chore: resolve all missing_const_for_fn clippy lints

roaring/src/bitmap/container.rs

@@ -26,7 +26,7 @@ pub(crate) struct Iter<'a> {
 }
 
 impl Container {
-    pub fn new(key: u16) -> Container {
+    pub const fn new(key: u16) -> Container {
         Container { key, store: Store::new() }
     }
 
@@ -61,7 +61,7 @@ impl Container {
         self.store.len()
     }
 
-    pub fn is_empty(&self) -> bool {
+    pub const fn is_empty(&self) -> bool {
         self.store.is_empty()
     }
 

roaring/src/bitmap/inherent.rs

@@ -20,7 +20,7 @@ impl RoaringBitmap {
     /// use roaring::RoaringBitmap;
     /// let rb = RoaringBitmap::new();
     /// ```
-    pub fn new() -> RoaringBitmap {
+    pub const fn new() -> RoaringBitmap {
         RoaringBitmap { containers: Vec::new() }
     }
 
@@ -635,7 +635,7 @@ impl RoaringBitmap {
     /// assert_eq!(rb.is_empty(), false);
     /// ```
     #[inline]
-    pub fn is_empty(&self) -> bool {
+    pub const fn is_empty(&self) -> bool {
         self.containers.is_empty()
     }
 

roaring/src/bitmap/serialization.rs

@@ -343,7 +343,7 @@ impl RoaringBitmap {
     }
 }
 
-fn header_size(size: usize, has_run_containers: bool) -> usize {
+const fn header_size(size: usize, has_run_containers: bool) -> usize {
     if has_run_containers {
         // New format encodes the size (number of containers) into the 4 byte cookie
         // Additionally a bitmap is included marking which containers are run containers

roaring/src/bitmap/store/array_store/mod.rs

@@ -79,15 +79,15 @@ fn intersect(lhs: &[u16], rhs: &[u16], visitor: &mut impl BinaryOperationVisitor
 }
 
 impl ArrayStore {
-    pub fn new() -> ArrayStore {
+    pub const fn new() -> ArrayStore {
         ArrayStore { vec: vec![] }
     }
 
-    pub fn serialized_byte_size(cardinality: u64) -> usize {
+    pub const fn serialized_byte_size(cardinality: u64) -> usize {
         cardinality as usize * ARRAY_ELEMENT_BYTES
     }
 
-    pub fn byte_size(&self) -> usize {
+    pub const fn byte_size(&self) -> usize {
         Self::serialized_byte_size(self.len())
     }
 
@@ -97,7 +97,7 @@ impl ArrayStore {
     }
 
     /// The number of total values that can be inserted without needing to reallocate.
-    pub fn capacity(&self) -> usize {
+    pub const fn capacity(&self) -> usize {
         self.vec.capacity()
     }
 
@@ -300,11 +300,11 @@ impl ArrayStore {
         BitmapStore::from_unchecked(len, bits)
     }
 
-    pub fn len(&self) -> u64 {
+    pub const fn len(&self) -> u64 {
         self.vec.len() as u64
     }
 
-    pub fn is_empty(&self) -> bool {
+    pub const fn is_empty(&self) -> bool {
         self.vec.is_empty()
     }
 

roaring/src/bitmap/store/array_store/vector.rs

@@ -31,6 +31,14 @@ const LANES: usize = 8;
 /// With `std`, this is detected at runtime on x86/x86-64 (and cached by `fearless_simd`).
 /// Otherwise, it is determined by the target features enabled at compile time.
 #[inline]
+// Scoped to `not(std)`, the only config where the lint fires; a plain `expect` would go unfulfilled.
+#[cfg_attr(
+    not(feature = "std"),
+    expect(
+        clippy::missing_const_for_fn,
+        reason = "`Level::new()` under `std` is runtime detection"
+    )
+)]
 fn level() -> Level {
     #[cfg(feature = "std")]
     return Level::new();

roaring/src/bitmap/store/array_store/visitor.rs

@@ -76,11 +76,11 @@ pub struct CardinalityCounter {
 }
 
 impl CardinalityCounter {
-    pub fn new() -> CardinalityCounter {
+    pub const fn new() -> CardinalityCounter {
         CardinalityCounter { count: 0 }
     }
 
-    pub fn into_inner(self) -> u64 {
+    pub const fn into_inner(self) -> u64 {
         self.count as u64
     }
 }

roaring/src/bitmap/store/bitmap_store.rs

@@ -26,7 +26,7 @@ impl BitmapStore {
         BitmapStore { len: 0, bits: Box::new([0; BITMAP_LENGTH]) }
     }
 
-    pub fn capacity(&self) -> usize {
+    pub const fn capacity(&self) -> usize {
         BITMAP_LENGTH * u64::BITS as usize
     }
 
@@ -282,11 +282,11 @@ impl BitmapStore {
         ArrayStore::from_vec_unchecked(vec)
     }
 
-    pub fn len(&self) -> u64 {
+    pub const fn len(&self) -> u64 {
         self.len
     }
 
-    pub fn is_empty(&self) -> bool {
+    pub const fn is_empty(&self) -> bool {
         self.len == 0
     }
 
@@ -834,12 +834,12 @@ impl<B: Borrow<[u64; BITMAP_LENGTH]>> DoubleEndedIterator for BitmapIter<B> {
 impl<B: Borrow<[u64; BITMAP_LENGTH]>> ExactSizeIterator for BitmapIter<B> {}
 
 #[inline]
-pub fn key(index: u16) -> usize {
+pub const fn key(index: u16) -> usize {
     index as usize / 64
 }
 
 #[inline]
-pub fn bit(index: u16) -> usize {
+pub const fn bit(index: u16) -> usize {
     index as usize % 64
 }
 

roaring/src/bitmap/store/interval_store.rs

@@ -32,11 +32,11 @@ impl IntervalStore {
         Self(alloc::vec![Interval::new_unchecked(0, u16::MAX)])
     }
 
-    pub fn byte_size(&self) -> usize {
+    pub const fn byte_size(&self) -> usize {
         Self::serialized_byte_size(self.run_amount())
     }
 
-    pub fn serialized_byte_size(run_amount: u64) -> usize {
+    pub const fn serialized_byte_size(run_amount: u64) -> usize {
         RUN_NUM_BYTES + (RUN_ELEMENT_BYTES * run_amount as usize)
     }
 
@@ -446,7 +446,7 @@ impl IntervalStore {
         self.0.iter().map(|iv| iv.run_len()).sum()
     }
 
-    pub fn is_empty(&self) -> bool {
+    pub const fn is_empty(&self) -> bool {
         self.0.is_empty()
     }
 
@@ -485,7 +485,7 @@ impl IntervalStore {
         None
     }
 
-    pub fn run_amount(&self) -> u64 {
+    pub const fn run_amount(&self) -> u64 {
         self.0.len() as u64
     }
 
@@ -678,7 +678,7 @@ pub(crate) struct RunIter<I: SliceIterator<Interval>> {
 }
 
 impl<I: SliceIterator<Interval>> RunIter<I> {
-    fn new(intervals: I) -> Self {
+    const fn new(intervals: I) -> Self {
         Self { forward_offset: 0, backward_offset: 0, intervals }
     }
 
@@ -956,7 +956,7 @@ impl IntoIterator for &'_ Interval {
     }
 }
 
-pub(crate) fn cmp_index_interval(index: u16, iv: Interval) -> Ordering {
+pub(crate) const fn cmp_index_interval(index: u16, iv: Interval) -> Ordering {
     if index < iv.start {
         Ordering::Less
     } else if index > iv.end {
@@ -972,15 +972,15 @@ impl Interval {
         Self { start, end }
     }
 
-    pub fn start(&self) -> u16 {
+    pub const fn start(&self) -> u16 {
         self.start
     }
 
-    pub fn end(&self) -> u16 {
+    pub const fn end(&self) -> u16 {
         self.end
     }
 
-    pub fn overlaps(&self, interval: &Self) -> bool {
+    pub const fn overlaps(&self, interval: &Self) -> bool {
         interval.start <= self.end && self.start <= interval.end
     }
 
@@ -996,7 +996,7 @@ impl Interval {
         u64::from(self.end - self.start) + 1
     }
 
-    pub fn is_full(&self) -> bool {
+    pub const fn is_full(&self) -> bool {
         self.start == 0 && self.end == u16::MAX
     }
 }

roaring/src/bitmap/store/mod.rs

@@ -42,7 +42,7 @@ pub(crate) enum Iter<'a> {
 }
 
 impl Store {
-    pub fn new() -> Store {
+    pub const fn new() -> Store {
         Store::Array(ArrayStore::new())
     }
 
@@ -257,7 +257,7 @@ impl Store {
         }
     }
 
-    pub fn is_empty(&self) -> bool {
+    pub const fn is_empty(&self) -> bool {
         match self {
             Array(vec) => vec.is_empty(),
             Bitmap(bits) => bits.is_empty(),

roaring/src/bitmap/util.rs

@@ -3,7 +3,7 @@ use core::ops::{Bound, RangeBounds, RangeInclusive};
 /// Returns the container key and the index
 /// in this container for a given integer.
 #[inline]
-pub fn split(value: u32) -> (u16, u16) {
+pub const fn split(value: u32) -> (u16, u16) {
     ((value >> 16) as u16, value as u16)
 }
 

roaring/src/lib.rs

@@ -53,7 +53,7 @@ pub struct NonSortedIntegers {
 
 impl NonSortedIntegers {
     /// Returns the number of elements that were
-    pub fn valid_until(&self) -> u64 {
+    pub const fn valid_until(&self) -> u64 {
         self.valid_until
     }
 }

roaring/src/treemap/inherent.rs

@@ -20,7 +20,7 @@ impl RoaringTreemap {
     /// use roaring::RoaringTreemap;
     /// let rb = RoaringTreemap::new();
     /// ```
-    pub fn new() -> RoaringTreemap {
+    pub const fn new() -> RoaringTreemap {
         RoaringTreemap { map: BTreeMap::new() }
     }
 

roaring/src/treemap/util.rs

@@ -1,7 +1,7 @@
 use core::ops::{Bound, RangeBounds, RangeInclusive};
 
 #[inline]
-pub fn split(value: u64) -> (u32, u32) {
+pub const fn split(value: u64) -> (u32, u32) {
     ((value >> 32) as u32, value as u32)
 }