#8809: Prettier error messages? -------------------------------------+------------------------------------- Reporter: joelteon | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by goldfire): Replying to [comment:3 bgamari]:
Edsko and I were thinking about this a bit in light of the recent discussion on Reddit. He had what I thought was a rather nice idea: ...
I think the idea of embedding richer info into `SDoc` is a good one. In particular, I like the idea that this enables a gradual transition. For example, we could have some large ADT defined in !TcErrors that represents all of the errors that the module produces (but not other modules). Then some of the downside of the big-ADT approach that Simon is worried about is reduced. And then we could do another module... and so on. However, I think indexing `SDoc` is going to lead to trouble. We won't be able to have lists of errors that originated in disparate parts of the compiler. And we won't be able to embed multiple types of information in the same error message. Instead, what if we just use dynamic typing here? (gasp!) By this, I mean something like {{{ data Doc = forall a. Typeable a => Embed a | Empty | ... }}} When pulling out embedded bits, we just use dynamic checks to get the types. Although this seems somewhat un-Haskellish, I think it's forced by the very-dynamic nature of an error message. During parsing, a consumer can discover what type of embedded information should be at a certain spot, and then do the dynamic check. This seems like just the sort of thing that dynamic typing excels at. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8809#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler