As reported by deadalnix:

```d
struct S {
     void delegate() dg;
}

void main() {
     int x = 42;
     immutable S s = { dg: () { x++; } };
     s.dg();

     import std.stdio;
     writeln(x);
}
```

This still compiles and run and mutates a variable through an immutable pointer. This variable could be shared too because immutable is safe to share.

May be related to https://issues.dlang.org/show_bug.cgi?id=16095 and https://issues.dlang.org/show_bug.cgi?id=1983