Fix Issue 21628 - The padding bits of bitfields could be calculated a…

…utomatically

std/bitmanip.d

@@ -161,17 +161,18 @@ private template createStorageAndFields(Ts...)
 {
     enum Name = createStoreName!Ts;
     enum Size = sizeOfBitField!Ts;
-    static if (Size == ubyte.sizeof * 8)
+    static if (Size <= ubyte.sizeof * 8)
         alias StoreType = ubyte;
-    else static if (Size == ushort.sizeof * 8)
+    else static if (Size <= ushort.sizeof * 8)
         alias StoreType = ushort;
-    else static if (Size == uint.sizeof * 8)
+    else static if (Size <= uint.sizeof * 8)
         alias StoreType = uint;
-    else static if (Size == ulong.sizeof * 8)
+    else static if (Size <= ulong.sizeof * 8)
         alias StoreType = ulong;
     else
     {
-        static assert(false, "Field widths must sum to 8, 16, 32, or 64");
+        import std.conv : to;
+        static assert(false, "Sum of field widths must be <= 64, is " ~ to!string(Size));
         alias StoreType = ulong; // just to avoid another error msg
     }
     enum result
@@ -291,18 +292,17 @@ of the bitfields storage.
 }
 
 /**
-The sum of all bit lengths in one $(D_PARAM bitfield) instantiation
-must be exactly 8, 16, 32, or 64. If padding is needed, just allocate
-one bitfield with an empty name.
+In former versions of Phobos the sum of all bit lengths in one
+$(D_PARAM bitfield) instantiation had to be of certain lengths.
+This restriction has been dropped now.
 */
 @safe unittest
 {
     struct A
     {
         mixin(bitfields!(
             bool, "flag1",    1,
-            bool, "flag2",    1,
-            uint, "",         6));
+            bool, "flag2",    1));
     }
 
     A a;