const Propagation

[Julian Kranz via Digitalmars-d]

Thank you for your answers. All of your suggestions go into the 
right direction, however there's still one thing left that 
breakes it: the method itself (blah()) needs to be marked as 
const to be callable on a const object. Therefore, I need 
something like

void blah(...)(...) if(this ia const object) const : nothing {
}

I would also like to discuss the underlying problem. Even if we 
end up finding some syntactic monster to deal with this, there 
obviously is no sneaky syntax for it. Am I wrong thinking that is 
some very basic type checking problem? I mean, D already 
implements const transitively. Thus, if I cast some object to its 
const version, all its members magically turn to be const as 
well. Wouldn't it be natural to apply this here as well? This 
way, I would not even need to declare the lambda's parameter as 
const or anything; the compiler would only fail if I actually 
pass in something of which the compiler is unsure whether it 
changes the passed-in object or not...