'failed to produce diagnostic for expression, Xcode 11.4, Moya

After updating to Xcode 11.4, I started to get this error

Failed to produce diagnostic for expression please file a bug report

On:

let provider = MoyaProvider<EndPoint>(requestClosure: requestClosure)

I updated Moya but it doesn't look like the issue. Runs fine on previous Xcode versions.

full code:

 let requestClosure: MoyaProvider.RequestClosure = {
            [unowned self] (endpoint: Endpoint, done: @escaping MoyaProvider.RequestResultClosure) in

       guard let request = try? endpoint.urlRequest() else { return }

       self.authenticator.authenticate(request, done: { (request) in
                done(.success(request))
       })
 }
 provider = MoyaProvider<EndPoint>(requestClosure: requestClosure

Solution 1:^[1]

I found the issue, Xcode 11.4 compile issues are not verbose enough when it comes to optionals and generics.

Moya version and Swift version were not changed.

An issue with generics:

let requestClosure: MoyaProvider<EndPoint>.RequestClosure Had to explicitly define the type in the closure, which makes sense, but was not a requirement pre-Xcode version 11.4

let requestClosure: MoyaProvider<EndPoint>.RequestClosure = {
            [unowned self] (endpoint: Endpoint, done: @escaping MoyaProvider.RequestResultClosure) in

       guard let request = try? endpoint.urlRequest() else { return }

       self.authenticator.authenticate(request, done: { (request) in
          done(.success(request))
      })
}
provider = MoyaProvider<EndPoint>(requestClosure: requestClosure

Solution 2:^[2]

For me the I was getting that error because one of my property was of type Error and I was assigning a value of type LocalizedError to it. Changing the property type to LocalizedError fixed the problem.

Solution 3:^[3]

It seems to be an Xcode bug for some cases at least. I renamed a protocol and then renamed it back and the issue was gone.

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	Tal Zion
Solution 2	EasySkankin
Solution 3	Abdurrahman Mubeen Ali

'failed to produce diagnostic for expression, Xcode 11.4, Moya

Solution 1:[1]

Solution 2:[2]

Solution 3:[3]

Sources

Related Questions

Solution 1:^[1]

Solution 2:^[2]

Solution 3:^[3]