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[ty] Fix false positives when subscripting an object inferred as having an Intersection type (#18920)

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Alex Waygood 2025-06-24 19:39:02 +01:00 • committed by GitHub
parent 3220242dec
commit e44c489273
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3 changed files with 52 additions and 18 deletions
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18
crates/ty_python_semantic/resources/mdtest/subscript/class.md
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@ -84,3 +84,21 @@ def _(flag: bool):
reveal_type(a) # revealed: str | Unknown
```
## Intersection of nominal-instance types
If a subscript operation could succeed for *any* positive element of an intersection, no diagnostic
should be reported even if it would not succeed for some other element of the intersection.
```py
class Foo: ...
class Bar:
def __getitem__(self, key: str) -> int:
return 42
def f(x: Foo):
if isinstance(x, Bar):
# TODO: should be `int`
reveal_type(x["whatever"]) # revealed: @Todo(Subscript expressions on intersections)
```

10
crates/ty_python_semantic/resources/mdtest/subscript/tuple.md
View file

@ -210,8 +210,12 @@ def test3(val: tuple[str] | tuple[int] | int):
### Intersection subscript access
```py
from ty_extensions import Intersection, Not
from ty_extensions import Intersection
def test4(val: Intersection[tuple[str], tuple[int]]):
reveal_type(val[0]) # revealed: str & int
class Foo: ...
class Bar: ...
def test4(val: Intersection[tuple[Foo], tuple[Bar]]):
# TODO: should be `Foo & Bar`
reveal_type(val[0]) # revealed: @Todo(Subscript expressions on intersections)
```