I have been receiving this area when trying to wire up ngrx. I cloned the ngrx_exemplary app, and it builds just fine. I tried to reproduce this as minimally as possible, and I'm still receiving the following error:
ERROR in ~/Repos/AngularSandbox/apps/test/src/app/app.module.ts (17,60): Argument of type '(state: Test, action: TestAction) => Test' is not assignable to parameter of type 'ActionReducerMap<{ readonly count: number; }, Action> | InjectionToken<ActionReducerMap<{ readonl...'.
Type '(state: Test, action: TestAction) => Test' is not assignable to type 'InjectionToken<ActionReducerMap<{ readonly count: number; }, Action>>'.
Property '_differentiate_from_OpaqueToken_structurally' is missing in type '(state: Test, action: TestAction) => Test'.
export interface Test {
// define state here
readonly count: number;
}
export interface TestState { readonly test: Test; }
import {Test} from './test.interfaces';
export const testInitialState: Test = {
// fill it initial state here
count: 4
};