Use () instead of PhantomData as IdentityManager's Input type.

PhantomData suggests that there's some sort of persuasion required for lifetime variance inference or other sorts of arcana, but it doesn't seem to be necessary at all. `()` works just fine.
gfx-rs · Aug 19, 2022 · ce3e2f7 · ce3e2f7
1 parent c6ca2a7
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -74,7 +74,7 @@ the same every time it is rendered, we now warn if it is missing.
 - Added downlevel restriction error message for `InvalidFormatUsages` error by @Seamooo in [#2886](https://github.com/gfx-rs/wgpu/pull/2886)
 - Add warning when using CompareFunction::*Equal with vertex shader that is missing @invariant tag by @cwfitzgerald in [#2887](https://github.com/gfx-rs/wgpu/pull/2887)
 - Update Winit to version 0.27 and raw-window-handle to 0.5 by @wyatt-herkamp in  [#2918](https://github.com/gfx-rs/wgpu/pull/2918)
-
+- Don't use `PhantomData` for `IdentityManager`'s `Input` type. By @jimblandy in [#2972](https://github.com/gfx-rs/wgpu/pull/2972)
 #### Metal
 - Extract the generic code into `get_metal_layer` by @jinleili in [#2826](https://github.com/gfx-rs/wgpu/pull/2826)
 

diff --git a/wgpu-core/src/hub.rs b/wgpu-core/src/hub.rs
@@ -438,7 +438,7 @@ pub trait IdentityHandler<I>: Debug {
 }
 
 impl<I: id::TypedId + Debug> IdentityHandler<I> for Mutex<IdentityManager> {
-    type Input = PhantomData<I>;
+    type Input = ();
     fn process(&self, _id: Self::Input, backend: Backend) -> I {
         self.lock().alloc(backend)
     }

diff --git a/wgpu/src/backend/direct.rs b/wgpu/src/backend/direct.rs
@@ -15,7 +15,6 @@ use std::{
     error::Error,
     fmt,
     future::{ready, Ready},
-    marker::PhantomData,
     ops::Range,
     slice,
     sync::Arc,
@@ -69,17 +68,15 @@ impl Context {
     #[cfg(any(not(target_arch = "wasm32"), feature = "emscripten"))]
     pub fn enumerate_adapters(&self, backends: wgt::Backends) -> Vec<wgc::id::AdapterId> {
         self.0
-            .enumerate_adapters(wgc::instance::AdapterInputs::Mask(backends, |_| {
-                PhantomData
-            }))
+            .enumerate_adapters(wgc::instance::AdapterInputs::Mask(backends, |_| ()))
     }
 
     #[cfg(any(not(target_arch = "wasm32"), feature = "emscripten"))]
     pub unsafe fn create_adapter_from_hal<A: wgc::hub::HalApi>(
         &self,
         hal_adapter: hal::ExposedAdapter<A>,
     ) -> wgc::id::AdapterId {
-        self.0.create_adapter_from_hal(hal_adapter, PhantomData)
+        self.0.create_adapter_from_hal(hal_adapter, ())
     }
 
     pub unsafe fn adapter_as_hal<A: wgc::hub::HalApi, F: FnOnce(Option<&A::Adapter>) -> R, R>(
@@ -105,7 +102,7 @@ impl Context {
             hal_device,
             &desc.map_label(|l| l.map(Borrowed)),
             trace_dir,
-            PhantomData,
+            (),
         );
         if let Some(err) = error {
             self.handle_error_fatal(err, "Adapter::create_device_from_hal");
@@ -130,7 +127,7 @@ impl Context {
             hal_texture,
             device.id,
             &desc.map_label(|l| l.map(Borrowed)),
-            PhantomData,
+            (),
         );
         if let Some(cause) = error {
             self.handle_error(
@@ -177,7 +174,7 @@ impl Context {
         self: &Arc<Self>,
         layer: *mut std::ffi::c_void,
     ) -> crate::Surface {
-        let id = self.0.instance_create_surface_metal(layer, PhantomData);
+        let id = self.0.instance_create_surface_metal(layer, ());
         crate::Surface {
             context: Arc::clone(self),
             id: Surface {
@@ -192,7 +189,7 @@ impl Context {
         self: &Arc<Self>,
         canvas: &web_sys::HtmlCanvasElement,
     ) -> Surface {
-        let id = self.0.create_surface_webgl_canvas(canvas, PhantomData);
+        let id = self.0.create_surface_webgl_canvas(canvas, ());
         Surface {
             id,
             configured_device: Mutex::default(),
@@ -204,9 +201,7 @@ impl Context {
         self: &Arc<Self>,
         canvas: &web_sys::OffscreenCanvas,
     ) -> Surface {
-        let id = self
-            .0
-            .create_surface_webgl_offscreen_canvas(canvas, PhantomData);
+        let id = self.0.create_surface_webgl_offscreen_canvas(canvas, ());
         Surface {
             id,
             configured_device: Mutex::default(),
@@ -218,9 +213,7 @@ impl Context {
         self: &Arc<Self>,
         visual: *mut std::ffi::c_void,
     ) -> crate::Surface {
-        let id = self
-            .0
-            .instance_create_surface_from_visual(visual, PhantomData);
+        let id = self.0.instance_create_surface_from_visual(visual, ());
         crate::Surface {
             context: Arc::clone(self),
             id: Surface {
@@ -853,7 +846,7 @@ impl crate::Context for Context {
         handle: &(impl raw_window_handle::HasRawWindowHandle + raw_window_handle::HasRawDisplayHandle),
     ) -> Self::SurfaceId {
         Surface {
-            id: self.0.instance_create_surface(handle, PhantomData),
+            id: self.0.instance_create_surface(handle, ()),
             configured_device: Mutex::new(None),
         }
     }
@@ -868,7 +861,7 @@ impl crate::Context for Context {
                 force_fallback_adapter: options.force_fallback_adapter,
                 compatible_surface: options.compatible_surface.map(|surface| surface.id.id),
             },
-            wgc::instance::AdapterInputs::Mask(wgt::Backends::all(), |_| PhantomData),
+            wgc::instance::AdapterInputs::Mask(wgt::Backends::all(), |_| ()),
         );
         ready(id.ok())
     }
@@ -892,7 +885,7 @@ impl crate::Context for Context {
             *adapter,
             &desc.map_label(|l| l.map(Borrowed)),
             trace_dir,
-            PhantomData
+            ()
         ));
         if let Some(err) = error {
             log::error!("Error in Adapter::request_device: {}", err);
@@ -1022,7 +1015,7 @@ impl crate::Context for Context {
             .lock()
             .expect("Surface was not configured?");
         match wgc::gfx_select!(
-            device_id => global.surface_get_current_texture(surface.id, PhantomData)
+            device_id => global.surface_get_current_texture(surface.id, ())
         ) {
             Ok(wgc::present::SurfaceOutput { status, texture_id }) => (
                 texture_id.map(|id| Texture {
@@ -1127,7 +1120,7 @@ impl crate::Context for Context {
             ShaderSource::Naga(module) => wgc::pipeline::ShaderModuleSource::Naga(module),
         };
         let (id, error) = wgc::gfx_select!(
-            device.id => global.device_create_shader_module(device.id, &descriptor, source, PhantomData)
+            device.id => global.device_create_shader_module(device.id, &descriptor, source, ())
         );
         if let Some(cause) = error {
             self.handle_error(
@@ -1154,7 +1147,7 @@ impl crate::Context for Context {
             shader_bound_checks: wgt::ShaderBoundChecks::unchecked(),
         };
         let (id, error) = wgc::gfx_select!(
-            device.id => global.device_create_shader_module_spirv(device.id, &descriptor, Borrowed(&desc.source), PhantomData)
+            device.id => global.device_create_shader_module_spirv(device.id, &descriptor, Borrowed(&desc.source), ())
         );
         if let Some(cause) = error {
             self.handle_error(
@@ -1179,7 +1172,7 @@ impl crate::Context for Context {
             entries: Borrowed(desc.entries),
         };
         let (id, error) = wgc::gfx_select!(
-            device.id => global.device_create_bind_group_layout(device.id, &descriptor, PhantomData)
+            device.id => global.device_create_bind_group_layout(device.id, &descriptor, ())
         );
         if let Some(cause) = error {
             self.handle_error(
@@ -1280,7 +1273,7 @@ impl crate::Context for Context {
         let (id, error) = wgc::gfx_select!(device.id => global.device_create_bind_group(
             device.id,
             &descriptor,
-            PhantomData
+            ()
         ));
         if let Some(cause) = error {
             self.handle_error(
@@ -1323,7 +1316,7 @@ impl crate::Context for Context {
         let (id, error) = wgc::gfx_select!(device.id => global.device_create_pipeline_layout(
             device.id,
             &descriptor,
-            PhantomData
+            ()
         ));
         if let Some(cause) = error {
             self.handle_error(
@@ -1358,8 +1351,8 @@ impl crate::Context for Context {
         let implicit_pipeline_ids = match desc.layout {
             Some(_) => None,
             None => Some(wgc::device::ImplicitPipelineIds {
-                root_id: PhantomData,
-                group_ids: &[PhantomData; wgc::MAX_BIND_GROUPS],
+                root_id: (),
+                group_ids: &[(); wgc::MAX_BIND_GROUPS],
             }),
         };
         let descriptor = pipe::RenderPipelineDescriptor {
@@ -1389,7 +1382,7 @@ impl crate::Context for Context {
         let (id, error) = wgc::gfx_select!(device.id => global.device_create_render_pipeline(
             device.id,
             &descriptor,
-            PhantomData,
+            (),
             implicit_pipeline_ids
         ));
         if let Some(cause) = error {
@@ -1418,8 +1411,8 @@ impl crate::Context for Context {
         let implicit_pipeline_ids = match desc.layout {
             Some(_) => None,
             None => Some(wgc::device::ImplicitPipelineIds {
-                root_id: PhantomData,
-                group_ids: &[PhantomData; wgc::MAX_BIND_GROUPS],
+                root_id: (),
+                group_ids: &[(); wgc::MAX_BIND_GROUPS],
             }),
         };
         let descriptor = pipe::ComputePipelineDescriptor {
@@ -1435,7 +1428,7 @@ impl crate::Context for Context {
         let (id, error) = wgc::gfx_select!(device.id => global.device_create_compute_pipeline(
             device.id,
             &descriptor,
-            PhantomData,
+            (),
             implicit_pipeline_ids
         ));
         if let Some(cause) = error {
@@ -1467,7 +1460,7 @@ impl crate::Context for Context {
         let (id, error) = wgc::gfx_select!(device.id => global.device_create_buffer(
             device.id,
             &desc.map_label(|l| l.map(Borrowed)),
-            PhantomData
+            ()
         ));
         if let Some(cause) = error {
             self.handle_error(
@@ -1493,7 +1486,7 @@ impl crate::Context for Context {
         let (id, error) = wgc::gfx_select!(device.id => global.device_create_texture(
             device.id,
             &desc.map_label(|l| l.map(Borrowed)),
-            PhantomData
+            ()
         ));
         if let Some(cause) = error {
             self.handle_error(
@@ -1536,7 +1529,7 @@ impl crate::Context for Context {
         let (id, error) = wgc::gfx_select!(device.id => global.device_create_sampler(
             device.id,
             &descriptor,
-            PhantomData
+            ()
         ));
         if let Some(cause) = error {
             self.handle_error(
@@ -1559,7 +1552,7 @@ impl crate::Context for Context {
         let (id, error) = wgc::gfx_select!(device.id => global.device_create_query_set(
             device.id,
             &desc.map_label(|l| l.map(Borrowed)),
-            PhantomData
+            ()
         ));
         if let Some(cause) = error {
             self.handle_error_nolabel(&device.error_sink, cause, "Device::create_query_set");
@@ -1576,7 +1569,7 @@ impl crate::Context for Context {
         let (id, error) = wgc::gfx_select!(device.id => global.device_create_command_encoder(
             device.id,
             &desc.map_label(|l| l.map(Borrowed)),
-            PhantomData
+            ()
         ));
         if let Some(cause) = error {
             self.handle_error(
@@ -1742,7 +1735,7 @@ impl crate::Context for Context {
         };
         let global = &self.0;
         let (id, error) = wgc::gfx_select!(
-            texture.id => global.texture_create_view(texture.id, &descriptor, PhantomData)
+            texture.id => global.texture_create_view(texture.id, &descriptor, ())
         );
         if let Some(cause) = error {
             self.handle_error(
@@ -1848,7 +1841,7 @@ impl crate::Context for Context {
         index: u32,
     ) -> Self::BindGroupLayoutId {
         let global = &self.0;
-        let (id, error) = wgc::gfx_select!(*pipeline => global.compute_pipeline_get_bind_group_layout(*pipeline, index, PhantomData));
+        let (id, error) = wgc::gfx_select!(*pipeline => global.compute_pipeline_get_bind_group_layout(*pipeline, index, ()));
         if let Some(err) = error {
             panic!("Error reflecting bind group {}: {}", index, err);
         }
@@ -1860,7 +1853,7 @@ impl crate::Context for Context {
         index: u32,
     ) -> Self::BindGroupLayoutId {
         let global = &self.0;
-        let (id, error) = wgc::gfx_select!(*pipeline => global.render_pipeline_get_bind_group_layout(*pipeline, index, PhantomData));
+        let (id, error) = wgc::gfx_select!(*pipeline => global.render_pipeline_get_bind_group_layout(*pipeline, index, ()));
         if let Some(err) = error {
             panic!("Error reflecting bind group {}: {}", index, err);
         }
@@ -2183,7 +2176,7 @@ impl crate::Context for Context {
         let (id, error) = wgc::gfx_select!(encoder.parent() => global.render_bundle_encoder_finish(
             encoder,
             &desc.map_label(|l| l.map(Borrowed)),
-            PhantomData
+            ()
         ));
         if let Some(err) = error {
             self.handle_error_fatal(err, "RenderBundleEncoder::finish");
@@ -2230,7 +2223,7 @@ impl crate::Context for Context {
     ) -> QueueWriteBuffer {
         let global = &self.0;
         match wgc::gfx_select!(
-            *queue => global.queue_create_staging_buffer(*queue, size, PhantomData)
+            *queue => global.queue_create_staging_buffer(*queue, size, ())
         ) {
             Ok((buffer_id, ptr)) => QueueWriteBuffer {
                 buffer_id,