types.java

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                }
            }

            private Set<TypePair> cache = new HashSet<TypePair>();

            private boolean containsTypeRecursive(Type t, Type s) {
                TypePair pair = new TypePair(t, s);
                if (cache.add(pair)) {
                    try {
                        return containsType(t.getTypeArguments(),
                                            s.getTypeArguments());
                    } finally {
                        cache.remove(pair);
                    }
                } else {
                    return containsType(t.getTypeArguments(),
                                        rewriteSupers(s).getTypeArguments());
                }
            }

            private Type rewriteSupers(Type t) {
                if (!t.isParameterized())
                    return t;
                ListBuffer<Type> from = lb();
                ListBuffer<Type> to = lb();
                adaptSelf(t, from, to);
                if (from.isEmpty())
                    return t;
                ListBuffer<Type> rewrite = lb();
                boolean changed = false;
                for (Type orig : to.toList()) {
                    Type s = rewriteSupers(orig);
                    if (s.isSuperBound() && !s.isExtendsBound()) {
                        s = new WildcardType(syms.objectType,
                                             BoundKind.UNBOUND,
                                             syms.boundClass);
                        changed = true;
                    } else if (s != orig) {
                        s = new WildcardType(upperBound(s),
                                             BoundKind.EXTENDS,
                                             syms.boundClass);
                        changed = true;
                    }
                    rewrite.append(s);
                }
                if (changed)
                    return subst(t.tsym.type, from.toList(), rewrite.toList());
                else
                    return t;
            }

            @Override
            public Boolean visitClassType(ClassType t, Type s) {
                Type sup = asSuper(t, s.tsym);
                return sup != null
                    && sup.tsym == s.tsym
                    // You're not allowed to write
                    //     Vector<Object> vec = new Vector<String>();
                    // But with wildcards you can write
                    //     Vector<? extends Object> vec = new Vector<String>();
                    // which means that subtype checking must be done
                    // here instead of same-type checking (via containsType).
                    && (!s.isParameterized() || containsTypeRecursive(s, sup))
                    && isSubtypeNoCapture(sup.getEnclosingType(),
                                          s.getEnclosingType());
            }

            @Override
            public Boolean visitArrayType(ArrayType t, Type s) {
                if (s.tag == ARRAY) {
                    if (t.elemtype.tag <= lastBaseTag)
                        return isSameType(t.elemtype, elemtype(s));
                    else
                        return isSubtypeNoCapture(t.elemtype, elemtype(s));
                }

                if (s.tag == CLASS) {
                    Name sname = s.tsym.getQualifiedName();
                    return sname == names.java_lang_Object
                        || sname == names.java_lang_Cloneable
                        || sname == names.java_io_Serializable;
                }

                return false;
            }

            @Override
            public Boolean visitUndetVar(UndetVar t, Type s) {
                //todo: test against origin needed? or replace with substitution?
                if (t == s || t.qtype == s || s.tag == ERROR || s.tag == UNKNOWN)
                    return true;

                if (t.inst != null)
                    return isSubtypeNoCapture(t.inst, s); // TODO: ", warn"?

                t.hibounds = t.hibounds.prepend(s);
                return true;
            }

            @Override
            public Boolean visitErrorType(ErrorType t, Type s) {
                return true;
            }
        };

    /**
     * Is t a subtype of every type in given list `ts'?<br>
     * (not defined for Method and ForAll types)<br>
     * Allows unchecked conversions.
     */
    public boolean isSubtypeUnchecked(Type t, List<Type> ts, Warner warn) {
        for (List<Type> l = ts; l.nonEmpty(); l = l.tail)
            if (!isSubtypeUnchecked(t, l.head, warn))
                return false;
        return true;
    }

    /**
     * Are corresponding elements of ts subtypes of ss?  If lists are
     * of different length, return false.
     */
    public boolean isSubtypes(List<Type> ts, List<Type> ss) {
        while (ts.tail != null && ss.tail != null
               /*inlined: ts.nonEmpty() && ss.nonEmpty()*/ &&
               isSubtype(ts.head, ss.head)) {
            ts = ts.tail;
            ss = ss.tail;
        }
        return ts.tail == null && ss.tail == null;
        /*inlined: ts.isEmpty() && ss.isEmpty();*/
    }

    /**
     * Are corresponding elements of ts subtypes of ss, allowing
     * unchecked conversions?  If lists are of different length,
     * return false.
     **/
    public boolean isSubtypesUnchecked(List<Type> ts, List<Type> ss, Warner warn) {
        while (ts.tail != null && ss.tail != null
               /*inlined: ts.nonEmpty() && ss.nonEmpty()*/ &&
               isSubtypeUnchecked(ts.head, ss.head, warn)) {
            ts = ts.tail;
            ss = ss.tail;
        }
        return ts.tail == null && ss.tail == null;
        /*inlined: ts.isEmpty() && ss.isEmpty();*/
    }
    // </editor-fold>

    // <editor-fold defaultstate="collapsed" desc="isSuperType">
    /**
     * Is t a supertype of s?
     */
    public boolean isSuperType(Type t, Type s) {
        switch (t.tag) {
        case ERROR:
            return true;
        case UNDETVAR: {
            UndetVar undet = (UndetVar)t;
            if (t == s ||
                undet.qtype == s ||
                s.tag == ERROR ||
                s.tag == BOT) return true;
            if (undet.inst != null)
                return isSubtype(s, undet.inst);
            undet.lobounds = undet.lobounds.prepend(s);
            return true;
        }
        default:
            return isSubtype(s, t);
        }
    }
    // </editor-fold>

    // <editor-fold defaultstate="collapsed" desc="isSameType">
    /**
     * Are corresponding elements of the lists the same type?  If
     * lists are of different length, return false.
     */
    public boolean isSameTypes(List<Type> ts, List<Type> ss) {
        while (ts.tail != null && ss.tail != null
               /*inlined: ts.nonEmpty() && ss.nonEmpty()*/ &&
               isSameType(ts.head, ss.head)) {
            ts = ts.tail;
            ss = ss.tail;
        }
        return ts.tail == null && ss.tail == null;
        /*inlined: ts.isEmpty() && ss.isEmpty();*/
    }

    /**
     * Is t the same type as s?
     */
    public boolean isSameType(Type t, Type s) {
        return isSameType.visit(t, s);
    }
    // where
        private TypeRelation isSameType = new TypeRelation() {

            public Boolean visitType(Type t, Type s) {
                if (t == s)
                    return true;

                if (s.tag >= firstPartialTag)
                    return visit(s, t);

                switch (t.tag) {
                case BYTE: case CHAR: case SHORT: case INT: case LONG: case FLOAT:
                case DOUBLE: case BOOLEAN: case VOID: case BOT: case NONE:
                    return t.tag == s.tag;
                case TYPEVAR:
                    return s.isSuperBound()
                        && !s.isExtendsBound()
                        && visit(t, upperBound(s));
                default:
                    throw new AssertionError("isSameType " + t.tag);
                }
            }

            @Override
            public Boolean visitWildcardType(WildcardType t, Type s) {
                if (s.tag >= firstPartialTag)
                    return visit(s, t);
                else
                    return false;
            }

            @Override
            public Boolean visitClassType(ClassType t, Type s) {
                if (t == s)
                    return true;

                if (s.tag >= firstPartialTag)
                    return visit(s, t);

                if (s.isSuperBound() && !s.isExtendsBound())
                    return visit(t, upperBound(s)) && visit(t, lowerBound(s));

                if (t.isCompound() && s.isCompound()) {
                    if (!visit(supertype(t), supertype(s)))
                        return false;

                    HashSet<SingletonType> set = new HashSet<SingletonType>();
                    for (Type x : interfaces(t))
                        set.add(new SingletonType(x));
                    for (Type x : interfaces(s)) {
                        if (!set.remove(new SingletonType(x)))
                            return false;
                    }
                    return (set.size() == 0);
                }
                return t.tsym == s.tsym
                    && visit(t.getEnclosingType(), s.getEnclosingType())
                    && containsTypeEquivalent(t.getTypeArguments(), s.getTypeArguments());
            }

            @Override
            public Boolean visitArrayType(ArrayType t, Type s) {
                if (t == s)
                    return true;

                if (s.tag >= firstPartialTag)
                    return visit(s, t);

                return s.tag == ARRAY
                    && containsTypeEquivalent(t.elemtype, elemtype(s));
            }

            @Override
            public Boolean visitMethodType(MethodType t, Type s) {
                // isSameType for methods does not take thrown
                // exceptions into account!
                return hasSameArgs(t, s) && visit(t.getReturnType(), s.getReturnType());
            }

            @Override
            public Boolean visitPackageType(PackageType t, Type s) {
                return t == s;
            }

            @Override
            public Boolean visitForAll(ForAll t, Type s) {
                if (s.tag != FORALL)
                    return false;

                ForAll forAll = (ForAll)s;
                return hasSameBounds(t, forAll)
                    && visit(t.qtype, subst(forAll.qtype, forAll.tvars, t.tvars));
            }

            @Override
            public Boolean visitUndetVar(UndetVar t, Type s) {
                if (s.tag == WILDCARD)
                    // FIXME, this might be leftovers from before capture conversion
                    return false;

                if (t == s || t.qtype == s || s.tag == ERROR || s.tag == UNKNOWN)
                    return true;

                if (t.inst != null)
                    return visit(t.inst, s);

                t.inst = fromUnknownFun.apply(s);
                for (List<Type> l = t.lobounds; l.nonEmpty(); l = l.tail) {
                    if (!isSubtype(l.head, t.inst))
                        return false;
                }
                for (List<Type> l = t.hibounds; l.nonEmpty(); l = l.tail) {
                    if (!isSubtype(t.inst, l.head))
                        return false;
                }
                return true;
            }

            @Override
            public Boolean visitErrorType(ErrorType t, Type s) {
                return true;
            }
        };
    // </editor-fold>

    // <editor-fold defaultstate="collapsed" desc="fromUnknownFun">
    /**
     * A mapping that turns all unknown types in this type to fresh
     * unknown variables.
     */
    public Mapping fromUnknownFun = new Mapping("fromUnknownFun") {
            public Type apply(Type t) {
                if (t.tag == UNKNOWN) return new UndetVar(t);
                else return t.map(this);
            }
        };
    // </editor-fold>

    // <editor-fold defaultstate="collapsed" desc="Contains Type">
    public boolean containedBy(Type t, Type s) {
        switch (t.tag) {
        case UNDETVAR:
            if (s.tag == WILDCARD) {
                UndetVar undetvar = (UndetVar)t;

                // Because of wildcard capture, s must be on the left
                // hand side of an assignment.  Furthermore, t is an
                // underconstrained type variable, for example, one
                // that is only used in the return type of a method.
                // If the type variable is truly underconstrained, it
                // cannot have any low bounds:
                assert undetvar.lobounds.isEmpty() : undetvar;

                undetvar.inst = glb(upperBound(s), undetvar.inst);
                return true;
            } else {
                return isSameType(t, s);
            }
        case ERROR:
            return true;
        default:
            return containsType(s, t);
        }
    }