Merge #17134: doc: Add switch on enum example to developer notes

c8961c7d9f doc: Add switch on enum example (Hennadii Stepanov)
11e3d5eb1d util: Add AllowShortCaseLabelsOnASingleLine option (Hennadii Stepanov)

Pull request description:

  This PR documents a recurring issue:
  - #15938
  - #17105

ACKs for top commit:
  laanwj:
    Seems like good advice to me. ACK c8961c7d9f
  practicalswift:
    ACK c8961c7d9f
  promag:
    ACK c8961c7d9f, no excuse now, thanks!

Tree-SHA512: 530da5117094ed1bfaa6e447089521bd2c86b0742758dbacec4e4f934dc07b0e24f15a1448c4d58e49905e8fd3797d87bcae5669a346d33ed4c2878a04891699

doc/developer-notes.md

@@ -87,7 +87,6 @@ code.
   - `++i` is preferred over `i++`.
   - `nullptr` is preferred over `NULL` or `(void*)0`.
   - `static_assert` is preferred over `assert` where possible. Generally; compile-time checking is preferred over run-time checking.
-  - `enum class` is preferred over `enum` where possible. Scoped enumerations avoid two potential pitfalls/problems with traditional C++ enumerations: implicit conversions to int, and name clashes due to enumerators being exported to the surrounding scope.
 
 Block style example:
 ```c++
@@ -563,6 +562,34 @@ class A
   - *Rationale*: Easier to understand what is happening, thus easier to spot mistakes, even for those
   that are not language lawyers.
 
+- Prefer `enum class` (scoped enumerations) over `enum` (traditional enumerations) where possible.
+
+  - *Rationale*: Scoped enumerations avoid two potential pitfalls/problems with traditional C++ enumerations: implicit conversions to `int`, and name clashes due to enumerators being exported to the surrounding scope.
+
+- `switch` statement on an enumeration example:
+
+```cpp
+enum class Tabs {
+    INFO,
+    CONSOLE,
+    GRAPH,
+    PEERS
+};
+
+int GetInt(Tabs tab)
+{
+    switch (tab) {
+    case Tabs::INFO: return 0;
+    case Tabs::CONSOLE: return 1;
+    case Tabs::GRAPH: return 2;
+    case Tabs::PEERS: return 3;
+    } // no default case, so the compiler can warn about missing cases
+    assert(false);
+}
+```
+
+*Rationale*: The comment documents skipping `default:` label, and it complies with `clang-format` rules. The assertion prevents firing of `-Wreturn-type` warning on some compilers.
+
 Strings and formatting
 ------------------------
 

src/.clang-format

@@ -5,6 +5,7 @@ AlignEscapedNewlinesLeft: true
 AlignTrailingComments: true
 AllowAllParametersOfDeclarationOnNextLine: false
 AllowShortBlocksOnASingleLine: false
+AllowShortCaseLabelsOnASingleLine: true
 AllowShortFunctionsOnASingleLine: All
 AllowShortIfStatementsOnASingleLine: true
 AllowShortLoopsOnASingleLine: false