Add an lvalue overload for opCmp

Author: Geod24

source/geod24/bitblob.d

@@ -234,6 +234,7 @@ public struct BitBlob (size_t Bits)
         assert(0, "Unexpected char in string passed to BitBlob");
     }
 
+    /// Support for comparison
     public int opCmp (ref const typeof(this) s) const
     {
         // Reverse because little endian
@@ -242,6 +243,12 @@ public struct BitBlob (size_t Bits)
                 return b - s.data[idx];
         return 0;
     }
+
+    /// Support for comparison (rvalue overload)
+    public int opCmp (const typeof(this) s) const
+    {
+        return this.opCmp(s);
+    }
 }
 
 pure @safe nothrow @nogc unittest
@@ -359,6 +366,17 @@ unittest
     static assert(CTFEability[] == GenesisBlockHash);
 }
 
+// Support for rvalue opCmp
+unittest
+{
+    alias Hash = BitBlob!(256);
+    import std.algorithm.sorting : sort;
+
+    static Hash getLValue(int) { return Hash.init; }
+    int[] array = [1, 2];
+    array.sort!((a, b) => getLValue(a) < getLValue(b));
+}
+
 version (unittest)
 {
 private: