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Apr 4, 2025
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[syntax-errors] Allow yield in base classes and annotations #17206

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73d2c0a
[syntax-errors] Allow `yield` in base classes and annotations
ntBre Apr 4, 2025
c1ab658
restore function type annotation error for future annotations, 3.14
ntBre Apr 4, 2025
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4 changes: 4 additions & 0 deletions crates/ruff_linter/src/checkers/ast/mod.rs
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Expand Up @@ -587,6 +587,10 @@ impl SemanticSyntaxContext for Checker<'_> {
fn source(&self) -> &str {
self.source()
}

fn future_annotations_or_stub(&self) -> bool {
self.semantic.future_annotations_or_stub()
}
}

impl<'a> Visitor<'a> for Checker<'a> {
Expand Down
2 changes: 0 additions & 2 deletions crates/ruff_python_parser/resources/inline/err/invalid_annotation_class.py
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@@ -1,6 +1,4 @@
class F[T](y := list): ...
class G((yield 1)): ...
class H((yield from 1)): ...
class I[T]((yield 1)): ...
class J[T]((yield from 1)): ...
class K[T: (yield 1)]: ... # yield in TypeVar
Expand Down
4 changes: 0 additions & 4 deletions crates/ruff_python_parser/resources/inline/err/invalid_annotation_function.py
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@@ -1,13 +1,9 @@
def f[T]() -> (y := 3): ...
def g[T](arg: (x := 1)): ...
def h[T](x: (yield 1)): ...
def i(x: (yield 1)): ...
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@JelleZijlstra JelleZijlstra Apr 4, 2025

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These ones should perhaps stay as errors. They are a syntax error in Python 3.14 (and under from __future__ import annotations). They're legal otherwise in older versions, but yielding in an annotation is a very questionable idea and it will be a SyntaxError in the future, so it would make sense for Ruff to error about it.

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@ntBre ntBre Apr 4, 2025

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Oh, interesting. We can check the version before emitting these errors, but I don't think we have any others that depend on from __future__ import annotations yet. It does seem easiest just to make this an error on any version in that case. Thanks!

And it looks like my error message was very similar to CPython in that case too:

>>> from __future__ import annotations
>>> def i(x: (yield 1)): ...
  File "<python-input-1>", line 1
    def i(x: (yield 1)): ...
              ^^^^^^^
SyntaxError: yield expression cannot be used within an annotation

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@JelleZijlstra JelleZijlstra Apr 4, 2025

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For reference: https://peps.python.org/pep-0649/#changes-to-allowable-annotations-syntax

Up to you how to handle this in Ruff. You could raise a SyntaxError on all versions for simplicity (pro: helps prepare people for the error, simpler to implement; con: not strictly accurate on 3.13 and earlier, might have false positives in the unlikely case people are actually using yield etc. in annotations). You could also add a new error code specifically for this case, so people can ignore it if they want. Or you can just leave it as in this PR for now, and make it a SyntaxError for >3.14 only once you add 3.14 support.

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@ntBre ntBre Apr 4, 2025

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Oh is this the same for named expressions too? I had already skipped those in the initial PR because they were allowed in 3.13:

>>> def i(x: (x:=1)): ...
...
>>> from __future__ import annotations
>>> def i(x: (x:=1)): ...
  File "<python-input-2>", line 1
    def i(x: (x:=1)): ...
              ^^^^
SyntaxError: named expression cannot be used within an annotation
>>>

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@JelleZijlstra JelleZijlstra Apr 4, 2025

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Yes, and await. (The comment above was written before I saw your reply.)

def j[T]() -> (yield 1): ...
def k() -> (yield 1): ...
def l[T](x: (yield from 1)): ...
def m(x: (yield from 1)): ...
def n[T]() -> (yield from 1): ...
def o() -> (yield from 1): ...
def p[T: (yield 1)](): ... # yield in TypeVar bound
def q[T = (yield 1)](): ... # yield in TypeVar default
def r[*Ts = (yield 1)](): ... # yield in TypeVarTuple default
Expand Down
8 changes: 8 additions & 0 deletions crates/ruff_python_parser/resources/inline/err/invalid_annotation_function_py314.py
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@@ -0,0 +1,8 @@
# parse_options: {"target-version": "3.14"}
def f() -> (y := 3): ...
def g(arg: (x := 1)): ...
def outer():
def i(x: (yield 1)): ...
def k() -> (yield 1): ...
def m(x: (yield from 1)): ...
def o() -> (yield from 1): ...
3 changes: 3 additions & 0 deletions crates/ruff_python_parser/resources/inline/ok/valid_annotation_class.py
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@@ -1 +1,4 @@
class F(y := list): ...
def f():
class G((yield 1)): ...
class H((yield from 1)): ...
5 changes: 5 additions & 0 deletions crates/ruff_python_parser/resources/inline/ok/valid_annotation_function.py
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@@ -1,2 +1,7 @@
def f() -> (y := 3): ...
def g(arg: (x := 1)): ...
def outer():
def i(x: (yield 1)): ...
def k() -> (yield 1): ...
def m(x: (yield from 1)): ...
def o() -> (yield from 1): ...
71 changes: 30 additions & 41 deletions crates/ruff_python_parser/src/semantic_errors.rs
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Expand Up @@ -128,18 +128,29 @@ impl SemanticSyntaxChecker {
// test_ok valid_annotation_function
// def f() -> (y := 3): ...
// def g(arg: (x := 1)): ...
// def outer():
// def i(x: (yield 1)): ...
// def k() -> (yield 1): ...
// def m(x: (yield from 1)): ...
// def o() -> (yield from 1): ...

// test_err invalid_annotation_function_py314
// # parse_options: {"target-version": "3.14"}
// def f() -> (y := 3): ...
// def g(arg: (x := 1)): ...
// def outer():
// def i(x: (yield 1)): ...
// def k() -> (yield 1): ...
// def m(x: (yield from 1)): ...
// def o() -> (yield from 1): ...

// test_err invalid_annotation_function
// def f[T]() -> (y := 3): ...
// def g[T](arg: (x := 1)): ...
// def h[T](x: (yield 1)): ...
// def i(x: (yield 1)): ...
// def j[T]() -> (yield 1): ...
// def k() -> (yield 1): ...
// def l[T](x: (yield from 1)): ...
// def m(x: (yield from 1)): ...
// def n[T]() -> (yield from 1): ...
// def o() -> (yield from 1): ...
// def p[T: (yield 1)](): ... # yield in TypeVar bound
// def q[T = (yield 1)](): ... # yield in TypeVar default
// def r[*Ts = (yield 1)](): ... # yield in TypeVarTuple default
Expand All @@ -148,19 +159,20 @@ impl SemanticSyntaxChecker {
// def u[T = (x := 1)](): ... # named expr in TypeVar default
// def v[*Ts = (x := 1)](): ... # named expr in TypeVarTuple default
// def w[**Ts = (x := 1)](): ... # named expr in ParamSpec default
let is_generic = type_params.is_some();
let mut visitor = InvalidExpressionVisitor {
allow_named_expr: !is_generic,
position: InvalidExpressionPosition::TypeAnnotation,
ctx,
};
if let Some(type_params) = type_params {
visitor.visit_type_params(type_params);
}
if is_generic {
// the __future__ annotation error takes precedence over the generic error
if ctx.future_annotations_or_stub() || ctx.python_version() > PythonVersion::PY313 {
visitor.position = InvalidExpressionPosition::TypeAnnotation;
} else if type_params.is_some() {
visitor.position = InvalidExpressionPosition::GenericDefinition;
} else {
visitor.position = InvalidExpressionPosition::TypeAnnotation;
return;
}
for param in parameters
.iter()
Expand All @@ -173,36 +185,29 @@ impl SemanticSyntaxChecker {
}
}
Stmt::ClassDef(ast::StmtClassDef {
type_params,
type_params: Some(type_params),
arguments,
..
}) => {
// test_ok valid_annotation_class
// class F(y := list): ...
// def f():
// class G((yield 1)): ...
// class H((yield from 1)): ...

// test_err invalid_annotation_class
// class F[T](y := list): ...
// class G((yield 1)): ...
// class H((yield from 1)): ...
// class I[T]((yield 1)): ...
// class J[T]((yield from 1)): ...
// class K[T: (yield 1)]: ... # yield in TypeVar
// class L[T: (x := 1)]: ... # named expr in TypeVar
let is_generic = type_params.is_some();
let mut visitor = InvalidExpressionVisitor {
allow_named_expr: !is_generic,
position: InvalidExpressionPosition::TypeAnnotation,
ctx,
};
if let Some(type_params) = type_params {
visitor.visit_type_params(type_params);
}
if is_generic {
visitor.position = InvalidExpressionPosition::GenericDefinition;
} else {
visitor.position = InvalidExpressionPosition::BaseClass;
}
visitor.visit_type_params(type_params);
if let Some(arguments) = arguments {
visitor.position = InvalidExpressionPosition::GenericDefinition;
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@MichaReiser MichaReiser Apr 4, 2025

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Do we need the same future check here to determine the position or are functions different?

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@ntBre ntBre Apr 4, 2025

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I think base classes still allow this, at least with future annotations:

>>> from __future__ import annotations
>>> class F(y := list): ...
... def f[T]():
...     class G((yield 1)): ...
...     class H((yield from 1)): ...
...

Although I'm now realizing that this applies to other annotations not considered in this PR:

>>> def f():
...     x: (yield 1)
...
>>> from __future__ import annotations
>>> def f():
...     x: (yield 1)
...
  File "<python-input-2>", line 2
    x: (yield 1)
        ^^^^^^^
SyntaxError: yield expression cannot be used within an annotation

Another addition to #11934...

visitor.visit_arguments(arguments);
}
}
Expand All @@ -217,7 +222,6 @@ impl SemanticSyntaxChecker {
// type Y = (yield 1) # yield in value
// type Y = (x := 1) # named expr in value
let mut visitor = InvalidExpressionVisitor {
allow_named_expr: false,
position: InvalidExpressionPosition::TypeAlias,
ctx,
};
Expand Down Expand Up @@ -625,12 +629,6 @@ impl Display for SemanticSyntaxError {
write!(f, "cannot delete `__debug__` on Python {python_version} (syntax was removed in 3.9)")
}
},
SemanticSyntaxErrorKind::InvalidExpression(
kind,
InvalidExpressionPosition::BaseClass,
) => {
write!(f, "{kind} cannot be used as a base class")
}
SemanticSyntaxErrorKind::InvalidExpression(kind, position) => {
write!(f, "{kind} cannot be used within a {position}")
}
Expand Down Expand Up @@ -858,7 +856,6 @@ pub enum InvalidExpressionPosition {
TypeVarTupleDefault,
ParamSpecDefault,
TypeAnnotation,
BaseClass,
GenericDefinition,
TypeAlias,
}
Expand All @@ -872,7 +869,6 @@ impl Display for InvalidExpressionPosition {
InvalidExpressionPosition::ParamSpecDefault => "ParamSpec default",
InvalidExpressionPosition::TypeAnnotation => "type annotation",
InvalidExpressionPosition::GenericDefinition => "generic definition",
InvalidExpressionPosition::BaseClass => "base class",
InvalidExpressionPosition::TypeAlias => "type alias",
})
}
Expand Down Expand Up @@ -1086,16 +1082,6 @@ impl<'a, Ctx: SemanticSyntaxContext> MatchPatternVisitor<'a, Ctx> {
}

struct InvalidExpressionVisitor<'a, Ctx> {
/// Allow named expressions (`x := ...`) to appear in annotations.
///
/// These are allowed in non-generic functions, for example:
///
/// ```python
/// def foo(arg: (x := int)): ... # ok
/// def foo[T](arg: (x := int)): ... # syntax error
/// ```
allow_named_expr: bool,

/// Context used for emitting errors.
ctx: &'a Ctx,

Expand All @@ -1108,7 +1094,7 @@ where
{
fn visit_expr(&mut self, expr: &Expr) {
match expr {
Expr::Named(ast::ExprNamed { range, .. }) if !self.allow_named_expr => {
Expr::Named(ast::ExprNamed { range, .. }) => {
SemanticSyntaxChecker::add_error(
self.ctx,
SemanticSyntaxErrorKind::InvalidExpression(
Expand Down Expand Up @@ -1166,6 +1152,9 @@ pub trait SemanticSyntaxContext {
/// Returns `true` if a module's docstring boundary has been passed.
fn seen_docstring_boundary(&self) -> bool;

/// Returns `true` if `__future__`-style type annotations are enabled.
fn future_annotations_or_stub(&self) -> bool;

/// The target Python version for detecting backwards-incompatible syntax changes.
fn python_version(&self) -> PythonVersion;

Expand Down
4 changes: 4 additions & 0 deletions crates/ruff_python_parser/tests/fixtures.rs
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Expand Up @@ -490,6 +490,10 @@ impl SemanticSyntaxContext for TestContext<'_> {
false
}

fn future_annotations_or_stub(&self) -> bool {
false
}

fn python_version(&self) -> PythonVersion {
self.python_version
}
Expand Down
10 changes: 0 additions & 10 deletions ...uff_python_parser/tests/snapshots/invalid_syntax@function_def_invalid_return_expr.py.snap
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Expand Up @@ -179,13 +179,3 @@ Module(
3 | def foo() -> yield x: ...
| ^^^^^^^ Syntax Error: Yield expression cannot be used here
|


## Semantic Syntax Errors

|
1 | def foo() -> *int: ...
2 | def foo() -> (*int): ...
3 | def foo() -> yield x: ...
| ^^^^^^^ Syntax Error: yield expression cannot be used within a type annotation
|
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