immutable int n = Test(); int[n] x;---- compiles, but __ctfe is false. How?

[anonymous]

On Friday, 21 February 2014 at 13:38:58 UTC, Gopan wrote:
> Attempting to learn CTFE, I tried the following test.
>
> size_t counter;
>
> uint Test()
> {
> 	if (!__ctfe)
> 	{
> 		++counter;// This code is for execution at run time
> 	}
> 	return 2;
> }
>
> void main()
> {
> 	writeln("counter = ", counter);
> 	
> 	immutable int n = Test();

As this is a local variable, this is a runtime initialization, no
__ctfe here. Doesn't matter that it's immutable. It's
static/global vs local. So, this correctly does ++counter.

Make it static immutable n, and counter won't be incremented.

> 	int[n] arr;

Not sure if this should compile. n is a run-time value. It just
happens that it can be CTFE'd. A more problematic case:
---
void main()
{
	immutable n = __ctfe ? 1 : 2;
	int[n] a;
	assert(a.length == n); // fails, wat
}
---

> 	writeln("arrary length = ", arr.length, " ; counter = ", 
> counter);
> }
>
> output:
> counter = 0
> arrary length = 2 ; counter = 1
>
> For array declaration to be successful, its size has to be 
> known at compile time.  The above code compiles too.  But 
> __ctfe seems to be false while performing Test().
>
> Instead, if I write
> 	int[Test()] c;
> 	writeln("c.length = ", c.length, " ; counter = ", counter);
> output is
> counter = 0
> c.length = 2 ; counter = 0
>
> What is wrong in my mind?
>
> Thanks,
> Gopan