ExpressionParser { static Parser<Expression> exists(Parser<Relation> relation) { return term("exists").next(relation).map(e -> new UnaryRelationalExpression(e, Op.EXISTS)); }    }
@Test public void testExists() { TerminalParserTest.assertParser(ExpressionParser.exists(RelationParser.TABLE), "exists t", new UnaryRelationalExpression(table("t"), Op.EXISTS)); }