Add Transitive casting and testing code

Author: BenFordTytherington

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

@@ -83,18 +83,11 @@ 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;
-                //     }
-                // }
-            ],
+                }
+            }],
         })
     }
 

crates/cxx-qt/src/casting.rs

@@ -127,6 +127,7 @@ unsafe impl<T> Upcast<T> for T {
         self
     }
 }
+
 /// Implements transitive casting in a chain for a type and all its ancestors
 ///
 /// Suppose you have 3 types, A, B and C where A -> B and B -> C casting relationships exist,

examples/qml_minimal/qml/main.qml

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