From 2ef316ab524ddcde970909dafa070076f68de71a Mon Sep 17 00:00:00 2001
From: Simon Gardling <titaniumtown@proton.me>
Date: Tue, 18 Feb 2025 23:44:56 -0500
Subject: [PATCH] const_fn bitvec + bitvec build fixes

---
 Cargo.lock      |  7 +++++++
 Cargo.toml      |  1 +
 src/bitboard.rs |  9 +++++++--
 src/board.rs    | 21 +++++++++++++++++----
 4 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 776e2ed..0801c46 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -142,6 +142,12 @@ dependencies = [
  "windows-sys",
 ]
 
+[[package]]
+name = "const_fn"
+version = "0.4.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2f8a2ca5ac02d09563609681103aada9e1777d54fc57a5acd7a41404f9c93b6e"
+
 [[package]]
 name = "criterion"
 version = "0.5.1"
@@ -425,6 +431,7 @@ version = "0.1.0"
 dependencies = [
  "arrayvec",
  "bitvec",
+ "const_fn",
  "criterion",
  "either",
  "indicatif",
diff --git a/Cargo.toml b/Cargo.toml
index cc035f9..2b0e35e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -31,6 +31,7 @@ bitvec = [ "dep:bitvec" ]
 [dependencies]
 arrayvec = "0.7"
 bitvec = { version = "1", optional = true }
+const_fn = "0.4.11"
 either = "1.13"
 indicatif = "0.17"
 lazy_static = "1.5"
diff --git a/src/bitboard.rs b/src/bitboard.rs
index 5cb3676..af75efb 100644
--- a/src/bitboard.rs
+++ b/src/bitboard.rs
@@ -1,4 +1,5 @@
 use crate::board::{BOARD_AREA, BOARD_SIZE};
+use const_fn::const_fn;
 use static_assertions::const_assert;
 
 // quick explanation for the dual-nature of [`BitBoard`]
@@ -11,7 +12,10 @@ use static_assertions::const_assert;
 use bitvec::prelude::*;
 
 #[cfg(feature = "bitvec")]
-pub type BitBoardInner = BitArr!(for BOARD_AREA, in u64, Lsb0);
+type BBBaseType = u64;
+
+#[cfg(feature = "bitvec")]
+pub type BitBoardInner = BitArr!(for BOARD_AREA, in BBBaseType, Lsb0);
 
 #[cfg(not(feature = "bitvec"))]
 pub type BitBoardInner = u64;
@@ -78,7 +82,8 @@ impl BitBoard {
         self.0.set(Self::get_index(row, col), value);
     }
 
-    // works on both `bitvec` and native
+    // works on both `bitvec` and native (const on native)
+    #[const_fn(cfg(not(feature = "bitvec")))]
     pub fn count(&self) -> usize {
         self.0.count_ones() as usize
     }
diff --git a/src/board.rs b/src/board.rs
index c78a554..a9d630e 100644
--- a/src/board.rs
+++ b/src/board.rs
@@ -4,8 +4,9 @@ use crate::{
     piece::Piece,
 };
 use arrayvec::ArrayVec;
+use const_fn::const_fn;
 use lazy_static::lazy_static;
-use std::{cmp::Ordering, fmt};
+use std::{cmp::Ordering, collections::HashSet, fmt};
 
 /// Size of each dim of the board
 pub const BOARD_SIZE: usize = 8;
@@ -62,6 +63,12 @@ fn gen_adj_lookup() -> PosMap<ChainCollection> {
                         "chains go out-of-bounds"
                     );
 
+                    let mut uniq = HashSet::new();
+                    assert!(
+                        chains.iter().flatten().all(move |x| uniq.insert(x)),
+                        "there are duplicate nodes in chain"
+                    );
+
                     chains
                 })
                 .collect()
@@ -191,11 +198,13 @@ impl Board {
         }
     }
 
-    pub fn get_piece(&self, i: usize, j: usize, color: Piece) -> bool {
+    #[const_fn(cfg(not(feature = "bitvec")))]
+    pub const fn get_piece(&self, i: usize, j: usize, color: Piece) -> bool {
         self.board(color).get(i, j)
     }
 
     /// Returns the color of a place on the [`Board`] at a position
+    #[const_fn(cfg(not(feature = "bitvec")))]
     pub fn get(&self, i: usize, j: usize) -> Option<Piece> {
         if self.get_piece(i, j, Piece::White) {
             Some(Piece::White)
@@ -207,11 +216,13 @@ impl Board {
     }
 
     /// Place a piece without checking for propegation of validity
+    #[const_fn(cfg(not(feature = "bitvec")))]
     fn place_unchecked(&mut self, i: usize, j: usize, piece: Piece) {
         self.board_mut(piece).set(i, j, true);
-        self.board_mut(!piece).set(i, j, false);
+        self.board_mut(piece.flip()).set(i, j, false);
     }
 
+    #[const_fn(cfg(not(feature = "bitvec")))]
     fn delete(&mut self, i: usize, j: usize) {
         self.board_mut(Piece::White).set(i, j, false);
         self.board_mut(Piece::Black).set(i, j, false);
@@ -300,14 +311,16 @@ impl Board {
     }
 
     /// Count the number of a type of [`Piece`] on the board
+    #[const_fn(cfg(not(feature = "bitvec")))]
     pub fn count(&self, piece: Piece) -> usize {
         self.board(piece).count()
     }
 
     /// Get the "net score" of a player
     /// Formula: `net_score = Score_player - Score_opponent`
+    #[const_fn(cfg(not(feature = "bitvec")))]
     pub fn net_score(&self, piece: Piece) -> isize {
-        self.count(piece) as isize - self.count(!piece) as isize
+        self.count(piece) as isize - self.count(piece.flip()) as isize
     }
 
     /// Returns the winner of the board (if any)