parse embedded mappings only if value is a string

src/Symfony/Component/Yaml/Inline.php

@@ -397,7 +397,7 @@ class Inline
                     $value = self::parseScalar($sequence, $flags, array(',', ']'), array('"', "'"), $i, true, $references);
 
                     // the value can be an array if a reference has been resolved to an array var
-                    if (!is_array($value) && !$value instanceof \DateTimeInterface && !$isQuoted && false !== strpos($value, ': ')) {
+                    if (is_string($value) && !$isQuoted && false !== strpos($value, ': ')) {
                         // embedded mapping?
                         try {
                             $pos = 0;