#13251: Must perform family consistency check on non-imported identifiers -------------------------------------+------------------------------------- Reporter: ezyang | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.1 checker) | Resolution: | Keywords: TypeFamilies Operating System: Unknown/Multiple | Architecture: Type of failure: GHC accepts | Unknown/Multiple invalid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by rwbarton): GHCi lets you use a fully-qualified name to refer to an identifier without importing it (similar to TH), so I suppose we ought to treat a module used in this way as an instance provider, as well. Example from slyfox, involving an orphan instance. {{{ ghci -ignore-package=regex-tdfa-rc GHCi, version 8.0.2: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/slyfox/.ghci Prelude C TP CM> "a" Text.Regex.TDFA.=~ "^(a)|(a)$" ::[[ String ]] <interactive>:1:1: error: • No instance for (Text.Regex.Base.RegexLike.RegexMaker Text.Regex.TDFA.Common.Regex Text.Regex.TDFA.Common.CompOption Text.Regex.TDFA.Common.ExecOption [Char]) arising from a use of ‘Text.Regex.TDFA.=~’ • In the expression: "a" Text.Regex.TDFA.=~ "^(a)|(a)$" :: [[String]] In an equation for ‘it’: it = "a" Text.Regex.TDFA.=~ "^(a)|(a)$" :: [[String]] Prelude C TP CM> :m Text.Regex.TDFA Prelude Text.Regex.TDFA> "a" Text.Regex.TDFA.=~ "^(a)|(a)$" ::[[ String ]] [["a","a",""]] }}} (Actually, we could in principle decide freely whether or not to provide the instances here in the sense of making them visible; but we definitely have to do the family instance consistency checks.) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13251#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler