src/vs/platform/extensionManagement/electron-sandbox/extensionTipsService.ts/ExtensionTipsService/groupByInstalled
class ExtensionTipsService:	private groupByInstalled(recommendationsToSuggest: string[], local: ILocalExtension[]): { installed: string[], uninstalled: string[] } {
		const installed: string[] = [], uninstalled: string[] = [];
		const installedExtensionsIds = local.reduce((result, i) => { result.add(i.identifier.id.toLowerCase()); return result; }, new Set<string>());
		recommendationsToSuggest.forEach(id => {
			if (installedExtensionsIds.has(id.toLowerCase())) {
				installed.push(id);
			} else {
				uninstalled.push(id);
			}
		});
		return { installed, uninstalled };
	}