## Summary
This is the second PR out of three that adds support for
enabling/disabling lint rules in Red Knot. You may want to take a look
at the [first PR](https://github.com/astral-sh/ruff/pull/14869) in this
stack to familiarize yourself with the used terminology.
This PR adds a new syntax to define a lint:
```rust
declare_lint! {
/// ## What it does
/// Checks for references to names that are not defined.
///
/// ## Why is this bad?
/// Using an undefined variable will raise a `NameError` at runtime.
///
/// ## Example
///
/// ```python
/// print(x) # NameError: name 'x' is not defined
/// ```
pub(crate) static UNRESOLVED_REFERENCE = {
summary: "detects references to names that are not defined",
status: LintStatus::preview("1.0.0"),
default_level: Level::Warn,
}
}
```
A lint has a name and metadata about its status (preview, stable,
removed, deprecated), the default diagnostic level (unless the
configuration changes), and documentation. I use a macro here to derive
the kebab-case name and extract the documentation automatically.
This PR doesn't yet add any mechanism to discover all known lints. This
will be added in the next and last PR in this stack.
## Documentation
I documented some rules but then decided that it's probably not my best
use of time if I document all of them now (it also means that I play
catch-up with all of you forever). That's why I left some rules
undocumented (marked with TODO)
## Where is the best place to define all lints?
I'm not sure. I think what I have in this PR is fine but I also don't
love it because most lints are in a single place but not all of them. If
you have ideas, let me know.
## Why is the message not part of the lint, unlike Ruff's `Violation`
I understand that the main motivation for defining `message` on
`Violation` in Ruff is to remove the need to repeat the same message
over and over again. I'm not sure if this is an actual problem. Most
rules only emit a diagnostic in a single place and they commonly use
different messages if they emit diagnostics in different code paths,
requiring extra fields on the `Violation` struct.
That's why I'm not convinced that there's an actual need for it and
there are alternatives that can reduce the repetition when creating a
diagnostic:
* Create a helper function. We already do this in red knot with the
`add_xy` methods
* Create a custom `Diagnostic` implementation that tailors the entire
diagnostic and pre-codes e.g. the message
Avoiding an extra field on the `Violation` also removes the need to
allocate intermediate strings as it is commonly the place in Ruff.
Instead, Red Knot can use a borrowed string with `format_args`
## Test Plan
`cargo test`
## Summary
Adds meta information to `Type::Todo`, allowing developers to easily
trace back the origin of a particular `@Todo` type they encounter.
Instead of `Type::Todo`, we now write either `type_todo!()` which
creates a `@Todo[path/to/source.rs:123]` type with file and line
information, or using `type_todo!("PEP 604 unions not supported")`,
which creates a variant with a custom message.
`Type::Todo` now contains a `TodoType` field. In release mode, this is
just a zero-sized struct, in order not to create any overhead. In debug
mode, this is an `enum` that contains the meta information.
`Type` implements `Copy`, which means that `TodoType` also needs to be
copyable. This limits the design space. We could intern `TodoType`, but
I discarded this option, as it would require us to have access to the
salsa DB everywhere we want to use `Type::Todo`. And it would have made
the macro invocations less ergonomic (requiring us to pass `db`).
So for now, the meta information is simply a `&'static str` / `u32` for
the file/line variant, or a `&'static str` for the custom message.
Anything involving a chain/backtrace of several `@Todo`s or similar is
therefore currently not implemented. Also because we currently don't see
any direct use cases for this, and because all of this will eventually
go away.
Note that the size of `Type` increases from 16 to 24 bytes, but only in
debug mode.
## Test Plan
- Observed the changes in Markdown tests.
- Added custom messages for all `Type::Todo`s that were revealed in the
tests
- Ran red knot in release and debug mode on the following Python file:
```py
def f(x: int) -> int:
reveal_type(x)
```
Prints `@Todo` in release mode and `@Todo(function parameter type)` in
debug mode.
## Summary
Add a typed representation of function signatures (parameters and return
type) and infer it correctly from a function.
Convert existing usage of function return types to use the signature
representation.
This does not yet add inferred types for parameters within function body
scopes based on the annotations, but it should be easy to add as a next
step.
Part of #14161 and #13693.
## Test Plan
Added tests.
## Summary
Create definitions and infer types for PEP 695 type variables.
This just gives us the type of the type variable itself (the type of `T`
as a runtime object in the body of `def f[T](): ...`), with special
handling for its attributes `__name__`, `__bound__`, `__constraints__`,
and `__default__`. Mostly the support for these attributes exists
because it is easy to implement and allows testing that we are
internally representing the typevar correctly.
This PR doesn't yet have support for interpreting a typevar as a type
annotation, which is of course the primary use of a typevar. But the
information we store in the typevar's type in this PR gives us
everything we need to handle it correctly in a future PR when the
typevar appears in an annotation.
## Test Plan
Added mdtest.
## Summary
This PR adds support for heterogenous `tuple` annotations to red-knot.
It does the following:
- Extends `infer_type_expression` so that it understands tuple
annotations
- Changes `infer_type_expression` so that `ExprStarred` nodes in type
annotations are inferred as `Todo` rather than `Unknown` (they're valid
in PEP-646 tuple annotations)
- Extends `Type::is_subtype_of` to understand when one heterogenous
tuple type can be understood to be a subtype of another (without this
change, the PR would have introduced new false-positive errors to some
existing mdtests).
Summary
---------
PEP 695 Generics introduce a scope inside a class statement's arguments
and keywords.
```
class C[T](A[T]): # the T in A[T] is not from the global scope but from a type-param-specfic scope
...
```
When doing inference on the class bases, we currently have been doing
base class expression lookups in the global scope. Not an issue without
generics (since a scope is only created when generics are present).
This change instead makes sure to stop the global scope inference from
going into expressions within this sub-scope. Since there is a separate
scope, `check_file` and friends will trigger inference on these
expressions still.
Another change as a part of this is making sure that `ClassType` looks
up its bases in the right scope.
Test Plan
----------
`cargo test --package red_knot_python_semantic generics` will run the
markdown test that previously would panic due to scope lookup issues
---------
Co-authored-by: Micha Reiser <micha@reiser.io>
Co-authored-by: Carl Meyer <carl@astral.sh>
