'Item' nodes cannot have PDOM content, see #771

js/AquaRadioButtonGroup.ts

@@ -97,6 +97,10 @@ export default class AquaRadioButtonGroup<T> extends FlowBox {
     for ( let i = 0; i < items.length; i++ ) {
       const item = items[ i ];
 
+      assert && assert( !item.node.hasPDOMContent,
+        'Accessibility is provided by AquaRadioButton and AquaRadioButtonGroupItem.labelContent. ' +
+        'Additional PDOM content in the provided Node could break accessibility.' );
+
       // Content for the radio button.
       // For vertical orientation, add an invisible strut, so that buttons have uniform width.
       const content = ( options.orientation === 'vertical' ) ?

js/buttons/RectangularRadioButtonGroup.ts

@@ -10,7 +10,7 @@
 import { Shape } from '../../../kite/js/imports.js';
 import InstanceRegistry from '../../../phet-core/js/documentation/InstanceRegistry.js';
 import merge from '../../../phet-core/js/merge.js';
-import { Color, FocusHighlightPath, IInputListener, IPaint, FlowBox, FlowBoxOptions, Node, PDOMPeer, Rectangle, SceneryConstants } from '../../../scenery/js/imports.js';
+import { Color, FlowBox, FlowBoxOptions, FocusHighlightPath, IInputListener, IPaint, Node, PDOMPeer, Rectangle, SceneryConstants } from '../../../scenery/js/imports.js';
 import multiSelectionSoundPlayerFactory from '../../../tambo/js/multiSelectionSoundPlayerFactory.js';
 import Tandem from '../../../tandem/js/Tandem.js';
 import ColorConstants from '../ColorConstants.js';
@@ -286,6 +286,10 @@ export default class RectangularRadioButtonGroup<T> extends FlowBox {
         radioButtonGroupMemberOptions.tandem = options.tandem.createTandem( item.tandemName );
       }
 
+      assert && assert( !item.node.hasPDOMContent,
+        'Accessibility is provided by RectangularRadioButton and RectangularRadioButtonItem.labelContent. ' +
+        'Additional PDOM content in the provided Node could break accessibility.' );
+
       // create the label and voicing response for the radio button
       if ( item.labelContent ) {
         radioButtonGroupMemberOptions.labelContent = item.labelContent;