added IValue.getPatternMatchFingerprint() that simulates rascal-core:TopLevelType.getFingerprint(v) exactly for the value kinds we have in vallang

pom.xml

@@ -4,7 +4,7 @@
 
 	<groupId>io.usethesource</groupId>
 	<artifactId>vallang</artifactId>
-	<version>0.15.2-SNAPSHOT</version>
+	<version>1.0.0-SNAPSHOT</version>
 	<packaging>jar</packaging>
 
 	<scm>

src/main/java/io/usethesource/vallang/IBool.java

@@ -13,6 +13,16 @@
 import io.usethesource.vallang.visitors.IValueVisitor;
 
 public interface IBool extends IValue {
+	@Override
+    default int getMatchFingerprint() {
+        if (getValue()) {
+            return 3569038; /* "true".hashCode() */
+        }
+        else {
+            return 97196323; /* "false".hashCode() */
+        }
+    }
+
 	boolean getValue();
 	String getStringRepresentation();
 	IBool and(IBool other);

src/main/java/io/usethesource/vallang/IConstructor.java

@@ -25,6 +25,11 @@
  */
 public interface IConstructor extends INode {
 
+	@Override
+	default int getMatchFingerprint() {
+		return getName().hashCode() + 131 * arity();
+	}
+
 	/**
 	 * @return the specific ConstructorType of this constructor
 	 */

src/main/java/io/usethesource/vallang/IExternalValue.java

@@ -37,6 +37,12 @@
  * Note that NORMAL USE OF THE PDB DOES NOT REQUIRE IMPLEMENTING THIS INTERFACE
  */
 public interface IExternalValue extends IValue {
+    /** 
+     * External values must re-think their pattern match fingerprint,
+     * instead of returning `IValue.hashCode()` automatically.
+     */
+    @Override
+    int getMatchFingerprint();
 
 	/**
 	 * @return an ExternalType

src/main/java/io/usethesource/vallang/IInteger.java

@@ -15,6 +15,16 @@
 import io.usethesource.vallang.visitors.IValueVisitor;
 
 public interface IInteger extends INumber {
+    @Override
+    default int getMatchFingerprint() {
+        if (signum() == 0) {
+            return 104431; /* "int".hashCode() */
+        }
+        else {
+            return hashCode();
+        }
+    }
+
 	/**
 	 * @return this + other;
 	 */

src/main/java/io/usethesource/vallang/IList.java

@@ -22,6 +22,12 @@
 import io.usethesource.vallang.visitors.IValueVisitor;
 
 public interface IList extends ICollection<IList> {
+
+    @Override
+    default int getMatchFingerprint() {
+        return 3322014; // "list".hashCode()
+    }
+
     /**
      * @return the number of elements in the list
      */

src/main/java/io/usethesource/vallang/IMap.java

@@ -26,6 +26,11 @@
 
 public interface IMap extends ICollection<IMap> {
 
+    @Override
+    default int getMatchFingerprint() {
+        return 107868; // "map".hashCode()
+    }
+
     /**
      * Adds a new entry to the map, mapping the key to value. If the
      * key existed before, the old value will be lost.

src/main/java/io/usethesource/vallang/INode.java

@@ -30,6 +30,14 @@
  * it recursively.
  */
 public interface INode extends IValue, Iterable<IValue> {
+
+	@Override
+	default int getMatchFingerprint() {
+		int hash = getName().hashCode();
+
+		return hash == 0 ? 13547528 /* "node".hashCode() << 2*/ + arity() : hash + 131 * arity(); 
+	}
+
 	/**
 	 * Get a child
 	 * @param i the zero based index of the child

src/main/java/io/usethesource/vallang/IReal.java

@@ -16,6 +16,12 @@
 import io.usethesource.vallang.visitors.IValueVisitor;
 
 public interface IReal extends INumber {
+    @Override
+    default int getMatchFingerprint() {
+        int hash = hashCode();
+        return hash == 0 ? 3496350 /* real.hashCode() */ : hash;
+    }
+
 	/**
 	 * @return this + other;
 	 */

src/main/java/io/usethesource/vallang/ISet.java

@@ -21,6 +21,11 @@
 
 public interface ISet extends ICollection<ISet> {
 
+    @Override
+    default int getMatchFingerprint() {
+        return 113762; // "set".hashCode()
+    }
+
     /**
      * Add an element to the set. 
      * @param element

src/main/java/io/usethesource/vallang/IString.java

@@ -19,6 +19,17 @@
 import io.usethesource.vallang.visitors.IValueVisitor;
 
 public interface IString extends IValue, Iterable<Integer> {
+
+    @Override
+    default int getMatchFingerprint() {
+        if (length() == 0) {
+            return 114225; /* "str".hashCode() */
+        }
+        else {
+            return hashCode();
+        }
+    }
+
 	/**
 	 * @return the Java string that this string represents
 	 */

src/main/java/io/usethesource/vallang/ITuple.java

@@ -16,6 +16,11 @@
 import io.usethesource.vallang.visitors.IValueVisitor;
 
 public interface ITuple extends Iterable<IValue>, IValue {
+    @Override
+    default int getMatchFingerprint() {
+        return 442900256 /* "tuple".hashCode() << 2 */ + arity();
+    }
+
     /**
      * Retrieve the given field at the given index.
      * 

src/main/java/io/usethesource/vallang/IValue.java

@@ -28,7 +28,35 @@ public interface IValue {
 	 * @return the {@link Type} of a value
 	 */
     public Type getType();
+
+    /**
+     * This method is used exclusively by code generated by the Rascal compiler,
+     * or by the Rascal interpreter. The returned integer codes are opaque, although stable.
+     * If you need to know what kind of value you have, use the IValueVisitor or the ITypeVisitor
+     * interfaces and the `accept` methods on IValue and Type.
+     * 
+     * @return an integer code that:
+     *    * accurate reflects the identity of the top-level structure of this value
+     *    * such that if pattern.match(this) ===> pattern.getPatternMatchFingerprint() == this.getPatternMatchFingerprint()
+     *    * distinguishes maximally between different kinds of values
+     *    * never makes the same or similar value have a different fingerprint
+     */
+    default int getMatchFingerprint() {
+        return hashCode();
+    }
 
+     /**
+     * This method is used exclusively by code generated by the Rascal compiler,
+     * 
+     * @return an integer code that:
+     *    * is guaranteed to be different from `getMatchFingerPrint`
+     *    * is guaranteed to be constant
+     *    * is guaranteed to be the same for every IValue
+     */
+    static int getDefaultMatchFingerprint() {
+        return 0;
+    }
+
     /**
      * Execute the {@link IValueVisitor} on the current node
      * 

src/main/java/io/usethesource/vallang/impl/persistent/PersistentHashIndexedBinaryRelation.java

@@ -38,7 +38,6 @@
 import io.usethesource.vallang.ISetWriter;
 import io.usethesource.vallang.ITuple;
 import io.usethesource.vallang.IValue;
-import io.usethesource.vallang.exceptions.IllegalOperationException;
 import io.usethesource.vallang.type.Type;
 import io.usethesource.vallang.util.AbstractTypeBag;
 

src/main/java/io/usethesource/vallang/impl/primitive/IntegerValue.java

@@ -519,6 +519,7 @@ else if (isRationalType(other)) {
 		}
 	}
 
+	@Override
 	public int hashCode(){
 		int h = value ^ 0x85ebca6b;
 		// based on the final Avalanching phase of MurmurHash2

src/main/java/io/usethesource/vallang/util/WeakReferenceHashConsingMap.java

@@ -121,7 +121,6 @@ public boolean equals(@Nullable Object obj) {
      */
     private final HotEntry<T>[] hotEntries;
     private final int mask;
-    private final int expireAfter;
 
     /** 
      * All entries are also stored in a WeakReference, this helps with clearing memory
@@ -143,7 +142,6 @@ public WeakReferenceHashConsingMap(int size, int demoteAfterSeconds) {
         size = Integer.highestOneBit(size - 1) << 1;
         hotEntries = new HotEntry[size]; 
         this.mask = size - 1;
-        this.expireAfter = demoteAfterSeconds;
 
         coldEntries = new ConcurrentHashMap<>(size);
 

src/test/java/io/usethesource/vallang/ValueProvider.java

@@ -337,8 +337,26 @@ private RandomTypesConfig configureRandomTypes(TypeConfig typeConfig, int depth)
      * @return an instance assignable to `cl`
      */
     private IValue generateValue(IValueFactory vf, TypeStore ts, Class<? extends IValue> cl, ExpectedType expected, int depth, int width) {
-        Type expectedType = expected != null ? readType(ts, expected) : types.getOrDefault(cl, (x, n) -> tf.valueType()).apply(ts, expected);
+        Type expectedType = tf.voidType();
+
 
+        // this should terminate through random selection.
+        // only tuple types with nested void arguments can reduce to void.
+        int i = 0;
+        while (expectedType.isBottom() && i++ < 1000) {
+            if (expected != null) {
+                expectedType = readType(ts, expected);
+                break;
+            }
+            else {
+                expectedType = types
+                    .getOrDefault(cl, (x, n) -> tf.valueType())
+                    .apply(ts, expected);         
+            }
+        }
+
+        assert !expectedType.isBottom() : cl + " generated void type?";
+
         if (previous != null && rnd.nextInt(4) == 0 && previous.getType().isSubtypeOf(expectedType)) {
             return rnd.nextBoolean() ? previous : reinstantiate(vf, ts, previous);
         }