Preserve terminal nodes

pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/impl/antlr4/AbstractAntlrInnerNode.java

@@ -0,0 +1,38 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.ast.impl.antlr4;
+
+/**
+ *
+ */
+public abstract class AbstractAntlrInnerNode<T extends AntlrParseTreeBase, N extends AntlrNode<N>>
+    extends AbstractAntlrNode<T, N> {
+
+    protected AbstractAntlrInnerNode(T parseTree) {
+        super(parseTree);
+    }
+
+    @Override
+    public int getBeginLine() {
+        return getParseTree().start.getLine(); // This goes from 1 to n
+    }
+
+    @Override
+    public int getEndLine() {
+        // FIXME this is not the end line if the stop token spans several lines
+        return getParseTree().stop.getLine();
+    }
+
+    @Override
+    public int getBeginColumn() {
+        return AntlrUtils.getBeginColumn(getParseTree().start);
+    }
+
+    @Override
+    public int getEndColumn() {
+        return AntlrUtils.getEndColumn(getParseTree().stop);
+    }
+
+}

pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/impl/antlr4/AbstractAntlrNode.java

@@ -5,16 +5,12 @@
 package net.sourceforge.pmd.lang.ast.impl.antlr4;
 
 import net.sourceforge.pmd.lang.ast.impl.AbstractNode;
-import net.sourceforge.pmd.lang.ast.impl.GenericNode;
 
 /**
  *
  */
-public abstract class AbstractAntlrNode<
-    B extends AbstractAntlrNode<B, ?, N>,
-    T extends AntlrParseTreeBase,
-    N extends GenericNode<N>
-    > extends AbstractNode<B, N> {
+public abstract class AbstractAntlrNode<T, N extends AntlrNode<N>>
+    extends AbstractNode<AbstractAntlrNode<?, N>, N> implements AntlrNode<N> {
 
     private final T parseTree;
 
@@ -22,14 +18,11 @@ public abstract class AbstractAntlrNode<
         this.parseTree = parseTree;
     }
 
-
     @Override
-    protected void addChild(B child, int index) {
+    protected void addChild(AbstractAntlrNode<?, N> child, int index) {
         super.addChild(child, index);
     }
 
-    public abstract <P, R> R acceptVisitor(AntlrTreeVisitor<P, R, ?> visitor, P data);
-
     public T getParseTree() {
         return parseTree;
     }
@@ -41,25 +34,5 @@ public abstract class AbstractAntlrNode<
             '}';
     }
 
-    @Override
-    public int getBeginLine() {
-        return parseTree.start.getLine(); // This goes from 1 to n
-    }
-
-    @Override
-    public int getEndLine() {
-        // FIXME this is not the end line if the stop token spans several lines
-        return parseTree.stop.getLine();
-    }
-
-    @Override
-    public int getBeginColumn() {
-        return AntlrUtils.getBeginColumn(parseTree.start);
-    }
-
-    @Override
-    public int getEndColumn() {
-        return AntlrUtils.getEndColumn(parseTree.stop);
-    }
 
 }

pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/impl/antlr4/AbstractAntlrTerminalNode.java

@@ -0,0 +1,40 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.ast.impl.antlr4;
+
+import org.antlr.v4.runtime.tree.TerminalNode;
+
+/**
+ *
+ */
+public abstract class AbstractAntlrTerminalNode<N extends AntlrNode<N>>
+    extends AbstractAntlrNode<TerminalNode, N> {
+
+    protected AbstractAntlrTerminalNode(TerminalNode parseTree) {
+        super(parseTree);
+    }
+
+    @Override
+    public int getBeginLine() {
+        return getParseTree().getSymbol().getLine(); // This goes from 1 to n
+    }
+
+    @Override
+    public int getEndLine() {
+        // FIXME this is not the end line if the stop token spans several lines
+        return getParseTree().getSymbol().getLine();
+    }
+
+    @Override
+    public int getBeginColumn() {
+        return AntlrUtils.getBeginColumn(getParseTree().getSymbol());
+    }
+
+    @Override
+    public int getEndColumn() {
+        return AntlrUtils.getEndColumn(getParseTree().getSymbol());
+    }
+
+}

pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/impl/antlr4/AntlrBaseParser.java

@@ -15,7 +15,6 @@ import net.sourceforge.pmd.lang.Parser;
 import net.sourceforge.pmd.lang.ParserOptions;
 import net.sourceforge.pmd.lang.ast.ParseException;
 import net.sourceforge.pmd.lang.ast.RootNode;
-import net.sourceforge.pmd.lang.ast.impl.GenericNode;
 
 /**
  * Generic Antlr parser adapter for all Antlr parsers. This wraps a parser
@@ -25,9 +24,8 @@ import net.sourceforge.pmd.lang.ast.impl.GenericNode;
  * @param <R> Type of the root node
  */
 public abstract class AntlrBaseParser<
-    N extends GenericNode<N>,
-    B extends AbstractAntlrNode<B, ?, N>,
-    R extends AbstractAntlrNode<B, ?, N> & RootNode
+    N extends AntlrNode<N>,
+    R extends AbstractAntlrNode<?, N> & RootNode
     > implements Parser {
 
     protected final ParserOptions parserOptions;

pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/impl/antlr4/AntlrBaseRule.java

@@ -27,7 +27,7 @@ public abstract class AntlrBaseRule extends AbstractRule {
         for (Node node : nodes) {
             assert node instanceof AbstractAntlrNode : "Incorrect node type " + node + " passed to " + this;
 
-            ((AbstractAntlrNode<?, ?, ?>) node).acceptVisitor(visitor, ctx);
+            ((AbstractAntlrNode<?, ?>) node).acceptVisitor(visitor, ctx);
         }
     }
 

pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/impl/antlr4/AntlrNode.java

@@ -0,0 +1,15 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.ast.impl.antlr4;
+
+import net.sourceforge.pmd.lang.ast.impl.GenericNode;
+
+/**
+ *
+ */
+public interface AntlrNode<N extends GenericNode<N>> extends GenericNode<N> {
+
+    <P, R> R acceptVisitor(AntlrTreeVisitor<P, R, ?> visitor, P data);
+}

pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/impl/antlr4/AntlrParseTreeBase.java

@@ -12,7 +12,7 @@ import org.antlr.v4.runtime.ParserRuleContext;
  */
 public abstract class AntlrParseTreeBase extends ParserRuleContext {
 
-    AbstractAntlrNode<?, ?, ?> pmdNode;
+    AntlrNode<?> pmdNode;
 
 
     protected AntlrParseTreeBase() {

pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/impl/antlr4/AntlrTreeBuilderListener.java

@@ -16,7 +16,7 @@ import org.antlr.v4.runtime.tree.TerminalNode;
 /**
  * Don't extend me, compose me.
  */
-public class AntlrTreeBuilderState<B extends AbstractAntlrNode<B, ?, ?>> implements ParseTreeListener {
+public class AntlrTreeBuilderListener<B extends AbstractAntlrNode<?, N>, N extends AntlrNode<N>> implements ParseTreeListener {
 
 
     private final ParseTreeVisitor<B> nodeFactory;
@@ -26,7 +26,7 @@ public class AntlrTreeBuilderState<B extends AbstractAntlrNode<B, ?, ?>> impleme
     private int sp = 0;
     private int mk = 0;
 
-    public AntlrTreeBuilderState(ParseTreeVisitor<B> nodeFactory) {
+    public AntlrTreeBuilderListener(ParseTreeVisitor<B> nodeFactory) {
         this.nodeFactory = nodeFactory;
     }
 
@@ -36,7 +36,8 @@ public class AntlrTreeBuilderState<B extends AbstractAntlrNode<B, ?, ?>> impleme
 
     @Override
     public void visitTerminal(TerminalNode node) {
-
+        B toPush = nodeFactory.visitTerminal(node);
+        pushNode(toPush);
     }
 
     @Override
@@ -46,6 +47,10 @@ public class AntlrTreeBuilderState<B extends AbstractAntlrNode<B, ?, ?>> impleme
 
     @Override
     public void enterEveryRule(ParserRuleContext ctx) {
+        enterNode();
+    }
+
+    private void enterNode() {
         marks.push(mk);
         mk = sp;
     }
@@ -55,6 +60,7 @@ public class AntlrTreeBuilderState<B extends AbstractAntlrNode<B, ?, ?>> impleme
         B newNode = nodeFactory.visit(ctx);
         ((AntlrParseTreeBase) ctx).pmdNode = newNode;
 
+
         int arity = nodeArity();
         mk = marks.pop();
         while (arity-- > 0) {

pmd-swift/src/main/antlr4/net/sourceforge/pmd/lang/swift/ast/SwiftTree.g4

@@ -38,7 +38,6 @@ import net.sourceforge.pmd.lang.ast.impl.antlr4.*;
 }
 
 
-
 @parser::members {
 
     public static final AntlrNameDictionary DICO = new AntlrNameDictionary(VOCABULARY, ruleNames);

pmd-swift/src/main/java/net/sourceforge/pmd/lang/swift/SwiftHandler.java

@@ -7,12 +7,12 @@ package net.sourceforge.pmd.lang.swift;
 import net.sourceforge.pmd.lang.AbstractPmdLanguageVersionHandler;
 import net.sourceforge.pmd.lang.Parser;
 import net.sourceforge.pmd.lang.ParserOptions;
-import net.sourceforge.pmd.lang.swift.ast.SwiftParserAdapter;
+import net.sourceforge.pmd.lang.swift.ast.SwiftParser;
 
 public class SwiftHandler extends AbstractPmdLanguageVersionHandler {
 
     @Override
     public Parser getParser(final ParserOptions parserOptions) {
-        return new SwiftParserAdapter(parserOptions);
+        return new SwiftParser(parserOptions);
     }
 }

pmd-swift/src/main/java/net/sourceforge/pmd/lang/swift/ast/SwIdentifier.java

@@ -0,0 +1,23 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.swift.ast;
+
+import net.sourceforge.pmd.lang.swift.ast.SwiftTreeParser.IdentifierContext;
+
+public final class SwIdentifier extends SwiftInnerNode<IdentifierContext> {
+
+    SwIdentifier(IdentifierContext parseTreeNode) {
+        super(parseTreeNode);
+    }
+
+    public String getName() {
+        return getParseTree().getText(); // single token
+    }
+
+    @Override
+    public <P, R> R acceptVisitor(SwiftVisitor<P, R> visitor, P data) {
+        return visitor.visitIdent(this, data);
+    }
+}

pmd-swift/src/main/java/net/sourceforge/pmd/lang/swift/ast/SwRootNode.java

@@ -7,9 +7,9 @@ package net.sourceforge.pmd.lang.swift.ast;
 import net.sourceforge.pmd.lang.ast.RootNode;
 import net.sourceforge.pmd.lang.swift.ast.SwiftTreeParser.TopLevelContext;
 
-public final class SwiftRootNode extends SwiftNodeImpl<TopLevelContext> implements RootNode {
+public final class SwRootNode extends SwiftInnerNode<TopLevelContext> implements RootNode {
 
-    public SwiftRootNode(TopLevelContext parseTreeNode) {
+    SwRootNode(TopLevelContext parseTreeNode) {
         super(parseTreeNode);
     }
 

pmd-swift/src/main/java/net/sourceforge/pmd/lang/swift/ast/SwiftInnerNode.java

@@ -4,32 +4,22 @@
 
 package net.sourceforge.pmd.lang.swift.ast;
 
+import net.sourceforge.pmd.lang.ast.impl.antlr4.AbstractAntlrInnerNode;
 import net.sourceforge.pmd.lang.ast.impl.antlr4.AbstractAntlrNode;
 import net.sourceforge.pmd.lang.ast.impl.antlr4.AntlrParseTreeBase;
-import net.sourceforge.pmd.lang.ast.impl.antlr4.AntlrTreeVisitor;
 
-/**
- *
- */
-public class SwiftNodeImpl<T extends AntlrParseTreeBase>
-    extends AbstractAntlrNode<SwiftNodeImpl<?>, T, SwiftNode<?>>
+public class SwiftInnerNode<T extends AntlrParseTreeBase>
+    extends AbstractAntlrInnerNode<T, SwiftNode<?>>
     implements SwiftNode<T> {
 
-    SwiftNodeImpl(T parseTreeNode) {
+    SwiftInnerNode(T parseTreeNode) {
         super(parseTreeNode);
     }
 
-    @Override
-    protected void addChild(SwiftNodeImpl<?> child, int index) {
-        super.addChild(child, index);
-    }
 
     @Override
-    public final <P, R> R acceptVisitor(AntlrTreeVisitor<P, R, ?> visitor, P data) {
-        if (visitor instanceof SwiftVisitor) {
-            return acceptVisitor((SwiftVisitor<P, R>) visitor, data);
-        }
-        throw new IllegalArgumentException("Cannot accept visitor " + visitor);
+    protected void addChild(AbstractAntlrNode<?, SwiftNode<?>> child, int index) {
+        super.addChild(child, index);
     }
 
     @Override

pmd-swift/src/main/java/net/sourceforge/pmd/lang/swift/ast/SwiftNode.java

@@ -4,19 +4,27 @@
 
 package net.sourceforge.pmd.lang.swift.ast;
 
-import net.sourceforge.pmd.lang.ast.impl.GenericNode;
-import net.sourceforge.pmd.lang.ast.impl.antlr4.AntlrParseTreeBase;
+import net.sourceforge.pmd.lang.ast.impl.antlr4.AntlrNode;
+import net.sourceforge.pmd.lang.ast.impl.antlr4.AntlrTreeVisitor;
 
 
 /**
  * Supertype of all swift nodes.
  */
-public interface SwiftNode<T extends AntlrParseTreeBase> extends GenericNode<SwiftNode<?>> {
-
+public interface SwiftNode<T> extends AntlrNode<SwiftNode<?>> {
 
     T getParseTree();
 
 
     <P, R> R acceptVisitor(SwiftVisitor<P, R> visitor, P data);
 
+
+    @Override
+    default <P, R> R acceptVisitor(AntlrTreeVisitor<P, R, ?> visitor, P data) {
+        if (visitor instanceof SwiftVisitor) {
+            return acceptVisitor((SwiftVisitor<P, R>) visitor, data);
+        }
+        throw new IllegalArgumentException("Cannot accept visitor " + visitor);
+    }
+
 }

pmd-swift/src/main/java/net/sourceforge/pmd/lang/swift/ast/SwiftNodeFactory.java

@@ -5,12 +5,15 @@
 package net.sourceforge.pmd.lang.swift.ast;
 
 import org.antlr.v4.runtime.tree.RuleNode;
+import org.antlr.v4.runtime.tree.TerminalNode;
 
+import net.sourceforge.pmd.lang.ast.impl.antlr4.AbstractAntlrNode;
 import net.sourceforge.pmd.lang.ast.impl.antlr4.AntlrParseTreeBase;
+import net.sourceforge.pmd.lang.swift.ast.SwiftTreeParser.IdentifierContext;
 import net.sourceforge.pmd.lang.swift.ast.SwiftTreeParser.TopLevelContext;
 
 
-final class SwiftNodeFactory extends SwiftTreeBaseVisitor<SwiftNodeImpl<?>> {
+final class SwiftNodeFactory extends SwiftTreeBaseVisitor<AbstractAntlrNode<?, SwiftNode<?>>> {
 
     static final SwiftNodeFactory INSTANCE = new SwiftNodeFactory();
 
@@ -19,13 +22,23 @@ final class SwiftNodeFactory extends SwiftTreeBaseVisitor<SwiftNodeImpl<?>> {
     }
 
     @Override
-    public SwiftNodeImpl<?> visitTopLevel(TopLevelContext ctx) {
-        return new SwiftRootNode(ctx);
+    public SwiftTerminal visitTerminal(TerminalNode node) {
+        return new SwiftTerminal(node);
     }
 
     @Override
-    public SwiftNodeImpl<?> visitChildren(RuleNode node) {
+    public SwiftInnerNode<?> visitIdentifier(IdentifierContext ctx) {
+        return new SwIdentifier(ctx);
+    }
+
+    @Override
+    public SwiftInnerNode<?> visitTopLevel(TopLevelContext ctx) {
+        return new SwRootNode(ctx);
+    }
+
+    @Override
+    public SwiftInnerNode<?> visitChildren(RuleNode node) {
         // default visit
-        return new SwiftNodeImpl<>((AntlrParseTreeBase) node);
+        return new SwiftInnerNode<>((AntlrParseTreeBase) node);
     }
 }

pmd-swift/src/main/java/net/sourceforge/pmd/lang/swift/ast/SwiftParser.java

@@ -10,24 +10,24 @@ import org.antlr.v4.runtime.Lexer;
 
 import net.sourceforge.pmd.lang.ParserOptions;
 import net.sourceforge.pmd.lang.ast.impl.antlr4.AntlrBaseParser;
-import net.sourceforge.pmd.lang.ast.impl.antlr4.AntlrTreeBuilderState;
+import net.sourceforge.pmd.lang.ast.impl.antlr4.AntlrTreeBuilderListener;
 
 /**
  * Adapter for the SwiftParser.
  */
-public final class SwiftParserAdapter extends AntlrBaseParser<SwiftNode<?>, SwiftNodeImpl<?>, SwiftRootNode> {
+public final class SwiftParser extends AntlrBaseParser<SwiftNode<?>, SwRootNode> {
 
-    public SwiftParserAdapter(final ParserOptions parserOptions) {
+    public SwiftParser(final ParserOptions parserOptions) {
         super(parserOptions);
     }
 
     @Override
-    protected SwiftRootNode parse(final Lexer lexer) {
+    protected SwRootNode parse(final Lexer lexer) {
         SwiftTreeParser parser = new SwiftTreeParser(new CommonTokenStream(lexer));
-        AntlrTreeBuilderState<?> listener = new AntlrTreeBuilderState<>(SwiftNodeFactory.INSTANCE);
+        AntlrTreeBuilderListener<?, ?> listener = new AntlrTreeBuilderListener<>(SwiftNodeFactory.INSTANCE);
         parser.addParseListener(listener);
         parser.topLevel();
-        return (SwiftRootNode) listener.top();
+        return (SwRootNode) listener.top();
     }
 
     @Override

pmd-swift/src/main/java/net/sourceforge/pmd/lang/swift/ast/SwiftTerminal.java

@@ -0,0 +1,27 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.swift.ast;
+
+import org.antlr.v4.runtime.tree.TerminalNode;
+
+import net.sourceforge.pmd.lang.ast.impl.antlr4.AbstractAntlrTerminalNode;
+
+public final class SwiftTerminal extends AbstractAntlrTerminalNode<SwiftNode<?>> implements SwiftNode<TerminalNode> {
+
+    SwiftTerminal(TerminalNode parseTreeNode) {
+        super(parseTreeNode);
+    }
+
+
+    @Override
+    public String getXPathNodeName() {
+        return SwiftTreeParser.DICO.getXPathNameOfToken(getParseTree().getSymbol().getType());
+    }
+
+    @Override
+    public <P, R> R acceptVisitor(SwiftVisitor<P, R> visitor, P data) {
+        return visitor.visitTerminal(this, data);
+    }
+}

pmd-swift/src/main/java/net/sourceforge/pmd/lang/swift/ast/SwiftVisitor.java

@@ -11,10 +11,24 @@ import net.sourceforge.pmd.lang.ast.impl.antlr4.AntlrTreeVisitor;
  */
 public interface SwiftVisitor<P, R> extends AntlrTreeVisitor<P, R, SwiftNode<?>> {
 
-
-    default R visitRoot(SwiftRootNode node, P data) {
+    default R visitTerminal(SwiftTerminal node, P data) {
         return visitAnyNode(node, data);
     }
 
 
+    default R visitInnerNode(SwiftInnerNode<?> node, P data) {
+        return visitAnyNode(node, data);
+    }
+
+
+    default R visitRoot(SwRootNode node, P data) {
+        return visitInnerNode(node, data);
+    }
+
+
+    default R visitIdent(SwIdentifier node, P data) {
+        return visitInnerNode(node, data);
+    }
+
+
 }

pmd-swift/src/main/java/net/sourceforge/pmd/lang/swift/rule/bestpractices/UnavailableFunctionRule.java

@@ -8,6 +8,7 @@ import java.util.List;
 
 import net.sourceforge.pmd.RuleContext;
 import net.sourceforge.pmd.lang.swift.AbstractSwiftRule;
+import net.sourceforge.pmd.lang.swift.ast.SwiftInnerNode;
 import net.sourceforge.pmd.lang.swift.ast.SwiftNode;
 import net.sourceforge.pmd.lang.swift.ast.SwiftTreeParser;
 import net.sourceforge.pmd.lang.swift.ast.SwiftTreeParser.AttributeContext;
@@ -34,8 +35,13 @@ public class UnavailableFunctionRule extends AbstractSwiftRule {
         return new SwiftVisitor<RuleContext, Void>() {
 
             @Override
-            @SuppressWarnings("unchecked")
             public Void visitAnyNode(SwiftNode<?> swiftNode, RuleContext data) {
+                return null;
+            }
+
+            @Override
+            @SuppressWarnings("unchecked")
+            public Void visitInnerNode(SwiftInnerNode<?> swiftNode, RuleContext data) {
                 switch (swiftNode.getParseTree().getRuleIndex()) {
                 case SwiftTreeParser.RULE_functionDeclaration:
                     return visitFunctionDeclaration((SwiftNode<FunctionDeclarationContext>) swiftNode, data);

pmd-swift/src/main/resources/category/swift/bestpractices.xml

@@ -26,9 +26,9 @@ Rules which enforce generally accepted best practices.
             <property name="version" value="2.0" />
             <property name="xpath">
                 <value>
-                    //VariableDeclarationHead/Attributes/Attribute[T-at-symbol and AttributeName/*/T-Identifier/@Text = "IBOutlet"]
+                    //VariableDeclarationHead/Attributes/Attribute[AttributeName/Identifier[@Name = "IBOutlet"]]
                     |
-                    //FunctionHead/Attributes/Attribute[T-at-symbol and AttributeName/*/T-Identifier/@Text = "IBAction"]
+                    //FunctionHead/Attributes/Attribute[AttributeName/Identifier[@Name = "IBAction"]]
                 </value>
             </property>
         </properties>

pmd-swift/src/main/resources/category/swift/errorprone.xml

@@ -25,7 +25,7 @@
             <property name="xpath">
                 <value>
                     <![CDATA[
-//TypeCastingOperator[T-bang]
+//TypeCastingOperator[T-as and T-bang]
 ]]>
                 </value>
             </property>

pmd-swift/src/test/java/net/sourceforge/pmd/lang/swift/ast/SwiftParserTests.java

@@ -16,4 +16,9 @@ public class SwiftParserTests extends BaseSwiftTreeDumpTest {
         doTest("Simple");
     }
 
+    @Test
+    public void testBtree() {
+        doTest("BTree");
+    }
+
 }

pmd-swift/src/test/java/net/sourceforge/pmd/lang/swift/ast/SwiftParsingHelper.java

@@ -12,13 +12,13 @@ import net.sourceforge.pmd.lang.swift.SwiftLanguageModule;
 /**
  *
  */
-public class SwiftParsingHelper extends BaseParsingHelper<SwiftParsingHelper, SwiftRootNode> {
+public class SwiftParsingHelper extends BaseParsingHelper<SwiftParsingHelper, SwRootNode> {
 
     public static final SwiftParsingHelper DEFAULT = new SwiftParsingHelper(Params.getDefaultNoProcess());
 
 
     public SwiftParsingHelper(@NotNull Params params) {
-        super(SwiftLanguageModule.NAME, SwiftRootNode.class, params);
+        super(SwiftLanguageModule.NAME, SwRootNode.class, params);
     }
 
     @NotNull