[Yaml] Fix scope resolution operator in flow mapping keys

Author: MatTheCat

src/Symfony/Component/Yaml/Inline.php

@@ -453,7 +453,7 @@ private static function parseMapping(string $mapping, int $flags, int &$i = 0, a
             }
 
             if ('!php/const' === $key || '!php/enum' === $key) {
-                $key .= ' '.self::parseScalar($mapping, $flags, [':'], $i, false);
+                $key .= ' '.self::parseScalar($mapping, $flags, ['(?<!:):(?!:)'], $i, false);
                 $key = self::evaluateScalar($key, $flags);
             }
 

src/Symfony/Component/Yaml/Tests/InlineTest.php

@@ -63,6 +63,7 @@ public static function getTestsForParsePhpConstants()
             ['{ foo: !php/const PHP_INT_MAX }', ['foo' => \PHP_INT_MAX]],
             ['{ !php/const PHP_INT_MAX: foo }', [\PHP_INT_MAX => 'foo']],
             ['!php/const NULL', null],
+            ['{ !php/const Symfony\Component\Yaml\Yaml::PARSE_CONSTANT: foo }', [Yaml::PARSE_CONSTANT => 'foo']],
         ];
     }