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Crash if a class is generic over a PEP-695 parameter that has the same name as an old-style TypeVar that is also in scope and the old-style TypeVar has a bound which uses an unquoted forward reference #18507
Description
Crash Report
This feels quite specific, but I think it may come up a surprising amount as more and more people use codemods to try to auto-upgrade their code to use PEP 695 in the coming years! Mypy crashes on this snippet:
from typing import TypeVar
T = TypeVar("T", bound=Foo)
class Foo: ...
class Bar[T]: ...The following things must all be true for the crash to occur:
- The global-scope TypeVar must have the same name as the type parameter used for
Bar - The global-scope TypeVar must have a
bound=argument that uses a forward reference - The forward reference in the global-scope TypeVar's bound must be unquoted. (For
.pyfiles, you generally need to quote all forward references, but this is not true for stubs.)
Traceback
% mypy foo.py --python-version=3.12 --show-traceback
foo.py:6: error: INTERNAL ERROR -- Please try using mypy master on GitHub:
https://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 1.15.0+dev.58de753b6b76227ff726e9ce1888cfc24c7ba44b
Traceback (most recent call last):
File "/Users/alexw/dev/typeshed/.venv/bin/mypy", line 8, in <module>
sys.exit(console_entry())
File "/Users/alexw/dev/mypy/mypy/__main__.py", line 15, in console_entry
main()
File "/Users/alexw/dev/mypy/mypy/main.py", line 119, in main
res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
File "/Users/alexw/dev/mypy/mypy/main.py", line 203, in run_build
res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
File "/Users/alexw/dev/mypy/mypy/build.py", line 191, in build
result = _build(
File "/Users/alexw/dev/mypy/mypy/build.py", line 267, in _build
graph = dispatch(sources, manager, stdout)
File "/Users/alexw/dev/mypy/mypy/build.py", line 2937, in dispatch
process_graph(graph, manager)
File "/Users/alexw/dev/mypy/mypy/build.py", line 3335, in process_graph
process_stale_scc(graph, scc, manager)
File "/Users/alexw/dev/mypy/mypy/build.py", line 3430, in process_stale_scc
mypy.semanal_main.semantic_analysis_for_scc(graph, scc, manager.errors)
File "/Users/alexw/dev/mypy/mypy/semanal_main.py", line 93, in semantic_analysis_for_scc
process_top_levels(graph, scc, patches)
File "/Users/alexw/dev/mypy/mypy/semanal_main.py", line 220, in process_top_levels
deferred, incomplete, progress = semantic_analyze_target(
File "/Users/alexw/dev/mypy/mypy/semanal_main.py", line 351, in semantic_analyze_target
analyzer.refresh_partial(
File "/Users/alexw/dev/mypy/mypy/semanal.py", line 646, in refresh_partial
self.refresh_top_level(node)
File "/Users/alexw/dev/mypy/mypy/semanal.py", line 657, in refresh_top_level
self.accept(d)
File "/Users/alexw/dev/mypy/mypy/semanal.py", line 7241, in accept
node.accept(self)
~~~~~~~~~~~^^^^^^
File "/Users/alexw/dev/mypy/mypy/nodes.py", line 1177, in accept
return visitor.visit_class_def(self)
~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
File "/Users/alexw/dev/mypy/mypy/semanal.py", line 1728, in visit_class_def
self.analyze_class(defn)
~~~~~~~~~~~~~~~~~~^^^^^^
File "/Users/alexw/dev/mypy/mypy/semanal.py", line 1869, in analyze_class
bases, tvar_defs, is_protocol = self.clean_up_bases_and_infer_type_variables(
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
defn, bases, context=defn
^^^^^^^^^^^^^^^^^^^^^^^^^
)
^
File "/Users/alexw/dev/mypy/mypy/semanal.py", line 2174, in clean_up_bases_and_infer_type_variables
assert isinstance(node.node, TypeVarLikeExpr)
~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError:To Reproduce
Paste the above snippet into a foo.py file and run mypy --python-version=3.12 foo.py --show-traceback
Your Environment
- Mypy version used:
1.15.0+dev.58de753b6b76227ff726e9ce1888cfc24c7ba44b - Mypy command-line flags:
--python-version=3.12 --show-traceback - Python version used: 3.13.1
Activity
AlexWaygood commentedon Jan 22, 2025
(Feel free to retitle the issue if you can think of something snappier...)
Allow type parameters reusing the name missing from current module (#…