Terrible trouble with Map

[isoftninja]

class T {
    static map = new Map<string, object>();
    static getInstanceById(id:string): object {
        if ( !T.map.has( id ) ) {
            T.map.set( id, {} );
        }

        return T.map.get( id ); // >>>
    }
}

/** <<<
 * TS2322: Type 'object | undefined' is not assignable to type 'object'.
 * Type 'undefined' is not assignable to type 'object'.
 */

// very bad!
class T0 {
    static map = new Map<string, object>();
    static getInstanceById(id:string): object {
        let result = T0.map.get( id );

        if ( !result ) {
            result = {};

            T0.map.set( id, result );
        }

        return result;
    }
}
// Good!
class T1 {
    static map = new Map<string, object>();
    static getInstanceById(id:string): object {
        return T1.map.has( id ) ? T1.map.get( id ) : T1.map.set( id, {} ).get( id );
    }
}

[nmain]

Duplicate of #9619

Either use the T0 form or a ! type assertion, or perhaps encapsulate the login from T0 into some sort of getValueOrDefault helper function.

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.