Type 'BehaviorSubject<false>' is not assignable to type 'BehaviorSubject<boolean>'

Question

I have this in one of my components:

public booleanSubject: BehaviorSubject<boolean> = new BehaviorSubject(false);

When I add "strictFunctionTypes": true to the tsconfig.json file I get the following error:

× Compiling TypeScript sources through NGC
ERROR: path/to/my/component.component.ts:28:10 - error TS2322: Type 'BehaviorSubject<false>' is not assignable to type 'BehaviorSubject<boolean>'.
  Types of property 'observers' are incompatible.
    Type 'Observer<false>[]' is not assignable to type 'Observer<boolean>[]'.
      Type 'Observer<false>' is not assignable to type 'Observer<boolean>'.
        Type 'boolean' is not assignable to type 'false'.

28   public booleanSubject: BehaviorSubject<boolean> = new BehaviorSubject(false);

Does anyone know the reason and how to get it not to throw the error by keeping the strictFunctionTypes flag set to true?

Answer 1

Normally when I create a BehaviorSubject I just assign a type to it when initializing it. Try to it like this:

public booleanSubject = new BehaviorSubject<boolean>(false);

Doing so it will initialize the BehaviorSubject type as boolean and I believe the error will go away.