[GHC] #13734: Code requires ScopedTypeVariables, possibly erroneously

[GHC]

#13734: Code requires ScopedTypeVariables, possibly erroneously
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 This looks like expected behavior to me. After all, this won't typecheck
 without `ScopedTypeVariables` either:

 {{{#!hs
 {-# Language ScopedTypeVariables, TypeApplications, InstanceSigs #-}

 import Data.Proxy

 class Sized f where
   size :: proxy f ->  Int

 instance Sized Int where
   size :: proxy Int -> Int
   size _ = 42

 instance (Sized a, Sized b) => Sized (a, b) where
   size :: proxy (a, b) -> Int
   size _ = size (Proxy :: Proxy a) + size (Proxy :: Proxy b)
 }}}

 I don't see why `TypeApplications` would be different in that regard.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13734#comment:1>
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