Currently, all parser warnings just get displayed at the top of a page, which makes it very hard for editors to identify the source of them. It would be nice if they could somehow show exactly where they came from. While we were discussing this on IRC, I noticed two potential problems with the placement of the warnings: if they're always placed at top-level, they're useless for very large templates, and if they're always placed at the level where they came from, they could break things like #expr that weren't expecting to see them. To take care of both of these issues, I think stack traces should be associated with the warnings, allowing editors to trace exactly where it came from, without breaking any intermediate templates.