Debugging "missing callgraph edge for call stmt"

[Johannes Pfau]

> 
> It's in a template which is nested in a second function (topNIndex)
> and it accesses a function(indirectLess) nested in that function by
> alias. So isn't that the same as:
> -topNIndex
> ----indirectLess
> ----percolateDown{indirectLess();} <--- nested function
> 
> (we have)
> -topNIndex
> ----indirectLess
> ----BinaryHeap(alias indirectLess)
> --------percolateDown{indirectLess()}; <--- is TREE_PUBLIC
> 

I should add that indirectLess is a real nested function - not static -
so it could access variables defined in topNIndex. This is why I think
percolateDown can't be TREE_PUBLIC: It calls a function which is nested
in another function and can access variables in that function. So
percolateDown can indirectly access topNIndex's variables and is
therefore, as far as I understand, nested.