We're having real problems trying to resolve this and so hoping for some Firebase assistance / those that have solved the same problem.

The app is React Native (0.43.2) and using Firebase JS API (latest)

We provide Facebook and Google auth. Works fine.

BUT, if a user:

1. signs in with Facebook (is ok)
2. later, signs in with Google (is also fine)
3. later, tries to sign in with Facebook - BOOM! not so fine and Firebase returns this error:

`auth/account-exists-with-different-credential`

From reading docs and a few posts on SO, we thought the following was correct but clearly not as we're getting the same auth error back.

```
...error returned by Firebase auth after trying Facebook login...

const email = error.email;
const pendingCred = error.credential;

firebase.auth().fetchProvidersForEmail(email)
.then(providers => {
   //providers returns this array -> ["google.com"]
   firebase.auth().signInWithCredential(pendingCred)
   .then(result => {
       result.user.link(pendingCred)
   })
   .catch(error => log(error))

```

The call to signInWithCredential is throwing the same error `auth/account-exists-with-different-credential`. 

Can anyone help point out what we are doing wrong with this implementation? Greatly appreciated.