From 58bc611e3a429ba7c9589b66cc9b6a5787a40c02 Mon Sep 17 00:00:00 2001
From: Alexander Udalov <Alexander.Udalov@jetbrains.com>
Date: Mon, 9 Jun 2014 21:24:27 +0400
Subject: [PATCH] Copy pcollections's HashPMap to kotlin/reflect/jvm/internal

It will be used for caching KClass instances for foreign (Java) classes
---
 .../jet/parsing/JetCodeConformanceTest.java   |   2 +
 .../jvm/internal/pcollections/ConsPStack.java | 210 ++++++++++++
 .../jvm/internal/pcollections/HashPMap.java   | 175 ++++++++++
 .../internal/pcollections/HashTreePMap.java   |  51 +++
 .../jvm/internal/pcollections/IntTree.java    | 309 ++++++++++++++++++
 .../internal/pcollections/IntTreePMap.java    | 163 +++++++++
 .../internal/pcollections/PCollection.java    |  47 +++
 .../jvm/internal/pcollections/PMap.java       |  45 +++
 .../jvm/internal/pcollections/PSequence.java  |  69 ++++
 .../jvm/internal/pcollections/PStack.java     |  53 +++
 .../pcollections/SimpleImmutableEntry.java    | 148 +++++++++
 license/third_party/pcollections_LICENSE.txt  |  19 ++
 12 files changed, 1291 insertions(+)
 create mode 100644 core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/ConsPStack.java
 create mode 100644 core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/HashPMap.java
 create mode 100644 core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/HashTreePMap.java
 create mode 100644 core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/IntTree.java
 create mode 100644 core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/IntTreePMap.java
 create mode 100644 core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PCollection.java
 create mode 100644 core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PMap.java
 create mode 100644 core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PSequence.java
 create mode 100644 core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PStack.java
 create mode 100644 core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/SimpleImmutableEntry.java
 create mode 100644 license/third_party/pcollections_LICENSE.txt

diff --git a/compiler/tests/org/jetbrains/jet/parsing/JetCodeConformanceTest.java b/compiler/tests/org/jetbrains/jet/parsing/JetCodeConformanceTest.java
index 7c092def797..534f6719e38 100644
--- a/compiler/tests/org/jetbrains/jet/parsing/JetCodeConformanceTest.java
+++ b/compiler/tests/org/jetbrains/jet/parsing/JetCodeConformanceTest.java
@@ -36,6 +36,8 @@ public class JetCodeConformanceTest extends TestCase {
     private static final Pattern SOURCES_FILE_PATTERN = Pattern.compile("(.+\\.java|.+\\.kt|.+\\.js)");
     private static final List<File> EXCLUDED_FILES_AND_DIRS = Arrays.asList(
             new File("android.tests.dependencies"),
+            new File("core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections"),
+            new File("libraries/tools/runtime/target/copied-sources"),
             new File("dependencies"),
             new File("examples"),
             new File("js/js.translator/qunit/qunit.js"),
diff --git a/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/ConsPStack.java b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/ConsPStack.java
new file mode 100644
index 00000000000..b529b6580c8
--- /dev/null
+++ b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/ConsPStack.java
@@ -0,0 +1,210 @@
+package kotlin.reflect.jvm.internal.pcollections;
+
+import java.util.AbstractSequentialList;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.ListIterator;
+
+
+
+/**
+ * 
+ * A simple persistent stack of non-null values.
+ * <p>
+ * This implementation is thread-safe (assuming Java's AbstractSequentialList is thread-safe),
+ * although its iterators may not be.
+ * 
+ * @author harold
+ *
+ * @param <E>
+ */
+public final class ConsPStack<E> extends AbstractSequentialList<E> implements PStack<E> {
+//// STATIC FACTORY METHODS ////
+	private static final ConsPStack<Object> EMPTY = new ConsPStack<Object>();
+	
+	/**
+	 * @param <E>
+	 * @return an empty stack
+	 */
+	@SuppressWarnings("unchecked")
+	public static <E> ConsPStack<E> empty() {
+		return (ConsPStack<E>)EMPTY; }
+	
+	/**
+	 * @param <E>
+	 * @param e
+	 * @return empty().plus(e)
+	 */
+	public static <E> ConsPStack<E> singleton(final E e) {
+		return ConsPStack.<E>empty().plus(e); }
+	
+	/**
+	 * @param <E>
+	 * @param list
+	 * @return a stack consisting of the elements of list in the order of list.iterator()
+	 */
+	@SuppressWarnings("unchecked")
+	public static <E> ConsPStack<E> from(final Collection<? extends E> list) {
+		if(list instanceof ConsPStack)
+			return (ConsPStack<E>)list; //(actually we only know it's ConsPStack<? extends E>)
+									// but that's good enough for an immutable
+									// (i.e. we can't mess someone else up by adding the wrong type to it)
+		return from(list.iterator());
+	}
+	
+	private static <E> ConsPStack<E> from(final Iterator<? extends E> i) {
+		if(!i.hasNext()) return empty();
+		E e = i.next();
+		return from(i).plus(e);
+	}
+
+	
+//// PRIVATE CONSTRUCTORS ////
+	private final E first; private final ConsPStack<E> rest;
+	private final int size;
+	// not externally instantiable (or subclassable):
+	private ConsPStack() { // EMPTY constructor
+		if(EMPTY!=null)
+			throw new RuntimeException("empty constructor should only be used once");
+		size = 0; first=null; rest=null;
+	}
+	private ConsPStack(final E first, final ConsPStack<E> rest) {
+		this.first = first; this.rest = rest;
+		
+		size = 1 + rest.size;
+	}
+	
+	
+//// REQUIRED METHODS FROM AbstractSequentialList ////
+	@Override
+	public int size() {
+		return size; }
+	
+	@Override
+	public ListIterator<E> listIterator(final int index) {
+		if(index<0 || index>size) throw new IndexOutOfBoundsException();
+		
+		return new ListIterator<E>() {
+			int i = index;
+			ConsPStack<E> next = subList(index);
+
+			public boolean hasNext() {
+				return next.size>0; }
+			public boolean hasPrevious() {
+				return i>0; }
+			public int nextIndex() {
+				return index; }
+			public int previousIndex() {
+				return index-1; }
+			public E next() {
+				E e = next.first;
+				next = next.rest;
+				return e;
+			}
+			public E previous() {
+				System.err.println("ConsPStack.listIterator().previous() is inefficient, don't use it!");
+				next = subList(index-1); // go from beginning...
+				return next.first;
+			}
+
+			public void add(final E o) {
+				throw new UnsupportedOperationException(); }
+			public void remove() {
+				throw new UnsupportedOperationException(); }
+			public void set(final E o) {
+				throw new UnsupportedOperationException(); }
+		};
+	}
+
+
+//// OVERRIDDEN METHODS FROM AbstractSequentialList ////
+	@Override
+	public ConsPStack<E> subList(final int start, final int end) {
+		if(start<0 || end>size || start>end)
+			throw new IndexOutOfBoundsException();
+		if(end==size) // want a substack
+			return subList(start); // this is faster
+		if(start==end) // want nothing
+			return empty();
+		if(start==0) // want the current element
+			return new ConsPStack<E>(first, rest.subList(0, end-1));
+		// otherwise, don't want the current element:
+		return rest.subList(start-1, end-1);
+	}
+	
+	
+//// IMPLEMENTED METHODS OF PStack ////
+	public ConsPStack<E> plus(final E e) {
+		return new ConsPStack<E>(e, this);
+	}
+	
+	public ConsPStack<E> plusAll(final Collection<? extends E> list) {
+		ConsPStack<E> result = this;
+		for(E e : list)
+			result = result.plus(e);
+		return result;
+	}
+
+	public ConsPStack<E> plus(final int i, final E e) {
+		if(i<0 || i>size)
+			throw new IndexOutOfBoundsException();
+		if(i==0) // insert at beginning
+			return plus(e);
+		return new ConsPStack<E>(first, rest.plus(i-1, e));
+	}
+
+	public ConsPStack<E> plusAll(final int i, final Collection<? extends E> list) {
+		// TODO inefficient if list.isEmpty()
+		if(i<0 || i>size)
+			throw new IndexOutOfBoundsException();
+		if(i==0)
+			return plusAll(list);
+		return new ConsPStack<E>(first, rest.plusAll(i-1, list));
+	}
+	
+	public ConsPStack<E> minus(final Object e) {
+		if(size==0)
+			return this;
+		if(first.equals(e)) // found it
+			return rest; // don't recurse (only remove one)
+		// otherwise keep looking:
+		ConsPStack<E> newRest = rest.minus(e);
+		if(newRest==rest) return this;
+		return new ConsPStack<E>(first, newRest);
+	}
+
+	public ConsPStack<E> minus(final int i) {
+		return minus(get(i));
+	}
+
+	public ConsPStack<E> minusAll(final Collection<?> list) {
+		if(size==0)
+			return this;
+		if(list.contains(first)) // get rid of current element
+			return rest.minusAll(list); // recursively delete all
+		// either way keep looking:
+		ConsPStack<E> newRest = rest.minusAll(list);
+		if(newRest==rest) return this;
+		return new ConsPStack<E>(first, newRest);
+	}
+	
+	public ConsPStack<E> with(final int i, final E e) {
+		if(i<0 || i>=size)
+			throw new IndexOutOfBoundsException();
+		if(i==0) {
+			if(first.equals(e)) return this;
+			return new ConsPStack<E>(e, rest);
+		}
+		ConsPStack<E> newRest = rest.with(i-1, e);
+		if(newRest==rest) return this;
+		return new ConsPStack<E>(first, newRest);
+	}
+
+	public ConsPStack<E> subList(final int start) {
+		if(start<0 || start>size)
+			throw new IndexOutOfBoundsException();
+		if(start==0)
+			return this;
+		return rest.subList(start-1);
+	}
+}
diff --git a/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/HashPMap.java b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/HashPMap.java
new file mode 100644
index 00000000000..f2c777c364b
--- /dev/null
+++ b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/HashPMap.java
@@ -0,0 +1,175 @@
+package kotlin.reflect.jvm.internal.pcollections;
+
+import java.util.AbstractMap;
+import java.util.AbstractSet;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Set;
+
+
+
+
+/**
+ * 
+ * A persistent map from non-null keys to non-null values.
+ * <p>
+ * This map uses a given integer map to map hashcodes to lists of elements
+ * with the same hashcode. Thus if all elements have the same hashcode, performance
+ * is reduced to that of an association list.
+ * <p>
+ * This implementation is thread-safe (assuming Java's AbstractMap and AbstractSet are thread-safe),
+ * although its iterators may not be.
+ * 
+ * @author harold
+ *
+ * @param <K>
+ * @param <V>
+ */
+public final class HashPMap<K,V> extends AbstractMap<K,V> implements PMap<K,V> {
+//// STATIC FACTORY METHODS ////
+	/**
+	 * @param <K>
+	 * @param <V>
+	 * @param intMap
+	 * @return a map backed by an empty version of intMap,
+	 * 	i.e. backed by intMap.minusAll(intMap.keySet())
+	 */
+	public static <K,V> HashPMap<K,V> empty(final PMap<Integer,PSequence<Entry<K,V>>> intMap) {
+		return new HashPMap<K,V>(intMap.minusAll(intMap.keySet()), 0); }
+	
+
+//// PRIVATE CONSTRUCTORS ////
+	private final PMap<Integer,PSequence<Entry<K,V>>> intMap;
+	private final int size;
+	// not externally instantiable (or subclassable):
+	private HashPMap(final PMap<Integer,PSequence<Entry<K,V>>> intMap, final int size) {
+		this.intMap = intMap; this.size = size; }
+
+	
+//// REQUIRED METHODS FROM AbstractMap ////
+	// this cache variable is thread-safe since assignment in Java is atomic:
+	private Set<Entry<K,V>> entrySet = null;
+	@Override
+	public Set<Entry<K,V>> entrySet() {
+		if(entrySet==null)
+			entrySet = new AbstractSet<Entry<K,V>>() {
+				// REQUIRED METHODS OF AbstractSet // 
+				@Override
+				public int size() {
+					return size; }		
+				@Override
+				public Iterator<Entry<K,V>> iterator() {
+					return new SequenceIterator<Entry<K,V>>(intMap.values().iterator()); }
+				// OVERRIDDEN METHODS OF AbstractSet //
+				@Override
+				public boolean contains(final Object e) {
+					if(!(e instanceof Entry))
+						return false;
+					V value = get(((Entry<?,?>)e).getKey());
+					return value!=null && value.equals(((Entry<?,?>)e).getValue());
+				}
+			};
+		return entrySet;
+	}
+
+	
+//// OVERRIDDEN METHODS FROM AbstractMap ////
+	@Override
+	public int size() {
+		return size; }
+
+	@Override
+	public boolean containsKey(final Object key) {
+		return keyIndexIn(getEntries(key.hashCode()), key) != -1; }
+	
+	@Override
+	public V get(final Object key) {
+		PSequence<Entry<K,V>> entries = getEntries(key.hashCode());
+		for(Entry<K,V> entry : entries)
+			if(entry.getKey().equals(key))
+				return entry.getValue();
+		return null;
+	}
+
+	
+//// IMPLEMENTED METHODS OF PMap////
+	public HashPMap<K,V> plusAll(final Map<? extends K, ? extends V> map) {
+		HashPMap<K,V> result = this;
+		for(Entry<? extends K,? extends V> entry : map.entrySet())
+			result = result.plus(entry.getKey(), entry.getValue());
+		return result;
+	}
+
+	public HashPMap<K,V> minusAll(final Collection<?> keys) {
+		HashPMap<K,V> result = this;
+		for(Object key : keys)
+			result = result.minus(key);
+		return result;
+	}
+	
+	public HashPMap<K,V> plus(final K key, final V value) {
+		PSequence<Entry<K,V>> entries = getEntries(key.hashCode());
+		int size0 = entries.size(),
+			i = keyIndexIn(entries, key);
+		if(i!=-1) entries = entries.minus(i);
+		entries = entries.plus(new SimpleImmutableEntry<K,V>(key, value));
+		return new HashPMap<K,V>(intMap.plus(key.hashCode(), entries),
+				size-size0+entries.size());
+	}
+
+	public HashPMap<K,V> minus(final Object key) {
+		PSequence<Entry<K,V>> entries = getEntries(key.hashCode());
+		int i = keyIndexIn(entries, key);
+		if(i==-1) // key not in this
+			return this;
+		entries = entries.minus(i);
+		if(entries.size()==0) // get rid of the entire hash entry
+			return new HashPMap<K,V>(intMap.minus(key.hashCode()),
+					size-1);
+		// otherwise replace hash entry with new smaller one:
+		return new HashPMap<K,V>(intMap.plus(key.hashCode(), entries),
+				size-1);
+	}
+	
+	
+//// PRIVATE UTILITIES ////
+	private PSequence<Entry<K,V>> getEntries(final int hash) {
+		PSequence<Entry<K,V>> entries = intMap.get(hash);
+		if(entries==null) return ConsPStack.empty();
+		return entries;
+	}
+
+	
+//// PRIVATE STATIC UTILITIES ////
+	private static <K,V> int keyIndexIn(final PSequence<Entry<K,V>> entries, final Object key) {
+		int i=0;
+		for(Entry<K,V> entry : entries) {
+			if(entry.getKey().equals(key))
+				return i;
+			i++;
+		}
+		return -1;
+	}
+	
+	static class SequenceIterator<E> implements Iterator<E> {
+		private final Iterator<PSequence<E>> i;
+		private PSequence<E> seq = ConsPStack.empty();
+		SequenceIterator(Iterator<PSequence<E>> i) {
+			this.i = i; }
+
+		public boolean hasNext() {
+			return seq.size()>0 || i.hasNext(); }
+
+		public E next() {
+			if(seq.size()==0)
+				seq = i.next();
+			final E result = seq.get(0);
+			seq = seq.subList(1, seq.size());
+			return result;
+		}
+
+		public void remove() {
+			throw new UnsupportedOperationException(); }
+	}
+}
diff --git a/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/HashTreePMap.java b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/HashTreePMap.java
new file mode 100644
index 00000000000..46b3ab9c195
--- /dev/null
+++ b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/HashTreePMap.java
@@ -0,0 +1,51 @@
+package kotlin.reflect.jvm.internal.pcollections;
+
+import java.util.Map;
+import java.util.Map.Entry;
+
+
+
+
+/**
+ *
+ * A static convenience class for creating efficient persistent maps.
+ * <p>
+ * This class simply creates HashPMaps backed by IntTreePMaps.
+ * 
+ * @author harold
+ */
+public final class HashTreePMap {
+	// not instantiable (or subclassable):
+	private HashTreePMap() {}
+	
+	private static final HashPMap<Object,Object> EMPTY
+		= HashPMap.empty(IntTreePMap.<PSequence<Entry<Object,Object>>>empty());
+
+	/**
+	 * @param <K>
+	 * @param <V>
+	 * @return an empty map
+	 */
+	@SuppressWarnings("unchecked")
+	public static <K,V> HashPMap<K,V> empty() {
+		return (HashPMap<K,V>)EMPTY; }
+	
+	/**
+	 * @param <K>
+	 * @param <V>
+	 * @param key
+	 * @param value
+	 * @return empty().plus(key, value)
+	 */
+	public static <K,V> HashPMap<K,V> singleton(final K key, final V value) {
+		return HashTreePMap.<K,V>empty().plus(key, value); }
+	
+	/**
+	 * @param <K>
+	 * @param <V>
+	 * @param map
+	 * @return empty().plusAll(map)
+	 */
+	public static <K,V> HashPMap<K,V> from(final Map<? extends K, ? extends V> map) {
+		return HashTreePMap.<K,V>empty().plusAll(map); }
+}
diff --git a/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/IntTree.java b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/IntTree.java
new file mode 100644
index 00000000000..d5a1ea7b2bb
--- /dev/null
+++ b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/IntTree.java
@@ -0,0 +1,309 @@
+package kotlin.reflect.jvm.internal.pcollections;
+
+import java.util.Iterator;
+import java.util.Map.Entry;
+
+
+
+
+/**
+ * 
+ * A non-public utility class for persistent balanced tree maps with integer keys.
+ * <p>
+ * To allow for efficiently increasing all keys above a certain value or decreasing
+ * all keys below a certain value, the keys values are stored relative to their parent.
+ * This makes this map a good backing for fast insertion and removal of indices in a
+ * vector.
+ * <p>
+ * This implementation is thread-safe except for its iterators.
+ * <p>
+ * Other than that, this tree is based on the Glasgow Haskell Compiler's Data.Map implementation,
+ * which in turn is based on "size balanced binary trees" as described by:
+ * <p>
+ * Stephen Adams, "Efficient sets: a balancing act",
+ * Journal of Functional Programming 3(4):553-562, October 1993,
+ * http://www.swiss.ai.mit.edu/~adams/BB/.
+ * <p>
+ * J. Nievergelt and E.M. Reingold, "Binary search trees of bounded balance",
+ * SIAM journal of computing 2(1), March 1973.
+ * 
+ * @author harold
+ *
+ * @param <V>
+ */
+class IntTree<V> {
+	// marker value:
+	static final IntTree<Object> EMPTYNODE = new IntTree<Object>();
+	
+	private final long key; // we use longs so relative keys can express all ints
+		// (e.g. if this has key -10 and right has 'absolute' key MAXINT,
+		// then its relative key is MAXINT+10 which overflows)
+		// there might be some way to deal with this based on left-verse-right logic,
+		// but that sounds like a mess.
+	private final V value; // null value means this is empty node
+	private final IntTree<V> left, right;
+	private final int size;
+	private IntTree() {
+		if(EMPTYNODE!=null)
+			throw new RuntimeException("empty constructor should only be used once");
+		size = 0;
+		
+		key=0; value=null; left=null; right=null;
+	}
+	private IntTree(final long key, final V value, final IntTree<V> left, final IntTree<V> right) {
+		this.key = key; this.value = value;
+		this.left = left; this.right = right;
+		size = 1 + left.size + right.size;
+	}
+	
+	private IntTree<V> withKey(final long newKey) {
+		if(size==0 || newKey==key) return this;
+		return new IntTree<V>(newKey, value, left, right); }
+	
+	Iterator<Entry<Integer,V>> iterator() {
+		return new EntryIterator<V>(this); }
+	
+	int size() {
+		return size; }
+
+	boolean containsKey(final long key) {
+		if(size==0)
+			return false;
+		if(key < this.key)
+			return left.containsKey(key-this.key);
+		if(key > this.key)
+			return right.containsKey(key-this.key);
+		// otherwise key==this.key:
+		return true;
+	}
+	
+	V get(final long key) {
+		if(size==0)
+			return null;
+		if(key < this.key)
+			return left.get(key-this.key);
+		if(key > this.key)
+			return right.get(key-this.key);
+		// otherwise key==this.key:
+		return value;
+	}
+
+	IntTree<V> plus(final long key, final V value) {
+		if(size==0)
+			return new IntTree<V>(key, value, this, this);
+		if(key < this.key)
+			return rebalanced(left.plus(key-this.key, value), right);
+		if(key > this.key)
+			return rebalanced(left, right.plus(key-this.key, value));
+		// otherwise key==this.key, so we simply replace this, with no effect on balance:
+		if(value==this.value)
+			return this;
+		return new IntTree<V>(key, value, left, right);
+	}
+
+	IntTree<V> minus(final long key) {
+		if(size==0)
+			return this;
+		if(key < this.key)
+			return rebalanced(left.minus(key-this.key), right);
+		if(key > this.key)
+			return rebalanced(left, right.minus(key-this.key));
+
+		// otherwise key==this.key, so we are killing this node:
+
+		if(left.size==0) // we can just become right node
+			// make key 'absolute':
+			return right.withKey(right.key+this.key);
+		if(right.size==0) // we can just become left node
+			return left.withKey(left.key+this.key);
+
+		// otherwise replace this with the next key (i.e. the smallest key to the right):
+		
+		// TODO have minNode() instead of minKey to avoid having to call get()
+		// TODO get node from larger subtree, i.e. if left.size>right.size use left.maxNode()
+		// TODO have faster minusMin() instead of just using minus()
+		
+		long newKey = right.minKey() + this.key;
+			//(right.minKey() is relative to this; adding this.key makes it 'absolute'
+			//	where 'absolute' really means relative to the parent of this)
+
+		V newValue = right.get(newKey-this.key);
+		// now that we've got the new stuff, take it out of the right subtree:
+		IntTree<V> newRight = right.minus(newKey-this.key);
+
+		// lastly, make the subtree keys relative to newKey (currently they are relative to this.key):
+		newRight = newRight.withKey( (newRight.key+this.key) - newKey );
+		// left is definitely not empty:
+		IntTree<V> newLeft = left.withKey( (left.key+this.key) - newKey );
+		
+		return rebalanced(newKey, newValue, newLeft, newRight);
+	}
+	
+	/**
+	 * Changes every key k>=key to k+delta.
+	 * 
+	 * This method will create an _invalid_ tree if delta<0
+	 * and the distance between the smallest k>=key in this
+	 * and the largest j<key in this is |delta| or less.
+	 * 
+	 * In other words, this method must not result in any change
+	 * in the order of the keys in this, since the tree structure is
+	 * not being changed at all.
+	 */
+	IntTree<V> changeKeysAbove(final long key, final int delta) {
+		if(size==0 || delta==0)
+			return this;
+
+		if(this.key>=key)
+			// adding delta to this.key changes the keys of _all_ children of this,
+			// so we now need to un-change the children of this smaller than key,
+			// all of which are to the left. note that we still use the 'old' relative key...:
+			return new IntTree<V>(this.key+delta, value, left.changeKeysBelow(key-this.key, -delta), right);
+
+		// otherwise, doesn't apply yet, look to the right:
+		IntTree<V> newRight = right.changeKeysAbove(key-this.key, delta);
+		if(newRight==right) return this;
+		return new IntTree<V>(this.key, value, left, newRight);
+	}
+	
+	/**
+	 * Changes every key k<key to k+delta.
+	 * 
+	 * This method will create an _invalid_ tree if delta>0
+	 * and the distance between the largest k<key in this
+	 * and the smallest j>=key in this is delta or less.
+	 * 
+	 * In other words, this method must not result in any overlap or change
+	 * in the order of the keys in this, since the tree _structure_ is
+	 * not being changed at all.
+	 */
+	IntTree<V> changeKeysBelow(final long key, final int delta) {
+		if(size==0 || delta==0)
+			return this;
+
+		if(this.key<key)
+			// adding delta to this.key changes the keys of _all_ children of this,
+			// so we now need to un-change the children of this larger than key,
+			// all of which are to the right. note that we still use the 'old' relative key...:
+			return new IntTree<V>(this.key+delta, value, left, right.changeKeysAbove(key-this.key, -delta));
+
+		// otherwise, doesn't apply yet, look to the left:
+		IntTree<V> newLeft = left.changeKeysBelow(key-this.key, delta);
+		if(newLeft==left) return this;
+		return new IntTree<V>(this.key, value, newLeft, right);
+	}
+	
+	// min key in this:
+	private long minKey() {
+		if(left.size==0)
+			return key;
+		// make key 'absolute' (i.e. relative to the parent of this):
+		return left.minKey() + this.key;
+	}
+
+	private IntTree<V> rebalanced(final IntTree<V> newLeft, final IntTree<V> newRight) {
+		if(newLeft==left && newRight==right)
+			return this; // already balanced
+		return rebalanced(key, value, newLeft, newRight);
+	}
+
+	private static final int OMEGA = 5;
+	private static final int ALPHA = 2;
+	// rebalance a tree that is off-balance by at most 1:
+	private static <V> IntTree<V> rebalanced(final long key, final V value,
+			final IntTree<V> left, final IntTree<V> right) {
+		if(left.size + right.size > 1) {
+			if(left.size >= OMEGA*right.size) { // rotate to the right
+				IntTree<V> ll = left.left, lr = left.right;
+				if(lr.size < ALPHA*ll.size) // single rotation
+					return new IntTree<V>(left.key+key, left.value,
+							ll,
+							new IntTree<V>(-left.key, value,
+									lr.withKey(lr.key+left.key),
+									right));
+				else { // double rotation:
+					IntTree<V> lrl = lr.left, lrr = lr.right;
+					return new IntTree<V>(lr.key+left.key+key, lr.value,
+							new IntTree<V>(-lr.key, left.value,
+									ll,
+									lrl.withKey(lrl.key+lr.key)),
+							new IntTree<V>(-left.key-lr.key, value,
+									lrr.withKey(lrr.key+lr.key+left.key),
+									right));
+				}
+			}
+			else if(right.size >= OMEGA*left.size) { // rotate to the left
+				IntTree<V> rl = right.left, rr = right.right;
+				if(rl.size < ALPHA*rr.size) // single rotation
+					return new IntTree<V>(right.key+key, right.value,
+							new IntTree<V>(-right.key, value,
+									left,
+									rl.withKey(rl.key+right.key)),
+							rr);
+				else { // double rotation:
+					IntTree<V> rll = rl.left, rlr = rl.right;
+					return new IntTree<V>(rl.key+right.key+key, rl.value,
+							new IntTree<V>(-right.key-rl.key, value,
+									left,
+									rll.withKey(rll.key+rl.key+right.key)),
+							new IntTree<V>(-rl.key, right.value,
+									rlr.withKey(rlr.key+rl.key),
+									rr));
+				}
+			}
+		}
+		// otherwise already balanced enough:
+		return new IntTree<V>(key, value, left, right);
+	}
+
+	
+////entrySet().iterator() IMPLEMENTATION ////	
+	// TODO make this a ListIterator?
+	private static final class EntryIterator<V> implements Iterator<Entry<Integer,V>> {
+		private PStack<IntTree<V>> stack = ConsPStack.empty(); //path of nonempty nodes
+		private int key = 0; // note we use _int_ here since this is a truly absolute key
+		
+		EntryIterator(final IntTree<V> root) {
+			gotoMinOf(root); }
+		
+		public boolean hasNext() {
+			return stack.size()>0; }
+		
+		public Entry<Integer,V> next() {
+			IntTree<V> node = stack.get(0);
+			final Entry<Integer,V> result = new SimpleImmutableEntry<Integer,V>(key, node.value);
+			
+			// find next node.
+			// we've already done everything smaller,
+			// so try least larger node:
+			
+			if(node.right.size>0) // we can descend to the right
+				gotoMinOf(node.right);
+			
+			else // can't descend to the right -- try ascending to the right
+				while (true) { // find current node's least larger ancestor, if any
+					key -= node.key; // revert to parent's key
+					stack = stack.subList(1); // climb up to parent
+					// if parent was larger than child or there was no parent, we're done:
+					if(node.key<0 || stack.size()==0)
+						break;
+					// otherwise parent was smaller -- try its parent:
+					node = stack.get(0);
+				}
+			
+			return result;
+		}
+
+		public void remove() {
+			throw new UnsupportedOperationException(); }
+
+		// extend the stack to its least non-empty node:
+		private void gotoMinOf(IntTree<V> node) {
+			while(node.size>0) {
+				stack = stack.plus(node);
+				key += node.key;
+				node = node.left;
+			}
+		}
+	}
+}
diff --git a/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/IntTreePMap.java b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/IntTreePMap.java
new file mode 100644
index 00000000000..4c144faf378
--- /dev/null
+++ b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/IntTreePMap.java
@@ -0,0 +1,163 @@
+package kotlin.reflect.jvm.internal.pcollections;
+
+import java.util.AbstractMap;
+import java.util.AbstractSet;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Set;
+
+
+
+
+/**
+ * 
+ * An efficient persistent map from integer keys to non-null values.
+ * <p>
+ * Iteration occurs in the integer order of the keys.
+ * <p>
+ * This implementation is thread-safe (assuming Java's AbstractMap and AbstractSet are thread-safe),
+ * although its iterators may not be.
+ * <p>
+ * The balanced tree is based on the Glasgow Haskell Compiler's Data.Map implementation,
+ * which in turn is based on "size balanced binary trees" as described by:
+ * <p>
+ * Stephen Adams, "Efficient sets: a balancing act",
+ * Journal of Functional Programming 3(4):553-562, October 1993,
+ * http://www.swiss.ai.mit.edu/~adams/BB/.
+ * <p>
+ * J. Nievergelt and E.M. Reingold, "Binary search trees of bounded balance",
+ * SIAM journal of computing 2(1), March 1973.
+ * 
+ * @author harold
+ *
+ * @param <V>
+ */
+public final class IntTreePMap<V> extends AbstractMap<Integer,V> implements PMap<Integer,V> {
+//// STATIC FACTORY METHODS ////
+	private static final IntTreePMap<Object> EMPTY = new IntTreePMap<Object>(IntTree.EMPTYNODE);
+
+	/**
+	 * @param <V>
+	 * @return an empty map
+	 */
+	@SuppressWarnings("unchecked")
+	public static <V> IntTreePMap<V> empty() {
+		return (IntTreePMap<V>)EMPTY; }
+	
+	/**
+	 * @param <V>
+	 * @param key
+	 * @param value
+	 * @return empty().plus(key, value)
+	 */
+	public static <V> IntTreePMap<V> singleton(final Integer key, final V value) {
+		return IntTreePMap.<V>empty().plus(key, value); }
+	
+	/**
+	 * @param <V>
+	 * @param map
+	 * @return empty().plusAll(map)
+	 */
+	@SuppressWarnings("unchecked")
+	public static <V> IntTreePMap<V> from(final Map<? extends Integer, ? extends V> map) {
+		if(map instanceof IntTreePMap)
+			return (IntTreePMap<V>)map; //(actually we only know it's IntTreePMap<? extends V>)
+									// but that's good enough for an immutable
+									// (i.e. we can't mess someone else up by adding the wrong type to it)
+		return IntTreePMap.<V>empty().plusAll(map); }
+	
+
+//// PRIVATE CONSTRUCTORS ////
+	private final IntTree<V> root;
+	// not externally instantiable (or subclassable):
+	private IntTreePMap(final IntTree<V> root) {
+		this.root = root; }
+	private IntTreePMap<V> withRoot(final IntTree<V> root) {
+		if(root==this.root) return this;
+		return new IntTreePMap<V>(root); }
+	
+
+//// UNINHERITED METHODS OF IntTreePMap ////
+	IntTreePMap<V> withKeysChangedAbove(final int key, final int delta) {
+		// TODO check preconditions of changeKeysAbove()
+		// TODO make public?
+		return withRoot( root.changeKeysAbove(key, delta) );
+	}
+	
+	IntTreePMap<V> withKeysChangedBelow(final int key, final int delta) {
+		// TODO check preconditions of changeKeysAbove()
+		// TODO make public?
+		return withRoot( root.changeKeysBelow(key, delta) );
+	}
+	
+//// REQUIRED METHODS FROM AbstractMap ////
+	// this cache variable is thread-safe, since assignment in Java is atomic:
+	private Set<Entry<Integer,V>> entrySet = null;
+	@Override
+	public Set<Entry<Integer,V>> entrySet() {
+		if(entrySet==null)
+			entrySet = new AbstractSet<Entry<Integer,V>>() {
+				// REQUIRED METHODS OF AbstractSet // 
+				@Override
+				public int size() { // same as Map
+					return IntTreePMap.this.size(); }
+				@Override
+				public Iterator<Entry<Integer,V>> iterator() {
+					return root.iterator(); }
+				// OVERRIDDEN METHODS OF AbstractSet //
+				@Override
+				public boolean contains(final Object e) {
+					if(!(e instanceof Entry))
+						return false;
+					V value = get(((Entry<?,?>)e).getKey());
+					return value!=null && value.equals(((Entry<?,?>)e).getValue());
+				}
+			};
+		return entrySet;
+	}
+
+	
+//// OVERRIDDEN METHODS FROM AbstractMap ////
+	@Override
+	public int size() {
+		return root.size(); }
+
+	@Override
+	public boolean containsKey(final Object key) {
+		if(!(key instanceof Integer))
+			return false;
+		return root.containsKey((Integer)key);
+	}
+	
+	@Override
+	public V get(final Object key) {
+		if(!(key instanceof Integer))
+			return null;
+		return root.get((Integer)key);
+	}
+
+	
+//// IMPLEMENTED METHODS OF PMap////
+	public IntTreePMap<V> plus(final Integer key, final V value) {
+		return withRoot( root.plus(key, value) ); }
+	
+	public IntTreePMap<V> minus(final Object key) {
+		if(!(key instanceof Integer)) return this;
+		return withRoot( root.minus((Integer)key) ); }
+	
+	public IntTreePMap<V> plusAll(final Map<? extends Integer, ? extends V> map) {
+		IntTree<V> root = this.root;
+		for(Entry<? extends Integer,? extends V> entry : map.entrySet())
+			root = root.plus(entry.getKey(), entry.getValue());
+		return withRoot(root);
+	}
+
+	public IntTreePMap<V> minusAll(final Collection<?> keys) {
+		IntTree<V> root = this.root;
+		for(Object key : keys)
+			if(key instanceof Integer)
+				root = root.minus((Integer)key);
+		return withRoot(root);
+	}
+}
diff --git a/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PCollection.java b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PCollection.java
new file mode 100644
index 00000000000..333acc4ca15
--- /dev/null
+++ b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PCollection.java
@@ -0,0 +1,47 @@
+package kotlin.reflect.jvm.internal.pcollections;
+
+import java.util.Collection;
+
+/**
+ * 
+ * An immutable, persistent collection of non-null elements of type E.
+ * 
+ * @author harold
+ *
+ * @param <E>
+ */
+public interface PCollection<E> extends Collection<E> {
+	
+	/**
+	 * @param e non-null
+	 * @return a collection which contains e and all of the elements of this
+	 */
+	public PCollection<E> plus(E e);
+
+	/**
+	 * @param list contains no null elements
+	 * @return a collection which contains all of the elements of list and this
+	 */
+	public PCollection<E> plusAll(Collection<? extends E> list);
+	
+	/**
+	 * @param e
+	 * @return this with a single instance of e removed, if e is in this
+	 */
+	public PCollection<E> minus(Object e);
+	
+	/**
+	 * @param list
+	 * @return this with all elements of list completely removed
+	 */
+	public PCollection<E> minusAll(Collection<?> list);
+	
+	// TODO public PCollection<E> retainingAll(Collection<?> list);
+	
+	@Deprecated boolean add(E o);
+	@Deprecated boolean remove(Object o);
+	@Deprecated boolean addAll(Collection<? extends E> c);
+	@Deprecated boolean removeAll(Collection<?> c);
+	@Deprecated boolean retainAll(Collection<?> c);
+	@Deprecated void clear();
+}
diff --git a/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PMap.java b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PMap.java
new file mode 100644
index 00000000000..bdfd4f54896
--- /dev/null
+++ b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PMap.java
@@ -0,0 +1,45 @@
+package kotlin.reflect.jvm.internal.pcollections;
+
+import java.util.Collection;
+import java.util.Map;
+
+/**
+ * 
+ * An immutable, persistent map from non-null keys of type K to non-null values of type V.
+ * 
+ * @author harold
+ *
+ * @param <K>
+ * @param <V>
+ */
+public interface PMap<K,V> extends Map<K,V> {
+	/**
+	 * @param key non-null
+	 * @param value non-null
+	 * @return a map with the mappings of this but with key mapped to value
+	 */
+	public PMap<K,V> plus(K key, V value);
+	
+	/**
+	 * @param map
+	 * @return this combined with map, with map's mappings used for any keys in both map and this
+	 */
+	public PMap<K,V> plusAll(Map<? extends K, ? extends V> map);
+	
+	/**
+	 * @param key
+	 * @return a map with the mappings of this but with no value for key
+	 */
+	public PMap<K,V> minus(Object key);
+	
+	/**
+	 * @param keys
+	 * @return a map with the mappings of this but with no value for any element of keys
+	 */
+	public PMap<K,V> minusAll(Collection<?> keys);
+	
+	@Deprecated V put(K k, V v);
+	@Deprecated V remove(Object k);
+	@Deprecated void putAll(Map<? extends K, ? extends V> m);
+	@Deprecated void clear();
+}
diff --git a/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PSequence.java b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PSequence.java
new file mode 100644
index 00000000000..3be82dcec0f
--- /dev/null
+++ b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PSequence.java
@@ -0,0 +1,69 @@
+package kotlin.reflect.jvm.internal.pcollections;
+
+import java.util.Collection;
+import java.util.List;
+
+/**
+ * 
+ * An immutable, persistent indexed collection.
+ * 
+ * @author harold
+ *
+ * @param <E>
+ */
+public interface PSequence<E> extends PCollection<E>, List<E> {
+	
+	//@Override
+	public PSequence<E> plus(E e);
+	
+	//@Override
+	public PSequence<E> plusAll(Collection<? extends E> list);
+	
+	/**
+	 * @param i
+	 * @param e
+	 * @return a sequence consisting of the elements of this with e replacing the element at index i.
+	 * @throws IndexOutOfBOundsException if i&lt;0 || i&gt;=this.size()
+	 */
+	public PSequence<E> with(int i, E e);
+	
+	/**
+	 * @param i
+	 * @param e non-null
+	 * @return a sequence consisting of the elements of this with e inserted at index i.
+	 * @throws IndexOutOfBOundsException if i&lt;0 || i&gt;this.size()
+	 */
+	public PSequence<E> plus(int i, E e);
+	
+	/**
+	 * @param i
+	 * @param list
+	 * @return a sequence consisting of the elements of this with list inserted at index i.
+	 * @throws IndexOutOfBOundsException if i&lt;0 || i&gt;this.size()
+	 */
+	public PSequence<E> plusAll(int i, Collection<? extends E> list);
+	
+	/**
+	 * Returns a sequence consisting of the elements of this without the first occurrence of e.
+	 */
+	//@Override
+	public PSequence<E> minus(Object e);
+	
+	//@Override
+	public PSequence<E> minusAll(Collection<?> list);
+	
+	/**
+	 * @param i
+	 * @return a sequence consisting of the elements of this with the element at index i removed.
+	 * @throws IndexOutOfBOundsException if i&lt;0 || i&gt;=this.size()
+	 */
+	public PSequence<E> minus(int i);
+
+	//@Override
+	public PSequence<E> subList(int start, int end);
+	
+	@Deprecated boolean addAll(int index, Collection<? extends E> c);
+	@Deprecated E set(int index, E element);
+	@Deprecated void add(int index, E element);
+	@Deprecated E remove(int index);
+}
diff --git a/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PStack.java b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PStack.java
new file mode 100644
index 00000000000..ca68a69360e
--- /dev/null
+++ b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/PStack.java
@@ -0,0 +1,53 @@
+package kotlin.reflect.jvm.internal.pcollections;
+
+import java.util.Collection;
+
+/**
+ * 
+ * An immutable, persistent stack.
+ * 
+ * @author harold
+ *
+ * @param <E>
+ */
+public interface PStack<E> extends PSequence<E> {
+	
+	/**
+	 * Returns a stack consisting of the elements of this with e prepended.
+	 */
+	//@Override
+	public PStack<E> plus(E e);
+	
+	/**
+	 * Returns a stack consisting of the elements of this with list prepended in reverse.
+	 */
+	//@Override
+	public PStack<E> plusAll(Collection<? extends E> list);
+	
+	//@Override
+	public PStack<E> with(int i, E e);
+	
+	//@Override
+	public PStack<E> plus(int i, E e);
+	
+	//@Override
+	public PStack<E> plusAll(int i, Collection<? extends E> list);
+	
+	//@Override
+	public PStack<E> minus(Object e);
+	
+	//@Override
+	public PStack<E> minusAll(Collection<?> list);
+
+	//@Override
+	public PStack<E> minus(int i);
+
+	//@Override
+	public PStack<E> subList(int start, int end);
+	
+	/**
+	 * @param start
+	 * @return subList(start,this.size())
+	 */
+	public PStack<E> subList(int start);
+}
diff --git a/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/SimpleImmutableEntry.java b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/SimpleImmutableEntry.java
new file mode 100644
index 00000000000..71452649e25
--- /dev/null
+++ b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/pcollections/SimpleImmutableEntry.java
@@ -0,0 +1,148 @@
+package kotlin.reflect.jvm.internal.pcollections;
+
+import java.util.Map;
+import java.util.Map.Entry;
+
+
+/**
+ * (Taken from Java 6 code, so pcollections can be Java 5-compatible.)
+ * <p>
+ * An Entry maintaining an immutable key and value.  This class
+ * does not support method <tt>setValue</tt>.  This class may be
+ * convenient in methods that return thread-safe snapshots of
+ * key-value mappings.
+ *
+ * @since 1.6
+ */
+/*public*/ final class SimpleImmutableEntry<K,V>
+	implements Map.Entry<K,V>, java.io.Serializable
+{
+	private static final long serialVersionUID = 7138329143949025153L;
+
+	private final K key;
+	private final V value;
+
+	/**
+	 * Creates an entry representing a mapping from the specified
+	 * key to the specified value.
+	 *
+	 * @param key the key represented by this entry
+	 * @param value the value represented by this entry
+	 */
+	public SimpleImmutableEntry(K key, V value) {
+		this.key   = key;
+		this.value = value;
+	}
+
+	/**
+	 * Creates an entry representing the same mapping as the
+	 * specified entry.
+	 *
+	 * @param entry the entry to copy
+	 */
+	public SimpleImmutableEntry(Entry<? extends K, ? extends V> entry) {
+		this.key   = entry.getKey();
+		this.value = entry.getValue();
+	}
+
+	/**
+	 * Returns the key corresponding to this entry.
+	 *
+	 * @return the key corresponding to this entry
+	 */
+	public K getKey() {
+		return key;
+	}
+
+	/**
+	 * Returns the value corresponding to this entry.
+	 *
+	 * @return the value corresponding to this entry
+	 */
+	public V getValue() {
+		return value;
+	}
+
+	/**
+	 * Replaces the value corresponding to this entry with the specified
+	 * value (optional operation).  This implementation simply throws
+	 * <tt>UnsupportedOperationException</tt>, as this class implements
+	 * an <i>immutable</i> map entry.
+	 *
+	 * @param value new value to be stored in this entry
+	 * @return (Does not return)
+	 * @throws UnsupportedOperationException always
+	 */
+	public V setValue(V value) {
+		throw new UnsupportedOperationException();
+	}
+
+	/**
+	 * Compares the specified object with this entry for equality.
+	 * Returns {@code true} if the given object is also a map entry and
+	 * the two entries represent the same mapping.	More formally, two
+	 * entries {@code e1} and {@code e2} represent the same mapping
+	 * if<pre>
+	 *   (e1.getKey()==null ?
+	 *    e2.getKey()==null :
+	 *    e1.getKey().equals(e2.getKey()))
+	 *   &amp;&amp;
+	 *   (e1.getValue()==null ?
+	 *    e2.getValue()==null :
+	 *    e1.getValue().equals(e2.getValue()))</pre>
+	 * This ensures that the {@code equals} method works properly across
+	 * different implementations of the {@code Map.Entry} interface.
+	 *
+	 * @param o object to be compared for equality with this map entry
+	 * @return {@code true} if the specified object is equal to this map
+	 *	   entry
+	 * @see    #hashCode
+	 */
+	@Override
+	public boolean equals(Object o) {
+		if (!(o instanceof Map.Entry))
+			return false;
+		Map.Entry<?,?> e = (Map.Entry<?,?>)o;
+		return eq(key, e.getKey()) && eq(value, e.getValue());
+	}
+
+	/**
+	 * Returns the hash code value for this map entry.  The hash code
+	 * of a map entry {@code e} is defined to be: <pre>
+	 *   (e.getKey()==null   ? 0 : e.getKey().hashCode()) ^
+	 *   (e.getValue()==null ? 0 : e.getValue().hashCode())</pre>
+	 * This ensures that {@code e1.equals(e2)} implies that
+	 * {@code e1.hashCode()==e2.hashCode()} for any two Entries
+	 * {@code e1} and {@code e2}, as required by the general
+	 * contract of {@link Object#hashCode}.
+	 *
+	 * @return the hash code value for this map entry
+	 * @see    #equals
+	 */
+	@Override
+	public int hashCode() {
+		return (key   == null ? 0 :   key.hashCode()) ^
+		(value == null ? 0 : value.hashCode());
+	}
+
+	/**
+	 * Returns a String representation of this map entry.  This
+	 * implementation returns the string representation of this
+	 * entry's key followed by the equals character ("<tt>=</tt>")
+	 * followed by the string representation of this entry's value.
+	 *
+	 * @return a String representation of this map entry
+	 */
+	@Override
+	public String toString() {
+		return key + "=" + value;
+	}
+
+    /**
+     * Utility method for SimpleEntry and SimpleImmutableEntry.
+     * Test for equality, checking for nulls.
+     */
+    private static boolean eq(Object o1, Object o2) {
+        return o1 == null ? o2 == null : o1.equals(o2);
+    }
+}
diff --git a/license/third_party/pcollections_LICENSE.txt b/license/third_party/pcollections_LICENSE.txt
new file mode 100644
index 00000000000..345a0dad954
--- /dev/null
+++ b/license/third_party/pcollections_LICENSE.txt
@@ -0,0 +1,19 @@
+Copyright (c) 2008 Harold Cooper
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.