Safety, undefined behavior, @safe, @trusted

[Steven Schveighoffer]

On Thu, 05 Nov 2009 19:44:55 -0500, Walter Bright  
<newshound1 at digitalmars.com> wrote:

> Steven Schveighoffer wrote:
>> That is, I have a mutable reference x, I want to make it immutable.   
>> How do you write a function to do that?
>>  i.e.:
>>  @safe void foo()
>> {
>>    x = new X();
>>    x.modifyState(5);
>>    immutable(X) ix = ???; // how to write this part
>> }
>
> If you, the writer of foo(), know that there are no other mutable  
> references to x you can cast it to immutable - but you'll have to mark  
> the function as @trusted.

But what if I don't what the whole function to be trusted, just that  
creation section?  I have to create a new function just to create the data?

Maybe function-level granularity isn't good enough...

-Steve