fix panic with as_hal functions (#2871)

CHANGELOG.md

@@ -49,6 +49,7 @@ Bottom level categories:
 - `get_texture_format_features` only lists the COPY_* usages if the adapter actually supports that usage by @cwfitzgerald in [#2856](https://github.com/gfx-rs/wgpu/pull/2856)
 - Improve the validation and error reporting of buffer mappings by @nical in [#2848](https://github.com/gfx-rs/wgpu/pull/2848)
 - Fix bind group / pipeline deduplication not taking into account RenderBundle execution resetting these values by @shoebe [#2867](https://github.com/gfx-rs/wgpu/pull/2867)
+- Fix panics that occur when using `as_hal` functions when the hal generic type does not match the hub being looked up in by @i509VCB [#2871](https://github.com/gfx-rs/wgpu/pull/2871)
 
 #### DX12
 - `DownlevelCapabilities::default()` now returns the `ANISOTROPIC_FILTERING` flag set to true so DX12 lists `ANISOTROPIC_FILTERING` as true again by @cwfitzgerald in [#2851](https://github.com/gfx-rs/wgpu/pull/2851)

wgpu-core/src/hub.rs

@@ -158,6 +158,28 @@ impl<T, I: id::TypedId> Storage<T, I> {
         }
     }
 
+    /// Attempts to get a reference to an item behind a potentially invalid ID.
+    ///
+    /// Returns [`None`] if there is an epoch mismatch, or the entry is empty.
+    ///
+    /// This function is primarily intended for the `as_hal` family of functions where you may need to
+    /// fallibly get a object backed by an id that could be in a different hub.
+    pub(crate) fn try_get(&self, id: I) -> Result<Option<&T>, InvalidId> {
+        let (index, epoch, _) = id.unzip();
+        let (result, storage_epoch) = match self.map.get(index as usize) {
+            Some(&Element::Occupied(ref v, epoch)) => (Ok(Some(v)), epoch),
+            Some(&Element::Vacant) => return Ok(None),
+            Some(&Element::Error(epoch, ..)) => (Err(InvalidId), epoch),
+            None => return Err(InvalidId),
+        };
+        assert_eq!(
+            epoch, storage_epoch,
+            "{}[{}] is no longer alive",
+            self.kind, index
+        );
+        result
+    }
+
     /// Get a reference to an item behind a potentially invalid ID.
     /// Panics if there is an epoch mismatch, or the entry is empty.
     pub(crate) fn get(&self, id: I) -> Result<&T, InvalidId> {

wgpu-core/src/resource.rs

@@ -326,7 +326,7 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
         let hub = A::hub(self);
         let mut token = Token::root();
         let (guard, _) = hub.textures.read(&mut token);
-        let texture = guard.get(id).ok();
+        let texture = guard.try_get(id).ok().flatten();
         let hal_texture = texture.map(|tex| tex.inner.as_raw().unwrap());
 
         hal_texture_callback(hal_texture);
@@ -346,7 +346,7 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
         let mut token = Token::root();
 
         let (guard, _) = hub.adapters.read(&mut token);
-        let adapter = guard.get(id).ok();
+        let adapter = guard.try_get(id).ok().flatten();
         let hal_adapter = adapter.map(|adapter| &adapter.raw.adapter);
 
         hal_adapter_callback(hal_adapter)
@@ -365,7 +365,7 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
         let hub = A::hub(self);
         let mut token = Token::root();
         let (guard, _) = hub.devices.read(&mut token);
-        let device = guard.get(id).ok();
+        let device = guard.try_get(id).ok().flatten();
         let hal_device = device.map(|device| &device.raw);
 
         hal_device_callback(hal_device)