8000 `match` crashes on Union of Tuple and non-Tuple · Issue #12533 · python/mypy · GitHub
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bkovitz opened this issue Apr 6, 2022 · 8 comments · Fixed by #13514
Closed

match crashes on Union of Tuple and non-Tuple #12533

bkovitz opened this issue Apr 6, 2022 · 8 comments · Fixed by #13514
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crash topic-match-statement Python 3.10's match statement

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@bkovitz
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bkovitz commented Apr 6, 2022 •
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Crash Report

mypy 0.942 crashes when the match expression in a match statement is a Union of a Tuple type and a non-tuple type.

Traceback

$ mypy --python-version 3.10 --show-traceback x.py
x.py:14: 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: 0.942
Traceback (most recent call last):
  File "mypy/checker.py", line 424, in accept
  File "mypy/nodes.py", line 1405, in accept
  File "mypy/checker.py", line 4110, in visit_match_stmt
  File "mypy/checkpattern.py", line 107, in accept
  File "mypy/patterns.py", line 87, in accept
  File "mypy/checkpattern.py", line 301, in visit_sequence_pattern
  File "mypy/checkpattern.py", line 656, in construct_sequence_child
  File "mypy/checkpattern.py", line 663, in construct_sequence_child
AssertionError: 
x.py:14: : note: use --pdb to drop into pdb

To Reproduce

from typing import Union

def func(e: Union[str, tuple[str]]) -> None:
    match e:
        case (a,) if isinstance(a, str):
            print('HERE', e)

Notes

If we change the type of the tuple inside the Union to a tuple with no contents specified, like this:

def func(e: Union[str, tuple]) -> None:

then there is no crash.

This might be due to the same underlying bug as #12532.

Environment

  • Mypy version used: 0.942
  • Mypy command-line flags: --python-version 3.10 --show-traceback x.py
  • Mypy configuration options from mypy.ini (and other config files): (none)
  • Python version used: 3.10.2
  • Operating system and version: Ubuntu 18.04
@bkovitz bkovitz added the crash label Apr 6, 2022
@AlexWaygood AlexWaygood added the topic-match-statement Python 3.10's match statement label Apr 6, 2022
@MartinNowak
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MartinNowak commented Apr 22, 2022 8000

I have a similar, but slightly different case triggering this.

        match cast(results.get(table_ref), tuple[str, int | None]):
            case _, None:
                return f"`{table_ref.undecorated}{m['alias'] or ''}`"
            case _, snapshotTime:
                return f"`{table_ref.undecorated}{m['alias'] or ''}` FOR SYSTEM_TIME AS OF TIMESTAMP_MILLIS({snapshotTime})"
            case None:
                return m[0]
            case table_info:
                raise NotImplementedError(f"Unexpected table info {table_info}")

Will try to reduce this test case further when I find some time :/.

@Artemis21
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Artemis21 commented Apr 25, 2022 •
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Minimised test case:

foo: tuple[int] | None
match foo:
    case x,: pass

@JelleZijlstra JelleZijlstra mentioned this issue May 16, 2022
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@gertvdijk
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Similar if not identical traceback with union of tuples (so not just non-tuple):

import ipaddress
from typing import Literal

from typing_extensions import reveal_type

fam = Literal["4", "u"]

myvar: tuple[fam, ipaddress.IPv4Address] | tuple[fam, str] = ("u", "/mysock")

match myvar:
    case ("u", socket_path):
        reveal_type(socket_path)
    case ("4", ip):
        reveal_type(ip)
mypyerror.py:12: 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: 0.961
Traceback (most recent call last):
  File "mypy/checker.py", line 431, in accept
  File "mypy/nodes.py", line 1415, in accept
  File "mypy/checker.py", line 4155, in visit_match_stmt
  File "mypy/checkpattern.py", line 104, in accept
  File "mypy/patterns.py", line 87, in accept
  File "mypy/checkpattern.py", line 300, in visit_sequence_pattern
  File "mypy/checkpattern.py", line 651, in construct_sequence_child
  File "mypy/checkpattern.py", line 658, in construct_sequence_child
AssertionError: 
mypyerror.py:12: : note: use --pdb to drop into pdb

@JelleZijlstra JelleZijlstra mentioned this issue Jul 21, 2022
Closed
@AlexWaygood AlexWaygood mentioned this issue Aug 12, 2022
Closed
@ilevkivskyi ilevkivskyi mentioned this issue Aug 25, 2022
Merged
@sparkiegeek
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With #13514 landing in master, I thought it would be worth trying a development build of mypy which was crashing for me with what I believe to be this bug.

I can confirm that mypy no longer crashes, but it also seems to have lost typing information for variables assigned in the match statement.

I have tried to simplify down my complex scenario to a simple reproducer

from typing import Literal, TypeAlias

CreateOp: TypeAlias = tuple[Literal[1], list]
DeleteOp: TypeAlias = tuple[Literal[2], list]
Ops: TypeAlias = list[CreateOp | DeleteOp]
# No issue when Ops isn't a Union
#Ops: TypeAlias = list[CreateOp]


changes: Ops = []
for change in changes:
    match change:
        case [1, target]:
            reveal_type(target)
            target.append(1)

Running the above through mypy 0.942 causes a crash, and with master outputs the following:

$ mypy test_mypy.py 
test_mypy.py:14: note: Revealed type is "builtins.object"
test_mypy.py:15: error: "object" has no attribute "append"
Found 1 error in 1 file (checked 1 source file)

By switching around the definition of Ops to the commented one, mypy passes and the Revealed type is builtins.list[Any] as expected

@antonagestam
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@sparkiegeek FWIW, that sounds exactly like what is pointed out in a TODO in the merged PR, here:

https://github.com/python/mypy/pull/13514/files#diff-9100781e1e8bb8997aa611cce8014d8680677e036e9652d59fbd86336f80c3feR1624

@sparkiegeek
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@sparkiegeek FWIW, that sounds exactly like what is pointed out in a TODO in the merged PR, here:

https://github.com/python/mypy/pull/13514/files#diff-9100781e1e8bb8997aa611cce8014d8680677e036e9652d59fbd86336f80c3feR1624

Possibly, but if it were that, then wouldn't my reproducer have an inferred type of Union[builtins.list, builtins.list] (AKA builtins.list) and not builtins.object? Since both of the potential types of an 'Op' have the same type after the Literal

@hauntsaninja
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Btw, is the project you encountered this on open source? If so, I can add it to https://github.com/hauntsaninja/mypy_primer

@bkovitz
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bkovitz commented Sep 25, 2022

@hauntsaninja The project where I ran into this issue is: https://github.com/bkovitz/FARGish
It's an open-source project, but the directories are a mess right now—lots of old versions—and there's no good written explanation of what it does. You're welcome to list it, though.

@AlexWaygood AlexWaygood mentioned this issue Oct 26, 2022
Closed
@ahiuchingau ahiuchingau mentioned this issue Nov 15, 2024
Merged
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Fix match crash on unions including tuples ilevkivskyi/mypy
8 participants
@antonagestam @sparkiegeek @MartinNowak @gertvdijk @bkovitz @hauntsaninja @Artemis21 @AlexWaygood
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