Added @NonNull on parameters feature (issue 514),

including docs and changelog.

7 files changed, 365 insertions, 20 deletions

diff --git a/src/core/lombok/NonNull.java b/src/core/lombok/NonNull.java
index 5f5d8ed2..96813170 100644
--- a/src/core/lombok/NonNull.java
+++ b/src/core/lombok/NonNull.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2009 The Project Lombok Authors.
+ * Copyright (C) 2009-2013 The Project Lombok Authors.
  * 
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -28,12 +28,14 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 /**
- * Lombok is smart enough to translate any annotation named {@code @NonNull} in any casing and
- * with any package name to the return type of generated getters and the parameter of generated setters and constructors,
- * as well as generate the appropriate null checks in the setter and constructor.
- * 
- * You can use this annotation for the purpose, though you can also use JSR305's annotation, findbugs's, pmd's, or IDEA's, or just
- * about anyone elses. As long as it is named {@code @NonNull}.
+ * If put on a parameter, lombok will insert a null-check at the start of the method / constructor's body, throwing a
+ * {@code NullPointerException} with the parameter's name as message. If put on a field, any generated method assigning
+ * a value to this field will also produce these nullchecks.
+ * <p>
+ * Note that any annotation named {@code NonNull} with any casing and any package will result in nullchecks produced for
+ * generated methods (and the annotation will be copied to the getter return type and any parameters of generated methods),
+ * but <em>only</em> this annotation, if present on a parameter, will result in a null check inserted into your otherwise
+ * handwritten method.
  * 
  * WARNING: If the java community ever does decide on supporting a single {@code @NonNull} annotation (for example via JSR305), then
  * this annotation will <strong>be deleted</strong> from the lombok package. If the need to update an import statement scares
diff --git a/src/core/lombok/eclipse/handlers/EclipseHandlerUtil.java b/src/core/lombok/eclipse/handlers/EclipseHandlerUtil.java
index 7703336f..dc99dabf 100644
--- a/src/core/lombok/eclipse/handlers/EclipseHandlerUtil.java
+++ b/src/core/lombok/eclipse/handlers/EclipseHandlerUtil.java
@@ -61,6 +61,7 @@ import org.eclipse.jdt.internal.compiler.ast.Annotation;
 import org.eclipse.jdt.internal.compiler.ast.ArrayInitializer;
 import org.eclipse.jdt.internal.compiler.ast.ArrayQualifiedTypeReference;
 import org.eclipse.jdt.internal.compiler.ast.ArrayTypeReference;
+import org.eclipse.jdt.internal.compiler.ast.Block;
 import org.eclipse.jdt.internal.compiler.ast.CastExpression;
 import org.eclipse.jdt.internal.compiler.ast.CompilationUnitDeclaration;
 import org.eclipse.jdt.internal.compiler.ast.ConstructorDeclaration;
@@ -1334,7 +1335,11 @@ public class EclipseHandlerUtil {
 		EqualExpression equalExpression = new EqualExpression(varName, nullLiteral, OperatorIds.EQUAL_EQUAL);
 		equalExpression.sourceStart = pS; equalExpression.statementEnd = equalExpression.sourceEnd = pE;
 		setGeneratedBy(equalExpression, source);
-		IfStatement ifStatement = new IfStatement(equalExpression, throwStatement, 0, 0);
+		Block throwBlock = new Block(0);
+		throwBlock.statements = new Statement[] {throwStatement};
+		throwBlock.sourceStart = pS; throwBlock.sourceEnd = pE;
+		setGeneratedBy(throwBlock, source);
+		IfStatement ifStatement = new IfStatement(equalExpression, throwBlock, 0, 0);
 		setGeneratedBy(ifStatement, source);
 		return ifStatement;
 	}
diff --git a/src/core/lombok/eclipse/handlers/NonNullHandler.java b/src/core/lombok/eclipse/handlers/NonNullHandler.java
new file mode 100644
index 00000000..5c58069c
--- /dev/null
+++ b/src/core/lombok/eclipse/handlers/NonNullHandler.java
@@ -0,0 +1,147 @@
+/*
+ * Copyright (C) 2013 The Project Lombok Authors.
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package lombok.eclipse.handlers;
+
+import java.util.Arrays;
+
+import org.eclipse.jdt.internal.compiler.ast.ASTNode;
+import org.eclipse.jdt.internal.compiler.ast.AbstractMethodDeclaration;
+import org.eclipse.jdt.internal.compiler.ast.AbstractVariableDeclaration;
+import org.eclipse.jdt.internal.compiler.ast.Annotation;
+import org.eclipse.jdt.internal.compiler.ast.Argument;
+import org.eclipse.jdt.internal.compiler.ast.Block;
+import org.eclipse.jdt.internal.compiler.ast.EqualExpression;
+import org.eclipse.jdt.internal.compiler.ast.Expression;
+import org.eclipse.jdt.internal.compiler.ast.IfStatement;
+import org.eclipse.jdt.internal.compiler.ast.NullLiteral;
+import org.eclipse.jdt.internal.compiler.ast.OperatorIds;
+import org.eclipse.jdt.internal.compiler.ast.SingleNameReference;
+import org.eclipse.jdt.internal.compiler.ast.Statement;
+import org.eclipse.jdt.internal.compiler.ast.ThrowStatement;
+import org.mangosdk.spi.ProviderFor;
+
+import lombok.NonNull;
+import lombok.core.AST.Kind;
+import lombok.core.AnnotationValues;
+import lombok.eclipse.DeferUntilPostDiet;
+import lombok.eclipse.EclipseAnnotationHandler;
+import lombok.eclipse.EclipseNode;
+
+import static lombok.eclipse.Eclipse.*;
+import static lombok.eclipse.handlers.EclipseHandlerUtil.*;
+
+@DeferUntilPostDiet
+@ProviderFor(EclipseAnnotationHandler.class)
+public class NonNullHandler extends EclipseAnnotationHandler<NonNull> {
+	@Override public void handle(AnnotationValues<NonNull> annotation, Annotation ast, EclipseNode annotationNode) {
+		if (annotationNode.up().getKind() == Kind.FIELD) {
+			// This is meaningless unless the field is used to generate a method (@Setter, @RequiredArgsConstructor, etc),
+			// but in that case those handlers will take care of it. However, we DO check if the annotation is applied to
+			// a primitive, because those handlers trigger on any annotation named @NonNull and we only want the warning
+			// behaviour on _OUR_ 'lombok.NonNull'.
+			
+			try {
+				if (isPrimitive(((AbstractVariableDeclaration) annotationNode.up().get()).type)) {
+					annotationNode.addWarning("@NonNull is meaningless on a primitive.");
+				}
+			} catch (Exception ignore) {}
+			
+			return;
+		}
+		
+		if (annotationNode.up().getKind() != Kind.ARGUMENT) return;
+		
+		Argument arg;
+		AbstractMethodDeclaration declaration;
+		
+		try {
+			arg = (Argument) annotationNode.up().get();
+			declaration = (AbstractMethodDeclaration) annotationNode.up().up().get();
+		} catch (Exception e) {
+			return;
+		}
+		
+		if (isGenerated(declaration)) return;
+		
+		// Possibly, if 'declaration instanceof ConstructorDeclaration', fetch declaration.constructorCall, search it for any references to our parameter,
+		// and if they exist, create a new method in the class: 'private static <T> T lombok$nullCheck(T expr, String msg) {if (expr == null) throw NPE; return expr;}' and
+		// wrap all references to it in the super/this to a call to this method.
+		
+		Statement nullCheck = generateNullCheck(arg, ast);
+		
+		if (nullCheck == null) {
+			// @NonNull applied to a primitive. Kinda pointless. Let's generate a warning.
+			annotationNode.addWarning("@NonNull is meaningless on a primitive.");
+			return;
+		}
+		
+		if (declaration.statements == null) {
+			declaration.statements = new Statement[] {nullCheck};
+		} else {
+			char[] expectedName = arg.name;
+			for (Statement stat : declaration.statements) {
+				char[] varNameOfNullCheck = returnVarNameIfNullCheck(stat);
+				if (varNameOfNullCheck == null) break;
+				if (Arrays.equals(expectedName, varNameOfNullCheck)) return;
+			}
+			
+			Statement[] newStatements = new Statement[declaration.statements.length + 1];
+			int skipOver = 0;
+			for (Statement stat : declaration.statements) {
+				if (isGenerated(stat)) skipOver++;
+				else break;
+			}
+			System.arraycopy(declaration.statements, 0, newStatements, 0, skipOver);
+			System.arraycopy(declaration.statements, skipOver, newStatements, skipOver + 1, declaration.statements.length - skipOver);
+			newStatements[skipOver] = nullCheck;
+			declaration.statements = newStatements;
+		}
+		annotationNode.up().up().rebuild();
+	}
+	
+	private char[] returnVarNameIfNullCheck(Statement stat) {
+		if (!(stat instanceof IfStatement)) return null;
+		
+		/* Check that the if's statement is a throw statement, possibly in a block. */ {
+			Statement then = ((IfStatement) stat).thenStatement;
+			if (then instanceof Block) {
+				Statement[] blockStatements = ((Block) then).statements;
+				if (blockStatements == null || blockStatements.length == 0) return null;
+				then = blockStatements[0];
+			}
+			
+			if (!(then instanceof ThrowStatement)) return null;
+		}
+		
+		/* Check that the if's conditional is like 'x == null'. Return from this method (don't generate
+		   a nullcheck) if 'x' is equal to our own variable's name: There's already a nullcheck here. */ {
+			Expression cond = ((IfStatement) stat).condition;
+			if (!(cond instanceof EqualExpression)) return null;
+			EqualExpression bin = (EqualExpression) cond;
+			int operatorId = ((bin.bits & ASTNode.OperatorMASK) >> ASTNode.OperatorSHIFT);
+			if (operatorId != OperatorIds.EQUAL_EQUAL) return null;
+			if (!(bin.left instanceof SingleNameReference)) return null;
+			if (!(bin.right instanceof NullLiteral)) return null;
+			return ((SingleNameReference) bin.left).token;
+		}
+	}
+}
diff --git a/src/core/lombok/javac/handlers/HandleSneakyThrows.java b/src/core/lombok/javac/handlers/HandleSneakyThrows.java
index c2394fc8..c818f630 100644
--- a/src/core/lombok/javac/handlers/HandleSneakyThrows.java
+++ b/src/core/lombok/javac/handlers/HandleSneakyThrows.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2009-2011 The Project Lombok Authors.
+ * Copyright (C) 2009-2013 The Project Lombok Authors.
  * 
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -36,8 +36,6 @@ import org.mangosdk.spi.ProviderFor;
 
 import com.sun.tools.javac.code.Flags;
 import com.sun.tools.javac.tree.JCTree;
-import com.sun.tools.javac.tree.JCTree.JCExpressionStatement;
-import com.sun.tools.javac.tree.JCTree.JCMethodInvocation;
 import com.sun.tools.javac.tree.TreeMaker;
 import com.sun.tools.javac.tree.JCTree.JCAnnotation;
 import com.sun.tools.javac.tree.JCTree.JCBlock;
@@ -114,14 +112,6 @@ public class HandleSneakyThrows extends JavacAnnotationHandler<SneakyThrows> {
 		}
 	}
 
-	private boolean isConstructorCall(final JCStatement supect) {
-		if (!(supect instanceof JCExpressionStatement)) return false;
-		final JCExpression supectExpression = ((JCExpressionStatement) supect).expr;
-		if (!(supectExpression instanceof JCMethodInvocation)) return false;
-		final String methodName = ((JCMethodInvocation) supectExpression).meth.toString();
-		return "super".equals(methodName) || "this".equals(methodName);
-	}
-	
 	private JCStatement buildTryCatchBlock(JavacNode node, List<JCStatement> contents, String exception, JCTree source) {
 		TreeMaker maker = node.getTreeMaker();
 		
diff --git a/src/core/lombok/javac/handlers/JavacHandlerUtil.java b/src/core/lombok/javac/handlers/JavacHandlerUtil.java
index ef1a9f50..7cbaa5ac 100644
--- a/src/core/lombok/javac/handlers/JavacHandlerUtil.java
+++ b/src/core/lombok/javac/handlers/JavacHandlerUtil.java
@@ -50,9 +50,11 @@ import com.sun.tools.javac.tree.JCTree;
 import com.sun.tools.javac.tree.JCTree.JCAnnotation;
 import com.sun.tools.javac.tree.JCTree.JCArrayTypeTree;
 import com.sun.tools.javac.tree.JCTree.JCAssign;
+import com.sun.tools.javac.tree.JCTree.JCBlock;
 import com.sun.tools.javac.tree.JCTree.JCClassDecl;
 import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
 import com.sun.tools.javac.tree.JCTree.JCExpression;
+import com.sun.tools.javac.tree.JCTree.JCExpressionStatement;
 import com.sun.tools.javac.tree.JCTree.JCFieldAccess;
 import com.sun.tools.javac.tree.JCTree.JCIdent;
 import com.sun.tools.javac.tree.JCTree.JCImport;
@@ -121,6 +123,7 @@ public class JavacHandlerUtil {
 	}
 	
 	public static <T extends JCTree> T recursiveSetGeneratedBy(T node, JCTree source) {
+		if (node == null) return null;
 		setGeneratedBy(node, source);
 		node.accept(new MarkingScanner(source));
 		
@@ -543,6 +546,23 @@ public class JavacHandlerUtil {
 		return MemberExistsResult.NOT_EXISTS;
 	}
 	
+	public static boolean isConstructorCall(final JCStatement statement) {
+		if (!(statement instanceof JCExpressionStatement)) return false;
+		JCExpression expr = ((JCExpressionStatement) statement).expr;
+		if (!(expr instanceof JCMethodInvocation)) return false;
+		JCExpression invocation = ((JCMethodInvocation) expr).meth;
+		String name;
+		if (invocation instanceof JCFieldAccess) {
+			name = ((JCFieldAccess) invocation).name.toString();
+		} else if (invocation instanceof JCIdent) {
+			name = ((JCIdent) invocation).name.toString();
+		} else {
+			name = "";
+		}
+		
+		return "super".equals(name) || "this".equals(name);
+	}
+	
 	/**
 	 * Turns an {@code AccessLevel} instance into the flag bit used by javac.
 	 */
@@ -890,7 +910,8 @@ public class JavacHandlerUtil {
 		JCExpression npe = chainDots(variable, "java", "lang", "NullPointerException");
 		JCTree exception = treeMaker.NewClass(null, List.<JCExpression>nil(), npe, List.<JCExpression>of(treeMaker.Literal(fieldName.toString())), null);
 		JCStatement throwStatement = treeMaker.Throw(exception);
-		return treeMaker.If(treeMaker.Binary(CTC_EQUAL, treeMaker.Ident(fieldName), treeMaker.Literal(CTC_BOT, null)), throwStatement, null);
+		JCBlock throwBlock = treeMaker.Block(0, List.of(throwStatement));
+		return treeMaker.If(treeMaker.Binary(CTC_EQUAL, treeMaker.Ident(fieldName), treeMaker.Literal(CTC_BOT, null)), throwBlock, null);
 	}
 	
 	/**
diff --git a/src/core/lombok/javac/handlers/NonNullHandler.java b/src/core/lombok/javac/handlers/NonNullHandler.java
new file mode 100644
index 00000000..415d6032
--- /dev/null
+++ b/src/core/lombok/javac/handlers/NonNullHandler.java
@@ -0,0 +1,148 @@
+/*
+ * Copyright (C) 2013 The Project Lombok Authors.
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package lombok.javac.handlers;
+
+import static lombok.javac.Javac.*;
+import static lombok.javac.handlers.JavacHandlerUtil.*;
+
+import org.mangosdk.spi.ProviderFor;
+
+import com.sun.tools.javac.tree.JCTree.JCAnnotation;
+import com.sun.tools.javac.tree.JCTree.JCBinary;
+import com.sun.tools.javac.tree.JCTree.JCBlock;
+import com.sun.tools.javac.tree.JCTree.JCExpression;
+import com.sun.tools.javac.tree.JCTree.JCIdent;
+import com.sun.tools.javac.tree.JCTree.JCIf;
+import com.sun.tools.javac.tree.JCTree.JCLiteral;
+import com.sun.tools.javac.tree.JCTree.JCMethodDecl;
+import com.sun.tools.javac.tree.JCTree.JCParens;
+import com.sun.tools.javac.tree.JCTree.JCStatement;
+import com.sun.tools.javac.tree.JCTree.JCThrow;
+import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
+import com.sun.tools.javac.util.List;
+
+import lombok.NonNull;
+import lombok.core.AnnotationValues;
+import lombok.core.AST.Kind;
+import lombok.javac.JavacAnnotationHandler;
+import lombok.javac.JavacNode;
+
+@ProviderFor(JavacAnnotationHandler.class)
+public class NonNullHandler extends JavacAnnotationHandler<NonNull> {
+	@Override public void handle(AnnotationValues<NonNull> annotation, JCAnnotation ast, JavacNode annotationNode) {
+		if (annotationNode.up().getKind() == Kind.FIELD) {
+			// This is meaningless unless the field is used to generate a method (@Setter, @RequiredArgsConstructor, etc),
+			// but in that case those handlers will take care of it. However, we DO check if the annotation is applied to
+			// a primitive, because those handlers trigger on any annotation named @NonNull and we only want the warning
+			// behaviour on _OUR_ 'lombok.NonNull'.
+			
+			try {
+				if (isPrimitive(((JCVariableDecl) annotationNode.up().get()).vartype)) {
+					annotationNode.addWarning("@NonNull is meaningless on a primitive.");
+				}
+			} catch (Exception ignore) {}
+			
+			return;
+		}
+		
+		if (annotationNode.up().getKind() != Kind.ARGUMENT) return;
+		
+		JCMethodDecl declaration;
+		
+		try {
+			declaration = (JCMethodDecl) annotationNode.up().up().get();
+		} catch (Exception e) {
+			return;
+		}
+		
+		if (JavacHandlerUtil.isGenerated(declaration)) return;
+		
+		// Possibly, if 'declaration instanceof ConstructorDeclaration', fetch declaration.constructorCall, search it for any references to our parameter,
+		// and if they exist, create a new method in the class: 'private static <T> T lombok$nullCheck(T expr, String msg) {if (expr == null) throw NPE; return expr;}' and
+		// wrap all references to it in the super/this to a call to this method.
+		
+		JCStatement nullCheck = recursiveSetGeneratedBy(generateNullCheck(annotationNode.getTreeMaker(), annotationNode.up()), ast);
+		
+		if (nullCheck == null) {
+			// @NonNull applied to a primitive. Kinda pointless. Let's generate a warning.
+			annotationNode.addWarning("@NonNull is meaningless on a primitive.");
+			return;
+		}
+		
+		List<JCStatement> statements = declaration.body.stats;
+		
+		String expectedName = annotationNode.up().getName();
+		for (JCStatement stat : statements) {
+			if (JavacHandlerUtil.isConstructorCall(stat)) continue;
+			String varNameOfNullCheck = returnVarNameIfNullCheck(stat);
+			if (varNameOfNullCheck == null) break;
+			if (varNameOfNullCheck.equals(expectedName)) return;
+		}
+		
+		List<JCStatement> tail = statements;
+		List<JCStatement> head = List.nil();
+		for (JCStatement stat : statements) {
+			if (JavacHandlerUtil.isConstructorCall(stat) || JavacHandlerUtil.isGenerated(stat)) {
+				tail = tail.tail;
+				head = head.prepend(stat);
+				continue;
+			}
+			break;
+		}
+		
+		List<JCStatement> newList = tail.prepend(nullCheck);
+		for (JCStatement stat : head) newList = newList.prepend(stat);
+		declaration.body.stats = newList;
+	}
+	
+	/**
+	 * Checks if the statement is of the form 'if (x == null) {throw WHATEVER;},
+	 * where the block braces are optional. If it is of this form, returns "x".
+	 * If it is not of this form, returns null.
+	 */
+	private String returnVarNameIfNullCheck(JCStatement stat) {
+		if (!(stat instanceof JCIf)) return null;
+		
+		/* Check that the if's statement is a throw statement, possibly in a block. */ {
+			JCStatement then = ((JCIf) stat).thenpart;
+			if (then instanceof JCBlock) {
+				List<JCStatement> stats = ((JCBlock) then).stats;
+				if (stats.length() == 0) return null;
+				then = stats.get(0);
+			}
+			if (!(then instanceof JCThrow)) return null;
+		}
+		
+		/* Check that the if's conditional is like 'x == null'. Return from this method (don't generate
+		   a nullcheck) if 'x' is equal to our own variable's name: There's already a nullcheck here. */ {
+			JCExpression cond = ((JCIf) stat).cond;
+			while (cond instanceof JCParens) cond = ((JCParens) cond).expr;
+			if (!(cond instanceof JCBinary)) return null;
+			JCBinary bin = (JCBinary) cond;
+			if (getTag(bin) != CTC_EQUAL) return null;
+			if (!(bin.lhs instanceof JCIdent)) return null;
+			if (!(bin.rhs instanceof JCLiteral)) return null;
+			if (((JCLiteral) bin.rhs).typetag != CTC_BOT) return null;
+			return ((JCIdent) bin.lhs).name.toString();
+		}
+	}
+}
diff --git a/src/utils/lombok/javac/Javac.java b/src/utils/lombok/javac/Javac.java
index b4e58b8f..08c7c957 100644
--- a/src/utils/lombok/javac/Javac.java
+++ b/src/utils/lombok/javac/Javac.java
@@ -21,6 +21,8 @@
  */
 package lombok.javac;
 
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -129,4 +131,34 @@ public class Javac {
 			throw new RuntimeException(e);
 		}
 	}
+	
+	private static final Field JCTREE_TAG;
+	private static final Method JCTREE_GETTAG;
+	static {
+		Field f = null;
+		try {
+			f = JCTree.class.getDeclaredField("tag");
+		} catch (NoSuchFieldException e) {}
+		JCTREE_TAG = f;
+		
+		Method m = null;
+		try {
+			m = JCTree.class.getDeclaredMethod("getTag");
+		} catch (NoSuchMethodException e) {}
+		JCTREE_GETTAG = m;
+	}
+	
+	public static int getTag(JCTree node) {
+		if (JCTREE_GETTAG != null) {
+			try {
+				return (Integer) JCTREE_GETTAG.invoke(node);
+			} catch (Exception e) {}
+		}
+		try {
+			return (Integer) JCTREE_TAG.get(node);
+		} catch (Exception e) {
+			throw new IllegalStateException("Can't get node tag");
+		}
+	}
+	
 }