编译器无法识别模板函数中的映射迭代器

我有以下代码。

template<class key,class val>
bool has_key(key chkey,std::map<key,val> map){
  for (std::map<key,val>::iterator it = map.begin(); #line 13 referenced by gcc
      it!=map.end(); ++it){
    if(chkey == it->first) return true;
  }
  return false;
}

GCC给了我以下错误。

objects.hpp: In function `bool has_key(key, std::map<key, val, std::less<_Key>,
  std::allocator<std::pair<const _Key, _Tp> > >)':
objects.hpp:13: error: expected `;' before "it"
objects.hpp:14: error: `it' was not declared in this scope

不知怎的,“它”没有被初始化,这到底是怎么回事?!