#13595: Should ‘coerce’ be levity polymorphic? -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: | LevityPolymorphism Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #13592 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): The ability to write `coerceTuple` is an entirely separate matter, IIUC. You're asking for the `Coercible` solver to have extra knowledge about unboxed tuple representations that it's currently not privy to. With levity polymorphic `coerce` you could go from `(# Int #)` to `(# Age #)`, where `Age` is a newtype around `Int`. But you'd need some extra juice to go from `(# Int #)` to, say, `(# Int, (##) #)`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13595#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler