extensions/typescript-language-features/src/typeScriptServiceClientHost.ts/TypeScriptServiceClientHost/getAllModeIds
class TypeScriptServiceClientHost:	private getAllModeIds(descriptions: LanguageDescription[], pluginManager: PluginManager) {
		return [
			...descriptions.map(x => x.languageIds),
			...pluginManager.plugins.map(x => x.languages)
		].flat();
	}