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  • #10177
Closed
Open
Issue created Mar 21, 2015 by glguy@glguy

Typeable solver regression

This bug is known and fixed in master. Simon and Austin and Iavor are all aware of it. This ticket exists to ensure that the fix doesn't get lost.

This code breaks under the Typeable solver in 7.10.1-rc3 and is fixed in master.

The relevant commit in master is 3a0019e3 : Improve Typeable solver.

{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE FlexibleContexts #-}
module Bug where

import Data.Typeable

newtype V n a = V [a]

class    Typeable a                   => C a
instance (Typeable (V n), Typeable a) => C (V n a)

-- Bug.hs:13:10:
--  Could not deduce (Typeable (V n a))
--    arising from the superclasses of an instance declaration
--  from the context (Typeable (V n), Typeable a)
--    bound by the instance declaration at Bug.hs:13:10-50
--  In the instance declaration for ‘C (V n a)’
Trac metadata
Trac field Value
Version 7.10.1-rc3
Type Bug
TypeOfFailure OtherFailure
Priority highest
Resolution Unresolved
Component Compiler (Type checker)
Test case
Differential revisions
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Blocking
CC diatchki
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