[fixes #2104] superbuilder + non-list-singulars wouldn’t work due to hardcoded call to emptyList.

doc/changelog.markdown

@@ -11,6 +11,7 @@ Lombok Changelog
 * BUGFIX: Fix for java6 regression if a field has javadoc. [Issue #2066](https://github.com/rzwitserloot/lombok/issues/2066)
 * BUGFIX: Delombok now delomboks java10's own `var` as `var` and not as the actual underlying type. [Issue #2049](https://github.com/rzwitserloot/lombok/issues/2049)
 * BUGFIX: If you use `@Builder` and manually write the `build()` method in your builder class, javac would error out instead of deferring to your implementation. [Issue #2050](https://github.com/rzwitserloot/lombok/issues/2050) [Issue #2061](https://github.com/rzwitserloot/lombok/issues/2061)
+* BUGFIX: `@SuperBuilder` together with `@Singular` on non-lists would produce an erroneous `emptyList` call. [Issue #2104](https://github.com/rzwitserloot/lombok/issues/2104).
 * IMPROBABLE BREAKING CHANGE: For fields and parameters marked non-null, if the method body starts with an assert statement to ensure the value isn't null, no code to throw an exception will be generated.
 
 ### v1.18.6 (February 12th, 2019)

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

@@ -395,5 +395,8 @@ public class EclipseSingularsRecipes {
 				return new SingleNameReference(builderVariable.toCharArray(), 0);
 			}
 		}
+		
+		protected abstract char[][] getEmptyMakerReceiver(String targetFqn);
+		protected abstract char[] getEmptyMakerSelector(String targetFqn);
 	}
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2013-2018 The Project Lombok Authors.
+ * Copyright (C) 2013-2019 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
@@ -108,7 +108,6 @@ public class HandleSuperBuilder extends EclipseAnnotationHandler<SuperBuilder> {
 	private static final char[] TO_BUILDER_METHOD_NAME = TO_BUILDER_METHOD_NAME_STRING.toCharArray();
 	private static final char[] FILL_VALUES_METHOD_NAME = "$fillValuesFrom".toCharArray();
 	private static final char[] FILL_VALUES_STATIC_METHOD_NAME = "$fillValuesFromInstanceIntoBuilder".toCharArray();
-	private static final char[] EMPTY_LIST = "emptyList".toCharArray();
 	private static final char[] INSTANCE_VARIABLE_NAME = "instance".toCharArray();
 	private static final String BUILDER_VARIABLE_NAME_STRING = "b";
 	private static final char[] BUILDER_VARIABLE_NAME = BUILDER_VARIABLE_NAME_STRING.toCharArray();
@@ -741,10 +740,10 @@ public class HandleSuperBuilder extends EclipseAnnotationHandler<SuperBuilder> {
 			ms.arguments = tgt;
 		} else {
 			Expression ifNull = new EqualExpression(tgt[0], new NullLiteral(0, 0), OperatorIds.EQUAL_EQUAL);
-			MessageSend emptyList = new MessageSend();
-			emptyList.receiver = generateQualifiedNameRef(source, TypeConstants.JAVA, TypeConstants.UTIL, "Collections".toCharArray());
-			emptyList.selector = EMPTY_LIST;
-			ms.arguments = new Expression[] {new ConditionalExpression(ifNull, emptyList, tgt[1])};
+			MessageSend emptyCollection = new MessageSend();
+			emptyCollection.receiver = generateQualifiedNameRef(source, bfd.singularData.getSingularizer().getEmptyMakerReceiver(bfd.singularData.getTargetFqn()));
+			emptyCollection.selector = bfd.singularData.getSingularizer().getEmptyMakerSelector(bfd.singularData.getTargetFqn());
+			ms.arguments = new Expression[] {new ConditionalExpression(ifNull, emptyCollection, tgt[1])};
 		}
 		ms.receiver = new SingleNameReference(BUILDER_VARIABLE_NAME, 0);
 		ms.selector = setterName;

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

@@ -63,6 +63,9 @@ import org.eclipse.jdt.internal.compiler.ast.TypeReference;
 import org.eclipse.jdt.internal.compiler.classfmt.ClassFileConstants;
 
 abstract class EclipseGuavaSingularizer extends EclipseSingularizer {
+	protected static final char[] OF = {'o', 'f'};
+	protected static final char[][] CGCC = {{'c', 'o', 'm'}, {'g', 'o', 'o', 'g', 'l', 'e'}, {'c', 'o', 'm', 'm', 'o', 'n'}, {'c', 'o', 'l', 'l', 'e', 'c', 't'}};
+	
 	protected String getSimpleTargetTypeName(SingularData data) {
 		return GuavaTypeMap.getGuavaTypeName(data.getTargetFqn());
 	}
@@ -75,15 +78,23 @@ abstract class EclipseGuavaSingularizer extends EclipseSingularizer {
 	
 	protected char[][] makeGuavaTypeName(String simpleName, boolean addBuilder) {
 		char[][] tokenizedName = new char[addBuilder ? 6 : 5][];
-		tokenizedName[0] = new char[] {'c', 'o', 'm'};
-		tokenizedName[1] = new char[] {'g', 'o', 'o', 'g', 'l', 'e'};
-		tokenizedName[2] = new char[] {'c', 'o', 'm', 'm', 'o', 'n'};
-		tokenizedName[3] = new char[] {'c', 'o', 'l', 'l', 'e', 'c', 't'};
+		tokenizedName[0] = CGCC[0];
+		tokenizedName[1] = CGCC[1];
+		tokenizedName[2] = CGCC[2];
+		tokenizedName[3] = CGCC[3];
 		tokenizedName[4] = simpleName.toCharArray();
 		if (addBuilder) tokenizedName[5] = new char[] { 'B', 'u', 'i', 'l', 'd', 'e', 'r'};
 		return tokenizedName;
 	}
 	
+	@Override protected char[] getEmptyMakerSelector(String targetFqn) {
+		return OF;
+	}
+	
+	@Override protected char[][] getEmptyMakerReceiver(String targetFqn) {
+		return CGCC;
+	}
+	
 	@Override public List<EclipseNode> generateFields(SingularData data, EclipseNode builderType) {
 		String simpleTypeName = getSimpleTargetTypeName(data);
 		char[][] tokenizedName = makeGuavaTypeName(simpleTypeName, true);

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2015 The Project Lombok Authors.
+ * Copyright (C) 2015-2019 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
@@ -55,6 +55,16 @@ public class EclipseJavaUtilListSingularizer extends EclipseJavaUtilListSetSingu
 		return LombokImmutableList.of("java.util.List", "java.util.Collection", "java.lang.Iterable");
 	}
 	
+	private static final char[] EMPTY_LIST = {'e', 'm', 'p', 't', 'y', 'L', 'i', 's', 't'};
+	
+	@Override protected char[][] getEmptyMakerReceiver(String targetFqn) {
+		return JAVA_UTIL_COLLECTIONS;
+	}
+	
+	@Override protected char[] getEmptyMakerSelector(String targetFqn) {
+		return EMPTY_LIST;
+	}
+	
 	@Override public void appendBuildCode(SingularData data, EclipseNode builderType, List<Statement> statements, char[] targetVariableName, String builderVariable) {
 		if (useGuavaInstead(builderType)) {
 			guavaListSetSingularizer.appendBuildCode(data, builderType, statements, targetVariableName, builderVariable);

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

@@ -68,6 +68,20 @@ public class EclipseJavaUtilMapSingularizer extends EclipseJavaUtilSingularizer
 		return LombokImmutableList.of("java.util.Map", "java.util.SortedMap", "java.util.NavigableMap");
 	}
 	
+	private static final char[] EMPTY_SORTED_MAP = {'e', 'm', 'p', 't', 'y', 'S', 'o', 'r', 't', 'e', 'd', 'M', 'a', 'p'};
+	private static final char[] EMPTY_NAVIGABLE_MAP = {'e', 'm', 'p', 't', 'y', 'N', 'a', 'v', 'i', 'g', 'a', 'b', 'l', 'e', 'M', 'a', 'p'};
+	private static final char[] EMPTY_MAP = {'e', 'm', 'p', 't', 'y', 'M', 'a', 'p'};
+	
+	@Override protected char[][] getEmptyMakerReceiver(String targetFqn) {
+		return JAVA_UTIL_COLLECTIONS;
+	}
+	
+	@Override protected char[] getEmptyMakerSelector(String targetFqn) {
+		if (targetFqn.endsWith("SortedMap")) return EMPTY_SORTED_MAP;
+		if (targetFqn.endsWith("NavigableMap")) return EMPTY_NAVIGABLE_MAP;
+		return EMPTY_MAP;
+	}
+	
 	@Override public List<char[]> listFieldsToBeGenerated(SingularData data, EclipseNode builderType) {
 		if (useGuavaInstead(builderType)) {
 			return guavaMapSingularizer.listFieldsToBeGenerated(data, builderType);

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2015 The Project Lombok Authors.
+ * Copyright (C) 2015-2019 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
@@ -37,6 +37,20 @@ public class EclipseJavaUtilSetSingularizer extends EclipseJavaUtilListSetSingul
 		return LombokImmutableList.of("java.util.Set", "java.util.SortedSet", "java.util.NavigableSet");
 	}
 	
+	private static final char[] EMPTY_SORTED_SET = {'e', 'm', 'p', 't', 'y', 'S', 'o', 'r', 't', 'e', 'd', 'S', 'e', 't'};
+	private static final char[] EMPTY_NAVIGABLE_SET = {'e', 'm', 'p', 't', 'y', 'N', 'a', 'v', 'i', 'g', 'a', 'b', 'l', 'e', 'S', 'e', 't'};
+	private static final char[] EMPTY_SET = {'e', 'm', 'p', 't', 'y', 'S', 'e', 't'};
+	
+	@Override protected char[][] getEmptyMakerReceiver(String targetFqn) {
+		return JAVA_UTIL_COLLECTIONS;
+	}
+	
+	@Override protected char[] getEmptyMakerSelector(String targetFqn) {
+		if (targetFqn.endsWith("SortedSet")) return EMPTY_SORTED_SET;
+		if (targetFqn.endsWith("NavigableSet")) return EMPTY_NAVIGABLE_SET;
+		return EMPTY_SET;
+	}
+	
 	@Override public void appendBuildCode(SingularData data, EclipseNode builderType, List<Statement> statements, char[] targetVariableName, String builderVariable) {
 		if (useGuavaInstead(builderType)) {
 			guavaListSetSingularizer.appendBuildCode(data, builderType, statements, targetVariableName, builderVariable);

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2013-2018 The Project Lombok Authors.
+ * Copyright (C) 2013-2019 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
@@ -725,8 +725,9 @@ public class HandleSuperBuilder extends JavacAnnotationHandler<SuperBuilder> {
 			arg = tgt[0];
 		} else {
 			JCExpression eqNull = maker.Binary(CTC_EQUAL, tgt[0], maker.Literal(CTC_BOT, null));
-			JCExpression emptyList = maker.Apply(List.<JCExpression>nil(), chainDots(type, "java", "util", "Collections", "emptyList"), List.<JCExpression>nil());
-			arg = maker.Conditional(eqNull, emptyList, tgt[1]);
+			String emptyMaker = bfd.singularData.getSingularizer().getEmptyMaker(bfd.singularData.getTargetFqn());
+			JCExpression emptyCollection = maker.Apply(List.<JCExpression>nil(), chainDots(type, emptyMaker.split("\\.")), List.<JCExpression>nil());
+			arg = maker.Conditional(eqNull, emptyCollection, tgt[1]);
 		}
 		JCMethodInvocation apply = maker.Apply(List.<JCExpression>nil(), maker.Select(maker.Ident(type.toName(BUILDER_VARIABLE_NAME)), bfd.name), List.of(arg));
 		JCExpressionStatement exec = maker.Exec(apply);

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

@@ -437,5 +437,7 @@ public class JavacSingularsRecipes {
 		protected abstract String getAddMethodName();
 		
 		protected abstract int getTypeArgumentsCount();
+		
+		protected abstract String getEmptyMaker(String target);
 	}
 }

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

@@ -51,6 +51,10 @@ abstract class JavacGuavaSingularizer extends JavacSingularizer {
 		return GuavaTypeMap.getGuavaTypeName(data.getTargetFqn());
 	}
 	
+	@Override protected String getEmptyMaker(String target) {
+		return target + ".of";
+	}
+	
 	protected String getBuilderMethodName(SingularData data) {
 		String simpleTypeName = getSimpleTargetTypeName(data);
 		if ("ImmutableSortedSet".equals(simpleTypeName) || "ImmutableSortedMap".equals(simpleTypeName)) return "naturalOrder";

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

@@ -46,6 +46,10 @@ public class JavacJavaUtilListSingularizer extends JavacJavaUtilListSetSingulari
 		return LombokImmutableList.of("java.util.List", "java.util.Collection", "java.lang.Iterable");
 	}
 	
+	@Override protected String getEmptyMaker(String target) {
+		return "java.util.Collections.emptyList";
+	}
+	
 	@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();

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

@@ -54,6 +54,12 @@ public class JavacJavaUtilMapSingularizer extends JavacJavaUtilSingularizer {
 		return LombokImmutableList.of("java.util.Map", "java.util.SortedMap", "java.util.NavigableMap");
 	}
 	
+	@Override protected String getEmptyMaker(String target) {
+		if (target.endsWith("NavigableMap")) return "java.util.Collections.emptyNavigableMap";
+		if (target.endsWith("SortedMap")) return "java.util.Collections.emptySortedMap";
+		return "java.util.Collections.emptyMap";
+	}
+	
 	@Override protected JavacSingularizer getGuavaInstead(JavacNode node) {
 		return new JavacGuavaMapSingularizer();
 	}

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

@@ -40,6 +40,12 @@ public class JavacJavaUtilSetSingularizer extends JavacJavaUtilListSetSingulariz
 		return LombokImmutableList.of("java.util.Set", "java.util.SortedSet", "java.util.NavigableSet");
 	}
 	
+	@Override protected String getEmptyMaker(String target) {
+		if (target.endsWith("SortedSet")) return "java.util.Collections.emptySortedSet";
+		if (target.endsWith("NavigableSet")) return "java.util.Collections.emptyNavigableSet";
+		return "java.util.Collections.emptySet";
+	}
+	
 	@Override public void appendBuildCode(SingularData data, JavacNode builderType, JCTree source, ListBuffer<JCStatement> statements, Name targetVariableName, String builderVariable) {
 		JavacTreeMaker maker = builderType.getTreeMaker();
 		

test/transform/resource/after-delombok/SuperBuilderWithGenericsAndToBuilder.java

@@ -1,14 +1,16 @@
-import java.util.List;
+import java.util.Map;
 public class SuperBuilderWithGenericsAndToBuilder {
 	public static class Parent<A> {
 		A field1;
-		List<String> items;
+		Map<Integer, String> items;
 		@java.lang.SuppressWarnings("all")
 		public static abstract class ParentBuilder<A, C extends Parent<A>, B extends ParentBuilder<A, C, B>> {
 			@java.lang.SuppressWarnings("all")
 			private A field1;
 			@java.lang.SuppressWarnings("all")
-			private java.util.ArrayList<String> items;
+			private java.util.ArrayList<Integer> items$key;
+			@java.lang.SuppressWarnings("all")
+			private java.util.ArrayList<String> items$value;
 			@java.lang.SuppressWarnings("all")
 			protected B $fillValuesFrom(final C instance) {
 				ParentBuilder.$fillValuesFromInstanceIntoBuilder(instance, this);
@@ -17,7 +19,7 @@ public class SuperBuilderWithGenericsAndToBuilder {
 			@java.lang.SuppressWarnings("all")
 			private static <A> void $fillValuesFromInstanceIntoBuilder(final Parent<A> instance, final ParentBuilder<A, ?, ?> b) {
 				b.field1(instance.field1);
-				b.items(instance.items == null ? java.util.Collections.emptyList() : instance.items);
+				b.items(instance.items == null ? java.util.Collections.emptyMap() : instance.items);
 			}
 			@java.lang.SuppressWarnings("all")
 			protected abstract B self();
@@ -29,26 +31,39 @@ public class SuperBuilderWithGenericsAndToBuilder {
 				return self();
 			}
 			@java.lang.SuppressWarnings("all")
-			public B item(final String item) {
-				if (this.items == null) this.items = new java.util.ArrayList<String>();
-				this.items.add(item);
+			public B item(final Integer itemKey, final String itemValue) {
+				if (this.items$key == null) {
+					this.items$key = new java.util.ArrayList<Integer>();
+					this.items$value = new java.util.ArrayList<String>();
+				}
+				this.items$key.add(itemKey);
+				this.items$value.add(itemValue);
 				return self();
 			}
 			@java.lang.SuppressWarnings("all")
-			public B items(final java.util.Collection<? extends String> items) {
-				if (this.items == null) this.items = new java.util.ArrayList<String>();
-				this.items.addAll(items);
+			public B items(final java.util.Map<? extends Integer, ? extends String> items) {
+				if (this.items$key == null) {
+					this.items$key = new java.util.ArrayList<Integer>();
+					this.items$value = new java.util.ArrayList<String>();
+				}
+				for (final java.util.Map.Entry<? extends Integer, ? extends String> $lombokEntry : items.entrySet()) {
+					this.items$key.add($lombokEntry.getKey());
+					this.items$value.add($lombokEntry.getValue());
+				}
 				return self();
 			}
 			@java.lang.SuppressWarnings("all")
 			public B clearItems() {
-				if (this.items != null) this.items.clear();
+				if (this.items$key != null) {
+					this.items$key.clear();
+					this.items$value.clear();
+				}
 				return self();
 			}
 			@java.lang.Override
 			@java.lang.SuppressWarnings("all")
 			public java.lang.String toString() {
-				return "SuperBuilderWithGenericsAndToBuilder.Parent.ParentBuilder(field1=" + this.field1 + ", items=" + this.items + ")";
+				return "SuperBuilderWithGenericsAndToBuilder.Parent.ParentBuilder(field1=" + this.field1 + ", items$key=" + this.items$key + ", items$value=" + this.items$value + ")";
 			}
 		}
 		@java.lang.SuppressWarnings("all")
@@ -70,16 +85,18 @@ public class SuperBuilderWithGenericsAndToBuilder {
 		@java.lang.SuppressWarnings("all")
 		protected Parent(final ParentBuilder<A, ?, ?> b) {
 			this.field1 = b.field1;
-			java.util.List<String> items;
-			switch (b.items == null ? 0 : b.items.size()) {
+			java.util.Map<Integer, String> items;
+			switch (b.items$key == null ? 0 : b.items$key.size()) {
 			case 0: 
-				items = java.util.Collections.emptyList();
+				items = java.util.Collections.emptyMap();
 				break;
 			case 1: 
-				items = java.util.Collections.singletonList(b.items.get(0));
+				items = java.util.Collections.singletonMap(b.items$key.get(0), b.items$value.get(0));
 				break;
 			default: 
-				items = java.util.Collections.unmodifiableList(new java.util.ArrayList<String>(b.items));
+				items = new java.util.LinkedHashMap<Integer, String>(b.items$key.size() < 1073741824 ? 1 + b.items$key.size() + (b.items$key.size() - 3) / 3 : java.lang.Integer.MAX_VALUE);
+				for (int $i = 0; $i < b.items$key.size(); $i++) items.put(b.items$key.get($i), (String) b.items$value.get($i));
+				items = java.util.Collections.unmodifiableMap(items);
 			}
 			this.items = items;
 		}
@@ -157,6 +174,6 @@ public class SuperBuilderWithGenericsAndToBuilder {
 		}
 	}
 	public static void test() {
-		Child<Integer> x = Child.<Integer>builder().field3(0.0).field1(5).item("").build().toBuilder().build();
+		Child<Integer> x = Child.<Integer>builder().field3(0.0).field1(5).item(5, "").build().toBuilder().build();
 	}
 }

test/transform/resource/after-ecj/SuperBuilderWithGenericsAndToBuilder.java

@@ -1,9 +1,10 @@
-import java.util.List;
+import java.util.Map;
 public class SuperBuilderWithGenericsAndToBuilder {
   public static @lombok.experimental.SuperBuilder(toBuilder = true) class Parent<A> {
     public static abstract @java.lang.SuppressWarnings("all") class ParentBuilder<A, C extends Parent<A>, B extends ParentBuilder<A, C, B>> {
       private @java.lang.SuppressWarnings("all") A field1;
-      private @java.lang.SuppressWarnings("all") java.util.ArrayList<String> items;
+      private @java.lang.SuppressWarnings("all") java.util.ArrayList<Integer> items$key;
+      private @java.lang.SuppressWarnings("all") java.util.ArrayList<String> items$value;
       public ParentBuilder() {
         super();
       }
@@ -13,7 +14,7 @@ public class SuperBuilderWithGenericsAndToBuilder {
       }
       private static @java.lang.SuppressWarnings("all") <A>void $fillValuesFromInstanceIntoBuilder(final Parent<A> instance, final ParentBuilder<A, ?, ?> b) {
         b.field1(instance.field1);
-        b.items(((instance.items == null) ? java.util.Collections.emptyList() : instance.items));
+        b.items(((instance.items == null) ? java.util.Collections.emptyMap() : instance.items));
       }
       protected abstract @java.lang.SuppressWarnings("all") B self();
       public abstract @java.lang.SuppressWarnings("all") C build();
@@ -21,25 +22,39 @@ public class SuperBuilderWithGenericsAndToBuilder {
         this.field1 = field1;
         return self();
       }
-      public @java.lang.SuppressWarnings("all") B item(final String item) {
-        if ((this.items == null))
-            this.items = new java.util.ArrayList<String>();
-        this.items.add(item);
+      public @java.lang.SuppressWarnings("all") B item(final Integer itemKey, final String itemValue) {
+        if ((this.items$key == null))
+            {
+              this.items$key = new java.util.ArrayList<Integer>();
+              this.items$value = new java.util.ArrayList<String>();
+            }
+        this.items$key.add(itemKey);
+        this.items$value.add(itemValue);
         return self();
       }
-      public @java.lang.SuppressWarnings("all") B items(final java.util.Collection<? extends String> items) {
-        if ((this.items == null))
-            this.items = new java.util.ArrayList<String>();
-        this.items.addAll(items);
+      public @java.lang.SuppressWarnings("all") B items(final java.util.Map<? extends Integer, ? extends String> items) {
+        if ((this.items$key == null))
+            {
+              this.items$key = new java.util.ArrayList<Integer>();
+              this.items$value = new java.util.ArrayList<String>();
+            }
+        for (java.util.Map.Entry<? extends Integer, ? extends String> $lombokEntry : items.entrySet()) 
+          {
+            this.items$key.add($lombokEntry.getKey());
+            this.items$value.add($lombokEntry.getValue());
+          }
         return self();
       }
       public @java.lang.SuppressWarnings("all") B clearItems() {
-        if ((this.items != null))
-            this.items.clear();
+        if ((this.items$key != null))
+            {
+              this.items$key.clear();
+              this.items$value.clear();
+            }
         return self();
       }
       public @java.lang.Override @java.lang.SuppressWarnings("all") java.lang.String toString() {
-        return (((("SuperBuilderWithGenericsAndToBuilder.Parent.ParentBuilder(field1=" + this.field1) + ", items=") + this.items) + ")");
+        return (((((("SuperBuilderWithGenericsAndToBuilder.Parent.ParentBuilder(field1=" + this.field1) + ", items$key=") + this.items$key) + ", items$value=") + this.items$value) + ")");
       }
     }
     private static final @java.lang.SuppressWarnings("all") class ParentBuilderImpl<A> extends ParentBuilder<A, Parent<A>, ParentBuilderImpl<A>> {
@@ -54,20 +69,23 @@ public class SuperBuilderWithGenericsAndToBuilder {
       }
     }
     A field1;
-    @lombok.Singular List<String> items;
+    @lombok.Singular Map<Integer, String> items;
     protected @java.lang.SuppressWarnings("all") Parent(final ParentBuilder<A, ?, ?> b) {
       super();
       this.field1 = b.field1;
-      java.util.List<String> items;
-      switch (((b.items == null) ? 0 : b.items.size())) {
+      java.util.Map<Integer, String> items;
+      switch (((b.items$key == null) ? 0 : b.items$key.size())) {
       case 0 : 
-          items = java.util.Collections.emptyList();
+          items = java.util.Collections.emptyMap();
           break;
       case 1 : 
-          items = java.util.Collections.singletonList(b.items.get(0));
+          items = java.util.Collections.singletonMap(b.items$key.get(0), b.items$value.get(0));
           break;
       default : 
-          items = java.util.Collections.unmodifiableList(new java.util.ArrayList<String>(b.items));
+          items = new java.util.LinkedHashMap<Integer, String>(((b.items$key.size() < 0x40000000) ? ((1 + b.items$key.size()) + ((b.items$key.size() - 3) / 3)) : java.lang.Integer.MAX_VALUE));
+          for (int $i = 0;; ($i < b.items$key.size()); $i ++) 
+            items.put(b.items$key.get($i), b.items$value.get($i));
+          items = java.util.Collections.unmodifiableMap(items);
       }
       this.items = items;
     }
@@ -129,6 +147,6 @@ public class SuperBuilderWithGenericsAndToBuilder {
     super();
   }
   public static void test() {
-    Child<Integer> x = Child.<Integer>builder().field3(0.0).field1(5).item("").build().toBuilder().build();
+    Child<Integer> x = Child.<Integer>builder().field3(0.0).field1(5).item(5, "").build().toBuilder().build();
   }
 }

test/transform/resource/before/SuperBuilderWithGenericsAndToBuilder.java

@@ -1,10 +1,10 @@
-import java.util.List;
+import java.util.Map;
 
 public class SuperBuilderWithGenericsAndToBuilder {
 	@lombok.experimental.SuperBuilder(toBuilder = true)
 	public static class Parent<A> {
 		A field1;
-		@lombok.Singular List<String> items;
+		@lombok.Singular Map<Integer, String> items;
 	}
 	
 	@lombok.experimental.SuperBuilder(toBuilder = true)
@@ -13,6 +13,6 @@ public class SuperBuilderWithGenericsAndToBuilder {
 	}
 	
 	public static void test() {
-		Child<Integer> x = Child.<Integer>builder().field3(0.0).field1(5).item("").build().toBuilder().build();
+		Child<Integer> x = Child.<Integer>builder().field3(0.0).field1(5).item(5, "").build().toBuilder().build();
 	}
 }