Merge branch 'master' of https://github.com/janrieke/lombok into janrieke-master

Also fixed up style and docs, and updated behaviour when using `@Builder(inherit = true)` to error if you have no parent class.

src/core/lombok/Builder.java

@@ -131,6 +131,48 @@ public @interface Builder {
 	 */
 	String builderClassName() default "";
 	
+	/**
+	 * Should the generated builder extend the parent class's builder?
+	 * 
+	 * If {@code true}, the generated builder class will extend the builder of the
+	 * superclass. This means the builder also contains the methods for fields from
+	 * the superclass.
+	 * <p>
+	 * Note that both this builder and the superclass' builder must be a builder
+	 * for a type (so, not for a static method or a constructor). You must mark
+	 * the parent extendable: {@code @Builder(extensible = true)}.
+	 * <p>
+	 * This builder will also be {@code extensible = true} if you set {@code inherit = true}.
+	 * 
+	 * @see #extensible()
+	 */
+	boolean inherit() default false;
+	
+	/**
+	 * Should the generated builder be extensible by subclasses?
+	 * 
+	 * If {@code true} the generated builder class will be extensible by
+	 * {@code @Builder} classes of this class's subclasses, by marking them
+	 * with {@code @Builder(inherit = true)}.
+	 * <p>
+	 * The {@code @Builder} extensible system only works for {@code @Builder}
+	 * annotations on types (so, not on a static method or a constructor).
+	 * 
+	 * @see #inherit()
+	 */
+	boolean extensible() default false;
+	
+	/**
+	 * Name of the builder class in the superclass.
+	 * 
+	 * Only relevant if {@code inherit = true}
+	 * 
+	 * Default: {@code (SuperclassTypeName)Builder}.
+	 * 
+	 * @see #inherit()
+	 */
+	String superclassBuilderClassName() default "";
+	
 	/**
 	 * If true, generate an instance method to obtain a builder that is initialized with the values of this instance.
 	 * Legal only if {@code @Builder} is used on a constructor, on the type itself, or on a static method that returns

src/core/lombok/eclipse/handlers/EclipseSingularsRecipes.java

@@ -45,6 +45,8 @@ import org.eclipse.jdt.internal.compiler.ast.OperatorIds;
 import org.eclipse.jdt.internal.compiler.ast.ParameterizedQualifiedTypeReference;
 import org.eclipse.jdt.internal.compiler.ast.ParameterizedSingleTypeReference;
 import org.eclipse.jdt.internal.compiler.ast.QualifiedTypeReference;
+import org.eclipse.jdt.internal.compiler.ast.Reference;
+import org.eclipse.jdt.internal.compiler.ast.SingleNameReference;
 import org.eclipse.jdt.internal.compiler.ast.SingleTypeReference;
 import org.eclipse.jdt.internal.compiler.ast.Statement;
 import org.eclipse.jdt.internal.compiler.ast.ThisReference;
@@ -216,7 +218,7 @@ public class EclipseSingularsRecipes {
 		
 		public abstract List<EclipseNode> generateFields(SingularData data, EclipseNode builderType);
 		public abstract void generateMethods(SingularData data, boolean deprecate, EclipseNode builderType, boolean fluent, boolean chain);
-		public abstract void appendBuildCode(SingularData data, EclipseNode builderType, List<Statement> statements, char[] targetVariableName);
+		public abstract void appendBuildCode(SingularData data, EclipseNode builderType, List<Statement> statements, char[] targetVariableName, String builderVariable);
 		
 		public boolean requiresCleaning() {
 			try {
@@ -307,16 +309,16 @@ public class EclipseSingularsRecipes {
 		private static final char[] SIZE_TEXT = new char[] {'s', 'i', 'z', 'e'};
 		
 		/** Generates 'this.<em>name</em>.size()' as an expression; if nullGuard is true, it's this.name == null ? 0 : this.name.size(). */
-		protected Expression getSize(EclipseNode builderType, char[] name, boolean nullGuard) {
+		protected Expression getSize(EclipseNode builderType, char[] name, boolean nullGuard, String builderVariable) {
 			MessageSend invoke = new MessageSend();
-			ThisReference thisRef = new ThisReference(0, 0);
+			Reference thisRef = getBuilderReference(builderVariable);
 			FieldReference thisDotName = new FieldReference(name, 0L);
 			thisDotName.receiver = thisRef;
 			invoke.receiver = thisDotName;
 			invoke.selector = SIZE_TEXT;
 			if (!nullGuard) return invoke;
 			
-			ThisReference cdnThisRef = new ThisReference(0, 0);
+			Reference cdnThisRef = getBuilderReference(builderVariable);
 			FieldReference cdnThisDotName = new FieldReference(name, 0L);
 			cdnThisDotName.receiver = cdnThisRef;
 			NullLiteral nullLiteral = new NullLiteral(0, 0);
@@ -345,5 +347,14 @@ public class EclipseSingularsRecipes {
 			
 			return new QualifiedTypeReference(TypeConstants.JAVA_LANG_OBJECT, NULL_POSS);
 		}
+		
+		/** @return a {@code SingleNameReference} to the builder in the variable <code>builderVariable</code>. If {@ code builderVariable == "this"}, a {@code ThisReference} is returned. */
+		protected static Reference getBuilderReference(String builderVariable) {
+			if ("this".equals(builderVariable)) {
+				return new ThisReference(0, 0);
+			} else {
+				return new SingleNameReference(builderVariable.toCharArray(), 0);
+			}
+		}
 	}
 }

src/core/lombok/eclipse/handlers/HandleBuilder.java

@@ -25,6 +25,7 @@ import static lombok.eclipse.Eclipse.*;
 import static lombok.core.handlers.HandlerUtil.*;
 import static lombok.eclipse.handlers.EclipseHandlerUtil.*;
 
+import java.lang.reflect.Modifier;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -40,6 +41,7 @@ import org.eclipse.jdt.internal.compiler.ast.Assignment;
 import org.eclipse.jdt.internal.compiler.ast.CompilationUnitDeclaration;
 import org.eclipse.jdt.internal.compiler.ast.ConditionalExpression;
 import org.eclipse.jdt.internal.compiler.ast.ConstructorDeclaration;
+import org.eclipse.jdt.internal.compiler.ast.ExplicitConstructorCall;
 import org.eclipse.jdt.internal.compiler.ast.Expression;
 import org.eclipse.jdt.internal.compiler.ast.FalseLiteral;
 import org.eclipse.jdt.internal.compiler.ast.FieldDeclaration;
@@ -50,6 +52,7 @@ import org.eclipse.jdt.internal.compiler.ast.MethodDeclaration;
 import org.eclipse.jdt.internal.compiler.ast.OperatorIds;
 import org.eclipse.jdt.internal.compiler.ast.ParameterizedQualifiedTypeReference;
 import org.eclipse.jdt.internal.compiler.ast.ParameterizedSingleTypeReference;
+import org.eclipse.jdt.internal.compiler.ast.QualifiedNameReference;
 import org.eclipse.jdt.internal.compiler.ast.QualifiedThisReference;
 import org.eclipse.jdt.internal.compiler.ast.QualifiedTypeReference;
 import org.eclipse.jdt.internal.compiler.ast.ReturnStatement;
@@ -81,6 +84,7 @@ import lombok.core.HandlerPriority;
 import lombok.eclipse.Eclipse;
 import lombok.eclipse.EclipseAnnotationHandler;
 import lombok.eclipse.EclipseNode;
+import lombok.eclipse.handlers.EclipseHandlerUtil.MemberExistsResult;
 import lombok.eclipse.handlers.EclipseSingularsRecipes.EclipseSingularizer;
 import lombok.eclipse.handlers.EclipseSingularsRecipes.SingularData;
 import lombok.eclipse.handlers.HandleConstructor.SkipIfConstructorExists;
@@ -102,6 +106,7 @@ public class HandleBuilder extends EclipseAnnotationHandler<Builder> {
 	}
 	
 	private static class BuilderFieldData {
+		EclipseNode fieldNode;
 		TypeReference type;
 		char[] rawName;
 		char[] name;
@@ -155,6 +160,10 @@ public class HandleBuilder extends EclipseAnnotationHandler<Builder> {
 		String builderMethodName = builderInstance.builderMethodName();
 		String buildMethodName = builderInstance.buildMethodName();
 		String builderClassName = builderInstance.builderClassName();
+		
+		boolean inherit = builderInstance.inherit();
+		boolean extensible = inherit || builderInstance.extensible(); // inherit implies extendable
+		
 		String toBuilderMethodName = "toBuilder";
 		boolean toBuilder = builderInstance.toBuilder();
 		List<char[]> typeArgsForToBuilder = null;
@@ -182,9 +191,11 @@ public class HandleBuilder extends EclipseAnnotationHandler<Builder> {
 		boolean addCleaning = false;
 		boolean isStatic = true;
 		
+		TypeDeclaration td = null;
+		
 		if (parent.get() instanceof TypeDeclaration) {
 			tdParent = parent;
-			TypeDeclaration td = (TypeDeclaration) tdParent.get();
+			td = (TypeDeclaration) tdParent.get();
 			
 			List<EclipseNode> allFields = new ArrayList<EclipseNode>();
 			boolean valuePresent = (hasAnnotation(lombok.Value.class, parent) || hasAnnotation("lombok.experimental.Value", parent));
@@ -194,6 +205,7 @@ public class HandleBuilder extends EclipseAnnotationHandler<Builder> {
 				boolean isFinal = ((fd.modifiers & ClassFileConstants.AccFinal) != 0) || (valuePresent && !hasAnnotation(NonFinal.class, fieldNode));
 				
 				BuilderFieldData bfd = new BuilderFieldData();
+				bfd.fieldNode = fieldNode;
 				bfd.rawName = fieldNode.getName().toCharArray();
 				bfd.name = removePrefixFromField(fieldNode);
 				bfd.type = fd.type;
@@ -227,15 +239,29 @@ public class HandleBuilder extends EclipseAnnotationHandler<Builder> {
 				allFields.add(fieldNode);
 			}
 			
-			handleConstructor.generateConstructor(tdParent, AccessLevel.PACKAGE, allFields, false, null, SkipIfConstructorExists.I_AM_BUILDER,
-				Collections.<Annotation>emptyList(), annotationNode);
+			if (builderClassName.isEmpty()) builderClassName = new String(td.name) + "Builder";
+			
+			if (extensible) {
+				boolean callBuilderBasedSuperConstructor = td.superclass != null;
+				generateBuilderBasedConstructor(tdParent, builderFields, annotationNode, builderClassName, callBuilderBasedSuperConstructor);
+			} else {
+				handleConstructor.generateConstructor(tdParent, AccessLevel.PACKAGE, allFields, false, null, SkipIfConstructorExists.I_AM_BUILDER,
+					Collections.<Annotation>emptyList(), annotationNode);
+			}
 			
 			returnType = namePlusTypeParamsToTypeReference(td.name, td.typeParameters, p);
 			typeParams = td.typeParameters;
 			thrownExceptions = null;
 			nameOfStaticBuilderMethod = null;
-			if (builderClassName.isEmpty()) builderClassName = new String(td.name) + "Builder";
 		} else if (parent.get() instanceof ConstructorDeclaration) {
+			if (inherit) {
+				annotationNode.addError("@Builder(inherit=true) is only supported for type builders.");
+				return;
+			}
+			if (extensible) {
+				annotationNode.addError("@Builder(extensible=true) is only supported for type builders.");
+				return;
+			}
 			ConstructorDeclaration cd = (ConstructorDeclaration) parent.get();
 			if (cd.typeParameters != null && cd.typeParameters.length > 0) {
 				annotationNode.addError("@Builder is not supported on constructors with constructor type parameters.");
@@ -243,13 +269,21 @@ public class HandleBuilder extends EclipseAnnotationHandler<Builder> {
 			}
 			
 			tdParent = parent.up();
-			TypeDeclaration td = (TypeDeclaration) tdParent.get();
+			td = (TypeDeclaration) tdParent.get();
 			returnType = namePlusTypeParamsToTypeReference(td.name, td.typeParameters, p);
 			typeParams = td.typeParameters;
 			thrownExceptions = cd.thrownExceptions;
 			nameOfStaticBuilderMethod = null;
 			if (builderClassName.isEmpty()) builderClassName = new String(cd.selector) + "Builder";
 		} else if (parent.get() instanceof MethodDeclaration) {
+			if (inherit) {
+				annotationNode.addError("@Builder(inherit=true) is only supported for type builders.");
+				return;
+			}
+			if (extensible) {
+				annotationNode.addError("@Builder(extendable=true) is only supported for type builders.");
+				return;
+			}
 			MethodDeclaration md = (MethodDeclaration) parent.get();
 			tdParent = parent.up();
 			isStatic = md.isStatic();
@@ -380,7 +414,20 @@ public class HandleBuilder extends EclipseAnnotationHandler<Builder> {
 		
 		EclipseNode builderType = findInnerClass(tdParent, builderClassName);
 		if (builderType == null) {
-			builderType = makeBuilderClass(isStatic, tdParent, builderClassName, typeParams, ast);
+			String superclassBuilderClassName = null;
+			if (inherit) {
+				if (td.superclass == null) {
+					annotationNode.addError("@Builder(inherit = true) requires that your class has an 'extends' clause.");
+					return;
+				}
+				
+				superclassBuilderClassName = builderInstance.superclassBuilderClassName();
+				if (superclassBuilderClassName == null || superclassBuilderClassName.isEmpty()) {
+					superclassBuilderClassName = new String(td.superclass.getLastToken()) + "Builder";
+				}
+			}
+			
+			builderType = makeBuilderClass(isStatic, tdParent, builderClassName, typeParams, ast, superclassBuilderClassName);
 		} else {
 			TypeDeclaration builderTypeDeclaration = (TypeDeclaration) builderType.get();
 			if (isStatic && (builderTypeDeclaration.modifiers & ClassFileConstants.AccStatic) == 0) {
@@ -444,7 +491,7 @@ public class HandleBuilder extends EclipseAnnotationHandler<Builder> {
 		}
 		
 		if (methodExists(buildMethodName, builderType, -1) == MemberExistsResult.NOT_EXISTS) {
-			MethodDeclaration md = generateBuildMethod(tdParent, isStatic, buildMethodName, nameOfStaticBuilderMethod, returnType, builderFields, builderType, thrownExceptions, addCleaning, ast);
+			MethodDeclaration md = generateBuildMethod(tdParent, isStatic, buildMethodName, nameOfStaticBuilderMethod, returnType, builderFields, builderType, thrownExceptions, addCleaning, ast, extensible);
 			if (md != null) injectMethod(builderType, md);
 		}
 		
@@ -492,8 +539,7 @@ public class HandleBuilder extends EclipseAnnotationHandler<Builder> {
 		int pS = source.sourceStart, pE = source.sourceEnd;
 		long p = (long) pS << 32 | pE;
 		
-		MethodDeclaration out = new MethodDeclaration(
-				((CompilationUnitDeclaration) type.top().get()).compilationResult);
+		MethodDeclaration out = new MethodDeclaration(((CompilationUnitDeclaration) type.top().get()).compilationResult);
 		out.selector = methodName.toCharArray();
 		out.modifiers = ClassFileConstants.AccPublic;
 		out.bits |= ECLIPSE_DO_NOT_TOUCH_FLAG;
@@ -531,6 +577,95 @@ public class HandleBuilder extends EclipseAnnotationHandler<Builder> {
 
 	}
 	
+	/**
+	 * Generates a constructor that has a builder as the only parameter.
+	 * The values from the builder are used to initialize the fields of new instances.
+	 *
+	 * @param typeNode
+	 *            the type (with the {@code @Builder} annotation) for which a
+	 *            constructor should be generated.
+	 * @param builderFields a list of fields in the builder which should be assigned to new instances.
+	 * @param sourceNode the annotation (used for setting source code locations for the generated code).
+	 * @param builderClassnameAsParameter
+	 *            If {@code != null}, the only parameter of the constructor will
+	 *            be a builder with this classname; the constructor will then
+	 *            use the values within this builder to assign the fields of new
+	 *            instances.
+	 * @param callBuilderBasedSuperConstructor
+	 *            If {@code true}, the constructor will explicitly call a super
+	 *            constructor with the builder as argument. Requires
+	 *            {@code builderClassAsParameter != null}.
+	 */
+	private void generateBuilderBasedConstructor(EclipseNode typeNode, List<BuilderFieldData> builderFields, EclipseNode sourceNode,
+			String builderClassnameAsParameter, boolean callBuilderBasedSuperConstructor) {
+		
+		ASTNode source = sourceNode.get();
+		
+		TypeDeclaration typeDeclaration = ((TypeDeclaration) typeNode.get());
+		long p = (long) source.sourceStart << 32 | source.sourceEnd;
+		
+		boolean isEnum = (((TypeDeclaration) typeNode.get()).modifiers & ClassFileConstants.AccEnum) != 0;
+		AccessLevel level = isEnum ? AccessLevel.PRIVATE : AccessLevel.PROTECTED;
+		
+		ConstructorDeclaration constructor = new ConstructorDeclaration(((CompilationUnitDeclaration) typeNode.top().get()).compilationResult);
+		
+		constructor.modifiers = toEclipseModifier(level);
+		constructor.selector = typeDeclaration.name;
+		if (callBuilderBasedSuperConstructor) {
+			constructor.constructorCall = new ExplicitConstructorCall(ExplicitConstructorCall.Super);
+			constructor.constructorCall.arguments = new Expression[] {new SingleNameReference("b".toCharArray(), p)};
+		} else {
+			constructor.constructorCall = new ExplicitConstructorCall(ExplicitConstructorCall.ImplicitSuper);
+		}
+		constructor.constructorCall.sourceStart = source.sourceStart;
+		constructor.constructorCall.sourceEnd = source.sourceEnd;
+		constructor.thrownExceptions = null;
+		constructor.typeParameters = null;
+		constructor.bits |= ECLIPSE_DO_NOT_TOUCH_FLAG;
+		constructor.bodyStart = constructor.declarationSourceStart = constructor.sourceStart = source.sourceStart;
+		constructor.bodyEnd = constructor.declarationSourceEnd = constructor.sourceEnd = source.sourceEnd;
+		constructor.arguments = null;
+		
+		List<Statement> statements = new ArrayList<Statement>();
+		List<Statement> nullChecks = new ArrayList<Statement>();
+		
+		for (BuilderFieldData fieldNode : builderFields) {
+			char[] fieldName = removePrefixFromField(fieldNode.fieldNode);
+			FieldReference thisX = new FieldReference(fieldNode.rawName, p);
+			int s = (int) (p >> 32);
+			int e = (int) p;
+			thisX.receiver = new ThisReference(s, e);
+			
+			Expression assignmentExpr;
+			if (fieldNode.singularData != null && fieldNode.singularData.getSingularizer() != null) {
+				fieldNode.singularData.getSingularizer().appendBuildCode(fieldNode.singularData, typeNode, statements, fieldNode.name, "b");
+				assignmentExpr = new SingleNameReference(fieldNode.name, p);
+			} else {
+				char[][] variableInBuilder = new char[][] {"b".toCharArray(), fieldName};
+				long[] positions = new long[] {p, p};
+				assignmentExpr = new QualifiedNameReference(variableInBuilder, positions, s, e);
+			}
+			
+			Assignment assignment = new Assignment(thisX, assignmentExpr, (int) p);
+			statements.add(assignment);
+			Annotation[] nonNulls = findAnnotations((FieldDeclaration)fieldNode.fieldNode.get(), NON_NULL_PATTERN);
+			if (nonNulls.length != 0) {
+				Statement nullCheck = generateNullCheck((FieldDeclaration)fieldNode.fieldNode.get(), sourceNode);
+				if (nullCheck != null) {
+					nullChecks.add(nullCheck);
+				}
+			}
+		}
+		
+		nullChecks.addAll(statements);
+		constructor.statements = nullChecks.isEmpty() ? null : nullChecks.toArray(new Statement[nullChecks.size()]);
+		constructor.arguments = new Argument[] {new Argument("b".toCharArray(), p, new SingleTypeReference(builderClassnameAsParameter.toCharArray(), p), Modifier.FINAL)};
+		
+		constructor.traverse(new SetGeneratedByVisitor(source), typeDeclaration.scope);
+		
+		injectMethod(typeNode, constructor);
+	}
+	
 	private MethodDeclaration generateCleanMethod(List<BuilderFieldData> builderFields, EclipseNode builderType, ASTNode source) {
 		List<Statement> statements = new ArrayList<Statement>();
 		
@@ -553,49 +688,58 @@ public class HandleBuilder extends EclipseAnnotationHandler<Builder> {
 		return decl;
 	}
 	
-	public MethodDeclaration generateBuildMethod(EclipseNode tdParent, boolean isStatic, String name, char[] staticName, TypeReference returnType, List<BuilderFieldData> builderFields, EclipseNode type, TypeReference[] thrownExceptions, boolean addCleaning, ASTNode source) {
+	/**
+	 * @param useBuilderBasedConstructor
+	 *            if true, the {@code build()} method will use a constructor
+	 *            that takes the builder instance as parameter (instead of a
+	 *            constructor with all relevant fields as parameters)
+	 */
+	public MethodDeclaration generateBuildMethod(EclipseNode tdParent, boolean isStatic, String name, char[] staticName, TypeReference returnType, List<BuilderFieldData> builderFields, EclipseNode type, TypeReference[] thrownExceptions, boolean addCleaning, ASTNode source, boolean useBuilderBasedConstructor) {
 		MethodDeclaration out = new MethodDeclaration(((CompilationUnitDeclaration) type.top().get()).compilationResult);
 		out.bits |= ECLIPSE_DO_NOT_TOUCH_FLAG;
 		List<Statement> statements = new ArrayList<Statement>();
-		
-		if (addCleaning) {
-			FieldReference thisUnclean = new FieldReference(CLEAN_FIELD_NAME, 0);
-			thisUnclean.receiver = new ThisReference(0, 0);
-			Expression notClean = new UnaryExpression(thisUnclean, OperatorIds.NOT);
-			MessageSend invokeClean = new MessageSend();
-			invokeClean.selector = CLEAN_METHOD_NAME;
-			statements.add(new IfStatement(notClean, invokeClean, 0, 0));
-		}
-		
-		for (BuilderFieldData bfd : builderFields) {
-			if (bfd.singularData != null && bfd.singularData.getSingularizer() != null) {
-				bfd.singularData.getSingularizer().appendBuildCode(bfd.singularData, type, statements, bfd.name);
-			}
-		}
-		
 		List<Expression> args = new ArrayList<Expression>();
-		for (BuilderFieldData bfd : builderFields) {
-			if (bfd.nameOfSetFlag != null) {
-				MessageSend inv = new MessageSend();
-				inv.sourceStart = source.sourceStart;
-				inv.sourceEnd = source.sourceEnd;
-				inv.receiver = new SingleNameReference(((TypeDeclaration) tdParent.get()).name, 0L);
-				inv.selector = bfd.nameOfDefaultProvider;
-				inv.typeArguments = typeParameterNames(((TypeDeclaration) type.get()).typeParameters);
-				
-				args.add(new ConditionalExpression(
-					new SingleNameReference(bfd.nameOfSetFlag,  0L),
-					new SingleNameReference(bfd.name, 0L),
-					inv));
-			} else {
-				args.add(new SingleNameReference(bfd.name, 0L));
-			}
-		}
 		
-		if (addCleaning) {
-			FieldReference thisUnclean = new FieldReference(CLEAN_FIELD_NAME, 0);
-			thisUnclean.receiver = new ThisReference(0, 0);
-			statements.add(new Assignment(thisUnclean, new TrueLiteral(0, 0), 0));
+		// Extendable builders assign their values in the constructor, not in this build() method.
+		if (!useBuilderBasedConstructor) {
+			if (addCleaning) {
+				FieldReference thisUnclean = new FieldReference(CLEAN_FIELD_NAME, 0);
+				thisUnclean.receiver = new ThisReference(0, 0);
+				Expression notClean = new UnaryExpression(thisUnclean, OperatorIds.NOT);
+				MessageSend invokeClean = new MessageSend();
+				invokeClean.selector = CLEAN_METHOD_NAME;
+				statements.add(new IfStatement(notClean, invokeClean, 0, 0));
+			}
+			
+			for (BuilderFieldData bfd : builderFields) {
+				if (bfd.singularData != null && bfd.singularData.getSingularizer() != null) {
+					bfd.singularData.getSingularizer().appendBuildCode(bfd.singularData, type, statements, bfd.name, "this");
+				}
+			}
+			
+			for (BuilderFieldData bfd : builderFields) {
+				if (bfd.nameOfSetFlag != null) {
+					MessageSend inv = new MessageSend();
+					inv.sourceStart = source.sourceStart;
+					inv.sourceEnd = source.sourceEnd;
+					inv.receiver = new SingleNameReference(((TypeDeclaration) tdParent.get()).name, 0L);
+					inv.selector = bfd.nameOfDefaultProvider;
+					inv.typeArguments = typeParameterNames(((TypeDeclaration) type.get()).typeParameters);
+					
+					args.add(new ConditionalExpression(
+						new SingleNameReference(bfd.nameOfSetFlag,  0L),
+						new SingleNameReference(bfd.name, 0L),
+						inv));
+				} else {
+					args.add(new SingleNameReference(bfd.name, 0L));
+				}
+			}
+			
+			if (addCleaning) {
+				FieldReference thisUnclean = new FieldReference(CLEAN_FIELD_NAME, 0);
+				thisUnclean.receiver = new ThisReference(0, 0);
+				statements.add(new Assignment(thisUnclean, new TrueLiteral(0, 0), 0));
+			}
 		}
 		
 		out.modifiers = ClassFileConstants.AccPublic;
@@ -607,7 +751,13 @@ public class HandleBuilder extends EclipseAnnotationHandler<Builder> {
 		if (staticName == null) {
 			AllocationExpression allocationStatement = new AllocationExpression();
 			allocationStatement.type = copyType(out.returnType);
-			allocationStatement.arguments = args.isEmpty() ? null : args.toArray(new Expression[args.size()]);
+			if (useBuilderBasedConstructor) {
+				// Use a constructor that only has this builder as parameter.
+				allocationStatement.arguments = new Expression[] {new ThisReference(0, 0)};
+			} else {
+				// Use a constructor with all the fields.
+				allocationStatement.arguments = args.isEmpty() ? null : args.toArray(new Expression[args.size()]);
+			}
 			statements.add(new ReturnStatement(allocationStatement, 0, 0));
 		} else {
 			MessageSend invoke = new MessageSend();
@@ -756,7 +906,7 @@ public class HandleBuilder extends EclipseAnnotationHandler<Builder> {
 		return null;
 	}
 	
-	public EclipseNode makeBuilderClass(boolean isStatic, EclipseNode tdParent, String builderClassName, TypeParameter[] typeParams, ASTNode source) {
+	public EclipseNode makeBuilderClass(boolean isStatic, EclipseNode tdParent, String builderClassName, TypeParameter[] typeParams, ASTNode source, String parentBuilderClassName) {
 		TypeDeclaration parent = (TypeDeclaration) tdParent.get();
 		TypeDeclaration builder = new TypeDeclaration(parent.compilationResult);
 		builder.bits |= Eclipse.ECLIPSE_DO_NOT_TOUCH_FLAG;
@@ -764,6 +914,7 @@ public class HandleBuilder extends EclipseAnnotationHandler<Builder> {
 		if (isStatic) builder.modifiers |= ClassFileConstants.AccStatic;
 		builder.typeParameters = copyTypeParams(typeParams, source);
 		builder.name = builderClassName.toCharArray();
+		if (parentBuilderClassName != null) builder.superclass = new SingleTypeReference(parentBuilderClassName.toCharArray(), 0);
 		builder.traverse(new SetGeneratedByVisitor(source), (ClassScope) null);
 		return injectType(tdParent, builder);
 	}

src/core/lombok/eclipse/handlers/HandleConstructor.java

@@ -267,7 +267,7 @@ public class HandleConstructor {
 		}
 	}
 	
-	private static final char[][] JAVA_BEANS_CONSTRUCTORPROPERTIES = new char[][] { "java".toCharArray(), "beans".toCharArray(), "ConstructorProperties".toCharArray() };
+	public static final char[][] JAVA_BEANS_CONSTRUCTORPROPERTIES = new char[][] { "java".toCharArray(), "beans".toCharArray(), "ConstructorProperties".toCharArray() };
 	public static Annotation[] createConstructorProperties(ASTNode source, Collection<EclipseNode> fields) {
 		if (fields.isEmpty()) return null;
 		

src/core/lombok/eclipse/handlers/singulars/EclipseGuavaSingularizer.java

@@ -200,7 +200,7 @@ abstract class EclipseGuavaSingularizer extends EclipseSingularizer {
 		injectMethod(builderType, md);
 	}
 	
-	@Override public void appendBuildCode(SingularData data, EclipseNode builderType, List<Statement> statements, char[] targetVariableName) {
+	@Override public void appendBuildCode(SingularData data, EclipseNode builderType, List<Statement> statements, char[] targetVariableName, String builderVariable) {
 		TypeReference varType = new QualifiedTypeReference(fromQualifiedName(data.getTargetFqn()), NULL_POSS);
 		String simpleTypeName = getSimpleTargetTypeName(data);
 		int agrumentsCount = getTypeArgumentsCount();
@@ -219,14 +219,14 @@ abstract class EclipseGuavaSingularizer extends EclipseSingularizer {
 			invokeBuild = new MessageSend();
 			invokeBuild.selector = new char[] {'b', 'u', 'i', 'l', 'd'};
 			FieldReference thisDotField = new FieldReference(data.getPluralName(), 0L);
-			thisDotField.receiver = new ThisReference(0, 0);
+			thisDotField.receiver = getBuilderReference(builderVariable);
 			invokeBuild.receiver = thisDotField;
 		}
 		
 		Expression isNull; {
 			//this.pluralName == null
 			FieldReference thisDotField = new FieldReference(data.getPluralName(), 0L);
-			thisDotField.receiver = new ThisReference(0, 0);
+			thisDotField.receiver = getBuilderReference(builderVariable);
 			isNull = new EqualExpression(thisDotField, new NullLiteral(0, 0), OperatorIds.EQUAL_EQUAL);
 		}
 		

src/core/lombok/eclipse/handlers/singulars/EclipseJavaUtilListSingularizer.java

@@ -45,7 +45,6 @@ import org.eclipse.jdt.internal.compiler.ast.QualifiedTypeReference;
 import org.eclipse.jdt.internal.compiler.ast.SingleNameReference;
 import org.eclipse.jdt.internal.compiler.ast.Statement;
 import org.eclipse.jdt.internal.compiler.ast.SwitchStatement;
-import org.eclipse.jdt.internal.compiler.ast.ThisReference;
 import org.eclipse.jdt.internal.compiler.ast.TypeReference;
 import org.mangosdk.spi.ProviderFor;
 
@@ -56,9 +55,9 @@ public class EclipseJavaUtilListSingularizer extends EclipseJavaUtilListSetSingu
 		return LombokImmutableList.of("java.util.List", "java.util.Collection", "java.lang.Iterable");
 	}
 	
-	@Override public void appendBuildCode(SingularData data, EclipseNode builderType, List<Statement> statements, char[] targetVariableName) {
+	@Override public void appendBuildCode(SingularData data, EclipseNode builderType, List<Statement> statements, char[] targetVariableName, String builderVariable) {
 		if (useGuavaInstead(builderType)) {
-			guavaListSetSingularizer.appendBuildCode(data, builderType, statements, targetVariableName);
+			guavaListSetSingularizer.appendBuildCode(data, builderType, statements, targetVariableName, builderVariable);
 			return;
 		}
 		
@@ -76,7 +75,7 @@ public class EclipseJavaUtilListSingularizer extends EclipseJavaUtilListSetSingu
 		/* case 1: (singleton) break; */ {
 			switchContents.add(new CaseStatement(makeIntLiteral(new char[] {'1'}, null), 0, 0));
 			FieldReference thisDotField = new FieldReference(data.getPluralName(), 0L);
-			thisDotField.receiver = new ThisReference(0, 0);
+			thisDotField.receiver = getBuilderReference(builderVariable);
 			MessageSend thisDotFieldGet0 = new MessageSend();
 			thisDotFieldGet0.receiver = thisDotField;
 			thisDotFieldGet0.selector = new char[] {'g', 'e', 't'};
@@ -97,7 +96,7 @@ public class EclipseJavaUtilListSingularizer extends EclipseJavaUtilListSetSingu
 			Expression argToUnmodifiable;
 			/* new j.u.ArrayList<Generics>(this.pluralName); */ {
 				FieldReference thisDotPluralName = new FieldReference(data.getPluralName(), 0L);
-				thisDotPluralName.receiver = new ThisReference(0, 0);
+				thisDotPluralName.receiver = getBuilderReference(builderVariable);
 				TypeReference targetTypeExpr = new QualifiedTypeReference(JAVA_UTIL_ARRAYLIST, NULL_POSS);
 				targetTypeExpr = addTypeArgs(1, false, builderType, targetTypeExpr, data.getTypeArgs());
 				AllocationExpression constructorCall = new AllocationExpression();
@@ -117,7 +116,7 @@ public class EclipseJavaUtilListSingularizer extends EclipseJavaUtilListSetSingu
 		
 		SwitchStatement switchStat = new SwitchStatement();
 		switchStat.statements = switchContents.toArray(new Statement[switchContents.size()]);
-		switchStat.expression = getSize(builderType, data.getPluralName(), true);
+		switchStat.expression = getSize(builderType, data.getPluralName(), true, builderVariable);
 		
 		TypeReference localShadowerType = new QualifiedTypeReference(Eclipse.fromQualifiedName(data.getTargetFqn()), NULL_POSS);
 		localShadowerType = addTypeArgs(1, false, builderType, localShadowerType, data.getTypeArgs());

src/core/lombok/eclipse/handlers/singulars/EclipseJavaUtilMapSingularizer.java

@@ -298,16 +298,16 @@ public class EclipseJavaUtilMapSingularizer extends EclipseJavaUtilSingularizer
 		injectMethod(builderType, md);
 	}
 	
-	@Override public void appendBuildCode(SingularData data, EclipseNode builderType, List<Statement> statements, char[] targetVariableName) {
+	@Override public void appendBuildCode(SingularData data, EclipseNode builderType, List<Statement> statements, char[] targetVariableName, String builderVariable) {
 		if (useGuavaInstead(builderType)) {
-			guavaMapSingularizer.appendBuildCode(data, builderType, statements, targetVariableName);
+			guavaMapSingularizer.appendBuildCode(data, builderType, statements, targetVariableName, builderVariable);
 			return;
 		}
 		
 		if (data.getTargetFqn().equals("java.util.Map")) {
-			statements.addAll(createJavaUtilSetMapInitialCapacitySwitchStatements(data, builderType, true, "emptyMap", "singletonMap", "LinkedHashMap"));
+			statements.addAll(createJavaUtilSetMapInitialCapacitySwitchStatements(data, builderType, true, "emptyMap", "singletonMap", "LinkedHashMap", builderVariable));
 		} else {
-			statements.addAll(createJavaUtilSimpleCreationAndFillStatements(data, builderType, true, true, false, true, "TreeMap"));
+			statements.addAll(createJavaUtilSimpleCreationAndFillStatements(data, builderType, true, true, false, true, "TreeMap", builderVariable));
 		}
 	}
 }

src/core/lombok/eclipse/handlers/singulars/EclipseJavaUtilSetSingularizer.java

@@ -37,16 +37,16 @@ public class EclipseJavaUtilSetSingularizer extends EclipseJavaUtilListSetSingul
 		return LombokImmutableList.of("java.util.Set", "java.util.SortedSet", "java.util.NavigableSet");
 	}
 	
-	@Override public void appendBuildCode(SingularData data, EclipseNode builderType, List<Statement> statements, char[] targetVariableName) {
+	@Override public void appendBuildCode(SingularData data, EclipseNode builderType, List<Statement> statements, char[] targetVariableName, String builderVariable) {
 		if (useGuavaInstead(builderType)) {
-			guavaListSetSingularizer.appendBuildCode(data, builderType, statements, targetVariableName);
+			guavaListSetSingularizer.appendBuildCode(data, builderType, statements, targetVariableName, builderVariable);
 			return;
 		}
 		
 		if (data.getTargetFqn().equals("java.util.Set")) {
-			statements.addAll(createJavaUtilSetMapInitialCapacitySwitchStatements(data, builderType, false, "emptySet", "singleton", "LinkedHashSet"));
+			statements.addAll(createJavaUtilSetMapInitialCapacitySwitchStatements(data, builderType, false, "emptySet", "singleton", "LinkedHashSet", builderVariable));
 		} else {
-			statements.addAll(createJavaUtilSimpleCreationAndFillStatements(data, builderType, false, true, false, true, "TreeSet"));
+			statements.addAll(createJavaUtilSimpleCreationAndFillStatements(data, builderType, false, true, false, true, "TreeSet", builderVariable));
 		}
 	}
 }

src/core/lombok/eclipse/handlers/singulars/EclipseJavaUtilSingularizer.java

@@ -90,7 +90,7 @@ abstract class EclipseJavaUtilSingularizer extends EclipseSingularizer {
 		return Boolean.TRUE.equals(node.getAst().readConfiguration(ConfigurationKeys.SINGULAR_USE_GUAVA));
 	}
 	
-	protected List<Statement> createJavaUtilSetMapInitialCapacitySwitchStatements(SingularData data, EclipseNode builderType, boolean mapMode, String emptyCollectionMethod, String singletonCollectionMethod, String targetType) {
+	protected List<Statement> createJavaUtilSetMapInitialCapacitySwitchStatements(SingularData data, EclipseNode builderType, boolean mapMode, String emptyCollectionMethod, String singletonCollectionMethod, String targetType, String builderVariable) {
 		List<Statement> switchContents = new ArrayList<Statement>();
 		char[] keyName = mapMode ? (new String(data.getPluralName()) + "$key").toCharArray() : data.getPluralName();
 		
@@ -112,7 +112,7 @@ abstract class EclipseJavaUtilSingularizer extends EclipseSingularizer {
 			/* !mapMode: pluralName = java.util.Collections.singletonCollectionMethod(this.pluralName.get(0));
 			   mapMode: pluralName = java.util.Collections.singletonCollectionMethod(this.pluralName$key.get(0), this.pluralName$value.get(0)); */ {
 				FieldReference thisDotKey = new FieldReference(keyName, 0L);
-				thisDotKey.receiver = new ThisReference(0, 0);
+				thisDotKey.receiver = getBuilderReference(builderVariable);
 				MessageSend thisDotKeyGet0 = new MessageSend();
 				thisDotKeyGet0.receiver = thisDotKey;
 				thisDotKeyGet0.selector = new char[] {'g', 'e', 't'};
@@ -122,7 +122,7 @@ abstract class EclipseJavaUtilSingularizer extends EclipseSingularizer {
 				if (mapMode) {
 					char[] valueName = (new String(data.getPluralName()) + "$value").toCharArray();
 					FieldReference thisDotValue = new FieldReference(valueName, 0L);
-					thisDotValue.receiver = new ThisReference(0, 0);
+					thisDotValue.receiver = getBuilderReference(builderVariable);
 					MessageSend thisDotValueGet0 = new MessageSend();
 					thisDotValueGet0.receiver = thisDotValue;
 					thisDotValueGet0.selector = new char[] {'g', 'e', 't'};
@@ -143,12 +143,12 @@ abstract class EclipseJavaUtilSingularizer extends EclipseSingularizer {
 		
 		{ // default:
 			switchContents.add(new CaseStatement(null, 0, 0));
-			switchContents.addAll(createJavaUtilSimpleCreationAndFillStatements(data, builderType, mapMode, false, true, emptyCollectionMethod == null, targetType));
+			switchContents.addAll(createJavaUtilSimpleCreationAndFillStatements(data, builderType, mapMode, false, true, emptyCollectionMethod == null, targetType, builderVariable));
 		}
 		
 		SwitchStatement switchStat = new SwitchStatement();
 		switchStat.statements = switchContents.toArray(new Statement[switchContents.size()]);
-		switchStat.expression = getSize(builderType, keyName, true);
+		switchStat.expression = getSize(builderType, keyName, true, builderVariable);
 		
 		TypeReference localShadowerType = new QualifiedTypeReference(fromQualifiedName(data.getTargetFqn()), NULL_POSS);
 		localShadowerType = addTypeArgs(mapMode ? 2 : 1, false, builderType, localShadowerType, data.getTypeArgs());
@@ -157,7 +157,7 @@ abstract class EclipseJavaUtilSingularizer extends EclipseSingularizer {
 		return Arrays.asList(varDefStat, switchStat);
 	}
 	
-	protected List<Statement> createJavaUtilSimpleCreationAndFillStatements(SingularData data, EclipseNode builderType, boolean mapMode, boolean defineVar, boolean addInitialCapacityArg, boolean nullGuard, String targetType) {
+	protected List<Statement> createJavaUtilSimpleCreationAndFillStatements(SingularData data, EclipseNode builderType, boolean mapMode, boolean defineVar, boolean addInitialCapacityArg, boolean nullGuard, String targetType, String builderVariable) {
 		char[] varName = mapMode ? (new String(data.getPluralName()) + "$key").toCharArray() : data.getPluralName();
 		
 		Statement createStat; {
@@ -166,11 +166,11 @@ abstract class EclipseJavaUtilSingularizer extends EclipseSingularizer {
 			if (addInitialCapacityArg) {
 				// this.varName.size() < MAX_POWER_OF_2 ? 1 + this.varName.size() + (this.varName.size() - 3) / 3 : Integer.MAX_VALUE;
 				// lessThanCutOff = this.varName.size() < MAX_POWER_OF_2
-				Expression lessThanCutoff = new BinaryExpression(getSize(builderType, varName, nullGuard), makeIntLiteral("0x40000000".toCharArray(), null), OperatorIds.LESS);
+				Expression lessThanCutoff = new BinaryExpression(getSize(builderType, varName, nullGuard, builderVariable), makeIntLiteral("0x40000000".toCharArray(), null), OperatorIds.LESS);
 				FieldReference integerMaxValue = new FieldReference("MAX_VALUE".toCharArray(), 0L);
 				integerMaxValue.receiver = new QualifiedNameReference(TypeConstants.JAVA_LANG_INTEGER, NULL_POSS, 0, 0);
-				Expression sizeFormulaLeft = new BinaryExpression(makeIntLiteral(new char[] {'1'}, null), getSize(builderType, varName, nullGuard), OperatorIds.PLUS);
-				Expression sizeFormulaRightLeft = new BinaryExpression(getSize(builderType, varName, nullGuard), makeIntLiteral(new char[] {'3'}, null), OperatorIds.MINUS);
+				Expression sizeFormulaLeft = new BinaryExpression(makeIntLiteral(new char[] {'1'}, null), getSize(builderType, varName, nullGuard, builderVariable), OperatorIds.PLUS);
+				Expression sizeFormulaRightLeft = new BinaryExpression(getSize(builderType, varName, nullGuard, builderVariable), makeIntLiteral(new char[] {'3'}, null), OperatorIds.MINUS);
 				Expression sizeFormulaRight = new BinaryExpression(sizeFormulaRightLeft, makeIntLiteral(new char[] {'3'}, null), OperatorIds.DIVIDE);
 				Expression sizeFormula = new BinaryExpression(sizeFormulaLeft, sizeFormulaRight, OperatorIds.PLUS);
 				Expression cond = new ConditionalExpression(lessThanCutoff, sizeFormula, integerMaxValue);
@@ -203,9 +203,9 @@ abstract class EclipseJavaUtilSingularizer extends EclipseSingularizer {
 				pluralnameDotPut.selector = new char[] {'p', 'u', 't'};
 				pluralnameDotPut.receiver = new SingleNameReference(data.getPluralName(), 0L);
 				FieldReference thisDotKey = new FieldReference(varName, 0L);
-				thisDotKey.receiver = new ThisReference(0, 0);
+				thisDotKey.receiver = getBuilderReference(builderVariable);
 				FieldReference thisDotValue = new FieldReference((new String(data.getPluralName()) + "$value").toCharArray(), 0L);
-				thisDotValue.receiver = new ThisReference(0, 0);
+				thisDotValue.receiver = getBuilderReference(builderVariable);
 				MessageSend keyArg = new MessageSend();
 				keyArg.receiver = thisDotKey;
 				keyArg.arguments = new Expression[] {new SingleNameReference(iVar, 0L)};
@@ -219,7 +219,7 @@ abstract class EclipseJavaUtilSingularizer extends EclipseSingularizer {
 				LocalDeclaration forInit = new LocalDeclaration(iVar, 0, 0);
 				forInit.type = TypeReference.baseTypeReference(TypeIds.T_int, 0);
 				forInit.initialization = makeIntLiteral(new char[] {'0'}, null);
-				Expression checkExpr = new BinaryExpression(new SingleNameReference(iVar, 0L), getSize(builderType, varName, nullGuard), OperatorIds.LESS);
+				Expression checkExpr = new BinaryExpression(new SingleNameReference(iVar, 0L), getSize(builderType, varName, nullGuard, builderVariable), OperatorIds.LESS);
 				Expression incrementExpr = new PostfixExpression(new SingleNameReference(iVar, 0L), IntLiteral.One, OperatorIds.PLUS, 0);
 				fillStat = new ForStatement(new Statement[] {forInit}, checkExpr, new Statement[] {incrementExpr}, pluralnameDotPut, true, 0, 0);
 			} else {
@@ -228,14 +228,14 @@ abstract class EclipseJavaUtilSingularizer extends EclipseSingularizer {
 				pluralnameDotAddAll.selector = new char[] {'a', 'd', 'd', 'A', 'l', 'l'};
 				pluralnameDotAddAll.receiver = new SingleNameReference(data.getPluralName(), 0L);
 				FieldReference thisDotPluralname = new FieldReference(varName, 0L);
-				thisDotPluralname.receiver = new ThisReference(0, 0);
+				thisDotPluralname.receiver = getBuilderReference(builderVariable);
 				pluralnameDotAddAll.arguments = new Expression[] {thisDotPluralname};
 				fillStat = pluralnameDotAddAll;
 			}
 			
 			if (nullGuard) {
 				FieldReference thisDotField = new FieldReference(varName, 0L);
-				thisDotField.receiver = new ThisReference(0, 0);
+				thisDotField.receiver = getBuilderReference(builderVariable);
 				Expression cond = new EqualExpression(thisDotField, new NullLiteral(0, 0), OperatorIds.NOT_EQUAL);
 				fillStat = new IfStatement(cond, fillStat, 0, 0);
 			}

src/core/lombok/javac/handlers/HandleBuilder.java

@@ -39,6 +39,7 @@ 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.JCMethodInvocation;
 import com.sun.tools.javac.tree.JCTree.JCModifiers;
 import com.sun.tools.javac.tree.JCTree.JCPrimitiveTypeTree;
 import com.sun.tools.javac.tree.JCTree.JCStatement;
@@ -83,6 +84,7 @@ public class HandleBuilder extends JavacAnnotationHandler<Builder> {
 	}
 	
 	private static class BuilderFieldData {
+		JavacNode fieldNode;
 		JCExpression type;
 		Name rawName;
 		Name name;
@@ -107,6 +109,10 @@ public class HandleBuilder extends JavacAnnotationHandler<Builder> {
 		String buildMethodName = builderInstance.buildMethodName();
 		String builderClassName = builderInstance.builderClassName();
 		String toBuilderMethodName = "toBuilder";
+		
+		boolean inherit = builderInstance.inherit();
+		boolean extensible = inherit || builderInstance.extensible(); // inherit implies extendable
+		
 		boolean toBuilder = builderInstance.toBuilder();
 		java.util.List<Name> typeArgsForToBuilder = null;
 		
@@ -135,9 +141,11 @@ public class HandleBuilder extends JavacAnnotationHandler<Builder> {
 		boolean addCleaning = false;
 		boolean isStatic = true;
 		
+		JCClassDecl td = null;
+		
 		if (parent.get() instanceof JCClassDecl) {
 			tdParent = parent;
-			JCClassDecl td = (JCClassDecl) tdParent.get();
+			td = (JCClassDecl) tdParent.get();
 			ListBuffer<JavacNode> allFields = new ListBuffer<JavacNode>();
 			boolean valuePresent = (hasAnnotation(lombok.Value.class, parent) || hasAnnotation("lombok.experimental.Value", parent));
 			for (JavacNode fieldNode : HandleConstructor.findAllFields(tdParent, true)) {
@@ -145,6 +153,7 @@ public class HandleBuilder extends JavacAnnotationHandler<Builder> {
 				JavacNode isDefault = findAnnotation(Builder.Default.class, fieldNode, true);
 				boolean isFinal = (fd.mods.flags & Flags.FINAL) != 0 || (valuePresent && !hasAnnotation(NonFinal.class, fieldNode));
 				BuilderFieldData bfd = new BuilderFieldData();
+				bfd.fieldNode = fieldNode;
 				bfd.rawName = fd.name;
 				bfd.name = removePrefixFromField(fieldNode);
 				bfd.type = fd.vartype;
@@ -178,14 +187,30 @@ public class HandleBuilder extends JavacAnnotationHandler<Builder> {
 				allFields.append(fieldNode);
 			}
 			
-			handleConstructor.generateConstructor(tdParent, AccessLevel.PACKAGE, List.<JCAnnotation>nil(), allFields.toList(), false, null, SkipIfConstructorExists.I_AM_BUILDER, annotationNode);
+			if (builderClassName.isEmpty()) builderClassName = td.name.toString() + "Builder";
+			
+			JCTree extendsClause = Javac.getExtendsClause(td);
+			
+			if (extensible) {
+				boolean callBuilderBasedSuperConstructor = extendsClause != null;
+				generateBuilderBasedConstructor(tdParent, builderFields, annotationNode, builderClassName, callBuilderBasedSuperConstructor);
+			} else {
+				handleConstructor.generateConstructor(tdParent, AccessLevel.PROTECTED, List.<JCAnnotation>nil(), allFields.toList(), false, null, SkipIfConstructorExists.I_AM_BUILDER, annotationNode);
+			}
 			
 			returnType = namePlusTypeParamsToTypeReference(tdParent.getTreeMaker(), td.name, td.typarams);
 			typeParams = td.typarams;
 			thrownExceptions = List.nil();
 			nameOfBuilderMethod = null;
-			if (builderClassName.isEmpty()) builderClassName = td.name.toString() + "Builder";
 		} else if (fillParametersFrom != null && fillParametersFrom.getName().toString().equals("<init>")) {
+			if (inherit) {
+				annotationNode.addError("@Builder(inherit=true) is only supported for type builders.");
+				return;
+			}
+			if (extensible) {
+				annotationNode.addError("@Builder(extendable=true) is only supported for type builders.");
+				return;
+			}
 			JCMethodDecl jmd = (JCMethodDecl) fillParametersFrom.get();
 			if (!jmd.typarams.isEmpty()) {
 				annotationNode.addError("@Builder is not supported on constructors with constructor type parameters.");
@@ -193,15 +218,23 @@ public class HandleBuilder extends JavacAnnotationHandler<Builder> {
 			}
 			
 			tdParent = parent.up();
-			JCClassDecl td = (JCClassDecl) tdParent.get();
+			td = (JCClassDecl) tdParent.get();
 			returnType = namePlusTypeParamsToTypeReference(tdParent.getTreeMaker(), td.name, td.typarams);
 			typeParams = td.typarams;
 			thrownExceptions = jmd.thrown;
 			nameOfBuilderMethod = null;
 			if (builderClassName.isEmpty()) builderClassName = td.name.toString() + "Builder";
 		} else if (fillParametersFrom != null) {
+			if (inherit) {
+				annotationNode.addError("@Builder(inherit=true) is only supported for type builders.");
+				return;
+			}
+			if (extensible) {
+				annotationNode.addError("@Builder(extendable=true) is only supported for type builders.");
+				return;
+			}
 			tdParent = parent.up();
-			JCClassDecl td = (JCClassDecl) tdParent.get();
+			td = (JCClassDecl) tdParent.get();
 			JCMethodDecl jmd = (JCMethodDecl) fillParametersFrom.get();
 			isStatic = (jmd.mods.flags & Flags.STATIC) != 0;
 			JCExpression fullReturnType = jmd.restype;
@@ -333,7 +366,18 @@ public class HandleBuilder extends JavacAnnotationHandler<Builder> {
 		
 		JavacNode builderType = findInnerClass(tdParent, builderClassName);
 		if (builderType == null) {
-			builderType = makeBuilderClass(isStatic, annotationNode, tdParent, builderClassName, typeParams, ast);
+			String superclassBuilderClassName = null;
+			if (inherit) {
+				JCTree extendsClause = Javac.getExtendsClause(td);
+				if (extendsClause == null) {
+					annotationNode.addError("@Builder(inherit = true) requires that your class has an 'extends' clause.");
+					return;
+				}
+				
+				superclassBuilderClassName = builderInstance.superclassBuilderClassName();
+				if (superclassBuilderClassName == null || superclassBuilderClassName.isEmpty()) superclassBuilderClassName = extendsClause + "Builder";
+			}
+			builderType = makeBuilderClass(isStatic, annotationNode, tdParent, builderClassName, typeParams, ast, superclassBuilderClassName);
 		} else {
 			JCClassDecl builderTypeDeclaration = (JCClassDecl) builderType.get();
 			if (isStatic && !builderTypeDeclaration.getModifiers().getFlags().contains(Modifier.STATIC)) {
@@ -393,7 +437,7 @@ public class HandleBuilder extends JavacAnnotationHandler<Builder> {
 		}
 		
 		if (methodExists(buildMethodName, builderType, -1) == MemberExistsResult.NOT_EXISTS) {
-			JCMethodDecl md = generateBuildMethod(tdParent, isStatic, buildMethodName, nameOfBuilderMethod, returnType, builderFields, builderType, thrownExceptions, ast, addCleaning);
+			JCMethodDecl md = generateBuildMethod(tdParent, isStatic, buildMethodName, nameOfBuilderMethod, returnType, builderFields, builderType, thrownExceptions, ast, addCleaning, extensible);
 			if (md != null) injectMethod(builderType, md);
 		}
 		
@@ -502,6 +546,82 @@ public class HandleBuilder extends JavacAnnotationHandler<Builder> {
 		JCBlock body = maker.Block(0, List.<JCStatement>of(statement));
 		return maker.MethodDef(maker.Modifiers(Flags.PUBLIC), type.toName(toBuilderMethodName), namePlusTypeParamsToTypeReference(maker, type.toName(builderClassName), typeParams), List.<JCTypeParameter>nil(), List.<JCVariableDecl>nil(), List.<JCExpression>nil(), body, null);
 	}
+
+	/**
+	 * Generates a constructor that has a builder as the only parameter.
+	 * The values from the builder are used to initialize the fields of new instances.
+	 *
+	 * @param typeNode
+	 *            the type (with the {@code @Builder} annotation) for which a
+	 *            constructor should be generated.
+	 * @param builderFields a list of fields in the builder which should be assigned to new instances.
+	 * @param source the annotation (used for setting source code locations for the generated code).
+	 * @param builderClassnameAsParameter
+	 *            If {@code != null}, the only parameter of the constructor will
+	 *            be a builder with this classname; the constructor will then
+	 *            use the values within this builder to assign the fields of new
+	 *            instances.
+	 * @param callBuilderBasedSuperConstructor
+	 *            If {@code true}, the constructor will explicitly call a super
+	 *            constructor with the builder as argument. Requires
+	 *            {@code builderClassAsParameter != null}.
+	 */
+	private void generateBuilderBasedConstructor(JavacNode typeNode, java.util.List<BuilderFieldData> builderFields, JavacNode source, String builderClassnameAsParameter, boolean callBuilderBasedSuperConstructor) {
+		JavacTreeMaker maker = typeNode.getTreeMaker();
+		
+		boolean isEnum = (((JCClassDecl) typeNode.get()).mods.flags & Flags.ENUM) != 0;
+		AccessLevel level = isEnum ? AccessLevel.PRIVATE : AccessLevel.PROTECTED;
+		
+		ListBuffer<JCStatement> nullChecks = new ListBuffer<JCStatement>();
+		ListBuffer<JCStatement> statements = new ListBuffer<JCStatement>();
+		
+		Name builderVariableName = typeNode.toName("b");
+		for (BuilderFieldData bfd : builderFields) {
+			List<JCAnnotation> nonNulls = findAnnotations(bfd.fieldNode, NON_NULL_PATTERN);
+			if (!nonNulls.isEmpty()) {
+				JCStatement nullCheck = generateNullCheck(maker, bfd.fieldNode, source);
+				if (nullCheck != null) {
+					nullChecks.append(nullCheck);
+				}
+			}
+			
+			JCExpression rhs;
+			if (bfd.singularData != null && bfd.singularData.getSingularizer() != null) {
+				bfd.singularData.getSingularizer().appendBuildCode(bfd.singularData, bfd.fieldNode, bfd.type, statements, bfd.name, "b");
+				rhs = maker.Ident(bfd.singularData.getPluralName());
+			} else {
+				rhs = maker.Select(maker.Ident(builderVariableName), bfd.rawName);
+			}
+			JCFieldAccess thisX = maker.Select(maker.Ident(bfd.fieldNode.toName("this")), bfd.rawName);
+			
+			JCExpression assign = maker.Assign(thisX, rhs);
+				
+			statements.append(maker.Exec(assign));
+		}
+		
+		JCModifiers mods = maker.Modifiers(toJavacModifier(level), List.<JCAnnotation>nil());
+		
+		// Create a constructor that has just the builder as parameter.
+		ListBuffer<JCVariableDecl> params = new ListBuffer<JCVariableDecl>();
+		long flags = JavacHandlerUtil.addFinalIfNeeded(Flags.PARAMETER, typeNode.getContext());
+		Name builderClassname = typeNode.toName(builderClassnameAsParameter);
+		JCVariableDecl param = maker.VarDef(maker.Modifiers(flags), builderVariableName, maker.Ident(builderClassname), null);
+		params.append(param);
+
+		if (callBuilderBasedSuperConstructor) {
+			// The first statement must be the call to the super constructor.
+			JCMethodInvocation callToSuperConstructor = maker.Apply(List.<JCExpression>nil(),
+					maker.Ident(typeNode.toName("super")),
+					List.<JCExpression>of(maker.Ident(builderVariableName)));
+			statements.prepend(maker.Exec(callToSuperConstructor));
+		}
+		
+		JCMethodDecl constr = recursiveSetGeneratedBy(maker.MethodDef(mods, typeNode.toName("<init>"),
+			null, List.<JCTypeParameter>nil(), params.toList(), List.<JCExpression>nil(),
+			maker.Block(0L, nullChecks.appendList(statements).toList()), null), source.get(), typeNode.getContext());
+		
+		injectMethod(typeNode, constr, null, Javac.createVoidType(typeNode.getSymbolTable(), CTC_VOID));
+	}
 	
 	private JCMethodDecl generateCleanMethod(java.util.List<BuilderFieldData> builderFields, JavacNode type, JCTree source) {
 		JavacTreeMaker maker = type.getTreeMaker();
@@ -530,40 +650,56 @@ public class HandleBuilder extends JavacAnnotationHandler<Builder> {
 		 */
 	}
 	
-	private JCMethodDecl generateBuildMethod(JavacNode tdParent, boolean isStatic, String buildName, Name builderName, JCExpression returnType, java.util.List<BuilderFieldData> builderFields, JavacNode type, List<JCExpression> thrownExceptions, JCTree source, boolean addCleaning) {
+	/**
+	 * @param useBuilderBasedConstructor
+	 *            if true, the {@code build()} method will use a constructor
+	 *            that takes the builder instance as parameter (instead of a
+	 *            constructor with all relevant fields as parameters)
+	 */
+	private JCMethodDecl generateBuildMethod(JavacNode tdParent, boolean isStatic, String buildName, Name builderName, JCExpression returnType, java.util.List<BuilderFieldData> builderFields, JavacNode type, List<JCExpression> thrownExceptions, JCTree source, boolean addCleaning, boolean useBuilderBasedConstructor) {
 		JavacTreeMaker maker = type.getTreeMaker();
 		
 		JCExpression call;
 		ListBuffer<JCStatement> statements = new ListBuffer<JCStatement>();
-		
-		if (addCleaning) {
-			JCExpression notClean = maker.Unary(CTC_NOT, maker.Select(maker.Ident(type.toName("this")), type.toName("$lombokUnclean")));
-			JCStatement invokeClean = maker.Exec(maker.Apply(List.<JCExpression>nil(), maker.Ident(type.toName("$lombokClean")), List.<JCExpression>nil()));
-			JCIf ifUnclean = maker.If(notClean, invokeClean, null);
-			statements.append(ifUnclean);
-		}
-		
-		for (BuilderFieldData bfd : builderFields) {
-			if (bfd.singularData != null && bfd.singularData.getSingularizer() != null) {
-				bfd.singularData.getSingularizer().appendBuildCode(bfd.singularData, type, source, statements, bfd.name);
-			}
-		}
-		
 		ListBuffer<JCExpression> args = new ListBuffer<JCExpression>();
-		for (BuilderFieldData bfd : builderFields) {
-			if (bfd.nameOfSetFlag != null) {
-				statements.append(maker.VarDef(maker.Modifiers(0L), bfd.name, cloneType(maker, bfd.type, source, tdParent.getContext()), maker.Select(maker.Ident(type.toName("this")), bfd.name)));
-				statements.append(maker.If(maker.Unary(CTC_NOT, maker.Ident(bfd.nameOfSetFlag)), maker.Exec(maker.Assign(maker.Ident(bfd.name),maker.Apply(typeParameterNames(maker, ((JCClassDecl) tdParent.get()).typarams), maker.Select(maker.Ident(((JCClassDecl) tdParent.get()).name), bfd.nameOfDefaultProvider), List.<JCExpression>nil()))), null));
-			}
-			args.append(maker.Ident(bfd.name));
-		}
 		
-		if (addCleaning) {
-			statements.append(maker.Exec(maker.Assign(maker.Select(maker.Ident(type.toName("this")), type.toName("$lombokUnclean")), maker.Literal(CTC_BOOLEAN, 1))));
+		// Extendable builders assign their values in the constructor, not in this build() method.
+		if (!useBuilderBasedConstructor) {
+			if (addCleaning) {
+				JCExpression notClean = maker.Unary(CTC_NOT, maker.Select(maker.Ident(type.toName("this")), type.toName("$lombokUnclean")));
+				JCStatement invokeClean = maker.Exec(maker.Apply(List.<JCExpression>nil(), maker.Ident(type.toName("$lombokClean")), List.<JCExpression>nil()));
+				JCIf ifUnclean = maker.If(notClean, invokeClean, null);
+				statements.append(ifUnclean);
+			}
+			
+			for (BuilderFieldData bfd : builderFields) {
+				if (bfd.singularData != null && bfd.singularData.getSingularizer() != null) {
+					bfd.singularData.getSingularizer().appendBuildCode(bfd.singularData, type, source, statements, bfd.name, "this");
+				}
+			}
+			
+			for (BuilderFieldData bfd : builderFields) {
+				if (bfd.nameOfSetFlag != null) {
+					statements.append(maker.VarDef(maker.Modifiers(0L), bfd.name, cloneType(maker, bfd.type, source, tdParent.getContext()), maker.Select(maker.Ident(type.toName("this")), bfd.name)));
+					statements.append(maker.If(maker.Unary(CTC_NOT, maker.Ident(bfd.nameOfSetFlag)), maker.Exec(maker.Assign(maker.Ident(bfd.name),maker.Apply(typeParameterNames(maker, ((JCClassDecl) tdParent.get()).typarams), maker.Select(maker.Ident(((JCClassDecl) tdParent.get()).name), bfd.nameOfDefaultProvider), List.<JCExpression>nil()))), null));
+				}
+				args.append(maker.Ident(bfd.name));
+			}
+			
+			if (addCleaning) {
+				statements.append(maker.Exec(maker.Assign(maker.Select(maker.Ident(type.toName("this")), type.toName("$lombokUnclean")), maker.Literal(CTC_BOOLEAN, 1))));
+			}
 		}
 		
 		if (builderName == null) {
-			call = maker.NewClass(null, List.<JCExpression>nil(), returnType, args.toList(), null);
+			if (useBuilderBasedConstructor) {
+				// Use a constructor that only has this builder as parameter.
+				List<JCExpression> builderArg = List.<JCExpression>of(maker.Ident(type.toName("this")));
+				call = maker.NewClass(null, List.<JCExpression>nil(), returnType, builderArg, null);
+			} else {
+				// Use a constructor with all the fields.
+				call = maker.NewClass(null, List.<JCExpression>nil(), returnType, args.toList(), null);
+			}
 			statements.append(maker.Return(call));
 		} else {
 			ListBuffer<JCExpression> typeParams = new ListBuffer<JCExpression>();
@@ -686,12 +822,13 @@ public class HandleBuilder extends JavacAnnotationHandler<Builder> {
 		return null;
 	}
 	
-	public JavacNode makeBuilderClass(boolean isStatic, JavacNode source, JavacNode tdParent, String builderClassName, List<JCTypeParameter> typeParams, JCAnnotation ast) {
+	public JavacNode makeBuilderClass(boolean isStatic, JavacNode source, JavacNode tdParent, String builderClassName, List<JCTypeParameter> typeParams, JCAnnotation ast, String parentBuilderClassName) {
 		JavacTreeMaker maker = tdParent.getTreeMaker();
 		int modifiers = Flags.PUBLIC;
 		if (isStatic) modifiers |= Flags.STATIC;
 		JCModifiers mods = maker.Modifiers(modifiers);
-		JCClassDecl builder = maker.ClassDef(mods, tdParent.toName(builderClassName), copyTypeParams(source, typeParams), null, List.<JCExpression>nil(), List.<JCTree>nil());
+		JCExpression extending = parentBuilderClassName == null ?  null : maker.Ident(tdParent.toName(parentBuilderClassName));
+		JCClassDecl builder = maker.ClassDef(mods, tdParent.toName(builderClassName), copyTypeParams(source, typeParams), extending, List.<JCExpression>nil(), List.<JCTree>nil());
 		return injectType(tdParent, builder);
 	}
 	

src/core/lombok/javac/handlers/JavacSingularsRecipes.java

@@ -195,7 +195,7 @@ public class JavacSingularsRecipes {
 		
 		public abstract java.util.List<JavacNode> generateFields(SingularData data, JavacNode builderType, JCTree source);
 		public abstract void generateMethods(SingularData data, boolean deprecate, JavacNode builderType, JCTree source, boolean fluent, boolean chain);
-		public abstract void appendBuildCode(SingularData data, JavacNode builderType, JCTree source, ListBuffer<JCStatement> statements, Name targetVariableName);
+		public abstract void appendBuildCode(SingularData data, JavacNode builderType, JCTree source, ListBuffer<JCStatement> statements, Name targetVariableName, String builderVariable);
 		
 		public boolean requiresCleaning() {
 			try {
@@ -274,9 +274,9 @@ public class JavacSingularsRecipes {
 			return arguments.toList();
 		}
 		
-		/** Generates 'this.<em>name</em>.size()' as an expression; if nullGuard is true, it's this.name == null ? 0 : this.name.size(). */
-		protected JCExpression getSize(JavacTreeMaker maker, JavacNode builderType, Name name, boolean nullGuard, boolean parens) {
-			Name thisName = builderType.toName("this");
+		/** Generates '<em>builderVariable</em>.<em>name</em>.size()' as an expression; if nullGuard is true, it's this.name == null ? 0 : this.name.size(). */
+		protected JCExpression getSize(JavacTreeMaker maker, JavacNode builderType, Name name, boolean nullGuard, boolean parens, String builderVariable) {
+			Name thisName = builderType.toName(builderVariable);
 			JCExpression fn = maker.Select(maker.Select(maker.Ident(thisName), name), builderType.toName("size"));
 			JCExpression sizeInvoke = maker.Apply(List.<JCExpression>nil(), fn, List.<JCExpression>nil());
 			if (nullGuard) {

src/core/lombok/javac/handlers/singulars/JavacGuavaSingularizer.java

@@ -168,7 +168,7 @@ abstract class JavacGuavaSingularizer extends JavacSingularizer {
 		injectMethod(builderType, method);
 	}
 	
-	@Override public void appendBuildCode(SingularData data, JavacNode builderType, JCTree source, ListBuffer<JCStatement> statements, Name targetVariableName) {
+	@Override public void appendBuildCode(SingularData data, JavacNode builderType, JCTree source, ListBuffer<JCStatement> statements, Name targetVariableName, String builderVariable) {
 		JavacTreeMaker maker = builderType.getTreeMaker();
 		List<JCExpression> jceBlank = List.nil();
 		
@@ -185,12 +185,12 @@ abstract class JavacGuavaSingularizer extends JavacSingularizer {
 		
 		JCExpression invokeBuild; {
 			//this.pluralName.build();
-			invokeBuild = maker.Apply(jceBlank, chainDots(builderType, "this", data.getPluralName().toString(), "build"), jceBlank);
+			invokeBuild = maker.Apply(jceBlank, chainDots(builderType, builderVariable, data.getPluralName().toString(), "build"), jceBlank);
 		}
 		
 		JCExpression isNull; {
 			//this.pluralName == null
-			isNull = maker.Binary(CTC_EQUAL, maker.Select(maker.Ident(builderType.toName("this")), data.getPluralName()), maker.Literal(CTC_BOT, null));
+			isNull = maker.Binary(CTC_EQUAL, maker.Select(maker.Ident(builderType.toName(builderVariable)), data.getPluralName()), maker.Literal(CTC_BOT, null));
 		}
 		
 		JCExpression init = maker.Conditional(isNull, empty, invokeBuild); // this.pluralName == null ? ImmutableX.of() : this.pluralName.build()

src/core/lombok/javac/handlers/singulars/JavacJavaUtilListSingularizer.java

@@ -46,9 +46,9 @@ public class JavacJavaUtilListSingularizer extends JavacJavaUtilListSetSingulari
 		return LombokImmutableList.of("java.util.List", "java.util.Collection", "java.lang.Iterable");
 	}
 	
-	@Override public void appendBuildCode(SingularData data, JavacNode builderType, JCTree source, ListBuffer<JCStatement> statements, Name targetVariableName) {
+	@Override public void appendBuildCode(SingularData data, JavacNode builderType, JCTree source, ListBuffer<JCStatement> statements, Name targetVariableName, String builderVariable) {
 		if (useGuavaInstead(builderType)) {
-			guavaListSetSingularizer.appendBuildCode(data, builderType, source, statements, targetVariableName);
+			guavaListSetSingularizer.appendBuildCode(data, builderType, source, statements, targetVariableName, builderVariable);
 			return;
 		}
 		
@@ -71,7 +71,7 @@ public class JavacJavaUtilListSingularizer extends JavacJavaUtilListSetSingulari
 			JCStatement assignStat; {
 				// pluralName = java.util.Collections.singletonList(this.pluralName.get(0));
 				JCExpression zeroLiteral = maker.Literal(CTC_INT, 0);
-				JCExpression arg = maker.Apply(jceBlank, chainDots(builderType, "this", data.getPluralName().toString(), "get"), List.of(zeroLiteral));
+				JCExpression arg = maker.Apply(jceBlank, chainDots(builderType, builderVariable, data.getPluralName().toString(), "get"), List.of(zeroLiteral));
 				List<JCExpression> args = List.of(arg);
 				JCExpression invoke = maker.Apply(jceBlank, chainDots(builderType, "java", "util", "Collections", "singletonList"), args);
 				assignStat = maker.Exec(maker.Assign(maker.Ident(data.getPluralName()), invoke));
@@ -82,12 +82,12 @@ public class JavacJavaUtilListSingularizer extends JavacJavaUtilListSetSingulari
 		}
 		
 		/* default: Create with right size, then addAll */ {
-			List<JCStatement> defStats = createListCopy(maker, data, builderType, source);
+			List<JCStatement> defStats = createListCopy(maker, data, builderType, source, builderVariable);
 			JCCase defaultCase = maker.Case(null, defStats);
 			cases.append(defaultCase);
 		}
 		
-		JCStatement switchStat = maker.Switch(getSize(maker,  builderType, data.getPluralName(), true, false), cases.toList());
+		JCStatement switchStat = maker.Switch(getSize(maker,  builderType, data.getPluralName(), true, false, builderVariable), cases.toList());
 		JCExpression localShadowerType = chainDotsString(builderType, data.getTargetFqn());
 		localShadowerType = addTypeArgs(1, false, builderType, localShadowerType, data.getTypeArgs(), source);
 		JCStatement varDefStat = maker.VarDef(maker.Modifiers(0), data.getPluralName(), localShadowerType, null);
@@ -95,9 +95,9 @@ public class JavacJavaUtilListSingularizer extends JavacJavaUtilListSetSingulari
 		statements.append(switchStat);
 	}
 	
-	private List<JCStatement> createListCopy(JavacTreeMaker maker, SingularData data, JavacNode builderType, JCTree source) {
+	private List<JCStatement> createListCopy(JavacTreeMaker maker, SingularData data, JavacNode builderType, JCTree source, String builderVariable) {
 		List<JCExpression> jceBlank = List.nil();
-		Name thisName = builderType.toName("this");
+		Name thisName = builderType.toName(builderVariable);
 		
 		JCExpression argToUnmodifiable; {
 			 // new java.util.ArrayList<Generics>(this.pluralName);

src/core/lombok/javac/handlers/singulars/JavacJavaUtilMapSingularizer.java

@@ -212,18 +212,18 @@ public class JavacJavaUtilMapSingularizer extends JavacJavaUtilSingularizer {
 		injectMethod(builderType, method);
 	}
 	
-	@Override public void appendBuildCode(SingularData data, JavacNode builderType, JCTree source, ListBuffer<JCStatement> statements, Name targetVariableName) {
+	@Override public void appendBuildCode(SingularData data, JavacNode builderType, JCTree source, ListBuffer<JCStatement> statements, Name targetVariableName, String builderVariable) {
 		if (useGuavaInstead(builderType)) {
-			guavaMapSingularizer.appendBuildCode(data, builderType, source, statements, targetVariableName);
+			guavaMapSingularizer.appendBuildCode(data, builderType, source, statements, targetVariableName, builderVariable);
 			return;
 		}
 		
 		JavacTreeMaker maker = builderType.getTreeMaker();
 		
 		if (data.getTargetFqn().equals("java.util.Map")) {
-			statements.appendList(createJavaUtilSetMapInitialCapacitySwitchStatements(maker, data, builderType, true, "emptyMap", "singletonMap", "LinkedHashMap", source));
+			statements.appendList(createJavaUtilSetMapInitialCapacitySwitchStatements(maker, data, builderType, true, "emptyMap", "singletonMap", "LinkedHashMap", source, builderVariable));
 		} else {
-			statements.appendList(createJavaUtilSimpleCreationAndFillStatements(maker, data, builderType, true, true, false, true, "TreeMap", source));
+			statements.appendList(createJavaUtilSimpleCreationAndFillStatements(maker, data, builderType, true, true, false, true, "TreeMap", source, builderVariable));
 		}
 	}
 }

src/core/lombok/javac/handlers/singulars/JavacJavaUtilSetSingularizer.java

@@ -40,18 +40,18 @@ public class JavacJavaUtilSetSingularizer extends JavacJavaUtilListSetSingulariz
 		return LombokImmutableList.of("java.util.Set", "java.util.SortedSet", "java.util.NavigableSet");
 	}
 	
-	@Override public void appendBuildCode(SingularData data, JavacNode builderType, JCTree source, ListBuffer<JCStatement> statements, Name targetVariableName) {
+	@Override public void appendBuildCode(SingularData data, JavacNode builderType, JCTree source, ListBuffer<JCStatement> statements, Name targetVariableName, String builderVariable) {
 		if (useGuavaInstead(builderType)) {
-			guavaListSetSingularizer.appendBuildCode(data, builderType, source, statements, targetVariableName);
+			guavaListSetSingularizer.appendBuildCode(data, builderType, source, statements, targetVariableName, builderVariable);
 			return;
 		}
 		
 		JavacTreeMaker maker = builderType.getTreeMaker();
 		
 		if (data.getTargetFqn().equals("java.util.Set")) {
-			statements.appendList(createJavaUtilSetMapInitialCapacitySwitchStatements(maker, data, builderType, false, "emptySet", "singleton", "LinkedHashSet", source));
+			statements.appendList(createJavaUtilSetMapInitialCapacitySwitchStatements(maker, data, builderType, false, "emptySet", "singleton", "LinkedHashSet", source, builderVariable));
 		} else {
-			statements.appendList(createJavaUtilSimpleCreationAndFillStatements(maker, data, builderType, false, true, false, true, "TreeSet", source));
+			statements.appendList(createJavaUtilSimpleCreationAndFillStatements(maker, data, builderType, false, true, false, true, "TreeSet", source, builderVariable));
 		}
 	}
 }

src/core/lombok/javac/handlers/singulars/JavacJavaUtilSingularizer.java

@@ -46,7 +46,7 @@ abstract class JavacJavaUtilSingularizer extends JavacSingularizer {
 		return Boolean.TRUE.equals(node.getAst().readConfiguration(ConfigurationKeys.SINGULAR_USE_GUAVA));
 	}
 	
-	protected List<JCStatement> createJavaUtilSetMapInitialCapacitySwitchStatements(JavacTreeMaker maker, SingularData data, JavacNode builderType, boolean mapMode, String emptyCollectionMethod, String singletonCollectionMethod, String targetType, JCTree source) {
+	protected List<JCStatement> createJavaUtilSetMapInitialCapacitySwitchStatements(JavacTreeMaker maker, SingularData data, JavacNode builderType, boolean mapMode, String emptyCollectionMethod, String singletonCollectionMethod, String targetType, JCTree source, String builderVariable) {
 		List<JCExpression> jceBlank = List.nil();
 		ListBuffer<JCCase> cases = new ListBuffer<JCCase>();
 		
@@ -66,11 +66,11 @@ abstract class JavacJavaUtilSingularizer extends JavacSingularizer {
 				// !mapMode: pluralName = java.util.Collections.singletonCollectionMethod(this.pluralName.get(0));
 				//  mapMode: pluralName = java.util.Collections.singletonCollectionMethod(this.pluralName$key.get(0), this.pluralName$value.get(0));
 				JCExpression zeroLiteral = maker.Literal(CTC_INT, 0);
-				JCExpression arg = maker.Apply(jceBlank, chainDots(builderType, "this", data.getPluralName() + (mapMode ? "$key" : ""), "get"), List.of(zeroLiteral));
+				JCExpression arg = maker.Apply(jceBlank, chainDots(builderType, builderVariable, data.getPluralName() + (mapMode ? "$key" : ""), "get"), List.of(zeroLiteral));
 				List<JCExpression> args;
 				if (mapMode) {
 					JCExpression zeroLiteralClone = maker.Literal(CTC_INT, 0);
-					JCExpression arg2 = maker.Apply(jceBlank, chainDots(builderType, "this", data.getPluralName() + (mapMode ? "$value" : ""), "get"), List.of(zeroLiteralClone));
+					JCExpression arg2 = maker.Apply(jceBlank, chainDots(builderType, builderVariable, data.getPluralName() + (mapMode ? "$value" : ""), "get"), List.of(zeroLiteralClone));
 					args = List.of(arg, arg2);
 				} else {
 					args = List.of(arg);
@@ -84,12 +84,12 @@ abstract class JavacJavaUtilSingularizer extends JavacSingularizer {
 		}
 		
 		{ // default:
-			List<JCStatement> statements = createJavaUtilSimpleCreationAndFillStatements(maker, data, builderType, mapMode, false, true, emptyCollectionMethod == null, targetType, source);
+			List<JCStatement> statements = createJavaUtilSimpleCreationAndFillStatements(maker, data, builderType, mapMode, false, true, emptyCollectionMethod == null, targetType, source, builderVariable);
 			JCCase defaultCase = maker.Case(null, statements);
 			cases.append(defaultCase);
 		}
 		
-		JCStatement switchStat = maker.Switch(getSize(maker,  builderType, mapMode ? builderType.toName(data.getPluralName() + "$key") : data.getPluralName(), true, false), cases.toList());
+		JCStatement switchStat = maker.Switch(getSize(maker,  builderType, mapMode ? builderType.toName(data.getPluralName() + "$key") : data.getPluralName(), true, false, builderVariable), cases.toList());
 		JCExpression localShadowerType = chainDotsString(builderType, data.getTargetFqn());
 		localShadowerType = addTypeArgs(mapMode ? 2 : 1, false, builderType, localShadowerType, data.getTypeArgs(), source);
 		JCStatement varDefStat = maker.VarDef(maker.Modifiers(0), data.getPluralName(), localShadowerType, null);
@@ -125,9 +125,9 @@ abstract class JavacJavaUtilSingularizer extends JavacSingularizer {
 		return maker.If(cond, thenPart, null);
 	}
 	
-	protected List<JCStatement> createJavaUtilSimpleCreationAndFillStatements(JavacTreeMaker maker, SingularData data, JavacNode builderType, boolean mapMode, boolean defineVar, boolean addInitialCapacityArg, boolean nullGuard, String targetType, JCTree source) {
+	protected List<JCStatement> createJavaUtilSimpleCreationAndFillStatements(JavacTreeMaker maker, SingularData data, JavacNode builderType, boolean mapMode, boolean defineVar, boolean addInitialCapacityArg, boolean nullGuard, String targetType, JCTree source, String builderVariable) {
 		List<JCExpression> jceBlank = List.nil();
-		Name thisName = builderType.toName("this");
+		Name thisName = builderType.toName(builderVariable);
 		
 		JCStatement createStat; {
 			 // pluralName = new java.util.TargetType(initialCap);
@@ -136,10 +136,10 @@ abstract class JavacJavaUtilSingularizer extends JavacSingularizer {
 				Name varName = mapMode ? builderType.toName(data.getPluralName() + "$key") : data.getPluralName();
 				// this.varName.size() < MAX_POWER_OF_2 ? 1 + this.varName.size() + (this.varName.size() - 3) / 3 : Integer.MAX_VALUE;
 				// lessThanCutOff = this.varName.size() < MAX_POWER_OF_2
-				JCExpression lessThanCutoff = maker.Binary(CTC_LESS_THAN, getSize(maker, builderType, varName, nullGuard, true), maker.Literal(CTC_INT, 0x40000000));
+				JCExpression lessThanCutoff = maker.Binary(CTC_LESS_THAN, getSize(maker, builderType, varName, nullGuard, true, builderVariable), maker.Literal(CTC_INT, 0x40000000));
 				JCExpression integerMaxValue = genJavaLangTypeRef(builderType, "Integer", "MAX_VALUE");
-				JCExpression sizeFormulaLeft = maker.Binary(CTC_PLUS, maker.Literal(CTC_INT, 1), getSize(maker, builderType, varName, nullGuard, true));
-				JCExpression sizeFormulaRightLeft = maker.Parens(maker.Binary(CTC_MINUS, getSize(maker, builderType, varName, nullGuard, true), maker.Literal(CTC_INT, 3)));
+				JCExpression sizeFormulaLeft = maker.Binary(CTC_PLUS, maker.Literal(CTC_INT, 1), getSize(maker, builderType, varName, nullGuard, true, builderVariable));
+				JCExpression sizeFormulaRightLeft = maker.Parens(maker.Binary(CTC_MINUS, getSize(maker, builderType, varName, nullGuard, true, builderVariable), maker.Literal(CTC_INT, 3)));
 				JCExpression sizeFormulaRight = maker.Binary(CTC_DIV, sizeFormulaRightLeft, maker.Literal(CTC_INT, 3));
 				JCExpression sizeFormula = maker.Binary(CTC_PLUS, sizeFormulaLeft, sizeFormulaRight);
 				constructorArgs = List.<JCExpression>of(maker.Conditional(lessThanCutoff, sizeFormula, integerMaxValue));
@@ -163,14 +163,14 @@ abstract class JavacJavaUtilSingularizer extends JavacSingularizer {
 				Name ivar = builderType.toName("$i");
 				Name keyVarName = builderType.toName(data.getPluralName() + "$key");
 				JCExpression pluralnameDotPut = maker.Select(maker.Ident(data.getPluralName()), builderType.toName("put"));
-				JCExpression arg1 = maker.Apply(jceBlank, chainDots(builderType, "this", data.getPluralName() + "$key", "get"), List.<JCExpression>of(maker.Ident(ivar)));
-				JCExpression arg2 = maker.Apply(jceBlank, chainDots(builderType, "this", data.getPluralName() + "$value", "get"), List.<JCExpression>of(maker.Ident(ivar)));
+				JCExpression arg1 = maker.Apply(jceBlank, chainDots(builderType, builderVariable, data.getPluralName() + "$key", "get"), List.<JCExpression>of(maker.Ident(ivar)));
+				JCExpression arg2 = maker.Apply(jceBlank, chainDots(builderType, builderVariable, data.getPluralName() + "$value", "get"), List.<JCExpression>of(maker.Ident(ivar)));
 				// [jdk9] We add an unneccessary (V) cast here. Not doing so gives an error in javac (build 9-ea+156-jigsaw-nightly-h6072-20170212):
 				//   error: method put in interface Map<K#2,V#2> cannot be applied to given types;
 				arg2 = maker.TypeCast(createTypeArgs(2, false, builderType, data.getTypeArgs(), source).get(1), arg2);
 				JCStatement putStatement = maker.Exec(maker.Apply(jceBlank, pluralnameDotPut, List.of(arg1, arg2)));
 				JCStatement forInit = maker.VarDef(maker.Modifiers(0), ivar, maker.TypeIdent(CTC_INT), maker.Literal(CTC_INT, 0));
-				JCExpression checkExpr = maker.Binary(CTC_LESS_THAN, maker.Ident(ivar), getSize(maker, builderType, keyVarName, nullGuard, true));
+				JCExpression checkExpr = maker.Binary(CTC_LESS_THAN, maker.Ident(ivar), getSize(maker, builderType, keyVarName, nullGuard, true, builderVariable));
 				JCExpression incrementExpr = maker.Unary(CTC_POSTINC, maker.Ident(ivar));
 				fillStat = maker.ForLoop(List.of(forInit), checkExpr, List.of(maker.Exec(incrementExpr)), putStatement);
 			} else {