Treat alternative syntax for unions (and other "new-semantics-old-syntax" typing features) in explicit `TypeAlias`es inside `if TYPE_CHECKING` blocks as stringized annotations.
还没有人认领这个 Issue。
评估
调研方向
从链接的 pyright-play 和 mypy-play 示例开始，重点关注 Python 3.9、TYPE_CHECKING 以及显式注释的 TypeAliases。目前没有确定任何 repository 文件或测试；只有在确定这些情况应如何解释的规范，并在相关类型检查工具中完成相应的共识或实现工作后，才能算完成。
由索引模型根据 Issue 内容生成。
描述
The Problem
At runtime, TYPE_CHECKING is always False, only type checkers assume it is True. Therefore, if TYPE_CHECKING blocks are only parsed, but never evaluated by the Python interpreter. Since A = int | str is a valid syntax for all still-supported Python versions at the moment (all versions ever since typing was introduced, actually), it would make sense if type checkers were allowed to accept usage of "new-semantics-old-syntax" features (like the alternative union syntax) in explicitly-annotated TypeAliases inside of if TYPE_CHECKING blocks as long as the Python version specified [project.requires-python] (or it's equivalent in tools) can successfully parse that syntax. This is essentially the same as treating explicitly-annotated TypeAliases as stringized annotations by-default.
Examples
# Run on 3.9
from typing import TYPE_CHECKING
if TYPE_CHECKING:
A = int | str # Alternative syntax for unions requires Python 3.10 or newer # pyright
# Invalid type alias: expression is not a valid type # mypy
# Unsupported left operand type for | ("type[int]") # mypy
# With proposal
from typing import TYPE_CHECKING
from typing_extensions import TypeAlias
if TYPE_CHECKING:
A: TypeAlias = int | str # Treated as a stringized annotation because `: TypeAlias`
# is explicit, therefore valid.
- 主要语言
- Python
- 星标
- 1.8k
- 派生
- 302
- 平均合并
- 23 小时
- 30 天内合并 PR
- 8
贡献指南
这个仓库没有索引到贡献指南
从这里开始
- 先读完整个 Issue，再读项目的贡献指南。
- 在 Issue 下留言说明你要接手 —— 这能避免两个人做同样的事。
- Fork 仓库，在一个分支上完成修改。
- 提交 Pull Request，并在描述里引用这个 Issue 编号。
python/typing 的其他 Issue
-
topic: typing spec
难度 2/5 1-3 小时 新手友好度 72/100
-
topic: typing spec
难度 2/5 1-3 小时 新手友好度 75/100
-
topic: documentation
难度 2/5 1-3 小时 新手友好度 76/100
-
topic: documentation
难度 2/5 1-3 小时 新手友好度 65/100
-
topic: conformance tests topic: typing spec
难度 3/5 1-2 天 新手友好度 72/100
相似的 Issue
-
essnmx good first issue
难度 1/5 1 小时以内 新手友好度 95/100
-
难度 2/5 1-3 小时 新手友好度 65/100
syfoud/Simulated_Scepter#174 ·
-
难度 2/5 1-3 小时 新手友好度 75/100
Giskard-AI/giskard-oss#2840 · 1 条评论 ·
-
A claim comment carrying the issue number is silently declined while the workflow reports success 未关闭area: repo bug perceived difficulty: 2
难度 2/5 1-3 小时 新手友好度 70/100
-
难度 2/5 1-3 小时 新手友好度 75/100
yeti-platform/yeti#1380 ·