set AnyPointer from AnyPointer

compiler/src/test/java/org/capnproto/EncodingTest.java

@@ -844,6 +844,19 @@ public class EncodingTest {
       Assert.assertEquals(listReader.get(0).getInt8Field(), 11);
       TestUtil.checkTestMessage(listReader.get(1));
   }
+
+    @org.junit.Test
+    public void testCopyAnyPointer() {
+        MessageBuilder message1 = new MessageBuilder();
+        Test.TestAllTypes.Builder root1 = message1.initRoot(Test.TestAllTypes.factory);
+        TestUtil.initTestMessage(root1);
+
+        MessageBuilder message2 = new MessageBuilder();
+        AnyPointer.Builder root2 = message2.initRoot(AnyPointer.factory);
+        root2.set(message1.getRoot(AnyPointer.factory).asReader());
+
+        TestUtil.checkTestMessage(root2.getAs(Test.TestAllTypes.factory));
+    }
 }
 
 

runtime-rpc/src/main/java/org/capnproto/RpcState.java

@@ -1353,7 +1353,38 @@ final class RpcState<VatId> {
 
         @Override
         public ClientHook.VoidPromiseAndPipeline directTailCall(RequestHook request) {
-            return null;
+            assert this.response == null: "Can't call tailCall() after initializing the results struct.";
+
+            if (request.getBrand() == RpcState.this && !this.redirectResults) {
+                // The tail call is headed towards the peer that called us in the first place, so we can
+                // optimize out the return trip.
+
+                var tailInfo = ((RpcRequest)request).tailSend();
+                if (tailInfo != null) {
+                    if (isFirstResponder()) {
+                        if (isConnected()) {
+                            var message = connection.newOutgoingMessage(
+                                    messageSizeHint()
+                                            + RpcProtocol.Return.factory.structSize().total());
+                            var builder = message.getBody().initAs(RpcProtocol.Message.factory).initReturn();
+                            builder.setAnswerId(this.answerId);
+                            builder.setReleaseParamCaps(false);
+                            builder.setTakeFromOtherQuestion(tailInfo.questionId);
+                            message.send();
+                        }
+
+                        cleanupAnswerTable(null, false);
+                    }
+                    return new ClientHook.VoidPromiseAndPipeline(tailInfo.promise, tailInfo.pipeline);
+                }
+            }
+
+            // Just forward to another local call
+            var promise = request.send();
+            var voidPromise = promise.thenAccept(results -> {
+                getResults(0).set(results);
+            });
+            return new ClientHook.VoidPromiseAndPipeline(voidPromise, promise.pipeline().hook);
         }
 
         private RpcResponse consumeRedirectedResponse() {

runtime/src/main/java/org/capnproto/AnyPointer.java

@@ -128,6 +128,18 @@ public final class AnyPointer {
             factory.setPointerBuilder(this.segment, this.capTable, this.pointer, reader);
         }
 
+        public void set(AnyPointer.Reader reader) {
+            if (reader.isNull()) {
+                WireHelpers.zeroObject(this.segment, this.capTable, this.pointer);
+                WireHelpers.zeroPointerAndFars(this.segment, this.pointer);
+            }
+            else {
+                WireHelpers.copyPointer(
+                        this.segment, this.capTable, this.pointer,
+                        reader.segment, reader.capTable, reader.pointer, reader.nestingLimit);
+            }
+        }
+
         final void setAsCap(Capability.Client cap) {
             WireHelpers.setCapabilityPointer(this.segment, capTable, this.pointer, cap.getHook());
         }