All that’s needed to reproduce this is a file containing:

from typing import TypeVar

_ = TypeVar("tar.gz")

Then run pylint on this file. I get a stacktrace like:

************* Module example
example.py:1:0: C0114: Missing module docstring (missing-module-docstring)
Exception on node <AssignName._ l.3 at 0x7fe8c7586580> in file '/directory/example.py'
Traceback (most recent call last):
  File "/usr/local/venvs/test-venv/lib/python3.8/site-packages/astroid/inference_tip.py", line 37, in _inference_tip_cached
    result = _cache[func, node]
KeyError: (<function infer_typing_typevar_or_newtype at 0x7fe8c6442670>, <Call l.3 at 0x7fe8c7586640>)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/venvs/test-venv/lib/python3.8/site-packages/astroid/builder.py", line 168, in _data_build
    node, parser_module = _parse_string(data, type_comments=True)
  File "/usr/local/venvs/test-venv/lib/python3.8/site-packages/astroid/builder.py", line 454, in _parse_string
    parsed = parser_module.parse(data + "\n", type_comments=type_comments)
  File "/usr/local/venvs/test-venv/lib/python3.8/site-packages/astroid/_ast.py", line 49, in parse
    return parse_func(string)
  File "/usr/local/lib/python3.8/ast.py", line 47, in parse
    return compile(source, filename, mode, flags,
  File "<unknown>", line 10
    class tar.gz(metaclass=Meta):
             ^
SyntaxError: invalid syntax

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/local/venvs/test-venv/lib/python3.8/site-packages/pylint/checkers/utils.py", line 1258, in safe_infer
    value = next(infer_gen)
  File "/usr/local/venvs/test-venv/lib/python3.8/site-packages/astroid/nodes/node_ng.py", line 158, in infer
    results = list(self._explicit_inference(self, context, **kwargs))
  File "/usr/local/venvs/test-venv/lib/python3.8/site-packages/astroid/inference_tip.py", line 44, in _inference_tip_cached
    result = _cache[func, node] = list(func(*args, **kwargs))
  File "/usr/local/venvs/test-venv/lib/python3.8/site-packages/astroid/brain/brain_typing.py", line 127, in infer_typing_typevar_or_newtype
    node = extract_node(TYPING_TYPE_TEMPLATE.format(typename))
  File "/usr/local/venvs/test-venv/lib/python3.8/site-packages/astroid/builder.py", line 423, in extract_node
    tree = parse(code, module_name=module_name)
  File "/usr/local/venvs/test-venv/lib/python3.8/site-packages/astroid/builder.py", line 281, in parse
    return builder.string_build(code, modname=module_name, path=path)
  File "/usr/local/venvs/test-venv/lib/python3.8/site-packages/astroid/builder.py", line 138, in string_build
    module, builder = self._data_build(data, modname, path)
  File "/usr/local/venvs/test-venv/lib/python3.8/site-packages/astroid/builder.py", line 170, in _data_build
    raise AstroidSyntaxError(
astroid.exceptions.AstroidSyntaxError: Parsing Python code failed:
invalid syntax (<unknown>, line 10)

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/local/venvs/test-venv/lib/python3.8/site-packages/pylint/utils/ast_walker.py", line 90, in walk
    callback(astroid)
  File "/usr/local/venvs/test-venv/lib/python3.8/site-packages/pylint/checkers/base/name_checker/checker.py", line 411, in visit_assignname
    inferred_assign_type = utils.safe_infer(assign_type.value)
  File "/usr/local/venvs/test-venv/lib/python3.8/site-packages/pylint/checkers/utils.py", line 1262, in safe_infer
    raise AstroidError from e
astroid.exceptions.AstroidError
example.py:1:0: F0002: example.py: Fatal error while checking 'example.py'. Please open an issue in our bug tracker so we address this. There is a pre-filled template that you can use in '/home/vscode/.cache/pylint/pylint-crash-2022-09-12-15.txt'. (astroid-error)

AFAICT, nothing prevents creating a TypeVar with a period in the name, however, I believe it is implied that the name should be the name of a class, which cannot contain a period.

I think that’s what tripping up pylint.

There are 2 examples of FlyteFile’s in the flytekit repo that use periods in the typing of the FlyteFile: https://github.com/flyteorg/flytekit/blob/386626356ff2cb810733a29a51cf3d6351c8424d[…]flytekit-aws-sagemaker/flytekitplugins/awssagemaker/training.py https://github.com/flyteorg/flytekit/blob/8528268a29a07fe7e9ce9f7f08fea68c41b6a60b/tests/flytekit/unit/core/test_realworld_examples.py#L47

If I understand correctly this name is really not serving any functional purpose, but it is declaring/documenting the extension of the file. It seems a bit problematic to use TypeVar in this way, in the case of having multiple extension parts.