#9123: Emit quantified Coercible constraints in GeneralizedNewtypeDeriving -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.8.1 Component: Compiler (Type | Version: 7.8.2 checker) | Keywords: Roles, Resolution: | QuantifiedConstraints Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: quantified- | constraints/T9123{,a} Blocked By: 15290 | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj):
Instead, we could do it in TcDerivInfer by anticipating the need for role-based implication constraint and then providing it.
`TcDerivInfer` works as follows: * Generate constraints * Simplify them * Decide what to quantify over I don't see where in that path we would add "anticipate the need for role- based implication constrains and provide it". Anyway I think we have bigger fish to fry! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9123#comment:67 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler