tests/cases/compiler/undeclaredModuleError.ts(1,21): error TS2307: Cannot find external module 'fs'. tests/cases/compiler/undeclaredModuleError.ts(8,29): error TS2345: Argument of type '() => void' is not assignable to parameter of type '(stat: any, name: string) => boolean'. Type 'void' is not assignable to type 'boolean'. tests/cases/compiler/undeclaredModuleError.ts(11,41): error TS2304: Cannot find name 'IDoNotExist'. ==== tests/cases/compiler/undeclaredModuleError.ts (3 errors) ==== import fs = require('fs'); ~~~~ !!! error TS2307: Cannot find external module 'fs'. function readdir(path: string, accept: (stat: fs.Stats, name: string) => boolean, callback: (error: Error, results: { name: string; stat: fs.Stats; }[]) => void ) {} function join(...paths: string[]) {} function instrumentFile(covFileDir: string, covFileName: string, originalFilePath: string) { fs.readFile(originalFilePath, () => { readdir(covFileDir, () => { ~~~~~~~ } , (error: Error, files: {}[]) => { ~~~~~~~~~ !!! error TS2345: Argument of type '() => void' is not assignable to parameter of type '(stat: any, name: string) => boolean'. !!! error TS2345: Type 'void' is not assignable to type 'boolean'. files.forEach((file) => { var fullPath = join(IDoNotExist); ~~~~~~~~~~~ !!! error TS2304: Cannot find name 'IDoNotExist'. } ); } ); } ); }