Styjun

I know there are quite a lot of question about this, I did read most of them (I guess) and they helped me having a better understanding of this error, and how to solve it in most cases.

However I am facing one I could not resolves by myself, so apologies if SO is not the good place for this question (I guess this could be a dupe since there is already questions about this issue, but I did not found any that helped me to solve this "particular case").

I have the following piece of code :

import Request from 'express'
import multer from 'multer'
import path from 'path'

class ImageMiddleware 

 // ...

 private storage (folder: string): multer.StorageEngine 
 return multer.diskStorage( null, destination: string) => void): void => 
 callback(
 null,
 `$file.fieldname`
 + `-`
 + `$Date.now()`
 + `$req.user.id`
 + `$path.extname(file.originalname)`
 )
 ,
 )
 

 // ...


export default new ImageMiddleware()

With this tsconfig.json :

 "compilerOptions": 
 "target": "ES6",
 "module": "commonjs",
 "outDir": "./dist/",
 "sourceMap": true,
 "removeComments": true,
 "pretty": true,
 "noUnusedLocals": true,
 "noUnusedParameters": true,
 "alwaysStrict": true,
 "noImplicitThis": true,
 "noImplicitAny": true,
 "allowUnreachableCode": false,
 "esModuleInterop": true,
 "strict": true
 ,
 "exclude": ["**/spec/*.spec.ts", "./node_modules"]

But when running ./node_modules/typescript/bin/tsc I have the following error :

services/middlewares/image/image.middleware.ts:112:13 - error TS2322: Type '(_req: Request, _file: File, callback: (error: Error | null, destination: string) => void) => void' is not assignable to type 'string | ((req: Request, file: File, callback: (error: Error | null, destination: string) => void) => void) | undefined'.
 Type '(_req: Request, _file: File, callback: (error: Error | null, destination: string) => void) => void' is not assignable to type '(req: Request, file: File, callback: (error: Error | null, destination: string) => void) => void'.
 Types of parameters '_req' and 'req' are incompatible.
 Type 'Request' is missing the following properties from type 'Request': get, header, accepts, acceptsCharsets, and 71 more.

112 destination: (
 ~~~~~~~~~~~

 node_modules/@types/multer/index.d.ts:59:9
 59 destination?: string | ((req: Express.Request, file: Express.Multer.File, callback: (error: Error | null, destination: string) => void) => void);
 ~~~~~~~~~~~
 The expected type comes from property 'destination' which is declared here on type 'DiskStorageOptions'

So I guess that the ): void => { line is wrong, hence I tried a lot of stuff to debug it but did not find anything successfull.

The output of ./node_modules/typescript/bin/tsc -v is Version 3.3.4000

Any help would be welcome, please let me know if I forgot some relevant informations

Because this error is in node_modules the only hope of fixing it is a pull request to the typings repository.

For now to silence the error turn "skipLibCheck": true in tsconfig.

EDIT: Sorry misread where error was coming from.

"Types of parameters '_req' and 'req' are incompatible."
I Suspect if you're using express you've ended up with two types for "Request" there is one in the standard typescript library which 1 function is typed with and another type for "Request" that exists in express that express uses.