[clang-tools-extra] [clang-tidy] Added check 'bugprone-function-visibility-change' (PR #140086)

[Piotr Zegar via cfe-commits]

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@@ -0,0 +1,43 @@
+.. title:: clang-tidy - bugprone-function-visibility-change
+
+bugprone-function-visibility-change
+===================================
+
+Check changes in visibility of C++ member functions in subclasses. The check
+detects if a virtual function is overridden with a different visibility than in
+the base class declaration. Only normal functions are detected, no constructors,
+operators, conversions or other special functions.
+
+.. code-block:: c++
+
+  class A {
+  public:
+    virtual void f_pub();
+  private:
+    virtual void f_priv();
+  };
+  
+  class B: public A {
+  public:
+    void f_priv(); // warning: changed visibility from private to public
+  private:
+    void f_pub(); // warning: changed visibility from public to private
+  };
+
+  class C: private A {
+    // no warning: f_pub becomes private in this case but this is from the
+    // private inheritance
+  };
+
+  class D: private A {
+  public:
+    void f_pub(); // warning: changed visibility from private to public
+                  // 'f_pub' would have private access but is forced to be
+                  // public
+  };
+
+The changed visibility can be an indicator of bad design or a result of
+coding error or code changes. If it is intentional, it can be avoided by
+adding an additional virtual function with the new access.
----------------
PiotrZSL wrote:

Proxy functions are out of date, in current days "using declaration" can be used for that.

https://github.com/llvm/llvm-project/pull/140086