#8649: Disambiguate Repeated Identifiers for data types in error messages ------------------------------------+------------------------------------- Reporter: agibiansky | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- If, in an interactive context, you redefine a type, but then try to use functions for the previous definition, it will (as expected) give you an error message. The following code would trigger this in an interactive context: {{{ data X = Y Int f (Y i) = i data X = Y Int | Z String f (Y 3) }}} However the error message is not very good: {{{ Couldn't match expected type `:Interactive.X' with actual type `:Interactive.X' }}} This is very uninformative to the user if they do not understand what's going on. The following GHC API code can replicate this: {{{ runDeclsWithLocation "Interactive.hs" 1 "data X = Y Int" runDeclsWithLocation "Asdf.hs" 2 "f (Y i) = i" runDeclsWithLocation "Bloop.hs" 3 "data X = Y Int | Z String" runStmtWithLocation "Test.hs" 4 "f (Y 3)" RunToCompletion }}} Note that varying the location given to `runStmt` and `runDecls` (the string as well as the line number) seems to have no effect upon anything. I started out with just "<interactive>" but varied it to check - no effect on anything as far as I can tell. How can I make this error message more informative? I would ideally like something like {{{ Couldn't match expected type `:Interactive1.X' with actual type `:Interactive5.X' }}} or really anything that caused these types to be visibly different. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8649 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler