rust: qom: move ClassInitImpl to the instance side

Put all traits on the instance struct, which makes it possible to reuse
class structs if no new virtual methods or class fields are added.
This is almost always the case for devices (because they are leaf
classes), which is the primary use case for Rust.

This is also simpler: soon we will find the implemented methods without
macros, and this removes the need to go from the class struct to the
instance struct to find the implementation of the *Impl traits.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

rust/hw/char/pl011/src/device.rs

@@ -116,7 +116,7 @@ pub struct PL011Class {
     _inner: [u8; 0],
 }
 
-impl qemu_api::definitions::ClassInitImpl for PL011Class {
+impl qemu_api::definitions::ClassInitImpl for PL011State {
     const CLASS_INIT: Option<unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void)> =
         Some(crate::device_class::pl011_class_init);
     const CLASS_BASE_INIT: Option<
@@ -649,7 +649,7 @@ pub struct PL011LuminaryClass {
     }
 }
 
-impl qemu_api::definitions::ClassInitImpl for PL011LuminaryClass {
+impl qemu_api::definitions::ClassInitImpl for PL011Luminary {
     const CLASS_INIT: Option<unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void)> =
         None;
     const CLASS_BASE_INIT: Option<

rust/qemu-api/src/definitions.rs

@@ -9,8 +9,8 @@
 use crate::bindings::{Object, ObjectClass, TypeInfo};
 
 /// Trait a type must implement to be registered with QEMU.
-pub trait ObjectImpl: Sized {
-    type Class: ClassInitImpl;
+pub trait ObjectImpl: ClassInitImpl + Sized {
+    type Class;
     const TYPE_NAME: &'static CStr;
     const PARENT_TYPE_NAME: Option<&'static CStr>;
     const ABSTRACT: bool = false;
@@ -32,8 +32,8 @@ pub trait ObjectImpl: Sized {
         instance_finalize: Self::INSTANCE_FINALIZE,
         abstract_: Self::ABSTRACT,
         class_size: core::mem::size_of::<Self::Class>(),
-        class_init: <Self::Class as ClassInitImpl>::CLASS_INIT,
-        class_base_init: <Self::Class as ClassInitImpl>::CLASS_BASE_INIT,
+        class_init: <Self as ClassInitImpl>::CLASS_INIT,
+        class_base_init: <Self as ClassInitImpl>::CLASS_BASE_INIT,
         class_data: core::ptr::null_mut(),
         interfaces: core::ptr::null_mut(),
     };

rust/qemu-api/tests/tests.rs

@@ -59,7 +59,7 @@ impl ObjectImpl for DummyState {
         const PARENT_TYPE_NAME: Option<&'static CStr> = Some(device_class::TYPE_DEVICE);
     }
 
-    impl ClassInitImpl for DummyClass {
+    impl ClassInitImpl for DummyState {
         const CLASS_INIT: Option<unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void)> =
             Some(dummy_class_init);
         const CLASS_BASE_INIT: Option<