lambdas and function literals in classes

[John Colvin]

JS asked about this in the main group, but here is more 
appropriate and I'm quite interested myself.

Can someone explain the rationale behind this:

class A
{
     auto a = (){}; 		//Lambda not allowed
     auto b = function(){};	//Function allowed
     auto c = delegate(){};	//Delegate not allowed
}

A guess:

Delegate's aren't allowed as members due their context pointer 
(why???), lambdas are assumed to be delegates unless they are 
proved to not need context (and dmd is sucking at proving that).