My problem with const

[Freddy via Digitalmars-d]

I love the way D does transitive const and immutable but i have a 
problem when i use const a struct field.
---
struct MyStruct
{
    int a;
    const int b;
}

struct Range
{
    MyStruct front;
    void popFront()
    {
        front = MyStruct(2, 3);
    }
    enum empty = false;
}
---
This sample doesn't compile.