September 22
Hi all,
```
  auto foo(const int[3] x)
  {
      int[3] y = x;
      y[0] = 1; // line 4
      return y;
  }
  immutable int[3] a = [0,1,2];
  immutable int[3] b = foo(a); // line 8
```
compiles with an error:
```
4: Error: cannot modify read-only constant [0, 1, 2]
8:        called from here: foo(a)
```

What am I doing wrong?

Thanks,
  Johan

September 23
On Friday, 22 September 2017 at 14:43:28 UTC, Johan wrote:
> Hi all,
> ```
>   auto foo(const int[3] x)
>   {
>       int[3] y = x;
>       y[0] = 1; // line 4
>       return y;
>   }
>   immutable int[3] a = [0,1,2];
>   immutable int[3] b = foo(a); // line 8
> ```
> compiles with an error:
> ```
> 4: Error: cannot modify read-only constant [0, 1, 2]
> 8:        called from here: foo(a)
> ```
>
> What am I doing wrong?
>
> Thanks,
>   Johan

Looks like a compiler bug to me. Please file a bug report on https://issues.dlang.org/enter_bug.cgi