#12393: Poor error message with equational type constraints ---------------------------------+-------------------------------------- Reporter: laneb | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ---------------------------------+-------------------------------------- Comment (by rwbarton):
Even if that is what's going on, the suggestion to "Use GADTs or TypeFamilies to permit this" is clearly wrong, as I am already using TypeFamilies.
Actually, it's technically not wrong: you don't have TypeFamilies turned on ''in GHCi'' which is where the problematic constraint arose. But I certainly agree that GHC should just give the ambiguous type variable error in preference to the one it gave you, and probably shouldn't bother checking the inferred type of `it` at all. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12393#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler