Be more specific with what exception we catch

src/Symfony/Component/Translation/Formatter/FallbackFormatter.php

@@ -12,6 +12,7 @@
 namespace Symfony\Component\Translation\Formatter;
 
 use Symfony\Component\Translation\Exception\LogicException;
+use Symfony\Component\Translation\Exception\InvalidArgumentException;
 
 class FallbackFormatter implements MessageFormatterInterface, ChoiceMessageFormatterInterface
 {
@@ -35,7 +36,7 @@ class FallbackFormatter implements MessageFormatterInterface, ChoiceMessageForma
     {
         try {
             $result = $this->firstFormatter->format($message, $locale, $parameters);
-        } catch (\Throwable $e) {
+        } catch (InvalidArgumentException $e) {
             return $this->secondFormatter->format($message, $locale, $parameters);
         }
 
@@ -52,7 +53,7 @@ class FallbackFormatter implements MessageFormatterInterface, ChoiceMessageForma
         if ($this->firstFormatter instanceof ChoiceMessageFormatterInterface && $this->secondFormatter instanceof ChoiceMessageFormatterInterface) {
             try {
                 $result = $this->firstFormatter->choiceFormat($message, $number, $locale, $parameters);
-            } catch (\Throwable $e) {
+            } catch (InvalidArgumentException $e) {
                 return $this->secondFormatter->choiceFormat($message, $number, $locale, $parameters);
             }
 

src/Symfony/Component/Translation/Tests/Formatter/FallbackFormatterTest.php

@@ -17,6 +17,7 @@ use Symfony\Component\Translation\Formatter\ChoiceMessageFormatterInterface;
 use Symfony\Component\Translation\Formatter\FallbackFormatter;
 use Symfony\Component\Translation\Formatter\MessageFormatterInterface;
 
+
 class FallbackFormatterTest extends \PHPUnit\Framework\TestCase
 {
     public function testFormatSame()
@@ -74,6 +75,23 @@ class FallbackFormatterTest extends \PHPUnit\Framework\TestCase
         $this->assertEquals('bar', (new FallbackFormatter($first, $second))->format('foo', 'en', array(2)));
     }
 
+    public function testFormatExceptionUnknown()
+    {
+        $first = $this->getMockBuilder(MessageFormatterInterface::class)->setMethods(array('format'))->getMock();
+        $first
+            ->expects($this->once())
+            ->method('format')
+            ->willThrowException(new \RuntimeException());
+
+        $second = $this->getMockBuilder(MessageFormatterInterface::class)->setMethods(array('format'))->getMock();
+        $second
+            ->expects($this->exactly(0))
+            ->method('format');
+
+        $this->expectException(\RuntimeException::class);
+        $this->assertEquals('bar', (new FallbackFormatter($first, $second))->format('foo', 'en', array(2)));
+    }
+
     public function testChoiceFormatSame()
     {
         $first = $this->getMockBuilder(SuperFormatterInterface::class)->setMethods(array('format', 'choiceFormat'))->getMock();