package soot.toolkits.exceptions;
/*-
 * #%L
 * Soot - a J*va Optimization Framework
 * %%
 * Copyright (C) 2003 John Jorgensen
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 2.1 of the
 * License, or (at your option) any later version.
 * 
 * This program 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 Lesser Public License for more details.
 * 
 * You should have received a copy of the GNU General Lesser Public
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/lgpl-2.1.html>.
 * #L%
 */

import com.google.common.cache.CacheBuilder;

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

import soot.AnySubType;
import soot.FastHierarchy;
import soot.G;
import soot.RefLikeType;
import soot.RefType;
import soot.Scene;
import soot.Singletons;
import soot.SootClass;
import soot.Unit;
import soot.options.Options;

/**
 * <p>
 * A class for representing the set of exceptions that an instruction may throw.
 * </p>
 *
 * <p>
 * <code>ThrowableSet</code> does not implement the {@link java.util.Set} interface, so perhaps it is misnamed. Instead, it
 * provides only the operations that we require for determining whether a given statement might throw an exception that would
 * be caught by a given handler.
 * </p>
 *
 * <p>
 * There is a limitation on the combinations of operations permitted on a <code>ThrowableSet</code>. The
 * <code>ThrowableSet</code>s returned by {@link #whichCatchableAs(RefType)} cannot be involved in subsequent
 * <code>add()</code> or <code>whichCatchableAs()</code> operations. That is, given
 *
 * <blockquote> <code>p = s.whichCatchableAs(r)</code> </blockquote>
 *
 * for any <code>ThrowableSet</code> <code>s</code> and {@link soot.RefType RefType} <code>r</code>, and
 *
 * <blockquote> <code>t == p.getUncaught()</code> or <code>t == p.getCaught()</code> </blockquote>
 *
 * then calls to <code>t.add(r)</code>, <code>t.add(a)</code>, and <code>s.add(t)</code>, will throw an
 * {@link ThrowableSet.AlreadyHasExclusionsException}, for any <code>RefType</code> <code>r</code>, {@link AnySubType}
 * <code>a</code>, and <code>ThrowableSet</code> <code>t</code>.
 * </p>
 *
 * <p>
 * Actually the restrictions implemented are not quite so strict (there are some combinations of
 * <code>whichCatchableAs()</code> followed by <code>add()</code> which will not raise an exception), but a more accurate
 * description would require reference to the internals of the current implementation. The restrictions should not be too
 * onerous for <code>ThrowableSet</code>'s anticipated uses: we expect <code>ThrowableSet</code>s to grow by accumulating all
 * the exception types that a given {@link Unit} may throw, then, shrink as the types caught by different exception handlers
 * are removed to yield the sets representing exceptions which escape those handlers.
 * </p>
 *
 * <p>
 * The <code>ThrowableSet</code> class is intended to be immutable (hence the <code>final</code> modifier on its
 * declaration). It does not take the step of guaranteeing immutability by cloning the <code>RefLikeType</code> objects it
 * contains, though, because we trust {@link Scene} to enforce the existence of only one <code>RefLikeType</code> instance
 * with a given name.
 * </p>
 */

public class ThrowableSet {

  private static final boolean INSTRUMENTING = false;
  private final SootClass JAVA_LANG_OBJECT_CLASS = Scene.v().getObjectType().getSootClass();

  /**
   * Set of exception types included within the set.
   */
  protected final Set<RefLikeType> exceptionsIncluded;
  /**
   * Set of exception types which, though members of exceptionsIncluded, are to be excluded from the types represented by
   * this <code>ThrowableSet</code>. To simplify the implementation, once a <code>ThrowableSet</code> has any excluded types,
   * the various <code>add()</code> methods of this class must bar additions of subtypes of those excluded types.
   */
  protected final Set<AnySubType> exceptionsExcluded;
  /**
   * A map from ({@link RefLikeType} \\union <code>ThrowableSet</code>) to <code>ThrowableSet</code>. If the mapping (k,v) is
   * in <code>memoizedAdds</code> and k is a <code>ThrowableSet</code>, then v is the set that results from adding all
   * elements in k to <code>this</code>. If (k,v) is in <code>memoizedAdds</code> and k is a {@link RefLikeType}, then v is
   * the set that results from adding k to <code>this</code>.
   */
  protected Map<Object, ThrowableSet> memoizedAdds;

  /**
   * Constructs a <code>ThrowableSet</code> which contains the exception types represented in <code>include</code>, except
   * for those which are also in <code>exclude</code>. The constructor is private to ensure that the only way to get a new
   * <code>ThrowableSet</code> is by adding elements to or removing them from an existing set.
   *
   * @param include
   *          The set of {@link RefType} and {@link AnySubType} objects representing the types to be included in the set.
   * @param exclude
   *          The set of {@link AnySubType} objects representing the types to be excluded from the set.
   */
  protected ThrowableSet(Set<RefLikeType> include, Set<AnySubType> exclude) {
    exceptionsIncluded = getImmutable(include);
    exceptionsExcluded = getImmutable(exclude);
    // We don't need to clone include and exclude to guarantee
    // immutability since ThrowableSet(Set,Set) is private to this
    // class, where it is only called (via
    // Manager.v().registerSetIfNew()) with arguments which the
    // callers do not subsequently modify.
  }

  private static <T> Set<T> getImmutable(Set<T> in) {
    if ((null == in) || in.isEmpty()) {
      return Collections.emptySet();
    }
    if (1 == in.size()) {
      return Collections.singleton(in.iterator().next());
    }
    return Collections.unmodifiableSet(in);
  }

  /**
   * Returns an {@link Iterator} over a {@link Collection} of Throwable types which iterates over its elements in a
   * consistent order (maintaining an ordering that is consistent across different runs makes it easier to compare sets
   * generated by different implementations of the CFG classes).
   *
   * @param coll
   *          The collection to iterate over.
   *
   * @return An iterator which presents the elements of <code>coll</code> in order.
   */
  private static <T extends RefLikeType> Iterator<T> sortedThrowableIterator(Collection<T> coll) {
    if (coll.size() <= 1) {
      return coll.iterator();
    } else {
      @SuppressWarnings("unchecked")
      T[] array = (T[]) coll.toArray(new RefLikeType[coll.size()]);
      Arrays.sort(array, new ThrowableComparator<T>());
      return Arrays.asList(array).iterator();
    }
  }

  private ThrowableSet getMemoizedAdds(Object key) {
    return memoizedAdds == null ? null : memoizedAdds.get(key);
  }

  private void addToMemoizedAdds(Object key, ThrowableSet value) {
    if (memoizedAdds == null) {
      memoizedAdds = new ConcurrentHashMap<>();
    }
    memoizedAdds.put(key, value);
  }

  /**
   * Returns a <code>ThrowableSet</code> which contains <code>e</code> in addition to the exceptions in this
   * <code>ThrowableSet</code>.
   *
   * <p>
   * Add <code>e</code> as a {@link RefType} when you know that the run-time class of the exception you are representing is
   * necessarily <code>e</code> and cannot be a subclass of <code>e</code>.
   *
   * <p>
   * For example, if you were recording the type of the exception thrown by
   *
   * <pre>
   * throw new IOException(&quot;Permission denied&quot;);
   * </pre>
   *
   * you would call
   *
   * <pre>
   * <code>add(Scene.v().getRefType("java.lang.Exception.IOException"))</code>
   * </pre>
   *
   * since the class of the exception is necessarily <code>IOException</code>.
   *
   * @param e
   *          the exception class
   *
   * @return a set containing <code>e</code> as well as the exceptions in this set.
   *
   * @throws {@link
   *           ThrowableSet.IllegalStateException} if this <code>ThrowableSet</code> is the result of a
   *           {@link #whichCatchableAs(RefType)} operation and, thus, unable to represent the addition of <code>e</code>.
   */
  public ThrowableSet add(RefType e) throws ThrowableSet.AlreadyHasExclusionsException {
    if (INSTRUMENTING) {
      Manager.v().addsOfRefType++;
    }
    if (this.exceptionsIncluded.contains(e)) {
      if (INSTRUMENTING) {
        Manager.v().addsInclusionFromMap++;
        Manager.v().addsExclusionWithoutSearch++;
      }
      return this;
    }

    ThrowableSet result = getMemoizedAdds(e);
    if (result != null) {
      if (INSTRUMENTING) {
        Manager.v().addsInclusionFromMemo++;
        Manager.v().addsExclusionWithoutSearch++;
      }
      return result;
    }

    if (INSTRUMENTING) {
      Manager.v().addsInclusionFromSearch++;
      if (exceptionsExcluded.isEmpty()) {
        Manager.v().addsExclusionWithoutSearch++;
      } else {
        Manager.v().addsExclusionWithSearch++;
      }
    }

    FastHierarchy hierarchy = Scene.v().getOrMakeFastHierarchy();
    boolean eHasNoHierarchy = hasNoHierarchy(e);

    for (AnySubType excludedType : exceptionsExcluded) {
      RefType exclusionBase = excludedType.getBase();
      if ((eHasNoHierarchy && exclusionBase.equals(e)) || (!eHasNoHierarchy && hierarchy.canStoreType(e, exclusionBase))) {
        throw new AlreadyHasExclusionsException("ThrowableSet.add(RefType): adding" + e.toString() + " to the set [ "
            + this.toString() + "] where " + exclusionBase.toString() + " is excluded.");
      }
    }

    // If this is a real class, we need to check whether we already have it
    // in the list through subtyping.
    if (!eHasNoHierarchy) {
      for (RefLikeType incumbent : exceptionsIncluded) {
        if (incumbent instanceof AnySubType) {
          // Need to use incumbent.getBase() because
          // hierarchy.canStoreType() assumes that parent
          // is not an AnySubType.
          RefType incumbentBase = ((AnySubType) incumbent).getBase();
          if (hierarchy.canStoreType(e, incumbentBase)) {
            addToMemoizedAdds(e, this);
            return this;
          }
        } else if (!(incumbent instanceof RefType)) {
          // assertion failure.
          throw new IllegalStateException(
              "ThrowableSet.add(RefType): Set element " + incumbent.toString() + " is neither a RefType nor an AnySubType.");
        }
      }
    }
    Set<RefLikeType> resultSet = new HashSet<>(this.exceptionsIncluded);
    resultSet.add(e);
    result = Manager.v().registerSetIfNew(resultSet, this.exceptionsExcluded);
    addToMemoizedAdds(e, result);
    return result;
  }

  private boolean hasNoHierarchy(RefType type) {
    final SootClass sootClass = type.getSootClass();
    return !(sootClass.hasSuperclass() || JAVA_LANG_OBJECT_CLASS == sootClass);
  }

  /**
   * Returns a <code>ThrowableSet</code> which contains <code>e</code> and all of its subclasses as well as the exceptions in
   * this set.
   *
   * <p>
   * <code>e</code> should be an instance of {@link AnySubType} if you know that the compile-time type of the exception you
   * are representing is <code>e</code>, but the exception may be instantiated at run-time by a subclass of <code>e</code>.
   *
   * <p>
   * For example, if you were recording the type of the exception thrown by
   *
   * <pre>
   * catch (IOException e) {
   *    throw e;
   * }
   * </pre>
   *
   * you would call
   *
   * <pre>
   * <code>add(AnySubtype.v(Scene.v().getRefType("java.lang.Exception.IOException")))</code>
   * </pre>
   *
   * since the handler might rethrow any subclass of <code>IOException</code>.
   *
   * @param e
   *          represents a subtree of the exception class hierarchy to add to this set.
   *
   * @return a set containing <code>e</code> and all its subclasses, as well as the exceptions represented by this set.
   *
   * @throws ThrowableSet.AlreadyHasExclusionsException
   *           if this <code>ThrowableSet</code> is the result of a {@link #whichCatchableAs(RefType)} operation and, thus,
   *           unable to represent the addition of <code>e</code>.
   */
  public ThrowableSet add(AnySubType e) throws ThrowableSet.AlreadyHasExclusionsException {
    if (INSTRUMENTING) {
      Manager.v().addsOfAnySubType++;
    }

    ThrowableSet result = getMemoizedAdds(e);
    if (result != null) {
      if (INSTRUMENTING) {
        Manager.v().addsInclusionFromMemo++;
        Manager.v().addsExclusionWithoutSearch++;
      }
      return result;
    }
    // java.lang.Object is managed by the Scene -> guaranteed to only have one instance of the Object class
    final SootClass objectClass = Scene.v().getObjectType().getSootClass();

    FastHierarchy hierarchy = Scene.v().getOrMakeFastHierarchy();
    RefType newBase = e.getBase();
    boolean newBaseHasNoHierarchy = hasNoHierarchy(newBase);

    if (INSTRUMENTING) {
      if (exceptionsExcluded.isEmpty()) {
        Manager.v().addsExclusionWithoutSearch++;
      } else {
        Manager.v().addsExclusionWithSearch++;
      }
    }
    for (AnySubType excludedType : exceptionsExcluded) {
      RefType exclusionBase = excludedType.getBase();
      boolean exclusionBaseHasNoHierarchy = !(exclusionBase.getSootClass().hasSuperclass() || //
          exclusionBase.getSootClass() == objectClass);

      boolean isExcluded = exclusionBaseHasNoHierarchy && exclusionBase.equals(newBase);
      isExcluded |= !exclusionBaseHasNoHierarchy
          && (hierarchy.canStoreType(newBase, exclusionBase) || hierarchy.canStoreType(exclusionBase, newBase));

      if (isExcluded) {
        if (INSTRUMENTING) {
          // To ensure that the subcategories total properly:
          Manager.v().addsInclusionInterrupted++;
        }
        throw new AlreadyHasExclusionsException("ThrowableSet.add(" + e.toString() + ") to the set [ " + this.toString()
            + "] where " + exclusionBase.toString() + " is excluded.");
      }
    }

    if (this.exceptionsIncluded.contains(e)) {
      if (INSTRUMENTING) {
        Manager.v().addsInclusionFromMap++;
      }
      return this;
    }

    if (INSTRUMENTING) {
      Manager.v().addsInclusionFromSearch++;
    }

    int changes = 0;
    boolean addNewException = true;
    Set<RefLikeType> resultSet = new HashSet<>();

    for (RefLikeType incumbent : this.exceptionsIncluded) {
      if (incumbent instanceof RefType) {
        if (hierarchy.canStoreType(incumbent, newBase)) {
          // Omit incumbent from result.
          changes++;
        } else {
          resultSet.add(incumbent);
        }
      } else if (incumbent instanceof AnySubType) {
        RefType incumbentBase = ((AnySubType) incumbent).getBase();
        if (newBaseHasNoHierarchy) {
          if (!incumbentBase.equals(newBase)) {
            resultSet.add(incumbent);
          }
        }
        // We have to use the base types in these hierarchy
        // calls
        // because we want to know if _all_ possible
        // types represented by e can be represented by
        // the incumbent, or vice versa.
        else if (hierarchy.canStoreType(newBase, incumbentBase)) {
          addNewException = false;
          resultSet.add(incumbent);
        } else if (hierarchy.canStoreType(incumbentBase, newBase)) {
          // Omit incumbent from result;
          changes++;
        } else {
          resultSet.add(incumbent);
        }
      } else { // assertion failure.
        throw new IllegalStateException("ThrowableSet.add(AnySubType): Set element " + incumbent.toString()
            + " is neither a RefType nor an AnySubType.");
      }
    }
    if (addNewException) {
      resultSet.add(e);
      changes++;
    }
    if (changes > 0) {
      result = Manager.v().registerSetIfNew(resultSet, this.exceptionsExcluded);
    } else {
      result = this;
    }
    addToMemoizedAdds(e, result);
    return result;
  }

  /**
   * Returns a <code>ThrowableSet</code> which contains all the exceptions in <code>s</code> in addition to those in this
   * <code>ThrowableSet</code>.
   *
   * @param s
   *          set of exceptions to add to this set.
   *
   * @return the union of this set with <code>s</code>
   *
   * @throws ThrowableSet.AlreadyHasExclusionsException
   *           if this <code>ThrowableSet</code> or <code>s</code> is the result of a {@link #whichCatchableAs(RefType)}
   *           operation, so that it is not possible to represent the addition of <code>s</code> to this
   *           <code>ThrowableSet</code>.
   */
  public ThrowableSet add(ThrowableSet s) throws ThrowableSet.AlreadyHasExclusionsException {
    if (INSTRUMENTING) {
      Manager.v().addsOfSet++;
    }
    if ((exceptionsExcluded.size() > 0) || (s.exceptionsExcluded.size() > 0)) {
      throw new AlreadyHasExclusionsException(
          "ThrowableSet.Add(ThrowableSet): attempt to add to [" + this.toString() + "] after removals recorded.");
    }
    ThrowableSet result = getMemoizedAdds(s);
    if (result == null) {
      if (INSTRUMENTING) {
        Manager.v().addsInclusionFromSearch++;
        Manager.v().addsExclusionWithoutSearch++;
      }
      result = this.add(s.exceptionsIncluded);
      addToMemoizedAdds(s, result);
    } else if (INSTRUMENTING) {
      Manager.v().addsInclusionFromMemo++;
      Manager.v().addsExclusionWithoutSearch++;
    }
    return result;
  }

  /**
   * Returns true if the throwable set is empty and false otherwise.
   * 
   * @return true if the throwable set is empty.
   */
  public boolean isEmpty() {
    return exceptionsIncluded.isEmpty();
  }

  /**
   * Returns a <code>ThrowableSet</code> which contains all the exceptions in <code>addedExceptions</code> in addition to
   * those in this <code>ThrowableSet</code>.
   *
   * @param addedExceptions
   *          a set of {@link RefLikeType} and {@link AnySubType} objects to be added to the types included in this
   *          <code>ThrowableSet</code>.
   *
   * @return a set containing all the <code>addedExceptions</code> as well as the exceptions in this set.
   */
  private ThrowableSet add(Set<RefLikeType> addedExceptions) {
    Set<RefLikeType> resultSet = new HashSet<>(this.exceptionsIncluded);
    int changes = 0;
    FastHierarchy hierarchy = Scene.v().getOrMakeFastHierarchy();

    // This algorithm is O(n m), where n and m are the sizes of the
    // two sets, so hope that the sets are small.

    for (RefLikeType newType : addedExceptions) {
      if (!resultSet.contains(newType)) {
        boolean addNewType = true;
        if (newType instanceof RefType) {
          for (RefLikeType incumbentType : resultSet) {
            if (incumbentType instanceof RefType) {
              if (newType == incumbentType) {
                // assertion failure.
                throw new IllegalStateException(
                    "ThrowableSet.add(Set): resultSet.contains() failed to screen duplicate RefType " + newType);
              }
            } else if (incumbentType instanceof AnySubType) {
              RefType incumbentBase = ((AnySubType) incumbentType).getBase();
              if (hierarchy.canStoreType(newType, incumbentBase)) {
                // No need to add this class.
                addNewType = false;
              }
            } else { // assertion failure.
              throw new IllegalStateException("ThrowableSet.add(Set): incumbent Set element " + incumbentType
                  + " is neither a RefType nor an AnySubType.");
            }
          }
        } else if (newType instanceof AnySubType) {
          RefType newBase = ((AnySubType) newType).getBase();
          for (Iterator<RefLikeType> j = resultSet.iterator(); j.hasNext();) {
            RefLikeType incumbentType = j.next();
            if (incumbentType instanceof RefType) {
              RefType incumbentBase = (RefType) incumbentType;
              if (hierarchy.canStoreType(incumbentBase, newBase)) {
                j.remove();
                changes++;
              }
            } else if (incumbentType instanceof AnySubType) {
              RefType incumbentBase = ((AnySubType) incumbentType).getBase();
              if (newBase == incumbentBase) {
                // assertion failure.
                throw new IllegalStateException(
                    "ThrowableSet.add(Set): resultSet.contains() failed to screen duplicate AnySubType " + newBase);
              } else if (hierarchy.canStoreType(incumbentBase, newBase)) {
                j.remove();
                changes++;
              } else if (hierarchy.canStoreType(newBase, incumbentBase)) {
                // No need to add this class.
                addNewType = false;
              }
            } else { // assertion failure.
              throw new IllegalStateException(
                  "ThrowableSet.add(Set): old Set element " + incumbentType + " is neither a RefType nor an AnySubType.");
            }
          }
        } else { // assertion failure.
          throw new IllegalArgumentException(
              "ThrowableSet.add(Set): new Set element " + newType + " is neither a RefType nor an AnySubType.");
        }
        if (addNewType) {
          changes++;
          resultSet.add(newType);
        }
      }
    }

    ThrowableSet result = null;
    if (changes > 0) {
      result = Manager.v().registerSetIfNew(resultSet, this.exceptionsExcluded);
    } else {
      result = this;
    }
    return result;
  }

  /**
   * Returns a <code>ThrowableSet</code> which contains all the exceptions in this <code>ThrowableSet</code> except for those
   * in <code>removedExceptions</code>.
   *
   * @param removedExceptions
   *          a set of {@link RefLikeType} and {@link AnySubType} objects to be added to the types included in this
   *          <code>ThrowableSet</code>.
   *
   * @return a set containing all the <code>addedExceptions</code> as well as the exceptions in this set.
   */
  private ThrowableSet remove(Set<RefLikeType> removedExceptions) {
    // Is there anything to remove?
    if (removedExceptions.isEmpty()) {
      return this;
    }

    int changes = 0;
    Set<RefLikeType> resultSet = new HashSet<>(this.exceptionsIncluded);
    for (RefLikeType tp : removedExceptions) {
      if (tp instanceof RefType) {
        if (resultSet.remove(tp)) {
          changes++;
        }
      }
    }

    ThrowableSet result = null;
    if (changes > 0) {
      result = Manager.v().registerSetIfNew(resultSet, this.exceptionsExcluded);
    } else {
      result = this;
    }
    return result;
  }

  /**
   * Returns a <code>ThrowableSet</code> which contains all the exceptions from the current set except for those in the given
   * <code>ThrowableSet</code>.
   *
   * @param s
   *          The set containing the exceptions to exclude from the new set
   *
   * @return The exceptions that are only in this set, but not in the given set
   *
   * @throws ThrowableSet.AlreadyHasExclusionsException
   *           if this <code>ThrowableSet</code> or <code>s</code> is the result of a {@link #whichCatchableAs(RefType)}
   *           operation, so that it is not possible to represent the addition of <code>s</code> to this
   *           <code>ThrowableSet</code>.
   */
  public ThrowableSet remove(ThrowableSet s) {
    if ((exceptionsExcluded.size() > 0) || (s.exceptionsExcluded.size() > 0)) {
      throw new AlreadyHasExclusionsException(
          "ThrowableSet.Add(ThrowableSet): attempt to add to [" + this.toString() + "] after removals recorded.");
    }

    // Remove the exceptions
    return this.remove(s.exceptionsIncluded);
  }

  /**
   * Indicates whether this ThrowableSet includes some exception that might be caught by a handler argument of the type
   * <code>catcher</code>.
   *
   * @param catcher
   *          type of the handler parameter to be tested.
   *
   * @return <code>true</code> if this set contains an exception type that might be caught by <code>catcher</code>, false if
   *         it does not.
   */
  public boolean catchableAs(RefType catcher) {
    if (INSTRUMENTING) {
      Manager.v().catchableAsQueries++;
    }

    FastHierarchy h = Scene.v().getOrMakeFastHierarchy();
    /**
     * Originally this implementation had checked if the catcher.getSootClass() is a phantom class. However this makes
     * problems in case the soot option no_bodies_for_excluded==true because certain library classes will be marked as
     * phantom classes even if they have a hierarchy. The workaround for this problem is to check for the suerClass. As every
     * class except java.lang.Object have a superClass (even interfaces have!) only real phantom classes can be identified
     * using this method.
     */
    boolean catcherHasNoHierarchy = hasNoHierarchy(catcher);

    if (exceptionsExcluded.size() > 0) {
      if (INSTRUMENTING) {
        Manager.v().catchableAsFromSearch++;
      }
      for (AnySubType exclusion : exceptionsExcluded) {
        if (catcherHasNoHierarchy) {
          if (exclusion.getBase().equals(catcher)) {
            return false;
          }
        } else if (h.canStoreType(catcher, exclusion.getBase())) {
          return false;
        }
      }
    }

    if (exceptionsIncluded.contains(catcher)) {
      if (INSTRUMENTING) {
        if (exceptionsExcluded.size() == 0) {
          Manager.v().catchableAsFromMap++;
        } else {
          Manager.v().catchableAsFromSearch++;
        }
      }
      return true;
    } else {
      if (INSTRUMENTING) {
        if (exceptionsExcluded.size() == 0) {
          Manager.v().catchableAsFromSearch++;
        }
      }
      for (RefLikeType thrownType : exceptionsIncluded) {
        if (thrownType instanceof RefType) {
          if (thrownType == catcher) {
            // assertion failure.
            throw new IllegalStateException(
                "ThrowableSet.catchableAs(RefType): exceptions.contains() failed to match contained RefType " + catcher);
          } else if (!catcherHasNoHierarchy && h.canStoreType(thrownType, catcher)) {
            return true;
          }
        } else {
          RefType thrownBase = ((AnySubType) thrownType).getBase();
          if (catcherHasNoHierarchy) {
            if (thrownBase.equals(catcher) || thrownBase.getClassName().equals("java.lang.Throwable")) {
              return true;
            }
          }
          // At runtime, thrownType might be instantiated by any
          // of thrownBase's subtypes, so:
          else if (h.canStoreType(thrownBase, catcher) || h.canStoreType(catcher, thrownBase)) {
            return true;
          }
        }
      }
      return false;
    }
  }

  /**
   * Partitions the exceptions in this <code>ThrowableSet</code> into those which would be caught by a handler with the
   * passed <code>catch</code> parameter type and those which would not.
   *
   * @param catcher
   *          type of the handler parameter to be tested.
   *
   * @return a pair of <code>ThrowableSet</code>s, one containing the types in this <code>ThrowableSet</code> which would be
   *         be caught as <code>catcher</code> and the other containing the types in this <code>ThrowableSet</code> which
   *         would not be caught as <code>catcher</code>.
   */
  public Pair whichCatchableAs(RefType catcher) {
    if (INSTRUMENTING) {
      Manager.v().removesOfAnySubType++;
    }

    FastHierarchy h = Scene.v().getOrMakeFastHierarchy();
    Set<RefLikeType> caughtIncluded = null;
    Set<AnySubType> caughtExcluded = null;
    Set<RefLikeType> uncaughtIncluded = null;
    Set<AnySubType> uncaughtExcluded = null;

    if (INSTRUMENTING) {
      Manager.v().removesFromSearch++;
    }
    boolean catcherHasNoHierarchy = hasNoHierarchy(catcher);

    for (AnySubType exclusion : exceptionsExcluded) {
      RefType exclusionBase = exclusion.getBase();

      // Is the current type explicitly excluded?
      if (catcherHasNoHierarchy && exclusionBase.equals(catcher)) {
        return new Pair(ThrowableSet.Manager.v().EMPTY, this);
      }

      if (h.canStoreType(catcher, exclusionBase)) {
        // Because the add() operations ban additions to sets
        // with exclusions, we can be sure no types in this are
        // caught by catcher.
        return new Pair(ThrowableSet.Manager.v().EMPTY, this);
      } else if (h.canStoreType(exclusionBase, catcher)) {
        // exclusion wouldn't be in exceptionsExcluded if one
        // of its supertypes were not in exceptionsIncluded,
        // so we know the next loop will add either that supertype
        // or catcher to caughtIncluded. Thus:
        caughtExcluded = addExceptionToSet(exclusion, caughtExcluded);
      } else {
        uncaughtExcluded = addExceptionToSet(exclusion, uncaughtExcluded);
      }
    }

    for (RefLikeType inclusion : exceptionsIncluded) {
      if (inclusion instanceof RefType) {
        // If the current type is has no hierarchy, we catch it if and
        // only if it is in the inclusion list and ignore any hierarchy.
        if (catcherHasNoHierarchy) {
          if (inclusion.equals(catcher)) {
            caughtIncluded = addExceptionToSet(inclusion, caughtIncluded);
          } else {
            uncaughtIncluded = addExceptionToSet(inclusion, uncaughtIncluded);
          }
        } else if (h.canStoreType(inclusion, catcher)) {
          caughtIncluded = addExceptionToSet(inclusion, caughtIncluded);
        } else {
          uncaughtIncluded = addExceptionToSet(inclusion, uncaughtIncluded);
        }
      } else {
        RefType base = ((AnySubType) inclusion).getBase();
        // If the current type is has no hierarchy, we catch it if and
        // only if it is in the inclusion list and ignore any hierarchy.
        if (catcherHasNoHierarchy) {
          if (base.equals(catcher)) {
            caughtIncluded = addExceptionToSet(inclusion, caughtIncluded);
          } else {
            if (base.getClassName().equals("java.lang.Throwable")) {
              caughtIncluded = addExceptionToSet(catcher, caughtIncluded);
            }
            uncaughtIncluded = addExceptionToSet(inclusion, uncaughtIncluded);
          }
        } else if (h.canStoreType(base, catcher)) {
          // All subtypes of base will be caught. Any exclusions
          // will already have been copied to caughtExcluded by
          // the preceding loop.
          caughtIncluded = addExceptionToSet(inclusion, caughtIncluded);
        } else if (h.canStoreType(catcher, base)) {
          // Some subtypes of base will be caught, and
          // we know that not all of those catchable subtypes
          // are among exceptionsExcluded, since in that case we
          // would already have returned from within the
          // preceding loop. So, remove AnySubType(catcher)
          // from the uncaught types.
          uncaughtIncluded = addExceptionToSet(inclusion, uncaughtIncluded);
          uncaughtExcluded = addExceptionToSet(AnySubType.v(catcher), uncaughtExcluded);
          caughtIncluded = addExceptionToSet(AnySubType.v(catcher), caughtIncluded);
          // Any already excluded subtypes of inclusion
          // which are subtypes of catcher will have been
          // added to caughtExcluded by the previous loop.
        } else {
          uncaughtIncluded = addExceptionToSet(inclusion, uncaughtIncluded);
        }
      }
    }
    ThrowableSet caughtSet = Manager.v().registerSetIfNew(caughtIncluded, caughtExcluded);
    ThrowableSet uncaughtSet = Manager.v().registerSetIfNew(uncaughtIncluded, uncaughtExcluded);
    return new Pair(caughtSet, uncaughtSet);
  }

  /**
   * Utility method for building sets of exceptional types for a {@link Pair}.
   *
   * @param e
   *          The exceptional type to add to the set.
   *
   * @param set
   *          The <code>Set</code> to which to add the types, or <code>null</code> if no <code>Set</code> has yet been
   *          allocated.
   *
   * @return A <code>Set</code> containing the elements in <code>set</code> plus <code>e</code>.
   */
  private <T> Set<T> addExceptionToSet(T e, Set<T> set) {
    if (set == null) {
      set = new HashSet<>();
    }
    set.add(e);
    return set;
  }

  /**
   * Returns a string representation of this <code>ThrowableSet</code>.
   */
  @Override
  public String toString() {
    StringBuffer buffer = new StringBuffer(this.toBriefString());
    buffer.append(":\n  ");
    for (RefLikeType ei : exceptionsIncluded) {
      buffer.append('+');
      buffer.append(ei == null ? "null" : ei.toString());
      // buffer.append(i.next().toString());
    }
    for (RefLikeType ee : exceptionsExcluded) {
      buffer.append('-');
      buffer.append(ee.toString());
    }
    return buffer.toString();
  }

  /**
   * Returns a cryptic identifier for this <code>ThrowableSet</code>, used to identify a set when it appears in a collection.
   */
  public String toBriefString() {
    return super.toString();
  }

  /**
   * <p>
   * Produce an abbreviated representation of this <code>ThrowableSet</code>, suitable for human consumption. The
   * abbreviations include:
   * </p>
   *
   * <ul>
   *
   * <li>The strings &ldquo;<code>java.lang.</code>&rdquo; is stripped from the beginning of exception names.</li>
   *
   * <li>The string &ldquo;<code>Exception</code>&rdquo; is stripped from the ends of exception names.</li>
   *
   * <li>Instances of <code>AnySubType</code> are indicated by surrounding the base type name with parentheses, rather than
   * with the string &ldquo; <code>Any_subtype_of_</code>&rdquo;</li>
   *
   * <li>If this <code>ThrowableSet</code> includes all the elements of {@link ThrowableSet.Manager#VM_ERRORS VM_ERRORS},
   * they are abbreviated as &ldquo;<code>vmErrors</code>&rdquo; rather than listed individually.</li>
   *
   * @return An abbreviated representation of the contents of this set.
   */
  public String toAbbreviatedString() {
    return toAbbreviatedString(exceptionsIncluded, '+') + toAbbreviatedString(exceptionsExcluded, '-');
  }

  /**
   * <p>
   * Utility method which prints the abbreviations of the elements in a passed {@link Set} of exception types.
   * </p>
   *
   * @param s
   *          The exceptions to print.
   *
   * @param connector
   *          The character to insert between exceptions.
   *
   * @return An abbreviated representation of the exceptions.
   */
  private String toAbbreviatedString(Set<? extends RefLikeType> s, char connector) {
    final String JAVA_LANG = "java.lang.";
    final String EXCEPTION = "Exception";

    Collection<RefLikeType> vmErrorThrowables = ThrowableSet.Manager.v().VM_ERRORS.exceptionsIncluded;
    boolean containsAllVmErrors = s.containsAll(vmErrorThrowables);
    StringBuffer buf = new StringBuffer();

    if (containsAllVmErrors) {
      buf.append(connector);
      buf.append("vmErrors");
    }

    for (Iterator<? extends RefLikeType> it = sortedThrowableIterator(s); it.hasNext();) {
      RefLikeType reflikeType = it.next();
      RefType baseType = null;
      if (reflikeType instanceof RefType) {
        baseType = (RefType) reflikeType;
        if (containsAllVmErrors && vmErrorThrowables.contains(baseType)) {
          continue; // Already accounted for vmErrors.
        } else {
          buf.append(connector);
        }
      } else if (reflikeType instanceof AnySubType) {
        buf.append(connector);
        buf.append('(');
        baseType = ((AnySubType) reflikeType).getBase();
      } else {
        throw new RuntimeException("Unsupported type " + reflikeType.getClass().getName());
      }
      String typeName = baseType.toString();
      int start = 0;
      int end = typeName.length();
      if (typeName.startsWith(JAVA_LANG)) {
        start += JAVA_LANG.length();
      }
      if (typeName.endsWith(EXCEPTION)) {
        end -= EXCEPTION.length();
      }
      buf.append(typeName, start, end);
      if (reflikeType instanceof AnySubType) {
        buf.append(')');
      }
    }
    return buf.toString();
  }

  /**
   * A package-private method to provide unit tests with access to the {@link RefLikeType} objects which represent the
   * <code>Throwable</code> types included in this set.
   *
   * @return an unmodifiable collection view of the <code>Throwable</code> types in this set.
   */
  Collection<RefLikeType> typesIncluded() {
    return exceptionsIncluded;
  }

  /**
   * A package-private method to provide unit tests with access to the {@link RefLikeType} objects which represent the
   * <code>Throwable</code> types excluded from this set.
   *
   * @return an unmodifiable collection view of the <code>Throwable</code> types excluded from this set.
   */
  Collection<AnySubType> typesExcluded() {
    return exceptionsExcluded;
  }

  /**
   * A package-private method to provide unit tests with access to ThrowableSet's internals.
   */
  Map<Object, ThrowableSet> getMemoizedAdds() {
    if (memoizedAdds == null) {
      return Collections.emptyMap();
    } else {
      return Collections.unmodifiableMap(memoizedAdds);
    }
  }

  @Override
  public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = (prime * result) + exceptionsIncluded.hashCode();
    result = (prime * result) + exceptionsExcluded.hashCode();
    return result;
  }

  @Override
  public boolean equals(Object obj) {
    if (this == obj) {
      return true;
    }
    if (obj == null) {
      return false;
    }
    if (getClass() != obj.getClass()) {
      return false;
    }
    ThrowableSet other = (ThrowableSet) obj;

    return exceptionsIncluded.equals(other.exceptionsIncluded) && exceptionsExcluded.equals(other.exceptionsExcluded);
  }

  /**
   * Singleton class for fields and initializers common to all ThrowableSet objects (i.e., these would be static fields and
   * initializers, in the absence of soot's {@link G} and {@link Singletons} classes).
   */
  public static class Manager {

    /**
     * <code>ThrowableSet</code> containing no exception classes.
     */
    public final ThrowableSet EMPTY;
    /**
     * <code>ThrowableSet</code> containing all the exceptions that may be thrown in the course of resolving a reference to
     * another class, including the process of loading, preparing, and verifying the referenced class.
     */
    public final ThrowableSet RESOLVE_CLASS_ERRORS;
    public final RefType RUNTIME_EXCEPTION;
    public final RefType ARITHMETIC_EXCEPTION;
    public final RefType ARRAY_STORE_EXCEPTION;
    public final RefType CLASS_CAST_EXCEPTION;
    public final RefType ILLEGAL_MONITOR_STATE_EXCEPTION;
    public final RefType INDEX_OUT_OF_BOUNDS_EXCEPTION;
    public final RefType ARRAY_INDEX_OUT_OF_BOUNDS_EXCEPTION;
    public final RefType NEGATIVE_ARRAY_SIZE_EXCEPTION;
    public final RefType NULL_POINTER_EXCEPTION;
    public final RefType INSTANTIATION_ERROR;
    /**
     * <code>ThrowableSet</code> representing all possible Throwables.
     */
    final ThrowableSet ALL_THROWABLES;
    /**
     * <code>ThrowableSet</code> containing all the asynchronous and virtual machine errors, which may be thrown by any
     * bytecode instruction at any point in the computation.
     */
    final ThrowableSet VM_ERRORS;
    /**
     * <code>ThrowableSet</code> containing all the exceptions that may be thrown in the course of resolving a reference to a
     * field.
     */
    final ThrowableSet RESOLVE_FIELD_ERRORS;
    /**
     * <code>ThrowableSet</code> containing all the exceptions that may be thrown in the course of resolving a reference to a
     * non-static method.
     */
    final ThrowableSet RESOLVE_METHOD_ERRORS;
    /**
     * <code>ThrowableSet</code> containing all the exceptions which may be thrown by instructions that have the potential to
     * cause a new class to be loaded and initialized (including UnsatisfiedLinkError, which is raised at runtime rather than
     * linking type).
     */
    final ThrowableSet INITIALIZATION_ERRORS;
    /**
     * This map stores all referenced <code>ThrowableSet</code>s.
     */
    private final Map<ThrowableSet, ThrowableSet> registry
        = CacheBuilder.newBuilder().weakValues().<ThrowableSet, ThrowableSet>build().asMap();
    private final int removesFromMap = 0;
    private final int removesFromMemo = 0;
    // counts for instrumenting:
    private int addsOfRefType = 0;
    private int addsOfAnySubType = 0;
    private int addsOfSet = 0;
    private int addsInclusionFromMap = 0;
    private int addsInclusionFromMemo = 0;
    private int addsInclusionFromSearch = 0;
    private int addsInclusionInterrupted = 0;
    private int addsExclusionWithSearch = 0;
    private int addsExclusionWithoutSearch = 0;
    private int removesOfAnySubType = 0;
    private int removesFromSearch = 0;
    private int registrationCalls = 0;
    private int catchableAsQueries = 0;
    private int catchableAsFromMap = 0;
    private int catchableAsFromSearch = 0;

    /**
     * Constructs a <code>ThrowableSet.Manager</code> for inclusion in Soot's global variable manager, {@link G}.
     *
     * @param g
     *          guarantees that the constructor may only be called from {@link Singletons}.
     */
    public Manager(Singletons.Global g) {
      // First ensure the Exception classes are represented in Soot. Note that Soot supports multiple target platforms such
      // as .net, which may use different exception classes. In that case, we just use null for the Java exception types.
      final Scene scene = Scene.v();

      // Runtime errors:
      RUNTIME_EXCEPTION = scene.getRefTypeUnsafe("java.lang.RuntimeException");
      ARITHMETIC_EXCEPTION = scene.getRefTypeUnsafe("java.lang.ArithmeticException");
      ARRAY_STORE_EXCEPTION = scene.getRefTypeUnsafe("java.lang.ArrayStoreException");
      CLASS_CAST_EXCEPTION = scene.getRefTypeUnsafe("java.lang.ClassCastException");
      ILLEGAL_MONITOR_STATE_EXCEPTION = scene.getRefTypeUnsafe("java.lang.IllegalMonitorStateException");
      INDEX_OUT_OF_BOUNDS_EXCEPTION = scene.getRefTypeUnsafe("java.lang.IndexOutOfBoundsException");
      ARRAY_INDEX_OUT_OF_BOUNDS_EXCEPTION = scene.getRefTypeUnsafe("java.lang.ArrayIndexOutOfBoundsException");
      NEGATIVE_ARRAY_SIZE_EXCEPTION = scene.getRefTypeUnsafe("java.lang.NegativeArraySizeException");
      NULL_POINTER_EXCEPTION = scene.getRefTypeUnsafe("java.lang.NullPointerException");

      INSTANTIATION_ERROR = scene.getRefType("java.lang.InstantiationError");

      EMPTY = registerSetIfNew(null, null);

      Set<RefLikeType> allThrowablesSet = new HashSet<>();
      allThrowablesSet.add(AnySubType.v(scene.getRefType("java.lang.Throwable")));
      ALL_THROWABLES = registerSetIfNew(allThrowablesSet, null);

      Set<RefLikeType> vmErrorSet = new HashSet<>();
      vmErrorSet.add(scene.getRefTypeUnsafe("java.lang.InternalError"));
      vmErrorSet.add(scene.getRefTypeUnsafe("java.lang.OutOfMemoryError"));
      vmErrorSet.add(scene.getRefTypeUnsafe("java.lang.StackOverflowError"));
      vmErrorSet.add(scene.getRefTypeUnsafe("java.lang.UnknownError"));

      // The Java library's deprecated Thread.stop(Throwable) method
      // would actually allow _any_ Throwable to be delivered
      // asynchronously, not just java.lang.ThreadDeath.
      vmErrorSet.add(scene.getRefTypeUnsafe("java.lang.ThreadDeath"));

      VM_ERRORS = registerSetIfNew(vmErrorSet, null);

      Set<RefLikeType> resolveClassErrorSet = new HashSet<>();
      resolveClassErrorSet.add(scene.getRefType("java.lang.ClassCircularityError"));
      // We add AnySubType(ClassFormatError) so that we can
      // avoid adding its subclass,
      // UnsupportedClassVersionError, explicitly. This is a
      // hack to allow Soot to analyze older class libraries
      // (UnsupportedClassVersionError was added in JDK 1.2).
      if (!Options.v().j2me()) {
        resolveClassErrorSet.add(AnySubType.v(Scene.v().getRefTypeUnsafe("java.lang.ClassFormatError")));
      }

      resolveClassErrorSet.add(scene.getRefTypeUnsafe("java.lang.IllegalAccessError"));
      resolveClassErrorSet.add(scene.getRefTypeUnsafe("java.lang.IncompatibleClassChangeError"));
      resolveClassErrorSet.add(scene.getRefTypeUnsafe("java.lang.LinkageError"));
      resolveClassErrorSet.add(scene.getRefTypeUnsafe("java.lang.NoClassDefFoundError"));
      resolveClassErrorSet.add(scene.getRefTypeUnsafe("java.lang.VerifyError"));
      RESOLVE_CLASS_ERRORS = registerSetIfNew(resolveClassErrorSet, null);

      Set<RefLikeType> resolveFieldErrorSet = new HashSet<>(resolveClassErrorSet);
      resolveFieldErrorSet.add(scene.getRefTypeUnsafe("java.lang.NoSuchFieldError"));
      RESOLVE_FIELD_ERRORS = registerSetIfNew(resolveFieldErrorSet, null);

      Set<RefLikeType> resolveMethodErrorSet = new HashSet<>(resolveClassErrorSet);
      resolveMethodErrorSet.add(scene.getRefTypeUnsafe("java.lang.AbstractMethodError"));
      resolveMethodErrorSet.add(scene.getRefTypeUnsafe("java.lang.NoSuchMethodError"));
      resolveMethodErrorSet.add(scene.getRefTypeUnsafe("java.lang.UnsatisfiedLinkError"));
      RESOLVE_METHOD_ERRORS = registerSetIfNew(resolveMethodErrorSet, null);

      // The static initializers of a newly loaded class might
      // throw any Error (if they threw an Exception---even a
      // RuntimeException---it would be replaced by an
      // ExceptionInInitializerError):
      //
      Set<RefLikeType> initializationErrorSet = new HashSet<>();
      initializationErrorSet.add(AnySubType.v(scene.getRefTypeUnsafe("java.lang.Error")));
      INITIALIZATION_ERRORS = registerSetIfNew(initializationErrorSet, null);
    }

    /**
     * Returns the single instance of <code>ThrowableSet.Manager</code>.
     *
     * @return Soot's <code>ThrowableSet.Manager</code>.
     */
    public static Manager v() {
      return G.v().soot_toolkits_exceptions_ThrowableSet_Manager();
    }

    /**
     * <p>
     * Returns a <code>ThrowableSet</code> representing the set of exceptions included in <code>include</code> minus the set
     * of exceptions included in <code>exclude</code>. Creates a new <code>ThrowableSet</code> only if there was not already
     * one whose contents correspond to <code>include</code> - <code>exclude</code>.
     * </p>
     *
     * @param include
     *          A set of {@link RefLikeType} objects representing exception types included in the result; may be
     *          <code>null</code> if there are no included types.
     *
     * @param exclude
     *          A set of {@link AnySubType} objects representing exception types excluded from the result; may be
     *          <code>null</code> if there are no excluded types.
     *
     * @return a <code>ThrowableSet</code> representing the set of exceptions corresponding to <code>include</code> -
     *         <code>exclude</code>.
     */
    protected ThrowableSet registerSetIfNew(Set<RefLikeType> include, Set<AnySubType> exclude) {
      if (INSTRUMENTING) {
        registrationCalls++;
      }
      ThrowableSet result = new ThrowableSet(include, exclude);
      ThrowableSet ref = registry.get(result);
      if (null != ref) {
        return ref;
      }
      registry.put(result, result);
      return result;
    }

    /**
     * Report the counts collected by instrumentation (for now, at least, there is no need to provide access to the
     * individual values as numbers).
     *
     * @return a string listing the counts.
     */
    public String reportInstrumentation() {
      int setCount = registry.size();

      StringBuffer buf = new StringBuffer("registeredSets: ").append(setCount).append("\naddsOfRefType: ")
          .append(addsOfRefType).append("\naddsOfAnySubType: ").append(addsOfAnySubType).append("\naddsOfSet: ")
          .append(addsOfSet).append("\naddsInclusionFromMap: ").append(addsInclusionFromMap)
          .append("\naddsInclusionFromMemo: ").append(addsInclusionFromMemo).append("\naddsInclusionFromSearch: ")
          .append(addsInclusionFromSearch).append("\naddsInclusionInterrupted: ").append(addsInclusionInterrupted)
          .append("\naddsExclusionWithoutSearch: ").append(addsExclusionWithoutSearch).append("\naddsExclusionWithSearch: ")
          .append(addsExclusionWithSearch).append("\nremovesOfAnySubType: ").append(removesOfAnySubType)
          .append("\nremovesFromMap: ").append(removesFromMap).append("\nremovesFromMemo: ").append(removesFromMemo)
          .append("\nremovesFromSearch: ").append(removesFromSearch).append("\nregistrationCalls: ")
          .append(registrationCalls).append("\ncatchableAsQueries: ").append(catchableAsQueries)
          .append("\ncatchableAsFromMap: ").append(catchableAsFromMap).append("\ncatchableAsFromSearch: ")
          .append(catchableAsFromSearch).append('\n');
      return buf.toString();
    }

    /**
     * A package-private method to provide unit tests with access to the collection of ThrowableSets.
     */
    Set<ThrowableSet> getThrowableSets() {
      return registry.keySet();
    }
  }

  public static class AlreadyHasExclusionsException extends IllegalStateException {
    private static final long serialVersionUID = 6785184160868722359L;

    public AlreadyHasExclusionsException(String s) {
      super(s);
    }
  }

  /**
   * The return type for {@link ThrowableSet#whichCatchableAs(RefType)}, consisting of a pair of ThrowableSets.
   */
  public static class Pair {
    private ThrowableSet caught;
    private ThrowableSet uncaught;

    /**
     * Constructs a <code>ThrowableSet.Pair</code>.
     *
     * @param caught
     *          The set of exceptions to be returned when {@link #getCaught()} is called on the constructed
     *          <code>ThrowableSet.Pair</code>.
     *
     * @param uncaught
     *          The set of exceptions to be returned when {@link #getUncaught()} is called on the constructed
     *          <code>ThrowableSet.Pair</code>.
     */
    protected Pair(ThrowableSet caught, ThrowableSet uncaught) {
      this.caught = caught;
      this.uncaught = uncaught;
    }

    /**
     * @return the set of caught exceptions.
     */
    public ThrowableSet getCaught() {
      return caught;
    }

    /**
     * @return the set of uncaught exceptions.
     */
    public ThrowableSet getUncaught() {
      return uncaught;
    }

    /**
     * Indicates whether two {@link Object}s are <code>ThrowableSet.Pair</code>s representing the same set of caught and
     * uncaught exception types.
     *
     * @param o
     *          the <code>Object</code> to compare to this <code>ThrowableSet.Pair</code>.
     *
     * @return <code>true</code> if <code>o</code> is a <code>ThrowableSet.Pair</code> representing the same set of caught
     *         and uncaught types as this <code>ThrowableSet.Pair</code>.
     */
    @Override
    public boolean equals(Object o) {
      if (o == this) {
        return true;
      }
      if (!(o instanceof Pair)) {
        return false;
      }
      Pair tsp = (Pair) o;
      if (this.caught.equals(tsp.caught) && this.uncaught.equals(tsp.uncaught)) {
        return true;
      }
      return false;
    }

    @Override
    public int hashCode() {
      int result = 31;
      result = (37 * result) + caught.hashCode();
      result = (37 * result) + uncaught.hashCode();
      return result;
    }
  }

  /**
   * Comparator used to implement sortedThrowableIterator().
   *
   */
  private static class ThrowableComparator<T extends RefLikeType> implements java.util.Comparator<T> {

    private static RefType baseType(RefLikeType o) {
      if (o instanceof AnySubType) {
        return ((AnySubType) o).getBase();
      } else {
        return (RefType) o; // ClassCastException if o is not a RefType.
      }
    }

    @Override
    public int compare(T o1, T o2) {
      RefType t1 = baseType(o1);
      RefType t2 = baseType(o2);
      if (t1.equals(t2)) {
        // There should never be both AnySubType(t) and
        // t in a ThrowableSet, but if it happens, put
        // AnySubType(t) first:
        if (o1 instanceof AnySubType) {
          if (o2 instanceof AnySubType) {
            return 0;
          } else {
            return -1;
          }
        } else if (o2 instanceof AnySubType) {
          return 1;
        } else {
          return 0;
        }
      } else {
        return t1.toString().compareTo(t2.toString());
      }
    }

  }
}
