Unable to bind Annotated to instances of origin

Originally stemming from interest in #133 , I too thought to replicate Guice's @Named convention. In doing so, I originally used the typing.NewType (prior to having even seen the aforementioned issue) and succeeded. However, instantiating a type for each simple alias, I thought typing.Annotated (albeit, using typing_extensions.Annotated) would be more idiomatic.

Given a simple example:

import pathlib
import injector

ConfigFile = injector.Annotated[pathlib.WindowsPath, 'config']

cfg_file = pathlib.Path.home() / 'settings.cfg'


class AppModule(injector.Module):

    def configure(self, binder):
        binder.bind(ConfigFile, to=cfg_file) # Guice uses annotatedWith here

class App:

    @injector.inject
    def __init__(self, cfg: ConfigFile):
        self.config = cfg

app = injector.Injector(AppModule).get(App)

...throws...

Traceback (most recent call last):
  File "E:\Programming\test\test_injector\test.py", line 20, in <module>
    app = injector.Injector(AppModule).get(App)
  File "C:\Python37\lib\site-packages\injector\__init__.py", line 913, in __init__
    self.binder.install(module)
  File "C:\Python37\lib\site-packages\injector\__init__.py", line 577, in install
    instance(self)
  File "C:\Python37\lib\site-packages\injector\__init__.py", line 860, in __call__
    self.configure(binder)
  File "E:\Programming\test\test_injector\test.py", line 12, in configure
    binder.bind(ConfigFile, to=cfg_file) # Guice uses annotatedWith here
  File "C:\Python37\lib\site-packages\injector\__init__.py", line 479, in bind
    self._bindings[interface] = self.create_binding(interface, to, scope)
  File "C:\Python37\lib\site-packages\injector\__init__.py", line 582, in create_binding
    provider = self.provider_for(interface, to)
  File "C:\Python37\lib\site-packages\injector\__init__.py", line 644, in provider_for
    raise UnknownProvider('couldn\'t determine provider for %r to %r' % (interface, to))
injector.UnknownProvider: couldn't determine provider for typing_extensions.Annotated[pathlib.WindowsPath, 'config'] to WindowsPath('C:/Users/Paul/settings.cfg')

My belief is that provider_for does not adequately check to see if the interface is an _AnnotatedAlias or not. The origin variable resolves to the base interface correctly, in this case pathlib.WindowsPath, but since base_type is typing_extenstions.Annotated, not check is made given that case.

Start at the Binder.provider_for entry point shown in the traceback and reproduce the pathlib.WindowsPath example with typing_extensions.Annotated. Trace how the Annotated interface and its origin are handled; done means binding the annotated alias to cfg_file succeeds and injector.Injector(AppModule).get(App) constructs App with that value.