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Type "int" cannot be assigned to type "Comparable" #2346

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desktable opened this issue Feb 7, 2022 · 2 comments
Closed

Type "int" cannot be assigned to type "Comparable" #2346

desktable opened this issue Feb 7, 2022 · 2 comments
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@desktable
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desktable commented Feb 7, 2022 •
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Environment data

  • Language Server version: 2022.2.0
  • OS and version: linux x64 (Ubuntu 20.04)
  • Python version (and distribution if applicable, e.g. Anaconda): 3.9.7
  • python.analysis.indexing: null
  • python.analysis.typeCheckingMode: basic

Expected behaviour

No error.

Actual behaviour

Pylance reports the following errors on the line func(a, b):

(variable) a: Literal[1]
Argument of type "Literal[1]" cannot be assigned to parameter "x" of type "CT@_func" in function "_func"
  Type "int" cannot be assigned to type "Comparable"Pylance[reportGeneralTypeIssues](https://github.com/microsoft/pylance-release/blob/main/DIAGNOSTIC_SEVERITY_RULES.md#diagnostic-severity-rules)

(variable) b: Literal[2]
Argument of type "Literal[2]" cannot be assigned to parameter "y" of type "CT@func" in function "func"
  Type "int" cannot be assigned to type "Comparable"Pylance[reportGeneralTypeIssues](https://github.com/microsoft/pylance-release/blob/main/DIAGNOSTIC_SEVERITY_RULES.md#diagnostic-severity-rules)

Logs

[Info  - 9:26:47 AM] (3321373) Pylance language server 2022.2.0 (pyright 65946fc7) starting
[Info  - 9:26:47 AM] (3321373) Server root directory: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist
[Info  - 9:26:47 AM] (3321373) No pyproject.toml file found.
[Info  - 9:26:47 AM] (3321373) Setting pythonPath for service "<default>": "/home/desktable/.pyenv/versions/3.9.7/bin/python"
[Warn  - 9:26:47 AM] (3321373) stubPath typings is not a valid directory.
[Info  - 9:26:47 AM] (3321373) Assuming Python version 3.9
[Info  - 9:26:47 AM] (3321373) Assuming Python platform Linux
[Info  - 9:26:47 AM] (3321373) Search paths for <default>
[Info  - 9:26:47 AM] (3321373)   /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib
[Info  - 9:26:47 AM] (3321373)   typings
[Info  - 9:26:47 AM] (3321373)   /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stubs/...
[Info  - 9:26:47 AM] (3321373)   /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/bundled/stubs
[Info  - 9:26:47 AM] (3321373)   /home/desktable/.pyenv/versions/3.9.7/lib/python3.9
[Info  - 9:26:47 AM] (3321373)   /home/desktable/.pyenv/versions/3.9.7/lib/python3.9/lib-dynload
[Info  - 9:26:47 AM] (3321373)   /home/desktable/.pyenv/versions/3.9.7/lib/python3.9/site-packages
[Info  - 9:26:47 AM] (3321373) Adding fs watcher for library directories:
 /home/desktable/.pyenv/versions/3.9.7/lib/python3.9
/home/desktable/.pyenv/versions/3.9.7/lib/python3.9/lib-dynload
/home/desktable/.pyenv/versions/3.9.7/lib/python3.9/site-packages
[Warn  - 9:26:48 AM] (3321373) Exception received when installing file system watcher: TypeError [ERR_FEATURE_UNAVAILABLE_ON_PLATFORM]: The feature watch recursively is unavailable on the current platform, which is being used to run Node.js
[Warn  - 9:26:48 AM] (3321373) Exception received when installing file system watcher: TypeError [ERR_FEATURE_UNAVAILABLE_ON_PLATFORM]: The feature watch recursively is unavailable on the current platform, which is being used to run Node.js
[Warn  - 9:26:48 AM] (3321373) Exception received when installing file system watcher: TypeError [ERR_FEATURE_UNAVAILABLE_ON_PLATFORM]: The feature watch recursively is unavailable on the current platform, which is being used to run Node.js
[Warn  - 9:26:48 AM] (3321373) Exception received when installing file system watcher: TypeError [ERR_FEATURE_UNAVAILABLE_ON_PLATFORM]: The feature watch recursively is unavailable on the current platform, which is being used to run Node.js
[Info  - 9:26:48 AM] (3321373) Searching for source files
[Info  - 9:26:48 AM] (3321373) No source files found.
(3321373) [IDX(FG)] index libraries  (index) ...
(3321373) [IDX(FG)]   read stdlib indices (33ms)
(3321373) [IDX(FG)] index libraries  (index) [succeed] (33ms)
[Info  - 9:26:48 AM] (3321373) Background analysis(1) root directory: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist
[Info  - 9:26:48 AM] (3321373) Background analysis(1) started
(3321373) Background analysis message: setConfigOptions
(3321373) Background analysis message: setImportResolver
(3321373) Background analysis message: ensurePartialStubPackages
(3321373) Background analysis message: setTrackedFiles
(3321373) Background analysis message: markAllFilesDirty
(3321373) Background analysis message: setFileOpened
(3321373) [FG] parsing: /home/desktable/play_comparable.py (18ms)
(3321373) [FG] parsing: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/builtins.pyi [fs read 2ms] (104ms)
(3321373) [FG] binding: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/builtins.pyi (31ms)
(3321373) [FG] binding: /home/desktable/play_comparable.py (0ms)
(3321373) Background analysis message: getDiagnosticsForRange
(3321373) Background analysis message: getDiagnosticsForRange
(3321373) Background analysis message: analyze
(3321373) [BG(1)] analyzing: /home/desktable/play_comparable.py ...
(3321373) [BG(1)]   parsing: /home/desktable/play_comparable.py (51ms)
(3321373) [BG(1)]   parsing: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/builtins.pyi [fs read 3ms] (111ms)
(3321373) [BG(1)]   binding: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/builtins.pyi (31ms)
(3321373) [BG(1)]   binding: /home/desktable/play_comparable.py (0ms)
(3321373) [BG(1)]   checking: /home/desktable/play_comparable.py ...
(3321373) [BG(1)]     parsing: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/typing_extensions.pyi [fs read 1ms] (7ms)
(3321373) [BG(1)]     binding: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/typing_extensions.pyi (2ms)
(3321373) [BG(1)]     parsing: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/typing.pyi [fs read 0ms] (19ms)
(3321373) [BG(1)]     binding: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/typing.pyi (9ms)
(3321373) [BG(1)]     parsing: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/_typeshed/__init__.pyi [fs read 0ms] (11ms)
(3321373) [BG(1)]     binding: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/_typeshed/__init__.pyi (1ms)
(3321373) [BG(1)]     parsing: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/abc.pyi [fs read 0ms] (1ms)
(3321373) [BG(1)]     binding: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/abc.pyi (0ms)
(3321373) [BG(1)]   checking: /home/desktable/play_comparable.py (87ms)
(3321373) [BG(1)] analyzing: /home/desktable/play_comparable.py (282ms)
(3321373) Background analysis message: resumeAnalysis
(3321373) Background analysis message: getDiagnosticsForRange
(3321373) Background analysis message: getDiagnosticsForRange
(3321373) Background analysis message: getDiagnosticsForRange
(3321373) Background analysis message: getDiagnosticsForRange
(3321373) Background analysis message: getDiagnosticsForRange
(3321373) Background analysis message: getDiagnosticsForRange
(3321373) Background analysis message: getDiagnosticsForRange
(3321373) Background analysis message: getDiagnosticsForRange
(3321373) Background analysis message: setFileOpened
(3321373) Background analysis message: markFilesDirty
(3321373) [FG] parsing: /home/desktable/play_comparable.py (14ms)
(3321373) [FG] binding: /home/desktable/play_comparable.py (1ms)
(3321373) Background analysis message: analyze
(3321373) [BG(1)] analyzing: /home/desktable/play_comparable.py ...
(3321373) [BG(1)]   parsing: /home/desktable/play_comparable.py (2ms)
(3321373) [BG(1)]   binding: /home/desktable/play_comparable.py (1ms)
(3321373) [BG(1)]   checking: /home/desktable/play_comparable.py (12ms)
(3321373) [BG(1)] analyzing: /home/desktable/play_comparable.py (15ms)
(3321373) Background analysis message: resumeAnalysis
(3321373) [FG] parsing: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/typing_extensions.pyi [fs read 1ms] (22ms)
(3321373) [FG] binding: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/typing_extensions.pyi (3ms)
(3321373) [FG] parsing: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/typing.pyi [fs read 0ms] (48ms)
(3321373) [FG] binding: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/typing.pyi (11ms)
(3321373) [FG] parsing: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/_typeshed/__init__.pyi [fs read 0ms] (15ms)
(3321373) [FG] binding: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/_typeshed/__init__.pyi (3ms)
(3321373) [FG] parsing: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/abc.pyi [fs read 1ms] (4ms)
(3321373) [FG] binding: /home/desktable/.vscode-server/extensions/ms-python.vscode-pylance-2022.2.0/dist/typeshed-fallback/stdlib/abc.pyi (0ms)
(3321373) Background analysis message: getDiagnosticsForRange
(3321373) Background analysis message: getDiagnosticsForRange
(3321373) Background analysis message: setFileOpened
(3321373) Background analysis message: markFilesDirty
(3321373) [FG] parsing: /home/desktable/play_comparable.py (2ms)
(3321373) [FG] binding: /home/desktable/play_comparable.py (1ms)
(3321373) Background analysis message: getDiagnosticsForRange
(3321373) Background analysis message: getDiagnosticsForRange
(3321373) Background analysis message: analyze
(3321373) [BG(1)] analyzing: /home/desktable/play_comparable.py ...
(3321373) [BG(1)]   parsing: /home/desktable/play_comparable.py (3ms)
(3321373) [BG(1)]   binding: /home/desktable/play_comparable.py (1ms)
(3321373) [BG(1)]   checking: /home/desktable/play_comparable.py (22ms)
(3321373) [BG(1)] analyzing: /home/desktable/play_comparable.py (26ms)
(3321373) Background analysis message: resumeAnalysis
(3321373) Background analysis message: getDiagnosticsForRange
(3321373) Background analysis message: getDiagnosticsForRange

Code Snippet / Additional information

from abc import abstractmethod
from typing import Protocol, TypeVar

CT = TypeVar("CT", bound="Comparable")


class Comparable(Protocol):
    """Generic comparable class"""

    @abstractmethod
    def __lt__(self: CT, other: CT) -> bool:
        ...


def func(x: CT, y: CT) -> bool:
    return x < y

a: int = 1
b: int = 2
func(a, b)  # pylance (incorrectly??) reports type issues on this line
@github-actions github-actions bot added the triage label Feb 7, 2022
@desktable desktable changed the title Pylance incorrectly states: Type "int" cannot be assigned to type "Comparable" Type "int" cannot be assigned to type "Comparable" Feb 7, 2022
@erictraut
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erictraut commented Feb 7, 2022 •
edited
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The problem is that your protocol class defines a method __lt__ that has a parameter named other, and that parameter can be specified by keyword. However, the int class defines this same parameter as positional-only.

If func were to call this method with a keyword argument, it would crash at runtime.

def func(x: CT, y: CT) -> bool:
    return x.__lt__(other=y) # Crash if `int` is passed

If you attempt to assign an int value to a simple variable that is annotated with `Comparable, you'll see a more detailed error message that describes the problem.

x: Comparable = a
Expression of type "Literal[1]" cannot be assigned to declared type "Comparable"
  "Literal[1]" is incompatible with protocol "Comparable"
    "__lt__" is an incompatible type
      Type "(__x: int) -> bool" cannot be assigned to type "(other: int) -> bool"
        Position-only parameter mismatch; expected 1 but received 0

You can fix this by doing one of the following.

    # This uses the "old style" way of specifying a position-only parameter
    # by using a double underscore.
    @abstractmethod
    def __lt__(self: CT, __other: CT) -> bool:
        ...

or

    # This uses the newer mechanism introduced in PEP 570.
    @abstractmethod
    def __lt__(self: CT, other: CT, /) -> bool:
        ...

@desktable
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desktable commented Feb 7, 2022 •
edited
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Thank you for the quick response! Confirming that adding "/" to the __lt__ definition fixes the issue.

@judej judej added the reference label Feb 7, 2022
@github-actions github-actions bot removed the triage label Feb 7, 2022
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@desktable @judej @erictraut