Add WriteOnly type.

`WriteOnly<'a, T>` is a custom smart pointer which is stricter than
`&'a mut [T]` in that it only allows writing data and not reading it.
This will be part of the fix for <gfx-rs#8897>.

This commit only introduces the public type and does not use it.

Author: kpreid

.github/workflows/ci.yml

@@ -743,6 +743,41 @@ jobs:
 
           cargo --locked test --doc
 
+  miri:
+    # runtime is normally 2 minutes
+    timeout-minutes: 10
+
+    name: Miri (limited scope)
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v6
+
+      # Miri is *only* available on nightly.
+      - name: Install nightly toolchain
+      
+        run: |
+          rustup toolchain install nightly --no-self-update --profile=minimal --component miri
+          rustup override set nightly
+          cargo -V
+
+      - name: Caching
+        uses: Swatinem/rust-cache@v2
+        with:
+          key: miri-${{ env.CACHE_SUFFIX }}
+
+      - name: Run Miri on selected tests
+        shell: bash
+        run: |
+          set -e
+
+          # Note: this is a *smaller* set of tests than `cargo xtask miri` runs;
+          # it is ones that are both important and cheap.
+          # Consider expanding it to include some API tests with the noop backend.
+          cargo miri test --package=wgpu --no-default-features -- write_only
+
+
   fmt:
     # runtime is normally 15 seconds
     timeout-minutes: 2

wgpu/src/lib.rs

@@ -96,7 +96,7 @@
 #![cfg_attr(not(any(wgpu_core, webgpu)), allow(unused))]
 
 extern crate alloc;
-#[cfg(std)]
+#[cfg(any(std, test))]
 extern crate std;
 #[cfg(wgpu_core)]
 pub extern crate wgpu_core as wgc;
@@ -116,6 +116,7 @@ mod cmp;
 mod dispatch;
 mod macros;
 pub mod util;
+mod write_only;
 
 //
 //
@@ -155,6 +156,7 @@ pub use wgt::{
     MAXIMUM_SUBGROUP_MAX_SIZE, MINIMUM_SUBGROUP_MIN_SIZE, QUERY_RESOLVE_BUFFER_ALIGNMENT,
     QUERY_SET_MAX_QUERIES, QUERY_SIZE, VERTEX_ALIGNMENT,
 };
+pub use write_only::{WriteOnly, WriteOnlyIter};
 
 #[expect(deprecated)]
 pub use wgt::VERTEX_STRIDE_ALIGNMENT;