#13933: Support Typeable instances for types with coercions -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.3 Keywords: TypeInType, | Operating System: Unknown/Multiple Typeable | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- If I say {{{#!hs {-# LANGUAGE GADTs, TypeApplications, TypeInType #-} module Bug where import Type.Reflection data G a where MkG :: a ~ Bool => G a rep = typeRep @MkG }}} I get {{{ Bug.hs:10:7: error: • No instance for (Typeable <>) arising from a use of ‘typeRep’ • In the expression: typeRep @MkG In an equation for ‘rep’: rep = typeRep @MkG | 10 | rep = typeRep @MkG | }}} First off, the error message is confusing, mentioning the mysterious `<>`. But more importantly, it would be nice if the `Typeable` mechanism supported coercions. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13933 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler