fix shadow play: only use ahead extension set per direction

src/movegen-test-baseline.txt

@@ -191,32 +191,32 @@
   13.0460 9B ROTOR 13
 === Case 11: rack=ST fen=ZONULE1B2APAID/1KY2RHANJA4/GAM4R2HUI2/7G6D/6FECIT3O/6AE1TOWIES/6I7E/1EnGUARD6D/NAOI2W8/6AT7/5PYE7/5L1L7/2COVE1L7/5X1E7/7N7 ===
   18.1100 11F (PYE)T 9
-  14.1100 B8 (EA)T 5
   14.1100 6F T(AE) 5
+  14.1100 B8 (EA)T 5
   14.0000 I10 ST 14
-  13.1100 7N T(E) 4
+  13.1100 7F T(I) 4
   13.1100 L3 (U)T 4
-  13.1100 5N T(O) 4
-  13.1100 D12 T(O) 4
+  13.1100 7N T(E) 4
   13.1100 N1 (I)T 4
+  13.1100 D12 T(O) 4
   13.1100 D8 (GI)T 4
-  13.1100 7F T(I) 4
+  13.1100 5N T(O) 4
   13.0000 N1 (I)TS 13
   12.1100 K5 (TO)T 3
   12.1100 B7 T(EA) 3
-  12.1100 M6 (I)T 3
+  12.1100 10G (AT)T 3
 === Case 12: rack=OO fen=ZONULE1B2APAID/1KY2RHANJA4/GAM4R2HUI2/7G6D/6FECIT3O/6AE1TOWIES/6I7E/1EnGUARD6D/NAOI2W8/6AT7/5PYE7/5L1L7/2COVE1L7/5X1E7/7N7 ===
-  11.0000 2N OO 11
   11.0000 7L OO 11
+  11.0000 2N OO 11
   10.0000 7K OO 10
   8.0000 I12 OO 8
   8.0000 10C OO 8
   7.0000 L6 (W)OO 7
   6.5220 3G O(R) 9
   6.0000 10D OO 6
-  5.0000 N8 OO 5
-  5.0000 C13 (C)OO 5
   5.0000 A3 (G)OO 5
+  5.0000 C13 (C)OO 5
+  5.0000 N8 OO 5
   4.0000 13H (L)OO 4
   3.5220 1H (B)O 6
   3.0000 A9 (N)OO 3
@@ -230,9 +230,9 @@
   7.0000 L6 (W)OO 7
   6.5220 3G O(R) 9
   6.0000 10D OO 6
+  5.0000 A3 (G)OO 5
   5.0000 N8 OO 5
   5.0000 C13 (C)OO 5
-  5.0000 A3 (G)OO 5
   4.0000 13H (L)OO 4
   3.5220 1H (B)O 6
   3.0000 15H (N)OO 3
@@ -247,31 +247,31 @@
   1.5220 N1 (I)O 4
   0.5220 O1 (D)O 3
   0.5220 M6 (I)O 3
-  0.5220 13H (L)O 3
-  0.5220 8N O(D) 3
   0.5220 C7 O(nO) 3
+  0.5220 8N O(D) 3
+  0.5220 13H (L)O 3
   0.5220 K5 (TO)O 3
   0.5220 4N O(D) 3
   0.0000 Exch. OO
   -0.4780 15G O(N) 2
   -0.4780 12H (L)O 2
   -0.4780 15H (N)O 2
-  -0.4780 M3 (I)O 2
+  -0.4780 M5 O(I) 2
   -0.4780 D13 (O)O 2
-  -0.4780 C8 (nO)O 2
+  -0.4780 M3 (I)O 2
   -0.4780 A9 (N)O 2
   -0.4780 E7 O(U) 2
-  -0.4780 M5 O(I) 2
+  -0.4780 C8 (nO)O 2
   -2.4780 Exch. O
   -9.6960 Pass
 === Case 14: rack=VUAENRU fen=5MOZ6S/2FIREPOTS4p/2Y2UTA1HWAN1E/DAK8L2C/OWE1BIB4E2I/CADGE6U1PA/I4DOGY2R1aT/L2GLORIA1LOVIE/E1XI1TAED2N1N1/RAI8S1T1/13I1/13E1/13R1/15/15 ===
-  17.4770 M13 UVA 16
   17.4770 12L UV(E)A 16
+  17.4770 M13 UVA 16
   16.8870 12H UNREAV(E) 22
-  15.4770 5I UVA(E) 14
-  15.4770 K10 UVA 14
   15.4770 5J UV(E)A 14
+  15.4770 K10 UVA 14
   15.4770 12K UVA(E) 14
+  15.4770 5I UVA(E) 14
   14.4390 12I AVENU(E) 18
   12.8570 K10 URVA 16
   12.4770 1L VAU(S) 11

src/movegen.rs

@@ -1240,10 +1240,8 @@ fn gen_place_placements<'a, PossibleStripPlacementCallbackType: FnMut(i8, i8, i8
             } else if this_cross_bits != 1 {
                 // something hooks here and there is a valid letter.
                 // this_cross_bits has bit 1 set, so blank is always allowed.
-                let matching_bits = this_cross_bits
-                    & rack_bits
-                    & env.params.left_extension_strip[idx as usize]
-                    & env.params.right_extension_strip[idx as usize];
+                let matching_bits =
+                    this_cross_bits & rack_bits & env.params.left_extension_strip[idx as usize];
                 if matching_bits == 0 {
                     break;
                 }
@@ -1348,10 +1346,8 @@ fn gen_place_placements<'a, PossibleStripPlacementCallbackType: FnMut(i8, i8, i8
             } else if this_cross_bits != 1 {
                 // something hooks here and there is a valid letter.
                 // this_cross_bits has bit 1 set, so blank is always allowed.
-                let matching_bits = this_cross_bits
-                    & rack_bits
-                    & env.params.left_extension_strip[idx as usize]
-                    & env.params.right_extension_strip[idx as usize];
+                let matching_bits =
+                    this_cross_bits & rack_bits & env.params.right_extension_strip[idx as usize];
                 if matching_bits == 0 {
                     break;
                 }