Generalize forEachValue/Entry

Author: blambov

src/java/org/apache/cassandra/db/tries/BaseTrie.java

@@ -78,25 +78,25 @@ default void addPathBytes(DirectBuffer buffer, int pos, int count)
     }
 
     /// Call the given consumer on all content values in the trie in order.
-    default void forEachValue(ValueConsumer<T> consumer)
+    default void forEachValue(ValueConsumer<? super T> consumer)
     {
         process(Direction.FORWARD, consumer);
     }
 
     /// Call the given consumer on all content values in the trie in order.
-    default void forEachValue(Direction direction, ValueConsumer<T> consumer)
+    default void forEachValue(Direction direction, ValueConsumer<? super T> consumer)
     {
         process(direction, consumer);
     }
 
     /// Call the given consumer on all (path, content) pairs with non-null content in the trie in order.
-    default void forEachEntry(BiConsumer<ByteComparable, T> consumer)
+    default void forEachEntry(BiConsumer<ByteComparable, ? super T> consumer)
     {
         forEachEntry(Direction.FORWARD, consumer);
     }
 
     /// Call the given consumer on all (path, content) pairs with non-null content in the trie in order.
-    default void forEachEntry(Direction direction, BiConsumer<ByteComparable, T> consumer)
+    default void forEachEntry(Direction direction, BiConsumer<ByteComparable, ? super T> consumer)
     {
         Cursor<T> cursor = cursor(direction);
         cursor.process(new TrieEntriesWalker.WithConsumer<>(consumer, cursor.byteComparableVersion()));
@@ -111,14 +111,14 @@ default <R> R process(Direction direction, Cursor.Walker<? super T, R> walker)
     }
 
     /// Process the trie using the given [ValueConsumer], skipping all branches below the top content-bearing node.
-    default void forEachValueSkippingBranches(Direction direction, ValueConsumer<T> consumer)
+    default void forEachValueSkippingBranches(Direction direction, ValueConsumer<? super T> consumer)
     {
         processSkippingBranches(direction, consumer);
     }
 
     /// Call the given consumer on all `(path, content)` pairs with non-null content in the trie in order, skipping all
     /// branches below the top content-bearing node.
-    default void forEachEntrySkippingBranches(Direction direction, BiConsumer<ByteComparable, T> consumer)
+    default void forEachEntrySkippingBranches(Direction direction, BiConsumer<ByteComparable, ? super T> consumer)
     {
         Cursor<T> cursor = cursor(direction);
         cursor.processSkippingBranches(new TrieEntriesWalker.WithConsumer<>(consumer, cursor.byteComparableVersion()));
@@ -127,7 +127,7 @@ default void forEachEntrySkippingBranches(Direction direction, BiConsumer<ByteCo
     }
 
     /// Process the trie using the given [Cursor.Walker], skipping all branches below the top content-bearing node.
-    default <R> R processSkippingBranches(Direction direction, Cursor.Walker<T, R> walker)
+    default <R> R processSkippingBranches(Direction direction, Cursor.Walker<? super T, R> walker)
     {
         return cursor(direction).processSkippingBranches(walker);
     }

src/java/org/apache/cassandra/db/tries/Cursor.java

@@ -289,7 +289,7 @@ default <R> R process(Cursor.Walker<? super T, R> walker)
 
     /// Process the trie using the given [Walker], skipping over branches where content was found.
     /// This method should only be called on a freshly constructed cursor.
-    default <R> R processSkippingBranches(Cursor.Walker<T, R> walker)
+    default <R> R processSkippingBranches(Cursor.Walker<? super T, R> walker)
     {
         assert depth() == 0 : "The provided cursor has already been advanced.";
         T content = content();   // handle content on the root node

src/java/org/apache/cassandra/db/tries/DepthAdjustedCursor.java

@@ -121,7 +121,7 @@ public <R> R process(Walker<? super T, R> walker)
     }
 
     @Override
-    public <R> R processSkippingBranches(Walker<T, R> walker)
+    public <R> R processSkippingBranches(Walker<? super T, R> walker)
     {
         throw new AssertionError("Depth-adjusted cursors cannot be walked directly.");
     }

src/java/org/apache/cassandra/db/tries/TrieEntriesWalker.java

@@ -36,10 +36,10 @@ public void content(T content)
     /// Iterator representing the content of the trie a sequence of (path, content) pairs.
     static class WithConsumer<T> extends TrieEntriesWalker<T, Void>
     {
-        private final BiConsumer<ByteComparable, T> consumer;
+        private final BiConsumer<ByteComparable, ? super T> consumer;
         private final ByteComparable.Version byteComparableVersion;
 
-        public WithConsumer(BiConsumer<ByteComparable, T> consumer, ByteComparable.Version byteComparableVersion)
+        public WithConsumer(BiConsumer<ByteComparable, ? super T> consumer, ByteComparable.Version byteComparableVersion)
         {
             this.consumer = consumer;
             this.byteComparableVersion = byteComparableVersion;