fix lints in fish

fish/src/bot.rs

@@ -210,8 +210,8 @@ impl SegmentedAStar {
         trans: &mut TransTable,
         eval: &Evaluator,
     ) -> Result<u32, Option<&'a Node>> {
-        let open_set = self.open.get_mut(self.depth);
-        let cand = open_set.map_or(None, |set| set.pop()).ok_or(None)?;
+        let open_set = self.open.get_mut(self.depth).ok_or(None)?;
+        let cand = open_set.pop().ok_or(None)?;
         let cand = unsafe { cand.0.as_node() };
 
         if cand.is_terminal() {
@@ -230,9 +230,8 @@ impl SegmentedAStar {
             eval.evaluate(mat, queue)
         };
 
-        for suc in cand.expand(arena, trans, evaluate) {
-            self.open[self.depth].push(suc.into());
-        }
+        let expanded = cand.expand(arena, trans, evaluate);
+        self.open[self.depth].extend(expanded.map(AStarNode::from));
 
         Ok(work)
     }

fish/src/bot/node.rs

@@ -27,7 +27,7 @@ fn copy_matrix<'a>(arena: &'a Arena, matrix: &Mat) -> &'a Mat {
 fn copy_queue<'a>(arena: &'a Arena, queue: Queue<'_>) -> Queue<'a> {
     Queue {
         hold: queue.hold,
-        next: arena.alloc_slice_copy(&queue.next),
+        next: arena.alloc_slice_copy(queue.next),
     }
 }
 

fish/src/eval/downstacking.rs

@@ -1,5 +1,6 @@
 #![allow(dead_code)]
 
+use core::mem::replace;
 use core::ops::Range;
 use mino::matrix::{EMPTY_ROW, FULL_ROW};
 use mino::{Mat, MatBuf};
@@ -125,18 +126,17 @@ fn flood_fill(rows: &mut [u16]) -> Option<(i16, i16, u32)> {
         (lx, rx)
     }
 
-    // list the new columns that should be passed on the stack for the given row and range
+    // list the new columns that should be pushed on the stack for the given row and range
     fn scan(row: u16, lx: i16, rx: i16) -> impl Iterator<Item = i16> {
-        let mut added = false;
-        (lx..rx).filter_map(move |x| {
+        let mut allowed = true;
+        (lx..rx).filter(move |x| {
             if row & (1 << x) != 0 {
-                added = false;
-                None
-            } else if added {
-                None
+                // don't push this column since it is occupied, but push the next
+                // unoccupied column encountered
+                allowed = true;
+                false
             } else {
-                added = true;
-                Some(x)
+                replace(&mut allowed, false)
             }
         })
     }