Fix assertion in RubyCallNode#assign when isSplatted

(cherry picked from commit 973ba7c)

Author: eregon

src/main/java/org/truffleruby/core/array/ArrayAppendOneNode.java

@@ -25,7 +25,7 @@
 import com.oracle.truffle.api.profiles.ConditionProfile;
 
 @NodeChild(value = "array", type = RubyNode.class)
-@NodeChild(value = "value", type = RubyNode.class)
+@NodeChild(value = "valueNode", type = RubyNode.class)
 @ImportStatic(ArrayGuards.class)
 public abstract class ArrayAppendOneNode extends RubyContextSourceNode {
 
@@ -37,6 +37,8 @@ public static ArrayAppendOneNode create() {
 
     public abstract RubyArray executeAppendOne(RubyArray array, Object value);
 
+    public abstract RubyNode getValueNode();
+
     // Append of the correct type
 
     @Specialization(

src/main/java/org/truffleruby/language/dispatch/RubyCallNode.java

@@ -11,6 +11,7 @@
 
 import org.truffleruby.RubyContext;
 import org.truffleruby.RubyLanguage;
+import org.truffleruby.core.array.ArrayAppendOneNode;
 import org.truffleruby.core.array.ArrayToObjectArrayNode;
 import org.truffleruby.core.array.ArrayToObjectArrayNodeGen;
 import org.truffleruby.core.array.AssignableNode;
@@ -100,8 +101,8 @@ public Object execute(VirtualFrame frame) {
 
     @Override
     public void assign(VirtualFrame frame, Object value) {
-        assert getLastArgumentNode() instanceof NilLiteralNode &&
-                ((NilLiteralNode) getLastArgumentNode()).isImplicit() : getLastArgumentNode();
+        assert (getLastArgumentNode() instanceof NilLiteralNode &&
+                ((NilLiteralNode) getLastArgumentNode()).isImplicit()) : getLastArgumentNode();
 
         final Object receiverObject = receiver.execute(frame);
         if (isSafeNavigation && nilProfile.profile(receiverObject == nil)) {
@@ -195,7 +196,11 @@ public boolean hasLiteralBlock() {
     }
 
     private RubyNode getLastArgumentNode() {
-        return arguments[arguments.length - 1];
+        final RubyNode lastArg = arguments[arguments.length - 1];
+        if (isSplatted && lastArg instanceof ArrayAppendOneNode) {
+            return ((ArrayAppendOneNode) lastArg).getValueNode();
+        }
+        return lastArg;
     }
 
     @Override