type export issue

[waitingsong]

Issue Type: Bug

tsconfig.json

{
  "compilerOptions": {
    "alwaysStrict": true,           /* Parse in strict mode and emit "use strict" for each source file. */
    "declaration": true,            /* Generates corresponding '.d.ts' file. */
    "module": "commonjs",           /* 'commonjs', 'amd', 'system', 'umd' or 'es2015'. */
    "strict": true,                 /* Enable all strict type-checking options. */
    "target": "ES2017",              /* 'ES5', 'ES2015', 'ES2016', 'ES2017', or 'ESNEXT'. */
    "types" : ["node"]
  }
}

package.json

{
  "name": "",
  "version": "1.0.0",
  "description": "",
  "private": true,
  "scripts": {},
  "dependencies": {},
  "devDependencies": {
    "@types/node": "^7.0.12",
    "tslib": "^1.9.0",
    "typescript": "^2.8.1"
  },
  "engines": {
    "node": ">=8.9.0"
  }
} 

config/config.default.ts

export interface Config {
  keys: string
  news: {
    pageSize: number;
  };
}

export type PowerPartial<T> = {
  [U in keyof T]?: T[U] extends {}
  ? PowerPartial<T[U]>
  : T[U]
}

// for config.{env}.ts
export type DefaultConfig = PowerPartial<Config>;

config.local.ts

import { DefaultConfig } from './config.default';

export default () => {
  const config: DefaultConfig = {};

  config.sourceUrl = 'foo'
  config.news = {
    pageSize: 20,
  };

  return config;
}; 

got error:

config/config.local.ts(3,1): error TS4082: Default export of the module has or is using private name 'PowerPartial'.
config/config.local.ts(6,10): error TS2339: Property 'sourceUrl' does not exist on type 'PowerPartial<Config>'.
11:06:36 - Compilation complete. Watching for file changes.

if change to `"declaration": false,``` , then issue gone.
any suggestion ?

VS Code version: Code 1.21.1 (79b44aa, 2018-03-14T14:46:47.128Z)
OS version: Windows_NT x64 6.1.7601

System Info

Item	Value
CPUs	Intel(R) Core(TM) i5 CPU 760 @ 2.80GHz (4 x 2809)
Memory (System)	15.97GB (4.32GB free)
Process Argv	C:\Program Files\Microsoft VS Code\Code.exe E:\project\tt\ts\config\config.local.ts
Screen Reader	no
VM	67%

Extensions: none Reproduces without extensions

[waitingsong]

If change

export interface Config {
  keys: string
  news: {
    pageSize: number;
  };
}

without sub object news, then issue gone

export interface Config {
  keys: string
 // news: {
 //   pageSize: number;
 //  };
}

[waitingsong]

maybe bug of TypeScript ?

[mjbvz]

This issue was moved to microsoft/TypeScript#23280