Crash on sequence match statement in generic class with restricted type variable bound to sequence #18089
Description
Crash Report
mypy crashes when the following conditions are met:
- A generic class is present.
- The generic class refers to a typevar
Tthat is bound to a sequence. - The generic class has a method that attempts to pattern match a method parameter of type
T - One of the pattern matching cases is a sequence pattern such as
_, _.
This crash is similar to but distinct from this issue: #12448
Traceback
$ mypy mypy_mre.py --show-traceback
mypy_mre.py:7: 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: 1.14.0+dev.05a9e79068a5830e57264390c9f6bca859e92053
Traceback (most recent call last):
File "~/venv-3.11.6/bin/mypy", line 8, in <module>
sys.exit(console_entry())
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/__main__.py", line 15, in console_entry
main()
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/main.py", line 109, in main
res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/main.py", line 193, in run_build
res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/build.py", line 194, in build
result = _build(
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/build.py", line 269, in _build
graph = dispatch(sources, manager, stdout)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/build.py", line 2937, in dispatch
process_graph(graph, manager)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/build.py", line 3335, in process_graph
process_stale_scc(graph, scc, manager)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/build.py", line 3436, in process_stale_scc
graph[id].type_check_first_pass()
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/build.py", line 2306, in type_check_first_pass
self.type_checker().check_first_pass()
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checker.py", line 483, in check_first_pass
self.accept(d)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checker.py", line 592, in accept
stmt.accept(self)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/nodes.py", line 1196, in accept
return visitor.visit_class_def(self)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checker.py", line 2461, in visit_class_def
self.accept(defn.defs)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checker.py", line 592, in accept
stmt.accept(self)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/nodes.py", line 1277, in accept
return visitor.visit_block(self)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checker.py", line 2951, in visit_block
self.accept(s)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checker.py", line 592, in accept
stmt.accept(self)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/nodes.py", line 827, in accept
return visitor.visit_func_def(self)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checker.py", line 1046, in visit_func_def
self._visit_func_def(defn)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checker.py", line 1050, in _visit_func_def
self.check_func_item(defn, name=defn.name)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checker.py", line 1084, in check_func_item
self.check_func_def(defn, typ, name, allow_empty)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checker.py", line 1360, in check_func_def
self.accept(item.body)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checker.py", line 592, in accept
stmt.accept(self)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/nodes.py", line 1277, in accept
return visitor.visit_block(self)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checker.py", line 2951, in visit_block
self.accept(s)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checker.py", line 592, in accept
stmt.accept(self)
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/nodes.py", line 1661, in accept
return visitor.visit_match_stmt(self)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checker.py", line 5298, in visit_match_stmt
pattern_types = [self.pattern_checker.accept(p, subject_type) for p in s.patterns]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checker.py", line 5298, in <listcomp>
pattern_types = [self.pattern_checker.accept(p, subject_type) for p in s.patterns]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checkpattern.py", line 129, in accept
result = o.accept(self)
^^^^^^^^^^^^^^
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/patterns.py", line 93, in accept
return visitor.visit_sequence_pattern(self)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checkpattern.py", line 345, in visit_sequence_pattern
new_type = self.construct_sequence_child(current_type, new_inner_type)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "~/venv-3.11.6/lib/python3.11/site-packages/mypy/checkpattern.py", line 766, in construct_sequence_child
assert isinstance(proper_type, Instance)
AssertionError:
mypy_mre.py:7: : note: use --pdb to drop into pdb
To Reproduce
Here is an MRE:
from typing import Generic, TypeVar, Sequence, Any
T = TypeVar("T", bound=Sequence[Any])
class C(Generic[T]):
def f(self, x: T) -> None:
match x:
case _, _:
pass
case _:
passYour Environment
- Mypy version used: 1.14.0+dev.05a9e79068a5830e57264390c9f6bca859e92053 (current master)
- Mypy command-line flags: None
- Mypy configuration options from
mypy.ini(and other config files):
check_untyped_defs = true
disallow_any_generics = true
disallow_incomplete_defs = true
disallow_subclassing_any = true
disallow_untyped_calls = true
disallow_untyped_decorators = true
disallow_untyped_defs = true
extra_checks = true
no_implicit_reexport = true
python_version = "3.11"
strict_equality = true
warn_redundant_casts = true
warn_return_any = true
warn_unused_configs = true
warn_unused_ignores = true- Python version used: 3.11.6
- Operating system and version: AlmaLinux 9.4 under WSL 2 on Windows 10