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b30d97e5e0
## Summary
Adds validation to subscript assignment expressions.
```py
class Foo: ...
class Bar:
__setattr__ = None
class Baz:
def __setitem__(self, index: str, value: int) -> None:
pass
# We now emit a diagnostic on these statements
Foo()[1] = 2
Bar()[1] = 2
Baz()[1] = 2
```
Also improves error messages on invalid `__getitem__` expressions
## Test Plan
Update mdtests and add more to `subscript/instance.md`
---------
Co-authored-by: David Peter <sharkdp@users.noreply.github.com>
Co-authored-by: David Peter <mail@david-peter.de>
2.4 KiB
2.4 KiB
Instance subscript
__getitem__ unbound
class NotSubscriptable: ...
a = NotSubscriptable()[0] # error: "Cannot subscript object of type `NotSubscriptable` with no `__getitem__` method"
__getitem__ not callable
class NotSubscriptable:
__getitem__ = None
# error: "Method `__getitem__` of type `Unknown | None` is possibly not callable on object of type `NotSubscriptable`"
a = NotSubscriptable()[0]
Valid __getitem__
class Identity:
def __getitem__(self, index: int) -> int:
return index
reveal_type(Identity()[0]) # revealed: int
__getitem__ union
def _(flag: bool):
class Identity:
if flag:
def __getitem__(self, index: int) -> int:
return index
else:
def __getitem__(self, index: int) -> str:
return str(index)
reveal_type(Identity()[0]) # revealed: int | str
__getitem__ with invalid index argument
class Identity:
def __getitem__(self, index: int) -> int:
return index
a = Identity()
# error: [invalid-argument-type] "Method `__getitem__` of type `bound method Identity.__getitem__(index: int) -> int` cannot be called with key of type `Literal["a"]` on object of type `Identity`"
a["a"]
__setitem__ with no __getitem__
class NoGetitem:
def __setitem__(self, index: int, value: int) -> None:
pass
a = NoGetitem()
a[0] = 0
Subscript store with no __setitem__
class NoSetitem: ...
a = NoSetitem()
a[0] = 0 # error: "Cannot assign to object of type `NoSetitem` with no `__setitem__` method"
__setitem__ not callable
class NoSetitem:
__setitem__ = None
a = NoSetitem()
a[0] = 0 # error: "Method `__setitem__` of type `Unknown | None` is possibly not callable on object of type `NoSetitem`"
Valid __setitem__ method
class Identity:
def __setitem__(self, index: int, value: int) -> None:
pass
a = Identity()
a[0] = 0
__setitem__ with invalid index argument
class Identity:
def __setitem__(self, index: int, value: int) -> None:
pass
a = Identity()
# error: [invalid-assignment] "Method `__setitem__` of type `bound method Identity.__setitem__(index: int, value: int) -> None` cannot be called with a key of type `Literal["a"]` and a value of type `Literal[0]` on object of type `Identity`"
a["a"] = 0