Make String::from_utf8_unchecked const

CHANGELOG.md

@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
   The implementation for sizes higher than u16::MAX were unsound anyway.
 - Added `shift_remove`, `shift_remove_entry` and `shift_remove_full` to `IndexMap` and `IndexSet`.
 - Implemented `Index` and `IndexMut` for `Vec`.
+- Made `String::from_utf8_unchecked` const. The v0.9.0 changelog already listed this, but the change was undone before that release.
 
 ## [v0.9.3] 2025-04-15
 

src/string/mod.rs

@@ -277,7 +277,7 @@ impl<LenT: LenType, const N: usize> String<N, LenT> {
     /// assert_eq!("💖", sparkle_heart);
     /// ```
     #[inline]
-    pub unsafe fn from_utf8_unchecked(vec: Vec<u8, N, LenT>) -> Self {
+    pub const unsafe fn from_utf8_unchecked(vec: Vec<u8, N, LenT>) -> Self {
         Self { vec }
     }
 
@@ -1116,6 +1116,13 @@ mod tests {
         static mut _S: String<8> = String::new();
     }
 
+    #[test]
+    fn static_from_utf8_unchecked() {
+        // SAFETY: `b"abcd"` is valid UTF-8.
+        static S: String<8> = unsafe { String::from_utf8_unchecked(Vec::from_array(*b"abcd")) };
+        assert_eq!(S, "abcd");
+    }
+
     #[test]
     fn clone() {
         let s1: String<20> = String::try_from("abcd").unwrap();