type of concatenated arrays

[Steven Schveighoffer]

In D 2, What should the return type be of concatenated const arrays?

For example, if I have a const(char)[] array a1, and I want to concatenate 
"\n", I could do:

auto a2 = a1 ~ "\n";

Now, a2 is declared as a const(char)[] array, but I think it should be just 
a char[] array.  Why?  because the concat operator should have made a copy 
of the array with length +1 and added the \n character.  If this is the 
case, I should be able to do whatever I want with the copy.  Why does it 
have to be const?

If I want a mutable copy I am forced to do:

auto a2 = (a1 ~ "\n").dup;

which makes a copy of a temporary copy, or if I want to be more efficient, I 
am forced to do something funky like:

char[] a2 = new char[a1.length + "\n".length];
a2[0..a1.length] = a1[];
a2[length - 1] = '\n';

But now, I think the new operation wastes time initializing the array before 
copying the slice.

thoughts?

-Steve