Steps to reproduce:

1. create an app using cli
2. ignite generate model foo
3. try to include using this syntax

import {FooModel} from ".."

export const RootStoreModel = types.model("RootStore").props({
  user: types.maybeNull(FooModel)
})

4. see this error on log
   Error: [mobx-state-tree] expected mobx-state-tree type as argument 1, got undefined instead

How i fixed it:

1. created index.ts file in foo folder inside models
2. add this code export * from "./foo"
3. change the import to

import {FooModel} from "../foo"

I wasted 2 hours of debugging and pulling my hair. only to realize this.