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Callback protocol with TypeVar defined in class body leads to crash later #12337

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kstauffer opened this issue Mar 11, 2022 · 0 comments · Fixed by #13526
Closed

Callback protocol with TypeVar defined in class body leads to crash later #12337

kstauffer opened this issue Mar 11, 2022 · 0 comments · Fixed by #13526
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crash topic-protocols

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@kstauffer
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kstauffer commented Mar 11, 2022 •
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Crash Report

Two simple programs trigger similar crashes. They both define & use a TypeVar within the body of a class, so that may be the common issue. First program:

from typing import *
class C(Protocol):
    T = TypeVar('T')
    def __call__(self, t: T) -> T:
        ...

def f(t: int) -> int:
    return t

g: C = f  # mypy crashes here

Second program:

from typing import *
class C(Protocol):
    T = TypeVar('T')
    def foo(self, t: T) -> T:
        ...

class D:
    def foo(self, t):
        return t

c: C = D()  # mypy crashes here

Traceback

First program:

a.py:10: 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: 0.950+dev.7ee84c71e851ce373d1824ecc09332caa373148c
a.py:10: : note: use --pdb to drop into pdb
Traceback (most recent call last):
  File "/tmp/venv/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
  File "/tmp/venv/lib/python3.10/site-packages/mypy/__main__.py", line 12, in console_entry
    main(None, sys.stdout, sys.stderr)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/main.py", line 96, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/main.py", line 173, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/build.py", line 180, in build
    result = _build(
  File "/tmp/venv/lib/python3.10/site-packages/mypy/build.py", line 256, in _build
    graph = dispatch(sources, manager, stdout)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/build.py", line 2727, in dispatch
    process_graph(graph, manager)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/build.py", line 3071, in process_graph
    process_stale_scc(graph, scc, manager)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/build.py", line 3169, in process_stale_scc
    graph[id].type_check_first_pass()
  File "/tmp/venv/lib/python3.10/site-packages/mypy/build.py", line 2186, in type_check_first_pass
    self.type_checker().check_first_pass()
  File "/tmp/venv/lib/python3.10/site-packages/mypy/checker.py", line 318, in check_first_pass
    self.accept(d)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/checker.py", line 424, in accept
    stmt.accept(self)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/nodes.py", line 1152, in accept
    return visitor.visit_assignment_stmt(self)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/checker.py", line 2193, in visit_assignment_stmt
    self.check_assignment(s.lvalues[-1], s.rvalue, s.type is None, s.new_syntax)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/checker.py", line 2354, in check_assignment
    rvalue_type = self.check_simple_assignment(lvalue_type, rvalue, context=rvalue,
  File "/tmp/venv/lib/python3.10/site-packages/mypy/checker.py", line 3281, in check_simple_assignment
    self.check_subtype(rvalue_type, lvalue_type, context, msg,
  File "/tmp/venv/lib/python3.10/site-packages/mypy/checker.py", line 5214, in check_subtype
    if is_subtype(subtype, supertype):
  File "/tmp/venv/lib/python3.10/site-packages/mypy/subtypes.py", line 94, in is_subtype
    return _is_subtype(left, right,
  File "/tmp/venv/lib/python3.10/site-packages/mypy/subtypes.py", line 151, in _is_subtype
    return left.accept(SubtypeVisitor(orig_right,
  File "/tmp/venv/lib/python3.10/site-packages/mypy/types.py", line 1328, in accept
    return visitor.visit_callable_type(self)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/subtypes.py", line 354, in visit_callable_type
    return self._is_subtype(left.fallback, right)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/subtypes.py", line 205, in _is_subtype
    return is_subtype(left, right,
  File "/tmp/venv/lib/python3.10/site-packages/mypy/subtypes.py", line 94, in is_subtype
    return _is_subtype(left, right,
  File "/tmp/venv/lib/python3.10/site-packages/mypy/subtypes.py", line 151, in _is_subtype
    return left.accept(SubtypeVisitor(orig_right,
  File "/tmp/venv/lib/python3.10/site-packages/mypy/types.py", line 1065, in accept
    return visitor.visit_instance(self)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/subtypes.py", line 286, in visit_instance
    if right.type.is_protocol and is_protocol_implementation(left, right):
  File "/tmp/venv/lib/python3.10/site-packages/mypy/subtypes.py", line 588, in is_protocol_implementation
    assert supertype is not None
AssertionError:

Second program crashes like this (almost the same, except frames of the first crash -8:-4 are absent in this stack:

b.py:11: 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: 0.950+dev.7ee84c71e851ce373d1824ecc09332caa373148c
b.py:11: : note: use --pdb to drop into pdb
Traceback (most recent call last):
  File "/tmp/venv/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
  File "/tmp/venv/lib/python3.10/site-packages/mypy/__main__.py", line 12, in console_entry
    main(None, sys.stdout, sys.stderr)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/main.py", line 96, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/main.py", line 173, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/build.py", line 180, in build
    result = _build(
  File "/tmp/venv/lib/python3.10/site-packages/mypy/build.py", line 256, in _build
    graph = dispatch(sources, manager, stdout)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/build.py", line 2727, in dispatch
    process_graph(graph, manager)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/build.py", line 3071, in process_graph
    process_stale_scc(graph, scc, manager)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/build.py", line 3169, in process_stale_scc
    graph[id].type_check_first_pass()
  File "/tmp/venv/lib/python3.10/site-packages/mypy/build.py", line 2186, in type_check_first_pass
    self.type_checker().check_first_pass()
  File "/tmp/venv/lib/python3.10/site-packages/mypy/checker.py", line 318, in check_first_pass
    self.accept(d)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/checker.py", line 424, in accept
    stmt.accept(self)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/nodes.py", line 1152, in accept
    return visitor.visit_assignment_stmt(self)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/checker.py", line 2193, in visit_assignment_stmt
    self.check_assignment(s.lvalues[-1], s.rvalue, s.type is None, s.new_syntax)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/checker.py", line 2354, in check_assignment
    rvalue_type = self.check_simple_assignment(lvalue_type, rvalue, context=rvalue,
  File "/tmp/venv/lib/python3.10/site-packages/mypy/checker.py", line 3281, in check_simple_assignment
    self.check_subtype(rvalue_type, lvalue_type, context, msg,
  File "/tmp/venv/lib/python3.10/site-packages/mypy/checker.py", line 5214, in check_subtype
    if is_subtype(subtype, supertype):
  File "/tmp/venv/lib/python3.10/site-packages/mypy/subtypes.py", line 94, in is_subtype
    return _is_subtype(left, right,
  File "/tmp/venv/lib/python3.10/site-packages/mypy/subtypes.py", line 151, in _is_subtype
    return left.accept(SubtypeVisitor(orig_right,
  File "/tmp/venv/lib/python3.10/site-packages/mypy/types.py", line 1065, in accept
    return visitor.visit_instance(self)
  File "/tmp/venv/lib/python3.10/site-packages/mypy/subtypes.py", line 286, in visit_instance
    if right.type.is_protocol and is_protocol_implementation(left, right):
  File "/tmp/venv/lib/python3.10/site-packages/mypy/subtypes.py", line 588, in is_protocol_implementation
    assert supertype is not None
AssertionError:

Your Environment

  • Mypy version used: Github master 0.950+dev.7ee84c71e851ce373d1824ecc09332caa373148c
  • Mypy command-line flags: mypy a.py --show-traceback a.py
  • Mypy configuration options from mypy.ini (and other config files): None
  • Python version used: 3.10
  • Operating system and version: WSL Ubuntu 20.04
@AlexWaygood AlexWaygood mentioned this issue Jul 3, 2022
Closed
@ilevkivskyi ilevkivskyi mentioned this issue Aug 26, 2022
Merged
ilevkivskyi added a commit that referenced this issue Aug 26, 2022
@ilevkivskyi
Fix crashes on special forms in protocol bodies (#13526)
fd6760c 
Fixes #6801
Fixes #10577
Fixes #12642
Fixes #12337
Fixes #10639 
Fixes #13390 

All these crashes are in a sense duplicates of each other. Fix is trivial, except I decided to ban type aliases in protocol bodies. Already in the examples in issues, I have found two cases where people wrote `foo = list[str]`, where they clearly wanted `foo: list[str]`. This can cause hard to spot false negatives.
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Fix crashes on special forms in protocol bodies ilevkivskyi/mypy
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@kstauffer @AlexWaygood