#14961: QuantifiedConstraints: introducing classes through equality constraints fails -------------------------------------+------------------------------------- Reporter: mrkgnao | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.5 Resolution: | Keywords: | QuantifiedConstraints wipT2893 Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: #14860 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): You want GHC to ''infer'' a type with a quantified constraint. In general that is hard, and quite probably not what you wanted, so GHC doesn't even try. In short: no inferred type has a quantified constraint, only declared types. In GHCi, `:type <expression>` infers the type of `<expression>` so you have the same issue. On the other hand `:info <identifier>` will work just fine. Does that make sense? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14961#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler