什么样的C ++模板编程可以称为“元编程”？(What kind of C++ template programming can be called “meta programming”? [closed])

 在@GünterZöchbauer的帮助下，我把这件事理顺了。 因此添加return语句将解决类型不匹配问题。 这是通过编译器检查的修改代码。 
 
  loadHero1(id: number) {
      this.hero$ = this._cachedHeroes.map(heroes => heroes.find(hero => { return hero._id === id; } )) 
                                     .catch(handleError)
                                     .map( (data : Hero) => {  
                                                            this._dataStore.hero = data;
                                                            this._heroObserver.next(this._dataStore.hero);
                                                            return data;
                                                         } 
                                                  //error => handleError('Could not load hero.')
                                               );
  }

With the help of @Günter Zöchbauer, I got this thing straighten out. So adding return statement will resolve the type mismatch. Here is the modified code that passed the compiler check.
 
  loadHero1(id: number) {
      this.hero$ = this._cachedHeroes.map(heroes => heroes.find(hero => { return hero._id === id; } )) 
                                     .catch(handleError)
                                     .map( (data : Hero) => {  
                                                            this._dataStore.hero = data;
                                                            this._heroObserver.next(this._dataStore.hero);
                                                            return data;
                                                         } 
                                                  //error => handleError('Could not load hero.')
                                               );
  }