Method parse_lambda_expr

crates/ruff_python_parser/src/parser/expression.rs:2893–2934

Parses a lambda expression. # Panics If the parser isn't positioned at a `lambda` token. See:

(&mut self)

    ///
    /// See: <https://docs.python.org/3/reference/expressions.html#lambda>
    fn parse_lambda_expr(&mut self) -> ast::ExprLambda {
        let start = self.node_start();
        self.bump(TokenKind::Lambda);

        let parameters = if self.at(TokenKind::Colon) {
            // test_ok lambda_with_no_parameters
            // lambda: 1
            None
        } else {
            Some(Box::new(self.parse_parameters(FunctionKind::Lambda)))
        };

        self.expect(TokenKind::Colon);

        // test_ok lambda_with_valid_body
        // lambda x: x
        // lambda x: x if True else y
        // lambda x: await x
        // lambda x: lambda y: x + y
        // lambda x: (yield x)  # Parenthesized `yield` is fine
        // lambda x: x, *y

        // test_err lambda_body_with_starred_expr
        // lambda x: *y
        // lambda x: *y,
        // lambda x: *y, z
        // lambda x: *y and z

        // test_err lambda_body_with_yield_expr
        // lambda x: yield y
        // lambda x: yield from y

        // Lambda bodies recurse through the conditional layer without entering the binary parser.
        let body = self.with_recursion(Self::parse_conditional_expression_or_higher);

        ast::ExprLambda {
            body: Box::new(body.expr),
            parameters,
            range: self.node_range(start),
            node_index: AtomicNodeIndex::NONE,
        }
    }

    /// Parses an `if` expression.
    ///