Distinct formatting for type objects #3374
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test-data/unit/check-generics.test
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| @@ -1505,7 +1505,7 @@ T = TypeVar('T') | |||
| class C(Generic[T]): | |||
| def __init__(self) -> None: pass | |||
| x = C # type: Callable[[], C[int]] | |||
| y = C # type: Callable[[], int] # E: Incompatible types in assignment (expression has type C[T], variable has type Callable[[], int]) | |||
| y = C # type: Callable[[], int] # E: Incompatible types in assignment (expression has type Type[C[T]], variable has type Callable[[], int]) | |||
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Probably unrelated to this PR, but this error message looks not right, it should be Type[C] here (or maybe Type[C[Any]]). If not and it is not easy to fix this (by just erasing the return type) in the same PR, could you please open a new issue?
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I am also not entirely sure I understand what's wrong with Type[C[T]]. Making this work seems to require either bringing erasure to this module or duplicating the formatting of instance types without type parameters.
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I am also not entirely sure I understand what's wrong with
Type[C[T]]
PEP 484 specifies that bare (unsubscribed) type is equivalent to C[Any]. Moreover, writing C[T] is invalid in this context (and in other examples I mentioned below) and will trigger a mypy error Invalid type '__main__.T'.
Does fixing this actually requires extensive code duplication? If yes, then maybe it is better to import erasetype.
test-data/unit/pythoneval.test
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| @@ -1096,7 +1096,7 @@ class MyDDict(t.DefaultDict[int,T], t.Generic[T]): | |||
| MyDDict(dict)['0'] | |||
| MyDDict(dict)[0] | |||
| [out] | |||
| _program.py:6: error: Argument 1 to "defaultdict" has incompatible type List[_T]; expected Callable[[], str] | |||
| _program.py:6: error: Argument 1 to "defaultdict" has incompatible type Type[List[_T]]; expected Callable[[], str] | |||
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Again, this should be Type[List] or Type[List[Any]].
test-data/unit/check-functions.test
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| @@ -1479,7 +1479,7 @@ L = Callable[[Arg(name='x', type=int)], int] # ok | |||
| # I have commented out the following test because I don't know how to expect the "defined here" note part of the error. | |||
| # M = Callable[[Arg(gnome='x', type=int)], int] E: Invalid type alias E: Unexpected keyword argument "gnome" for "Arg" | |||
| N = Callable[[Arg(name=None, type=int)], int] # ok | |||
| O = Callable[[List[Arg(int)]], int] # E: Invalid type alias # E: Value of type "int" is not indexable # E: Type expected within [...] # E: The type List[T] is not generic and not indexable | |||
| O = Callable[[List[Arg(int)]], int] # E: Invalid type alias # E: Value of type "int" is not indexable # E: Type expected within [...] # E: The type Type[List[T]] is not generic and not indexable | |||
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E: The type
Type[List[T]]is not generic and not indexable.
@sixolet This error looks quite confusing in this context, since the type mentioned is generic and is indexable. In real mypy installation (not in tests) I get these errors:
tst26.py:14: error: Invalid type alias
tst26.py:14: error: Value of type "object" is not indexable
tst26.py:14: error: Type expected within [...]
tst26.py:14: error: Value of type List[_T] is not indexable
Note that none of them mentions (or even hints) that something is wrong with Arg. Is there an issue for improving the error message in such cases?
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Thank you! (Both.) |
Fix #3050. (The discussion there is not over yet, but this PR can demonstrate the formatting)