nightly alloc trait support

.github/workflows/ci.yml

@@ -28,7 +28,7 @@ jobs:
         with:
           tool: just,cargo-hack,cargo-sync-rdme
       - name: Lint (clippy)
-        run: just powerset --partition ${{ matrix.partition }}/10 clippy --all-targets
+        run: just powerset --exclude-features nightly --partition ${{ matrix.partition }}/10 clippy --all-targets
       - name: Lint (rustfmt)
         run: cargo xfmt --check
       - name: Run rustdoc
@@ -67,11 +67,11 @@ jobs:
       - uses: taiki-e/install-action@just
       - uses: taiki-e/install-action@nextest
       - name: Build
-        run: just powerset --partition ${{ matrix.partition }}/10 build
+        run: just powerset --exclude-features nightly --partition ${{ matrix.partition }}/10 build
       - name: Run tests
-        run: just powerset --partition ${{ matrix.partition }}/10 nextest run
+        run: just powerset --exclude-features nightly --partition ${{ matrix.partition }}/10 nextest run
       - name: Doctests
-        run: just powerset --partition ${{ matrix.partition }}/10 test --doc
+        run: just powerset --exclude-features nightly --partition ${{ matrix.partition }}/10 test --doc
 
   build-no-std:
     name: Build on no-std

crates/iddqd/Cargo.toml

@@ -46,6 +46,7 @@ allocator-api2 = ["iddqd-test-utils/allocator-api2"]
 daft = ["dep:daft", "dep:ref-cast"]
 default = ["allocator-api2", "std", "default-hasher"]
 default-hasher = ["dep:foldhash", "iddqd-test-utils/default-hasher"]
+nightly = []
 proptest = ["dep:proptest"]
 schemars08 = ["dep:schemars", "dep:serde_json", "serde"]
 serde = ["dep:serde_core", "iddqd-test-utils/serde"]

crates/iddqd/README.md

@@ -289,6 +289,10 @@ platform-specific notion of thread locals, would suffice to make
 * `default-hasher`: Enables the `DefaultHashBuilder` type. Disable this
   feature to require a hash builder type parameter to be passed into
   [`IdHashMap`](https://docs.rs/iddqd/0.4.0/iddqd/id_hash_map/imp/struct.IdHashMap.html), [`BiHashMap`](https://docs.rs/iddqd/0.4.0/iddqd/bi_hash_map/imp/struct.BiHashMap.html), and [`TriHashMap`](https://docs.rs/iddqd/0.4.0/iddqd/tri_hash_map/imp/struct.TriHashMap.html). *Enabled by default.*
+* `nightly`: Enables support for the nightly `core::alloc::Allocator` trait.
+  Requires a nightly Rust compiler. When enabled, map types accept any type
+  implementing `core::alloc::Allocator` as a custom allocator. *Not enabled
+  by default.*
 * `proptest`: Enables [`proptest`](https://docs.rs/proptest/1.7.0/proptest/index.html) support for all ID map types, providing
   [`Arbitrary`] implementations and strategies for property-based testing.
   *Not enabled by default.*

crates/iddqd/src/lib.rs

@@ -317,6 +317,10 @@
 //! - `default-hasher`: Enables the `DefaultHashBuilder` type. Disable this
 //!   feature to require a hash builder type parameter to be passed into
 //!   [`IdHashMap`], [`BiHashMap`], and [`TriHashMap`]. *Enabled by default.*
+//! - `nightly`: Enables support for the nightly `core::alloc::Allocator` trait.
+//!   Requires a nightly Rust compiler. When enabled, map types accept any type
+//!   implementing `core::alloc::Allocator` as a custom allocator. *Not enabled
+//!   by default.*
 //! - `proptest`: Enables [`proptest`] support for all ID map types, providing
 //!   [`Arbitrary`] implementations and strategies for property-based testing.
 //!   *Not enabled by default.*
@@ -367,6 +371,7 @@
 
 #![no_std]
 #![cfg_attr(doc_cfg, feature(doc_cfg))]
+#![cfg_attr(feature = "nightly", feature(allocator_api))]
 #![warn(missing_docs)]
 
 #[cfg_attr(not(feature = "std"), macro_use)] // for `format!`

crates/iddqd/src/support/alloc.rs

@@ -5,8 +5,6 @@
 pub use self::inner::Global;
 pub(crate) use self::inner::{AllocWrapper, Allocator, global_alloc};
 
-// TODO: support nightly.
-
 // Basic non-nightly case.
 #[cfg(feature = "allocator-api2")]
 mod inner {
@@ -103,3 +101,30 @@ mod inner {
         }
     }
 }
+
+// Nightly support: implement `core::alloc::Allocator` for `AllocWrapper`.
+// This bridges `allocator_api2::alloc::Allocator` types to the nightly
+// `core::alloc::Allocator` trait, allowing `AllocWrapper` to be used where
+// the standard library allocator trait is expected.
+#[cfg(feature = "nightly")]
+// SAFETY: These functions just forward to the wrapped allocator.
+unsafe impl<T: Allocator> alloc::alloc::Allocator for AllocWrapper<T> {
+    #[inline]
+    fn allocate(
+        &self,
+        layout: alloc::alloc::Layout,
+    ) -> Result<core::ptr::NonNull<[u8]>, alloc::alloc::AllocError> {
+        Allocator::allocate(&self.0, layout)
+            .map_err(|_| alloc::alloc::AllocError)
+    }
+
+    #[inline]
+    unsafe fn deallocate(
+        &self,
+        ptr: core::ptr::NonNull<u8>,
+        layout: alloc::alloc::Layout,
+    ) {
+        // SAFETY: caller upholds safety contract.
+        unsafe { Allocator::deallocate(&self.0, ptr, layout) }
+    }
+}