minor improvements, add some inline annotations

src/iter.rs

@@ -142,6 +142,7 @@ where
 {
     type Item = (S, String);
 
+    #[inline]
     fn next(&mut self) -> Option<Self::Item> {
         self.iter.next().map(|(num, boxed_str)| {
             (S::from_usize(num), Pin::into_inner(boxed_str).into_string())

src/lib.rs

@@ -1,7 +1,6 @@
 #![doc(html_root_url = "https://docs.rs/crate/string-interner/0.8.0")]
 #![cfg_attr(not(feature = "std"), no_std)]
 #![deny(missing_docs)]
-#![allow(unused_attributes)] // TODO: remove
 
 //! Caches strings efficiently, with minimal memory footprint and associates them with unique symbols.
 //! These symbols allow constant time comparisons and look-ups to the underlying interned strings.
@@ -123,12 +122,14 @@ impl PinnedStr {
 }
 
 impl Hash for PinnedStr {
+    #[inline]
     fn hash<H: Hasher>(&self, state: &mut H) {
         self.as_str().hash(state)
     }
 }
 
 impl PartialEq for PinnedStr {
+    #[inline]
     fn eq(&self, other: &Self) -> bool {
         self.as_str() == other.as_str()
     }
@@ -401,7 +402,7 @@ where
     }
 }
 
-impl<T, S> core::iter::Extend<T> for StringInterner<S>
+impl<T, S> Extend<T> for StringInterner<S>
 where
     S: Symbol,
     T: Into<String> + AsRef<str>,

src/symbol.rs

@@ -14,7 +14,7 @@ pub trait Symbol: Copy + Ord + Eq {
     /// # Note
     ///
     /// Implementations panic if the operation cannot succeed.
-    fn from_usize(val: usize) -> Self;
+    fn from_usize(index: usize) -> Self;
 
     /// Returns the `usize` representation of `self`.
     fn to_usize(self) -> usize;
@@ -36,19 +36,21 @@ impl Symbol for DefaultSymbol {
     /// # Panics
     ///
     /// If the given `usize` is greater than `u32::MAX - 1`.
-    fn from_usize(val: usize) -> Self {
+    #[inline]
+    fn from_usize(index: usize) -> Self {
         assert!(
-            val < core::u32::MAX as usize,
+            index < core::u32::MAX as usize,
             "{} is out of bounds for the default symbol",
-            val
+            index
         );
         Self(
-            NonZeroU32::new((val + 1) as u32)
+            NonZeroU32::new((index as u32) + 1)
                 // Due to the assert above we can assume that this always succeeds.
-                .unwrap_or_else(|| unsafe { core::hint::unreachable_unchecked() }),
+                .unwrap_or_else(|| unsafe { ::core::hint::unreachable_unchecked() }),
         )
     }
 
+    #[inline]
     fn to_usize(self) -> usize {
         (self.0.get() as usize) - 1
     }