fn parse_mul_assign_rhs_if_allowed(&mut self) -> Result<Vec<Node>, ParseErr> {
        if self.suppress_mul_assign {
            let node = vec![self.parse_arg()?];
            Ok(node)
        } else {
            let mrhs = self.parse_mul_assign_rhs(None)?;
            Ok(mrhs)
        }
    }
Parse rhs of multiple assignment.
If Parser.mul_assign_rhs is true, only a single assignment is allowed.
ruruby-parse/src/parser/expression.rs