Why do not all Syntax elements have a SrcLoc?

[Reto Kramer]

Is there a particular reason why only "top level" AST elements in the 
Language.Haskell.Syntax libarary have a SrcLoc attribute?

It would be very handy for my application to be able to know the src 
location of each AST element and I was wondering if there was a deeper 
reason why that's not the case.

Also I wonder if other would be interested in an extension that 
captured the start (line,column) as well as the end (line column) of 
AST elements (handy for rendering src).

- Reto