path: root/sources/scalac/symtab/Symbol.java

/*     ____ ____  ____ ____  ______                                     *\
**    / __// __ \/ __// __ \/ ____/    SOcos COmpiles Scala             **
**  __\_ \/ /_/ / /__/ /_/ /\_ \       (c) 2002, LAMP/EPFL              **
** /_____/\____/\___/\____/____/                                        **
**
** $Id$
\*                                                                      */

//todo check significance of JAVA flag.

package scalac.symtab;

import ch.epfl.lamp.util.Position;
import scalac.ApplicationError;
import scalac.Global;
import scalac.Phase;
import scalac.util.ArrayApply;
import scalac.util.Name;
import scalac.util.Names;
import scalac.util.NameTransformer;
import scalac.util.Debug;
import scalac.symtab.classfile.*;


public abstract class Symbol implements Modifiers, Kinds {

    /** An empty symbol array */
    public static final Symbol[] EMPTY_ARRAY = new Symbol[0];

    /** An empty array of symbol arrays */
    public static final Symbol[][] EMPTY_ARRAY_ARRAY = new Symbol[0][];

    /** The error symbol */
    public static final ErrorSymbol ERROR = new ErrorSymbol();

    /** The absent symbol */
    public static final NoSymbol NONE = new NoSymbol();

// Fields -------------------------------------------------------------

    /** The kind of the symbol */
    public int kind;

    /** The position of the symbol */
    public int pos;

    /** The name of the symbol */
    public Name name;

    /** The modifiers of the symbol */
    public int flags;

    /** The owner of the symbol */
    private Symbol owner;

    /** The infos of the symbol */
    private TypeIntervalList infos;

// Constructors -----------------------------------------------------------

    /** Generic symbol constructor */
    public Symbol(int kind, int pos, Name name, Symbol owner, int flags) {
        this.kind = kind;
        this.pos = pos;
        this.name = name;
        this.owner = owner;
        this.flags = flags & ~(INITIALIZED | LOCKED); // safety first
    }

    protected void update(int pos, int flags) {
        this.pos = pos;
        this.flags = (flags & ~(INITIALIZED | LOCKED)) |
            (this.flags & (INITIALIZED | LOCKED));
    }

    /** Return a fresh symbol with the same fields as this one.
     */
    public final Symbol cloneSymbol() {
        return cloneSymbol(owner);
    }

    /** Return a fresh symbol with the same fields as this one and the
     * given owner.
     */
    public abstract Symbol cloneSymbol(Symbol owner);

    /** Returns a shallow copy of the given array. */
    public static Symbol[] cloneArray(Symbol[] array) {
        return cloneArray(0, array, 0);
    }

    /**
     * Returns a shallow copy of the given array prefixed by "prefix"
     * null items.
     */
    public static Symbol[] cloneArray(int prefix, Symbol[] array) {
        return cloneArray(prefix, array, 0);
    }

    /**
     * Returns a shallow copy of the given array suffixed by "suffix"
     * null items.
     */
    public static Symbol[] cloneArray(Symbol[] array, int suffix) {
        return cloneArray(0, array, suffix);
    }

    /**
     * Returns a shallow copy of the given array prefixed by "prefix"
     * null items and suffixed by "suffix" null items.
     */
    public static Symbol[] cloneArray(int prefix, Symbol[] array, int suffix) {
        assert prefix >= 0 && suffix >= 0: prefix + " - " + suffix;
        int size = prefix + array.length + suffix;
        if (size == 0) return EMPTY_ARRAY;
        Symbol[] clone = new Symbol[size];
        for (int i = 0; i < array.length; i++) clone[prefix + i] = array[i];
        return clone;
    }

    /** Returns the concatenation of the two arrays. */
    public static Symbol[] concat(Symbol[] array1, Symbol[] array2) {
        if (array1.length == 0) return array2;
        if (array2.length == 0) return array1;
        Symbol[] clone = cloneArray(array1.length, array2);
        for (int i = 0; i < array1.length; i++) clone[i] = array1[i];
        return clone;
    }

    /** copy all fields to `sym'
     */
    public void copyTo(Symbol sym) {
        sym.kind = kind;
        sym.pos = pos;
        sym.name = name;
        sym.flags = flags;
        sym.owner = owner;
        sym.infos = infos;
    }

// Setters ---------------------------------------------------------------

    /** Set the mangled name of this Symbol */
    public Symbol setMangledName(Name name) {
        throw new ApplicationError("illegal operation on " + getClass());
    }

    /** Set owner */
    public Symbol setOwner(Symbol owner) {
        assert !isModuleClass() : Debug.show(this);
        assert !isPrimaryConstructor() : Debug.show(this);
        setOwner(this, owner);
        return this;
    }
    private static void setOwner(Symbol symbol, Symbol owner) {
        assert symbol != null;
        assert symbol != Symbol.NONE;
        assert symbol != Symbol.ERROR;
        if (symbol.isModule()) setOwner(symbol.moduleClass(), owner);
        if (symbol.isClass()) {
            Symbol[] alts = symbol.allConstructors().alternativeSymbols();
            for (int i = 0; i < alts.length; i++) setOwner(alts[i], owner);
        }
        symbol.owner = owner;
    }

    /** Set type -- this is an alias for setInfo(Type info) */
    public final Symbol setType(Type info) { return setInfo(info); }

    /**
     * Set initial information valid from start of current phase. This
     * information is visible in the current phase and will be
     * transformed by the current phase (except if current phase is
     * the first one).
     */
    public Symbol setInfo(Type info) {
        return setInfoAt(info, Global.instance.currentPhase);
    }

    /**
     * Set initial information valid from start of first phase. This
     * information is visible in the first phase and will be
     * transformed by all phases excepted the first one.
     */
    public final Symbol setFirstInfo(Type info) {
        return setInfoAt(info, Global.instance.getFirstPhase());
    }

    /**
     * Set initial information valid from start of given phase. This
     * information is visible in the given phase and will be
     * transformed by the given phase (except if it is the first
     * phase).
     */
    private final Symbol setInfoAt(Type info, Phase phase) {
        assert phase != null : this;
        assert !isConstructor()
            || info instanceof Type.LazyType
            || info == Type.NoType
            || info == Type.ErrorType
            || info instanceof Type.MethodType
            || info instanceof Type.OverloadedType
            || info instanceof Type.PolyType
            : "illegal type for " + this + ": " + info;
        if (phase.prev != null) phase = phase.prev;
        infos = new TypeIntervalList(null, info, phase);
        if (info instanceof Type.LazyType) flags &= ~INITIALIZED;
        else flags |= INITIALIZED;
        return this;
    }

    /**
     * Set new information valid from start of next phase. This
     * information is only visible in next phase or through
     * "nextInfo". It will not be transformed by the current phase.
     */
    public final Symbol updateInfo(Type info) {
        return updateInfoAt(info, Global.instance.currentPhase);
    }

    /**
     * Set new information valid from start of phase after given
     * phase. This information is only visible from the start of the
     * phase after the given phase. It will not be tranformed by the
     * given phase.
     */
    private final Symbol updateInfoAt(Type info, Phase phase) {
        assert infos != null : this;
        assert !phase.precedes(infos.limit()) :
            this + " -- " + phase + " -- " + infos.limit();
        if (infos.limit() == phase) {
            if (infos.start == phase)
                infos = infos.prev;
            else
                infos.setLimit(infos.limit().prev);
        }
        infos = new TypeIntervalList(infos, info, phase);
        return this;
    }

    /** Set type of `this' in current class
     */
    public Symbol setTypeOfThis(Type tp) {
        throw new ApplicationError(this + ".setTypeOfThis");
    }

    /** Set the low bound of this type variable
     */
    public Symbol setLoBound(Type lobound) {
        throw new ApplicationError("setLoBound inapplicable for " + this);
    }

    /** Add an auxiliary constructor to class; return created symbol.
     */
    public Symbol addConstructor() {
        throw new ApplicationError("addConstructor inapplicable for " + this);
    }

// Symbol classification ----------------------------------------------------

    /** Does this symbol denote a type? */
    public final boolean isType() {
        return kind == TYPE || kind == CLASS || kind == ALIAS;
    }

    /** Does this symbol denote a term? */
    public final boolean isTerm() {
        return kind == VAL;
    }

    /** Does this symbol denote a value? */
    public final boolean isValue() {
        preInitialize();
        return kind == VAL && !(isModule() && isJava()) && !isPackage();
    }

    /** Does this symbol denote a stable value? */
    public final boolean isStable() {
        return kind == VAL &&
            ((flags & STABLE) != 0 ||
             (flags & MUTABLE) == 0 && type().isObjectType());
    }

    /** Does this symbol denote a variable? */
    public final boolean isVariable() {
        return kind == VAL && (flags & MUTABLE) != 0;
    }

    /**
     * Does this symbol denote a final method? A final method is one
     * that can't be overridden in a subclass. This method assumes
     * that this symbol denotes a method. It doesn't test it.
     */
    public final boolean isMethodFinal() {
        return (flags & FINAL) != 0 || isPrivate() || isLifted();
    }

    /** Does this symbol denote a sealed class symbol? */
    public final boolean isSealed() {
        return (flags & SEALED) != 0;
    }

    /** Does this symbol denote a method?
     */
    public final boolean isInitializedMethod() {
        if (infos == null) return false;
        switch (rawInfo()) {
        case MethodType(_, _):
        case PolyType(_, _):
            return true;
        case OverloadedType(Symbol[] alts, _):
            for (int i = 0; i < alts.length; i++)
                if (alts[i].isMethod()) return true;
            return false;
        default:
            return false;
        }
    }

    public final boolean isMethod() {
        initialize();
        return isInitializedMethod();
    }

    public final boolean isCaseFactory() {
        return isMethod() && !isConstructor() && (flags & CASE) != 0;
    }

    public final boolean isAbstractClass() {
        preInitialize();
        return kind == CLASS && (flags & ABSTRACT) != 0 &&
            this != Global.instance.definitions.ARRAY_CLASS;
    }

    public final boolean isAbstractOverride() {
        preInitialize();
        return (flags & (ABSTRACT | OVERRIDE)) == (ABSTRACT | OVERRIDE);
    }

    /* Does this symbol denote an anonymous class? */
    public final boolean isAnonymousClass() {
        return isClass() && name.startsWith(Names.ANON_CLASS_NAME);
    }

    /** Does this symbol denote the root class or root module?
     */
    public final boolean isRoot() {
        return this.moduleClass() == Global.instance.definitions.ROOT_CLASS;
    }

    /** Does this symbol denote something loaded from a Java class? */
    public final boolean isJava() {
        preInitialize();
        return (flags & JAVA) != 0;
    }

    /** Does this symbol denote a Java package? */
    public final boolean isPackage() {
        return (flags & PACKAGE) != 0;
    }

    /** Does this symbol denote a module? */
    public final boolean isModule() {
        return kind == VAL && (flags & MODUL) != 0;
    }

    /** Does this symbol denote a global module? */
    public final  boolean isGlobalModule() {
        return isModule() && (owner().isPackage()
            //|| owner().isGlobalModule() // add later? translation does not work (yet?)
        );
    }

    /** Does this symbol denote a module? */
    public final boolean isModuleClass() {
        return kind == CLASS && (flags & MODUL) != 0;
    }

    /** Does this symbol denote a class? */
    public final boolean isClass() {
        return kind == CLASS && (flags & PACKAGE) == 0;
    }

    /** Does this symbol denote a case class?
     */
    public final boolean isCaseClass() {
        preInitialize();
        return kind == CLASS && (flags & CASE) != 0;
    }

    /** Does this symbol denote a uniform (i.e. parameterless) class? */
    public final boolean isTrait() {
        //preInitialize(); todo: enable, problem is that then we cannot print
        // during unpickle
        return kind == CLASS && (flags & TRAIT) != 0;
    }

    /** Does this class symbol denote a compound type symbol?
     */
    public final boolean isCompoundSym() {
        return name == Names.COMPOUND_NAME.toTypeName();
    }

    /** Does this symbol denote an interface? */
    public final boolean isInterface() {
        preInitialize();
        return (flags & INTERFACE) != 0;
    }

    /** Does this symbol denote a type alias? */
    public final boolean isTypeAlias() {
        return kind == ALIAS;
    }

    /** Does this symbol denote an abstract type? */
    public final boolean isAbstractType() {
        return kind == TYPE;
    }

    /** Does this symbol denote a class type? */
    public final boolean isClassType() {
        return kind == CLASS;
    }

    /** Does this symbol denote a public symbol? */
    public final boolean isPublic() {
        return !isProtected() && !isPrivate();
    }

    /** Does this symbol denote a protected symbol? */
    public final boolean isProtected() {
        preInitialize();
        return (flags & PROTECTED) != 0;
    }

    /** Does this symbol denote a private symbol? */
    public final boolean isPrivate() {
        preInitialize();
        return (flags & PRIVATE) != 0;
    }

    /** Has this symbol been lifted? */
    public final boolean isLifted() {
        preInitialize();
        return (flags & LIFTED) != 0;
    }

    /** Does this symbol denote a deferred symbol? */
    public final boolean isDeferred() {
        return (flags & DEFERRED) != 0;
    }

    /** Does this symbol denote a synthetic symbol? */
    public final boolean isSynthetic() {
        return (flags & SYNTHETIC) != 0;
    }

    /** Does this symbol denote a static member? */
    public final boolean isStatic() {
        return (flags & STATIC) != 0;
    }

    /** Does this symbol denote an accessor? */
    public final boolean isAccessor() {
        return (flags & ACCESSOR) != 0;
    }

    /** Is this symbol locally defined? I.e. not a member of a class or module */
    public final boolean isLocal() {
        return owner.kind == VAL &&
            !((flags & PARAM) != 0 && owner.isPrimaryConstructor());
    }

    /** Is this symbol a parameter? Includes type parameters of methods.
     */
    public final boolean isParameter() {
        return (flags & PARAM) != 0;
    }

    /** Is this symbol a def parameter?
     */
    public final boolean isDefParameter() {
        return (flags & (PARAM | DEF)) == (PARAM | DEF);
    }

    /** Is this class locally defined?
     *  A class is local, if
     *   - it is anonymous, or
     *   - its owner is a value
     *   - it is defined within a local class
     */
    public final boolean isLocalClass() {
        return isClass() &&
            (isAnonymousClass() ||
             owner.isValue() ||
             owner.isLocalClass());
    }

    /** Is this symbol an instance initializer? */
    public boolean isInitializer() {
        return false;
    }

    /** Is this symbol a constructor? */
    public boolean isConstructor() {
        return false;
    }

    /** Is this symbol the primary constructor of a type? */
    public final boolean isPrimaryConstructor() {
        return isConstructor() && this == constructorClass().primaryConstructor();
    }

    public final boolean isGenerated() {
        return name.pos((byte)'$') < name.length();
    }

    /** Symbol was preloaded from package
     */
    public final boolean isExternal() {
        return pos == Position.NOPOS;
    }

    /** Is this symbol an overloaded symbol? */
    public final boolean isOverloaded() {
        switch (info()) {
        case OverloadedType(_,_): return true;
        default                 : return false;
        }
    }

    /** Does this symbol denote a label? */
    public final boolean isLabel() {
        return (flags & LABEL) != 0;
    }

    /** The variance of this symbol as an integer
     */
    public int variance() {
        if ((flags & COVARIANT) != 0) return 1;
        else if ((flags & CONTRAVARIANT) != 0) return -1;
        else return 0;
    }

// Symbol names ----------------------------------------------------------------

    /** Get the fully qualified name of this Symbol
     *  (this is always a normal name, never a type name)
     */

    /** Get the simple name of this Symbol (this is always a term name)
     */
    public Name simpleName() {
        return isConstructor() ? constructorClass().name.toTermName()
            : name.toTermName();
    }

    /** Get the fully qualified name of this Symbol */
    public Name fullName() {
        return simpleName();
    }

    /** Get the mangled name of this Symbol
     *  (this is always a normal name, never a type name)
     */
    public Name mangledName() {
        return isConstructor() ? constructorClass().name.toTermName() : name.toTermName();
    }

    /** Get the fully qualified mangled name of this Symbol */
    public Name mangledFullName() {
        return fullName().replace((byte)'.', (byte)'$');
    }

// Acess to related symbols -----------------------------------------------------

    /** Get type parameters */
    public Symbol[] typeParams() {
        return EMPTY_ARRAY;
    }

    /** Get value parameters */
    public Symbol[] valueParams() {
        return EMPTY_ARRAY;
    }

    /** Get type parameters at start of next phase */
    public final Symbol[] nextTypeParams() {
        Global.instance.nextPhase();
        Symbol[] tparams = typeParams();
        Global.instance.prevPhase();
        return tparams;
    }

    /** Get value parameters at start of next phase */
    public final Symbol[] nextValueParams() {
        Global.instance.nextPhase();
        Symbol[] vparams = valueParams();
        Global.instance.prevPhase();
        return vparams;
    }

    /** Get all constructors of class */
    public Symbol allConstructors() {
        return NONE;
    }

    /** Get primary constructor of class */
    public Symbol primaryConstructor() {
        return NONE;
    }

    /** Get module associated with class */
    public Symbol module() {
        return NONE;
    }

    /** Get owner */
    public Symbol owner() {
        return owner;
    }

    /** Get owner, but if owner is primary constructor of a class,
     *  get class symbol instead. This is useful for type parameters
     *  and value parameters in classes which have the primary constructor
     *  as owner.
     */
    public Symbol classOwner() {
        Symbol owner = owner();
        Symbol clazz = owner.constructorClass();
        if (clazz.primaryConstructor() == owner) return clazz;
        else return owner;
    }

    /** The next enclosing class */
    public Symbol enclClass() {
        return owner().enclClass();
    }

    /** The next enclosing method */
    public Symbol enclMethod() {
        return isMethod() ? this : owner().enclMethod();
    }

    /** The top-level class enclosing `sym'
     */
    Symbol enclToplevelClass() {
        Symbol sym = this;
        while (sym.kind == VAL ||
               (sym.kind == CLASS && !sym.owner().isPackage())) {
            sym = sym.owner();
        }
        return sym;
    }

    /** If this is a constructor, return the class it constructs.
     *  Otherwise return the symbol itself.
     */
    public Symbol constructorClass() {
        return this;
    }

    /** Return first alternative if this has a (possibly lazy)
     *  overloaded type, otherwise symbol itself.
     *  Needed in ClassSymbol.primaryConstructor() and in UnPickle.
     */
    public Symbol firstAlternative() {
        if (infos == null)
            return this;
        else if (infos.info instanceof Type.OverloadedType)
            return infos.info.alternativeSymbols()[0];
        else if (infos.info instanceof LazyOverloadedType)
            return ((LazyOverloadedType) infos.info).sym1.firstAlternative();
        else
            return this;
    }

     /* If this is a module, return its class.
     *  Otherwise return the symbol itself.
     */
    public Symbol moduleClass() {
        return this;
    }

    /** if type is a (possibly lazy) overloaded type, return its alternatves
     *  else return array consisting of symbol itself
     */
    public Symbol[] alternativeSymbols() {
        Symbol[] alts = type().alternativeSymbols();
        if (alts.length == 0) return new Symbol[]{this};
        else return alts;
    }

    /** if type is a (possibly lazy) overloaded type, return its alternatves
     *  else return array consisting of type itself
     */
    public Type[] alternativeTypes() {
        return type().alternativeTypes();
    }

    /** The symbol accessed by this accessor function.
     */
    public Symbol accessed() {
        assert (flags & ACCESSOR) != 0;
        Name name1 = name;
        if (name1.endsWith(Names._EQ))
            name1 = name1.subName(0, name1.length() - Names._EQ.length());
        return owner.info().lookup(Name.fromString(name1 + "$"));
    }

    /** The members of this class or module symbol
     */
    public Scope members() {
        return info().members();
    }

    /** Lookup symbol with given name; return Symbol.NONE if not found.
     */
    public Symbol lookup(Name name) {
        return info().lookup(name);
    }

// Symbol types --------------------------------------------------------------

    /** Was symbol's type updated during given phase? */
    public final boolean isUpdatedAt(Phase phase) {
        TypeIntervalList infos = this.infos;
        while (infos != null) {
            if (infos.start == phase) return true;
            if (infos.limit().precedes(phase)) return false;
            infos = infos.prev;
        }
        return false;
    }

    /** Is this symbol initialized? */
    public final boolean isInitialized() {
        return (flags & INITIALIZED) != 0;
    }

    /** Initialize the symbol */
    public final Symbol initialize() {
        info();
        return this;
    }

    /** Make sure symbol is entered
     */
    public final void preInitialize() {
        //todo: clean up
        if (infos.info instanceof ClassParser ||
            infos.info instanceof SourceCompleter ||
            infos.info instanceof ClassParser.StaticsParser)
            infos.info.complete(this);
    }

    /** Get info at start of current phase; This is:
     *  for a term symbol, its type
     *  for a type variable, its bound
     *  for a type alias, its right-hand side
     *  for a class symbol, the compound type consisting of
     *  its baseclasses and members.
     */
    public final Type info() {
        //if (isModule()) moduleClass().initialize();
        Phase phase = Global.instance.currentPhase;
        if ((flags & INITIALIZED) == 0) {
            Type info = rawFirstInfo();
            assert info != null : this;
            if ((flags & LOCKED) != 0) {
                setInfo(Type.ErrorType);
                flags |= INITIALIZED;
                throw new CyclicReference(this, info);
            }
            flags |= LOCKED;
            //System.out.println("completing " + this);//DEBUG
            info.complete(this);
            flags = flags & ~LOCKED;
            if (info instanceof SourceCompleter && (flags & SNDTIME) == 0) {
                flags |= SNDTIME;
                Type tp = info();
                flags &= ~SNDTIME;
            } else {
                assert !(rawInfoAt(phase) instanceof Type.LazyType) : this;
                //flags |= INITIALIZED;
            }
            //System.out.println("done: " + this);//DEBUG
        }
        return rawInfoAt(phase);
    }

    /** Get info at start of next phase
     */
    public final Type nextInfo() {
        Global.instance.nextPhase();
        Type info = info();
        Global.instance.prevPhase();
        return info;
    }

    /** Get info at start of given phase
     */
    protected final Type infoAt(Phase phase) {
        Global global = phase.global;
        Phase current = global.currentPhase;
        global.currentPhase = phase;
        Type info = info();
        global.currentPhase = current;
        return info;
    }

    /** Get info at start of current phase, without forcing lazy types.
     */
    public final Type rawInfo() {
        return rawInfoAt(Global.instance.currentPhase);
    }

    /** Get info at start of next phase, without forcing lazy types.
     */
    public final Type rawNextInfo() {
        Global.instance.nextPhase();
        Type info = rawInfo();
        Global.instance.prevPhase();
        return info;
    }

    /** Get info at start of given phase, without forcing lazy types.
     */
    private final Type rawInfoAt(Phase phase) {
        //if (infos == null) return Type.NoType;//DEBUG
        assert infos != null : this;
        assert phase != null : this;
        if (infos.limit().precedes(phase)) {
            while (infos.limit().next != phase) {
                Phase next = infos.limit().next;
                Type info = transformInfo(next, infos.info);
                if (info != infos.info) {
                    infos = new TypeIntervalList(infos, info, next);
                } else {
                    infos.setLimit(next);
                }
            }
            return infos.info;
        } else {
            TypeIntervalList infos = this.infos;
            while (!infos.start.precedes(phase) && infos.prev != null)
                infos = infos.prev;
            return infos.info;
        }
    }
    // where
        private Type transformInfo(Phase phase, Type info) {
            Global global = phase.global;
            Phase current = global.currentPhase;
            switch (info) {
            case ErrorType:
            case NoType:
                return info;
            case OverloadedType(Symbol[] alts, Type[] alttypes):
                global.currentPhase = phase.next;
                for (int i = 0; i < alts.length; i++) {
                    Type type = alts[i].info();
                    if (type != alttypes[i]) {
                        Type[] types = new Type[alttypes.length];
                        for (int j = 0; j < i; j++) types[j] = alttypes[j];
                        alttypes[i] = type;
                        for (; i < alts.length; i++)
                            types[i] = alts[i].info();
                        global.currentPhase = current;
                        return Type.OverloadedType(alts, types);
                    }
                }
                global.currentPhase = current;
                return info;
            default:
                global.currentPhase = phase;
                info = phase.transformInfo(this, info);
                global.currentPhase = current;
                return info;
            }
        }

    /** Get first defined info, without forcing lazy types.
     */
    public final Type rawFirstInfo() {
        TypeIntervalList infos = this.infos;
        assert infos != null : this;
        while (infos.prev != null) infos = infos.prev;
        return infos.info;
    }

    /** Get phase that first defined an info, without forcing lazy types.
     */
    public final Phase rawFirstInfoStartPhase() {
        TypeIntervalList infos = this.infos;
        assert infos != null : this;
        while (infos.prev != null) infos = infos.prev;
        Phase phase = infos.start;
        return phase.prev != null && phase.next != null ? phase.next : phase;
    }

    /** Get type at start of current phase. The type of a symbol is:
     *  for a type symbol, the type corresponding to the symbol itself
     *  for a term symbol, its usual type
     */
    public Type type() {
        return info();
    }

    /** Get type at start of next phase
     */
    public final Type nextType() {
        Global.instance.nextPhase();
        Type type = type();
        Global.instance.prevPhase();
        return type;
    }

    /** The types of these symbols as an array.
     */
    static public Type[] type(Symbol[] syms) {
        Type[] tps = new Type[syms.length];
        for (int i = 0; i < syms.length; i++)
            tps[i] = syms[i].type();
        return tps;
    }

    /** The type constructor of a symbol is:
     *  For a type symbol, the type corresponding to the symbol itself, excluding
     *  parameters.
     *  Not applicable for term symbols.
     */
    public Type typeConstructor() {
        throw new ApplicationError("typeConstructor inapplicable for " + this);
    }

    /** The low bound of this type variable
     */
    public Type loBound() {
        return Global.instance.definitions.ALL_TYPE();
    }

    /** Get this.type corresponding to this symbol
     */
    public Type thisType() {
        return Type.localThisType;
    }

    /** Get type of `this' in current class.
     */
    public Type typeOfThis() {
        return type();
    }

    /** Get this symbol of current class
     */
    public Symbol thisSym() { return this; }


    /** A total ordering between symbols that refines the class
     *  inheritance graph (i.e. subclass.isLess(superclass) always holds).
     */
    public boolean isLess(Symbol that) {
        if (this == that) return false;
        int diff;
        if (this.isType()) {
            if (that.isType()) {
                diff = this.closure().length - that.closure().length;
                if (diff > 0) return true;
                if (diff < 0) return false;
            } else {
                return true;
            }
        } else if (that.isType()) {
            return false;
        }

        diff = that.mangledName().index - this.mangledName().index;
        if (diff > 0) return true;
        if (diff < 0) return false;

        diff = that.mangledFullName().index - this.mangledFullName().index;
        if (diff > 0) return true;
        if (diff < 0) return false;

        diff = that.hashCode() - this.hashCode();
        if (diff > 0) return true;
        if (diff < 0) return false;

        if (owner().isLess(that.owner())) return true;
        if (that.owner().isLess(owner())) return false;

        throw new ApplicationError(
            "Giving up: can't order two incarnations of class " +
            this.mangledFullName());
    }

    /** Return the symbol's type itself followed by all its direct and indirect
     *  base types, sorted by isLess(). Overridden for class symbols.
     */
    public Type[] closure() {
        return info().closure();
    }

    /** Return position of `c' in the closure of this type; -1 if not there.
     */
    public int closurePos(Symbol c) {
        if (this == c) return 0;
        if (c.isCompoundSym()) return -1;
        Type[] closure = closure();
        int lo = 0;
        int hi = closure.length - 1;
        while (lo <= hi) {
            int mid = (lo + hi) / 2;
            Symbol clsym = closure[mid].symbol();
            if (c == clsym) return mid;
            else if (c.isLess(clsym)) hi = mid - 1;
            else if (clsym.isLess(c)) lo = mid + 1;
            else throw new ApplicationError();
        }
        return -1;
    }

    public Type baseType(Symbol sym) {
        int i = closurePos(sym);
        if (i >= 0) return closure()[i];
        else return Type.NoType;
    }

    /** Is this class a subclass of `c'? I.e. does it have a type instance
     *  of `c' as indirect base class?
     */
    public boolean isSubClass(Symbol c) {
        return this == c ||
            c.kind == Kinds.ERROR ||
            closurePos(c) >= 0 ||
            this == Global.instance.definitions.ALL_CLASS ||
            (this == Global.instance.definitions.ALLREF_CLASS &&
             c != Global.instance.definitions.ALL_CLASS &&
             c.isSubClass(Global.instance.definitions.ANYREF_CLASS));
    }

    /** Get base types of this symbol */
    public Type[] parents() {
        return info().parents();
    }

// ToString -------------------------------------------------------------------

    /** String representation of symbol's simple name.
     *  Translates expansions of operators back to operator symbol. E.g.
     *  $eq => =.
     */
    public String nameString() {
        return NameTransformer.decode(simpleName()).toString();
    }

    /** String representation of symbol's full name.
     *  Translates expansions of operators back to operator symbol. E.g.
     *  $eq => =.
     */
    public String fullNameString() {
        return NameTransformer.decode(fullName()).toString();
    }

    /** String representation, including symbol's kind
     *  e.g., "class Foo", "function Bar".
     */
    public String toString() {
        return new SymbolTablePrinter().printSymbol(this).toString();
    }

    /** String representation of location.
     */
    public String locationString() {
        if (owner.kind == CLASS &&
            !owner.isAnonymousClass() && !owner.isCompoundSym() ||
            Global.instance.debug)
            return " in " + owner;
        else
            return "";
    }

    /** String representation of definition.
     */
    public String defString() {
        return new SymbolTablePrinter().printSignature(this).toString();
    }

    public static String[] defString(Symbol[] defs) {
        String[] strs = new String[defs.length];
        for (int i = 0; i < defs.length; i++)
            strs[i] = defs[i].defString();
        return strs;
    }

// Overloading and Overriding -------------------------------------------

    /** Add another overloaded alternative to this symbol.
     */
    public Symbol overloadWith(Symbol that) {
        assert isTerm() : Debug.show(this);
        assert this.name == that.name : Debug.show(this) + " <> " + Debug.show(that);
        assert this.owner == that.owner : Debug.show(this) + " != " + Debug.show(that);
        assert this.isConstructor() == that.isConstructor();
        int overflags = (this.flags & that.flags & (JAVA | ACCESSFLAGS)) |
            ((this.flags | that.flags) & ACCESSOR);
        TermSymbol overloaded = (this.isConstructor())
            ? TermSymbol.newConstructor(this.constructorClass(), overflags)
            : new TermSymbol(pos, name, owner, overflags);
        overloaded.setInfo(new LazyOverloadedType(this, that));
        return overloaded;
    }

    /** A lazy type which, when forced computed the overloaded type
     *  of symbols `sym1' and `sym2'. It also checks that this type is well-formed.
     */
    public static class LazyOverloadedType extends Type.LazyType {
        Symbol sym1;
        Symbol sym2;
        LazyOverloadedType(Symbol sym1, Symbol sym2) {
            this.sym1 = sym1;
            this.sym2 = sym2;
        }

        public Symbol[] alternativeSymbols() {
            Symbol[] alts1 = sym1.alternativeSymbols();
            Symbol[] alts2 = sym2.alternativeSymbols();
            Symbol[] alts3 = new Symbol[alts1.length + alts2.length];
            System.arraycopy(alts1, 0, alts3, 0, alts1.length);
            System.arraycopy(alts2, 0, alts3, alts1.length, alts2.length);
            return alts3;
        }

        public Type[] alternativeTypes() {
            Type[] alts1 = sym1.alternativeTypes();
            Type[] alts2 = sym2.alternativeTypes();
            Type[] alts3 = new Type[alts1.length + alts2.length];
            System.arraycopy(alts1, 0, alts3, 0, alts1.length);
            System.arraycopy(alts2, 0, alts3, alts1.length, alts2.length);
            return alts3;
        }

        public void complete(Symbol overloaded) {
            overloaded.setInfo(
                Type.OverloadedType(
                    alternativeSymbols(), alternativeTypes()));
        }

        public String toString() {
            return "LazyOverloadedType(" + sym1 + "," + sym2 + ")";
        }
    }

    /**
     * Returns the symbol in type "base" which is overridden by this
     * symbol in class "this.owner()". Returns "NONE" if no such
     * symbol exists. The type "base" must be a supertype of class
     * "this.owner()". If "exact" is true, overriding is restricted to
     * symbols that have the same type. The method may return this
     * symbol only if "base.symbol()" is equal to "this.owner()".
     */
    public final Symbol overriddenSymbol(Type base, boolean exact) {
        return overriddenSymbol(base, owner(), exact);
    }
    public final Symbol overriddenSymbol(Type base) {
        return overriddenSymbol(base, false);
    }

    /**
     * Returns the symbol in type "base" which is overridden by this
     * symbol in "clasz". Returns "NONE" if no such symbol exists. The
     * type "base" must be a supertype of "clasz" and "this.owner()"
     * must be a superclass of "clasz". If "exact" is true, overriding
     * is restricted to symbols that have the same type.  The method
     * may return this symbol if "base.symbol()" is a subclass of
     * "this.owner()".
     */
    public final Symbol overriddenSymbol(Type base, Symbol clasz, boolean exact) {
        Type.Relation relation = exact
            ? Type.Relation.SameType
            : Type.Relation.SuperType;
        return base.lookup(this, clasz.thisType(), relation);
    }
    public final Symbol overriddenSymbol(Type base, Symbol clasz) {
        return overriddenSymbol(base, clasz, false);
    }

    /**
     * Returns the symbol in type "sub" which overrides this symbol in
     * class "sub.symbol()". Returns this symbol if no such symbol
     * exists. The class "sub.symbol()" must be a subclass of
     * "this.owner()". If "exact" is true, overriding is restricted to
     * symbols that have the same type.
     */
    public final Symbol overridingSymbol(Type sub, boolean exact) {
        Type.Relation relation = exact
            ? Type.Relation.SameType
            : Type.Relation.SubType;
        return sub.lookup(this, sub, relation);
    }
    public final Symbol overridingSymbol(Type sub) {
        return overridingSymbol(sub, false);
    }

    /** Does this symbol override that symbol?
     */
    public boolean overrides(Symbol that) {
        return
            ((this.flags | that.flags) & (PRIVATE | STATIC)) == 0 &&
            this.name == that.name &&
            owner.thisType().memberType(this).derefDef().isSubType(
                owner.thisType().memberType(that).derefDef());
    }

    /** Reset symbol to initial state
     */
    public void reset(Type completer) {
        this.flags &= SOURCEFLAGS;
        this.pos = 0;
        this.infos = null;
        this.setInfo(completer);
    }

    /** return a tag which (in the ideal case) uniquely identifies
     *  class symbols
     */
        public int tag() {
                return name.toString().hashCode();
        }
}

/** A class for term symbols
 */
public class TermSymbol extends Symbol {

    private Symbol clazz;

    /** Constructor */
    public TermSymbol(int pos, Name name, Symbol owner, int flags) {
        super(VAL, pos, name, owner, flags);
        assert !name.isTypeName() : this;
    }

    public static TermSymbol define(
        int pos, Name name, Symbol owner, int flags, Scope scope) {
        Scope.Entry e = scope.lookupEntry(name);
        if (e.owner == scope && e.sym.isExternal() && e.sym.kind == VAL) {
            TermSymbol sym = (TermSymbol) e.sym;
            sym.update(pos, flags);
            return sym;
        } else {
            return new TermSymbol(pos, name, owner, flags);
        }
    }

    public static TermSymbol newConstructor(Symbol clazz, int flags) {
        TermSymbol sym = new TermSymbol(
            clazz.pos, Names.CONSTRUCTOR, clazz.owner(), flags);
        sym.clazz = clazz;
        return sym;
    }

    public static TermSymbol newJavaConstructor(Symbol clazz) {
        return newConstructor(clazz, clazz.flags & (ACCESSFLAGS | JAVA));
    }

    public TermSymbol makeModule(ClassSymbol clazz) {
        flags |= MODUL | FINAL;
        this.clazz = clazz;
        clazz.setModule(this);
        setInfo(clazz.typeConstructor());
        return this;
    }

    public TermSymbol makeModule() {
        ClassSymbol clazz = new ClassSymbol(
            pos, name.toTypeName(), owner(), flags | MODUL | FINAL);
        clazz.primaryConstructor().setInfo(
            Type.MethodType(Symbol.EMPTY_ARRAY, clazz.typeConstructor()));
        return makeModule(clazz);
    }

    /** Constructor for companion modules to classes, which need to be completed.
     */
    public static TermSymbol newCompanionModule(Symbol clazz, int flags, Type.LazyType parser) {
        TermSymbol sym = new TermSymbol(
            Position.NOPOS, clazz.name.toTermName(), clazz.owner(), flags | STABLE)
            .makeModule();
        sym.clazz.setInfo(parser);
        return sym;
    }

    /** Java package module constructor
     */
    public static TermSymbol newJavaPackageModule(Name name, Symbol owner, Type.LazyType parser) {
        TermSymbol sym = new TermSymbol(Position.NOPOS, name, owner, JAVA | PACKAGE)
            .makeModule();
        sym.clazz.flags |= SYNTHETIC;
        sym.clazz.setInfo(parser != null ? parser : Type.compoundType(Type.EMPTY_ARRAY, new Scope(), sym));
        return sym;
    }

    /** Dummy symbol for template of given class
     */
    public static Symbol newLocalDummy(Symbol clazz) {
        return new TermSymbol(clazz.pos, Names.LOCAL(clazz), clazz, 0)
            .setInfo(Type.NoType);
    }

    /** Get this.type corresponding to this class or module
     */
    public Type thisType() {
        if ((flags & MODUL) != 0) return moduleClass().thisType();
        else return Type.localThisType;
    }
    /** Get the fully qualified name of this Symbol */
    public Name fullName() {
        if (clazz != null) return clazz.fullName();
        else return super.fullName();
    }

    /** Is this symbol an instance initializer? */
    public boolean isInitializer() {
        return clazz == null && name == Names.CONSTRUCTOR;
    }

    /** Is this symbol a constructor? */
    public boolean isConstructor() {
        return clazz != null && name == Names.CONSTRUCTOR;
    }

    /** Return a fresh symbol with the same fields as this one.
     */
    public Symbol cloneSymbol(Symbol owner) {
        assert !isPrimaryConstructor() : Debug.show(this);
        TermSymbol other;
        if (isModule()) {
            other = new TermSymbol(pos, name, owner, flags).makeModule();
        } else {
            other = new TermSymbol(pos, name, owner, flags);
            other.clazz = clazz;
        }
        other.setInfo(info());
        return other;
    }

    public Symbol[] typeParams() {
        return type().typeParams();
    }

    public Symbol[] valueParams() {
        return type().valueParams();
    }

    public Symbol constructorClass() {
        return isConstructor() && clazz != null ? clazz : this;
    }

    public Symbol moduleClass() {
        return (flags & MODUL) != 0 ? clazz : this;
    }
}

/** A base class for all type symbols.
 *  It has AliasTypeSymbol, AbsTypeSymbol, ClassSymbol as subclasses.
 */
public abstract class TypeSymbol extends Symbol {

     /** A cache for closures
     */
    private ClosureIntervalList closures;

    /** The symbol's type template */
    private Type template = null;

    /** A cache for type constructors
     */
    private Type tycon = null;

    /** The primary constructor of this type */
    private Symbol constructor;

    /** Constructor */
    public TypeSymbol(int kind, int pos, Name name, Symbol owner, int flags) {
        super(kind, pos, name, owner, flags);
        assert name.isTypeName() : this;
        this.constructor = TermSymbol.newConstructor(this, flags & CONSTRFLAGS);
    }

    protected void update(int pos, int flags) {
        super.update(pos, flags);
        this.template = null;
    }

    /** copy all fields to `sym'
     */
    public void copyTo(Symbol sym) {
        super.copyTo(sym);
        Symbol symconstr = ((TypeSymbol) sym).constructor;
        constructor.copyTo(symconstr);
        if (constructor.isInitialized())
            symconstr.setInfo(fixConstrType(symconstr.type(), sym));
    }

    protected void copyConstructorInfo(TypeSymbol other) {
        other.primaryConstructor().setInfo(
            fixConstrType(
                primaryConstructor().info().cloneType(
                    primaryConstructor(), other.primaryConstructor()),
                other));
        Symbol[] alts = allConstructors().alternativeSymbols();
        for (int i = 1; i < alts.length; i++) {
            Symbol constr = other.addConstructor();
            constr.setInfo(
                fixConstrType(
                    alts[i].info().cloneType(alts[i], constr),
                    other));
        }
    }

    private Type fixConstrType(Type type, Symbol clone) {
        switch (type) {
        case MethodType(Symbol[] vparams, Type result):
            result = fixConstrType(result, clone);
            return new Type.MethodType(vparams, result);
        case PolyType(Symbol[] tparams, Type result):
            result = fixConstrType(result, clone);
            return new Type.PolyType(tparams, result);
        case TypeRef(Type pre, Symbol sym, Type[] args):
            assert sym == this : Debug.show(sym) + " != " + Debug.show(this);
            return new Type.TypeRef(pre, clone, args);
        case LazyType():
            return type;
        default:
            throw Debug.abort("unexpected constructor type:" + clone + ":" + type);
        }
    }

    /** add a constructor
     */
    public Symbol addConstructor() {
        Symbol constr = TermSymbol.newConstructor(this, flags & CONSTRFLAGS);
        constructor = constructor.overloadWith(constr);
        return constr;
    }

    /** Get primary constructor */
    public Symbol primaryConstructor() {
        return constructor.firstAlternative();
    }

    /** Get all constructors */
    public Symbol allConstructors() {
        return constructor;
    }

    /** Get type parameters */
    public Symbol[] typeParams() {
        return primaryConstructor().info().typeParams();
    }

    /** Get value parameters */
    public Symbol[] valueParams() {
        return (kind == CLASS) ? primaryConstructor().info().valueParams()
            : Symbol.EMPTY_ARRAY;
    }

    /** Get type constructor */
    public Type typeConstructor() {
        if (tycon == null)
            tycon = Type.TypeRef(owner().thisType(), this, Type.EMPTY_ARRAY);
        return tycon;
    }

    public Symbol setOwner(Symbol owner) {
        tycon = null;
        template = null;
        return super.setOwner(owner);
    }

    /** Get type */
    public Type type() {
        return primaryConstructor().type().resultType();
    }

    /**
     * Get closure at start of current phase. The closure of a symbol
     * is a list of types which contains the type of the symbol
     * followed by all its direct and indirect base types, sorted by
     * isLess().
     */
    public final Type[] closure() {
        if (kind == ALIAS) return info().symbol().closure();
        if (closures == null) computeClosureAt(rawFirstInfoStartPhase());
        Phase phase = Global.instance.currentPhase;
        if (closures.limit().precedes(phase)) {
            while (closures.limit().next != phase) {
                Phase limit = closures.limit().next;
                Type[] closure = closures.closure;
                for (int i = 0; i < closure.length; i++) {
                    Symbol symbol = closure[i].symbol();
                    if (symbol.infoAt(limit) != symbol.infoAt(limit.next)) {
                        computeClosureAt(limit.next);
                        break;
                    }
                }
                closures.setLimit(limit);
            }
            return closures.closure;
        } else {
            ClosureIntervalList closures = this.closures;
            while (!closures.start.precedes(phase) && closures.prev != null)
                closures = closures.prev;
            return closures.closure;
        }
    }

    /** Compute closure at start of given phase. */
    private final void computeClosureAt(Phase phase) {
        Phase current = Global.instance.currentPhase;
        Global.instance.currentPhase = phase;
        // todo: why can't we do: inclClosure(SymSet.EMPTY, this) ?
        //System.out.println("computing closure of " + this);//DEBUG
        Type[] parents = type().parents(); // evals info before use of LOCKED
        assert (flags & LOCKED) == 0 : Debug.show(this) + " -- " + phase;
        flags |= LOCKED;
        SymSet closureClassSet = inclClosure(SymSet.EMPTY, parents);
        flags &= ~LOCKED;
        Symbol[] closureClasses = new Symbol[closureClassSet.size() + 1];
        closureClasses[0] = this;
        closureClassSet.copyToArray(closureClasses, 1);
        //System.out.println(ArrayApply.toString(closureClasses));//DEBUG
        closures = new ClosureIntervalList(closures, Symbol.type(closureClasses), phase.prev == null ? phase : phase.prev);
        //System.out.println("closure(" + this + ") = " + ArrayApply.toString(closures.closure));//DEBUG



        adjustType(type());
        //System.out.println("closure(" + this + ") = " + ArrayApply.toString(closures.closure));//DEBUG
        Global.instance.currentPhase = current;

    }
    //where
        private static SymSet inclClosure(SymSet set, Type[] tps) {
            for (int i = 0; i < tps.length; i++) set = inclClosure(set,tps[i]);
            return set;
        }
        private static SymSet inclClosure(SymSet set, Type tp) {
            tp = tp.unalias();
            switch (tp) {
            case CompoundType(Type[] parents, _):
                return inclClosure(set, parents);
            default:
                return inclClosure(set, tp.symbol());
            }
        }
        private static SymSet inclClosure(SymSet set, Symbol sym) {
            while (sym.kind == ALIAS) sym = sym.info().symbol();
            return inclClosure(set.incl(sym), sym.type().parents());
        }

        private void adjustType(Type tp) {
            Type tp1 = tp.unalias();
            switch (tp) {
            case CompoundType(Type[] parents, _):
                break;
            default:
                Symbol sym = tp1.symbol();
                int pos = closurePos(sym);
                assert pos >= 0 : this + " " + tp1 + " " + tp1.symbol() + " " + pos;
                closures.closure[pos] = tp1;
            }
            Type[] parents = tp1.parents();
            for (int i = 0; i < parents.length; i++) {
                adjustType(parents[i]);
            }
        }

    public void reset(Type completer) {
        super.reset(completer);
        closures = null;
        tycon = null;
        template = null;
    }
}

public class AliasTypeSymbol extends TypeSymbol {

    /** Constructor */
    public AliasTypeSymbol(int pos, Name name, Symbol owner, int flags) {
        super(ALIAS, pos, name, owner, flags);
    }

    public static AliasTypeSymbol define(
        int pos, Name name, Symbol owner, int flags, Scope scope) {
        Scope.Entry e = scope.lookupEntry(name);
        if (e.owner == scope && e.sym.isExternal() && e.sym.kind == ALIAS) {
            AliasTypeSymbol sym = (AliasTypeSymbol) e.sym;
            sym.update(pos, flags);
            return sym;
        } else {
            return new AliasTypeSymbol(pos, name, owner, flags);
        }
    }

    /** Return a fresh symbol with the same fields as this one.
     */
    public Symbol cloneSymbol(Symbol owner) {
        AliasTypeSymbol other = new AliasTypeSymbol(pos, name, owner, flags);
        other.setInfo(info());
        copyConstructorInfo(other);
        return other;
    }
}

public class AbsTypeSymbol extends TypeSymbol {

    private Type lobound = null;

    /** Constructor */
    public AbsTypeSymbol(int pos, Name name, Symbol owner, int flags) {
        super(TYPE, pos, name, owner, flags);
        allConstructors().setFirstInfo(Type.MethodType(EMPTY_ARRAY, Type.TypeRef(owner.thisType(), this, Type.EMPTY_ARRAY)));
    }

    public static AbsTypeSymbol define(
        int pos, Name name, Symbol owner, int flags, Scope scope) {
        Scope.Entry e = scope.lookupEntry(name);
        if (e.owner == scope && e.sym.isExternal() && e.sym.kind == TYPE) {
            AbsTypeSymbol sym = (AbsTypeSymbol) e.sym;
            sym.update(pos, flags);
            return sym;
        } else {
            return new AbsTypeSymbol(pos, name, owner, flags);
        }
    }

    /** Return a fresh symbol with the same fields as this one.
     */
    public Symbol cloneSymbol(Symbol owner) {
        TypeSymbol other = new AbsTypeSymbol(pos, name, owner, flags);
        other.setInfo(info());
        other.setLoBound(loBound());
        return other;
    }

    /** copy all fields to `sym'
     */
    public void copyTo(Symbol sym) {
        super.copyTo(sym);
        ((AbsTypeSymbol) sym).lobound = lobound;
    }

    public Type loBound() {
        initialize();
        return lobound == null ? Global.instance.definitions.ALL_TYPE() : lobound;
    }

    public Symbol setLoBound(Type lobound) {
        this.lobound = lobound;
        return this;
    }
}

/** A class for class symbols. It has JavaClassSymbol as a subclass.
 */
public class ClassSymbol extends TypeSymbol {

    /** The mangled class name */
    private Name mangled;

    /** The module belonging to the class. This means:
     *  For Java classes, its statics parts.
     *  For module classes, the corresponding module.
     *  For other classes, null.
     */
    private Symbol module = NONE;

    /** The given type of self, or NoType, if no explicit type was given.
     */
    private Symbol thisSym = this;

    public Symbol thisSym() { return thisSym; }

    /** A cache for this.thisType()
     */
    final private Type thistp = Type.ThisType(this);

    /** Principal Constructor
     */
    public ClassSymbol(int pos, Name name, Symbol owner, int flags) {
        super(CLASS, pos, name, owner, flags);
        this.mangled = name;
    }

    public static ClassSymbol define(
        int pos, Name name, Symbol owner, int flags, Scope scope) {
        Scope.Entry e = scope.lookupEntry(name);
        if (e.owner == scope && e.sym.isExternal() && e.sym.kind == CLASS) {
            ClassSymbol sym = (ClassSymbol) e.sym;
            sym.update(pos, flags);
            return sym;
        } else {
            return new ClassSymbol(pos, name, owner, flags);
        }
    }

    /** Constructor for classes to load as source files
     */
    public ClassSymbol(Name name, Symbol owner, SourceCompleter parser) {
        this(Position.NOPOS, name, owner, 0);
        this.module = TermSymbol.newCompanionModule(this, 0, parser);
        this.setInfo(parser);
    }

    /** Constructor for classes to load as class files.
     */
    public ClassSymbol(Name name, Symbol owner, ClassParser parser) {
        this(Position.NOPOS, name, owner, JAVA);
        this.module = TermSymbol.newCompanionModule(this, JAVA, parser.staticsParser(this));
        this.setInfo(parser);
    }

    /** Return a fresh symbol with the same fields as this one.
     */
    public Symbol cloneSymbol(Symbol owner) {
        ClassSymbol other = new ClassSymbol(pos, name, owner, flags);
        other.module = module;
        other.setInfo(info());
        copyConstructorInfo(other);
        other.mangled = mangled;
        if (thisSym != this) other.setTypeOfThis(typeOfThis());
        return other;
    }

    /** copy all fields to `sym'
     */
    public void copyTo(Symbol sym) {
        super.copyTo(sym);
        if (thisSym != this) sym.setTypeOfThis(typeOfThis());
    }

   /** Get module */
    public Symbol module() {
        return module;
    }

    /** Set module; only used internally from TermSymbol
     */
    void setModule(Symbol module) { this.module = module; }

    /** Set the mangled name of this Symbol */
    public Symbol setMangledName(Name name) {
        this.mangled = name;
        return this;
    }

    /** Get the fully qualified name of this Symbol */
    public Name fullName() {
        if (owner().kind == CLASS && !owner().isRoot())
            return Name.fromString(owner().fullName() + "." + name);
        else
            return name.toTermName();
    }

    /** Get the mangled name of this Symbol */
    public Name mangledName() {
        return mangled;
    }

    /** Get the fully qualified mangled name of this Symbol */
    public Name mangledFullName() {
        if (mangled == name) {
            return fullName().replace((byte)'.', (byte)'$');
        } else {
            Symbol tc = enclToplevelClass();
            if (tc != this) {
                return Name.fromString(
                    enclToplevelClass().mangledFullName() + "$" + mangled);
            } else {
                return mangled;
            }
        }
    }

    public Type thisType() {
        return thistp;
    }

    public Type typeOfThis() {
        return thisSym.type();
    }

    public Symbol setTypeOfThis(Type tp) {
        if (tp == Type.NoType) { thisSym = this; return this; }
        thisSym = new TermSymbol(this.pos, Names.this_, this, SYNTHETIC);
        thisSym.setInfo(tp);
        return this;
    }

    /** Return the next enclosing class */
    public Symbol enclClass() {
        return this;
    }

    public Symbol caseFieldAccessor(int index) {
        assert (flags & CASE) != 0 : this;
        Scope.SymbolIterator it = info().members().iterator();
        Symbol sym = null;
        if ((flags & JAVA) == 0) {
			for (int i = 0; i <= index; i++) {
				do {
					sym = it.next();
				} while (sym.kind != VAL || (sym.flags & CASEACCESSOR) == 0 || !sym.isMethod());
			}
			//System.out.println(this + ", case field[" + index + "] = " + sym);//DEBUG
		} else {
			sym = it.next();
			while ((sym.flags & SYNTHETIC) == 0) {
				System.out.println("skipping " + sym);
				sym = it.next();
			}
			for (int i = 0; i < index; i++)
				sym = it.next();
			System.out.println("field accessor = " + sym);
		}
		assert sym != null : this;
		return sym;
    }

    public void reset(Type completer) {
        super.reset(completer);
        module().reset(completer);
        thisSym = this;
    }
}

/** A class for error symbols.
 */
public final class ErrorSymbol extends Symbol {

    /** Constructor */
    public ErrorSymbol() {
        super(Kinds.ERROR, Position.NOPOS, Name.ERROR, null, INITIALIZED);
        super.setOwner(this);
        super.setInfo(Type.ErrorType);
    }

    public Symbol cloneSymbol(Symbol owner) {
        assert owner == this : Debug.show(owner);
        return this;
    }

    /** Set the mangled name of this Symbol */
    public Symbol mangled(Name name) {
        return this;
    }

    /** Set owner */
    public Symbol setOwner(Symbol owner) {
        assert owner == this : Debug.show(owner);
        return this;
    }

    /** Set type */
    public Symbol setInfo(Type info) {
        assert info == Type.ErrorType : info;
        return this;
    }

    /** Get primary constructor */
    public Symbol primaryConstructor() {
        return TermSymbol.newConstructor(this, 0).setInfo(Type.ErrorType);
    }

    /** Return the next enclosing class */
    public Symbol enclClass() {
        return this;
    }

    /** Return the next enclosing method */
    public Symbol enclMethod() {
        return this;
    }

    public Type loBound() {
        return Type.ErrorType;
    }

    public void reset(Type completer) {
    }
}

/** The class of Symbol.NONE
 */
public final class NoSymbol extends Symbol {

    /** Constructor */
    public NoSymbol() {
        super(Kinds.NONE, Position.NOPOS, Names.NOSYMBOL, null, INITIALIZED);
        super.setOwner(this);
        super.setInfo(Type.NoType);
    }

    /** Return a fresh symbol with the same fields as this one.
     */
    public Symbol cloneSymbol(Symbol owner) {
        assert owner == this : Debug.show(owner);
        return this;
    }

    /** Set the mangled name of this Symbol */
    public Symbol mangled(Name name) {
        throw new ApplicationError("illegal operation on " + getClass());
    }

    /** Set owner */
    public Symbol setOwner(Symbol owner) {
        assert owner == this : Debug.show(owner);
        return this;
    }

    /** Set type */
    public Symbol setInfo(Type info) {
        assert info == Type.NoType : info;
        return this;
    }

    /** Return the next enclosing class */
    public Symbol enclClass() {
        return this;
    }

    /** Return the next enclosing method */
    public Symbol enclMethod() {
        return this;
    }

    public Symbol owner() {
        throw new ApplicationError();
    }

    public void reset(Type completer) {
    }
}

/** A class for symbols generated in label definitions.
 */
public class LabelSymbol extends TermSymbol {

    /** give as argument the symbol of the function that triggered
        the creation of this label */
    public LabelSymbol(Symbol f) {
        super(f.pos, f.name, f, LABEL);
    }
}

/** An exception for signalling cyclic references.
 */
public class CyclicReference extends Type.Error {
    public Symbol sym;
    public Type info;
    public CyclicReference(Symbol sym, Type info) {
        super("illegal cyclic reference involving " + sym);
        this.sym = sym;
        this.info = info;
    }
}

/** A base class for values indexed by phases. */
abstract class IntervalList {

    // Content of start/limit can't be replaced by (start/limit).next
    // because during initialization (start/limit).next is not yet
    // known.

    /** Interval starts at start of phase "start.next" (inclusive) */
    public final Phase start;
    /** Interval ends at start of phase "limit.next" (inclusive) */
    private Phase limit;

    public IntervalList(IntervalList prev, Phase start) {
        this.start = start;
        this.limit = start;
        assert start != null && (prev == null || prev.limit.next == start) :
            Global.instance.currentPhase + " - " + prev + " - " + start;
    }

    public Phase limit() {
        return limit;
    }

    public void setLimit(Phase phase) {
        assert phase != null && !phase.precedes(start) : start + " - " + phase;
        limit = phase;
    }

    public String toString() {
        return "[" + start + "->" + limit + "]";
    }

}

/** A class for types indexed by phases. */
class TypeIntervalList extends IntervalList {

    /** Previous interval */
    public final TypeIntervalList prev;
    /** Info valid during this interval */
    public final Type info;

    public TypeIntervalList(TypeIntervalList prev, Type info, Phase start) {
        super(prev, start);
        this.prev = prev;
        this.info = info;
    }

}

/** A class for closures indexed by phases. */
class ClosureIntervalList extends IntervalList {

    /** Previous interval */
    public final ClosureIntervalList prev;
    /** Closure valid during this interval */
    public final Type[] closure;

    public ClosureIntervalList(ClosureIntervalList prev, Type[] closure, Phase start){
        super(prev, start);
        this.prev = prev;
        this.closure = closure;
    }

}