[libc++][NFC] Fix include guard for decay_copy.h and remove underscores from the header

We don't use double underscores for private header names when they are
in a subdirectory with double underscores already.

Differential Revision: https://reviews.llvm.org/D108820

libcxx/include/CMakeLists.txt

@@ -264,9 +264,9 @@ set(files
   __tree
   __tuple
   __undef_macros
-  __utility/__decay_copy.h
   __utility/as_const.h
   __utility/cmp.h
+  __utility/decay_copy.h
   __utility/declval.h
   __utility/exchange.h
   __utility/forward.h

libcxx/include/__ranges/access.h

@@ -13,8 +13,8 @@
 #include <__iterator/concepts.h>
 #include <__iterator/readable_traits.h>
 #include <__ranges/enable_borrowed_range.h>
-#include <__utility/__decay_copy.h>
 #include <__utility/as_const.h>
+#include <__utility/decay_copy.h>
 #include <__utility/forward.h>
 #include <concepts>
 #include <type_traits>

libcxx/include/__ranges/all.h

@@ -17,7 +17,7 @@
 #include <__ranges/range_adaptor.h>
 #include <__ranges/ref_view.h>
 #include <__ranges/subrange.h>
-#include <__utility/__decay_copy.h>
+#include <__utility/decay_copy.h>
 #include <__utility/declval.h>
 #include <__utility/forward.h>
 #include <type_traits>

libcxx/include/__ranges/counted.h

@@ -18,7 +18,7 @@
 #include <__memory/pointer_traits.h>
 #include <__ranges/concepts.h>
 #include <__ranges/subrange.h>
-#include <__utility/__decay_copy.h>
+#include <__utility/decay_copy.h>
 #include <__utility/declval.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>

libcxx/include/__ranges/size.h

@@ -13,7 +13,7 @@
 #include <__iterator/concepts.h>
 #include <__iterator/iterator_traits.h>
 #include <__ranges/access.h>
-#include <__utility/__decay_copy.h>
+#include <__utility/decay_copy.h>
 #include <__utility/forward.h>
 #include <concepts>
 #include <type_traits>

libcxx/include/__utility/decay_copy.h

@@ -7,8 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP___TYPE_TRAITS_DECAY_COPY_H
-#define _LIBCPP___TYPE_TRAITS_DECAY_COPY_H
+#ifndef _LIBCPP___UTILITY_DECAY_COPY_H
+#define _LIBCPP___UTILITY_DECAY_COPY_H
 
 #include <__config>
 #include <__utility/forward.h>
@@ -31,4 +31,4 @@ inline _LIBCPP_INLINE_VISIBILITY typename decay<_Tp>::type __decay_copy(_Tp&& __
 
 _LIBCPP_END_NAMESPACE_STD
 
-#endif // _LIBCPP___TYPE_TRAITS_DECAY_COPY_H
+#endif // _LIBCPP___UTILITY_DECAY_COPY_H

libcxx/include/future

@@ -366,7 +366,7 @@ template <class R, class Alloc> struct uses_allocator<packaged_task<R>, Alloc>;
 #include <__debug>
 #include <__memory/allocator_arg_t.h>
 #include <__memory/uses_allocator.h>
-#include <__utility/__decay_copy.h>
+#include <__utility/decay_copy.h>
 #include <__utility/forward.h>
 #include <chrono>
 #include <exception>

libcxx/include/module.modulemap

@@ -789,9 +789,9 @@ module std [system] {
     export *
 
     module __utility {
-      module __decay_copy        { private header "__utility/__decay_copy.h"        }
       module as_const            { private header "__utility/as_const.h"            }
       module cmp                 { private header "__utility/cmp.h"                 }
+      module decay_copy          { private header "__utility/decay_copy.h"          }
       module declval             { private header "__utility/declval.h"             }
       module exchange            { private header "__utility/exchange.h"            }
       module forward             { private header "__utility/forward.h"             }

libcxx/include/thread

@@ -87,7 +87,7 @@ void sleep_for(const chrono::duration<Rep, Period>& rel_time);
 #include <__functional_base>
 #include <__mutex_base>
 #include <__threading_support>
-#include <__utility/__decay_copy.h>
+#include <__utility/decay_copy.h>
 #include <__utility/forward.h>
 #include <chrono>
 #include <cstddef>

libcxx/test/libcxx/diagnostics/detail.headers/utility/decay_copy.module.verify.cpp

@@ -12,5 +12,5 @@
 // WARNING: This test was generated by 'generate_private_header_tests.py'
 // and should not be edited manually.
 
-// expected-error@*:* {{use of private header from outside its module: '__utility/__decay_copy.h'}}
-#include <__utility/__decay_copy.h>
+// expected-error@*:* {{use of private header from outside its module: '__utility/decay_copy.h'}}
+#include <__utility/decay_copy.h>