in src/CodegenConstant.hack [52:64]
public function appendToBuilder(HackBuilder $builder): HackBuilder {
$value = $this->getValue();
invariant($value !== null, 'constants must have a value');
$type = $this->getType();
return $builder
->addDocBlock($this->getDocBlock())
->ensureNewLine()
->add('const ')
->addIf($type !== null, ($type ?? '').' ')
->add($this->getName())
->add(' = '.$value)
->addLine(';');
}