VoidType: Add tests and fix some bugs

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

@@ -68,13 +68,13 @@ public class ContextAnalysis extends KlangBaseVisitor<Node> {
 
   @Override
   public Node visitBraced_block(KlangParser.Braced_blockContext ctx) {
-    int actualStatementCount = 0;
+    var actualStatementCount = 0;
-    int declaredStatementCount = ctx.statement().size();
+    var declaredStatementCount = ctx.statement().size();
-    boolean hasReturn = false;
+    var hasReturn = false;
-    Statement[] statements = new Statement[declaredStatementCount];
+    var statements = new Statement[declaredStatementCount];
 
     for (int i = 0; i < declaredStatementCount; i++) {
-      Node currentStatement = this.visit(ctx.statement(i));
+      var currentStatement = visit(ctx.statement(i));
       statements[i] = (Statement) currentStatement;
       actualStatementCount += 1;
 
@@ -83,7 +83,7 @@ public class ContextAnalysis extends KlangBaseVisitor<Node> {
       if (currentStatement.type != null && !(currentStatement instanceof VariableDeclaration)) {
         // check whether the type matches
         try {
-          this.currentDeclaredReturnType.combine(currentStatement.type);
+          currentDeclaredReturnType.combine(currentStatement.type);
         } catch (Exception e) {
           throw new RuntimeException(
               Helper.getErrorPrefix(currentStatement.line, currentStatement.col) + e.getMessage());
@@ -99,14 +99,15 @@ public class ContextAnalysis extends KlangBaseVisitor<Node> {
     // If there was unreachable code in this block,
     // create a shorter statements array and copy the statements to there
     if (actualStatementCount < declaredStatementCount) {
-      Statement[] newStatements = new Statement[actualStatementCount];
+      var newStatements = new Statement[actualStatementCount];
       System.arraycopy(statements, 0, newStatements, 0, actualStatementCount);
       statements = newStatements;
     }
 
     // if this block contains at least one statement that guarantees a return value,
     // we indicate that this block guarantees a return value by setting result.type
-    Block result = new Block(statements);
+    var result = new Block(statements);
+
     if (hasReturn) {
       result.type = this.currentDeclaredReturnType;
     }
@@ -272,28 +273,28 @@ public class ContextAnalysis extends KlangBaseVisitor<Node> {
   @Override
   public Node visitReturn_statement(KlangParser.Return_statementContext ctx) {
     if (currentDeclaredReturnType.equals(Type.getVoidType())) {
-      ReturnStatement result = new ReturnStatement();
+      var 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.";
+        var 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());
+    var expression = (Expression) visit(ctx.expression());
-    ReturnStatement result = new ReturnStatement(expression);
 
     // Check if this expression is a tail recursion
     if (expression instanceof FunctionCall funCall) {
-      if (funCall.name.equals(this.currentFunctionDefinitionName)) {
+      if (funCall.name.equals(currentFunctionDefinitionName)) {
         // Flag this function call
         funCall.isTailRecursive = true;
       }
     }
 
+    var result = new ReturnStatement(expression);
     result.line = ctx.start.getLine();
     result.type = expression.type;
     result.col = ctx.start.getCharPositionInLine();
@@ -766,6 +767,11 @@ public class ContextAnalysis extends KlangBaseVisitor<Node> {
     var line = ctx.start.getLine();
     var col = ctx.start.getCharPositionInLine();
 
+    if (structFieldType.equals(Type.getVoidType())) {
+      var error = "Type void can not be used as a struct field type.";
+      throw new RuntimeException(Helper.getErrorPrefix(line, col) + error);
+    }
+
     if (!structFieldType.isPrimitiveType() && !structDefs.containsKey(structFieldType.getName()) && !enumDefs.containsKey(structFieldType.getName())) {
       var error = "Type " + structFieldType.getName() + " not defined.";
       throw new RuntimeException(Helper.getErrorPrefix(line, col) + error);
@@ -796,7 +802,8 @@ public class ContextAnalysis extends KlangBaseVisitor<Node> {
     currentDeclaredReturnType = returnType;
     currentFunctionDefinitionName = name;
 
-    if (!returnType.isPrimitiveType() && !structDefs.containsKey(returnType.getName()) && !enumDefs.containsKey(returnType.getName())) {
+    var typeNotDefined = !returnType.isPrimitiveType() && !structDefs.containsKey(returnType.getName()) && !enumDefs.containsKey(returnType.getName());
+    if (!returnType.equals(Type.getVoidType()) && typeNotDefined) {
       var line = ctx.returnType.start.getLine();
       var col = ctx.returnType.start.getCharPositionInLine();
       var error = "Type " + returnType.getName() + " not defined.";
@@ -824,7 +831,7 @@ public class ContextAnalysis extends KlangBaseVisitor<Node> {
 
     // Visit the block, make sure that a return value is guaranteed
     var block = visit(ctx.braced_block());
-    if (block.type == null) {
+    if (block.type == null && !returnType.equals(Type.getVoidType())) {
       var line = ctx.braced_block().start.getLine();
       var col = ctx.braced_block().start.getCharPositionInLine();
       var error = "Function " + name + " has to return something of type " + returnType.getName() + ".";

src/test/java/VoidTest.java

@@ -0,0 +1,101 @@
+import de.hsrm.compiler.Klang.ContextAnalysis;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class VoidTest {
+
+    @Test
+    void shouldNotThrowIfVoidIsUsedAsReturnType() {
+        // given
+        var tree = Helper.prepareParser("function foo(): void { let a: int = 0; } foo();");
+        var ctxAnal = new ContextAnalysis(Helper.getFuncs(tree), Helper.getStructs(tree), Helper.getEnums(tree));
+
+        // when / then
+        assertDoesNotThrow(() -> ctxAnal.visit(tree));
+    }
+
+    @Test
+    void shouldNotThrowIfVoidFunctionIsCalled() {
+        // given
+        var tree = Helper.prepareParser("""
+                function foo(): void {
+                    let a: int = 0;
+                }
+                function bar(): int {
+                    foo();
+                    return 1;
+                }
+                bar();
+                """);
+        var ctxAnal = new ContextAnalysis(Helper.getFuncs(tree), Helper.getStructs(tree), Helper.getEnums(tree));
+
+        // when / then
+        assertDoesNotThrow(() -> ctxAnal.visit(tree));
+    }
+
+    @Test
+    void shouldThrowIfVoidFunctionIsAssignedToVariable() {
+        // given
+        var tree = Helper.prepareParser("""
+                function foo(): void {
+                    let a: int = 0;
+                }
+                function bar(): int {
+                    let a: int = foo();
+                    return 1;
+                }
+                bar();
+                """);
+        var ctxAnal = new ContextAnalysis(Helper.getFuncs(tree), Helper.getStructs(tree), Helper.getEnums(tree));
+
+        // when / then
+        var e = assertThrows(RuntimeException.class, () -> ctxAnal.visit(tree));
+        assertEquals("Error in line 5:4 Type mismatch: cannot combine int and void", e.getMessage());
+    }
+
+    @Test
+    void shouldThrowIfValueIsReturnedFromVoidFunction() {
+        // given
+        var tree = Helper.prepareParser("function foo(): void { return 1; } foo();");
+        var ctxAnal = new ContextAnalysis(Helper.getFuncs(tree), Helper.getStructs(tree), Helper.getEnums(tree));
+
+        // when / then
+        var e = assertThrows(RuntimeException.class, () -> ctxAnal.visit(tree));
+        assertEquals("Error in line 1:23 Cannot return an expression from a void function.", e.getMessage());
+    }
+
+    @Test
+    void shouldThrowIfVoidIsUsedAsParameterType() {
+        // given
+        var tree = Helper.prepareParser("function foo(a: void): int { return 1; } foo();");
+        var ctxAnal = new ContextAnalysis(Helper.getFuncs(tree), Helper.getStructs(tree), Helper.getEnums(tree));
+
+        // when / then
+        var e = assertThrows(RuntimeException.class, () -> ctxAnal.visit(tree));
+        assertEquals("Error in line 1:13 Type void cannot be used to declare a parameter.", e.getMessage());
+    }
+
+    @Test
+    void shouldThrowIfVoidIsUsedAsVariableType() {
+        // given
+        var tree = Helper.prepareParser("function foo(): int { let a: void; return 1; } foo();");
+        var ctxAnal = new ContextAnalysis(Helper.getFuncs(tree), Helper.getStructs(tree), Helper.getEnums(tree));
+
+        // when / then
+        var e = assertThrows(RuntimeException.class, () -> ctxAnal.visit(tree));
+        assertEquals("Error in line 1:22 Type void can not be used to declare variables.", e.getMessage());
+    }
+
+    @Test
+    void shouldThrowIfVoidIsUsedAsStructFieldType() {
+        // given
+        var tree = Helper.prepareParser("struct bar { a: void; } function foo(): int { return 1; } foo();");
+        var ctxAnal = new ContextAnalysis(Helper.getFuncs(tree), Helper.getStructs(tree), Helper.getEnums(tree));
+
+        // when / then
+        var e = assertThrows(RuntimeException.class, () -> ctxAnal.visit(tree));
+        assertEquals("Error in line 1:13 Type void can not be used as a struct field type.", e.getMessage());
+    }
+
+}