diff --git a/src/Symfony/Component/Form/Extension/Core/DataTransformer/NumberToLocalizedStringTransformer.php b/src/Symfony/Component/Form/Extension/Core/DataTransformer/NumberToLocalizedStringTransformer.php
index 911246782df9..0693e7979759 100644
--- a/src/Symfony/Component/Form/Extension/Core/DataTransformer/NumberToLocalizedStringTransformer.php
+++ b/src/Symfony/Component/Form/Extension/Core/DataTransformer/NumberToLocalizedStringTransformer.php
@@ -183,35 +183,21 @@ protected function castParsedValue(int|float $value): int|float
      */
     private function round(int|float $number): int|float
     {
-        if (null !== $this->scale && null !== $this->roundingMode) {
+        if (null !== $this->scale) {
             // shift number to maintain the correct scale during rounding
             $roundingCoef = 10 ** $this->scale;
             // string representation to avoid rounding errors, similar to bcmul()
             $number = (string) ($number * $roundingCoef);
 
-            switch ($this->roundingMode) {
-                case \NumberFormatter::ROUND_CEILING:
-                    $number = ceil($number);
-                    break;
-                case \NumberFormatter::ROUND_FLOOR:
-                    $number = floor($number);
-                    break;
-                case \NumberFormatter::ROUND_UP:
-                    $number = $number > 0 ? ceil($number) : floor($number);
-                    break;
-                case \NumberFormatter::ROUND_DOWN:
-                    $number = $number > 0 ? floor($number) : ceil($number);
-                    break;
-                case \NumberFormatter::ROUND_HALFEVEN:
-                    $number = round($number, 0, \PHP_ROUND_HALF_EVEN);
-                    break;
-                case \NumberFormatter::ROUND_HALFUP:
-                    $number = round($number, 0, \PHP_ROUND_HALF_UP);
-                    break;
-                case \NumberFormatter::ROUND_HALFDOWN:
-                    $number = round($number, 0, \PHP_ROUND_HALF_DOWN);
-                    break;
-            }
+            $number = match ($this->roundingMode) {
+                \NumberFormatter::ROUND_CEILING => ceil($number),
+                \NumberFormatter::ROUND_FLOOR => floor($number),
+                \NumberFormatter::ROUND_UP => $number > 0 ? ceil($number) : floor($number),
+                \NumberFormatter::ROUND_DOWN => $number > 0 ? floor($number) : ceil($number),
+                \NumberFormatter::ROUND_HALFEVEN => round($number, 0, \PHP_ROUND_HALF_EVEN),
+                \NumberFormatter::ROUND_HALFUP => round($number, 0, \PHP_ROUND_HALF_UP),
+                \NumberFormatter::ROUND_HALFDOWN => round($number, 0, \PHP_ROUND_HALF_DOWN),
+            };
 
             $number = 1 === $roundingCoef ? (int) $number : $number / $roundingCoef;
         }
diff --git a/src/Symfony/Component/Form/Extension/Core/DataTransformer/PercentToLocalizedStringTransformer.php b/src/Symfony/Component/Form/Extension/Core/DataTransformer/PercentToLocalizedStringTransformer.php
index 0915021d3bab..98d62783c1c0 100644
--- a/src/Symfony/Component/Form/Extension/Core/DataTransformer/PercentToLocalizedStringTransformer.php
+++ b/src/Symfony/Component/Form/Extension/Core/DataTransformer/PercentToLocalizedStringTransformer.php
@@ -180,9 +180,7 @@ protected function getNumberFormatter(): \NumberFormatter
 
         $formatter->setAttribute(\NumberFormatter::FRACTION_DIGITS, $this->scale);
 
-        if (null !== $this->roundingMode) {
-            $formatter->setAttribute(\NumberFormatter::ROUNDING_MODE, $this->roundingMode);
-        }
+        $formatter->setAttribute(\NumberFormatter::ROUNDING_MODE, $this->roundingMode);
 
         return $formatter;
     }
@@ -192,43 +190,27 @@ protected function getNumberFormatter(): \NumberFormatter
      */
     private function round(int|float $number): int|float
     {
-        if (null !== $this->scale && null !== $this->roundingMode) {
-            // shift number to maintain the correct scale during rounding
-            $roundingCoef = 10 ** $this->scale;
+        // shift number to maintain the correct scale during rounding
+        $roundingCoef = 10 ** $this->scale;
 
-            if (self::FRACTIONAL == $this->type) {
-                $roundingCoef *= 100;
-            }
+        if (self::FRACTIONAL === $this->type) {
+            $roundingCoef *= 100;
+        }
 
-            // string representation to avoid rounding errors, similar to bcmul()
-            $number = (string) ($number * $roundingCoef);
-
-            switch ($this->roundingMode) {
-                case \NumberFormatter::ROUND_CEILING:
-                    $number = ceil($number);
-                    break;
-                case \NumberFormatter::ROUND_FLOOR:
-                    $number = floor($number);
-                    break;
-                case \NumberFormatter::ROUND_UP:
-                    $number = $number > 0 ? ceil($number) : floor($number);
-                    break;
-                case \NumberFormatter::ROUND_DOWN:
-                    $number = $number > 0 ? floor($number) : ceil($number);
-                    break;
-                case \NumberFormatter::ROUND_HALFEVEN:
-                    $number = round($number, 0, \PHP_ROUND_HALF_EVEN);
-                    break;
-                case \NumberFormatter::ROUND_HALFUP:
-                    $number = round($number, 0, \PHP_ROUND_HALF_UP);
-                    break;
-                case \NumberFormatter::ROUND_HALFDOWN:
-                    $number = round($number, 0, \PHP_ROUND_HALF_DOWN);
-                    break;
-            }
+        // string representation to avoid rounding errors, similar to bcmul()
+        $number = (string) ($number * $roundingCoef);
 
-            $number = 1 === $roundingCoef ? (int) $number : $number / $roundingCoef;
-        }
+        $number = match ($this->roundingMode) {
+            \NumberFormatter::ROUND_CEILING => ceil($number),
+            \NumberFormatter::ROUND_FLOOR => floor($number),
+            \NumberFormatter::ROUND_UP => $number > 0 ? ceil($number) : floor($number),
+            \NumberFormatter::ROUND_DOWN => $number > 0 ? floor($number) : ceil($number),
+            \NumberFormatter::ROUND_HALFEVEN => round($number, 0, \PHP_ROUND_HALF_EVEN),
+            \NumberFormatter::ROUND_HALFUP => round($number, 0, \PHP_ROUND_HALF_UP),
+            \NumberFormatter::ROUND_HALFDOWN => round($number, 0, \PHP_ROUND_HALF_DOWN),
+        };
+
+        $number = 1 === $roundingCoef ? (int) $number : $number / $roundingCoef;
 
         return $number;
     }
diff --git a/src/Symfony/Component/Form/Form.php b/src/Symfony/Component/Form/Form.php
index 5c86d27b56f6..88c43766190a 100644
--- a/src/Symfony/Component/Form/Form.php
+++ b/src/Symfony/Component/Form/Form.php
@@ -21,7 +21,6 @@
 use Symfony\Component\Form\Exception\OutOfBoundsException;
 use Symfony\Component\Form\Exception\RuntimeException;
 use Symfony\Component\Form\Exception\TransformationFailedException;
-use Symfony\Component\Form\Exception\UnexpectedTypeException;
 use Symfony\Component\Form\Extension\Core\Type\TextType;
 use Symfony\Component\Form\Util\FormUtil;
 use Symfony\Component\Form\Util\InheritDataAwareIterator;
@@ -727,12 +726,6 @@ public function add(FormInterface|string $child, string $type = null, array $opt
         }
 
         if (!$child instanceof FormInterface) {
-            if (!\is_string($child) && !\is_int($child)) {
-                throw new UnexpectedTypeException($child, 'string or Symfony\Component\Form\FormInterface');
-            }
-
-            $child = (string) $child;
-
             // Never initialize child forms automatically
             $options['auto_initialize'] = false;
 
diff --git a/src/Symfony/Component/Form/FormBuilder.php b/src/Symfony/Component/Form/FormBuilder.php
index 33f07b0f1dc0..816c38810fc3 100644
--- a/src/Symfony/Component/Form/FormBuilder.php
+++ b/src/Symfony/Component/Form/FormBuilder.php
@@ -14,7 +14,6 @@
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 use Symfony\Component\Form\Exception\BadMethodCallException;
 use Symfony\Component\Form\Exception\InvalidArgumentException;
-use Symfony\Component\Form\Exception\UnexpectedTypeException;
 use Symfony\Component\Form\Extension\Core\Type\TextType;
 
 /**
@@ -60,10 +59,6 @@ public function add(FormBuilderInterface|string $child, string $type = null, arr
             return $this;
         }
 
-        if (!\is_string($child) && !\is_int($child)) {
-            throw new UnexpectedTypeException($child, 'string or Symfony\Component\Form\FormBuilderInterface');
-        }
-
         // Add to "children" to maintain order
         $this->children[$child] = null;
         $this->unresolvedChildren[$child] = [$type, $options];