src/vs/workbench/contrib/extensions/browser/extensionsViews.ts/ExtensionsListView/filterBuiltinExtensions
class ExtensionsListView:	private filterBuiltinExtensions(local: IExtension[], query: Query, options: IQueryOptions): IExtension[] {
		let value = query.value;
		const showThemesOnly = /@builtin:themes/i.test(value);
		if (showThemesOnly) {
			value = value.replace(/@builtin:themes/g, '');
		}
		const showBasicsOnly = /@builtin:basics/i.test(value);
		if (showBasicsOnly) {
			value = value.replace(/@builtin:basics/g, '');
		}
		const showFeaturesOnly = /@builtin:features/i.test(value);
		if (showFeaturesOnly) {
			value = value.replace(/@builtin:features/g, '');
		}

		value = value.replace(/@builtin/g, '').replace(/@sort:(\w+)(-\w*)?/g, '').trim().toLowerCase();

		const result = local
			.filter(e => e.isBuiltin && (e.name.toLowerCase().indexOf(value) > -1 || e.displayName.toLowerCase().indexOf(value) > -1));

		const isThemeExtension = (e: IExtension): boolean => {
			return (Array.isArray(e.local?.manifest?.contributes?.themes) && e.local!.manifest!.contributes!.themes.length > 0)
				|| (Array.isArray(e.local?.manifest?.contributes?.iconThemes) && e.local!.manifest!.contributes!.iconThemes.length > 0);
		};
		if (showThemesOnly) {
			const themesExtensions = result.filter(isThemeExtension);
			return this.sortExtensions(themesExtensions, options);
		}

		const isLangaugeBasicExtension = (e: IExtension): boolean => {
			return FORCE_FEATURE_EXTENSIONS.indexOf(e.identifier.id) === -1
				&& (Array.isArray(e.local?.manifest?.contributes?.grammars) && e.local!.manifest!.contributes!.grammars.length > 0);
		};
		if (showBasicsOnly) {
			const basics = result.filter(isLangaugeBasicExtension);
			return this.sortExtensions(basics, options);
		}
		if (showFeaturesOnly) {
			const others = result.filter(e => {
				return e.local
					&& e.local.manifest
					&& !isThemeExtension(e)
					&& !isLangaugeBasicExtension(e);
			});
			return this.sortExtensions(others, options);
		}

		return this.sortExtensions(result, options);
	}