""
, ""In stock, usually dispatched in 1 business day""
, ""

""
, """"
, """"]
avWrong =
responseBuilder
status404
[(""Content-Type"", ""text/html"")]
$ mconcat
$ map copyByteString [""wong!

""] index x = responseBuilder status200 [(""Content-Type"", ""text/html"")] $ mconcat $ map copyByteString [ ""Hello from "" , BU.fromString $ show x , ""!

"" , ""\n"" ] }}} We get {{{""
, ""In stock, usually dispatched in 1 business day""
, ""

""
, """"
, """"]
}}}
compiles happily. I'm using
- bytestring-0.10.6.0
- wai-3.0.4.0
- warp-3.1.8
- http-types-0.8.6
- blaze-builder-0.4.0.1
- utf8-string-1.0.1.1" simone.trubian
11957 DataKinds: lifting constructors whose identifier is a single character Compiler 8.1 normal new 2016-04-19T22:56:03Z 2016-04-20T17:41:47Z "{{{
ghci> data I' = I'
ghci> :kind I'
I' :: *
ghci> :kind 'I'
GHCi, version 8.1.20160725: http://www.haskell.org/ghc/ :? for help > :show bindings > x = () > :show bindings}}}" mniip 12535 Bad error message when unidirectional pattern synonym used in bidirectional pattern synonym Compiler (Type checker) 8.0.1 low new 2016-08-25T07:57:05Z 2016-08-25T07:57:05Z "If I write: {{{ {-# LANGUAGE PatternSynonyms #-} module I where pattern P2 x y <- (x, y) pattern P1 x y = P2 x y }}} I get the error: {{{ ezyang@sabre:~$ ghc-8.0 -c I.hs I.hs:5:18: error: • non-bidirectional pattern synonym ‘P2’ used in an expression • In the expression: P2 x y In an equation for ‘$bP1’: $bP1 x y = P2 x y }}}" ezyang 12616 type synonyms confuse generalized newtype deriving role checking Compiler 8.0.1 low goldfire new 2016-09-24T14:47:56Z 2016-09-26T21:45:24Z "Below is a small Haskell file showing the problem. It defines a simple `MonadTrans` typeclass, but using a type operator `~>`. When using the type operator, GHC complains that generalized newtype deriving gets stuck on a nominal role, but when the type operator is not used then GND works just fine. Perhaps this is just expected behavior with mixing RankNTypes and GND (and roles), but it's rather unfortunate. {{{#!hs {-# LANGUAGE GeneralizedNewtypeDeriving #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE TypeOperators #-} module GND where type m ~> n = forall a. m a -> n a class MonadTrans t where -- > this line works: -- lift :: (Monad m) => m a -> t m a -- > this line doesn't: lift :: (Monad m) => m ~> t m data StateT s m a = StateT { runStateT :: s -> m (a, s) } instance MonadTrans (StateT s) where lift xM = StateT $ \ s -> do { x <- xM ; return (x,s) } newtype OtherStateT s m a = OtherStateT { runOtherStateT :: StateT s m a } deriving (MonadTrans) }}} The error message is: {{{ GND.hs:23:13: error: • Couldn't match representation of type ‘m1 ~> StateT s m1’ with that of ‘m1 a1 -> OtherStateT s m1 a1’ arising from a use of ‘GHC.Prim.coerce’ • In the expression: GHC.Prim.coerce (lift :: (~>) m (StateT s m)) :: forall (m :: TYPE GHC.Types.PtrRepLifted -> TYPE GHC.Types.PtrRepLifted). Monad m => (~>) m (OtherStateT s m) In an equation for ‘lift’: lift = GHC.Prim.coerce (lift :: (~>) m (StateT s m)) :: forall (m :: TYPE GHC.Types.PtrRepLifted -> TYPE GHC.Types.PtrRepLifted). Monad m => (~>) m (OtherStateT s m) When typechecking the code for ‘lift’ in a derived instance for ‘MonadTrans (OtherStateT s)’: To see the code I am typechecking, use -ddump-deriv In the instance declaration for ‘MonadTrans (OtherStateT s)’ • Relevant bindings include lift :: m ~> OtherStateT s m (bound at GND.hs:23:13) }}}" daviddarais 344 arrow notation: incorrect scope of existential dictionaries Compiler (Type checker) 6.4 lowest normal ross new 2005-04-07T20:39:35Z 2016-01-24T18:07:53Z "{{{ ghc-6.4: panic! (the `impossible' happened, GHC version 6.4): cgPanic deref{v a1yz} static binds for: local binds for: SRT labelghc-6.4: panic! (the `impossible' happened, GHC version 6.4): initC: srt Please report it as a compiler bug to glasgow-haskell-bugs@haskell.org, or http://sourceforge.net/projects/ghc/. I've attached a test driver that can reproduce the problem. -- Esa Pulkkinen$trModule :: GHC.Types.Module = _x :: () = _ > class Foo a > :show bindings x :: () = _ class Foo a$tcFoo :: GHC.Types.TyCon = _ $tc'C:Foo :: GHC.Types.TyCon = _ $trModule :: GHC.Types.Module = _