[libc++] Moves unwrap_reference to type_traits.

This was discovered while working on modules.

Reviewed By: #libc, philnik

Differential Revision: https://reviews.llvm.org/D149351

Author: mordante

libcxx/include/CMakeLists.txt

@@ -395,7 +395,6 @@ set(files
   __functional/reference_wrapper.h
   __functional/unary_function.h
   __functional/unary_negate.h
-  __functional/unwrap_ref.h
   __functional/weak_result_type.h
   __fwd/array.h
   __fwd/fstream.h
@@ -792,6 +791,7 @@ set(files
   __type_traits/type_identity.h
   __type_traits/type_list.h
   __type_traits/underlying_type.h
+  __type_traits/unwrap_ref.h
   __type_traits/void_t.h
   __undef_macros
   __utility/as_const.h

libcxx/include/__functional/unwrap_ref.h renamed to libcxx/include/__type_traits/unwrap_ref.h

@@ -6,8 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP___FUNCTIONAL_UNWRAP_REF_H
-#define _LIBCPP___FUNCTIONAL_UNWRAP_REF_H
+#ifndef _LIBCPP___TYPE_TRAITS_UNWRAP_REF_H
+#define _LIBCPP___TYPE_TRAITS_UNWRAP_REF_H
 
 #include <__config>
 #include <__type_traits/decay.h>
@@ -42,7 +42,7 @@ struct unwrap_ref_decay : unwrap_reference<__decay_t<_Tp> > { };
 
 template <class _Tp>
 using unwrap_ref_decay_t = typename unwrap_ref_decay<_Tp>::type;
-#endif // > C++17
+#endif // _LIBCPP_STD_VER >= 20
 
 template <class _Tp>
 struct __unwrap_ref_decay
@@ -55,4 +55,4 @@ struct __unwrap_ref_decay
 
 _LIBCPP_END_NAMESPACE_STD
 
-#endif // _LIBCPP___FUNCTIONAL_UNWRAP_REF_H
+#endif // _LIBCPP___TYPE_TRAITS_UNWRAP_REF_H

libcxx/include/__utility/pair.h

@@ -13,7 +13,6 @@
 #include <__compare/synth_three_way.h>
 #include <__concepts/different_from.h>
 #include <__config>
-#include <__functional/unwrap_ref.h>
 #include <__fwd/array.h>
 #include <__fwd/get.h>
 #include <__fwd/subrange.h>
@@ -45,6 +44,7 @@
 #include <__type_traits/is_swappable.h>
 #include <__type_traits/nat.h>
 #include <__type_traits/remove_cvref.h>
+#include <__type_traits/unwrap_ref.h>
 #include <__utility/declval.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>

libcxx/include/functional

@@ -541,7 +541,7 @@ POLICY:  For non-variadic implementations, the number of arguments is limited
 #include <__functional/reference_wrapper.h>
 #include <__functional/unary_function.h>
 #include <__functional/unary_negate.h>
-#include <__functional/unwrap_ref.h>
+#include <__type_traits/unwrap_ref.h>
 #include <__utility/forward.h>
 #include <memory> // TODO: find out why removing this breaks the modules build
 #include <typeinfo>

libcxx/include/module.modulemap.in

@@ -977,6 +977,8 @@ module std [system] {
   }
   module functional {
     header "functional"
+    // the contents of __type_traits/unwrap_ref.h should be available from functional too.
+    export type_traits.unwrap_ref
     export *
 
     module __functional {
@@ -1010,7 +1012,6 @@ module std [system] {
       module reference_wrapper          { private header "__functional/reference_wrapper.h" }
       module unary_function             { private header "__functional/unary_function.h" }
       module unary_negate               { private header "__functional/unary_negate.h" }
-      module unwrap_ref                 { private header "__functional/unwrap_ref.h" }
       module weak_result_type           { private header "__functional/weak_result_type.h" }
     }
   }
@@ -1521,7 +1522,6 @@ module std [system] {
   }
   module type_traits {
     header "type_traits"
-    export functional.__functional.unwrap_ref
     export *
 
     module add_const                                 { private header "__type_traits/add_const.h" }
@@ -1682,6 +1682,7 @@ module std [system] {
 
       export type_traits
     }
+    module unwrap_ref                                { private header "__type_traits/unwrap_ref.h" }
     module void_t                                    { private header "__type_traits/void_t.h" }
   }
   module typeindex {

libcxx/include/tuple

@@ -206,7 +206,6 @@ template <class... Types>
 #include <__compare/synth_three_way.h>
 #include <__config>
 #include <__functional/invoke.h>
-#include <__functional/unwrap_ref.h>
 #include <__fwd/array.h>
 #include <__fwd/tuple.h>
 #include <__memory/allocator_arg_t.h>
@@ -252,6 +251,7 @@ template <class... Types>
 #include <__type_traits/negation.h>
 #include <__type_traits/remove_cvref.h>
 #include <__type_traits/remove_reference.h>
+#include <__type_traits/unwrap_ref.h>
 #include <__utility/forward.h>
 #include <__utility/integer_sequence.h>
 #include <__utility/move.h>

libcxx/include/type_traits

@@ -532,6 +532,7 @@ namespace std
 #include <__type_traits/result_of.h>
 #include <__type_traits/type_identity.h>
 #include <__type_traits/underlying_type.h>
+#include <__type_traits/unwrap_ref.h>
 #include <__type_traits/void_t.h>
 #include <__utility/declval.h>
 #include <cstddef>

libcxx/test/libcxx/private_headers.verify.cpp

@@ -431,7 +431,6 @@ END-SCRIPT
 #include <__functional/reference_wrapper.h> // expected-error@*:* {{use of private header from outside its module: '__functional/reference_wrapper.h'}}
 #include <__functional/unary_function.h> // expected-error@*:* {{use of private header from outside its module: '__functional/unary_function.h'}}
 #include <__functional/unary_negate.h> // expected-error@*:* {{use of private header from outside its module: '__functional/unary_negate.h'}}
-#include <__functional/unwrap_ref.h> // expected-error@*:* {{use of private header from outside its module: '__functional/unwrap_ref.h'}}
 #include <__functional/weak_result_type.h> // expected-error@*:* {{use of private header from outside its module: '__functional/weak_result_type.h'}}
 #include <__fwd/array.h> // expected-error@*:* {{use of private header from outside its module: '__fwd/array.h'}}
 #include <__fwd/fstream.h> // expected-error@*:* {{use of private header from outside its module: '__fwd/fstream.h'}}
@@ -776,6 +775,7 @@ END-SCRIPT
 #include <__type_traits/type_identity.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/type_identity.h'}}
 #include <__type_traits/type_list.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/type_list.h'}}
 #include <__type_traits/underlying_type.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/underlying_type.h'}}
+#include <__type_traits/unwrap_ref.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/unwrap_ref.h'}}
 #include <__type_traits/void_t.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/void_t.h'}}
 #include <__utility/as_const.h> // expected-error@*:* {{use of private header from outside its module: '__utility/as_const.h'}}
 #include <__utility/auto_cast.h> // expected-error@*:* {{use of private header from outside its module: '__utility/auto_cast.h'}}

libcxx/utils/data/ignore_format.txt

@@ -394,7 +394,6 @@ libcxx/include/__functional/ranges_operations.h
 libcxx/include/__functional/reference_wrapper.h
 libcxx/include/__functional/unary_function.h
 libcxx/include/__functional/unary_negate.h
-libcxx/include/__functional/unwrap_ref.h
 libcxx/include/__functional/weak_result_type.h
 libcxx/include/future
 libcxx/include/__fwd/get.h
@@ -757,6 +756,7 @@ libcxx/include/__type_traits/strip_signature.h
 libcxx/include/__type_traits/type_identity.h
 libcxx/include/__type_traits/type_list.h
 libcxx/include/__type_traits/underlying_type.h
+libcxx/include/__type_traits/unwrap_ref.h
 libcxx/include/__type_traits/void_t.h
 libcxx/include/uchar.h
 libcxx/include/unordered_map