Symfony\Component\Routing\RouteCompiler::compile PHP Method

    public static function compile(Route $route)
    {
        $hostVariables = array();
        $variables = array();
        $hostRegex = null;
        $hostTokens = array();
        if ('' !== ($host = $route->getHost())) {
            $result = self::compilePattern($route, $host, true);
            $hostVariables = $result['variables'];
            $variables = $hostVariables;
            $hostTokens = $result['tokens'];
            $hostRegex = $result['regex'];
        }
        $path = $route->getPath();
        $result = self::compilePattern($route, $path, false);
        $staticPrefix = $result['staticPrefix'];
        $pathVariables = $result['variables'];
        foreach ($pathVariables as $pathParam) {
            if ('_fragment' === $pathParam) {
                throw new \InvalidArgumentException(sprintf('Route pattern "%s" cannot contain "_fragment" as a path parameter.', $route->getPath()));
            }
        }
        $variables = array_merge($variables, $pathVariables);
        $tokens = $result['tokens'];
        $regex = $result['regex'];
        return new CompiledRoute($staticPrefix, $regex, $tokens, $pathVariables, $hostRegex, $hostTokens, $hostVariables, array_unique($variables));
    }

 /**
  * Compiles the current route instance.
  *
  * Because so much of the parent class is private, we need to call the parent
  * class's compile() method and then dissect its return value to build our
  * new compiled object.  If upstream gets refactored so we can subclass more
  * easily then this may not be necessary.
  *
  * @param \Symfony\Component\Routing\Route $route
  *   A Route instance.
  *
  * @return \Drupal\Core\Routing\CompiledRoute
  *   A CompiledRoute instance.
  */
 public static function compile(Route $route)
 {
     $symfony_compiled = parent::compile($route);
     // The Drupal-specific compiled information.
     $stripped_path = static::getPathWithoutDefaults($route);
     $fit = static::getFit($stripped_path);
     $pattern_outline = static::getPatternOutline($stripped_path);
     $num_parts = count(explode('/', trim($pattern_outline, '/')));
     return new CompiledRoute($route, $fit, $pattern_outline, $num_parts, $symfony_compiled->getStaticPrefix(), $symfony_compiled->getRegex(), $symfony_compiled->getTokens(), $symfony_compiled->getPathVariables(), $symfony_compiled->getHostRegex(), $symfony_compiled->getHostTokens(), $symfony_compiled->getHostVariables(), $symfony_compiled->getVariables());
 }