#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: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: 13122 Related Tickets: | Differential Rev(s): #8809,#10073,#10179,#12906 | Wiki Page: | -------------------------------------+------------------------------------- Comment (by Rufflewind): TBH, I think `SDoc` is too low level to embed rich semantic information like expressions, locations etc. It should stick to what it does best: laying out dumb text data. Instead, I think it'd be nicer to have a simple high-level data type for diagnostics, which could look like: {{{#!hs data Error = Error Severity (Maybe ErrorID) ErrorMessage [(Location, Maybe Expression)] type ErrorID = String -- i.e. flag that disables the warning -- it'd be nice to have them for errors too type ErrorMessage = [ErrMsgSegment] data ErrMsgSegment = EDoc SDoc | ELink Int -- link to some expression of interest }}} … something along those lines. There's plenty of room to bikeshed on the details, but it'd be great to keep it as simple as possible so as to minimize the effort required by downstream to interpret the diagnostics. In contrast, an `SDoc` does not give the consumer a lot of flexibility in the display of an error. This approach allows for a gradual transition: simply edit the legacy error-emitting framework to emit an `Error severity Nothing (EDoc msg) [(loc, Nothing)]`, which is the kind of “dumb” error that we have today. To take advantage of the new system, we just bypass the legacy framework and create `Error`s directly. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8809#comment:52 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler