Should .idup simply do nothing for arrays that are already immutable?

[dsimcha]

import std.stdio;

void main() {
    immutable foo = "FOO";
    immutable bar = foo.idup;
    writeln(foo.ptr, '\t', bar.ptr);
}

Output:
42C090  97AE40

Should we define .idup on an already-immutable array to simply do nothing?  It
seems that there is never any good reason to copy an immutable array, and it
would avoid the need to either needlessly copy an array or explicitly check
for immutability in metaprogramming situations.