Style, code updates

Colin Robertson · web-flow · commit 8dbe7567d994 · 2020-08-21T18:31:35.000-07:00
Update date, add description.
Acrolinx fixes.
Replace sample with one that demonstrates C26434 instead of C26435
diff --git a/docs/code-quality/c26434.md b/docs/code-quality/c26434.md
@@ -1,45 +1,49 @@
 ---
 title: C26434
-ms.date: 11/15/2017
+description: "Microsoft C++ Code Analysis warning C26434 for the C++ Core Guidelines case C.128."
+ms.date: 08/21/2020
 ms.topic: "conceptual"
 f1_keywords: ["C26434"]
 helpviewer_keywords: ["C26434"]
 ms.assetid: 7f66477f-da66-444a-a6e3-44513d7d7e31
 ---
 # C26434 DONT_HIDE_METHODS
 
-"Function hides a non-virtual function."
+> `Function 'derived::function' hides a non-virtual function 'base::function' (c.128).`
 
 ## C++ Core Guidelines
 
 [C.128: Virtual functions should specify exactly one of virtual, override, or final](https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md)
 
-Introducing a function which has the same name as a non-virtual function in a base class is like introducing a variable name which conflicts with a name from outer scope. Furthermore, if signatures of functions mismatch, the intended overriding may turn into overloading. Overall, name hiding is dangerous and error-prone.
-
 ## Remarks
 
-- Only non-overriding functions in current class are checked.
+When you introduce a function that has the same name as a non-virtual function in a base class, you may get unexpected behavior. It's like introducing a variable name which conflicts with a name from an outer scope. For example, you may have intended to override a base class function. If the signatures of the functions don't match, the override you intended may turn into an overload instead. In general, name hiding is dangerous and error-prone.
+
+In the Core Guidelines checks:
+
+- Only non-overriding functions in the current class are checked.
 - Only non-virtual functions of base classes are considered.
 - No signature matching is performed. Warnings are emitted if unqualified names match.
 
-## See also
+## Example
 
-[C.128: Virtual functions should specify exactly one of virtual, override, or final](https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md)
+This example demonstrates good engineering practice for explicit **`override`** and **`virtual`** use:
 
-# Example
-```
+```cpp
+// C26434.cpp
 struct Base
 {
-    virtual void foo() = 0;
+    virtual ~Base() = default;
+    virtual void is_virtual() noexcept {}
+    void not_virtual() noexcept {}
 };
 
-struct Derived_1 : Base
+struct Derived : Base
 {
-    virtual void foo() override {} // C26434, virtual is not needed here.
+    void is_virtual() noexcept override {}      // Okay, override existing function
+    virtual void is_virtual(int i) noexcept {}  // Add a virtual overload for function
+    void not_virtual() noexcept {}              // C26434, hides a non-virtual function
+    virtual void not_virtual(int i) noexcept {} // C26434, and parameters ignored
 };
 
-struct Derived_2 : Base
-{
-    void foo() override {}
-};
 ```
