Add support for Optional chaining in ReferenceCollectingCallBack pass

PiperOrigin-RevId: 321252042

Author: rishipal

src/com/google/javascript/jscomp/ReferenceCollectingCallback.java

@@ -337,6 +337,9 @@ private static boolean isBlockBoundary(Node n, Node parent) {
         case OR:
         case SWITCH:
         case COALESCE:
+        case OPTCHAIN_GETPROP:
+        case OPTCHAIN_GETELEM:
+        case OPTCHAIN_CALL:
           // The first child of a conditional is not a boundary,
           // but all the rest of the children are.
           return n != parent.getFirstChild();

test/com/google/javascript/jscomp/ReferenceCollectingCallbackTest.java

@@ -427,6 +427,26 @@ public void afterExitScope(NodeTraversal t, ReferenceMap rm) {
         });
   }
 
+  @Test
+  public void optionalChaining() {
+    setLanguage(UNSUPPORTED, UNSUPPORTED);
+    testBehavior(
+        "var x = 0; var y = x?.(x = 1)",
+        new Behavior() {
+          @Override
+          public void afterExitScope(NodeTraversal t, ReferenceMap rm) {
+            if (t.getScope().isGlobal()) {
+              ReferenceCollection x = rm.getReferences(t.getScope().getVar("x"));
+              assertThat(x.references).hasSize(3);
+              assertNode(x.references.get(0).getBasicBlock().getRoot()).hasType(Token.ROOT);
+              assertNode(x.references.get(1).getBasicBlock().getRoot()).hasType(Token.ROOT);
+              // first child of `?.` is not a boundary, but the second child is.
+              assertNode(x.references.get(2).getBasicBlock().getRoot()).hasType(Token.ASSIGN);
+            }
+          }
+        });
+  }
+
   @Test
   public void testThis() {
     testBehavior(