[syntax-errors] Starred expressions in return, yield, and for

crates/ruff_linter/src/checkers/ast/mod.rs

@@ -552,7 +552,8 @@ impl SemanticSyntaxContext for Checker<'_> {
             | SemanticSyntaxErrorKind::MultipleCaseAssignment(_)
             | SemanticSyntaxErrorKind::IrrefutableCasePattern(_)
             | SemanticSyntaxErrorKind::SingleStarredAssignment
-            | SemanticSyntaxErrorKind::WriteToDebug(_) => {
+            | SemanticSyntaxErrorKind::WriteToDebug(_)
+            | SemanticSyntaxErrorKind::InvalidStarExpression => {
                 if self.settings.preview.is_enabled() {
                     self.semantic_errors.borrow_mut().push(error);
                 }

crates/ruff_python_parser/resources/inline/err/single_star_for.py

@@ -0,0 +1,2 @@
+for _ in *x: ...
+for *x in xs: ...

crates/ruff_python_parser/resources/inline/err/single_star_return.py

@@ -0,0 +1 @@
+def f(): return *x

crates/ruff_python_parser/resources/inline/err/single_star_yield.py

@@ -0,0 +1 @@
+def f(): yield *x

crates/ruff_python_parser/resources/inline/ok/single_star_in_tuple.py

@@ -0,0 +1,4 @@
+def f(): yield (*x,)
+def f(): return (*x,)
+for _ in (*x,): ...
+for (*x,) in xs: ...

crates/ruff_python_parser/resources/valid/expressions/yield.py

@@ -10,7 +10,5 @@
 yield (x, y)
 yield x == y
 yield (x := 1)
-yield *y
 yield x, *y
 yield *x,
-yield *x | y

crates/ruff_python_parser/resources/valid/statement/for.py

@@ -22,19 +22,9 @@
 for (a, b) in iter:
     pass
 
-for target in *x.attr:
-    pass
-
 for target in [1, 2]:
     pass
 
-for *target in a, b, c,:
-    pass
-else:
-    pass
-
-for target in *x | y: ...
-for target in *await x: ...
 for target in await x: ...
 for target in lambda x: x: ...
 for target in x if True else y: ...

crates/ruff_python_parser/resources/valid/statement/return.py

@@ -1,7 +1,5 @@
 return
 return x
-return *x
-return *x | y
 return *x, *y
 return (x := 1)
 return None

crates/ruff_python_parser/src/semantic_errors.rs

@@ -89,12 +89,42 @@ impl SemanticSyntaxChecker {
                     );
                 }
             }
+            Stmt::Return(ast::StmtReturn {
+                value: Some(value), ..
+            }) => {
+                // test_err single_star_return
+                // def f(): return *x
+                Self::invalid_star_expression(value, ctx);
+            }
+            Stmt::For(ast::StmtFor { target, iter, .. }) => {
+                // test_err single_star_for
+                // for _ in *x: ...
+                // for *x in xs: ...
+                Self::invalid_star_expression(target, ctx);
+                Self::invalid_star_expression(iter, ctx);
+            }
             _ => {}
         }
 
         Self::debug_shadowing(stmt, ctx);
     }
 
+    /// Emit a [`SemanticSyntaxErrorKind::InvalidStarExpression`] if `expr` is starred.
+    fn invalid_star_expression<Ctx: SemanticSyntaxContext>(expr: &Expr, ctx: &Ctx) {
+        // test_ok single_star_in_tuple
+        // def f(): yield (*x,)
+        // def f(): return (*x,)
+        // for _ in (*x,): ...
+        // for (*x,) in xs: ...
+        if expr.is_starred_expr() {
+            Self::add_error(
+                ctx,
+                SemanticSyntaxErrorKind::InvalidStarExpression,
+                expr.range(),
+            );
+        }
+    }
+
     /// Check for [`SemanticSyntaxErrorKind::WriteToDebug`] in `stmt`.
     fn debug_shadowing<Ctx: SemanticSyntaxContext>(stmt: &ast::Stmt, ctx: &Ctx) {
         match stmt {
@@ -368,6 +398,13 @@ impl SemanticSyntaxChecker {
                     };
                 }
             }
+            Expr::Yield(ast::ExprYield {
+                value: Some(value), ..
+            }) => {
+                // test_err single_star_yield
+                // def f(): yield *x
+                Self::invalid_star_expression(value, ctx);
+            }
             _ => {}
         }
     }
@@ -462,6 +499,9 @@ impl Display for SemanticSyntaxError {
                     write!(f, "cannot delete `__debug__` on Python {python_version} (syntax was removed in 3.9)")
                 }
             },
+            SemanticSyntaxErrorKind::InvalidStarExpression => {
+                f.write_str("can't use starred expression here")
+            }
         }
     }
 }
@@ -575,6 +615,19 @@ pub enum SemanticSyntaxErrorKind {
     ///
     /// [BPO 45000]: https://github.com/python/cpython/issues/89163
     WriteToDebug(WriteToDebugKind),
+
+    /// Represents the use of a starred expression in an invalid location, such as a `return` or
+    /// `yield` statement.
+    ///
+    /// ## Examples
+    ///
+    /// ```python
+    /// def f(): return *x
+    /// def f(): yield *x
+    /// for _ in *x: ...
+    /// for *x in xs: ...
+    /// ```
+    InvalidStarExpression,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]

crates/ruff_python_parser/tests/snapshots/invalid_syntax@expressions__yield__star_expression.py.snap

@@ -111,3 +111,14 @@ Module(
 4 | yield *x and y, z
   |        ^^^^^^^ Syntax Error: Boolean expression cannot be used here
   |
+
+
+## Semantic Syntax Errors
+
+  |
+1 | # Cannot use starred expression here
+2 | yield (*x)
+  |        ^^ Syntax Error: can't use starred expression here
+3 |
+4 | yield *x and y, z
+  |

crates/ruff_python_parser/tests/snapshots/invalid_syntax@for_stmt_invalid_iter_expr.py.snap

@@ -1,7 +1,6 @@
 ---
 source: crates/ruff_python_parser/tests/fixtures.rs
 input_file: crates/ruff_python_parser/resources/inline/err/for_stmt_invalid_iter_expr.py
-snapshot_kind: text
 ---
 ## AST
 
@@ -182,3 +181,13 @@ Module(
 3 | for target in x := 1: ...
   |                    ^ Syntax Error: Invalid annotated assignment target
   |
+
+
+## Semantic Syntax Errors
+
+  |
+1 | for x in *a and b: ...
+  |          ^^^^^^^^ Syntax Error: can't use starred expression here
+2 | for x in yield a: ...
+3 | for target in x := 1: ...
+  |

crates/ruff_python_parser/tests/snapshots/invalid_syntax@for_stmt_invalid_target.py.snap

@@ -1,7 +1,6 @@
 ---
 source: crates/ruff_python_parser/tests/fixtures.rs
 input_file: crates/ruff_python_parser/resources/inline/err/for_stmt_invalid_target.py
-snapshot_kind: text
 ---
 ## AST
 
@@ -462,3 +461,25 @@ Module(
 7 | for [x, 1, y, *["a"]] in z: ...
   |                 ^^^ Syntax Error: Invalid assignment target
   |
+
+
+## Semantic Syntax Errors
+
+  |
+1 | for 1 in x: ...
+2 | for "a" in x: ...
+3 | for *x and y in z: ...
+  |     ^^^^^^^^ Syntax Error: can't use starred expression here
+4 | for *x | y in z: ...
+5 | for await x in z: ...
+  |
+
+
+  |
+2 | for "a" in x: ...
+3 | for *x and y in z: ...
+4 | for *x | y in z: ...
+  |     ^^^^^^ Syntax Error: can't use starred expression here
+5 | for await x in z: ...
+6 | for yield x in y: ...
+  |

crates/ruff_python_parser/tests/snapshots/invalid_syntax@return_stmt_invalid_expr.py.snap

@@ -1,7 +1,6 @@
 ---
 source: crates/ruff_python_parser/tests/fixtures.rs
 input_file: crates/ruff_python_parser/resources/inline/err/return_stmt_invalid_expr.py
-snapshot_kind: text
 ---
 ## AST
 
@@ -181,3 +180,21 @@ Module(
 5 | return *x and y
   |         ^^^^^^^ Syntax Error: Boolean expression cannot be used here
   |
+
+
+## Semantic Syntax Errors
+
+  |
+1 | return *
+  |        ^ Syntax Error: can't use starred expression here
+2 | return yield x
+3 | return yield from x
+  |
+
+
+  |
+3 | return yield from x
+4 | return x := 1
+5 | return *x and y
+  |        ^^^^^^^^ Syntax Error: can't use starred expression here
+  |

crates/ruff_python_parser/tests/snapshots/invalid_syntax@single_star_for.py.snap

@@ -0,0 +1,107 @@
+---
+source: crates/ruff_python_parser/tests/fixtures.rs
+input_file: crates/ruff_python_parser/resources/inline/err/single_star_for.py
+---
+## AST
+
+```
+Module(
+    ModModule {
+        range: 0..35,
+        body: [
+            For(
+                StmtFor {
+                    range: 0..16,
+                    is_async: false,
+                    target: Name(
+                        ExprName {
+                            range: 4..5,
+                            id: Name("_"),
+                            ctx: Store,
+                        },
+                    ),
+                    iter: Starred(
+                        ExprStarred {
+                            range: 9..11,
+                            value: Name(
+                                ExprName {
+                                    range: 10..11,
+                                    id: Name("x"),
+                                    ctx: Load,
+                                },
+                            ),
+                            ctx: Load,
+                        },
+                    ),
+                    body: [
+                        Expr(
+                            StmtExpr {
+                                range: 13..16,
+                                value: EllipsisLiteral(
+                                    ExprEllipsisLiteral {
+                                        range: 13..16,
+                                    },
+                                ),
+                            },
+                        ),
+                    ],
+                    orelse: [],
+                },
+            ),
+            For(
+                StmtFor {
+                    range: 17..34,
+                    is_async: false,
+                    target: Starred(
+                        ExprStarred {
+                            range: 21..23,
+                            value: Name(
+                                ExprName {
+                                    range: 22..23,
+                                    id: Name("x"),
+                                    ctx: Store,
+                                },
+                            ),
+                            ctx: Store,
+                        },
+                    ),
+                    iter: Name(
+                        ExprName {
+                            range: 27..29,
+                            id: Name("xs"),
+                            ctx: Load,
+                        },
+                    ),
+                    body: [
+                        Expr(
+                            StmtExpr {
+                                range: 31..34,
+                                value: EllipsisLiteral(
+                                    ExprEllipsisLiteral {
+                                        range: 31..34,
+                                    },
+                                ),
+                            },
+                        ),
+                    ],
+                    orelse: [],
+                },
+            ),
+        ],
+    },
+)
+```
+## Semantic Syntax Errors
+
+  |
+1 | for _ in *x: ...
+  |          ^^ Syntax Error: can't use starred expression here
+2 | for *x in xs: ...
+  |
+
+
+  |
+1 | for _ in *x: ...
+2 | for *x in xs: ...
+  |     ^^ Syntax Error: can't use starred expression here
+  |