Why are immutable array literals heap allocated?

[ag0aep6g]

On 06.07.19 01:12, Patrick Schluter wrote:
> On Friday, 5 July 2019 at 23:08:04 UTC, Patrick Schluter wrote:
>> On Thursday, 4 July 2019 at 10:56:50 UTC, Nick Treleaven wrote:
>>> immutable(int[]) f() @nogc {
>>>     return [1,2];
>>> }
[...]
> 
> and it cannot optimize it away because it doesn't know what the caller 
> want to do with it. It might in another module invoke it and modify it, 
> the compiler cannot tell. auto a=f(); a[0]++;

f returns immutable. typeof(a) is immutable(int[]). You can't do a[0]++.