Kalle Vuorjoki
--- a/core/modules/views/tests/src/Kernel/Handler/FilterBooleanOperatorTest.php
+++ b/core/modules/views/tests/src/Kernel/Handler/FilterBooleanOperatorTest.php
    $this->assertIdenticalResultset($view, $expected_result, $this->columnMap);
  }

+  /**
+   * Tests the BooleanOperator empty/not empty filters.
+   */
+  public function testEmptyFilterBooleanOperator() {
-  public function testEmptyFilterBooleanOperator() {
+  public function testEmptyFilterBooleanOperator(): void {
--- a/core/modules/views/src/Plugin/views/filter/BooleanOperator.php
+++ b/core/modules/views/src/Plugin/views/filter/BooleanOperator.php
+      $operator = "IS NOT NULL";
+    }
+
+    $this->query->addWhere($this->options['group'], $field, NULL, $operator);
+  }
+
+  /**
+   * Returns operators for values.
+   *
+   * @param int $values
+   *   The values filter value.
+   *
+   * @return string[]
+   *   A filtered list of operators.
+   */
+  protected function operatorValues($values = 1) {
-  protected function operatorValues($values = 1) {
+  protected function operatorValues(int $values = 1): array {
--- a/core/modules/views/src/Plugin/views/filter/BooleanOperator.php
+++ b/core/modules/views/src/Plugin/views/filter/BooleanOperator.php
    }
  }

+  /**
+   * Filters by operator empty.
+   *
+   * @param string $field
+   *   The views field.
+   */
+  protected function opEmpty($field) {
-  protected function opEmpty($field) {
+  protected function opEmpty(string $field): void {