReturnStatement(expression);
 
@@ -277,8 +294,8 @@ public class ContextAnalysis extends KlangBaseVisitor<Node> {
       }
     }
 
-    result.type = expression.type;
     result.line = ctx.start.getLine();
+    result.type = expression.type;
     result.col = ctx.start.getCharPositionInLine();
     return result;
   }
@@ -826,26 +843,29 @@ public class ContextAnalysis extends KlangBaseVisitor<Node> {
   public Node visitParameter(KlangParser.ParameterContext ctx) {
     var parameterName = ctx.IDENT().getText();
     var parameterType = Type.getByName(ctx.type_annotation().type().getText());
-
-    if (structDefs.containsKey(parameterName)) {
     var line = ctx.start.getLine();
     var col = ctx.start.getCharPositionInLine();
+
+    if (parameterType.equals(Type.getVoidType())) {
+      var error = "Type " + parameterType.getName() + " cannot be used to declare a parameter.";
+      throw new RuntimeException(Helper.getErrorPrefix(line, col) + error);
+    }
+
+    if (structDefs.containsKey(parameterName)) {
       var error = "Parameter name " + parameterName + " duplicates a struct of the same name.";
       throw new RuntimeException(Helper.getErrorPrefix(line, col) + error);
     }
 
     if (enumDefs.containsKey(parameterName)) {
-      var line = ctx.start.getLine();
-      var col = ctx.start.getCharPositionInLine();
       var error = "Parameter name " + parameterName + " duplicates an enum of the same name.";
       throw new RuntimeException(Helper.getErrorPrefix(line, col) + error);
     }
 
     if (!parameterType.isPrimitiveType() && !structDefs.containsKey(parameterType.getName()) && !enumDefs.containsKey(parameterType.getName())) {
-      var line = ctx.type_annotation().start.getLine();
-      var col = ctx.type_annotation().start.getCharPositionInLine();
+      var typeLine = ctx.type_annotation().start.getLine();
+      var typeCol = ctx.type_annotation().start.getCharPositionInLine();
       var error = "Type " + parameterType.getName() + " not defined.";
-      throw new RuntimeException(Helper.getErrorPrefix(line, col) + error);
+      throw new RuntimeException(Helper.getErrorPrefix(typeLine, typeCol) + error);
     }
 
     var parameter = new Parameter(parameterName);

src/main/java/de/hsrm/compiler/Klang/Klang.java

@@ -1,9 +1,11 @@
 package de.hsrm.compiler.Klang;
 
+import de.hsrm.compiler.Klang.helper.*;
 import de.hsrm.compiler.Klang.nodes.EnumDefinition;
 import de.hsrm.compiler.Klang.nodes.FunctionDefinition;
 import de.hsrm.compiler.Klang.nodes.Node;
 import de.hsrm.compiler.Klang.nodes.StructDefinition;
+import de.hsrm.compiler.Klang.types.Type;
 import de.hsrm.compiler.Klang.visitors.EvalVisitor;
 import de.hsrm.compiler.Klang.visitors.GenASM;
 import de.hsrm.compiler.Klang.visitors.PrettyPrintVisitor;
@@ -120,7 +122,11 @@ public class Klang {
       System.out.println("\nEvaluating the source code:");
       EvalVisitor evalVisitor = new EvalVisitor(structDefs);
       Value result = root.welcome(evalVisitor);
+      if (result.type.equals(Type.getVoidType())) {
+        generateOutput(out, "Result was void");
+      } else {
         generateOutput(out, "Result was: " + result.asObject().toString());
+      }
       return;
     }
 

src/main/java/de/hsrm/compiler/Klang/nodes/statements/ReturnStatement.java

@@ -11,6 +11,10 @@ public class ReturnStatement extends Statement {
         this.expression = expression;
     }
 
+    public ReturnStatement() {
+      this.expression = null;    
+    }
+
     @Override
     public <R> R welcome(Visitor<R> v) {
         return v.visit(this);

src/main/java/de/hsrm/compiler/Klang/types/Type.java

@@ -27,12 +27,17 @@ public abstract class Type {
     return NullType.getType();
   }
 
+  public static VoidType getVoidType() {
+    return VoidType.getType();
+  }
+
   public static Type getByName(String name) {
     switch (name) {
       case "bool": return getBooleanType();
       case "int": return getIntegerType();
       case "float": return getFloatType();
       case "null": return getNullType();
+      case "void": return getVoidType();
       default: return new NamedType(name);
     }
   }

src/main/java/de/hsrm/compiler/Klang/types/VoidType.java

@@ -0,0 +1,45 @@
+package de.hsrm.compiler.Klang.types;
+
+import de.hsrm.compiler.Klang.Value;
+
+public class VoidType extends Type {
+
+  private static VoidType instance;
+
+  public static VoidType getType() {
+    if (instance != null) {
+        return instance;
+    }
+    instance = new VoidType();
+    return instance;
+}
+
+  @Override
+  public String getName() {
+    return "void";
+  }
+
+  @Override
+  public Type combine(Type that) {
+    if (that.equals(this)) {
+      return this;
+    }
+    throw new RuntimeException("Type mismatch: cannot combine " + this.getName() + " and " + that.getName());
+  }
+
+  @Override
+  public boolean valuesEqual(Value a, Value b) {
+    throw new RuntimeException("Can not compare void types.");
+  }
+
+  @Override
+  public boolean isPrimitiveType() {
+    return false;
+  }
+
+  @Override
+  public boolean isNumericType() {
+    return false;
+  }
+
+}

src/main/java/de/hsrm/compiler/Klang/visitors/EvalVisitor.java

@@ -396,6 +396,9 @@ public class EvalVisitor implements Visitor<Value> {
 
   @Override
   public Value visit(ReturnStatement e) {
+    if (e.expression == null) {
+      return new Value(null, Type.getVoidType());
+    }
     return e.expression.welcome(this);
   }
 

src/main/java/de/hsrm/compiler/Klang/visitors/GenASM.java

@@ -525,7 +525,9 @@ public class GenASM implements Visitor<Void> {
 
   @Override
   public Void visit(ReturnStatement e) {
+    if (e.expression != null) {
       e.expression.welcome(this);
+    }
 
     // The ReturnStatement visitor is kindly removing the
     // stack space that was allocated by the FunctionDefinition

src/main/java/de/hsrm/compiler/Klang/visitors/GetVars.java

@@ -194,7 +194,9 @@ class GetVars implements Visitor<Void> {
 
   @Override
   public Void visit(ReturnStatement e) {
+    if (e.expression != null) {
       e.expression.welcome(this);
+    }
     return null;
   }
 

src/main/java/de/hsrm/compiler/Klang/visitors/PrettyPrintVisitor.java

@@ -310,8 +310,11 @@ public class PrettyPrintVisitor implements Visitor<Void> {
 
   @Override
   public Void visit(ReturnStatement e) {
-    ex.write("return ");
+    ex.write("return");
+    if (e.expression != null) {
+      ex.write(" ");
       e.expression.welcome(this);
+    }
     ex.write(";");
     return null;
   }