Crash Applying Generic Arguments

[saulshanabrook]

Crash Report

MyPy crashes when using type var tuple with multiple generic args in overload

Traceback

$ mypy tmp.py --show-traceback
tmp.py:34: 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: 1.11.0+dev.fb31409b392c5533b25173705d62ed385ee39cfb
Traceback (most recent call last):
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/__main__.py", line 15, in console_entry
    main()
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/main.py", line 100, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/main.py", line 182, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/build.py", line 192, in build
    result = _build(
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/build.py", line 266, in _build
    graph = dispatch(sources, manager, stdout)
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/build.py", line 2946, in dispatch
    process_graph(graph, manager)
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/build.py", line 3344, in process_graph
    process_stale_scc(graph, scc, manager)
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/build.py", line 3445, in process_stale_scc
    graph[id].type_check_first_pass()
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/build.py", line 2310, in type_check_first_pass
    self.type_checker().check_first_pass()
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/checker.py", line 481, in check_first_pass
    self.accept(d)
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/checker.py", line 589, in accept
    stmt.accept(self)
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/nodes.py", line 1310, in accept
    return visitor.visit_assignment_stmt(self)
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/checker.py", line 2850, in visit_assignment_stmt
    self.check_assignment(s.lvalues[-1], s.rvalue, s.type is None, s.new_syntax)
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/checker.py", line 3027, in check_assignment
    rvalue_type = self.check_simple_assignment(lvalue_type, rvalue, context=rvalue)
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/checker.py", line 4184, in check_simple_assignment
    rvalue_type = self.expr_checker.accept(
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/checkexpr.py", line 5760, in accept
    typ = node.accept(self)
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/nodes.py", line 1966, in accept
    return visitor.visit_index_expr(self)
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/checkexpr.py", line 4257, in visit_index_expr
    result = self.visit_index_expr_helper(e)
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/checkexpr.py", line 4271, in visit_index_expr_helper
    return self.accept(e.analyzed)
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/checkexpr.py", line 5760, in accept
    typ = node.accept(self)
          ^^^^^^^^^^^^^^^^^
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/nodes.py", line 2644, in accept
    return visitor.visit_type_alias_expr(self)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/checkexpr.py", line 4706, in visit_type_alias_expr
    return self.alias_type_in_runtime_context(alias.node, ctx=alias, alias_definition=True)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/checkexpr.py", line 4749, in alias_type_in_runtime_context
    return self.apply_type_arguments_to_callable(tp, item.args, ctx)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/checkexpr.py", line 4859, in apply_type_arguments_to_callable
    self.apply_generic_arguments(it, self.split_for_callable(it, args, ctx), ctx)
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/checkexpr.py", line 3205, in apply_generic_arguments
    return applytype.apply_generic_arguments(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/Caskroom/miniconda/base/envs/egg-smol-python/lib/python3.12/site-packages/mypy/applytype.py", line 97, in apply_generic_arguments
    assert min_arg_count <= len(orig_types) <= len(tvars)
AssertionError: 
tmp.py:34: : note: use --pdb to drop into pdb

To Reproduce

(I have commented out some lines which are unnecessary to reproduce the crash).
Create a tmp.py and run mypy tmp.py:

from collections.abc import Callable
from typing import Generic, TypeAlias, TypeVar, TypeVarTuple, Unpack, overload

T = TypeVar("T")
T1 = TypeVar("T1")
T2 = TypeVar("T2")
T3 = TypeVar("T3")
TS = TypeVarTuple("TS")


class PartialFn(Generic[T, Unpack[TS]]):
    @overload
    def __init__(self, f: Callable[[Unpack[TS]], T]) -> None: ...

    # @overload
    # def __init__(self, f: Callable[[T1, Unpack[TS]], T], _a: T1, /) -> None: ...

    # @overload
    # def __init__(self, f: Callable[[T1, T2, Unpack[TS]], T], _a: T1, _b: T2, /) -> None: ...

    @overload
    def __init__(self, f: Callable[[T1, T2, T3, Unpack[TS]], T], _a: T1, _b: T2, _c: T3, /) -> None: ...

    # etc, for partial application

    def __init__(self, f, *partial) -> None: ...

    # def __call__(self, *args: Unpack[TS]) -> T: ...


class Math: ...


MathFn: TypeAlias = PartialFn[Math, Math]

Your Environment

Mypy config from pyproject.toml:

[tool.mypy]
ignore_missing_imports = true
warn_redundant_casts = true
check_untyped_defs = true
strict_equality = true
warn_unused_configs = true
allow_redefinition = true
exclude = ["__snapshots__", "_build", "^conftest.py$"]

Mypy version (also fails on most recent released version):

$ mypy --version
mypy 1.11.0+dev.fb31409b392c5533b25173705d62ed385ee39cfb (compiled: no)
$ python --version
Python 3.12.1