C#: Change note & docs.

Author: calumgrant

change-notes/1.23/analysis-csharp.md

@@ -37,5 +37,6 @@ The following changes in version 1.23 affect C# analysis in all applications.
   disabled by default and can be enabled for individual configurations by
   overriding `int explorationLimit()`.
 * `foreach` statements where the body is guaranteed to be executed at least once, such as `foreach (var x in new string[]{ "a", "b", "c" }) { ... }`, are now recognized by all analyses based on the control flow graph (such as SSA, data flow and taint tracking).
+* Fixed the control flow graph for `switch` statements where the `default` case was not the last case. This had caused the remaining cases to be unreachable. `SwitchStmt.getCase(int i)` now puts the `default` case last.
 
 ## Changes to autobuilder

csharp/ql/src/semmle/code/csharp/Stmt.qll

@@ -165,6 +165,7 @@ class SwitchStmt extends SelectionStmt, Switch, @switch_stmt {
    *     return 3;
    * }
    * ```
+   * Note that this reorders the `default` case to always be at the end.
    */
   override CaseStmt getCase(int i) { result = SwithStmtInternal::getCase(this, i) }