Try tweaking attrs.fields()

[Tinche]

Trying to fix #15393 in an alternative way.

@JukkaL I might need some help here. I'm still getting builtins.object while iterating:

from attrs import define, fields


@define
class Test:
    a: int
    b: float


for f in fields(Test):
    reveal_type(f)  # note: Revealed type is "builtins.object"

But if I do this:

for f in iter(fields(Test)):
    reveal_type(f)  # note: Revealed type is "attr.Attribute[Any]"

Any ideas?

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[ikonst]

I might not be helping here, but what you did with copying the __iter__ symbol is a likely the outlier.

The normal behavior e.g. for a tuple, is:

t: tuple[list[int], list[float]]
for v in t:
    reveal_type(v)  # note: Revealed type is "builtins.object"
for v in iter(t):
    reveal_type(v)  # note: Revealed type is "builtins.object"
reveal_type(x.__iter__())  # note: Revealed type is "typing.Iterator[builtins.object]"

Update: This is the culprit. Tuples are special-cased.

[jhance]

Can we add a new field to TupleType that is only for that callsite? Like joined_type_for_iter or something?

[Tinche]

Superseded by #15688