WIP

core/src/coordinates.rs

@@ -217,6 +217,43 @@ coordinate_enum!(Square, [
     A8, B8, C8, D8, E8, F8, G8, H8
 ]);
 
+/// Generate an enum that maps its values to variants of [Square].
+macro_rules! to_square_enum {
+    ($vis:vis $name:ident { $($variant:ident)* }) => {
+        #[repr(u8)]
+        #[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
+        $vis enum $name {
+            $($variant = Square::$variant as u8,)*
+        }
+
+        impl From<$name> for Square {
+            fn from(value: $name) -> Self {
+                unsafe { Square::from_index_unchecked(value as u8) }
+            }
+        }
+    };
+}
+
+to_square_enum!(
+    pub EnPassantTargetSquare {
+        A3 B3 C3 D3 E3 F3 G3 H3
+        A6 B6 C6 D6 E6 F6 G6 H6
+    }
+);
+
+// impl TryFrom<Square> for EnPassantTargetSquare {
+//     type Error = ();
+
+//     fn try_from(value: Square) -> Result<Self, Self::Error> {
+//         let square = Self::ALL[value as usize];
+//         if square as usize == value as usize {
+//             Ok(square)
+//         } else {
+//             Err(())
+//         }
+//     }
+// }
+
 impl Square {
     /// # Safety
     ///
@@ -240,20 +277,24 @@ impl Square {
         s.parse()
     }
 
+    #[must_use]
     #[inline]
     pub fn file(self) -> File {
         unsafe { File::new_unchecked((self as u8) & 0b000_00111) }
     }
 
+    #[must_use]
     #[inline]
     pub fn rank(self) -> Rank {
         unsafe { Rank::new_unchecked((self as u8) >> 3) }
     }
 
+    #[must_use]
     pub fn file_rank(&self) -> (File, Rank) {
         (self.file(), self.rank())
     }
 
+    #[must_use]
     pub fn neighbor(self, direction: Direction) -> Option<Square> {
         let index: u8 = self as u8;
         let dir: i8 = direction.to_offset();
@@ -347,10 +388,9 @@ impl From<File> for char {
     }
 }
 
-impl Into<char> for Rank {
-    fn into(self) -> char {
-        let value: u8 = self.into();
-        (value + b'1') as char
+impl From<Rank> for char {
+    fn from(value: Rank) -> Self {
+        Self::from(value.0)
     }
 }