Does slicing have an effect?

[Max Haughton]

On Tuesday, 21 May 2019 at 20:31:58 UTC, Dennis wrote:
> I was replacing a memcpy with a slice assignment and 
> accidentally used == instead of =.
> Usually the compiler protects me from mistakes like that:
>
> ```
> int[4] a;
> a == a;
> ```
> Error: a == a has no effect
>
> However, because I was using slices it didn't:
> ```
> int[4] a;
> a[] == a[];
> ```
> No errors
>
> Does slicing have an effect I'm not aware of, or is this a bug?

It calls druntime( https://d.godbolt.org/z/3gS3-E ), so 
technically it does have an effect, even if that effect is 
completely unused and therefore optimized away. Whether this 
should be considered an effect or not is up to you