--- /dev/null
+<?php
+
+namespace Drupal\drupalmoduleupgrader\Plugin\DMU\Converter\Functions;
+
+use Drupal\drupalmoduleupgrader\TargetInterface;
+use Pharborist\Functions\FunctionCallNode;
+
+/**
+ * @Converter(
+ * id = "form_state_defaults",
+ * description = @Translation("Rewrites calls to form_state_defaults().")
+ * )
+ */
+class FormStateDefaults extends FunctionCallModifier {
+
+ /**
+ * {@inheritdoc}
+ */
+ public function rewrite(FunctionCallNode $call, TargetInterface $target) {
+ // @todo
+ // There are two possibilities here. If the call is part of a += operation
+ // or an array_merge() call, the entire thing needs to be commented out.
+ // Otherwise, it should be changed to 'new FormState()', which requires an
+ // upstream change in Pharborist.
+ }
+
+}