Fix VoidType handling

Author: tamasvajk

csharp/ql/src/Stubs/Stubs.qll

@@ -13,6 +13,7 @@
 
 import csharp
 private import semmle.code.csharp.frameworks.System
+private import semmle.code.dotnet.DotNet as DotNet // added to handle VoidType as a ValueOrRefType
 
 /** An element that should be in the generated code. */
 abstract class GeneratedElement extends Element { }
@@ -332,7 +333,7 @@ private class GeneratedNamespace extends Namespace, GeneratedElement {
   }
 
   private predicate isInAssembly(Assembly assembly) {
-    any(GeneratedType gt | gt.(ValueOrRefType).getDeclaringNamespace() = this)
+    any(GeneratedType gt | gt.(DotNet::ValueOrRefType).getDeclaringNamespace() = this)
         .isInAssembly(assembly)
     or
     this.getChildNamespace(_).isInAssembly(assembly)
@@ -353,7 +354,7 @@ private class GeneratedNamespace extends Namespace, GeneratedElement {
     this.isInAssembly(assembly) and
     result =
       concat(GeneratedType gt |
-        gt.(ValueOrRefType).getDeclaringNamespace() = this and gt.isInAssembly(assembly)
+        gt.(DotNet::ValueOrRefType).getDeclaringNamespace() = this and gt.isInAssembly(assembly)
       |
         gt.getStub(assembly) order by gt.getName()
       )