Destructors, const structs, and opEquals

[Don]

Brad Roberts wrote:
> On 12/13/2010 2:54 PM, Don wrote:
> 
>> I can't really escape the feeling that 'const' guarantees too little.
>> It makes guarantees to the caller, but tells the callee *nothing*.
> 
> As far as I'm concerned, that's exactly what I want const for.  The caller can
> rely on the object not being modified.
> 
> Later,
> Brad

Yes. But the callee wants some guarantees as well. How can we provide them?