unary-expression ::= (custom-operator |
                      'not') prefix-expression

relational-expression ::= bitwise-expression (('==' |
                                               '!=' |
                                               '>' |
                                               '>=' |
                                               '<' |
                                               '<=') bitwise-expression)*

bitwise-expression ::= shift-expression (custom-bitwise-operator shift-expression)*

multiplicative-expression ::= prefix-expression (custom-multiplicative-operator prefix-expression)*

additive-expression ::= multiplicative-expression (custom-additive-operator multiplicative-expression)*

logical-expression ::= relational-expression (('and' |
                                               'or') relational-expression)*

shift-expression ::= additive-expression (custom-shift-operator additive-expression)*