Const functions are stable since 1.61, so no need to feature guard them.

.github/workflows/rust.yml

@@ -24,5 +24,7 @@ jobs:
       run: cargo build --verbose
     - name: Build without default features
       run: cargo build --no-default-features --verbose
+    - name: Build with all features
+      run: cargo build --all-features --verbose
     - name: Run tests
       run: cargo test --verbose

Cargo.toml

@@ -17,7 +17,6 @@ license = "MIT"
 [features]
 default = ["alloc", "use_spin"]
 alloc = []
-const_fn = []
 use_spin = ["spin"]
 
 [dependencies.spin]

README.md

@@ -34,7 +34,6 @@ You can also use `FrameAllocator` and `LockedHeapWithRescue`, see their document
   global allocator.
 - **`use_spin`** (default): Provide a `LockedHeap` type that implements the [`GlobalAlloc`] trait by
   using a spinlock.
-- **`const_fn`** (nightly only): Provide const fn version of `LockedHeapWithRescue::new`.
 
 [`GlobalAlloc`]: https://doc.rust-lang.org/nightly/core/alloc/trait.GlobalAlloc.html
 

src/lib.rs

@@ -1,4 +1,3 @@
-#![cfg_attr(feature = "const_fn", feature(const_mut_refs, const_fn_fn_ptr_basics))]
 #![no_std]
 
 #[cfg(test)]
@@ -293,22 +292,12 @@ pub struct LockedHeapWithRescue<const ORDER: usize> {
 #[cfg(feature = "use_spin")]
 impl<const ORDER: usize> LockedHeapWithRescue<ORDER> {
     /// Creates an empty heap
-    #[cfg(feature = "const_fn")]
     pub const fn new(rescue: fn(&mut Heap<ORDER>, &Layout)) -> Self {
         LockedHeapWithRescue {
             inner: Mutex::new(Heap::<ORDER>::new()),
             rescue,
         }
     }
-
-    /// Creates an empty heap
-    #[cfg(not(feature = "const_fn"))]
-    pub fn new(rescue: fn(&mut Heap<ORDER>, &Layout)) -> Self {
-        LockedHeapWithRescue {
-            inner: Mutex::new(Heap::<ORDER>::new()),
-            rescue,
-        }
-    }
 }
 
 #[cfg(feature = "use_spin")]