#15316: Regarding coherence and implication loops in presence of QuantifiedConstraints -------------------------------------+------------------------------------- Reporter: mniip | Owner: (none) Type: bug | Status: merge Priority: high | Milestone: 8.6.1 Component: Compiler (Type | Version: 8.5 checker) | Keywords: Resolution: | QuantifiedConstraints Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: GHC accepts | Test Case: quantified- invalid program | constraints/T15316 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by mniip): Replying to [comment:9 simonpj]:
OK, so now you need `UndecidableInstances` to have bad quantified constraints, just as the original proposal said.
Doesn't `UndecidableInstances` imply the typechecking might not terminate, as opposed to a finite typechecking process resulting in a program nonterminating due to poor case of context elaboration? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15316#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler