constructor(type, filepath, closureSymbols, imports, language = 'es3') {
    /** @const */
    this.type = type;

    /**
     * Full path of this file on disc.
     * @const
     */
    this.path = path.resolve(filepath);

    /**
     * Array of Closure symbols this file provides.
     * @const
     */
    this.closureSymbols = closureSymbols;

    /**
     * Array of imports in this file.
     * @const
     */
    this.imports = imports;

    for (const i of this.imports) {
      i.from = this;
    }

    /**
     * The language level of this file; e.g. "es3", "es6", etc.
     * @const
     */
    this.language = language;
  }
@param {!DependencyType} type
@param {string} filepath
@param {!Array<string>} closureSymbols
@param {!Array<!Import>} imports
@param {string=} language