#14247: Fails to coerce between newtypes directly -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs import Data.Coerce import Data.Type.Coercion newtype W a = W a newtype A = MkA (W A) a :: Coercion A A a = Coercion b :: Coercion a a' -> Coercion a (W a') b Coercion = Coercion c :: Coercion A (W A) c = b a }}} works just fine but the following fail: {{{#!hs -- • Couldn't match representation of type ‘A’ with that of ‘W A’ -- arising from a use of ‘Coercion’ -- • In the expression: Coercion -- In an equation for ‘d’: d = Coercion d :: Coercion A (W A) d = Coercion -- • Couldn't match representation of type ‘A’ with that of ‘W A’ -- arising from a use of ‘coerce’ -- • In the expression: coerce -- In an equation for ‘e’: e = coerce e :: A -> W A e = coerce }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14247 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler