## Summary
For PEP 695 generic functions and classes, there is an extra "type
params scope" (a child of the outer scope, and wrapping the body scope)
in which the type parameters are defined; class bases and function
parameter/return annotations are resolved in that type-params scope.
This PR fixes some longstanding bugs in how we resolve name loads from
inside these PEP 695 type parameter scopes, and also defers type
inference of PEP 695 typevar bounds/constraints/default, so we can
handle cycles without panicking.
We were previously treating these type-param scopes as lazy nested
scopes, which is wrong. In fact they are eager nested scopes; the class
`C` here inherits `int`, not `str`, and previously we got that wrong:
```py
Base = int
class C[T](Base): ...
Base = str
```
But certain syntactic positions within type param scopes (typevar
bounds/constraints/defaults) are lazy at runtime, and we should use
deferred name resolution for them. This also means they can have cycles;
in order to handle that without panicking in type inference, we need to
actually defer their type inference until after we have constructed the
`TypeVarInstance`.
PEP 695 does specify that typevar bounds and constraints cannot be
generic, and that typevar defaults can only reference prior typevars,
not later ones. This reduces the scope of (valid from the type-system
perspective) cycles somewhat, although cycles are still possible (e.g.
`class C[T: list[C]]`). And this is a type-system-only restriction; from
the runtime perspective an "invalid" case like `class C[T: T]` actually
works fine.
I debated whether to implement the PEP 695 restrictions as a way to
avoid some cycles up-front, but I ended up deciding against that; I'd
rather model the runtime name-resolution semantics accurately, and
implement the PEP 695 restrictions as a separate diagnostic on top.
(This PR doesn't yet implement those diagnostics, thus some `# TODO:
error` in the added tests.)
Introducing the possibility of cyclic typevars made typevar display
potentially stack overflow. For now I've handled this by simply removing
typevar details (bounds/constraints/default) from typevar display. This
impacts display of two kinds of types. If you `reveal_type(T)` on an
unbound `T` you now get just `typing.TypeVar` instead of
`typing.TypeVar("T", ...)` where `...` is the bound/constraints/default.
This matches pyright and mypy; pyrefly uses `type[TypeVar[T]]` which
seems a bit confusing, but does include the name. (We could easily
include the name without cycle issues, if there's a syntax we like for
that.)
It also means that displaying a generic function type like `def f[T:
int](x: T) -> T: ...` now displays as `f[T](x: T) -> T` instead of `f[T:
int](x: T) -> T`. This matches pyright and pyrefly; mypy does include
bound/constraints/defaults of typevars in function/callable type
display. If we wanted to add this, we would either need to thread a
visitor through all the type display code, or add a `decycle` type
transformation that replaced recursive reoccurrence of a type with a
marker.
## Test Plan
Added mdtests and modified existing tests to improve their correctness.
After this PR, there's only a single remaining py-fuzzer seed in the
0-500 range that panics! (Before this PR, there were 10; the fuzzer
likes to generate cyclic PEP 695 syntax.)
## Ecosystem report
It's all just the changes to `TypeVar` display.
## Summary
A [passing
comment](https://github.com/astral-sh/ruff/pull/19711#issuecomment-3169312014)
led me to explore why we didn't report a class attribute as possibly
unbound if it was a method and defined in two different conditional
branches.
I found that the reason was because of our handling of "conflicting
declarations" in `place_from_declarations`. It returned a `Result` which
would be `Err` in case of conflicting declarations.
But we only actually care about conflicting declarations when we are
actually doing type inference on that scope and might emit a diagnostic
about it. And in all cases (including that one), we want to otherwise
proceed with the union of the declared types, as if there was no
conflict.
In several cases we were failing to handle the union of declared types
in the same way as a normal declared type if there was a declared-types
conflict. The `Result` return type made this mistake really easy to
make, as we'd match on e.g. `Ok(Place::Type(...))` and do one thing,
then match on `Err(...)` and do another, even though really both of
those cases should be handled the same.
This PR refactors `place_from_declarations` to instead return a struct
which always represents the declared type we should use in the same way,
as well as carrying the conflicting declared types, if any. This struct
has a method to allow us to explicitly ignore the declared-types
conflict (which is what we want in most cases), as well as a method to
get the declared type and the conflict information, in the case where we
want to emit a diagnostic on the conflict.
## Test Plan
Existing CI; added a test showing that we now understand a
multiply-conditionally-defined method as possibly-unbound.
This does trigger issues on a couple new fuzzer seeds, but the issues
are just new instances of an already-known (and rarely occurring)
problem which I already plan to address in a future PR, so I think it's
OK to land as-is.
I happened to build this initially on top of
https://github.com/astral-sh/ruff/pull/19711, which adds invalid-await
diagnostics, so I also updated some invalid-syntax tests to not await on
an invalid type, since the purpose of those tests is to check the
syntactic location of the `await`, not the validity of the awaited type.
## Summary
This is a follow-up to #19321.
If we try to access a class variable before it is defined, the variable
is looked up in the global scope, rather than in any enclosing scopes.
Closes https://github.com/astral-sh/ty/issues/875.
## Test Plan
New tests in `narrow/conditionals/nested.md`.
This PR introduces a few related changes:
- We now keep track of each time a legacy typevar is bound in a
different generic context (e.g. class, function), and internally create
a new `TypeVarInstance` for each usage. This means the rest of the code
can now assume that salsa-equivalent `TypeVarInstance`s refer to the
same typevar, even taking into account that legacy typevars can be used
more than once.
- We also go ahead and track the binding context of PEP 695 typevars.
That's _much_ easier to track since we have the binding context right
there during type inference.
- With that in place, we can now include the name of the binding context
when rendering typevars (e.g. `T@f` instead of `T`)
Co-authored-by: David Peter <sharkdp@users.noreply.github.com>
Co-authored-by: Carl Meyer <carl@oddbird.net>
Co-authored-by: Micha Reiser <micha@reiser.io>
Fixes https://github.com/astral-sh/ty/issues/769.
**Updated:** The preferred approach here is to keep the SemanticIndex
simple (`del` of any name marks that name "bound" in the current scope)
and to move complexity to type inference (free variable resolution stops
when it finds a binding, unless that binding is declared `nonlocal`). As
part of this change, free variable resolution will now union the types
it finds as it walks in enclosing scopes. This approach is still
incomplete, because it doesn't consider inner scopes or sibling scopes,
but it improves the common case.
---------
Co-authored-by: Carl Meyer <carl@astral.sh>
Previously this worked if there was also a binding in the same scope as
the `global` declaration (probably almost always the case), but CPython
doesn't require this.
This change surfaced an error in an existing test, where a global
variable was only ever declared and bound using the `global` keyword,
and never mentioned explicitly in the global scope. @AlexWaygood
suggested we probably want to keep that requirement, so I'm adding an a
new test for that on top of fixing the failing test.
The initial implementation of `infer_nonlocal` landed in
https://github.com/astral-sh/ruff/pull/19112 fails to report an error
for this example:
```py
x = 1
def f():
# This is only a usage of `x`, not a definition. It shouldn't be
# enough to make the `nonlocal` statement below allowed.
print(x)
def g():
nonlocal x
```
Fix this by continuing to walk enclosing scopes when the place we've
found isn't bound, declared, or `nonlocal`.
## Summary
This PR includes a behavioral change to how we infer types for public
uses of symbols within a module. Where we would previously use the type
that a use at the end of the scope would see, we now consider all
reachable bindings and union the results:
```py
x = None
def f():
reveal_type(x) # previously `Unknown | Literal[1]`, now `Unknown | None | Literal[1]`
f()
x = 1
f()
```
This helps especially in cases where the the end of the scope is not
reachable:
```py
def outer(x: int):
def inner():
reveal_type(x) # previously `Unknown`, now `int`
raise ValueError
```
This PR also proposes to skip the boundness analysis of public uses.
This is consistent with the "all reachable bindings" strategy, because
the implicit `x = <unbound>` binding is also always reachable, and we
would have to emit "possibly-unresolved" diagnostics for every public
use otherwise. Changing this behavior allows common use-cases like the
following to type check without any errors:
```py
def outer(flag: bool):
if flag:
x = 1
def inner():
print(x) # previously: possibly-unresolved-reference, now: no error
```
closes https://github.com/astral-sh/ty/issues/210
closes https://github.com/astral-sh/ty/issues/607
closes https://github.com/astral-sh/ty/issues/699
## Follow up
It is now possible to resolve the following TODO, but I would like to do
that as a follow-up, because it requires some changes to how we treat
implicit attribute assignments, which could result in ecosystem changes
that I'd like to see separately.
315fb0f3da/crates/ty_python_semantic/src/semantic_index/builder.rs (L1095-L1117)
## Ecosystem analysis
[**Full report**](https://shark.fish/diff-public-types.html)
* This change obviously removes a lot of `possibly-unresolved-reference`
diagnostics (7818) because we do not analyze boundness for public uses
of symbols inside modules anymore.
* As the primary goal here, this change also removes a lot of
false-positive `unresolved-reference` diagnostics (231) in scenarios
like this:
```py
def _(flag: bool):
if flag:
x = 1
def inner():
x
raise
```
* This change also introduces some new false positives for cases like:
```py
def _():
x = None
x = "test"
def inner():
x.upper() # Attribute `upper` on type `Unknown | None | Literal["test"]`
is possibly unbound
```
We have test cases for these situations and it's plausible that we can
improve this in a follow-up.
## Test Plan
New Markdown tests
## Summary
As far as I can tell, the two existing tests did the exact same thing.
Remove the redundant test, and add tests for all combinations of
declared/not-declared and local/"public" use of the name.
Proposing this as a separate PR before the behavior might change via
https://github.com/astral-sh/ruff/pull/18750
## Summary
Closes https://github.com/astral-sh/ty/issues/577. Make global
`__debug__` a `bool` constant.
## Test Plan
Mdtest `global-constants.md` was created to check if resolved type was
`bool`.
---------
Co-authored-by: David Peter <mail@david-peter.de>
## Summary
The PR adds an explicit check for `"__builtins__"` during name lookup,
similar to how `"__file__"` is implemented. The inferred type is
`Any`.
closes https://github.com/astral-sh/ty/issues/393
## Test Plan
Added a markdown test for `__builtins__`.
---------
Co-authored-by: David Peter <sharkdp@users.noreply.github.com>
## Summary
Understand that `__file__` is always set and a `str` when looked up as
an implicit global from a Python file we are type checking.
## Test Plan
mdtests
Summary
--
This PR resolves both the typing-related and syntax error TODOs added in
#17563 by tracking a set of `global` bindings for each scope. As
discussed below, we avoid the additional AST traversal from ruff by
collecting `Name`s from `global` statements while building the semantic
index and emit a syntax error if the `Name` is already bound in the
current scope at the point of the `global` statement. This has the
downside of separating the error from the `SemanticSyntaxChecker`, but I
plan to explore using this approach in the `SemanticSyntaxChecker`
itself as a follow-up. It seems like this may be a better approach for
ruff as well.
Test Plan
--
Updated all of the related mdtests to remove the TODOs (and add quotes I
forgot on the messages).
There is one remaining TODO, but it requires `nonlocal` support, which
isn't even incorporated into the `SemanticSyntaxChecker` yet.
---------
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
Co-authored-by: Carl Meyer <carl@astral.sh>
