hexLiteral method
Implementation
Parser<ConstantNode> hexLiteral() =>
((string('0x') | string('0X')) &
(pattern('0-9a-fA-F') | char('_')).plus().flatten())
.flatten()
.map(
(s) => ConstantNode(
int.parse(s.substring(2).replaceAll('_', ''), radix: 16),
),
);