Confusing error message with multiparameter type classes.

The following program

{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE UndecidableInstances #-}

import Data.Typeable

class First a b c | c -> b where
  first :: c -> a -> b

class Second a b where
  second :: a -> b

instance (Typeable b, First a b c) => Second a c where
  second = undefined

main :: IO ()
main = print (second (9 :: Int) :: Int)

produces the following error message

$ runghc-8.0.2 t.hs
t.hs:18:15: error:
    • No instance for (Typeable b0) arising from a use of ‘second’
    • In the first argument of ‘print’, namely
        ‘(second (9 :: Int) :: Int)’
      In the expression: print (second (9 :: Int) :: Int)
      In an equation for ‘main’: main = print (second (9 :: Int) :: Int)

Note that the message does not explain where b0 comes from.

ghc-7.8.3 produced a better error message:

$ runghc-7.8.3 t.hs
t.hs:18:15:
    No instance for (First Int b Int) arising from a use of ‘second’
    In the first argument of ‘print’, namely
      ‘(second (9 :: Int) :: Int)’
    In the expression: print (second (9 :: Int) :: Int)
    In an equation for ‘main’: main = print (second (9 :: Int) :: Int)

Doing slight modifications changes the error message that ghc-8.0.2 shows. e.g.

- instance (Typeable b, First a b c) => Second a c where
+ instance (First a b c, Typeable b) => Second a c where

gives the same error as ghc-7.8.3.

In a big program the current error is very puzzling. Is ghc picking the wrong error to show? Could it print more errors perhaps?