## Summary
Fixes https://github.com/astral-sh/ty/issues/2565.
This PR adds support for `if type(x) is Y` narrowing where `Y` is a
subclass-of type, type-alias type, or typevar type.
## Test Plan
mdtests
## Summary
fixes: https://github.com/astral-sh/ty/issues/1838
This PR adds basic support for overloaded function when used to
specialize a `ParamSpec` type variable.
Following cases are still remaining:
1. Updating the specialization with the matching overload after the
paramspec sub-call logic
2. Updating the specialization with the matching overload using the
return type
Both of these cases are present in the mdtest file.
## Test Plan
Update mdtest with new cases.
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---------
Co-authored-by: Brent Westbrook <36778786+ntBre@users.noreply.github.com>
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## Summary
Negative subscripts are also indicative of a thing being subcriptable:
```python
class Subscriptable:
def __getitem__(self, key: int) -> int:
return 42
class NotSubscriptable: ...
def _(x: list[Subscriptable | NotSubscriptable]):
if not isinstance(x[-1], NotSubscriptable):
# After narrowing, x[-1] excludes NotSubscriptable, which means subscripting works
reveal_type(x[-1]) # revealed: Subscriptable & ~NotSubscriptable
reveal_type(x[-1][0]) # revealed: int
```
## Summary
Fixes some TODOs introduced in #22672 around cases like the following:
```python
from collections import namedtuple
from dataclasses import dataclass
NT = namedtuple("NT", "x y")
# error: [invalid-dataclass] "Cannot use `dataclass()` on a `NamedTuple` class"
dataclass(NT)
```
On main, `dataclass(NT)` emits `# error: [no-matching-overload]`
instead, which is wrong -- the overload does match! On main, the logic
proceeds as follows:
1. `dataclass` has two overloads:
- `dataclass(cls: type[_T], ...) -> type[_T]`
- `dataclass(cls: None = None, ...) -> Callable[[type[_T]], type[_T]]`
2. When `dataclass(NT)` is called:
- Arity check: Both overloads accept one positional argument, so both
pass.
- Type checking on first overload: `NT` matches `type[_T]`... but then
`invalid_dataclass_target()` runs and adds `InvalidDataclassApplication`
error
- Type checking on second overload: `NT` doesn't match `None`, so we
have a type error.
3. After type checking, both overloads have errors.
4. `matching_overload_index()` filters by
`overload.as_result().is_ok()`, which checks if `errors.is_empty()`.
Since both overloads have errors, neither matches...
5. We emit the "No overload matches arguments" error.
Instead, we now differentiate between non-matching errors, and errors
that occur when we _do_ match, but the call has some other semantic
failure.
## Summary
Consider `x: str | bytes` and then `x.split(" ")`. Because we have a
union, and at least one variant errors (`bytes` expects a `Buffer`, not
a `str`), we call `binding.report_diagnostics` for each variant. For the
`str` variant, it has two overloads that both match arity, but only one
actually matches the signature... So
`matching_overload_before_type_checking` is `None` (because they both
match arity), but we don't actually have an error, and we fall through
to `NO_MATCHING_OVERLOAD`.
If one variant succeeds, we should avoid reporting errors for it, even
if not _all_ variants matched.
