Description of the bug

I ran typesplainer on my code base and it crashed on the type Optional[Awaitable]. Using mypy on the same file produced no diagnostics indicating a problem with the typing. I've included a reproducer class and the stack trace in the additional information section.

Steps To Reproduce

1. installed from pypi
2. ran on reproducer: python3 -m typesplainer reproducer.py
3. crash

Additional Information

# reproducer.py
from typing import Awaitable, Optional
class BugClass:
    def no_crash(self) -> Optional[Awaitable[None]]:
        """A method that returns None or an Awaitable"""

    def crashes(self) -> Optional[Awaitable]:
        """A method that returns None or an Awaitable"""

$ python3 -m typesplainer reproducer.py 
Optional[Awaitable[None]] (reproducer.py:5:27) : A optional awaitable that returns nothing/none.
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/runpy.py", line 197, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/Users/ejo/Library/Caches/pypoetry/virtualenvs/busylight-for-humans-gON-ipZ_-py3.9/lib/python3.9/site-packages/typesplainer/__main__.py", line 99, in <module>
    print_description(f.read(), file_name=file)
  File "/Users/ejo/Library/Caches/pypoetry/virtualenvs/busylight-for-humans-gON-ipZ_-py3.9/lib/python3.9/site-packages/typesplainer/__main__.py", line 45, in print_description
    console.print(text, format_location(def_, typehint_text, file_name), ":", describe(def_))
  File "/Users/ejo/Library/Caches/pypoetry/virtualenvs/busylight-for-humans-gON-ipZ_-py3.9/lib/python3.9/site-packages/typesplainer/core.py", line 200, in describe
    return _describe(thing).capitalize() + "."
  File "/Users/ejo/Library/Caches/pypoetry/virtualenvs/busylight-for-humans-gON-ipZ_-py3.9/lib/python3.9/site-packages/typesplainer/core.py", line 47, in _describe
    return f"{'a ' if a else ''}optional {_describe(thing.args[0], a=False, plural=plural)}"
  File "/Users/ejo/Library/Caches/pypoetry/virtualenvs/busylight-for-humans-gON-ipZ_-py3.9/lib/python3.9/site-packages/typesplainer/core.py", line 132, in _describe
    return f"{'a ' if a else ''}awaitable that returns {_describe(thing.args[0])}"
IndexError: tuple index out of range
[VE] ejo@ufo:bl2 -> 

Description

Type aliases such as IntegerList = List[int] aren't supported yet

FixedWidthParseSpec = Union[
    Tuple[str, int],
    Tuple[str, int, Optional[int]],
    Tuple[str, int, Optional[int], Optional[Callable[[str], Any]]],
]

Due to how mypy parses these things these are parsed not as types but as any general python object indexing. Essentially

List = [1, 2, 3] 
a = List[0]

And

SomeList = List[int]

Have the same structure, so differentiating between them is a bit hard and requires some processing power since these elements can be nested i.e Dict[List[str], int]

Additional Information

No response