## Summary
This PR adds type narrowing in `and` and `or` expressions, for example:
```py
class A: ...
x: A | None = A() if bool_instance() else None
isinstance(x, A) or reveal_type(x) # revealed: None
```
## Test Plan
New mdtests 😍
## Summary
After #13918 has landed, narrowing constraint negation became easy, so
adding support for `not` operator.
## Test Plan
Added a new mdtest file for `not` expression.
---------
Co-authored-by: Carl Meyer <carl@astral.sh>
## Summary
Add support for type narrowing in elif and else scopes as part of
#13694.
## Test Plan
- mdtest
- builder unit test for union negation.
---------
Co-authored-by: Carl Meyer <carl@astral.sh>
## Summary
Add type narrowing for `isinstance(object, classinfo)` [1] checks:
```py
x = 1 if flag else "a"
if isinstance(x, int):
reveal_type(x) # revealed: Literal[1]
```
closes#13893
[1] https://docs.python.org/3/library/functions.html#isinstance
## Test Plan
New Markdown-based tests in `narrow/isinstance.md`.
---------
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
## Summary
- Properly treat the empty intersection as being of type `object`.
- Consequently, change the simplification method to explicitly add
`Never` to the positive side of the intersection when collapsing a type
such as `int & str` to `Never`, as opposed to just clearing both the
positive and the negative side.
- Minor code improvement in `bindings_ty`: use `peekable()` to check
whether the iterator over constraints is empty, instead of handling
first and subsequent elements separately.
fixes#13870
## Test Plan
- New unit tests for `IntersectionBuilder` to make sure the empty
intersection represents `object`.
- Markdown-based regression test for the original issue in #13870
Add type narrowing for `!=` expression as stated in
#13694.
### Test Plan
Add tests in new md format.
---------
Co-authored-by: David Peter <mail@david-peter.de>
## Summary
A small fix for comparisons of multiple comparators.
Instead of comparing each comparator to the leftmost item, we should
compare it to the closest item on the left.
While implementing this, I noticed that we don’t yet narrow Yoda
comparisons (e.g., `True is x`), so I didn’t change that behavior in
this PR.
## Test Plan
Added some mdtests 🎉
## Summary
- Add `Type::is_disjoint_from` as a way to test whether two types
overlap
- Add a first set of simplification rules for intersection types
- `S & T = S` for `S <: T`
- `S & ~T = Never` for `S <: T`
- `~S & ~T = ~T` for `S <: T`
- `A & ~B = A` for `A` disjoint from `B`
- `A & B = Never` for `A` disjoint from `B`
- `bool & ~Literal[bool] = Literal[!bool]`
resolves one item in #12694
## Open questions:
- Can we somehow leverage the (anti) symmetry between `positive` and
`negative` contributions? I could imagine that there would be a way if
we had `Type::Not(type)`/`Type::Negative(type)`, but with the
`positive`/`negative` architecture, I'm not sure. Note that there is a
certain duplication in the `add_positive`/`add_negative` functions (e.g.
`S & ~T = Never` is implemented twice), but other rules are actually not
perfectly symmetric: `S & T = S` vs `~S & ~T = ~T`.
- I'm not particularly proud of the way `add_positive`/`add_negative`
turned out. They are long imperative-style functions with some
mutability mixed in (`to_remove`). I'm happy to look into ways to
improve this code *if we decide to go with this approach* of
implementing a set of ad-hoc rules for simplification.
- ~~Is it useful to perform simplifications eagerly in
`add_positive`/`add_negative`? (@carljm)~~ This is what I did for now.
## Test Plan
- Unit tests for `Type::is_disjoint_from`
- Observe changes in Markdown-based tests
- Unit tests for `IntersectionBuilder::build()`
---------
Co-authored-by: Carl Meyer <carl@astral.sh>
Minor cleanup and consistent formatting of the Markdown-based tests.
- Removed lots of unnecessary `a`, `b`, `c`, … variables.
- Moved test assertions (`# revealed:` comments) closer to the tested
object.
- Always separate `# revealed` and `# error` comments from the code by
two spaces, according to the discussion
[here](https://github.com/astral-sh/ruff/pull/13746/files#r1799385758).
This trades readability for consistency in some cases.
- Fixed some headings
## Summary
Porting infer tests to new markdown tests framework.
Link to the corresponding issue: #13696
---------
Co-authored-by: Carl Meyer <carl@astral.sh>
## Summary
- Fix a bug with `… is not …` type guards.
Previously, in an example like
```py
x = [1]
y = [1]
if x is not y:
reveal_type(x)
```
we would infer a type of `list[int] & ~list[int] == Never` for `x`
inside the conditional (instead of `list[int]`), since we built a
(negative) intersection with the type of the right hand side (`y`).
However, as this example shows, this assumption can only be made for
singleton types (types with a single inhabitant) such as `None`.
- Add support for `… is …` type guards.
closes#13715
## Test Plan
Moved existing `narrow_…` tests to Markdown-based tests and added new
ones (including a regression test for the bug described above). Note
that will create some conflicts with
https://github.com/astral-sh/ruff/pull/13719. I tried to establish the
correct organizational structure as proposed in
https://github.com/astral-sh/ruff/pull/13719#discussion_r1800188105
