Put the component in a Pin<>

Removed the drop and create from the ComponentVTable:
since we are not using VBox<ComponentVTable>, this simplifies a bit
the code of the interpreter and everything else.

But there is still a lot of changes everywhere to support that the Component
is pinned.
This is just for the component. Which would be required if later we want
to access the properties as Pin<Property<_>>. But we have not yet ability
to do projections

helper_crates/vtable/src/lib.rs

@@ -57,7 +57,7 @@ that `cbindgen` can see the actual vtable.
 pub use const_field_offset::FieldOffset;
 use core::marker::PhantomData;
 use core::ops::{Deref, DerefMut, Drop};
-use core::ptr::NonNull;
+use core::{pin::Pin, ptr::NonNull};
 #[doc(inline)]
 pub use vtable_macro::*;
 
@@ -230,6 +230,20 @@ impl<'a, T: ?Sized + VTableMeta> VRef<'a, T> {
         }
     }
 
+    /// Create a new Pin<VRef<_>> from a pinned reference. This is similar to `VRef::new`
+    pub fn new_pin<X: HasStaticVTable<T>>(value: core::pin::Pin<&'a X>) -> Pin<Self> {
+        // Since Value is pinned, this means it is safe to construct a Pin
+        unsafe {
+            Pin::new_unchecked(Self {
+                inner: Inner {
+                    vtable: X::static_vtable() as *const T::VTable as *const u8,
+                    ptr: value.get_ref() as *const X as *const u8,
+                },
+                phantom: PhantomData,
+            })
+        }
+    }
+
     unsafe fn from_inner(inner: Inner) -> Self {
         Self { inner, phantom: PhantomData }
     }
@@ -251,6 +265,17 @@ impl<'a, T: ?Sized + VTableMeta> VRef<'a, T> {
             None
         }
     }
+
+    /// Return to a reference of the given type if the type is actually matching
+    pub fn downcast_pin<X: HasStaticVTable<T>>(this: Pin<Self>) -> Option<Pin<&'a X>> {
+        let inner = unsafe { Pin::into_inner_unchecked(this).inner };
+        if inner.vtable == X::static_vtable() as *const _ as *const u8 {
+            // Safety: We just checked that the vtable fits
+            unsafe { Some(Pin::new_unchecked(&*(inner.ptr as *const X))) }
+        } else {
+            None
+        }
+    }
 }
 
 /// `VRefMut<'a MyTraitVTable>` can be thought as a `&'a mut dyn MyTrait`