I may have found a bug in assumeUTF(), but being new to D, I'm
not sure.
The description:
Assume the given array of integers arr is a well-formed UTF
string and return it typed as a UTF string.
ubyte becomes char, ushort becomes wchar and uint becomes
dchar. Type qualifiers are preserved.
The declaration:
```d
auto assumeUTF(T)(T[] arr)
if (staticIndexOf!(immutable T, immutable ubyte, immutable
ushort, immutable uint) != -1)
```
Shouldn't that precondition's `immutable T` be simply `T`?
As it stands, I can do this with no complaints from the
compiler...
```d
string test(ubyte[] arr)
{
import std.string;
return arr.assumeUTF;
}
```
...and accidentally end up with a "string" pointing at mutable
data.
Am I missing something?
