cannot initialize const arrays with out parameters

[dlangBugzillaToGithub]

Walter Bright (@WalterBright) reported this on 2013-12-14T11:08:45Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=11743

Description

The following shows the problem:
---------------------
struct S {
    const int[] x;
    const int[] y;
    const int   z;

    this(int i) {
        x = null;       // works
        foo(y);         // fails
        bar(z);         // works
    }
}

void foo(out int[] y) { y = null; }

void bar(out int z) { z = 1; }
---------------------

dmd -c foo
foo.d(9): Error: function foo.foo (out int[] y) is not callable using argument types (const(int[]))

[dlangBugzillaToGithub]

k.hara.pg commented on 2013-12-14T22:00:57Z

(In reply to comment #0)
> The following shows the problem:
> ---------------------
> struct S {
>     const int[] x;
>     const int[] y;
>     const int   z;
> 
>     this(int i) {
>         x = null;       // works
>         foo(y);         // fails
>         bar(z);         // works
>     }
> }
> 
> void foo(out int[] y) { y = null; }
> 
> void bar(out int z) { z = 1; }
> ---------------------

I think bar(z); should also be rejected, because it would violate const system.

struct S
{
    immutable int z;

    this(int i)
    {
        bar(z); // works
    }
}

int* g;
void bar(out int z) { z = 1; g = &z; }

void main()
{
    S s = S(1);
    assert(s.z == 1 && is(typeof(s.z) == immutable int));
    *g = 100;
    assert(s.z == 1);   // fails!
}