[board] Add a piece! macro

This macro implements a tiny DSL for creating Pieces and PlacedPieces.

"White King" → Piece::new(Color::White, Shape::King)
"White King on E4" → PlacedPiece::new(Piece::new(Color::White, Shape::King), Square::E4)

board/src/lib.rs

@@ -2,6 +2,7 @@
 
 mod bitboard;
 mod moves;
+#[macro_use]
 pub mod piece;
 pub mod position;
 mod square;

board/src/piece.rs

@@ -118,6 +118,16 @@ pub enum PiecePlacementError {
     ExistsOnSquare,
 }
 
+#[macro_export]
+macro_rules! piece {
+    ($color:ident $shape:ident) => {
+        Piece::new(Color::$color, Shape::$shape)
+    };
+    ($color:ident $shape:ident on $square:ident) => {
+        PlacedPiece::new(piece!($color $shape), Square::$square)
+    }
+}
+
 #[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
 pub struct Piece {
     color: Color,