Inherit hash from tmp::entry

include/tmp/directory

@@ -4,7 +4,6 @@
 #include <tmp/entry>
 #include <tmp/export>
 
-#include <cstddef>
 #include <filesystem>
 #include <string_view>
 #include <system_error>
@@ -90,8 +89,6 @@ public:
 }    // namespace tmp
 
 /// The template specialization of `std::hash` for `tmp::directory`
-template<> struct TMP_EXPORT std::hash<tmp::directory> {
-  std::size_t operator()(const tmp::directory& directory) const noexcept;
-};
+template<> struct std::hash<tmp::directory> : std::hash<tmp::entry> {};
 
 #endif    // TMP_DIRECTORY_H

include/tmp/file

@@ -4,7 +4,6 @@
 #include <tmp/entry>
 #include <tmp/export>
 
-#include <cstddef>
 #include <filesystem>
 #include <fstream>
 #include <ios>
@@ -173,8 +172,6 @@ private:
 }    // namespace tmp
 
 /// The template specialization of `std::hash` for `tmp::file`
-template<> struct TMP_EXPORT std::hash<tmp::file> {
-  std::size_t operator()(const tmp::file& file) const noexcept;
-};
+template<> struct std::hash<tmp::file> : std::hash<tmp::entry> {};
 
 #endif    // TMP_FILE_H

src/directory.cpp

@@ -3,7 +3,6 @@
 
 #include "create.hpp"
 
-#include <cstddef>
 #include <filesystem>
 #include <string_view>
 #include <system_error>
@@ -65,8 +64,3 @@ directory::~directory() noexcept = default;
 directory::directory(directory&&) noexcept = default;
 directory& directory::operator=(directory&&) noexcept = default;
 }    // namespace tmp
-
-std::size_t std::hash<tmp::directory>::operator()(
-    const tmp::directory& directory) const noexcept {
-  return std::hash<tmp::entry>()(directory);
-}

src/entry.cpp

@@ -207,5 +207,6 @@ bool entry::operator>=(const entry& rhs) const noexcept {
 
 std::size_t
 std::hash<tmp::entry>::operator()(const tmp::entry& entry) const noexcept {
-  return tmp::fs::hash_value(entry);
+  // `std::hash<std::filesystem::path>` was not included in the C++17 standard
+  return filesystem::hash_value(entry);
 }

src/file.cpp

@@ -322,8 +322,3 @@ file::~file() noexcept = default;
 file::file(file&&) noexcept = default;
 file& file::operator=(file&& other) noexcept = default;
 }    // namespace tmp
-
-std::size_t
-std::hash<tmp::file>::operator()(const tmp::file& file) const noexcept {
-  return std::hash<tmp::entry>()(file);
-}