angular: TypeError: Cannot read property 'toJSON' of undefined

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Current behavior I get the following error when attempting to run the ngc ahead-of-time compiler in Angular 4.0.0-beta.7:

TypeError: Cannot read property ‘toJSON’ of undefined at TsickleCompilerHost.sourceMapGeneratorToConsumerWithFileName (node_modules\tsickle\build\src\tsickle_compiler_host.js:92:46) at TsickleCompilerHost.combineSourceMaps (node_modules\tsickle\build\src\tsickle_compiler_host.js:124:64) at TsickleCompilerHost.writeFile (node_modules\tsickle\build\src\tsickle_compiler_host.js:78:28) at Object.writeFile (node_modules\typescript\lib\typescript.js:62941:132) at Object.writeFile (node_modules\typescript\lib\typescript.js:8936:14) at printFile (node_modules\typescript\lib\typescript.js:60023:20) at emitFile (node_modules\typescript\lib\typescript.js:59979:21) at onSingleFileEmit (node_modules\typescript\lib\typescript.js:8844:13) at Object.forEachTransformedEmitFile (node_modules\typescript\lib\typescript.js:8821:21) at Object.emitFiles (node_modules\typescript\lib\typescript.js:59962:12) Compilation failed

If I set sourceMap to false in my tsconfig.json file, the compilation works again.

Expected behavior Compilation succeeds without having to disable sourcemaps.

Minimal reproduction of the problem with instructions My full tsconfig.json is as follows:

{
  "compilerOptions": {
    "target": "es5",
    "module": "es2015",
    "moduleResolution": "node",
    "sourceMap": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "lib": ["es2015", "dom"],
    "noImplicitAny": true
  },
  "files": [
    "app/app.module.ts",
    "app/main.ts"
  ],
  "angularCompilerOptions": {
    "genDir": "aot",
    "skipMetadataEmit" : true
  }
}

Please tell us about your environment: Windows Server 2012 R2 (equivalent to Windows 8.1)

• Angular version: 4.0.0-beta.7

• Language: TypeScript 2.1.6

• Node (for AoT issues): node --version = v7.4.0