Breaking the type system needs temporary?

[simendsjo]

I'm calling functions using ParameterTypeTuple. The problem arise when 
the parameters is defined as const/immutable. So I need to break out of 
the type system.
But I cannot seem to do this without using a temporary variable. Am I 
doing something wrong?

    int i = 1;
    const(int*) c;
    //c = &v; // ok - cannot modify const
    int* cp = cast(int*)c;
    cp = &v; // ok - breaking type system
    //(cast(int*)c) = &v; // cannot modify const - shouldn't this work 
as above?