What guarantees does D 'const' provide, compared to C++?

[Peter Alexander]

On Sunday, 19 August 2012 at 19:26:58 UTC, Jesse Phillips wrote:
> On Saturday, 18 August 2012 at 11:26:01 UTC, Peter Alexander 
> wrote:
>
>> const on its own provides no guarantees, it just imposes 
>> restrictions so that immutable can provide guarantees.
>
> While in context with the original question this is fine, but I 
> do not like this use of guarantee.
>
> What I mean is, const does provide guarantees by itself. And it 
> provides more than C++ because it is transitive and modifying a 
> const reference is undefined.

What guarantees does const provide on its own?