## Summary
As-is, the following rejects `return self.value` in `def other` in the
subclass
([link](https://play.ty.dev/f55b47b2-313e-45d1-ba45-fde410bed32e))
because `self.value` is resolving to `Unknown | int | float | property`:
```python
class Base:
_value: float = 0.0
@property
def value(self) -> float:
return self._value
@value.setter
def value(self, v: float) -> None:
self._value = v
@property
def other(self) -> float:
return self.value
@other.setter
def other(self, v: float) -> None:
self.value = v
class Derived(Base):
@property
def other(self) -> float:
return self.value
@other.setter
def other(self, v: float) -> None:
reveal_type(self.value) # revealed: int | float
self.value = v
```
I believe the root cause is that we're not excluding properties when
searching for class methods, so we're treating the `other` setter as a
classmethod. I don't fully understand how that ends up materializing as
`| property` on the union though.
## Summary
If we match on an `TestEnum | None`, then when adding a case like
`~Literal[TestEnum.FOO]` (i.e., after `if value == TestEnum.FOO:
return`), we'd distribute `Literal[TestEnum.BAR]` on the entire builder,
creating `None & Literal[TestEnum.BAR]` which simplified to `Never`.
Instead, we should only expand to the remaining members for pieces of
the intersection that contain the enum.
Now, `(TestEnum | None) & ~Literal[TestEnum.FOO] &
~Literal[TestEnum.BAR]` correctly simplifies to `None` instead of
`Never`.
Closes https://github.com/astral-sh/ty/issues/2260.
## Summary
`apply_type_mapping` always expands type aliases and operates on the
resulting types, which can lead to cluttered results due to excessive
type alias expansion in places where it is not actually needed.
Specifically, type aliases are expanded when displaying method
signatures, because we use `TypeMapping::BindSelf` to get the method
signature.
```python
type Scalar = int | float
type Array1d = list[Scalar] | tuple[Scalar]
def f(x: Scalar | Array1d) -> None: pass
reveal_type(f) # revealed: def f(x: Scalar | Array1d) -> None
class Foo:
def f(self, x: Scalar | Array1d) -> None: pass
# should be `bound method Foo.f(x: Scalar | Array1d) -> None`
reveal_type(Foo().f) # revealed: bound method Foo.f(x: int | float | list[int | float] | tuple[int | float]) -> None
```
In this PR, when type mapping is performed on a type alias, the
expansion result without type mapping is compared with the expansion
result after type mapping, and if the two are equivalent, the expansion
is deemed redundant and canceled.
## Test Plan
mdtest updated
## Summary
Resolve(s) astral-sh/ty#117, astral-sh/ty#1569
Implement `typing.TypeGuard`. Due to the fact that it [overrides
anything previously known about the checked
value](https://typing.python.org/en/latest/spec/narrowing.html#typeguard)---
> When a conditional statement includes a call to a user-defined type
guard function, and that function returns true, the expression passed as
the first positional argument to the type guard function should be
assumed by a static type checker to take on the type specified in the
TypeGuard return type, unless and until it is further narrowed within
the conditional code block.
---we have to substantially rework the constraints system. In
particular, we make constraints represented as a disjunctive normal form
(DNF) where each term includes a regular constraint, and one or more
disjuncts with a typeguard constraint. Some test cases (including some
with more complex boolean logic) are added to `type_guards.md`.
## Test Plan
- update existing tests
- add new tests for more complex boolean logic with `TypeGuard`
- add new tests for `TypeGuard` variance
---------
Co-authored-by: Carl Meyer <carl@astral.sh>
