code impl of FieldNameConstants rewrite + test updates for it

4 files changed, 188 insertions, 124 deletions

diff --git a/src/core/lombok/ConfigurationKeys.java b/src/core/lombok/ConfigurationKeys.java
index 1a28c0fa..184ded27 100644
--- a/src/core/lombok/ConfigurationKeys.java
+++ b/src/core/lombok/ConfigurationKeys.java
@@ -529,18 +529,11 @@ public class ConfigurationKeys {
 	public static final ConfigurationKey<FlagUsageType> FIELD_NAME_CONSTANTS_FLAG_USAGE = new ConfigurationKey<FlagUsageType>("lombok.fieldNameConstants.flagUsage", "Emit a warning or error if @FieldNameConstants is used.") {};
 	
 	/**
-	 * lombok configuration: {@code lombok.fieldNameConstants.prefix} = &lt;String: aJavaIdentifierPrefix&gt; (Default: {@code PREFIX_}).
+	 * lombok configuration: {@code lombok.fieldNameConstants.innerTypeName} = &lt;String: AValidJavaTypeName&gt; (Default: {@code Fields}).
 	 * 
 	 * The names of the constants generated by {@code @FieldNameConstants} will be prefixed with this value.
 	 */
-	public static final ConfigurationKey<String> FIELD_NAME_CONSTANTS_PREFIX = new ConfigurationKey<String>("lombok.fieldNameConstants.prefix", "names of constants generated by @FieldNameConstants will be prefixed with this value. (default: 'PREFIX_').") {};
-	
-	/**
-	 * lombok configuration: {@code lombok.fieldNameConstants.suffix} = &lt;String: aJavaIdentifierPrefix&gt; (Default: nothing).
-	 * 
-	 * The names of the constants generated by {@code @FieldNameConstants} will be suffixed with this value.
-	 */
-	public static final ConfigurationKey<String> FIELD_NAME_CONSTANTS_SUFFIX = new ConfigurationKey<String>("lombok.fieldNameConstants.suffix", "names of constants generated by @FieldNameConstants will be suffixed with this value. (default: nothing).") {};
+	public static final ConfigurationKey<String> FIELD_NAME_CONSTANTS_INNER_TYPE_NAME = new ConfigurationKey<String>("lombok.fieldNameConstants.innerTypeName", "The default name of the inner type generated by @FieldNameConstants. (default: 'Fields').") {};
 	
 	// ----- Wither -----
 	
diff --git a/src/core/lombok/eclipse/handlers/HandleFieldNameConstants.java b/src/core/lombok/eclipse/handlers/HandleFieldNameConstants.java
index c3a28f7f..15650490 100644
--- a/src/core/lombok/eclipse/handlers/HandleFieldNameConstants.java
+++ b/src/core/lombok/eclipse/handlers/HandleFieldNameConstants.java
@@ -24,32 +24,37 @@ package lombok.eclipse.handlers;
 import static lombok.core.handlers.HandlerUtil.handleExperimentalFlagUsage;
 import static lombok.eclipse.handlers.EclipseHandlerUtil.*;
 
-import java.lang.reflect.Modifier;
-import java.util.Collection;
+import java.util.ArrayList;
+import java.util.List;
 
 import lombok.AccessLevel;
 import lombok.ConfigurationKeys;
 import lombok.core.AST.Kind;
 import lombok.core.AnnotationValues;
-import lombok.core.handlers.HandlerUtil;
 import lombok.eclipse.Eclipse;
 import lombok.eclipse.EclipseAnnotationHandler;
 import lombok.eclipse.EclipseNode;
 import lombok.experimental.FieldNameConstants;
 
 import org.eclipse.jdt.internal.compiler.ast.ASTNode;
+import org.eclipse.jdt.internal.compiler.ast.AllocationExpression;
 import org.eclipse.jdt.internal.compiler.ast.Annotation;
+import org.eclipse.jdt.internal.compiler.ast.Clinit;
+import org.eclipse.jdt.internal.compiler.ast.ConstructorDeclaration;
+import org.eclipse.jdt.internal.compiler.ast.ExplicitConstructorCall;
 import org.eclipse.jdt.internal.compiler.ast.FieldDeclaration;
 import org.eclipse.jdt.internal.compiler.ast.QualifiedTypeReference;
+import org.eclipse.jdt.internal.compiler.ast.Statement;
 import org.eclipse.jdt.internal.compiler.ast.StringLiteral;
 import org.eclipse.jdt.internal.compiler.ast.TypeDeclaration;
 import org.eclipse.jdt.internal.compiler.classfmt.ClassFileConstants;
+import org.eclipse.jdt.internal.compiler.lookup.ClassScope;
 import org.eclipse.jdt.internal.compiler.lookup.TypeConstants;
 import org.mangosdk.spi.ProviderFor;
 
 @ProviderFor(EclipseAnnotationHandler.class)
 public class HandleFieldNameConstants extends EclipseAnnotationHandler<FieldNameConstants> {
-	public void generateFieldNameConstantsForType(EclipseNode typeNode, EclipseNode errorNode, AccessLevel level, String prefix, String suffix) {
+	public void generateFieldNameConstantsForType(EclipseNode typeNode, EclipseNode errorNode, AccessLevel level, boolean asEnum, String innerTypeName, boolean onlyExplicit) {
 		TypeDeclaration typeDecl = null;
 		if (typeNode.get() instanceof TypeDeclaration) typeDecl = (TypeDeclaration) typeNode.get();
 		
@@ -57,22 +62,29 @@ public class HandleFieldNameConstants extends EclipseAnnotationHandler<FieldName
 		boolean notAClass = (modifiers & (ClassFileConstants.AccInterface | ClassFileConstants.AccAnnotation)) != 0;
 		
 		if (typeDecl == null || notAClass) {
-			errorNode.addError("@FieldNameConstants is only supported on a class, an enum, or a field.");
+			errorNode.addError("@FieldNameConstants is only supported on a class or an enum.");
 			return;
 		}
 		
+		List<EclipseNode> qualified = new ArrayList<EclipseNode>();
+		
 		for (EclipseNode field : typeNode.down()) {
-			if (fieldQualifiesForFieldNameConstantsGeneration(field)) generateFieldNameConstantsForField(field, errorNode.get(), level, prefix, suffix);
+			if (fieldQualifiesForFieldNameConstantsGeneration(field, onlyExplicit)) qualified.add(field);
+		}
+		
+		if (qualified.isEmpty()) {
+			errorNode.addWarning("No fields qualify for @FieldNameConstants, therefore this annotation does nothing");
+		} else {
+			createInnerTypeFieldNameConstants(typeNode, errorNode.get(), level, qualified, asEnum, innerTypeName);
 		}
 	}
 	
-	private void generateFieldNameConstantsForField(EclipseNode fieldNode, ASTNode pos, AccessLevel level, String prefix, String suffix) {
-		if (hasAnnotation(FieldNameConstants.class, fieldNode)) return;
-		createFieldNameConstantsForField(level, prefix, suffix, fieldNode, fieldNode, pos, false);
-	}
-	
-	private boolean fieldQualifiesForFieldNameConstantsGeneration(EclipseNode field) {
+	private boolean fieldQualifiesForFieldNameConstantsGeneration(EclipseNode field, boolean onlyExplicit) {
 		if (field.getKind() != Kind.FIELD) return false;
+		if (hasAnnotation(FieldNameConstants.Exclude.class, field)) return false;
+		if (hasAnnotation(FieldNameConstants.Include.class, field)) return true;
+		if (onlyExplicit) return false;
+		
 		FieldDeclaration fieldDecl = (FieldDeclaration) field.get();
 		return filterField(fieldDecl);
 	}
@@ -81,55 +93,75 @@ public class HandleFieldNameConstants extends EclipseAnnotationHandler<FieldName
 		handleExperimentalFlagUsage(annotationNode, ConfigurationKeys.FIELD_NAME_CONSTANTS_FLAG_USAGE, "@FieldNameConstants");
 		
 		EclipseNode node = annotationNode.up();
-		FieldNameConstants annotatationInstance = annotation.getInstance();
-		AccessLevel level = annotatationInstance.level();
-		String prefix = annotatationInstance.prefix();
-		String suffix = annotatationInstance.suffix();
-		if (prefix.equals(" CONFIG DEFAULT ")) prefix = annotationNode.getAst().readConfiguration(ConfigurationKeys.FIELD_NAME_CONSTANTS_PREFIX);
-		if (suffix.equals(" CONFIG DEFAULT ")) suffix = annotationNode.getAst().readConfiguration(ConfigurationKeys.FIELD_NAME_CONSTANTS_SUFFIX);
-		if (prefix == null) prefix = "FIELD_";
-		if (suffix == null) suffix = "";
-		if (node == null) return;
-		
-		switch (node.getKind()) {
-		case FIELD:
-			if (level != AccessLevel.NONE) createFieldNameConstantsForFields(level, prefix, suffix, annotationNode.upFromAnnotationToFields(), annotationNode, annotationNode.get(), true);
-			break;
-		case TYPE:
-			if (level == AccessLevel.NONE) {
-				annotationNode.addWarning("type-level '@FieldNameConstants' does not work with AccessLevel.NONE.");
-				return;
-			}
-			generateFieldNameConstantsForType(node, annotationNode, level, prefix, suffix);
-			break;
-		}
-	}
-	
-	private void createFieldNameConstantsForFields(AccessLevel level, String prefix, String suffix, Collection<EclipseNode> fieldNodes, EclipseNode errorNode, ASTNode source, boolean whineIfExists) {
-		for (EclipseNode fieldNode : fieldNodes) createFieldNameConstantsForField(level, prefix, suffix, fieldNode, errorNode, source, whineIfExists);
-	}
-	
-	private void createFieldNameConstantsForField(AccessLevel level, String prefix, String suffix, EclipseNode fieldNode, EclipseNode errorNode, ASTNode source, boolean whineIfExists) {
-		if (fieldNode.getKind() != Kind.FIELD) {
-			errorNode.addError("@FieldNameConstants is only supported on a class, an enum, or a field");
+		FieldNameConstants annotationInstance = annotation.getInstance();
+		AccessLevel level = annotationInstance.level();
+		boolean asEnum = annotationInstance.asEnum();
+		boolean usingLombokv1_18_2 = annotation.isExplicit("prefix") || annotation.isExplicit("suffix") || node.getKind() == Kind.FIELD;
+		
+		if (usingLombokv1_18_2) {
+			annotationNode.addError("@FieldNameConstants has been redesigned in lombok v1.18.4; please upgrade your project dependency on lombok. See https://projectlombok.org/features/experimental/FieldNameConstants for more information.");
 			return;
 		}
 		
-		FieldDeclaration field = (FieldDeclaration) fieldNode.get();
-		String fieldName = new String(field.name);
-		String constantName = prefix + HandlerUtil.camelCaseToConstant(fieldName) + suffix;
-		if (constantName.equals(fieldName)) {
-			fieldNode.addWarning("Not generating constant for this field: The name of the constant would be equal to the name of this field.");
+		if (level == AccessLevel.NONE) {
+			annotationNode.addWarning("AccessLevel.NONE is not compatible with @FieldNameConstants. If you don't want the inner type, simply remove FieldNameConstants.");
 			return;
 		}
 		
-		int pS = source.sourceStart, pE = source.sourceEnd;
-		long p = (long) pS << 32 | pE;
-		FieldDeclaration fieldConstant = new FieldDeclaration(constantName.toCharArray(), pS,pE);
-		fieldConstant.bits |= Eclipse.ECLIPSE_DO_NOT_TOUCH_FLAG;
-		fieldConstant.modifiers = toEclipseModifier(level) | Modifier.STATIC | Modifier.FINAL;
-		fieldConstant.type = new QualifiedTypeReference(TypeConstants.JAVA_LANG_STRING, new long[] {p,p,p});
-		fieldConstant.initialization = new StringLiteral(field.name, pS, pE, 0);
-		injectField(fieldNode.up(), fieldConstant);
+		String innerTypeName = annotationInstance.innerTypeName();
+		if (innerTypeName.isEmpty()) innerTypeName = annotationNode.getAst().readConfiguration(ConfigurationKeys.FIELD_NAME_CONSTANTS_INNER_TYPE_NAME);
+		if (innerTypeName == null || innerTypeName.isEmpty()) innerTypeName = "Fields";
+		
+		generateFieldNameConstantsForType(node, annotationNode, level, asEnum, innerTypeName, annotationInstance.onlyExplicitlyIncluded());
+	}
+	
+	private void createInnerTypeFieldNameConstants(EclipseNode typeNode, ASTNode source, AccessLevel level, List<EclipseNode> fields, boolean asEnum, String innerTypeName) {
+		if (fields.isEmpty()) return;
+		
+		TypeDeclaration parent = (TypeDeclaration) typeNode.get();
+		TypeDeclaration innerType = new TypeDeclaration(parent.compilationResult);
+		innerType.bits |= Eclipse.ECLIPSE_DO_NOT_TOUCH_FLAG;
+		innerType.modifiers = toEclipseModifier(level) | (asEnum ? ClassFileConstants.AccEnum : ClassFileConstants.AccStatic | ClassFileConstants.AccFinal);
+		char[] name = innerTypeName.toCharArray();
+		innerType.name = name;
+		innerType.traverse(new SetGeneratedByVisitor(source), (ClassScope) null);
+		EclipseNode innerNode = injectType(typeNode, innerType);
+		
+		ConstructorDeclaration constructor = new ConstructorDeclaration(parent.compilationResult);
+		constructor.selector = name;
+		constructor.declarationSourceStart = constructor.sourceStart = source.sourceStart;
+		constructor.declarationSourceEnd = constructor.sourceEnd = source.sourceEnd;
+		constructor.modifiers = ClassFileConstants.AccPrivate;
+		ExplicitConstructorCall superCall = new ExplicitConstructorCall(0);
+		superCall.sourceStart = source.sourceStart;
+		superCall.sourceEnd = source.sourceEnd;
+		superCall.bits |= Eclipse.ECLIPSE_DO_NOT_TOUCH_FLAG;
+		constructor.constructorCall = superCall;
+		if (!asEnum) constructor.statements = new Statement[0];
+		
+		injectMethod(innerNode, constructor);
+		
+		if (asEnum) injectMethod(innerNode, new Clinit(parent.compilationResult));
+		
+		for (EclipseNode fieldNode : fields) {
+			FieldDeclaration field = (FieldDeclaration) fieldNode.get();
+			char[] fName = field.name;
+			int pS = source.sourceStart, pE = source.sourceEnd;
+			long p = (long) pS << 32 | pE;
+			FieldDeclaration fieldConstant = new FieldDeclaration(fName, pS, pE);
+			fieldConstant.bits |= Eclipse.ECLIPSE_DO_NOT_TOUCH_FLAG;
+			fieldConstant.modifiers = asEnum ? 0 : ClassFileConstants.AccPublic | ClassFileConstants.AccStatic | ClassFileConstants.AccFinal;
+			fieldConstant.type = asEnum ? null : new QualifiedTypeReference(TypeConstants.JAVA_LANG_STRING, new long[] {p, p, p});
+			if (asEnum) {
+				AllocationExpression ac = new AllocationExpression();
+				ac.enumConstant = fieldConstant;
+				ac.sourceStart = source.sourceStart;
+				ac.sourceEnd = source.sourceEnd;
+				fieldConstant.initialization = ac;
+			} else {
+				fieldConstant.initialization = new StringLiteral(field.name, pS, pE, 0);
+			}
+			injectField(innerNode, fieldConstant);
+		}
 	}
 }
diff --git a/src/core/lombok/experimental/FieldNameConstants.java b/src/core/lombok/experimental/FieldNameConstants.java
index 31c2970c..d6886890 100644
--- a/src/core/lombok/experimental/FieldNameConstants.java
+++ b/src/core/lombok/experimental/FieldNameConstants.java
@@ -29,12 +29,32 @@ import java.lang.annotation.Target;
 import lombok.AccessLevel;
 
 /**
- * Generates String constants containing the field name for each field.
+ * Generates an inner type, containing String constants containing the field name for each field. Alternatively, generates an inner enum with enum values matching each field name.
  */
-@Target({ElementType.TYPE, ElementType.FIELD})
+@Target(ElementType.TYPE)
 @Retention(RetentionPolicy.SOURCE)
 public @interface FieldNameConstants {
 	lombok.AccessLevel level() default AccessLevel.PUBLIC;
-	String prefix() default " CONFIG DEFAULT ";
-	String suffix() default " CONFIG DEFAULT ";
+	boolean asEnum() default false;
+	String innerTypeName() default "";
+	
+	/**
+	 * Only include fields and methods explicitly marked with {@code @FieldNameConstants.Include}.
+	 * Normally, all (non-static) fields are included by default.
+	 */
+	boolean onlyExplicitlyIncluded() default false;
+	
+	/**
+	 * If present, do not include this field in the generated fieldnames inner type.
+	 */
+	@Target(ElementType.FIELD)
+	@Retention(RetentionPolicy.SOURCE)
+	public @interface Exclude {}
+	
+	/**
+	 * If present, include this field in the generated fieldnames inner type (default).
+	 */
+	@Target(ElementType.FIELD)
+	@Retention(RetentionPolicy.SOURCE)
+	public @interface Include {}
 }
diff --git a/src/core/lombok/javac/handlers/HandleFieldNameConstants.java b/src/core/lombok/javac/handlers/HandleFieldNameConstants.java
index 8ff136fc..5b120948 100644
--- a/src/core/lombok/javac/handlers/HandleFieldNameConstants.java
+++ b/src/core/lombok/javac/handlers/HandleFieldNameConstants.java
@@ -24,13 +24,11 @@ package lombok.javac.handlers;
 import static lombok.core.handlers.HandlerUtil.handleExperimentalFlagUsage;
 import static lombok.javac.handlers.JavacHandlerUtil.*;
 
-import java.lang.reflect.Modifier;
-import java.util.Collection;
+import java.util.ArrayList;
 
 import lombok.AccessLevel;
 import lombok.ConfigurationKeys;
 import lombok.core.AST.Kind;
-import lombok.core.handlers.HandlerUtil;
 import lombok.core.AnnotationValues;
 import lombok.experimental.FieldNameConstants;
 import lombok.javac.JavacAnnotationHandler;
@@ -40,16 +38,23 @@ import lombok.javac.JavacTreeMaker;
 import org.mangosdk.spi.ProviderFor;
 
 import com.sun.tools.javac.code.Flags;
+import com.sun.tools.javac.tree.JCTree;
 import com.sun.tools.javac.tree.JCTree.JCAnnotation;
+import com.sun.tools.javac.tree.JCTree.JCBlock;
 import com.sun.tools.javac.tree.JCTree.JCClassDecl;
 import com.sun.tools.javac.tree.JCTree.JCExpression;
+import com.sun.tools.javac.tree.JCTree.JCMethodDecl;
 import com.sun.tools.javac.tree.JCTree.JCModifiers;
+import com.sun.tools.javac.tree.JCTree.JCStatement;
+import com.sun.tools.javac.tree.JCTree.JCTypeParameter;
 import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
+import com.sun.tools.javac.util.List;
+import com.sun.tools.javac.util.Name;
 
 @ProviderFor(JavacAnnotationHandler.class)
 public class HandleFieldNameConstants extends JavacAnnotationHandler<FieldNameConstants> {
-	public void generateFieldNameConstantsForType(JavacNode typeNode, JavacNode errorNode, AccessLevel level, String prefix, String suffix) {
+	public void generateFieldNameConstantsForType(JavacNode typeNode, JavacNode errorNode, AccessLevel level, boolean asEnum, String innerTypeName, boolean onlyExplicit) {
 		JCClassDecl typeDecl = null;
 		if (typeNode.get() instanceof JCClassDecl) typeDecl = (JCClassDecl) typeNode.get();
 		
@@ -57,22 +62,31 @@ public class HandleFieldNameConstants extends JavacAnnotationHandler<FieldNameCo
 		boolean notAClass = (modifiers & (Flags.INTERFACE | Flags.ANNOTATION)) != 0;
 		
 		if (typeDecl == null || notAClass) {
-			errorNode.addError("@FieldNameConstants is only supported on a class, an enum, or a field.");
+			errorNode.addError("@FieldNameConstants is only supported on a class or an enum.");
 			return;
 		}
 		
+		java.util.List<JavacNode> qualified = new ArrayList<JavacNode>();
+		
 		for (JavacNode field : typeNode.down()) {
-			if (fieldQualifiesForFieldNameConstantsGeneration(field)) generateFieldNameConstantsForField(field, errorNode.get(), level, prefix, suffix);
+			if (fieldQualifiesForFieldNameConstantsGeneration(field, onlyExplicit)) qualified.add(field);
+		}
+		
+		if (qualified.isEmpty()) {
+			errorNode.addWarning("No fields qualify for @FieldNameConstants, therefore this annotation does nothing");
+		} else {
+			createInnerTypeFieldNameConstants(typeNode, errorNode.get(), level, qualified, asEnum, innerTypeName);
 		}
 	}
 	
-	private void generateFieldNameConstantsForField(JavacNode fieldNode, DiagnosticPosition pos, AccessLevel level, String prefix, String suffix) {
-		if (hasAnnotation(FieldNameConstants.class, fieldNode)) return;
-		createFieldNameConstantsForField(level, prefix, suffix, fieldNode, fieldNode, false);
-	}
-	
-	private boolean fieldQualifiesForFieldNameConstantsGeneration(JavacNode field) {
+	private boolean fieldQualifiesForFieldNameConstantsGeneration(JavacNode field, boolean onlyExplicit) {
 		if (field.getKind() != Kind.FIELD) return false;
+		boolean exclAnn = JavacHandlerUtil.hasAnnotationAndDeleteIfNeccessary(FieldNameConstants.Exclude.class, field);
+		boolean inclAnn = JavacHandlerUtil.hasAnnotationAndDeleteIfNeccessary(FieldNameConstants.Include.class, field);
+		if (exclAnn) return false;
+		if (inclAnn) return true;
+		if (onlyExplicit) return false;
+		
 		JCVariableDecl fieldDecl = (JCVariableDecl) field.get();
 		if (fieldDecl.name.toString().startsWith("$")) return false;
 		if ((fieldDecl.mods.flags & Flags.STATIC) != 0) return false;
@@ -82,56 +96,61 @@ public class HandleFieldNameConstants extends JavacAnnotationHandler<FieldNameCo
 	public void handle(AnnotationValues<FieldNameConstants> annotation, JCAnnotation ast, JavacNode annotationNode) {
 		handleExperimentalFlagUsage(annotationNode, ConfigurationKeys.FIELD_NAME_CONSTANTS_FLAG_USAGE, "@FieldNameConstants");
 		
-		Collection<JavacNode> fields = annotationNode.upFromAnnotationToFields();
 		deleteAnnotationIfNeccessary(annotationNode, FieldNameConstants.class);
 		deleteImportFromCompilationUnit(annotationNode, "lombok.AccessLevel");
 		JavacNode node = annotationNode.up();
-		FieldNameConstants annotatationInstance = annotation.getInstance();
-		AccessLevel level = annotatationInstance.level();
-		String prefix = annotatationInstance.prefix();
-		String suffix = annotatationInstance.suffix();
-		if (prefix.equals(" CONFIG DEFAULT ")) prefix = annotationNode.getAst().readConfiguration(ConfigurationKeys.FIELD_NAME_CONSTANTS_PREFIX);
-		if (suffix.equals(" CONFIG DEFAULT ")) suffix = annotationNode.getAst().readConfiguration(ConfigurationKeys.FIELD_NAME_CONSTANTS_SUFFIX);
-		if (prefix == null) prefix = "FIELD_";
-		if (suffix == null) suffix = "";
-		if (node == null) return;
-		switch (node.getKind()) {
-		case FIELD:
-			if (level != AccessLevel.NONE) createFieldNameConstantsForFields(level, prefix, suffix, fields, annotationNode, annotationNode, true);
-			break;
-		case TYPE:
-			if (level == AccessLevel.NONE) {
-				annotationNode.addWarning("type-level '@FieldNameConstants' does not work with AccessLevel.NONE.");
-				return;
-			}
-			generateFieldNameConstantsForType(node, annotationNode, level, prefix, suffix);
-			break;
-		}
-	}
-	
-	private void createFieldNameConstantsForFields(AccessLevel level, String prefix, String suffix, Collection<JavacNode> fieldNodes, JavacNode annotationNode, JavacNode errorNode, boolean whineIfExists) {
-		for (JavacNode fieldNode : fieldNodes) createFieldNameConstantsForField(level, prefix, suffix, fieldNode, errorNode, whineIfExists);
-	}
-	
-	private void createFieldNameConstantsForField(AccessLevel level, String prefix, String suffix, JavacNode fieldNode, JavacNode source, boolean whineIfExists) {
-		if (fieldNode.getKind() != Kind.FIELD) {
-			source.addError("@FieldNameConstants is only supported on a class, an enum, or a field");
+		FieldNameConstants annotationInstance = annotation.getInstance();
+		AccessLevel level = annotationInstance.level();
+		boolean asEnum = annotationInstance.asEnum();
+		boolean usingLombokv1_18_2 = annotation.isExplicit("prefix") || annotation.isExplicit("suffix") || node.getKind() == Kind.FIELD;
+		
+		if (usingLombokv1_18_2) {
+			annotationNode.addError("@FieldNameConstants has been redesigned in lombok v1.18.4; please upgrade your project dependency on lombok. See https://projectlombok.org/features/experimental/FieldNameConstants for more information.");
 			return;
 		}
 		
-		JCVariableDecl field = (JCVariableDecl) fieldNode.get();
-		String fieldName = field.name.toString();
-		String constantName = prefix + HandlerUtil.camelCaseToConstant(fieldName) + suffix;
-		if (constantName.equals(fieldName)) {
-			fieldNode.addWarning("Not generating constant for this field: The name of the constant would be equal to the name of this field.");
+		
+		if (level == AccessLevel.NONE) {
+			annotationNode.addWarning("AccessLevel.NONE is not compatible with @FieldNameConstants. If you don't want the inner type, simply remove @FieldNameConstants.");
 			return;
 		}
 		
-		JavacTreeMaker treeMaker = fieldNode.getTreeMaker();
-		JCModifiers modifiers = treeMaker.Modifiers(toJavacModifier(level) | Modifier.STATIC | Modifier.FINAL);
-		JCExpression returnType = chainDots(fieldNode, "java", "lang", "String");
-		JCExpression init = treeMaker.Literal(fieldNode.getName());
-		JCVariableDecl fieldConstant = treeMaker.VarDef(modifiers, fieldNode.toName(constantName), returnType, init);
-		injectField(fieldNode.up(), fieldConstant);
+		String innerTypeName = annotationInstance.innerTypeName();
+		if (innerTypeName.isEmpty()) innerTypeName = annotationNode.getAst().readConfiguration(ConfigurationKeys.FIELD_NAME_CONSTANTS_INNER_TYPE_NAME);
+		if (innerTypeName == null || innerTypeName.isEmpty()) innerTypeName = "Fields";
+		
+		generateFieldNameConstantsForType(node, annotationNode, level, asEnum, innerTypeName, annotationInstance.onlyExplicitlyIncluded());
+	}
+	
+	private void createInnerTypeFieldNameConstants(JavacNode typeNode, DiagnosticPosition pos, AccessLevel level, java.util.List<JavacNode> fields, boolean asEnum, String innerTypeName) {
+		if (fields.isEmpty()) return;
+		
+		JavacTreeMaker maker = typeNode.getTreeMaker();
+		JCModifiers mods = maker.Modifiers(toJavacModifier(level) | (asEnum ? Flags.ENUM : Flags.STATIC | Flags.FINAL));
+		
+		Name fieldsName = typeNode.toName(innerTypeName);
+		JCClassDecl innerType = maker.ClassDef(mods, fieldsName, List.<JCTypeParameter>nil(), null, List.<JCExpression>nil(), List.<JCTree>nil());
+		JavacNode innerNode = injectType(typeNode, innerType);
+		
+		JCModifiers genConstrMods = maker.Modifiers(Flags.GENERATEDCONSTR | (asEnum ? 0L : Flags.PRIVATE));
+		JCBlock genConstrBody = maker.Block(0L, List.<JCStatement>of(maker.Exec(maker.Apply(List.<JCExpression>nil(), maker.Ident(typeNode.toName("super")), List.<JCExpression>nil()))));
+		JCMethodDecl genConstr = maker.MethodDef(genConstrMods, typeNode.toName("<init>"), null, List.<JCTypeParameter>nil(), List.<JCVariableDecl>nil(), List.<JCExpression>nil(), genConstrBody, null);
+		
+		injectMethod(innerNode, genConstr);
+		
+		for (JavacNode field : fields) {
+			JCModifiers enumValueMods = maker.Modifiers(Flags.PUBLIC | Flags.STATIC | Flags.FINAL | (asEnum ? Flags.ENUM : 0L));
+			JCExpression returnType;
+			JCExpression init;
+			if (asEnum) {
+				returnType = maker.Ident(fieldsName);
+				init = maker.NewClass(null, List.<JCExpression>nil(), maker.Ident(fieldsName), List.<JCExpression>nil(), null);
+			} else {
+				returnType = chainDots(field, "java", "lang", "String");
+				init = maker.Literal(field.getName());
+			}
+			JCVariableDecl enumField = maker.VarDef(enumValueMods, ((JCVariableDecl) field.get()).name, returnType, init);
+			injectField(innerNode, enumField);
+		}
 	}
-}
\ No newline at end of file
+}