[PATCH 5/5] rust: qdev: const_refs_to_static

[Paolo Bonzini]

Now that const_refs_to_static can be assumed, convert the members of
the DeviceImpl trait from functions to constants.  This lets the
compiler know that they have a 'static lifetime, and removes the
need for the weird "Box::leak()".

Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
 rust/hw/char/pl011/src/device.rs |  8 ++------
 rust/hw/timer/hpet/src/hpet.rs   | 10 ++--------
 rust/qemu-api/src/qdev.rs        | 16 +++++-----------
 rust/qemu-api/tests/tests.rs     |  8 ++------
 4 files changed, 11 insertions(+), 31 deletions(-)

diff --git a/rust/hw/char/pl011/src/device.rs b/rust/hw/char/pl011/src/device.rs
index 38373f54e7c..34aa2bbabec 100644
--- a/rust/hw/char/pl011/src/device.rs
+++ b/rust/hw/char/pl011/src/device.rs
@@ -169,12 +169,8 @@ impl ObjectImpl for PL011State {
 }
 
 impl DeviceImpl for PL011State {
-    fn properties() -> &'static [Property] {
-        &device_class::PL011_PROPERTIES
-    }
-    fn vmsd() -> Option<VMStateDescription<Self>> {
-        Some(device_class::VMSTATE_PL011)
-    }
+    const PROPERTIES: &'static [Property] = &device_class::PL011_PROPERTIES;
+    const VMSTATE: Option<VMStateDescription<Self>> = 
Some(device_class::VMSTATE_PL011);
     const REALIZE: Option<fn(&Self)> = Some(Self::realize);
 }
 
diff --git a/rust/hw/timer/hpet/src/hpet.rs b/rust/hw/timer/hpet/src/hpet.rs
index be3b9afa316..48970a6f9c5 100644
--- a/rust/hw/timer/hpet/src/hpet.rs
+++ b/rust/hw/timer/hpet/src/hpet.rs
@@ -1009,14 +1009,8 @@ impl ObjectImpl for HPETState {
         .build();
 
 impl DeviceImpl for HPETState {
-    fn properties() -> &'static [Property] {
-        &HPET_PROPERTIES
-    }
-
-    fn vmsd() -> Option<VMStateDescription<Self>> {
-        Some(VMSTATE_HPET)
-    }
-
+    const PROPERTIES: &'static [Property] = &HPET_PROPERTIES;
+    const VMSTATE: Option<VMStateDescription<Self>> = Some(VMSTATE_HPET);
     const REALIZE: Option<fn(&Self)> = Some(Self::realize);
 }
 
diff --git a/rust/qemu-api/src/qdev.rs b/rust/qemu-api/src/qdev.rs
index 09555bbd0e7..9b2bfabdad2 100644
--- a/rust/qemu-api/src/qdev.rs
+++ b/rust/qemu-api/src/qdev.rs
@@ -113,16 +113,12 @@ pub trait DeviceImpl: ObjectImpl + ResettablePhasesImpl + 
IsA<DeviceState> {
     /// An array providing the properties that the user can set on the
     /// device.  Not a `const` because referencing statics in constants
     /// is unstable until Rust 1.83.0.
-    fn properties() -> &'static [Property] {
-        &[]
-    }
+    const PROPERTIES: &'static [Property] = &[];
 
     /// A `VMStateDescription` providing the migration format for the device
     /// Not a `const` because referencing statics in constants is unstable
     /// until Rust 1.83.0.
-    fn vmsd() -> Option<VMStateDescription<Self>> {
-        None
-    }
+    const VMSTATE: Option<VMStateDescription<Self>> = None;
 }
 
 /// # Safety
@@ -168,12 +164,10 @@ pub fn class_init<T: DeviceImpl>(&mut self) {
         if <T as DeviceImpl>::REALIZE.is_some() {
             self.realize = Some(rust_realize_fn::<T>);
         }
-        if let Some(vmsd) = <T as DeviceImpl>::vmsd() {
-            // Give a 'static lifetime to the return value of vmsd().
-            // Temporary until vmsd() can be changed into a const.
-            self.vmsd = Box::leak(Box::new(vmsd.get()));
+        if let Some(ref vmsd) = <T as DeviceImpl>::VMSTATE {
+            self.vmsd = vmsd.as_ref();
         }
-        let prop = <T as DeviceImpl>::properties();
+        let prop = <T as DeviceImpl>::PROPERTIES;
         if !prop.is_empty() {
             unsafe {
                 bindings::device_class_set_props_n(self, prop.as_ptr(), 
prop.len());
diff --git a/rust/qemu-api/tests/tests.rs b/rust/qemu-api/tests/tests.rs
index 3264641d128..db0fd3de99b 100644
--- a/rust/qemu-api/tests/tests.rs
+++ b/rust/qemu-api/tests/tests.rs
@@ -67,12 +67,8 @@ impl ObjectImpl for DummyState {
 impl ResettablePhasesImpl for DummyState {}
 
 impl DeviceImpl for DummyState {
-    fn properties() -> &'static [Property] {
-        &DUMMY_PROPERTIES
-    }
-    fn vmsd() -> Option<VMStateDescription<Self>> {
-        Some(VMSTATE)
-    }
+    const PROPERTIES: &'static [Property] = &DUMMY_PROPERTIES;
+    const VMSTATE: Option<VMStateDescription<Self>> = Some(VMSTATE);
 }
 
 #[repr(C)]
-- 
2.49.0