Non-terminal symbol `OperatorExpression`

Defining rules for nonterminal symbol OperatorExpression:

`OperatorExpression`		`Operator`
		`OPERATOR_` `Expression`
		`Expression` `_OPERATOR`
		`Expression` `_OPERATOR_` `Expression`

Occurrences of symbol OperatorExpression in body of other rules:

UntypedExpression OperatorExpression

Non-terminal symbol OperatorExpression