in src/Merger.hack [25:32]
public static function merge(vec<AutoloadMap> $maps): AutoloadMap {
return dict[
'class' => self::mergeImpl(Vec\map($maps, $map ==> $map['class'])),
'function' => self::mergeImpl(Vec\map($maps, $map ==> $map['function'])),
'type' => self::mergeImpl(Vec\map($maps, $map ==> $map['type'])),
'constant' => self::mergeImpl(Vec\map($maps, $map ==> $map['constant'])),
];
}