[clang-tidy] Deprecate readability-deleted-default check

[njames93]

Summary

... For removal in next release cycle.
The clang warning that does the same thing is enabled by default and typically emits better diagnostics making this check surplus to requirements.

[Eugene.Zelenko]

If Wdefaulted-function-deleted was introduced in 12.0, I think it's safe just to remove readability-deleted-default.

[njames93]

In D97491#2588835, @Eugene.Zelenko wrote:

If Wdefaulted-function-deleted was introduced in 12.0, I think it's safe just to remove readability-deleted-default.

Wdefaulted-function-deleted was introduced in 8.0 and I think it was enabled by default even then. I'm thinking we may be able to squeeze this notice into the 12 branch and then it will be gone by 13

[Eugene.Zelenko]

In D97491#2589097, @njames93 wrote:

In D97491#2588835, @Eugene.Zelenko wrote:

If Wdefaulted-function-deleted was introduced in 12.0, I think it's safe just to remove readability-deleted-default.

Wdefaulted-function-deleted was introduced in 8.0 and I think it was enabled by default even then. I'm thinking we may be able to squeeze this notice into the 12 branch and then it will be gone by 13

Frankly, I don't remember any deprecated check in past. Obsolete checks were just removed and this change was reflected in Release Notes.

[aaron.ballman]

In D97491#2589098, @Eugene.Zelenko wrote:

In D97491#2589097, @njames93 wrote:

In D97491#2588835, @Eugene.Zelenko wrote:

If Wdefaulted-function-deleted was introduced in 12.0, I think it's safe just to remove readability-deleted-default.

Wdefaulted-function-deleted was introduced in 8.0 and I think it was enabled by default even then. I'm thinking we may be able to squeeze this notice into the 12 branch and then it will be gone by 13

Frankly, I don't remember any deprecated check in past. Obsolete checks were just removed and this change was reflected in Release Notes.

With checks that have been released to the public, I think it's good to have a notice that the check was deprecated before we remove it.

LGTM! If we want to squeeze the notice into 12, I think that's also reasonable, but given that this has been around for a while, I'm also fine with a slightly longer deprecation period.

clang-tools-extra/docs/ReleaseNotes.rst

 
 - Improved :doc:`readability-uniqueptr-delete-release
   <clang-tidy/checks/readability-uniqueptr-delete-release>` check.
 
   Added an option to choose whether to refactor by calling the ``reset`` member
   function or assignment to ``nullptr``.
   Added support for pointers to ``std::unique_ptr``.
 
+Deprecated checks
+^^^^^^^^^^^^^^^^^
+
+- The :doc:`readability-deleted-default
+  <clang-tidy/checks/readability-deleted-default>` check has been deprecated.
+  
+  The clang warning `Wdefaulted-function-deleted
+  <https://clang.llvm.org/docs/DiagnosticsReference.html#wdefaulted-function-deleted>`_
+  will diagnose the same issues and is enabled by default.
+
 Improvements to include-fixer
 -----------------------------
 
 The improvements are...
 
 Improvements to clang-include-fixer
 -----------------------------------
 

clang-tools-extra/docs/clang-tidy/checks/readability-deleted-default.rst

 .. title:: clang-tidy - readability-deleted-default
 
 readability-deleted-default
 ===========================
 
-Checks that constructors and assignment operators marked as ``= default`` are
-not actually deleted by the compiler.
-
-.. code-block:: c++
-
-  class Example {
-  public:
-    // This constructor is deleted because I is missing a default value.
-    Example() = default;
-    // This is fine.
-    Example(const Example& Other) = default;
-    // This operator is deleted because I cannot be assigned (it is const).
-    Example& operator=(const Example& Other) = default;
-
-  private:
-    const int I;
-  };
+This check has been deprecated prefer to make use of the `Wdefaulted-function-deleted
+<https://clang.llvm.org/docs/DiagnosticsReference.html#wdefaulted-function-deleted>`_
+flag.