DMD 2.057:

import std.stdio;
inout(int)** qux(inout(int) p, inout(int)** pp){
    return pp;
}
void main(){
    immutable(int) x;
    immutable(int)* y = &x;
    int z;
    *qux(1,&y)=&z; // BOOM.

    writeln(is(typeof(&z)==int*)            &&
            is(typeof( y)==immutable(int)*) &&
            &z is y); // "true"                                                 
}

The code exploits the fact that inout matching does not check sanity, in order to perform the forbidden immutable(int)** => const(int)** conversion. The code could be slightly modified such that it performs an int** => const(int)** conversion instead.

(Ideally, inout would be deduced as immutable in this specific example and the assignment would cause an error.)