## Summary
There are quite a few places we infer `Todo` types currently, and some
of them are nested somewhat deeply in type expressions. These can cause
spurious issues for the new `redundant-cast` diagnostics. We fixed all
the false positives we saw in the mypy_primer report before merging
https://github.com/astral-sh/ruff/pull/17100, but I think there are
still lots of places where we'd emit false positives due to this check
-- we currently don't run on that many projects at all in our
mypy_primer check:
d0c8eaa092/.github/workflows/mypy_primer.yaml (L71)
This PR fixes some more false positives from this diagnostic by making
the `Type::contains_todo()` method more expansive.
## Test Plan
I added a regression test which causes us to emit a spurious diagnostic
on `main`, but does not with this PR.
## Summary
Following up from earlier discussion on Discord, this PR adds logic to
flag casts as redundant when the inferred type of the expression is the
same as the target type. It should follow the semantics from
[mypy](https://github.com/python/mypy/pull/1705).
Example:
```python
def f() -> int:
return 10
# error: [redundant-cast] "Value is already of type `int`"
cast(int, f())
```
This breaks up call binding into two phases:
- **_Matching parameters_** just looks at the names and kinds
(positional/keyword) of each formal and actual parameters, and matches
them up. Most of the current call binding errors happen during this
phase.
- Once we have matched up formal and actual parameters, we can **_infer
types_** of each actual parameter, and **_check_** that each one is
assignable to the corresponding formal parameter type.
As part of this, we add information to each formal parameter about
whether it is a type form or not. Once [PEP
747](https://peps.python.org/pep-0747/) is finalized, we can hook that
up to this internal type form representation. This replaces the
`ParameterExpectations` type, which did the same thing in a more ad hoc
way.
While we're here, we add a new fluent API for building `Parameter`s,
which makes our signature constructors a bit nicer to read. We also
eliminate a TODO where we were consuming types from the argument list
instead of the bound parameter list when evaluating our special-case
known functions.
Closes#15460
---------
Co-authored-by: Micha Reiser <micha@reiser.io>
## Summary
Related to #15848, this PR adds the imports explicitly as we'll now flag
these symbols as undefined.
---------
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
