Add '# Safety' section to 'unsafe fn' doc

src/board/castle_rights.rs

@@ -26,6 +26,10 @@ impl CastleRights {
     }
 
     /// Convert from a castle rights index into a [CastleRights] type, no bounds checking.
+    ///
+    /// # Safety
+    ///
+    /// Should only be called with values that can be output by [CastleRights::index()].
     #[inline(always)]
     pub unsafe fn from_index_unchecked(index: usize) -> Self {
         std::mem::transmute(index as u8)

src/board/color.rs

@@ -20,6 +20,10 @@ impl Color {
     }
 
     /// Convert from a piece index into a [Color] type, no bounds checking.
+    ///
+    /// # Safety
+    ///
+    /// Should only be called with values that can be output by [Color::index()].
     #[inline(always)]
     pub unsafe fn from_index_unchecked(index: usize) -> Self {
         std::mem::transmute(index as u8)

src/board/file.rs

@@ -43,6 +43,10 @@ impl File {
     }
 
     /// Convert from a file index into a [File] type, no bounds checking.
+    ///
+    /// # Safety
+    ///
+    /// Should only be called with values that can be output by [File::index()].
     #[inline(always)]
     pub unsafe fn from_index_unchecked(index: usize) -> Self {
         std::mem::transmute(index as u8)

src/board/piece.rs

@@ -36,6 +36,10 @@ impl Piece {
     }
 
     /// Convert from a piece index into a [Piece] type, no bounds checking.
+    ///
+    /// # Safety
+    ///
+    /// Should only be called with values that can be output by [Piece::index()].
     #[inline(always)]
     pub unsafe fn from_index_unchecked(index: usize) -> Self {
         std::mem::transmute(index as u8)

src/board/rank.rs

@@ -43,6 +43,10 @@ impl Rank {
     }
 
     /// Convert from a rank index into a [Rank] type, no bounds checking.
+    ///
+    /// # Safety
+    ///
+    /// Should only be called with values that can be output by [Rank::index()].
     #[inline(always)]
     pub unsafe fn from_index_unchecked(index: usize) -> Self {
         std::mem::transmute(index as u8)

src/board/square.rs

@@ -59,6 +59,10 @@ impl Square {
     }
 
     /// Convert from a square index into a [Square] type, no bounds checking.
+    ///
+    /// # Safety
+    ///
+    /// Should only be called with values that can be output by [Square::index()].
     #[inline(always)]
     pub unsafe fn from_index_unchecked(index: usize) -> Self {
         std::mem::transmute(index as u8)