fixup! feat: add str_to_datetime function

Author: yuha-yuha

src/Processor/Expression/FunctionEvaluator.php

@@ -1542,15 +1542,15 @@ private static function sqlStrToDate(
         FunctionExpression $expr,
         array              $row,
         QueryResult        $result
-    ) {
+    ) : string | false {
         $args = $expr->args;
 
         if (\count($args) !== 2) {
             throw new ProcessorException("MySQL DATE_FORMAT() function must be called with one argument");
         }
 
-        $subject = Evaluator::evaluate($conn, $scope, $args[0], $row, $result);
-        $format = Evaluator::evaluate($conn, $scope, $args[1], $row, $result);
+        $subject = (string) Evaluator::evaluate($conn, $scope, $args[0], $row, $result);
+        $format = (string) Evaluator::evaluate($conn, $scope, $args[1], $row, $result);
 
         if (strpos($format, '%') === false) {
             return false;