From 0582f0ef2bd1032b2c963019f1150b99224b9b3d Mon Sep 17 00:00:00 2001
From: Nick Treleaven <ntrel002@gmail.com>
Date: Sat, 25 Apr 2026 15:31:34 +0100
Subject: [PATCH 1/2] Add const to BitArray opOpAssign!"~" and opBinary!"~"
 parameters

---
 std/bitmanip.d | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/std/bitmanip.d b/std/bitmanip.d
index f8a97dfbf19..e1435064a48 100644
--- a/std/bitmanip.d
+++ b/std/bitmanip.d
@@ -1176,10 +1176,10 @@ public:
     }
 
     /**********************************************
-     * Sets the amount of bits in the `BitArray`.
+     * Sets the number of bits in the `BitArray`.
      * $(RED Warning: increasing length may overwrite bits in
      * the final word of the current underlying data regardless
-     * of whether it is shared between BitArray objects. i.e. D
+     * of whether it is shared between `BitArray` objects. i.e. D
      * dynamic array extension semantics are not followed.)
      */
     @property size_t length(size_t newlen) pure nothrow @system
@@ -2214,7 +2214,7 @@ public:
     /***************************************
      * ditto
      */
-    BitArray opOpAssign(string op)(BitArray b) pure nothrow return scope
+    BitArray opOpAssign(string op)(const BitArray b) pure nothrow return scope
     if (op == "~")
     {
         auto istart = _len;
@@ -2231,7 +2231,7 @@ public:
         bool[] bb = [0,1,0];
 
         auto a = BitArray(ba);
-        auto b = BitArray(bb);
+        const b = BitArray(bb);
         BitArray c;
 
         c = (a ~= b);
@@ -2241,7 +2241,6 @@ public:
         assert(a[2] == 0);
         assert(a[3] == 1);
         assert(a[4] == 0);
-
         assert(c == a);
     }
 
@@ -2273,12 +2272,10 @@ public:
     }
 
     /** ditto */
-    BitArray opBinary(string op)(BitArray b) const pure nothrow
+    BitArray opBinary(string op)(const BitArray b) const pure nothrow
     if (op == "~")
     {
-        BitArray r;
-
-        r = this.dup;
+        BitArray r = this.dup;
         r ~= b;
         return r;
     }
@@ -2289,8 +2286,8 @@ public:
         bool[] ba = [1,0];
         bool[] bb = [0,1,0];
 
-        auto a = BitArray(ba);
-        auto b = BitArray(bb);
+        const a = BitArray(ba);
+        const b = BitArray(bb);
         BitArray c;
 
         c = (a ~ b);

From 37a3c015e000d5e5364cb617ddcfdde7e55c4eb4 Mon Sep 17 00:00:00 2001
From: Nick Treleaven <ntrel002@gmail.com>
Date: Sat, 25 Apr 2026 15:41:51 +0100
Subject: [PATCH 2/2] Add const for opCmp parameter too

---
 std/bitmanip.d | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/std/bitmanip.d b/std/bitmanip.d
index e1435064a48..1c32e6aeb06 100644
--- a/std/bitmanip.d
+++ b/std/bitmanip.d
@@ -1744,7 +1744,7 @@ public:
     /***************************************
      * Supports comparison operators for `BitArray`.
      */
-    int opCmp(BitArray a2) const @nogc pure nothrow
+    int opCmp(const BitArray a2) const @nogc pure nothrow
     {
         const lesser = this.length < a2.length ? &this : &a2;
         immutable fullWords = lesser.fullWords;
@@ -1791,8 +1791,8 @@ public:
         bool[] bf = [1,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1];
         bool[] bg = [1,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0];
 
-        auto a = BitArray(ba);
-        auto b = BitArray(bb);
+        const a = BitArray(ba);
+        const b = BitArray(bb);
         auto c = BitArray(bc);
         auto d = BitArray(bd);
         auto e = BitArray(be);