On 12/15/2013 02:20 AM, Jesse Phillips wrote:
On Sunday, 15 December 2013 at 00:36:31 UTC, Timon Gehr wrote:
I cannot cast data from my own storage allocator to immutable because
the behaviour will be undefined.
http://dlang.org/const3.html
Is this a documentation bug? What should be the actual rules?
Casting to immutable is defined, it is modifying the data which is not.
That is to say, by casting to immutable the compiler cannot guarantee no
mutation will occur. I assume you're confusion comes from:
char[] s = ...;
immutable(char)[] p = cast(immutable)s; // undefined behavior
immutable(char)[] p = cast(immutable)s.dup; // ok, unique reference
The docs should probably be cleaned up, but it isn't exactly incorrect,
since a mutable reference exists the compiler can't really define what
behavior will occur if the program is run because it can't guarantee
what behavior exists.
http://en.wikipedia.org/wiki/Humpty_Dumpty#In_Through_the_Looking-Glass
