Add Transitive casting and testing code

Author: BenFordTytherington

crates/cxx-qt-gen/src/generator/rust/fragment.rs

@@ -83,11 +83,18 @@ impl GeneratedRustFragment {
                         #upcast_fn_qualified(this)
                     }
 
-                    unsafe fn from_base_ptr(base: *const #base_qualified) -> *const Self {
-                        #downcast_fn_qualified(base)
+                        unsafe fn from_base_ptr(base: *const #base_qualified) -> *const Self {
+                            #downcast_fn_qualified(base)
+                        }
                     }
-                }
-            }],
+                },
+                // Add back once we figure out the bug with QObject, for automatic transitive casts
+                // parse_quote! {
+                //     unsafe impl ::cxx_qt::MainCast for #struct_name {
+                //        type Base = #base_qualified;
+                //     }
+                // }
+            ],
         })
     }
 

examples/qml_minimal/qml/main.qml

@@ -28,6 +28,11 @@ ApplicationWindow {
         string: qsTr("My String with my number: %1").arg(myObject.number)
     }
 
+    A {
+        id: a
+        number: 10
+    }
+
     Column {
         anchors.fill: parent
         anchors.margins: 10
@@ -55,6 +60,12 @@ ApplicationWindow {
             onClicked: myObject.sayHi(myObject.string, myObject.number)
         }
 
+        Button {
+            text: qsTr("Test A")
+
+            onClicked: a.test()
+        }
+
         Button {
             text: qsTr("Quit")