[clang-tools-extra] [clang-tidy] Add detection of decltype(nullptr) => std::nullptr_t to modernize-use-nullptr (PR #224591)

[via cfe-commits]

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@@ -229,6 +224,10 @@ infrastructure are described first, followed by tool-specific sections.
   <clang-tidy/checks/modernize/use-noexcept>` when analyzing malformed template
   code with an unparsed exception specification.
 
+- Extend {doc}`modernize-use-nullptr
+  <clang-tidy/checks/modernize/use-nullptr>` to turn ``decltype(nullptr)`` into
+  ``std::nullptr_t`` from ``<cstdef>``.
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serge-sans-paille wrote:

ack

https://github.com/llvm/llvm-project/pull/224591