[clang-tools-extra] [clang-tidy] Create bugprone-public-enable-shared-from-this check (PR #102299)

[Piotr Zegar via cfe-commits]

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@@ -0,0 +1,26 @@
+.. title:: clang-tidy - bugprone-public-enable-shared-from-this
+
+bugprone-public-enable-shared-from-this
+=======================================
+
+Checks that classes/structs inheriting from ``std::enable_shared_from_this`` derive it with the ``public`` access specifier. If not, then issue a FixItHint that can be applied.
+
+Consider the following code:
+.. code-block:: c++
+        #include <memory>
+
+        class BadExample : std::enable_shared_from_this<BadExample> {
+        // warning: class BadExample is not public even though it's derived from std::enable_shared_from_this [bugprone-public-enable-shared-from-this]
+        // will insert the public keyword if -fix is applied 
+                public:
+                BadExample* foo() { return shared_from_this().get(); }
+                void bar() { return; }
+        };
+
+        void using_not_public() {
+                auto bad_example = std::make_shared<BadExample>();
+                auto* b_ex = bad_example->foo();
+                b_ex->bar();
+        }
+
+When ``using_not_public()`` is called, this code will crash.
----------------
PiotrZSL wrote:

no it won't crash, it will thrown `std::bad_weak_ptr`, if application didin't implement proper exception handling then it would crash.

https://github.com/llvm/llvm-project/pull/102299