Merge commit '45307f1b0d27' from llvm.org/main into next

Author: git apple-llvm automerger

libcxx/docs/Contributing.rst

@@ -48,7 +48,7 @@ sure you don't forget anything:
 
   - Did you add it to ``include/module.modulemap.in``?
   - Did you add it to ``include/CMakeLists.txt``?
-  - If it's a public header, did you update ``utils/generate_header_inclusion_tests.py``?
+  - If it's a public header, did you update ``utils/libcxx/test/header_information.py``?
 
 - Did you add the relevant feature test macro(s) for your feature? Did you update the ``generate_feature_test_macro_components.py`` script with it?
 - Did you run the ``libcxx-generate-files`` target and verify its output?

libcxx/test/libcxx/header_inclusions.gen.py

@@ -0,0 +1,47 @@
+#===----------------------------------------------------------------------===##
+#
+# 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
+#
+#===----------------------------------------------------------------------===##
+
+# Test that all headers include all the other headers they're supposed to, as
+# prescribed by the Standard.
+
+# RUN: %{python} %s %{libcxx}/utils
+
+import sys
+sys.path.append(sys.argv[1])
+from libcxx.test.header_information import header_restrictions, public_headers, mandatory_inclusions
+
+for header in public_headers:
+  test_condition_begin = '#if ' + header_restrictions[header] if header in header_restrictions else ''
+  test_condition_end = '#endif' if header in header_restrictions else ''
+
+  header_guard = lambda h: f"_LIBCPP_{h.upper().replace('.', '_').replace('/', '_')}"
+
+  # <cassert> has no header guards
+  if header == 'cassert':
+    checks = ''
+  else:
+    checks = f'''
+#ifndef {header_guard(header)}
+# error <{header}> was expected to define a header guard {header_guard(header)}
+#endif
+'''
+  for includee in mandatory_inclusions.get(header, []):
+    checks += f'''
+#ifndef {header_guard(includee)}
+# error <{header}> was expected to include <{includee}>
+#endif
+'''
+
+  print(f"""\
+//--- {header}.compile.pass.cpp
+#include <__config>
+{test_condition_begin}
+#include <{header}>
+{checks}
+{test_condition_end}
+""")