src/vs/workbench/services/dialogs/browser/simpleFileDialog.ts/SimpleFileDialog/showSaveDialog
class SimpleFileDialog:	public async showSaveDialog(options: ISaveDialogOptions): Promise<URI | undefined> {
		this.scheme = this.getScheme(options.availableFileSystems, options.defaultUri);
		this.userHome = await this.getUserHome();
		this.requiresTrailing = true;
		const newOptions = this.getOptions(options, true);
		if (!newOptions) {
			return Promise.resolve(undefined);
		}
		this.options = newOptions;
		this.options.canSelectFolders = true;
		this.options.canSelectFiles = true;

		return new Promise<URI | undefined>((resolve) => {
			this.pickResource(true).then(folderUri => {
				resolve(folderUri);
			});
		});
	}