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1fe958c694
## Summary
Add support for implicit type aliases that use PEP 604 unions:
```py
IntOrStr = int | str
reveal_type(IntOrStr) # UnionType
def _(int_or_str: IntOrStr):
reveal_type(int_or_str) # int | str
```
## Typing conformance
The changes are either removed false positives, or new diagnostics due
to known limitations unrelated to this PR.
## Ecosystem impact
Spot checked, a mix of true positives and known limitations.
## Test Plan
New Markdown tests.
1.5 KiB
1.5 KiB
Union
Annotation
typing.Union can be used to construct union types in the same way as the | operator.
from typing import Union
a: Union[int, str]
a1: Union[int, bool]
a2: Union[int, Union[bytes, str]]
a3: Union[int, None]
a4: Union[Union[bytes, str]]
a5: Union[int]
a6: Union[()]
def f():
# revealed: int | str
reveal_type(a)
# Since bool is a subtype of int we simplify to int here. But we do allow assigning boolean values (see below).
# revealed: int
reveal_type(a1)
# revealed: int | bytes | str
reveal_type(a2)
# revealed: int | None
reveal_type(a3)
# revealed: bytes | str
reveal_type(a4)
# revealed: int
reveal_type(a5)
# revealed: Never
reveal_type(a6)
Assignment
from typing import Union
a: Union[int, str]
a = 1
a = ""
a1: Union[int, bool]
a1 = 1
a1 = True
# error: [invalid-assignment] "Object of type `Literal[b""]` is not assignable to `int | str`"
a = b""
Typing Extensions
from typing_extensions import Union
a: Union[int, str]
def f():
# revealed: int | str
reveal_type(a)
Invalid
from typing import Union
# error: [invalid-type-form] "`typing.Union` requires at least one argument when used in a type expression"
def f(x: Union) -> None:
reveal_type(x) # revealed: Unknown
Implicit type aliases using new-style unions
[environment]
python-version = "3.10"
X = int | str
def f(y: X):
reveal_type(y) # revealed: int | str