[Issue 9051] Passing an immutable global with post-blit to a CTFE function

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=9051



--- Comment #2 from Dmitry Olshansky <dmitry.olsh at gmail.com> 2012-11-21 10:49:17 PST ---
(In reply to comment #1)
> The error message is not coming from CTFE. Here's a simple case from a comment
> in the compiler source code (declaration.c):
> 
> /* The problem is the following code:
> *  struct CopyTest {
> *     double x;
> *     this(double a) { x = a * 10.0;}
> *     this(this) { x += 2.0; }
> *  }
> *  const CopyTest z = CopyTest(5.3);  // ok
> *  const CopyTest w = z;              // not ok, postblit not run
> *  static assert(w.x == 55.0);
> * because the postblit doesn't get run on the initialization of w.
> */
> 
> I think that if we didn't call this(this), wrong code would result.

I agree in general. And But given that getMeASet(uint[] arr) is an r-value.
Surely the result of it should be just moved?

The other thought is: can't this(this) be run at compile-time then? What are
limitations?

> There is at least a diagnostic bug here - if it must behave this way, the code
> that creates the comma expression should be issuing the error.
> 
> Interestingly, if you move it inside a function, the result is different:
> 

The same thing happens if you try passing set by reference be it const or
otherwise.

> void foo()
> {
>    pragma(msg, getSecond(set));
> }
> 
> qqq.d(19): Error: static variable set cannot be referenced at compile time
> qqq.d(19):        called from here: __cpcttmp6.__cpctor(set)
> qqq.d(19):        called from here: getSecond((const const(Set) __cpcttmp6 =
> __cpcttmp6.__cpctor(set);
>  , __cpcttmp6))

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