#6065: Suggested type signature causes a type error (even though it appears
correct)
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Reporter: tvynr | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler (Type
checker)
Version: 7.4.1 | Keywords: type signature
typeclass instance forall
Os: Linux | Architecture: x86_64 (amd64)
Failure: GHC rejects valid program | Testcase:
Blockedby: | Blocking:
Related: |
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Comment(by guest):
I reduced your test case. The following file compiles, but if inferred
type signature to "upcast" is added, it doesn't.
{{{
{-# LANGUAGE MultiParamTypeClasses, FlexibleContexts, FlexibleInstances
#-}
class AstOp ast result where
astop :: ast -> result
-- upcast :: AstOp ast ((ast -> t) -> t) => ast -> t
upcast ast = astop ast upcast
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6065#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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