[zozbot234]

I think the "no closure to allocate" is not quite right because the captured parameters of a first-class function still need to be stored somewhere. It just happens as part of the calling code, e.g. consider how a "function object" in C++/Java works: the operator() or .call() code does not need to allocate anything, but the allocation might occur as part of constructing the object itself.

[mrkeen]

Once they've been converted from free variables to formal parameters then it's assumed you can just stack allocate them, and roll them off when you return from your lambda (which is no longer a closure)