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DetachHead opened this issue Nov 1, 2021 · 3 comments · Fixed by #14008
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new union syntax doesn't work on Literals #11426

DetachHead opened this issue Nov 1, 2021 · 3 comments · Fixed by #14008
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bug mypy got something wrong topic-pep-604 PEP 604 (union | operator) topic-type-alias TypeAlias and other type alias issues

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@DetachHead
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from __future__ import annotations

from typing import Literal

Foo = Literal[1, 2]

Bar = Foo | Literal[3] # error: Unsupported left operand type for | ("object")

https://mypy-play.net/?mypy=latest&python=3.10&gist=3a429dfa3e9e3b692aac25887027ab69
@DetachHead DetachHead added the bug mypy got something wrong label Nov 1, 2021
@sobolevn
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sobolevn commented Nov 1, 2021 •
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This also happens without __future__ import, python3.9:

from typing import Literal

Foo = Literal[1, 2]
Bar = Foo | Literal[3]
# error: Invalid type alias: expression is not a valid type
# error: Unsupported left operand type for | ("object")

Will fix it right now, thanks!

@sobolevn
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sobolevn commented Nov 1, 2021

On python3.10 it generates a single error:

» mypy out/ex.py --show-traceback
out/ex.py:4: error: Unsupported left operand type for | ("object")

@sobolevn sobolevn mentioned this issue Nov 1, 2021
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@JelleZijlstra
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On 3.9 without the import the error is correct since | doesn't work at runtime in 3.9. But it should not error in 3.10 or with the future import on, or in stringified annotations.

@DetachHead DetachHead mentioned this issue Feb 22, 2022
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@KotlinIsland KotlinIsland mentioned this issue Mar 17, 2022
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@JelleZijlstra JelleZijlstra added the topic-pep-604 PEP 604 (union | operator) label Mar 19, 2022
@AlexWaygood AlexWaygood added the topic-type-alias TypeAlias and other type alias issues label Mar 24, 2022
JukkaL added a commit that referenced this issue Nov 4, 2022
@JukkaL
Fix new style union syntax in type aliases
5856657 
Fix Python 3.10 `|` union syntax in type aliases, when one of
the operands is a type alias or a type with an overloaded `__init__`.

Fixes #12368. Fixes #12005. Fixes #11426.
@JukkaL JukkaL mentioned this issue Nov 4, 2022
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JukkaL added a commit that referenced this issue Nov 7, 2022
@JukkaL
Fix new style union syntax in type aliases (#14008)
39d35cd 
Fix Python 3.10 `|` union syntax in type aliases, when one of
the operands is a type alias or a type with an overloaded `__init__`.

We can now infer `typing._SpecialForm` for type aliases in a runtime 
context.

Also create a bunch of minimal test-only stubs for stdlib modules 
to fix some test failures caused by the missing `typing._SpecialForm`
in the default test stubs. This is generally what we want in any case, 
since using typeshed stubs with minimal builtins/typing stubs can
result in unpredictable behavior and slow tests.

Fixes #12368. Fixes #12005. Fixes #11426.
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Fix new style union syntax in type aliases python/mypy
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@JelleZijlstra @sobolevn @DetachHead @AlexWaygood