#3023: Wrong inferred type shown
-----------------------------+----------------------------------------------
Reporter: guest | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 6.10.1 | Severity: normal
Keywords: | Testcase:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
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When the warning for missing type signatures is turned on the displayed
type is sometimes totally bogus.
{{{
{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies,
UndecidableInstances #-}
module Bug where
class C a b | a -> b, b -> a where
f :: a -> b
instance C Int Bool where
f = undefined
instance (C a c, C b d) => C (a -> b) (c -> d) where
f = undefined
foo :: Int -> Int
foo = undefined
bar = f foo
}}}
GHC says:
{{{
Warning: Definition but no type signature for `bar'
Inferred type: bar :: c -> d
}}}
The type for bar is, of course, Bool->Bool, and nothing else.
-- Lennart
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3023>
GHC <http://www.haskell.org/ghc/>
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