#9729: GHCi accepts invalid programs when recompiling -------------------------------------+------------------------------------- Reporter: crockeea | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.8.3 Resolution: | Keywords: Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: GHC | Blocked By: accepts invalid program | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by crockeea): By "remove the constraint", I mean comment that single line `Internal (a -> b) ~ (Internal a -> Internal b)` in the constraints for `share`. After the edit, module B is: {{{ #!haskell {-# LANGUAGE GADTs, TypeOperators, FlexibleContexts #-} module B where import Data.Syntactic data Let x where Let :: Let (a :-> (a -> b) :-> Full b) share :: (Let :<: sup, sup ~ Domain b, sup ~ Domain a, --Internal (a -> b) ~ (Internal a -> Internal b), -- remove me Syntactic a, Syntactic b, Syntactic (a -> b), SyntacticN (a -> (a -> b) -> b) (ASTF sup (Internal a) -> ASTF sup (Internal (a -> b)) -> ASTF sup (Internal b))) => a -> (a -> b) -> b share = sugarSym Let }}} The example is as minimal as I could make it. In particular, GHCi *does* detect the change to module B if I do not import BindingT in module A. This supports my hypothesis because the instance is never in scope. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9729#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler