std::experimental::filesystem::（中略）::directory_entryにexists等がないと言われる

前提・実現したいこと

https://github.com/ElonaFoobar/ElonaFoobar
上記リポジトリをコンパイルしようとしました。

// ライブラリ等の準備
brew install make
????  /usr/local/Cellar/make/4.2.1_1: 15 files, 956KB
brew install lua
????  /usr/local/Cellar/lua/5.3.4_3: 147 files, 753KB
brew install gcc
????  /usr/local/Cellar/gcc/7.3.0_1: 1,487 files, 285.9MB, built in 65 minutes 39 seconds

また、SDL関連を配布サイトからダウンロードし、readmeに従いファイルを移動させました。

$ pwd
/Library/Frameworks

$ ls
AEProfiling.framework		SDL2.framework
AERegistration.framework	SDL2_image.framework
AudioMixEngine.framework	SDL2_mixer.framework
NyxAudioAnalysis.framework	SDL2_ttf.framework
PluginManager.framework		iTunesLibrary.framework

ElonaFooBarディレクトリでmakeを実行したところ/usr/local/bin/g++-HEADがないと言われたため、CXX := /usr/local/bin/g++-7に書き換えました。
その後makeを実行したところ、以下のエラーメッセージが出てコンパイルに失敗します。

発生している問題・エラーメッセージ

$ make
/usr/local/Cellar/gcc/7.3.0_1/bin/g++-7 -Werror -Wall -Wextra -g -O0 -MMD -DDEBUG -std=c++17 -I/usr/local/include -I./thirdparty -I/usr/local/Cellar/gcc/7.3.0_1/lib/gcc/7  -c ability.cpp -o bin/./ability.o
In file included from cat.hpp:5:0,
                 from ability.hpp:7,
                 from ability.cpp:1:
filesystem.hpp: In instantiation of 'elona::filesystem::dir_entries::begin() const::<lambda(const auto:1&)> [with auto:1 = std::experimental::filesystem::v1::__cxx11::directory_iterator]':
/usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/type_traits:2428:26:   required by substitution of 'template<class _Fn, class ... _Args> static std::__result_of_success<decltype (declval<_Fn>()((declval<_Args>)()...)), std::__invoke_other> std::__result_of_other_impl::_S_test(int) [with _Fn = elona::filesystem::dir_entries::begin() const::<lambda(const auto:1&)>&; _Args = {std::experimental::filesystem::v1::__cxx11::directory_iterator}]'
/usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/type_traits:2439:55:   required from 'struct std::__result_of_impl<false, false, elona::filesystem::dir_entries::begin() const::<lambda(const auto:1&)>&, std::experimental::filesystem::v1::__cxx11::directory_iterator>'
/usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/type_traits:2444:12:   required from 'struct std::__invoke_result<elona::filesystem::dir_entries::begin() const::<lambda(const auto:1&)>&, std::experimental::filesystem::v1::__cxx11::directory_iterator>'
/usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/type_traits:2457:12:   required from 'class std::result_of<elona::filesystem::dir_entries::begin() const::<lambda(const auto:1&)>&(std::experimental::filesystem::v1::__cxx11::directory_iterator)>'
/usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/bits/std_function.h:464:9:   required by substitution of 'template<class _Functor, class, class> std::function<bool(std::experimental::filesystem::v1::__cxx11::directory_iterator)>::function(_Functor) [with _Functor = elona::filesystem::dir_entries::begin() const::<lambda(const auto:1&)>; <template-parameter-1-2> = void; <template-parameter-1-3> = <missing>]'
filesystem.hpp:134:18:   required from here
filesystem.hpp:114:31: error: 'const class std::experimental::filesystem::v1::__cxx11::directory_entry' has no member named 'exists'
                     if (!itr->exists())
                          ~~~~~^~~~~~
filesystem.hpp:119:35: error: 'const class std::experimental::filesystem::v1::__cxx11::directory_entry' has no member named 'is_directory'
                         if (!itr->is_directory())
                              ~~~~~^~~~~~~~~~~~
filesystem.hpp:125:35: error: 'const class std::experimental::filesystem::v1::__cxx11::directory_entry' has no member named 'is_regular_file'
                         if (!itr->is_regular_file())
                              ~~~~~^~~~~~~~~~~~~~~
make: *** [bin/./ability.o] Error 1

該当のソースコード

makefileはhttps://github.com/ElonaFoobar/ElonaFoobar/blob/master/Makefileを書き換え、最終的に以下のようになっています。

CXX := /usr/local/Cellar/gcc/7.3.0_1/bin/g++-7
CXX_FLAGS := -Werror -Wall -Wextra -g -O0 -MMD -DDEBUG -std=c++17 -I/usr/local/include -I./thirdparty -I/usr/local/Cellar/gcc/7.3.0_1/lib/gcc/7 $(EX_CXX_FLAGS)
LN_FLAGS := -lstdc++fs -L/usr/local/lib -lSDL2 -lSDL2_image -lSDL2_ttf -lSDL2_mixer -llua
BIN_DIR := bin
SRC_DIR := .
SOURCES := $(wildcard $(SRC_DIR)/*.cpp)
OBJECTS := $(foreach i, $(SOURCES), $(BIN_DIR)/$(basename $(i)).o)
RUNTIME_DIR := ./runtime
PROGRAM := $(RUNTIME_DIR)/elonafoobar


FORMAT := clang-format
FIND := find
XARGS := xargs
MKDIR := mkdir


.PHONY: FORCE clean cleandep


all: build


build: $(RUNTIME_DIR) $(BIN_DIR) $(PROGRAM)


$(RUNTIME_DIR):
	$(MKDIR) $(RUNTIME_DIR)


$(BIN_DIR):
	$(MKDIR) $(BIN_DIR)


$(PROGRAM): $(OBJECTS) snail/snail.a
	$(CXX) $(CXX_FLAGS) $^ -o $@ $(LN_FLAGS)


snail/snail.a: FORCE
	cd snail; make


$(BIN_DIR)/%.o: $(SRC_DIR)/%.cpp
	$(CXX) $(CXX_FLAGS) -c $< -o $@


clean:
	-@$(RM) -f $(PROGRAM)
	$(MAKE) cleandep
	-@$(RM) -f $(BIN_DIR)/*.o


format: FORCE
	$(FIND) $(SRC_DIR) ( -name "*.cpp" -or -name "*.hpp" ) -print0 | $(XARGS) -0 $(FORMAT) -i


checksyntax:
	$(MAKE) EX_CXX_FLAGS=-fsyntax-only


cleandep:
	-@$(RM) -f $(BIN_DIR)/*.d



rebuild: clean build


-include $(BIN_DIR)/*.d

エラーの発生したファイルはこちらです。

cpp
1// https://github.com/ElonaFoobar/ElonaFoobar/blob/master/filesystem.hpp
2#pragma once
3
4#if __has_include(<filesystem>)
5#include <filesystem>
6namespace fs = std::filesystem;
7#else
8#include <experimental/filesystem>
9namespace fs = std::experimental::filesystem;
10#endif
11#include <functional>
12#include <regex>
13#include "range.hpp"
14
15
16
17namespace elona::filesystem
18{
19
20
21struct dir_entries
22{
23    enum class type
24    {
25        dir,
26        file,
27        all,
28    };
29
30
31    dir_entries(
32        const fs::path& base_dir,
33        type entry_type,
34        const std::regex& pattern = std::regex{u8".*"})
35        : base_dir(base_dir)
36        , entry_type(entry_type)
37        , pattern(pattern)
38    {
39    }
40
41
42    struct iterator
43    {
44        using value_type = fs::directory_iterator::value_type;
45        using difference_type = fs::directory_iterator::difference_type;
46        using pointer = fs::directory_iterator::pointer;
47        using reference = fs::directory_iterator::reference;
48        using iterator_category = fs::directory_iterator::iterator_category;
49
50
51        // begin
52        iterator(
53            const fs::directory_iterator& itr,
54            std::function<bool(const fs::directory_iterator)> predicate)
55            : itr(itr)
56            , predicate(predicate)
57        {
58            while (predicate(this->itr))
59            {
60                ++this->itr;
61            }
62        }
63
64
65        // end
66        iterator()
67        {
68        }
69
70
71        void operator++()
72        {
73            do
74            {
75                ++itr;
76            } while (predicate(itr));
77        }
78
79
80        reference operator*() const
81        {
82            return *itr;
83        }
84
85
86        pointer operator->() const
87        {
88            return itr.operator->();
89        }
90
91
92        bool operator==(const iterator& other) const
93        {
94            return itr == other.itr;
95        }
96
97
98        bool operator!=(const iterator& other) const
99        {
100            return itr != other.itr;
101        }
102
103
104    private:
105        fs::directory_iterator itr;
106        std::function<bool(const fs::directory_iterator)> predicate;
107    };
108
109
110    iterator begin() const
111    {
112        return {fs::directory_iterator{base_dir}, [this](const auto& itr) {
113                    if (itr == fs::directory_iterator{})
114                        return false;
115                    if (!itr->exists())
116                        return true;
117                    switch (entry_type)
118                    {
119                    case type::dir:
120                        if (!itr->is_directory())
121                        {
122                            return true;
123                        }
124                        break;
125                    case type::file:
126                        if (!itr->is_regular_file())
127                        {
128                            return true;
129                        }
130                        break;
131                    case type::all: break;
132                    }
133                    return !std::regex_match(
134                        itr->path().filename().generic_u8string(), pattern);
135                }};
136    }
137
138
139    iterator end() const
140    {
141        return {};
142    }
143
144
145private:
146    const fs::path base_dir;
147    const type entry_type;
148    const std::regex pattern;
149};
150
151
152
153} // namespace elona::filesystem

試したこと

エラー文を見るとstdライブラリの中のdirectory_entryのメソッドがないと言われていたので、きっとライブラリを参照し損ねているのだと思い、makeファイルのCXX_FLAGSのオプションにusr/local/Cellar/gcc/7.3.0_1/lib/gcc/7を追加しました。それでもエラーは変わらず発生したので、 CXX := /usr/local/Cellar/gcc/7.3.0_1/bin/g++-7に試しに変更してみましたが、エラーは直りませんでした。