Using inout in delegate

[Steven Schveighoffer]

On Thu, 28 Mar 2013 04:34:36 -0400, Jacob Carlborg <doob at me.com> wrote:

> The following code fails to compile:
>
> void foo (inout int[] arr)
> {
>      auto dg = {
>          foreach (i, e ; arr) {}
>      };
>      dg();
> }
>
> void main ()
> {
>      auto a = [3, 4, 5];
>      foo(a);
> }
>
> Error message:
>
> main.d(9): Error: variable main.foo.__lambda1.__aggr1174 inout variables  
> can only be declared inside inout functions
> main.d(9): Error: variable main.foo.__lambda1.e inout variables can only  
> be declared inside inout functions
>
> If I remove the delegate everything compiles. Am I doing something wrong?
>

Like Timon said, it's a bug in inout design.

I'm not sure what __aggr1174 is, but you can fix the e error by specifying  
the type for e (or specifying it as const).

I'm assuming the issue is that the compiler is trying to generate a struct  
to hold the stack data for foo, and struct members cannot be inout.

It is a difficult problem to solve, because inout has two meanings  
depending on whether it is a parameter/return or a local variable.  At  
some point, we need to address this, because inout has so much potential,  
but suffers from some large deficiencies.

-Steve