Method parse_subscript

src/sql-parser/src/parser.rs:1430–1488

Parse subscript expression, i.e. either an index value or slice range.

(&mut self, expr: Expr<Raw>)

    /// Parse subscript expression, i.e. either an index value or slice range.
    fn parse_subscript(&mut self, expr: Expr<Raw>) -> Result<Expr<Raw>, ParserError> {
        let mut positions = Vec::new();

        while self.consume_token(&Token::LBracket) {
            let start = if self.peek_token() == Some(Token::Colon) {
                None
            } else {
                Some(self.parse_expr()?)
            };

            let (end, explicit_slice) = if self.consume_token(&Token::Colon) {
                // Presence of a colon means these positions were explicit
                (
                    // Terminated expr
                    if self.peek_token() == Some(Token::RBracket) {
                        None
                    } else {
                        Some(self.parse_expr()?)
                    },
                    true,
                )
            } else {
                (None, false)
            };

            assert!(
                start.is_some() || explicit_slice,
                "user typed something between brackets"
            );

            assert!(
                explicit_slice || end.is_none(),
                "if end is some, must have an explicit slice"
            );

            positions.push(SubscriptPosition {
                start,
                end,
                explicit_slice,
            });
            self.expect_token(&Token::RBracket)?;
        }

        // If the expression that is being cast can end with a type name, then let's parenthesize
        // it. Otherwise, the `[...]` would melt into the type name (making it an array type).
        // Specifically, the only expressions whose printing can end with a type name are casts, so
        // check for that.
        if matches!(expr, Expr::Cast { .. }) {
            Ok(Expr::Subscript {
                expr: Box::new(Expr::Nested(Box::new(expr))),
                positions,
            })
        } else {
            Ok(Expr::Subscript {
                expr: Box::new(expr),
                positions,
            })
        }