cxxmodules: remove support for `CXX_MODULE_HEADER_UNITS` filesets

There's no backing implementation for header units anyways, so just
remove it for now.

10 files changed, 8 insertions, 154 deletions

diff --git a/Help/command/target_sources.rst b/Help/command/target_sources.rst
index 5d07f54..4a8eda2 100644
--- a/Help/command/target_sources.rst
+++ b/Help/command/target_sources.rst
@@ -91,15 +91,6 @@ files within those directories. The acceptable types include:
   using the ``export`` keyword). This file set type may not have an
   ``INTERFACE`` scope except on ``IMPORTED`` targets.
 
-``CXX_MODULE_HEADER_UNITS``
-
-  .. note ::
-
-    Experimental. Gated by ``CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API``
-
-  C++ header sources which may be imported by other C++ source code. This file
-  set type may not have an ``INTERFACE`` scope except on ``IMPORTED`` targets.
-
 The optional default file sets are named after their type. The target may not
 be a custom target or :prop_tgt:`FRAMEWORK` target.
 
@@ -177,31 +168,20 @@ For file sets of type ``CXX_MODULES``:
 * :prop_tgt:`CXX_MODULE_DIRS`
 * :prop_tgt:`CXX_MODULE_DIRS_<NAME>`
 
-For file sets of type ``CXX_MODULE_HEADER_UNITS``:
-
-* :prop_tgt:`CXX_MODULE_HEADER_UNIT_SETS`
-* :prop_tgt:`INTERFACE_CXX_MODULE_HEADER_UNIT_SETS`
-* :prop_tgt:`CXX_MODULE_HEADER_UNIT_SET`
-* :prop_tgt:`CXX_MODULE_HEADER_UNIT_SET_<NAME>`
-* :prop_tgt:`CXX_MODULE_HEADER_UNIT_DIRS`
-* :prop_tgt:`CXX_MODULE_HEADER_UNIT_DIRS_<NAME>`
-
 Target properties related to include directories are also modified by
 ``target_sources(FILE_SET)`` as follows:
 
 :prop_tgt:`INCLUDE_DIRECTORIES`
 
-  If the ``TYPE`` is ``HEADERS`` or ``CXX_MODULE_HEADER_UNITS``, and the scope
-  of the file set is ``PRIVATE`` or ``PUBLIC``, all of the ``BASE_DIRS`` of
-  the file set are wrapped in :genex:`$<BUILD_INTERFACE>` and appended to this
-  property.
+  If the ``TYPE`` is ``HEADERS``, and the scope of the file set is ``PRIVATE``
+  or ``PUBLIC``, all of the ``BASE_DIRS`` of the file set are wrapped in
+  :genex:`$<BUILD_INTERFACE>` and appended to this property.
 
 :prop_tgt:`INTERFACE_INCLUDE_DIRECTORIES`
 
-  If the ``TYPE`` is ``HEADERS`` or ``CXX_MODULE_HEADER_UNITS``, and the scope
-  of the file set is ``INTERFACE`` or ``PUBLIC``, all of the ``BASE_DIRS`` of
-  the file set are wrapped in :genex:`$<BUILD_INTERFACE>` and appended to this
-  property.
+  If the ``TYPE`` is ``HEADERS``, and the scope of the file set is
+  ``INTERFACE`` or ``PUBLIC``, all of the ``BASE_DIRS`` of the file set are
+  wrapped in :genex:`$<BUILD_INTERFACE>` and appended to this property.
 
 See Also
 ^^^^^^^^
diff --git a/Help/manual/cmake-properties.7.rst b/Help/manual/cmake-properties.7.rst
index b2a27a0..e17d472 100644
--- a/Help/manual/cmake-properties.7.rst
+++ b/Help/manual/cmake-properties.7.rst
@@ -189,11 +189,6 @@ Properties on Targets
    /prop_tgt/CXX_EXTENSIONS
    /prop_tgt/CXX_MODULE_DIRS
    /prop_tgt/CXX_MODULE_DIRS_NAME
-   /prop_tgt/CXX_MODULE_HEADER_UNIT_DIRS
-   /prop_tgt/CXX_MODULE_HEADER_UNIT_DIRS_NAME
-   /prop_tgt/CXX_MODULE_HEADER_UNIT_SET
-   /prop_tgt/CXX_MODULE_HEADER_UNIT_SET_NAME
-   /prop_tgt/CXX_MODULE_HEADER_UNIT_SETS
    /prop_tgt/CXX_MODULE_SET
    /prop_tgt/CXX_MODULE_SET_NAME
    /prop_tgt/CXX_MODULE_SETS
@@ -279,7 +274,6 @@ Properties on Targets
    /prop_tgt/INTERFACE_COMPILE_DEFINITIONS
    /prop_tgt/INTERFACE_COMPILE_FEATURES
    /prop_tgt/INTERFACE_COMPILE_OPTIONS
-   /prop_tgt/INTERFACE_CXX_MODULE_HEADER_UNIT_SETS
    /prop_tgt/INTERFACE_CXX_MODULE_SETS
    /prop_tgt/INTERFACE_HEADER_SETS
    /prop_tgt/INTERFACE_HEADER_SETS_TO_VERIFY
diff --git a/Help/prop_sf/CXX_SCAN_FOR_MODULES.rst b/Help/prop_sf/CXX_SCAN_FOR_MODULES.rst
index 23c4859..5b704dc 100644
--- a/Help/prop_sf/CXX_SCAN_FOR_MODULES.rst
+++ b/Help/prop_sf/CXX_SCAN_FOR_MODULES.rst
@@ -15,8 +15,7 @@ consulted.
 
 Note that scanning is only performed if C++20 or higher is enabled for the
 target and the source uses the ``CXX`` language.  Scanning for modules in
-sources belonging to file sets of type ``CXX_MODULES`` and
-``CXX_MODULES_HEADER_UNITS`` is always performed.
+sources belonging to file sets of type ``CXX_MODULES`` is always performed.
 
 .. note ::
 
diff --git a/Help/prop_tgt/CXX_MODULE_HEADER_UNIT_DIRS.rst b/Help/prop_tgt/CXX_MODULE_HEADER_UNIT_DIRS.rst
deleted file mode 100644
index 5f33111..0000000
--- a/Help/prop_tgt/CXX_MODULE_HEADER_UNIT_DIRS.rst
+++ /dev/null
@@ -1,19 +0,0 @@
-CXX_MODULE_HEADER_UNIT_DIRS
----------------------------
-
-.. versionadded:: 3.25
-
-.. note ::
-
-  Experimental. Gated by ``CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API``
-
-Semicolon-separated list of base directories of the target's default C++
-module header set (i.e. the file set with name and type
-``CXX_MODULE_HEADER_UNITS``). The property supports
-:manual:`generator expressions <cmake-generator-expressions(7)>`.
-
-This property is normally only set by :command:`target_sources(FILE_SET)`
-rather than being manipulated directly.
-
-See :prop_tgt:`CXX_MODULE_HEADER_UNIT_DIRS_<NAME>` for the list of base
-directories in other C++ module header sets.
diff --git a/Help/prop_tgt/CXX_MODULE_HEADER_UNIT_DIRS_NAME.rst b/Help/prop_tgt/CXX_MODULE_HEADER_UNIT_DIRS_NAME.rst
deleted file mode 100644
index b6163da..0000000
--- a/Help/prop_tgt/CXX_MODULE_HEADER_UNIT_DIRS_NAME.rst
+++ /dev/null
@@ -1,21 +0,0 @@
-CXX_MODULE_HEADER_UNIT_DIRS_<NAME>
-----------------------------------
-
-.. versionadded:: 3.25
-
-.. note ::
-
-  Experimental. Gated by ``CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API``
-
-Semicolon-separated list of base directories of the target's ``<NAME>`` C++
-module header set, which has the set type ``CXX_MODULE_HEADER_UNITS``. The
-property supports
-:manual:`generator expressions <cmake-generator-expressions(7)>`.
-
-This property is normally only set by :command:`target_sources(FILE_SET)`
-rather than being manipulated directly.
-
-See :prop_tgt:`CXX_MODULE_HEADER_UNIT_DIRS` for the list of base directories
-in the default C++ module header set. See
-:prop_tgt:`CXX_MODULE_HEADER_UNIT_SETS` for the file set names of all C++
-module header sets.
diff --git a/Help/prop_tgt/CXX_MODULE_HEADER_UNIT_SET.rst b/Help/prop_tgt/CXX_MODULE_HEADER_UNIT_SET.rst
deleted file mode 100644
index 3b1bd04..0000000
--- a/Help/prop_tgt/CXX_MODULE_HEADER_UNIT_SET.rst
+++ /dev/null
@@ -1,20 +0,0 @@
-CXX_MODULE_HEADER_UNIT_SET
---------------------------
-
-.. versionadded:: 3.25
-
-.. note ::
-
-  Experimental. Gated by ``CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API``
-
-Semicolon-separated list of files in the target's default C++ module header
-set, (i.e. the file set with name and type ``CXX_MODULE_HEADER_UNITS``). If
-any of the paths are relative, they are computed relative to the target's
-source directory. The property supports
-:manual:`generator expressions <cmake-generator-expressions(7)>`.
-
-This property is normally only set by :command:`target_sources(FILE_SET)`
-rather than being manipulated directly.
-
-See :prop_tgt:`CXX_MODULE_HEADER_UNIT_SET_<NAME>` for the list of files in
-other C++ module header sets.
diff --git a/Help/prop_tgt/CXX_MODULE_HEADER_UNIT_SETS.rst b/Help/prop_tgt/CXX_MODULE_HEADER_UNIT_SETS.rst
deleted file mode 100644
index ffc2daf..0000000
--- a/Help/prop_tgt/CXX_MODULE_HEADER_UNIT_SETS.rst
+++ /dev/null
@@ -1,20 +0,0 @@
-CXX_MODULE_HEADER_UNIT_SETS
----------------------------
-
-.. versionadded:: 3.25
-
-.. note ::
-
-  Experimental. Gated by ``CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API``
-
-Read-only list of the target's ``PRIVATE`` and ``PUBLIC`` C++ module header
-sets (i.e. all file sets with the type ``CXX_MODULE_HEADER_UNITS``). Files
-listed in these file sets are treated as source files for the purpose of IDE
-integration.
-
-C++ module header sets may be defined using the :command:`target_sources`
-command ``FILE_SET`` option with type ``CXX_MODULE_HEADER_UNITS``.
-
-See also :prop_tgt:`CXX_MODULE_HEADER_UNIT_SET_<NAME>`,
-:prop_tgt:`CXX_MODULE_HEADER_UNIT_SET` and
-:prop_tgt:`INTERFACE_CXX_MODULE_HEADER_UNIT_SETS`.
diff --git a/Help/prop_tgt/CXX_MODULE_HEADER_UNIT_SET_NAME.rst b/Help/prop_tgt/CXX_MODULE_HEADER_UNIT_SET_NAME.rst
deleted file mode 100644
index 4bf5069..0000000
--- a/Help/prop_tgt/CXX_MODULE_HEADER_UNIT_SET_NAME.rst
+++ /dev/null
@@ -1,21 +0,0 @@
-CXX_MODULE_HEADER_UNIT_SET_<NAME>
----------------------------------
-
-.. versionadded:: 3.25
-
-.. note ::
-
-  Experimental. Gated by ``CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API``
-
-Semicolon-separated list of files in the target's ``<NAME>`` C++ module header
-set, which has the set type ``CXX_MODULE_HEADER_UNITS``. If any of the paths
-are relative, they are computed relative to the target's source directory. The
-property supports
-:manual:`generator expressions <cmake-generator-expressions(7)>`.
-
-This property is normally only set by :command:`target_sources(FILE_SET)`
-rather than being manipulated directly.
-
-See :prop_tgt:`CXX_MODULE_HEADER_UNIT_SET` for the list of files in the
-default C++ module header set. See :prop_tgt:`CXX_MODULE_HEADER_UNIT_SETS` for
-the file set names of all C++ module header sets.
diff --git a/Help/prop_tgt/CXX_SCAN_FOR_MODULES.rst b/Help/prop_tgt/CXX_SCAN_FOR_MODULES.rst
index e2127c2..93a1b73 100644
--- a/Help/prop_tgt/CXX_SCAN_FOR_MODULES.rst
+++ b/Help/prop_tgt/CXX_SCAN_FOR_MODULES.rst
@@ -19,7 +19,7 @@ scan the target's ``CXX`` sources at build time.
 
 Note that scanning is only performed if C++20 or higher is enabled for the
 target.  Scanning for modules in the target's sources belonging to file sets
-of type ``CXX_MODULES`` and ``CXX_MODULES_HEADER_UNITS`` is always performed.
+of type ``CXX_MODULES`` is always performed.
 
 .. note ::
 
diff --git a/Help/prop_tgt/INTERFACE_CXX_MODULE_HEADER_UNIT_SETS.rst b/Help/prop_tgt/INTERFACE_CXX_MODULE_HEADER_UNIT_SETS.rst
deleted file mode 100644
index 3fe6d9a..0000000
--- a/Help/prop_tgt/INTERFACE_CXX_MODULE_HEADER_UNIT_SETS.rst
+++ /dev/null
@@ -1,18 +0,0 @@
-INTERFACE_CXX_MODULE_HEADER_UNIT_SETS
--------------------------------------
-
-.. versionadded:: 3.25
-
-.. note ::
-
-  Experimental. Gated by ``CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API``
-
-Read-only list of the target's ``PUBLIC`` C++ module header sets (i.e. all
-file sets with the type ``CXX_MODULE_HEADER_UNITS``). Files listed in these
-C++ module header sets can be installed with :command:`install(TARGETS)` and
-exported with :command:`install(EXPORT)` and :command:`export`.
-
-C++ module header sets may be defined using the :command:`target_sources`
-command ``FILE_SET`` option with type ``CXX_MODULE_HEADER_UNITS``.
-
-See also :prop_tgt:`CXX_MODULE_HEADER_UNIT_SETS`.