[libcxx] Move the private header __std_stream into the src subdir

[mstorsjo]

Summary

This header isn't used by any public header, so there shouldn't
be any need to install it or treat it as a heder.

Once it's part of the src subdirectory, I guess one could consider
giving it a more traditional name too.

[philnik]

Thanks!

libcxx/include/CMakeLists.txt

set(files
   __ranges/subrange.h
   __ranges/take_view.h
   __ranges/take_while_view.h
   __ranges/transform_view.h
   __ranges/view_interface.h
   __ranges/views.h
   __ranges/zip_view.h
   __split_buffer
-  __std_stream
   __string/char_traits.h
   __string/constexpr_c_functions.h
   __string/extern_template_lists.h
   __support/android/locale_bionic.h
   __support/fuchsia/xlocale.h
   __support/ibm/gettod_zos.h
   __support/ibm/locale_mgmt_zos.h
   __support/ibm/nanosleep.h

libcxx/include/libcxx.imp

 [
   { include: [ "<__hash_table>", "private", "<unordered_map>", "public" ] },
   { include: [ "<__hash_table>", "private", "<unordered_set>", "public" ] },
   { include: [ "<__locale>", "private", "<locale>", "public" ] },
   { include: [ "<__node_handle>", "private", "<map>", "public" ] },
   { include: [ "<__node_handle>", "private", "<set>", "public" ] },
   { include: [ "<__node_handle>", "private", "<unordered_map>", "public" ] },
   { include: [ "<__node_handle>", "private", "<unordered_set>", "public" ] },
   { include: [ "<__split_buffer>", "private", "<deque>", "public" ] },
   { include: [ "<__split_buffer>", "private", "<vector>", "public" ] },
-  { include: [ "<__std_stream>", "private", "<iostream>", "public" ] },
   { include: [ "<__threading_support>", "private", "<atomic>", "public" ] },
   { include: [ "<__threading_support>", "private", "<mutex>", "public" ] },
   { include: [ "<__threading_support>", "private", "<semaphore>", "public" ] },
   { include: [ "<__threading_support>", "private", "<thread>", "public" ] },
   { include: [ "<__tree>", "private", "<map>", "public" ] },
   { include: [ "<__tree>", "private", "<set>", "public" ] },
   { include: [ "@<__algorithm/.*>", "private", "<algorithm>", "public" ] },
   { include: [ "@<__atomic/.*>", "private", "<atomic>", "public" ] },

libcxx/include/module.modulemap.in

   module __hash_table        {         header "__hash_table"        export * }
   module __locale            {
     @requires_LIBCXX_ENABLE_LOCALIZATION@
     private header "__locale" export *
   }
   module __mbstate_t         { private header "__mbstate_t.h"       export * }
   module __node_handle       { private header "__node_handle"       export * }
   module __split_buffer      { private header "__split_buffer"      export * }
-  module __std_stream        {
-    @requires_LIBCXX_ENABLE_LOCALIZATION@
-    private header "__std_stream" export *
-  }
   module __threading_support {         header "__threading_support" export * }
   module __tree              {         header "__tree"              export * }
   module __undef_macros      {         header "__undef_macros"      export * }
   module __verbose_abort     {         header "__verbose_abort"     export * }
 
   module experimental {
     requires cplusplus11
 

libcxx/src/iostream.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include <__locale>
-#include <__std_stream>
+#include "__std_stream"
 #include <new>
 #include <string>
 
 #define _str(s) #s
 #define str(s) _str(s)
 #define _LIBCPP_ABI_NAMESPACE_STR str(_LIBCPP_ABI_NAMESPACE)
 
 _LIBCPP_BEGIN_NAMESPACE_STD

libcxx/test/libcxx/private_headers.verify.cpp

 #include <__ranges/subrange.h> // expected-error@*:* {{use of private header from outside its module: '__ranges/subrange.h'}}
 #include <__ranges/take_view.h> // expected-error@*:* {{use of private header from outside its module: '__ranges/take_view.h'}}
 #include <__ranges/take_while_view.h> // expected-error@*:* {{use of private header from outside its module: '__ranges/take_while_view.h'}}
 #include <__ranges/transform_view.h> // expected-error@*:* {{use of private header from outside its module: '__ranges/transform_view.h'}}
 #include <__ranges/view_interface.h> // expected-error@*:* {{use of private header from outside its module: '__ranges/view_interface.h'}}
 #include <__ranges/views.h> // expected-error@*:* {{use of private header from outside its module: '__ranges/views.h'}}
 #include <__ranges/zip_view.h> // expected-error@*:* {{use of private header from outside its module: '__ranges/zip_view.h'}}
 #include <__split_buffer> // expected-error@*:* {{use of private header from outside its module: '__split_buffer'}}
-#include <__std_stream> // expected-error@*:* {{use of private header from outside its module: '__std_stream'}}
 #include <__string/char_traits.h> // expected-error@*:* {{use of private header from outside its module: '__string/char_traits.h'}}
 #include <__string/constexpr_c_functions.h> // expected-error@*:* {{use of private header from outside its module: '__string/constexpr_c_functions.h'}}
 #include <__string/extern_template_lists.h> // expected-error@*:* {{use of private header from outside its module: '__string/extern_template_lists.h'}}
 #include <__system_error/errc.h> // expected-error@*:* {{use of private header from outside its module: '__system_error/errc.h'}}
 #include <__system_error/error_category.h> // expected-error@*:* {{use of private header from outside its module: '__system_error/error_category.h'}}
 #include <__system_error/error_code.h> // expected-error@*:* {{use of private header from outside its module: '__system_error/error_code.h'}}
 #include <__system_error/error_condition.h> // expected-error@*:* {{use of private header from outside its module: '__system_error/error_condition.h'}}
 #include <__system_error/system_error.h> // expected-error@*:* {{use of private header from outside its module: '__system_error/system_error.h'}}

libcxx/utils/data/ignore_format.txt

 libcxx/include/stack
 libcxx/include/stdatomic.h
 libcxx/include/stdbool.h
 libcxx/include/stddef.h
 libcxx/include/stdexcept
 libcxx/include/stdint.h
 libcxx/include/stdio.h
 libcxx/include/stdlib.h
-libcxx/include/__std_stream
 libcxx/include/streambuf
 libcxx/include/string
 libcxx/include/__string/char_traits.h
 libcxx/include/__string/extern_template_lists.h
 libcxx/include/string.h
 libcxx/include/string_view
 libcxx/include/strstream
 libcxx/include/__support/android/locale_bionic.h

 libcxx/src/mutex_destructor.cpp
 libcxx/src/new.cpp
 libcxx/src/optional.cpp
 libcxx/src/random.cpp
 libcxx/src/random_shuffle.cpp
 libcxx/src/regex.cpp
 libcxx/src/shared_mutex.cpp
 libcxx/src/stdexcept.cpp
+libcxx/src/__std_stream
 libcxx/src/string.cpp
 libcxx/src/strstream.cpp
 libcxx/src/support/ibm/mbsnrtowcs.cpp
 libcxx/src/support/ibm/wcsnrtombs.cpp
 libcxx/src/support/ibm/xlocale_zos.cpp
 libcxx/src/support/runtime/exception_fallback.ipp
 libcxx/src/support/runtime/exception_glibcxx.ipp
 libcxx/src/support/runtime/exception_libcxxabi.ipp

libcxx/utils/generate_iwyu_mapping.py

for i in detail_files:
         elif i == '__debug': continue
         elif i == '__errc': continue
         elif i == '__hash_table': public = ['unordered_map', 'unordered_set']
         elif i == '__locale': public = ['locale']
         elif i == '__mbstate_t.h': continue
         elif i == '__mutex_base': continue
         elif i == '__node_handle': public = ['map', 'set', 'unordered_map', 'unordered_set']
         elif i == '__split_buffer': public = ['deque', 'vector']
-        elif i == '__std_stream': public = ['iostream']
         elif i == '__threading_support': public = ['atomic', 'mutex', 'semaphore', 'thread']
         elif i == '__tree': public = ['map', 'set']
         elif i == '__undef_macros': continue
         elif i == '__verbose_abort': continue
         else: panic()
 
         for p in public:
             result.append(f'{generate(f"<{i}>", p)},')