in src/CodegenClassish.hack [378:391]
protected function buildManualDeclarations(HackBuilder $builder): void {
if ($this->hasManualHeader) {
$manual_section = CP\coalescevax($this->headerName, $this->name.'_header');
$content = CP\coalescevax(
$this->headerContents,
'// Insert additional consts and vars here',
);
$builder
->ensureEmptyLine()
->startManualSection($manual_section)
->addLine($content)
->endManualSection();
}
}