编译器错误:(枚举类）未在此范围内声明

Question

我正在尝试编译以下程序，该程序使用名为Noun的枚举类。它从字符串中获取输入并使用映射枚举数据。

以下是定义枚举类的头文件：

nouns.h

#ifndef NOUNS_H
#define NOUNS_H

#include <iostream>
#include <map>          //std::map
#include <string>       //std::string

#include "classes.h"    // where classes are stored
#include "functions.h"  // standard functions kept here
#include "cmdtree.h"    // where the arguments from these functions are sent


enum class Noun
{
    name,                   
    /* other nouns */
    invalid         
};

std::map < std::string, Noun > knownNouns = 
{
    {   "name",         Noun::name          },
    /* more stuff in the map */
    {   "suspect",      Noun::suspect       }
};

Noun parseNoun(std::string &noun)
{
    auto n = knownNouns.find(noun);
    if ( n == knownNouns.end() ) {
        return Noun::invalid;
    }
    return n->second;
}

void ask (Noun noun);
void look (Noun noun);

#endif  /* NOUNS_H */

编译时，我遇到了一些错误：

In file included from functions.h:16:0,
                 from classes.h:15,
                 from nouns.h:37,
                 from nouns.cpp:1:
verbs.h:44:15: error: 'Noun' was not declared in this scope
 int verbProc (Noun noun, Verb verb);
               ^
verbs.h:44:31: error: expected primary-expression before 'verb'
 int verbProc (Noun noun, Verb verb);
                               ^
verbs.h:44:35: error: expression list treated as compound expression in initializer [-fpermissive]
 int verbProc (Noun noun, Verb verb);
                                   ^
In file included from classes.h:15:0,
                 from nouns.h:37,
                 from nouns.cpp:1:
functions.h:23:32: error: 'Noun' has not been declared
 char validateInput (Verb verb, Noun noun);
                                ^

在verbs.h中，它告诉我“名词”未在范围内声明，我查看我的头文件......

verbs.h：

#ifndef VERBS_H
#define VERBS_H

#include <iostream>
#include <map>
#include <string>

#include "nouns.h"
#include "classes.h"
#include "functions.h"
/*
 * See the nouns.h header for better documentation on what exactly this
 * is doing.
 */

    enum class Verb
    {
        ask,        // first verb
        /* other verbs */
        invalid     // last verb

    };

    std::map < std::string, Verb > knownVerbs =
    {                                       
        {   "ask",      Verb::ask       },  
        /* other stuff in map */
        {   "examine",  Verb::look      }
    };

    Verb parseVerb(const std::string &verb);
    int verbProc (Noun noun, Verb verb);        // <-- function where Noun is "undeclared."

    #endif  /* VERBS_H */

类似的非延迟错误发生在“functions.h”中：

#ifndef FUNCTIONS_H     
#define FUNCTIONS_H    

#include <iostream>
#include <string>
#include <cstring>

#include "classes.h"
#include "verbs.h"
#include "nouns.h"
#include "classes.h"
#include "cmdtree.h"

void localPause ();
void readInput (char* &command, const int MAXL, std::string &noun, std::string &verb);
char verifyExit(char exitChoice);
char validateInput (Verb verb, Noun noun); //  <-- error here, "Noun has not been declared"
void initializeSuspect();
void introduction();

#endif  /* FUNCTIONS_H */

有人能发现我不能发现的东西吗？