Method parse_infix

src/sql-parser/src/parser.rs:1277–1427

Parse an operator following an expression

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

    /// Parse an operator following an expression
    fn parse_infix(
        &mut self,
        expr: Expr<Raw>,
        precedence: Precedence,
    ) -> Result<Expr<Raw>, ParserError> {
        let tok = self.next_token().unwrap(); // safe as EOF's precedence is the lowest

        let regular_binary_operator = match &tok {
            Token::Op(s) => Some(Op::bare(s)),
            Token::Eq => Some(Op::bare("=")),
            Token::Star => Some(Op::bare("*")),
            Token::Keyword(OPERATOR) => {
                self.expect_token(&Token::LParen)?;
                let op = self.parse_operator()?;
                self.expect_token(&Token::RParen)?;
                Some(op)
            }
            _ => None,
        };

        if let Some(op) = regular_binary_operator {
            if let Some(kw) = self.parse_one_of_keywords(ANY_ALL_KEYWORDS) {
                self.parse_any_all(expr, op, kw)
            } else {
                Ok(Expr::Op {
                    op,
                    expr1: Box::new(expr),
                    expr2: Some(Box::new(self.parse_subexpr(precedence)?)),
                })
            }
        } else if let Token::Keyword(kw) = tok {
            match kw {
                IS => {
                    let negated = self.parse_keyword(NOT);
                    if let Some(construct) =
                        self.parse_one_of_keywords(&[NULL, TRUE, FALSE, UNKNOWN, DISTINCT])
                    {
                        let construct = match construct {
                            NULL => IsExprConstruct::Null,
                            TRUE => IsExprConstruct::True,
                            FALSE => IsExprConstruct::False,
                            UNKNOWN => IsExprConstruct::Unknown,
                            DISTINCT => {
                                self.expect_keyword(FROM)?;
                                // Parse the right-hand side at the precedence of
                                // the `IS` operator we are in the middle of, not
                                // at `Precedence::Zero`. Otherwise we greedily
                                // pull a trailing `AND`/`OR` into the RHS and
                                // parse `a IS DISTINCT FROM b AND c` as `a IS
                                // DISTINCT FROM (b AND c)`. `IS DISTINCT FROM`
                                // binds tighter than `AND`/`OR` (and looser than
                                // comparison and arithmetic), matching
                                // PostgreSQL.
                                let expr = self.parse_subexpr(precedence)?;
                                IsExprConstruct::DistinctFrom(Box::new(expr))
                            }
                            _ => unreachable!(),
                        };