/*
 * Copyright (c) 1999, 2017, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package com.sun.tools.javac.code;

import java.lang.annotation.Annotation;
import java.lang.annotation.Inherited;
import java.util.Collections;
import java.util.EnumSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.Callable;

import javax.lang.model.element.Element;
import javax.lang.model.element.ElementKind;
import javax.lang.model.element.ElementVisitor;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.element.Modifier;
import javax.lang.model.element.ModuleElement;
import javax.lang.model.element.NestingKind;
import javax.lang.model.element.PackageElement;
import javax.lang.model.element.TypeElement;
import javax.lang.model.element.TypeParameterElement;
import javax.lang.model.element.VariableElement;
import javax.tools.JavaFileManager;
import javax.tools.JavaFileObject;

import com.sun.tools.javac.code.ClassFinder.BadEnclosingMethodAttr;
import com.sun.tools.javac.code.Directive.RequiresFlag;
import com.sun.tools.javac.code.Kinds.Kind;
import com.sun.tools.javac.comp.Annotate.AnnotationTypeMetadata;
import com.sun.tools.javac.code.Scope.WriteableScope;
import com.sun.tools.javac.code.Type.*;
import com.sun.tools.javac.comp.Attr;
import com.sun.tools.javac.comp.AttrContext;
import com.sun.tools.javac.comp.Env;
import com.sun.tools.javac.jvm.*;
import com.sun.tools.javac.tree.JCTree.JCFieldAccess;
import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
import com.sun.tools.javac.tree.JCTree.Tag;
import com.sun.tools.javac.util.*;
import com.sun.tools.javac.util.DefinedBy.Api;
import com.sun.tools.javac.util.Name;

import static com.sun.tools.javac.code.Flags.*;
import static com.sun.tools.javac.code.Kinds.*;
import static com.sun.tools.javac.code.Kinds.Kind.*;
import static com.sun.tools.javac.code.Scope.LookupKind.NON_RECURSIVE;
import static com.sun.tools.javac.code.Symbol.OperatorSymbol.AccessCode.FIRSTASGOP;
import static com.sun.tools.javac.code.TypeTag.CLASS;
import static com.sun.tools.javac.code.TypeTag.FORALL;
import static com.sun.tools.javac.code.TypeTag.TYPEVAR;
import static com.sun.tools.javac.jvm.ByteCodes.iadd;
import static com.sun.tools.javac.jvm.ByteCodes.ishll;
import static com.sun.tools.javac.jvm.ByteCodes.lushrl;
import static com.sun.tools.javac.jvm.ByteCodes.lxor;
import static com.sun.tools.javac.jvm.ByteCodes.string_add;

Root class for Java symbols. It contains subclasses
 for specific sorts of symbols, such as variables, methods and operators,
 types, packages. Each subclass is represented as a static inner class
 inside Symbol.
 
This is NOT part of any supported API.
 If you write code that depends on this, you do so at your own risk.
 This code and its internal interfaces are subject to change or
 deletion without notice.
/** Root class for Java symbols. It contains subclasses
 *  for specific sorts of symbols, such as variables, methods and operators,
 *  types, packages. Each subclass is represented as a static inner class
 *  inside Symbol.
 *
 *  <p><b>This is NOT part of any supported API.
 *  If you write code that depends on this, you do so at your own risk.
 *  This code and its internal interfaces are subject to change or
 *  deletion without notice.</b>
 */
public abstract class Symbol extends AnnoConstruct implements Element {

    
The kind of this symbol.
 @see Kinds
/** The kind of this symbol.
     *  @see Kinds
     */
    public Kind kind;

    
The flags of this symbol.
/** The flags of this symbol.
     */
    public long flags_field;

    
An accessor method for the flags of this symbol.
 Flags of class symbols should be accessed through the accessor
 method to make sure that the class symbol is loaded.
/** An accessor method for the flags of this symbol.
     *  Flags of class symbols should be accessed through the accessor
     *  method to make sure that the class symbol is loaded.
     */
    public long flags() { return flags_field; }

    
The name of this symbol in Utf8 representation.
/** The name of this symbol in Utf8 representation.
     */
    public Name name;

    
The type of this symbol.
/** The type of this symbol.
     */
    public Type type;

    
The owner of this symbol.
/** The owner of this symbol.
     */
    public Symbol owner;

    
The completer of this symbol.
This should never equal null (NULL_COMPLETER should be used instead).
/** The completer of this symbol.
     * This should never equal null (NULL_COMPLETER should be used instead).
     */
    public Completer completer;

    
A cache for the type erasure of this symbol.
/** A cache for the type erasure of this symbol.
     */
    public Type erasure_field;

    // <editor-fold defaultstate="collapsed" desc="annotations">

    
The attributes of this symbol are contained in this
SymbolMetadata. The SymbolMetadata instance is NOT immutable.
/** The attributes of this symbol are contained in this
     * SymbolMetadata. The SymbolMetadata instance is NOT immutable.
     */
    protected SymbolMetadata metadata;


    
An accessor method for the attributes of this symbol.
 Attributes of class symbols should be accessed through the accessor
 method to make sure that the class symbol is loaded.
/** An accessor method for the attributes of this symbol.
     *  Attributes of class symbols should be accessed through the accessor
     *  method to make sure that the class symbol is loaded.
     */
    public List<Attribute.Compound> getRawAttributes() {
        return (metadata == null)
                ? List.nil()
                : metadata.getDeclarationAttributes();
    }

    
An accessor method for the type attributes of this symbol.
 Attributes of class symbols should be accessed through the accessor
 method to make sure that the class symbol is loaded.
/** An accessor method for the type attributes of this symbol.
     *  Attributes of class symbols should be accessed through the accessor
     *  method to make sure that the class symbol is loaded.
     */
    public List<Attribute.TypeCompound> getRawTypeAttributes() {
        return (metadata == null)
                ? List.nil()
                : metadata.getTypeAttributes();
    }

    
Fetch a particular annotation from a symbol. /** Fetch a particular annotation from a symbol. */
    public Attribute.Compound attribute(Symbol anno) {
        for (Attribute.Compound a : getRawAttributes()) {
            if (a.type.tsym == anno) return a;
        }
        return null;
    }

    public boolean annotationsPendingCompletion() {
        return metadata == null ? false : metadata.pendingCompletion();
    }

    public void appendAttributes(List<Attribute.Compound> l) {
        if (l.nonEmpty()) {
            initedMetadata().append(l);
        }
    }

    public void appendClassInitTypeAttributes(List<Attribute.TypeCompound> l) {
        if (l.nonEmpty()) {
            initedMetadata().appendClassInitTypeAttributes(l);
        }
    }

    public void appendInitTypeAttributes(List<Attribute.TypeCompound> l) {
        if (l.nonEmpty()) {
            initedMetadata().appendInitTypeAttributes(l);
        }
    }

    public void appendUniqueTypeAttributes(List<Attribute.TypeCompound> l) {
        if (l.nonEmpty()) {
            initedMetadata().appendUniqueTypes(l);
        }
    }

    public List<Attribute.TypeCompound> getClassInitTypeAttributes() {
        return (metadata == null)
                ? List.nil()
                : metadata.getClassInitTypeAttributes();
    }

    public List<Attribute.TypeCompound> getInitTypeAttributes() {
        return (metadata == null)
                ? List.nil()
                : metadata.getInitTypeAttributes();
    }

    public void setInitTypeAttributes(List<Attribute.TypeCompound> l) {
        initedMetadata().setInitTypeAttributes(l);
    }

    public void setClassInitTypeAttributes(List<Attribute.TypeCompound> l) {
        initedMetadata().setClassInitTypeAttributes(l);
    }

    public List<Attribute.Compound> getDeclarationAttributes() {
        return (metadata == null)
                ? List.nil()
                : metadata.getDeclarationAttributes();
    }

    public boolean hasAnnotations() {
        return (metadata != null && !metadata.isEmpty());
    }

    public boolean hasTypeAnnotations() {
        return (metadata != null && !metadata.isTypesEmpty());
    }

    public boolean isCompleted() {
        return completer.isTerminal();
    }

    public void prependAttributes(List<Attribute.Compound> l) {
        if (l.nonEmpty()) {
            initedMetadata().prepend(l);
        }
    }

    public void resetAnnotations() {
        initedMetadata().reset();
    }

    public void setAttributes(Symbol other) {
        if (metadata != null || other.metadata != null) {
            initedMetadata().setAttributes(other.metadata);
        }
    }

    public void setDeclarationAttributes(List<Attribute.Compound> a) {
        if (metadata != null || a.nonEmpty()) {
            initedMetadata().setDeclarationAttributes(a);
        }
    }

    public void setTypeAttributes(List<Attribute.TypeCompound> a) {
        if (metadata != null || a.nonEmpty()) {
            if (metadata == null)
                metadata = new SymbolMetadata(this);
            metadata.setTypeAttributes(a);
        }
    }

    private SymbolMetadata initedMetadata() {
        if (metadata == null)
            metadata = new SymbolMetadata(this);
        return metadata;
    }

    
This method is intended for debugging only. /** This method is intended for debugging only. */
    public SymbolMetadata getMetadata() {
        return metadata;
    }

    // </editor-fold>

    
Construct a symbol with given kind, flags, name, type and owner.
/** Construct a symbol with given kind, flags, name, type and owner.
     */
    public Symbol(Kind kind, long flags, Name name, Type type, Symbol owner) {
        this.kind = kind;
        this.flags_field = flags;
        this.type = type;
        this.owner = owner;
        this.completer = Completer.NULL_COMPLETER;
        this.erasure_field = null;
        this.name = name;
    }

    
Clone this symbol with new owner.
 Legal only for fields and methods.
/** Clone this symbol with new owner.
     *  Legal only for fields and methods.
     */
    public Symbol clone(Symbol newOwner) {
        throw new AssertionError();
    }

    public <R, P> R accept(Symbol.Visitor<R, P> v, P p) {
        return v.visitSymbol(this, p);
    }

    
The Java source which this symbol represents.
 A description of this symbol; overrides Object.
/** The Java source which this symbol represents.
     *  A description of this symbol; overrides Object.
     */
    public String toString() {
        return name.toString();
    }

    
A Java source description of the location of this symbol; used for
 error reporting.
Returns:
null if the symbol is a package or a toplevel class defined in
the default package; otherwise, the owner symbol is returned/** A Java source description of the location of this symbol; used for
     *  error reporting.
     *
     * @return null if the symbol is a package or a toplevel class defined in
     * the default package; otherwise, the owner symbol is returned
     */
    public Symbol location() {
        if (owner.name == null || (owner.name.isEmpty() &&
                                   (owner.flags() & BLOCK) == 0 &&
                                   owner.kind != PCK &&
                                   owner.kind != TYP)) {
            return null;
        }
        return owner;
    }

    public Symbol location(Type site, Types types) {
        if (owner.name == null || owner.name.isEmpty()) {
            return location();
        }
        if (owner.type.hasTag(CLASS)) {
            Type ownertype = types.asOuterSuper(site, owner);
            if (ownertype != null) return ownertype.tsym;
        }
        return owner;
    }

    public Symbol baseSymbol() {
        return this;
    }

    
The symbol's erased type.
/** The symbol's erased type.
     */
    public Type erasure(Types types) {
        if (erasure_field == null)
            erasure_field = types.erasure(type);
        return erasure_field;
    }

    
The external type of a symbol. This is the symbol's erased type
 except for constructors of inner classes which get the enclosing
 instance class added as first argument.
/** The external type of a symbol. This is the symbol's erased type
     *  except for constructors of inner classes which get the enclosing
     *  instance class added as first argument.
     */
    public Type externalType(Types types) {
        Type t = erasure(types);
        if (name == name.table.names.init && owner.hasOuterInstance()) {
            Type outerThisType = types.erasure(owner.type.getEnclosingType());
            return new MethodType(t.getParameterTypes().prepend(outerThisType),
                                  t.getReturnType(),
                                  t.getThrownTypes(),
                                  t.tsym);
        } else {
            return t;
        }
    }

    public boolean isDeprecated() {
        return (flags_field & DEPRECATED) != 0;
    }

    public boolean hasDeprecatedAnnotation() {
        return (flags_field & DEPRECATED_ANNOTATION) != 0;
    }

    public boolean isDeprecatedForRemoval() {
        return (flags_field & DEPRECATED_REMOVAL) != 0;
    }

    public boolean isDeprecatableViaAnnotation() {
        switch (getKind()) {
            case LOCAL_VARIABLE:
            case PACKAGE:
            case PARAMETER:
            case RESOURCE_VARIABLE:
            case EXCEPTION_PARAMETER:
                return false;
            default:
                return true;
        }
    }

    public boolean isStatic() {
        return
            (flags() & STATIC) != 0 ||
            (owner.flags() & INTERFACE) != 0 && kind != MTH &&
             name != name.table.names._this;
    }

    public boolean isInterface() {
        return (flags() & INTERFACE) != 0;
    }

    public boolean isPrivate() {
        return (flags_field & Flags.AccessFlags) == PRIVATE;
    }

    public boolean isEnum() {
        return (flags() & ENUM) != 0;
    }

    
Is this symbol declared (directly or indirectly) local
 to a method or variable initializer?
 Also includes fields of inner classes which are in
 turn local to a method or variable initializer.
/** Is this symbol declared (directly or indirectly) local
     *  to a method or variable initializer?
     *  Also includes fields of inner classes which are in
     *  turn local to a method or variable initializer.
     */
    public boolean isLocal() {
        return
            (owner.kind.matches(KindSelector.VAL_MTH) ||
             (owner.kind == TYP && owner.isLocal()));
    }

    
Has this symbol an empty name? This includes anonymous
 inner classes.
/** Has this symbol an empty name? This includes anonymous
     *  inner classes.
     */
    public boolean isAnonymous() {
        return name.isEmpty();
    }

    
Is this symbol a constructor?
/** Is this symbol a constructor?
     */
    public boolean isConstructor() {
        return name == name.table.names.init;
    }

    
The fully qualified name of this symbol.
 This is the same as the symbol's name except for class symbols,
 which are handled separately.
/** The fully qualified name of this symbol.
     *  This is the same as the symbol's name except for class symbols,
     *  which are handled separately.
     */
    public Name getQualifiedName() {
        return name;
    }

    
The fully qualified name of this symbol after converting to flat
 representation. This is the same as the symbol's name except for
 class symbols, which are handled separately.
/** The fully qualified name of this symbol after converting to flat
     *  representation. This is the same as the symbol's name except for
     *  class symbols, which are handled separately.
     */
    public Name flatName() {
        return getQualifiedName();
    }

    
If this is a class or package, its members, otherwise null.
/** If this is a class or package, its members, otherwise null.
     */
    public WriteableScope members() {
        return null;
    }

    
A class is an inner class if it it has an enclosing instance class.
/** A class is an inner class if it it has an enclosing instance class.
     */
    public boolean isInner() {
        return kind == TYP && type.getEnclosingType().hasTag(CLASS);
    }

    
An inner class has an outer instance if it is not an interface
 it has an enclosing instance class which might be referenced from the class.
 Nested classes can see instance members of their enclosing class.
 Their constructors carry an additional this$n parameter, inserted
 implicitly by the compiler.
 @see #isInner
/** An inner class has an outer instance if it is not an interface
     *  it has an enclosing instance class which might be referenced from the class.
     *  Nested classes can see instance members of their enclosing class.
     *  Their constructors carry an additional this$n parameter, inserted
     *  implicitly by the compiler.
     *
     *  @see #isInner
     */
    public boolean hasOuterInstance() {
        return
            type.getEnclosingType().hasTag(CLASS) && (flags() & (INTERFACE | NOOUTERTHIS)) == 0;
    }

    
The closest enclosing class of this symbol's declaration.
 Warning: this (misnamed) method returns the receiver itself
 when the receiver is a class (as opposed to its enclosing
 class as one may be misled to believe.)
/** The closest enclosing class of this symbol's declaration.
     *  Warning: this (misnamed) method returns the receiver itself
     *  when the receiver is a class (as opposed to its enclosing
     *  class as one may be misled to believe.)
     */
    public ClassSymbol enclClass() {
        Symbol c = this;
        while (c != null &&
               (!c.kind.matches(KindSelector.TYP) || !c.type.hasTag(CLASS))) {
            c = c.owner;
        }
        return (ClassSymbol)c;
    }

    
The outermost class which indirectly owns this symbol.
/** The outermost class which indirectly owns this symbol.
     */
    public ClassSymbol outermostClass() {
        Symbol sym = this;
        Symbol prev = null;
        while (sym.kind != PCK) {
            prev = sym;
            sym = sym.owner;
        }
        return (ClassSymbol) prev;
    }

    
The package which indirectly owns this symbol.
/** The package which indirectly owns this symbol.
     */
    public PackageSymbol packge() {
        Symbol sym = this;
        while (sym.kind != PCK) {
            sym = sym.owner;
        }
        return (PackageSymbol) sym;
    }

    
Is this symbol a subclass of `base'? Only defined for ClassSymbols.
/** Is this symbol a subclass of `base'? Only defined for ClassSymbols.
     */
    public boolean isSubClass(Symbol base, Types types) {
        throw new AssertionError("isSubClass " + this);
    }

    
Fully check membership: hierarchy, protection, and hiding.
 Does not exclude methods not inherited due to overriding.
/** Fully check membership: hierarchy, protection, and hiding.
     *  Does not exclude methods not inherited due to overriding.
     */
    public boolean isMemberOf(TypeSymbol clazz, Types types) {
        return
            owner == clazz ||
            clazz.isSubClass(owner, types) &&
            isInheritedIn(clazz, types) &&
            !hiddenIn((ClassSymbol)clazz, types);
    }

    
Is this symbol the same as or enclosed by the given class? /** Is this symbol the same as or enclosed by the given class? */
    public boolean isEnclosedBy(ClassSymbol clazz) {
        for (Symbol sym = this; sym.kind != PCK; sym = sym.owner)
            if (sym == clazz) return true;
        return false;
    }

    private boolean hiddenIn(ClassSymbol clazz, Types types) {
        Symbol sym = hiddenInInternal(clazz, types);
        Assert.check(sym != null, "the result of hiddenInInternal() can't be null");
        /* If we find the current symbol then there is no symbol hiding it
         */
        return sym != this;
    }

    
This method looks in the supertypes graph that has the current class as the
initial node, till it finds the current symbol or another symbol that hides it.
If the current class has more than one supertype (extends one class and
implements one or more interfaces) then null can be returned, meaning that
a wrong path in the supertypes graph was selected. Null can only be returned
as a temporary value, as a result of the recursive call.
/** This method looks in the supertypes graph that has the current class as the
     * initial node, till it finds the current symbol or another symbol that hides it.
     * If the current class has more than one supertype (extends one class and
     * implements one or more interfaces) then null can be returned, meaning that
     * a wrong path in the supertypes graph was selected. Null can only be returned
     * as a temporary value, as a result of the recursive call.
     */
    private Symbol hiddenInInternal(ClassSymbol currentClass, Types types) {
        if (currentClass == owner) {
            return this;
        }
        for (Symbol sym : currentClass.members().getSymbolsByName(name)) {
            if (sym.kind == kind &&
                    (kind != MTH ||
                    (sym.flags() & STATIC) != 0 &&
                    types.isSubSignature(sym.type, type))) {
                return sym;
            }
        }
        Symbol hiddenSym = null;
        for (Type st : types.interfaces(currentClass.type)
                .prepend(types.supertype(currentClass.type))) {
            if (st != null && (st.hasTag(CLASS))) {
                Symbol sym = hiddenInInternal((ClassSymbol)st.tsym, types);
                if (sym == this) {
                    return this;
                } else if (sym != null) {
                    hiddenSym = sym;
                }
            }
        }
        return hiddenSym;
    }

    
Is this symbol inherited into a given class?
 PRE: If symbol's owner is a interface,
      it is already assumed that the interface is a superinterface
      of given class.
 @param clazz  The class for which we want to establish membership.
               This must be a subclass of the member's owner.
/** Is this symbol inherited into a given class?
     *  PRE: If symbol's owner is a interface,
     *       it is already assumed that the interface is a superinterface
     *       of given class.
     *  @param clazz  The class for which we want to establish membership.
     *                This must be a subclass of the member's owner.
     */
    public boolean isInheritedIn(Symbol clazz, Types types) {
        switch ((int)(flags_field & Flags.AccessFlags)) {
        default: // error recovery
        case PUBLIC:
            return true;
        case PRIVATE:
            return this.owner == clazz;
        case PROTECTED:
            // we model interfaces as extending Object
            return (clazz.flags() & INTERFACE) == 0;
        case 0:
            PackageSymbol thisPackage = this.packge();
            for (Symbol sup = clazz;
                 sup != null && sup != this.owner;
                 sup = types.supertype(sup.type).tsym) {
                while (sup.type.hasTag(TYPEVAR))
                    sup = sup.type.getUpperBound().tsym;
                if (sup.type.isErroneous())
                    return true; // error recovery
                if ((sup.flags() & COMPOUND) != 0)
                    continue;
                if (sup.packge() != thisPackage)
                    return false;
            }
            return (clazz.flags() & INTERFACE) == 0;
        }
    }

    
The (variable or method) symbol seen as a member of given
 class type`site' (this might change the symbol's type).
 This is used exclusively for producing diagnostics.
/** The (variable or method) symbol seen as a member of given
     *  class type`site' (this might change the symbol's type).
     *  This is used exclusively for producing diagnostics.
     */
    public Symbol asMemberOf(Type site, Types types) {
        throw new AssertionError();
    }

    
Does this method symbol override `other' symbol, when both are seen as
 members of class `origin'?  It is assumed that _other is a member
 of origin.
 It is assumed that both symbols have the same name.  The static
 modifier is ignored for this test.
 See JLS 8.4.6.1 (without transitivity) and 8.4.6.4
/** Does this method symbol override `other' symbol, when both are seen as
     *  members of class `origin'?  It is assumed that _other is a member
     *  of origin.
     *
     *  It is assumed that both symbols have the same name.  The static
     *  modifier is ignored for this test.
     *
     *  See JLS 8.4.6.1 (without transitivity) and 8.4.6.4
     */
    public boolean overrides(Symbol _other, TypeSymbol origin, Types types, boolean checkResult) {
        return false;
    }

    
Complete the elaboration of this symbol's definition.
/** Complete the elaboration of this symbol's definition.
     */
    public void complete() throws CompletionFailure {
        if (completer != Completer.NULL_COMPLETER) {
            Completer c = completer;
            completer = Completer.NULL_COMPLETER;
            c.complete(this);
        }
    }

    
True if the symbol represents an entity that exists.
/** True if the symbol represents an entity that exists.
     */
    public boolean exists() {
        return true;
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public Type asType() {
        return type;
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public Symbol getEnclosingElement() {
        return owner;
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public ElementKind getKind() {
        return ElementKind.OTHER;       // most unkind
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public Set<Modifier> getModifiers() {
        return Flags.asModifierSet(flags());
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public Name getSimpleName() {
        return name;
    }

    
This is the implementation for 
javax.lang.model.element.Element.getAnnotationMirrors(). /**
     * This is the implementation for {@code
     * javax.lang.model.element.Element.getAnnotationMirrors()}.
     */
    @Override @DefinedBy(Api.LANGUAGE_MODEL)
    public List<Attribute.Compound> getAnnotationMirrors() {
        return getRawAttributes();
    }


    // TODO: getEnclosedElements should return a javac List, fix in FilteredMemberList
    @DefinedBy(Api.LANGUAGE_MODEL)
    public java.util.List<Symbol> getEnclosedElements() {
        return List.nil();
    }

    public List<TypeVariableSymbol> getTypeParameters() {
        ListBuffer<TypeVariableSymbol> l = new ListBuffer<>();
        for (Type t : type.getTypeArguments()) {
            Assert.check(t.tsym.getKind() == ElementKind.TYPE_PARAMETER);
            l.append((TypeVariableSymbol)t.tsym);
        }
        return l.toList();
    }

    public static class DelegatedSymbol<T extends Symbol> extends Symbol {
        protected T other;
        public DelegatedSymbol(T other) {
            super(other.kind, other.flags_field, other.name, other.type, other.owner);
            this.other = other;
        }
        public String toString() { return other.toString(); }
        public Symbol location() { return other.location(); }
        public Symbol location(Type site, Types types) { return other.location(site, types); }
        public Symbol baseSymbol() { return other; }
        public Type erasure(Types types) { return other.erasure(types); }
        public Type externalType(Types types) { return other.externalType(types); }
        public boolean isLocal() { return other.isLocal(); }
        public boolean isConstructor() { return other.isConstructor(); }
        public Name getQualifiedName() { return other.getQualifiedName(); }
        public Name flatName() { return other.flatName(); }
        public WriteableScope members() { return other.members(); }
        public boolean isInner() { return other.isInner(); }
        public boolean hasOuterInstance() { return other.hasOuterInstance(); }
        public ClassSymbol enclClass() { return other.enclClass(); }
        public ClassSymbol outermostClass() { return other.outermostClass(); }
        public PackageSymbol packge() { return other.packge(); }
        public boolean isSubClass(Symbol base, Types types) { return other.isSubClass(base, types); }
        public boolean isMemberOf(TypeSymbol clazz, Types types) { return other.isMemberOf(clazz, types); }
        public boolean isEnclosedBy(ClassSymbol clazz) { return other.isEnclosedBy(clazz); }
        public boolean isInheritedIn(Symbol clazz, Types types) { return other.isInheritedIn(clazz, types); }
        public Symbol asMemberOf(Type site, Types types) { return other.asMemberOf(site, types); }
        public void complete() throws CompletionFailure { other.complete(); }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public <R, P> R accept(ElementVisitor<R, P> v, P p) {
            return other.accept(v, p);
        }

        public <R, P> R accept(Symbol.Visitor<R, P> v, P p) {
            return v.visitSymbol(other, p);
        }

        public T getUnderlyingSymbol() {
            return other;
        }
    }

    
A base class for Symbols representing types.
/** A base class for Symbols representing types.
     */
    public static abstract class TypeSymbol extends Symbol {
        public TypeSymbol(Kind kind, long flags, Name name, Type type, Symbol owner) {
            super(kind, flags, name, type, owner);
        }
        
form a fully qualified name from a name and an owner
/** form a fully qualified name from a name and an owner
         */
        static public Name formFullName(Name name, Symbol owner) {
            if (owner == null) return name;
            if ((owner.kind != ERR) &&
                (owner.kind.matches(KindSelector.VAL_MTH) ||
                 (owner.kind == TYP && owner.type.hasTag(TYPEVAR))
                 )) return name;
            Name prefix = owner.getQualifiedName();
            if (prefix == null || prefix == prefix.table.names.empty)
                return name;
            else return prefix.append('.', name);
        }

        
form a fully qualified name from a name and an owner, after
 converting to flat representation
/** form a fully qualified name from a name and an owner, after
         *  converting to flat representation
         */
        static public Name formFlatName(Name name, Symbol owner) {
            if (owner == null || owner.kind.matches(KindSelector.VAL_MTH) ||
                (owner.kind == TYP && owner.type.hasTag(TYPEVAR))
                ) return name;
            char sep = owner.kind == TYP ? '$' : '.';
            Name prefix = owner.flatName();
            if (prefix == null || prefix == prefix.table.names.empty)
                return name;
            else return prefix.append(sep, name);
        }

        
A partial ordering between type symbols that refines the
class inheritance graph.
Type variables always precede other kinds of symbols.
/**
         * A partial ordering between type symbols that refines the
         * class inheritance graph.
         *
         * Type variables always precede other kinds of symbols.
         */
        public final boolean precedes(TypeSymbol that, Types types) {
            if (this == that)
                return false;
            if (type.hasTag(that.type.getTag())) {
                if (type.hasTag(CLASS)) {
                    return
                        types.rank(that.type) < types.rank(this.type) ||
                        types.rank(that.type) == types.rank(this.type) &&
                        that.getQualifiedName().compareTo(this.getQualifiedName()) < 0;
                } else if (type.hasTag(TYPEVAR)) {
                    return types.isSubtype(this.type, that.type);
                }
            }
            return type.hasTag(TYPEVAR);
        }

        @Override @DefinedBy(Api.LANGUAGE_MODEL)
        public java.util.List<Symbol> getEnclosedElements() {
            List<Symbol> list = List.nil();
            if (kind == TYP && type.hasTag(TYPEVAR)) {
                return list;
            }
            for (Symbol sym : members().getSymbols(NON_RECURSIVE)) {
                try {
                    if (sym != null && (sym.flags() & SYNTHETIC) == 0 && sym.owner == this) {
                        list = list.prepend(sym);
                    }
                } catch (BadEnclosingMethodAttr badEnclosingMethod) {
                    // ignore the exception
                }
            }
            return list;
        }

        public AnnotationTypeMetadata getAnnotationTypeMetadata() {
            Assert.error("Only on ClassSymbol");
            return null; //unreachable
        }

        public boolean isAnnotationType() { return false; }

        @Override
        public <R, P> R accept(Symbol.Visitor<R, P> v, P p) {
            return v.visitTypeSymbol(this, p);
        }
    }

    
Type variables are represented by instances of this class.
/**
     * Type variables are represented by instances of this class.
     */
    public static class TypeVariableSymbol
            extends TypeSymbol implements TypeParameterElement {

        public TypeVariableSymbol(long flags, Name name, Type type, Symbol owner) {
            super(TYP, flags, name, type, owner);
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public ElementKind getKind() {
            return ElementKind.TYPE_PARAMETER;
        }

        @Override @DefinedBy(Api.LANGUAGE_MODEL)
        public Symbol getGenericElement() {
            return owner;
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public List<Type> getBounds() {
            TypeVar t = (TypeVar)type;
            Type bound = t.getUpperBound();
            if (!bound.isCompound())
                return List.of(bound);
            ClassType ct = (ClassType)bound;
            if (!ct.tsym.erasure_field.isInterface()) {
                return ct.interfaces_field.prepend(ct.supertype_field);
            } else {
                // No superclass was given in bounds.
                // In this case, supertype is Object, erasure is first interface.
                return ct.interfaces_field;
            }
        }

        @Override @DefinedBy(Api.LANGUAGE_MODEL)
        public List<Attribute.Compound> getAnnotationMirrors() {
            // Declaration annotations on type variables are stored in type attributes
            // on the owner of the TypeVariableSymbol
            List<Attribute.TypeCompound> candidates = owner.getRawTypeAttributes();
            int index = owner.getTypeParameters().indexOf(this);
            List<Attribute.Compound> res = List.nil();
            for (Attribute.TypeCompound a : candidates) {
                if (isCurrentSymbolsAnnotation(a, index))
                    res = res.prepend(a);
            }

            return res.reverse();
        }

        // Helper to getAnnotation[s]
        @Override
        public <A extends Annotation> Attribute.Compound getAttribute(Class<A> annoType) {
            String name = annoType.getName();

            // Declaration annotations on type variables are stored in type attributes
            // on the owner of the TypeVariableSymbol
            List<Attribute.TypeCompound> candidates = owner.getRawTypeAttributes();
            int index = owner.getTypeParameters().indexOf(this);
            for (Attribute.TypeCompound anno : candidates)
                if (isCurrentSymbolsAnnotation(anno, index) &&
                    name.contentEquals(anno.type.tsym.flatName()))
                    return anno;

            return null;
        }
            //where:
            boolean isCurrentSymbolsAnnotation(Attribute.TypeCompound anno, int index) {
                return (anno.position.type == TargetType.CLASS_TYPE_PARAMETER ||
                        anno.position.type == TargetType.METHOD_TYPE_PARAMETER) &&
                        anno.position.parameter_index == index;
            }


        @Override @DefinedBy(Api.LANGUAGE_MODEL)
        public <R, P> R accept(ElementVisitor<R, P> v, P p) {
            return v.visitTypeParameter(this, p);
        }
    }
    
A class for module symbols.
/** A class for module symbols.
     */
    public static class ModuleSymbol extends TypeSymbol
            implements ModuleElement {

        public Name version;
        public JavaFileManager.Location sourceLocation;
        public JavaFileManager.Location classLocation;
        public JavaFileManager.Location patchLocation;
        public JavaFileManager.Location patchOutputLocation;

        
All directives, in natural order. /** All directives, in natural order. */
        public List<com.sun.tools.javac.code.Directive> directives;
        public List<com.sun.tools.javac.code.Directive.RequiresDirective> requires;
        public List<com.sun.tools.javac.code.Directive.ExportsDirective> exports;
        public List<com.sun.tools.javac.code.Directive.OpensDirective> opens;
        public List<com.sun.tools.javac.code.Directive.ProvidesDirective> provides;
        public List<com.sun.tools.javac.code.Directive.UsesDirective> uses;

        public ClassSymbol module_info;

        public PackageSymbol unnamedPackage;
        public Map<Name, PackageSymbol> visiblePackages;
        public Set<ModuleSymbol> readModules;
        public List<Symbol> enclosedPackages = List.nil();

        public Completer usesProvidesCompleter = Completer.NULL_COMPLETER;
        public final Set<ModuleFlags> flags = EnumSet.noneOf(ModuleFlags.class);
        public final Set<ModuleResolutionFlags> resolutionFlags = EnumSet.noneOf(ModuleResolutionFlags.class);

        
Create a ModuleSymbol with an associated module-info ClassSymbol.
/**
         * Create a ModuleSymbol with an associated module-info ClassSymbol.
         */
        public static ModuleSymbol create(Name name, Name module_info) {
            ModuleSymbol msym = new ModuleSymbol(name, null);
            ClassSymbol info = new ClassSymbol(Flags.MODULE, module_info, msym);
            info.fullname = formFullName(module_info, msym);
            info.flatname = info.fullname;
            info.members_field = WriteableScope.create(info);
            msym.module_info = info;
            return msym;
        }

        public ModuleSymbol(Name name, Symbol owner) {
            super(MDL, 0, name, null, owner);
            Assert.checkNonNull(name);
            this.type = new ModuleType(this);
        }

        @Override @DefinedBy(Api.LANGUAGE_MODEL)
        public Name getSimpleName() {
            return Convert.shortName(name);
        }

        @Override @DefinedBy(Api.LANGUAGE_MODEL)
        public boolean isOpen() {
            return flags.contains(ModuleFlags.OPEN);
        }

        @Override @DefinedBy(Api.LANGUAGE_MODEL)
        public boolean isUnnamed() {
            return name.isEmpty() && owner == null;
        }

        @Override
        public boolean isDeprecated() {
            return hasDeprecatedAnnotation();
        }

        public boolean isNoModule() {
            return false;
        }

        @Override @DefinedBy(Api.LANGUAGE_MODEL)
        public ElementKind getKind() {
            return ElementKind.MODULE;
        }

        @Override @DefinedBy(Api.LANGUAGE_MODEL)
        public java.util.List<Directive> getDirectives() {
            complete();
            completeUsesProvides();
            return Collections.unmodifiableList(directives);
        }

        public void completeUsesProvides() {
            if (usesProvidesCompleter != Completer.NULL_COMPLETER) {
                Completer c = usesProvidesCompleter;
                usesProvidesCompleter = Completer.NULL_COMPLETER;
                c.complete(this);
            }
        }

        @Override
        public ClassSymbol outermostClass() {
            return null;
        }

        @Override
        public String toString() {
            // TODO: the following strings should be localized
            // Do this with custom anon subtypes in Symtab
            String n = (name == null) ? "<unknown>"
                    : (name.isEmpty()) ? "<unnamed>"
                    : String.valueOf(name);
            return n;
        }

        @Override @DefinedBy(Api.LANGUAGE_MODEL)
        public <R, P> R accept(ElementVisitor<R, P> v, P p) {
            return v.visitModule(this, p);
        }

        @Override @DefinedBy(Api.LANGUAGE_MODEL)
        public List<Symbol> getEnclosedElements() {
            List<Symbol> list = List.nil();
            for (Symbol sym : enclosedPackages) {
                if (sym.members().anyMatch(m -> m.kind == TYP))
                    list = list.prepend(sym);
            }
            return list;
        }

        public void reset() {
            this.directives = null;
            this.requires = null;
            this.exports = null;
            this.provides = null;
            this.uses = null;
            this.visiblePackages = null;
        }

    }

    public enum ModuleFlags {
        OPEN(0x0020),
        SYNTHETIC(0x1000),
        MANDATED(0x8000);

        public static int value(Set<ModuleFlags> s) {
            int v = 0;
            for (ModuleFlags f: s)
                v |= f.value;
            return v;
        }

        private ModuleFlags(int value) {
            this.value = value;
        }

        public final int value;
    }

    public enum ModuleResolutionFlags {
        DO_NOT_RESOLVE_BY_DEFAULT(0x0001),
        WARN_DEPRECATED(0x0002),
        WARN_DEPRECATED_REMOVAL(0x0004),
        WARN_INCUBATING(0x0008);

        public static int value(Set<ModuleResolutionFlags> s) {
            int v = 0;
            for (ModuleResolutionFlags f: s)
                v |= f.value;
            return v;
        }

        private ModuleResolutionFlags(int value) {
            this.value = value;
        }

        public final int value;
    }

    
A class for package symbols
/** A class for package symbols
     */
    public static class PackageSymbol extends TypeSymbol
        implements PackageElement {

        public WriteableScope members_field;
        public Name fullname;
        public ClassSymbol package_info; // see bug 6443073
        public ModuleSymbol modle;
        // the file containing the documentation comments for the package
        public JavaFileObject sourcefile;

        public PackageSymbol(Name name, Type type, Symbol owner) {
            super(PCK, 0, name, type, owner);
            this.members_field = null;
            this.fullname = formFullName(name, owner);
        }

        public PackageSymbol(Name name, Symbol owner) {
            this(name, null, owner);
            this.type = new PackageType(this);
        }

        public String toString() {
            return fullname.toString();
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public Name getQualifiedName() {
            return fullname;
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public boolean isUnnamed() {
            return name.isEmpty() && owner != null;
        }

        public WriteableScope members() {
            complete();
            return members_field;
        }

        public long flags() {
            complete();
            return flags_field;
        }

        @Override
        public List<Attribute.Compound> getRawAttributes() {
            complete();
            if (package_info != null) {
                package_info.complete();
                mergeAttributes();
            }
            return super.getRawAttributes();
        }

        private void mergeAttributes() {
            if (metadata == null &&
                package_info.metadata != null) {
                metadata = new SymbolMetadata(this);
                metadata.setAttributes(package_info.metadata);
            }
        }

        
A package "exists" if a type or package that exists has
 been seen within it.
/** A package "exists" if a type or package that exists has
         *  been seen within it.
         */
        public boolean exists() {
            return (flags_field & EXISTS) != 0;
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public ElementKind getKind() {
            return ElementKind.PACKAGE;
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public Symbol getEnclosingElement() {
            return modle != null && !modle.isNoModule() ? modle : null;
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public <R, P> R accept(ElementVisitor<R, P> v, P p) {
            return v.visitPackage(this, p);
        }

        public <R, P> R accept(Symbol.Visitor<R, P> v, P p) {
            return v.visitPackageSymbol(this, p);
        }

        
Resets the Symbol into the state good for next round of annotation processing./**Resets the Symbol into the state good for next round of annotation processing.*/
        public void reset() {
            metadata = null;
        }

    }

    
A class for class symbols
/** A class for class symbols
     */
    public static class ClassSymbol extends TypeSymbol implements TypeElement {

        
a scope for all class members; variables, methods and inner classes
 type parameters are not part of this scope
/** a scope for all class members; variables, methods and inner classes
         *  type parameters are not part of this scope
         */
        public WriteableScope members_field;

        
the fully qualified name of the class, i.e. pck.outer.inner.
 null for anonymous classes
/** the fully qualified name of the class, i.e. pck.outer.inner.
         *  null for anonymous classes
         */
        public Name fullname;

        
the fully qualified name of the class after converting to flat
 representation, i.e. pck.outer$inner,
 set externally for local and anonymous classes
/** the fully qualified name of the class after converting to flat
         *  representation, i.e. pck.outer$inner,
         *  set externally for local and anonymous classes
         */
        public Name flatname;

        
the sourcefile where the class came from
/** the sourcefile where the class came from
         */
        public JavaFileObject sourcefile;

        
the classfile from where to load this class
 this will have extension .class or .java
/** the classfile from where to load this class
         *  this will have extension .class or .java
         */
        public JavaFileObject classfile;

        
the list of translated local classes (used for generating
InnerClasses attribute)
/** the list of translated local classes (used for generating
         * InnerClasses attribute)
         */
        public List<ClassSymbol> trans_local;

        
the constant pool of the class
/** the constant pool of the class
         */
        public Pool pool;

        
the annotation metadata attached to this class /** the annotation metadata attached to this class */
        private AnnotationTypeMetadata annotationTypeMetadata;

        public ClassSymbol(long flags, Name name, Type type, Symbol owner) {
            super(TYP, flags, name, type, owner);
            this.members_field = null;
            this.fullname = formFullName(name, owner);
            this.flatname = formFlatName(name, owner);
            this.sourcefile = null;
            this.classfile = null;
            this.pool = null;
            this.annotationTypeMetadata = AnnotationTypeMetadata.notAnAnnotationType();
        }

        public ClassSymbol(long flags, Name name, Symbol owner) {
            this(
                flags,
                name,
                new ClassType(Type.noType, null, null),
                owner);
            this.type.tsym = this;
        }

        
The Java source which this symbol represents.
/** The Java source which this symbol represents.
         */
        public String toString() {
            return className();
        }

        public long flags() {
            complete();
            return flags_field;
        }

        public WriteableScope members() {
            complete();
            return members_field;
        }

        @Override
        public List<Attribute.Compound> getRawAttributes() {
            complete();
            return super.getRawAttributes();
        }

        @Override
        public List<Attribute.TypeCompound> getRawTypeAttributes() {
            complete();
            return super.getRawTypeAttributes();
        }

        public Type erasure(Types types) {
            if (erasure_field == null)
                erasure_field = new ClassType(types.erasure(type.getEnclosingType()),
                                              List.nil(), this,
                                              type.getMetadata());
            return erasure_field;
        }

        public String className() {
            if (name.isEmpty())
                return
                    Log.getLocalizedString("anonymous.class", flatname);
            else
                return fullname.toString();
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public Name getQualifiedName() {
            return fullname;
        }

        public Name flatName() {
            return flatname;
        }

        public boolean isSubClass(Symbol base, Types types) {
            if (this == base) {
                return true;
            } else if ((base.flags() & INTERFACE) != 0) {
                for (Type t = type; t.hasTag(CLASS); t = types.supertype(t))
                    for (List<Type> is = types.interfaces(t);
                         is.nonEmpty();
                         is = is.tail)
                        if (is.head.tsym.isSubClass(base, types)) return true;
            } else {
                for (Type t = type; t.hasTag(CLASS); t = types.supertype(t))
                    if (t.tsym == base) return true;
            }
            return false;
        }

        
Complete the elaboration of this symbol's definition.
/** Complete the elaboration of this symbol's definition.
         */
        public void complete() throws CompletionFailure {
            try {
                super.complete();
            } catch (CompletionFailure ex) {
                // quiet error recovery
                flags_field |= (PUBLIC|STATIC);
                this.type = new ErrorType(this, Type.noType);
                throw ex;
            }
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public List<Type> getInterfaces() {
            complete();
            if (type instanceof ClassType) {
                ClassType t = (ClassType)type;
                if (t.interfaces_field == null) // FIXME: shouldn't be null
                    t.interfaces_field = List.nil();
                if (t.all_interfaces_field != null)
                    return Type.getModelTypes(t.all_interfaces_field);
                return t.interfaces_field;
            } else {
                return List.nil();
            }
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public Type getSuperclass() {
            complete();
            if (type instanceof ClassType) {
                ClassType t = (ClassType)type;
                if (t.supertype_field == null) // FIXME: shouldn't be null
                    t.supertype_field = Type.noType;
                // An interface has no superclass; its supertype is Object.
                return t.isInterface()
                    ? Type.noType
                    : t.supertype_field.getModelType();
            } else {
                return Type.noType;
            }
        }

        
Returns the next class to search for inherited annotations or null if the next class can't be found. /**
         * Returns the next class to search for inherited annotations or {@code null}
         * if the next class can't be found.
         */
        private ClassSymbol getSuperClassToSearchForAnnotations() {

            Type sup = getSuperclass();

            if (!sup.hasTag(CLASS) || sup.isErroneous())
                return null;

            return (ClassSymbol) sup.tsym;
        }


        @Override
        protected <A extends Annotation> A[] getInheritedAnnotations(Class<A> annoType) {

            ClassSymbol sup = getSuperClassToSearchForAnnotations();

            return sup == null ? super.getInheritedAnnotations(annoType)
                               : sup.getAnnotationsByType(annoType);
        }


        @DefinedBy(Api.LANGUAGE_MODEL)
        public ElementKind getKind() {
            long flags = flags();
            if ((flags & ANNOTATION) != 0)
                return ElementKind.ANNOTATION_TYPE;
            else if ((flags & INTERFACE) != 0)
                return ElementKind.INTERFACE;
            else if ((flags & ENUM) != 0)
                return ElementKind.ENUM;
            else
                return ElementKind.CLASS;
        }

        @Override @DefinedBy(Api.LANGUAGE_MODEL)
        public Set<Modifier> getModifiers() {
            long flags = flags();
            return Flags.asModifierSet(flags & ~DEFAULT);
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public NestingKind getNestingKind() {
            complete();
            if (owner.kind == PCK)
                return NestingKind.TOP_LEVEL;
            else if (name.isEmpty())
                return NestingKind.ANONYMOUS;
            else if (owner.kind == MTH)
                return NestingKind.LOCAL;
            else
                return NestingKind.MEMBER;
        }


        @Override
        protected <A extends Annotation> Attribute.Compound getAttribute(final Class<A> annoType) {

            Attribute.Compound attrib = super.getAttribute(annoType);

            boolean inherited = annoType.isAnnotationPresent(Inherited.class);
            if (attrib != null || !inherited)
                return attrib;

            // Search supertypes
            ClassSymbol superType = getSuperClassToSearchForAnnotations();
            return superType == null ? null
                                     : superType.getAttribute(annoType);
        }




        @DefinedBy(Api.LANGUAGE_MODEL)
        public <R, P> R accept(ElementVisitor<R, P> v, P p) {
            return v.visitType(this, p);
        }

        public <R, P> R accept(Symbol.Visitor<R, P> v, P p) {
            return v.visitClassSymbol(this, p);
        }

        public void markAbstractIfNeeded(Types types) {
            if (types.enter.getEnv(this) != null &&
                (flags() & ENUM) != 0 && types.supertype(type).tsym == types.syms.enumSym &&
                (flags() & (FINAL | ABSTRACT)) == 0) {
                if (types.firstUnimplementedAbstract(this) != null)
                    // add the ABSTRACT flag to an enum
                    flags_field |= ABSTRACT;
            }
        }

        
Resets the Symbol into the state good for next round of annotation processing./**Resets the Symbol into the state good for next round of annotation processing.*/
        public void reset() {
            kind = TYP;
            erasure_field = null;
            members_field = null;
            flags_field = 0;
            if (type instanceof ClassType) {
                ClassType t = (ClassType)type;
                t.setEnclosingType(Type.noType);
                t.rank_field = -1;
                t.typarams_field = null;
                t.allparams_field = null;
                t.supertype_field = null;
                t.interfaces_field = null;
                t.all_interfaces_field = null;
            }
            clearAnnotationMetadata();
        }

        public void clearAnnotationMetadata() {
            metadata = null;
            annotationTypeMetadata = AnnotationTypeMetadata.notAnAnnotationType();
        }

        @Override
        public AnnotationTypeMetadata getAnnotationTypeMetadata() {
            return annotationTypeMetadata;
        }

        @Override
        public boolean isAnnotationType() {
            return (flags_field & Flags.ANNOTATION) != 0;
        }

        public void setAnnotationTypeMetadata(AnnotationTypeMetadata a) {
            Assert.checkNonNull(a);
            Assert.check(!annotationTypeMetadata.isMetadataForAnnotationType());
            this.annotationTypeMetadata = a;
        }
    }


    
A class for variable symbols
/** A class for variable symbols
     */
    public static class VarSymbol extends Symbol implements VariableElement {

        
The variable's declaration position.
/** The variable's declaration position.
         */
        public int pos = Position.NOPOS;

        
The variable's address. Used for different purposes during
 flow analysis, translation and code generation.
 Flow analysis:
   If this is a blank final or local variable, its sequence number.
 Translation:
   If this is a private field, its access number.
 Code generation:
   If this is a local variable, its logical slot number.
/** The variable's address. Used for different purposes during
         *  flow analysis, translation and code generation.
         *  Flow analysis:
         *    If this is a blank final or local variable, its sequence number.
         *  Translation:
         *    If this is a private field, its access number.
         *  Code generation:
         *    If this is a local variable, its logical slot number.
         */
        public int adr = -1;

        
Construct a variable symbol, given its flags, name, type and owner.
/** Construct a variable symbol, given its flags, name, type and owner.
         */
        public VarSymbol(long flags, Name name, Type type, Symbol owner) {
            super(VAR, flags, name, type, owner);
        }

        
Clone this symbol with new owner.
/** Clone this symbol with new owner.
         */
        public VarSymbol clone(Symbol newOwner) {
            VarSymbol v = new VarSymbol(flags_field, name, type, newOwner) {
                @Override
                public Symbol baseSymbol() {
                    return VarSymbol.this;
                }
            };
            v.pos = pos;
            v.adr = adr;
            v.data = data;
//          System.out.println("clone " + v + " in " + newOwner);//DEBUG
            return v;
        }

        public String toString() {
            return name.toString();
        }

        public Symbol asMemberOf(Type site, Types types) {
            return new VarSymbol(flags_field, name, types.memberType(site, this), owner);
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public ElementKind getKind() {
            long flags = flags();
            if ((flags & PARAMETER) != 0) {
                if (isExceptionParameter())
                    return ElementKind.EXCEPTION_PARAMETER;
                else
                    return ElementKind.PARAMETER;
            } else if ((flags & ENUM) != 0) {
                return ElementKind.ENUM_CONSTANT;
            } else if (owner.kind == TYP || owner.kind == ERR) {
                return ElementKind.FIELD;
            } else if (isResourceVariable()) {
                return ElementKind.RESOURCE_VARIABLE;
            } else {
                return ElementKind.LOCAL_VARIABLE;
            }
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public <R, P> R accept(ElementVisitor<R, P> v, P p) {
            return v.visitVariable(this, p);
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public Object getConstantValue() { // Mirror API
            return Constants.decode(getConstValue(), type);
        }

        public void setLazyConstValue(final Env<AttrContext> env,
                                      final Attr attr,
                                      final JCVariableDecl variable)
        {
            setData((Callable<Object>)() -> attr.attribLazyConstantValue(env, variable, type));
        }

        
The variable's constant value, if this is a constant.
Before the constant value is evaluated, it points to an
initializer environment.  If this is not a constant, it can
be used for other stuff.
/**
         * The variable's constant value, if this is a constant.
         * Before the constant value is evaluated, it points to an
         * initializer environment.  If this is not a constant, it can
         * be used for other stuff.
         */
        private Object data;

        public boolean isExceptionParameter() {
            return data == ElementKind.EXCEPTION_PARAMETER;
        }

        public boolean isResourceVariable() {
            return data == ElementKind.RESOURCE_VARIABLE;
        }

        public Object getConstValue() {
            // TODO: Consider if getConstValue and getConstantValue can be collapsed
            if (data == ElementKind.EXCEPTION_PARAMETER ||
                data == ElementKind.RESOURCE_VARIABLE) {
                return null;
            } else if (data instanceof Callable<?>) {
                // In this case, this is a final variable, with an as
                // yet unevaluated initializer.
                Callable<?> eval = (Callable<?>)data;
                data = null; // to make sure we don't evaluate this twice.
                try {
                    data = eval.call();
                } catch (Exception ex) {
                    throw new AssertionError(ex);
                }
            }
            return data;
        }

        public void setData(Object data) {
            Assert.check(!(data instanceof Env<?>), this);
            this.data = data;
        }

        public <R, P> R accept(Symbol.Visitor<R, P> v, P p) {
            return v.visitVarSymbol(this, p);
        }
    }

    
A class for method symbols.
/** A class for method symbols.
     */
    public static class MethodSymbol extends Symbol implements ExecutableElement {

        
The code of the method. /** The code of the method. */
        public Code code = null;

        
The extra (synthetic/mandated) parameters of the method. /** The extra (synthetic/mandated) parameters of the method. */
        public List<VarSymbol> extraParams = List.nil();

        
The captured local variables in an anonymous class /** The captured local variables in an anonymous class */
        public List<VarSymbol> capturedLocals = List.nil();

        
The parameters of the method. /** The parameters of the method. */
        public List<VarSymbol> params = null;

        
The names of the parameters /** The names of the parameters */
        public List<Name> savedParameterNames;

        
For an annotation type element, its default value if any.
 The value is null if none appeared in the method
 declaration.
/** For an annotation type element, its default value if any.
         *  The value is null if none appeared in the method
         *  declaration.
         */
        public Attribute defaultValue = null;

        
Construct a method symbol, given its flags, name, type and owner.
/** Construct a method symbol, given its flags, name, type and owner.
         */
        public MethodSymbol(long flags, Name name, Type type, Symbol owner) {
            super(MTH, flags, name, type, owner);
            if (owner.type.hasTag(TYPEVAR)) Assert.error(owner + "." + name);
        }

        
Clone this symbol with new owner.
/** Clone this symbol with new owner.
         */
        public MethodSymbol clone(Symbol newOwner) {
            MethodSymbol m = new MethodSymbol(flags_field, name, type, newOwner) {
                @Override
                public Symbol baseSymbol() {
                    return MethodSymbol.this;
                }
            };
            m.code = code;
            return m;
        }

        @Override @DefinedBy(Api.LANGUAGE_MODEL)
        public Set<Modifier> getModifiers() {
            long flags = flags();
            return Flags.asModifierSet((flags & DEFAULT) != 0 ? flags & ~ABSTRACT : flags);
        }

        
The Java source which this symbol represents.
/** The Java source which this symbol represents.
         */
        public String toString() {
            if ((flags() & BLOCK) != 0) {
                return owner.name.toString();
            } else {
                String s = (name == name.table.names.init)
                    ? owner.name.toString()
                    : name.toString();
                if (type != null) {
                    if (type.hasTag(FORALL))
                        s = "<" + ((ForAll)type).getTypeArguments() + ">" + s;
                    s += "(" + type.argtypes((flags() & VARARGS) != 0) + ")";
                }
                return s;
            }
        }

        public boolean isDynamic() {
            return false;
        }

        
find a symbol that this (proxy method) symbol implements.
 @param    c       The class whose members are searched for
                   implementations
/** find a symbol that this (proxy method) symbol implements.
         *  @param    c       The class whose members are searched for
         *                    implementations
         */
        public Symbol implemented(TypeSymbol c, Types types) {
            Symbol impl = null;
            for (List<Type> is = types.interfaces(c.type);
                 impl == null && is.nonEmpty();
                 is = is.tail) {
                TypeSymbol i = is.head.tsym;
                impl = implementedIn(i, types);
                if (impl == null)
                    impl = implemented(i, types);
            }
            return impl;
        }

        public Symbol implementedIn(TypeSymbol c, Types types) {
            Symbol impl = null;
            for (Symbol sym : c.members().getSymbolsByName(name)) {
                if (this.overrides(sym, (TypeSymbol)owner, types, true) &&
                    // FIXME: I suspect the following requires a
                    // subst() for a parametric return type.
                    types.isSameType(type.getReturnType(),
                                     types.memberType(owner.type, sym).getReturnType())) {
                    impl = sym;
                }
            }
            return impl;
        }

        
Will the erasure of this method be considered by the VM to
 override the erasure of the other when seen from class `origin'?
/** Will the erasure of this method be considered by the VM to
         *  override the erasure of the other when seen from class `origin'?
         */
        public boolean binaryOverrides(Symbol _other, TypeSymbol origin, Types types) {
            if (isConstructor() || _other.kind != MTH) return false;

            if (this == _other) return true;
            MethodSymbol other = (MethodSymbol)_other;

            // check for a direct implementation
            if (other.isOverridableIn((TypeSymbol)owner) &&
                types.asSuper(owner.type, other.owner) != null &&
                types.isSameType(erasure(types), other.erasure(types)))
                return true;

            // check for an inherited implementation
            return
                (flags() & ABSTRACT) == 0 &&
                other.isOverridableIn(origin) &&
                this.isMemberOf(origin, types) &&
                types.isSameType(erasure(types), other.erasure(types));
        }

        
The implementation of this (abstract) symbol in class origin,
 from the VM's point of view, null if method does not have an
 implementation in class.
 @param origin   The class of which the implementation is a member.
/** The implementation of this (abstract) symbol in class origin,
         *  from the VM's point of view, null if method does not have an
         *  implementation in class.
         *  @param origin   The class of which the implementation is a member.
         */
        public MethodSymbol binaryImplementation(ClassSymbol origin, Types types) {
            for (TypeSymbol c = origin; c != null; c = types.supertype(c.type).tsym) {
                for (Symbol sym : c.members().getSymbolsByName(name)) {
                    if (sym.kind == MTH &&
                        ((MethodSymbol)sym).binaryOverrides(this, origin, types))
                        return (MethodSymbol)sym;
                }
            }
            return null;
        }

        
Does this symbol override `other' symbol, when both are seen as
 members of class `origin'?  It is assumed that _other is a member
 of origin.
 It is assumed that both symbols have the same name.  The static
 modifier is ignored for this test.
 A quirk in the works is that if the receiver is a method symbol for
 an inherited abstract method we answer false summarily all else being
 immaterial. Abstract "own" methods (i.e `this' is a direct member of
 origin) don't get rejected as summarily and are put to test against the
 suitable criteria.
 See JLS 8.4.6.1 (without transitivity) and 8.4.6.4
/** Does this symbol override `other' symbol, when both are seen as
         *  members of class `origin'?  It is assumed that _other is a member
         *  of origin.
         *
         *  It is assumed that both symbols have the same name.  The static
         *  modifier is ignored for this test.
         *
         *  A quirk in the works is that if the receiver is a method symbol for
         *  an inherited abstract method we answer false summarily all else being
         *  immaterial. Abstract "own" methods (i.e `this' is a direct member of
         *  origin) don't get rejected as summarily and are put to test against the
         *  suitable criteria.
         *
         *  See JLS 8.4.6.1 (without transitivity) and 8.4.6.4
         */
        public boolean overrides(Symbol _other, TypeSymbol origin, Types types, boolean checkResult) {
            return overrides(_other, origin, types, checkResult, true);
        }

        
Does this symbol override `other' symbol, when both are seen as
 members of class `origin'?  It is assumed that _other is a member
 of origin.
 Caveat: If `this' is an abstract inherited member of origin, it is
 deemed to override `other' only when `requireConcreteIfInherited'
 is false.
 It is assumed that both symbols have the same name.  The static
 modifier is ignored for this test.
 See JLS 8.4.6.1 (without transitivity) and 8.4.6.4
/** Does this symbol override `other' symbol, when both are seen as
         *  members of class `origin'?  It is assumed that _other is a member
         *  of origin.
         *
         *  Caveat: If `this' is an abstract inherited member of origin, it is
         *  deemed to override `other' only when `requireConcreteIfInherited'
         *  is false.
         *
         *  It is assumed that both symbols have the same name.  The static
         *  modifier is ignored for this test.
         *
         *  See JLS 8.4.6.1 (without transitivity) and 8.4.6.4
         */
        public boolean overrides(Symbol _other, TypeSymbol origin, Types types, boolean checkResult,
                                            boolean requireConcreteIfInherited) {
            if (isConstructor() || _other.kind != MTH) return false;

            if (this == _other) return true;
            MethodSymbol other = (MethodSymbol)_other;

            // check for a direct implementation
            if (other.isOverridableIn((TypeSymbol)owner) &&
                types.asSuper(owner.type, other.owner) != null) {
                Type mt = types.memberType(owner.type, this);
                Type ot = types.memberType(owner.type, other);
                if (types.isSubSignature(mt, ot)) {
                    if (!checkResult)
                        return true;
                    if (types.returnTypeSubstitutable(mt, ot))
                        return true;
                }
            }

            // check for an inherited implementation
            if (((flags() & ABSTRACT) != 0 && requireConcreteIfInherited) ||
                    ((other.flags() & ABSTRACT) == 0 && (other.flags() & DEFAULT) == 0) ||
                    !other.isOverridableIn(origin) ||
                    !this.isMemberOf(origin, types))
                return false;

            // assert types.asSuper(origin.type, other.owner) != null;
            Type mt = types.memberType(origin.type, this);
            Type ot = types.memberType(origin.type, other);
            return
                types.isSubSignature(mt, ot) &&
                (!checkResult || types.resultSubtype(mt, ot, types.noWarnings));
        }

        private boolean isOverridableIn(TypeSymbol origin) {
            // JLS 8.4.6.1
            switch ((int)(flags_field & Flags.AccessFlags)) {
            case Flags.PRIVATE:
                return false;
            case Flags.PUBLIC:
                return !this.owner.isInterface() ||
                        (flags_field & STATIC) == 0;
            case Flags.PROTECTED:
                return (origin.flags() & INTERFACE) == 0;
            case 0:
                // for package private: can only override in the same
                // package
                return
                    this.packge() == origin.packge() &&
                    (origin.flags() & INTERFACE) == 0;
            default:
                return false;
            }
        }

        @Override
        public boolean isInheritedIn(Symbol clazz, Types types) {
            switch ((int)(flags_field & Flags.AccessFlags)) {
                case PUBLIC:
                    return !this.owner.isInterface() ||
                            clazz == owner ||
                            (flags_field & STATIC) == 0;
                default:
                    return super.isInheritedIn(clazz, types);
            }
        }

        public boolean isLambdaMethod() {
            return (flags() & LAMBDA_METHOD) == LAMBDA_METHOD;
        }

        
The implementation of this (abstract) symbol in class origin;
 null if none exists. Synthetic methods are not considered
 as possible implementations.
/** The implementation of this (abstract) symbol in class origin;
         *  null if none exists. Synthetic methods are not considered
         *  as possible implementations.
         */
        public MethodSymbol implementation(TypeSymbol origin, Types types, boolean checkResult) {
            return implementation(origin, types, checkResult, implementation_filter);
        }
        // where
            public static final Filter<Symbol> implementation_filter = s ->
                    s.kind == MTH && (s.flags() & SYNTHETIC) == 0;

        public MethodSymbol implementation(TypeSymbol origin, Types types, boolean checkResult, Filter<Symbol> implFilter) {
            MethodSymbol res = types.implementation(this, origin, checkResult, implFilter);
            if (res != null)
                return res;
            // if origin is derived from a raw type, we might have missed
            // an implementation because we do not know enough about instantiations.
            // in this case continue with the supertype as origin.
            if (types.isDerivedRaw(origin.type) && !origin.isInterface())
                return implementation(types.supertype(origin.type).tsym, types, checkResult);
            else
                return null;
        }

        public List<VarSymbol> params() {
            owner.complete();
            if (params == null) {
                // If ClassReader.saveParameterNames has been set true, then
                // savedParameterNames will be set to a list of names that
                // matches the types in type.getParameterTypes().  If any names
                // were not found in the class file, those names in the list will
                // be set to the empty name.
                // If ClassReader.saveParameterNames has been set false, then
                // savedParameterNames will be null.
                List<Name> paramNames = savedParameterNames;
                savedParameterNames = null;
                // discard the provided names if the list of names is the wrong size.
                if (paramNames == null || paramNames.size() != type.getParameterTypes().size()) {
                    paramNames = List.nil();
                }
                ListBuffer<VarSymbol> buf = new ListBuffer<>();
                List<Name> remaining = paramNames;
                // assert: remaining and paramNames are both empty or both
                // have same cardinality as type.getParameterTypes()
                int i = 0;
                for (Type t : type.getParameterTypes()) {
                    Name paramName;
                    if (remaining.isEmpty()) {
                        // no names for any parameters available
                        paramName = createArgName(i, paramNames);
                    } else {
                        paramName = remaining.head;
                        remaining = remaining.tail;
                        if (paramName.isEmpty()) {
                            // no name for this specific parameter
                            paramName = createArgName(i, paramNames);
                        }
                    }
                    buf.append(new VarSymbol(PARAMETER, paramName, t, this));
                    i++;
                }
                params = buf.toList();
            }
            return params;
        }

        // Create a name for the argument at position 'index' that is not in
        // the exclude list. In normal use, either no names will have been
        // provided, in which case the exclude list is empty, or all the names
        // will have been provided, in which case this method will not be called.
        private Name createArgName(int index, List<Name> exclude) {
            String prefix = "arg";
            while (true) {
                Name argName = name.table.fromString(prefix + index);
                if (!exclude.contains(argName))
                    return argName;
                prefix += "$";
            }
        }

        public Symbol asMemberOf(Type site, Types types) {
            return new MethodSymbol(flags_field, name, types.memberType(site, this), owner);
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public ElementKind getKind() {
            if (name == name.table.names.init)
                return ElementKind.CONSTRUCTOR;
            else if (name == name.table.names.clinit)
                return ElementKind.STATIC_INIT;
            else if ((flags() & BLOCK) != 0)
                return isStatic() ? ElementKind.STATIC_INIT : ElementKind.INSTANCE_INIT;
            else
                return ElementKind.METHOD;
        }

        public boolean isStaticOrInstanceInit() {
            return getKind() == ElementKind.STATIC_INIT ||
                    getKind() == ElementKind.INSTANCE_INIT;
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public Attribute getDefaultValue() {
            return defaultValue;
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public List<VarSymbol> getParameters() {
            return params();
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public boolean isVarArgs() {
            return (flags() & VARARGS) != 0;
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public boolean isDefault() {
            return (flags() & DEFAULT) != 0;
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public <R, P> R accept(ElementVisitor<R, P> v, P p) {
            return v.visitExecutable(this, p);
        }

        public <R, P> R accept(Symbol.Visitor<R, P> v, P p) {
            return v.visitMethodSymbol(this, p);
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public Type getReceiverType() {
            return asType().getReceiverType();
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public Type getReturnType() {
            return asType().getReturnType();
        }

        @DefinedBy(Api.LANGUAGE_MODEL)
        public List<Type> getThrownTypes() {
            return asType().getThrownTypes();
        }
    }

    
A class for invokedynamic method calls.
/** A class for invokedynamic method calls.
     */
    public static class DynamicMethodSymbol extends MethodSymbol {

        public Object[] staticArgs;
        public Symbol bsm;
        public int bsmKind;

        public DynamicMethodSymbol(Name name, Symbol owner, int bsmKind, MethodSymbol bsm, Type type, Object[] staticArgs) {
            super(0, name, type, owner);
            this.bsm = bsm;
            this.bsmKind = bsmKind;
            this.staticArgs = staticArgs;
        }

        @Override
        public boolean isDynamic() {
            return true;
        }
    }

    
A class for predefined operators.
/** A class for predefined operators.
     */
    public static class OperatorSymbol extends MethodSymbol {

        public int opcode;
        private int accessCode = Integer.MIN_VALUE;

        public OperatorSymbol(Name name, Type type, int opcode, Symbol owner) {
            super(PUBLIC | STATIC, name, type, owner);
            this.opcode = opcode;
        }

        @Override
        public <R, P> R accept(Symbol.Visitor<R, P> v, P p) {
            return v.visitOperatorSymbol(this, p);
        }

        public int getAccessCode(Tag tag) {
            if (accessCode != Integer.MIN_VALUE && !tag.isIncOrDecUnaryOp()) {
                return accessCode;
            }
            accessCode = AccessCode.from(tag, opcode);
            return accessCode;
        }

        
Access codes for dereferencing, assignment,
 and pre/post increment/decrement.
 All access codes for accesses to the current class are even.
 If a member of the superclass should be accessed instead (because
 access was via a qualified super), add one to the corresponding code
 for the current class, making the number odd.
 This numbering scheme is used by the backend to decide whether
 to issue an invokevirtual or invokespecial call.
 @see Gen#visitSelect(JCFieldAccess tree)
/** Access codes for dereferencing, assignment,
         *  and pre/post increment/decrement.

         *  All access codes for accesses to the current class are even.
         *  If a member of the superclass should be accessed instead (because
         *  access was via a qualified super), add one to the corresponding code
         *  for the current class, making the number odd.
         *  This numbering scheme is used by the backend to decide whether
         *  to issue an invokevirtual or invokespecial call.
         *
         *  @see Gen#visitSelect(JCFieldAccess tree)
         */
        public enum AccessCode {
            UNKNOWN(-1, Tag.NO_TAG),
            DEREF(0, Tag.NO_TAG),
            ASSIGN(2, Tag.ASSIGN),
            PREINC(4, Tag.PREINC),
            PREDEC(6, Tag.PREDEC),
            POSTINC(8, Tag.POSTINC),
            POSTDEC(10, Tag.POSTDEC),
            FIRSTASGOP(12, Tag.NO_TAG);

            public final int code;
            public final Tag tag;
            public static final int numberOfAccessCodes = (lushrl - ishll + lxor + 2 - iadd) * 2 + FIRSTASGOP.code + 2;

            AccessCode(int code, Tag tag) {
                this.code = code;
                this.tag = tag;
            }

            static public AccessCode getFromCode(int code) {
                for (AccessCode aCodes : AccessCode.values()) {
                    if (aCodes.code == code) {
                        return aCodes;
                    }
                }
                return UNKNOWN;
            }

            static int from(Tag tag, int opcode) {
                /** Map bytecode of binary operation to access code of corresponding
                *  assignment operation. This is always an even number.
                */
                switch (tag) {
                    case PREINC:
                        return AccessCode.PREINC.code;
                    case PREDEC:
                        return AccessCode.PREDEC.code;
                    case POSTINC:
                        return AccessCode.POSTINC.code;
                    case POSTDEC:
                        return AccessCode.POSTDEC.code;
                }
                if (iadd <= opcode && opcode <= lxor) {
                    return (opcode - iadd) * 2 + FIRSTASGOP.code;
                } else if (opcode == string_add) {
                    return (lxor + 1 - iadd) * 2 + FIRSTASGOP.code;
                } else if (ishll <= opcode && opcode <= lushrl) {
                    return (opcode - ishll + lxor + 2 - iadd) * 2 + FIRSTASGOP.code;
                }
                return -1;
            }
        }
    }

    
Symbol completer interface.
/** Symbol completer interface.
     */
    public static interface Completer {

        
Dummy completer to be used when the symbol has been completed or
does not need completion.
/** Dummy completer to be used when the symbol has been completed or
         * does not need completion.
         */
        public final static Completer NULL_COMPLETER = new Completer() {
            public void complete(Symbol sym) { }
            public boolean isTerminal() { return true; }
        };

        void complete(Symbol sym) throws CompletionFailure;

        
Returns true if this completer is terminal. A terminal
completer is used as a place holder when the symbol is completed.
Calling complete on a terminal completer will not affect the symbol.
The dummy NULL_COMPLETER and the GraphDependencies completer are
examples of terminal completers.
Returns:
true iff this completer is terminal/** Returns true if this completer is <em>terminal</em>. A terminal
         * completer is used as a place holder when the symbol is completed.
         * Calling complete on a terminal completer will not affect the symbol.
         *
         * The dummy NULL_COMPLETER and the GraphDependencies completer are
         * examples of terminal completers.
         *
         * @return true iff this completer is terminal
         */
        default boolean isTerminal() {
            return false;
        }
    }

    public static class CompletionFailure extends RuntimeException {
        private static final long serialVersionUID = 0;
        public Symbol sym;

        
A diagnostic object describing the failure
/** A diagnostic object describing the failure
         */
        public JCDiagnostic diag;

        public CompletionFailure(Symbol sym, JCDiagnostic diag) {
            this.sym = sym;
            this.diag = diag;
//          this.printStackTrace();//DEBUG
        }

        public JCDiagnostic getDiagnostic() {
            return diag;
        }

        @Override
        public String getMessage() {
            return diag.getMessage(null);
        }

        public JCDiagnostic getDetailValue() {
            return diag;
        }

        @Override
        public CompletionFailure initCause(Throwable cause) {
            super.initCause(cause);
            return this;
        }

    }

    
A visitor for symbols.  A visitor is used to implement operations
(or relations) on symbols.  Most common operations on types are
binary relations and this interface is designed for binary
relations, that is, operations on the form
Symbol × P → R.

Type parameters:
<R> – the return type of the operation implemented by this
visitor; use Void if no return type is needed.
<P> – the type of the second argument (the first being the
symbol itself) of the operation implemented by this visitor; use
Void if a second argument is not needed./**
     * A visitor for symbols.  A visitor is used to implement operations
     * (or relations) on symbols.  Most common operations on types are
     * binary relations and this interface is designed for binary
     * relations, that is, operations on the form
     * Symbol&nbsp;&times;&nbsp;P&nbsp;&rarr;&nbsp;R.
     * <!-- In plain text: Type x P -> R -->
     *
     * @param <R> the return type of the operation implemented by this
     * visitor; use Void if no return type is needed.
     * @param <P> the type of the second argument (the first being the
     * symbol itself) of the operation implemented by this visitor; use
     * Void if a second argument is not needed.
     */
    public interface Visitor<R,P> {
        R visitClassSymbol(ClassSymbol s, P arg);
        R visitMethodSymbol(MethodSymbol s, P arg);
        R visitPackageSymbol(PackageSymbol s, P arg);
        R visitOperatorSymbol(OperatorSymbol s, P arg);
        R visitVarSymbol(VarSymbol s, P arg);
        R visitTypeSymbol(TypeSymbol s, P arg);
        R visitSymbol(Symbol s, P arg);
    }
}