Method parse_parameter

crates/ruff_python_parser/src/parser/statement.rs:3152–3241

Parses a single parameter for the given function kind. Matches either the `param_no_default_star_annotation` or `param_no_default` rule in the [Python grammar] depending on whether star annotation is allowed or not. Use [`Parser::parse_parameter_with_default`] to allow parameter with default values. [Python grammar]: https://docs.python.org/3/reference/grammar.html

(
        &mut self,
        start: TextSize,
        function_kind: FunctionKind,
        allow_star_annotation: AllowStarAnnotation,
    )

    ///
    /// [Python grammar]: https://docs.python.org/3/reference/grammar.html
    fn parse_parameter(
        &mut self,
        start: TextSize,
        function_kind: FunctionKind,
        allow_star_annotation: AllowStarAnnotation,
    ) -> ast::Parameter {
        let name = self.parse_identifier();

        // Annotations are only allowed for function definition. For lambda expression,
        // the `:` token would indicate its body.
        let annotation = match function_kind {
            FunctionKind::FunctionDef if self.eat(TokenKind::Colon) => {
                if self.at_expr() {
                    let parsed_expr = match allow_star_annotation {
                        AllowStarAnnotation::Yes => {
                            // test_ok param_with_star_annotation
                            // def foo(*args: *int | str): ...
                            // def foo(*args: *(int or str)): ...

                            // test_err param_with_invalid_star_annotation
                            // def foo(*args: *): ...
                            // def foo(*args: (*tuple[int])): ...
                            // def foo(*args: *int or str): ...
                            // def foo(*args: *yield x): ...
                            // # def foo(*args: **int): ...
                            let parsed_expr = self.parse_conditional_expression_or_higher_impl(
                                ExpressionContext::starred_bitwise_or(),
                            );

                            // test_ok param_with_star_annotation_py311
                            // # parse_options: {"target-version": "3.11"}
                            // def foo(*args: *Ts): ...

                            // test_ok param_with_star_annotation_py310
                            // # parse_options: {"target-version": "3.10"}
                            // # regression tests for https://github.com/astral-sh/ruff/issues/16874
                            // # starred parameters are fine, just not the annotation
                            // from typing import Annotated, Literal
                            // def foo(*args: Ts): ...
                            // def foo(*x: Literal["this should allow arbitrary strings"]): ...
                            // def foo(*x: Annotated[str, "this should allow arbitrary strings"]): ...
                            // def foo(*args: str, **kwds: int): ...
                            // def union(*x: A | B): ...

                            // test_err param_with_star_annotation_py310
                            // # parse_options: {"target-version": "3.10"}
                            // def foo(*args: *Ts): ...
                            if parsed_expr.is_starred_expr() {
                                self.add_unsupported_syntax_error(
                                    UnsupportedSyntaxErrorKind::StarAnnotation,
                                    parsed_expr.range(),
                                );
                            }

                            parsed_expr
                        }
                        AllowStarAnnotation::No => {
                            // test_ok param_with_annotation