Hello everyone!

Bug occurs when web profiler bundle is used.
Prior 4.0.8 if I have not configured string parameter as dependency I did get an error about it. Today I have a strange error about couldn't autoload a "string" class.
For example, I have a service:

class Service {
  public function __construct(string $key) {
    // some code
  }
}

And I haven't configured it. So container doesn't know what exactly $key it needs. I don't use this service anywhere but have an error: Warning: include(string.php): failed to open stream: No such file or directory (it is because my not PSR4 autoloader in queue), but I haven't an error about service configuration as I expected.

I've done a little research what happens.
In web-profiler-bundle/Resources/config/profiler.xml:

<service id="debug.file_link_formatter.url_format" class="string">
    <factory class="Symfony\Component\HttpKernel\Debug\FileLinkFormatter" method="generateUrlFormat" />
    <argument type="service" id="router" />
    <argument>_profiler_open_file</argument>
    <argument>?file=%%f&amp;line=%%l#line%%l</argument>
</service>

As you can see class="string" but string is not a class really...
So sometimes (not only if configuration is missed) when autowiring is processing method ContainerBuilder::getReflectionClass() is called. It calls ClassExistenceResource::isFresh() which calls class_exists() which triggers autoload.

Part of stack trace:

I think we have two options to resolve this problem:
The first one is changing configuration of file_link_formatter (may be wrap string to some special class with __toString() method?).
The second one is changing ContainerBuilder::getReflectionClass() to avoid getting reflection of internal types.
Or we can do both of course...

P.S.
I'm very sorry for my English. Please, ask any questions if my explanation is not clear.