myCustomType.ts

export class MyCustomType {
 ...
}

export class MyCustomTypeManager {
    public list: Array<(data: string) => MyCustomType>;
    public new(input : string, settings? : Object) {
        return new MyCustomType(input, settings);
    }
    public getByName(name) {
        return this.list[name]; // compiler thinks this return value is an Array<(data: string) => MyCustomType>
    }
    ...
}