Well, weather it's supposed to or not, it *does* contain the line number information:
<ExprAst lineno="1" col_offset="0">
For your example, the AST for "foo" tells you the offset for foo. If you want to know the offset (well, "offset") for blah, why not look at foo? Currently, the information is just copied from foo to blah.

Anyway, I'd like to get away from this abstract discussion which is not likely to yield a result... is there any reason not to do it like I suggested other than the philosophical "it's wrong"? Or don't you agree that the information given this way would be more useful?

Best regards,
Sven