export interface Config {
  files: ConfigFiles
}

export interface ConfigFiles {
  jspm: string;
  'jspm:browser': string;
  'jspm:dev': string;
  'jspm:node': string;
}

let configFiles: ConfigFiles;
configFile.jspm = '' // autocomplete works
configFiles['jspm:dev'] = '' // autocomplete possible?

let config: Config;
config = {
  files: {
    jspm: '' // autocomplete works
    'jspm:dev': '' // autocomplete possible?
} as Config;