C#: Add test case for local disposal.

Author: calumgrant

csharp/ql/test/query-tests/API Abuse/NoDisposeCallOnLocalIDisposable/NoDisposeCallOnLocalIDisposable.cs

@@ -83,6 +83,11 @@ public IDisposable Method()
         // GOOD: Disposed automatically.
         using var c2 = new Timer(TimerProc);
 
+        // GOOD: ownership taken via ?? (false positive)
+        StringReader source = null;
+        using(XmlReader.Create(source ?? new StringReader("xml"), null))
+            ;
+
         return null;
     }
 

csharp/ql/test/query-tests/API Abuse/NoDisposeCallOnLocalIDisposable/NoDisposeCallOnLocalIDisposable.expected

@@ -2,4 +2,5 @@
 | NoDisposeCallOnLocalIDisposable.cs:53:18:53:73 | object creation of type FileStream | Disposable 'FileStream' is created here but is not disposed. |
 | NoDisposeCallOnLocalIDisposable.cs:54:9:54:64 | object creation of type FileStream | Disposable 'FileStream' is created here but is not disposed. |
 | NoDisposeCallOnLocalIDisposable.cs:76:25:76:71 | call to method Create | Disposable 'XmlReader' is created here but is not disposed. |
+| NoDisposeCallOnLocalIDisposable.cs:88:42:88:64 | object creation of type StringReader | Disposable 'StringReader' is created here but is not disposed. |
 | NoDisposeCallOnLocalIDisposableBad.cs:8:22:8:56 | object creation of type FileStream | Disposable 'FileStream' is created here but is not disposed. |