#2361: ghci cannot :print certain functions
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Reporter: guest | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: GHCi | Version: 6.8.2
Severity: normal | Resolution:
Keywords: ghci, print, sprint | Testcase: :print truncate
Architecture: x86 | Os: Linux
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Comment (by ajd):
I've done a bit of testing, and it seems like this bites when :print-ing a
class function with a type that includes type variables not mentioned in
the class heading.
{{{
{-# LANGUAGE MultiParamTypeClasses #-}
class Bar a where
-- This is fine
bar :: a -> a
class Foo a where
-- All of these trigger the bug:
baz :: Bar b => a -> b
foo :: Bar b => a -> b -> a
faz :: Bar b => a -> b -> Int
bom :: Bar b => b -> a -> b
wow :: a -> b
doh :: b -> a
uhh :: a -> b -> a -> b -> a -> b -> a
oos :: a -> a -> a -> b -> a
-- But this doesn't:
cod :: a -> a
class Multi a b where
-- These two are OK
oks :: a -> b
sko :: b -> a
-- These trigger the bug:
dom :: a -> c
piz :: b -> c
coz :: a -> c -> b
-- Both of these functions are fine
fazola :: (Foo a, Bar b) => a -> b -> a
fazola = undefined
faz' :: (Foo a, Bar b) => a -> b -> Int
faz' = faz
}}}
Note also that a function defined as equal to a class function works fine.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2361#comment:1>
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