31: Add void type

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

@@ -29,7 +29,7 @@ parameter
   ;
 
 braced_block
-  : OBRK statement+ CBRK
+  : OBRK (statement | functionCall SCOL)+ CBRK
   ;
 
 
@@ -69,7 +69,7 @@ field_assignment
   ;
 
 return_statement
-  : RETURN expression SCOL
+  : RETURN expression? SCOL
   ;
 
 destroy_statement
@@ -116,6 +116,7 @@ type
   | BOOLEAN
   | FLOAT
   | IDENT
+  | VOID
   ;
 
 functionCall
@@ -181,6 +182,7 @@ DIV: '/';
 BOOLEAN: 'bool';
 INTEGER: 'int';
 FLOAT: 'float';
+VOID: 'void';
 
 INTEGER_LITERAL
   : [0-9]+

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

@@ -176,6 +176,11 @@ public class ContextAnalysis extends KlangBaseVisitor<Node> {
     int col = ctx.start.getCharPositionInLine();
     Type declaredType = Type.getByName(ctx.type_annotation().type().getText());
 
+    if (declaredType.equals(Type.getVoidType())) {
+      String error = "Type " + declaredType.getName() + " can not be used to declare variables.";
+      throw new RuntimeException(Helper.getErrorPrefix(line, col) + error);
+    }
+
     if (!declaredType.isPrimitiveType() && this.structs.get(declaredType.getName()) == null) {
       String error = "Type " + declaredType.getName() + " not defined.";
       throw new RuntimeException(Helper.getErrorPrefix(line, col) + error);
@@ -244,10 +249,21 @@ 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.line = ctx.start.getLine();
+      result.type = Type.getVoidType();
+      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);
-    result.type = expression.type;
     result.line = ctx.start.getLine();
+    result.type = expression.type;
     result.col = ctx.start.getCharPositionInLine();
     return result;
   }
@@ -721,7 +737,7 @@ public class ContextAnalysis extends KlangBaseVisitor<Node> {
     Type returnType = Type.getByName(ctx.returnType.type().getText());
     this.currentDeclaredReturnType = returnType;
 
-    if (!returnType.isPrimitiveType() && this.structs.get(returnType.getName()) == null) {
+    if (!returnType.isPrimitiveType() && this.structs.get(returnType.getName()) == null && !returnType.equals(Type.getVoidType())) {
       String error = "Type " + returnType.getName() + " not defined.";
       throw new RuntimeException(Helper.getErrorPrefix(line, col) + error);
     }
@@ -767,6 +783,11 @@ public class ContextAnalysis extends KlangBaseVisitor<Node> {
     int col = ctx.start.getCharPositionInLine();
     Type type = Type.getByName(ctx.type_annotation().type().getText());
 
+    if (type.equals(Type.getVoidType())) {
+      String error = "Type " + type.getName() + " cannot be used to declare a parameter.";
+      throw new RuntimeException(Helper.getErrorPrefix(line, col) + error);
+    }
+
     if (!type.isPrimitiveType() && this.structs.get(type.getName()) == null) {
       String error = "Type " + type.getName() + " not defined.";
       throw new RuntimeException(Helper.getErrorPrefix(line, col) + error);

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

@@ -12,6 +12,7 @@ import java.util.HashSet;
 
 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.*;
 import de.hsrm.compiler.Klang.helper.*;
 
@@ -115,7 +116,8 @@ public class Klang {
       PrettyPrintVisitor.ExWriter ex = new PrettyPrintVisitor.ExWriter(w);
       PrettyPrintVisitor printVisitor = new PrettyPrintVisitor(ex);
       root.welcome(printVisitor);
-      System.out.println(w.toString());
+      generateOutput(out, w.toString());
+      return;
     }
 
     if (evaluate) {
@@ -123,7 +125,11 @@ public class Klang {
       System.out.println("\nEvaluating the source code:");
       EvalVisitor evalVisitor = new EvalVisitor(structs);
       Value result = root.welcome(evalVisitor);
-      generateOutput(out, "Result was: " + result.asObject().toString());
+      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

@@ -20,12 +20,17 @@ 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 StructType(name);
     }
   }

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

@@ -0,0 +1,38 @@
+package de.hsrm.compiler.Klang.types;
+
+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 missmatch: cannot combine " + this.getName() + " and " + that.getName());
+  }
+
+  @Override
+  public boolean isPrimitiveType() {
+    return false;
+  }
+
+  @Override
+  public boolean isNumericType() {
+    return false;
+  }
+
+}

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

@@ -413,6 +413,9 @@ 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

@@ -589,7 +589,9 @@ public class GenASM implements Visitor<Void> {
 
   @Override
   public Void visit(ReturnStatement e) {
-    e.expression.welcome(this);
+    if (e.expression != null) {
+      e.expression.welcome(this);
+    }
     this.ex.write("    movq %rbp, %rsp\n");
     this.ex.write("    popq %rbp\n");
     this.ex.write("    ret\n");

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) {
-    e.expression.welcome(this);
+    if (e.expression != null) {
+      e.expression.welcome(this);
+    }
     return null;
   }
 

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

@@ -304,8 +304,11 @@ public class PrettyPrintVisitor implements Visitor<Void> {
 
   @Override
   public Void visit(ReturnStatement e) {
-    ex.write("return ");
-    e.expression.welcome(this);
+    ex.write("return");
+    if (e.expression != null) {
+      ex.write(" ");
+      e.expression.welcome(this);
+    }
     ex.write(";");
     return null;
   }