Avoid narrowing type[T]

[hauntsaninja]

Maybe a little ad hoc, but avoids some of the undesirable primer regression from #20492

Closes#20636

[hauntsaninja]

This is a win on spark and zulip
The xarray code is suspect; it ideally should be unreachable, but I don't mind the error
artigraph error is fine. We mark some code as reachable that is reachable (real fix is elsewhere though)

So I think all the primer is good

[hauntsaninja]

The behaviour here was fixed in the first PR #20492 , not in this one, but I didn't add the test coverage for it in the original PR.

Makes sense to add in this PR because bad versions of the current change could have regressed the fix.

(The behaviour in the f3 case could potentially be made more consistent, but this should be the subject of future investigation)

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

spark (https://github.com/apache/spark)
- python/pyspark/mllib/regression.py:282: error: Unused "type: ignore" comment [unused-ignore]- python/pyspark/mllib/regression.py:282: error: Incompatible return value type (got "LogisticRegressionModel", expected "LM") [return-value]- python/pyspark/mllib/regression.py:282: note: Error code "return-value" not covered by "type: ignore" comment
zulip (https://github.com/zulip/zulip)
- analytics/views/stats.py:577: error: Incompatible return value type (got "QuerySet[RealmCount, RealmCount]", expected "QuerySet[CountT, CountT]") [return-value]- analytics/views/stats.py:579: error: Incompatible return value type (got "QuerySet[UserCount, UserCount]", expected "QuerySet[CountT, CountT]") [return-value]- analytics/views/stats.py:581: error: Incompatible return value type (got "QuerySet[StreamCount, StreamCount]", expected "QuerySet[CountT, CountT]") [return-value]- analytics/views/stats.py:583: error: Incompatible return value type (got "QuerySet[InstallationCount, InstallationCount]", expected "QuerySet[CountT, CountT]") [return-value]- analytics/views/stats.py:585: error: Incompatible return value type (got "QuerySet[RemoteInstallationCount, RemoteInstallationCount]", expected "QuerySet[CountT, CountT]") [return-value]- analytics/views/stats.py:587: error: Incompatible return value type (got "QuerySet[RemoteRealmCount, RemoteRealmCount]", expected "QuerySet[CountT, CountT]") [return-value]
artigraph (https://github.com/artigraph/artigraph)
+ src/arti/views/__init__.py:98: error: Incompatible types in assignment (expression has type "type[View] | None", variable has type "type[Self]") [assignment]+ src/arti/views/__init__.py:102: error: Incompatible types in assignment (expression has type "type[View] | None", variable has type "type[Self]") [assignment]
xarray (https://github.com/pydata/xarray)
+ xarray/indexes/nd_point_index.py: note: In member "from_variables" of class "NDPointIndex":+ xarray/indexes/nd_point_index.py:271: error: Incompatible types in assignment (expression has type "type[ScipyKDTreeAdapter]", variable has type "type[T_TreeAdapter]") [assignment]