RC7 + webpack-9.4: All declarations of ' ... ' must have identical modifiers.

[alexciesielski]

Please provide us with the following information:

1. OS? Windows 7, 8 or 10. Linux (which distribution). Mac OSX (Yosemite? El Capitan?)

Linux Mint x64

1. Versions. Please run ng --version. If there's nothing outputted, please run
   in a Terminal: node --version and paste the result here:

node v6.5.0
npm 3.10.3
angular-cli 1.0.0-beta.11-webpack.9-4

1. Repro steps. Was this an app that wasn't created using the CLI? What change did you
   do on your code? etc.

a) Upgrade to latest cli and angular rc 7
b) ng init
c) ng serve

1. The log given by the failure. Normally this include a stack trace and some
   more information.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:21:13 
Duplicate identifier 'PropertyKey'.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:85:4 
All declarations of 'name' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:145:4 
Subsequent variable declarations must have the same type.  Variable '[Symbol.unscopables]' must be of type '{ copyWithin: boolean; entries: boolean; fill: boolean; find: boolean; findIndex: boolean; keys: ...', but here has type 'any'.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:262:4 
All declarations of 'flags' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:276:4 
All declarations of 'EPSILON' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:311:4 
All declarations of 'MAX_SAFE_INTEGER' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:318:4 
All declarations of 'MIN_SAFE_INTEGER' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:457:4 
Subsequent variable declarations must have the same type.  Variable '[Symbol.toStringTag]' must be of type '"Symbol"', but here has type 'string'.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:457:4 
All declarations of '[Symbol.toStringTag]' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:464:4 
All declarations of 'prototype' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:492:4 
All declarations of 'hasInstance' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:498:4 
All declarations of 'isConcatSpreadable' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:504:4 
All declarations of 'iterator' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:510:4 
All declarations of 'match' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:516:4 
All declarations of 'replace' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:522:4 
All declarations of 'search' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:528:4 
All declarations of 'species' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:534:4 
All declarations of 'split' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:540:4 
All declarations of 'toPrimitive' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:546:4 
All declarations of 'toStringTag' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:552:4 
All declarations of 'unscopables' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:609:4 
Subsequent variable declarations must have the same type.  Variable '[Symbol.toStringTag]' must be of type '"Math"', but here has type 'string'.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:609:4 
All declarations of '[Symbol.toStringTag]' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:613:4 
Subsequent variable declarations must have the same type.  Variable '[Symbol.toStringTag]' must be of type '"JSON"', but here has type 'string'.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:613:4 
All declarations of '[Symbol.toStringTag]' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:628:4 
All declarations of 'size' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:634:4 
All declarations of 'prototype' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:645:4 
All declarations of 'size' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:651:4 
All declarations of 'prototype' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:666:4 
All declarations of 'prototype' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:680:4 
All declarations of 'prototype' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:692:4 
All declarations of 'value' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/@types/core-js/index.d.ts:804:4 
All declarations of 'prototype' must have identical modifiers.

ERROR in [default] /home/ciesielskico/my-app/node_modules/angular-cli/node_modules/typescript/lib/lib.es2015.core.d.ts:17:13 
Duplicate identifier 'PropertyKey'.

1. Mention any other details that might be useful.

tsconfig.json

{
  "compilerOptions": {
    "declaration": false,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "lib": ["es6", "dom"],
    "mapRoot": "./",
    "module": "es6",
    "moduleResolution": "node",
    "outDir": "../dist/out-tsc",
    "sourceMap": true,
    "target": "es5",
    "typeRoots": [
      "../node_modules/@types"
    ]
  }
}

angular-cli.json

{
  "project": {
    "version": "1.0.0-beta.11-webpack.9-2",
    "name": "my-app"
  },
  "apps": [
    {
      "root": "src",
      "outDir": "dist",
      "assets": "assets",
      "index": "index.html",
      "main": "main.ts",
      "test": "test.ts",
      "tsconfig": "tsconfig.json",
      "prefix": "app",
      "mobile": false,
      "styles": [
        "styles.css"
      ],
      "scripts": [],
      "environments": {
        "source": "environments/environment.ts",
        "dev": "environments/environment.ts",
        "prod": "environments/environment.prod.ts"
      }
    }
  ],
  "addons": [],
  "packages": [],
  "e2e": {
    "protractor": {
      "config": "./protractor.conf.js"
    }
  },
  "test": {
    "karma": {
      "config": "./karma.conf.js"
    }
  },
  "defaults": {
    "styleExt": "css",
    "prefixInterfaces": false
  }
}

[deebloo]

try removing @types/core-js and see if that helps

[alexciesielski]

Thanks, removing @types/core-js from package.json, deleting node_modules and npm installing solved this issue.

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