Share a common empty array for mass assignment cases where either the pre- or post- node argument lists are empty.

Author: nirvdrum

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

@@ -144,6 +144,10 @@ public RubyNode cloneUninitialized() {
     }
 
     protected AssignableNode[] cloneUninitializedAssignable(AssignableNode[] nodes) {
+        if (nodes.length == 0) {
+            return AssignableNode.EMPTY_ARRAY;
+        }
+
         AssignableNode[] copies = new AssignableNode[nodes.length];
         for (int i = 0; i < nodes.length; i++) {
             copies[i] = nodes[i].cloneUninitializedAssignable();

src/main/java/org/truffleruby/parser/YARPMultiTargetNodeTranslator.java

@@ -78,10 +78,7 @@ public MultipleAssignmentNode translate() {
                 true,
                 null);
 
-        final AssignableNode[] preNodes = new AssignableNode[node.lefts.length];
-        for (int i = 0; i < node.lefts.length; i++) {
-            preNodes[i] = node.lefts[i].accept(this);
-        }
+        final AssignableNode[] preNodes = processAssignables(node.lefts);
 
         final AssignableNode restNode;
         if (node.rest != null) {
@@ -97,10 +94,7 @@ public MultipleAssignmentNode translate() {
             restNode = null;
         }
 
-        final AssignableNode[] postNodes = new AssignableNode[node.rights.length];
-        for (int i = 0; i < node.rights.length; i++) {
-            postNodes[i] = node.rights[i].accept(this);
-        }
+        final AssignableNode[] postNodes = processAssignables(node.rights);
 
         // prolog is supposed to be executed in the outer MultipleAssignmentNode (in multi-assignment only)
         final var multipleAssignmentNode = new MultipleAssignmentNode(
@@ -113,6 +107,18 @@ public MultipleAssignmentNode translate() {
         return multipleAssignmentNode;
     }
 
+    private AssignableNode[] processAssignables(Nodes.Node[] nodes) {
+        if (nodes.length == 0) {
+            return MultipleAssignmentNode.EMPTY_ASSIGNABLES;
+        }
+
+        final AssignableNode[] assignables = new AssignableNode[nodes.length];
+        for (int i = 0; i < nodes.length; i++) {
+            assignables[i] = nodes[i].accept(this);
+        }
+        return assignables;
+    }
+
     @Override
     public AssignableNode visitClassVariableTargetNode(Nodes.ClassVariableTargetNode node) {
         final RubyNode rubyNode = node.accept(yarpTranslator);