Skip to content

Unexpected IndexError in typing.List[''] #116325

@jureslak

Description

@jureslak

Bug report

Bug description:

Calling typing.List[''] produces an unexpected IndexError.

>>> import typing
>>> typing.List['']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.11/typing.py", line 362, in inner
    return cached(*args, **kwds)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/typing.py", line 1575, in __getitem__
    params = tuple(_type_check(p, msg) for p in params)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/typing.py", line 1575, in <genexpr>
    params = tuple(_type_check(p, msg) for p in params)
                   ^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/typing.py", line 186, in _type_check
    arg = _type_convert(arg, module=module, allow_special_forms=allow_special_forms)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/typing.py", line 164, in _type_convert
    return ForwardRef(arg, module=module, is_class=allow_special_forms)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/typing.py", line 859, in __init__
    if arg[0] == '*':
       ~~~^^^
IndexError: string index out of range

The construct is invalid, but I'd expect a more friendly error, something similar to

>>> typing.Dict[1]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.11/typing.py", line 365, in inner
    return func(*args, **kwds)
           ^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/typing.py", line 1576, in __getitem__
    _check_generic(self, params, self._nparams)
  File "/usr/lib/python3.11/typing.py", line 293, in _check_generic
    raise TypeError(f"Too {'many' if alen > elen else 'few'} arguments for {cls};"
TypeError: Too few arguments for typing.Dict; actual 1, expected 2

CPython versions tested on:

3.11

Operating systems tested on:

Linux

Linked PRs

Metadata

Metadata

Assignees

Labels

3.11only security fixes3.12only security fixes3.13bugs and security fixestopic-typingtype-bugAn unexpected behavior, bug, or error

Projects

No projects

Milestone

No milestone

Relationships

None yet

Development

No branches or pull requests

Issue actions

    pFad - Phonifier reborn

    Pfad - The Proxy pFad of © 2024 Garber Painting. All rights reserved.

    Note: This service is not intended for secure transactions such as banking, social media, email, or purchasing. Use at your own risk. We assume no liability whatsoever for broken pages.


    Alternative Proxies:

    Alternative Proxy

    pFad Proxy

    pFad v3 Proxy

    pFad v4 Proxy