src/vs/editor/common/languageFeatureRegistry.ts/isExclusive
function isExclusive(selector: LanguageSelector): boolean {
	if (typeof selector === 'string') {
		return false;
	} else if (Array.isArray(selector)) {
		return selector.every(isExclusive);
	} else {
		return !!(selector as LanguageFilter).exclusive; // TODO: microsoft/TypeScript#42768
	}
}