#9580: Possible excessive leniency in interaction between coerce and data families? -------------------------------------+------------------------------------- Reporter: dmcclean | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.8.3 (Type checker) | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by dmcclean): I tried a bunch of variations to see if I could get this to not compile to see what might be causing it. It still works if you move the type synonym definitions of `Mass` and `Quantity` out of `Test` and into `Main` (as long as you move the language extensions too). It still works even if the last type parameter is held polymorphic, as {{{ f :: Num v => v -> Mass v f x = coerce $ 3 * x }}} even when `f` is defined in `Main`. It even still works if the last two parameters are held polymorphic, as {{{ g :: Num v => v -> Quantity d v g x = coerce $ 3 * x }}} even when `g` is defined in `Main`. It also works if you do the same thing but expand the type synonyms manually. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9580#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler