[syntax-errors] Single starred assignment target #17024
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Summary
--
Detects starred assignment targets outside of tuples and lists like `*a = (1,)`.
This PR only considers assignment statements. I also checked annotated assigment
statements, but these give a separate error, so I think they're okay not to
consider:
```pycon
>>> *a: list[int] = []
File "<python-input-72>", line 1
*a: list[int] = []
^
SyntaxError: invalid syntax
```
Fixes #13759
Test Plan
--
New inline tests, plus a new `SemanticSyntaxError` for an existing parser test.
I also removed a now-invalid case from an otherwise-valid test fixture.
The new semantic error leads to two errors for the case below:
```python
*foo() = 42
```
but this matches [pyright] too.
[pyright]: https://pyright-play.net/?code=FQMw9mAUCUAEC8sAsAmAUEA
ntBre
added
rule
dhruvmanila
approved these changes
Mar 27, 2025
Comment on lines
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| Stmt::Assign(ast::StmtAssign { targets, .. }) => { | ||
| // test_err single_starred_assignment_target | ||
| // *a = (1,) | ||
|
|
||
| // test_ok single_starred_assignment_target | ||
| // (*a,) = (1,) | ||
| // *a, = (1,) | ||
| // [*a] = (1,) | ||
| if let [Expr::Starred(ast::ExprStarred { range, .. })] = targets.as_slice() { | ||
| Self::add_error( |
There was a problem hiding this comment.
I think I'd find it useful to keep the test_err closer to the add_error calls, so I'd switch the test_err and test_ok comments around and move them right above the Self::add_error call:
if let ... {
// test_ok ...
// test_err ...
Self::add_error(...)
}
Comment on lines
553
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563
| | SemanticSyntaxErrorKind::IrrefutableCasePattern(_) | ||
| | SemanticSyntaxErrorKind::SingleStarredAssignment | ||
| if self.settings.preview.is_enabled() => | ||
| { | ||
| self.semantic_errors.borrow_mut().push(error); | ||
| } | ||
| SemanticSyntaxErrorKind::ReboundComprehensionVariable | ||
| | SemanticSyntaxErrorKind::DuplicateTypeParameter | ||
| | SemanticSyntaxErrorKind::MultipleCaseAssignment(_) | ||
| | SemanticSyntaxErrorKind::IrrefutableCasePattern(_) => {} | ||
| | SemanticSyntaxErrorKind::IrrefutableCasePattern(_) | ||
| | SemanticSyntaxErrorKind::SingleStarredAssignment => {} |
There was a problem hiding this comment.
I got a bit confused as to why there are multiple branches for the same variants 😅
I might be missing something, please correct me if I'm wrong but I'd suggest to move the preview check condition inside the case block to avoid repeating the variants:
SemanticSyntaxErrorKind::ReboundComprehensionVariable
| SemanticSyntaxErrorKind::DuplicateTypeParameter
| SemanticSyntaxErrorKind::MultipleCaseAssignment(_)
| SemanticSyntaxErrorKind::IrrefutableCasePattern(_)
| SemanticSyntaxErrorKind::SingleStarredAssignment => {
if self.settings.preview.is_enabled() {
self.semantic_errors.borrow_mut().push(error);
}
}There was a problem hiding this comment.
I think this was a clippy suggestion when there was only one other variant, but it's definitely getting annoying to update them (and to read them!)
|
MichaReiser
approved these changes
Mar 28, 2025
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Summary
Detects starred assignment targets outside of tuples and lists like
*a = (1,).This PR only considers assignment statements. I also checked annotated assigment statements, but these give a separate error that we already catch, so I think they're okay not to consider:
Fixes #13759
Test Plan
New inline tests, plus a new
SemanticSyntaxErrorfor an existing parser test. I also removed a now-invalid case from an otherwise-valid test fixture.The new semantic error leads to two errors for the case below:
but this matches pyright too.