ghc/compiler/tests/typecheck/should_fail/Digraph.stderr

   1
   2 Digraph.hs:19: A type signature is more polymorphic than the inferred type
   3                    Some type variables in the inferred type can't be forall'd, namely:
   4                    `v{-a13W-}'
   5                    Possible cause: the RHS mentions something subject to the monomorphism restriction
   6     When checking signature for `reversed_edges'
   7     In an equation for function `stronglyConnComp':
   8         `stronglyConnComp es vs   =   PrelTup.snd
   9                                           (span_tree
  10                                                (new_range
  11                                                     reversed_edges)
  12                                                (PrelBase.[], (PrelBase.[]))
  13                                                (PrelTup.snd
  14                                                     (dfs (new_range
  15                                                               es)
  16                                                          (PrelBase.[], (PrelBase.[]))
  17                                                          vs)))
  18                                   where
  19                                       span_tree
  20                                           r (vs, ns) PrelBase.[]
  21                                                   =   (vs, (ns))
  22                                       span_tree
  23                                           r (vs, ns) (x PrelBase.: xs)
  24                                                   | [x PrelList.elem vs] =
  25                                                       span_tree
  26                                                           r (vs, (ns)) xs
  27                                                   | [PrelBase.otherwise] =
  28                                                       span_tree
  29                                                           r
  30                                                           (vs', ((x PrelBase.: ns') PrelBase.: ns))
  31                                                           xs
  32                                                   where
  33                                                       (vs', ns')
  34                                                           =   dfs r
  35                                                                   (x PrelBase.: vs, (PrelBase.[]))
  36                                                                   (r   x)
  37                                       new_range
  38                                           PrelBase.[] w
  39                                                   =   PrelBase.[]
  40                                       new_range
  41                                           ((x, y) PrelBase.: xys) w
  42                                                   =   if x PrelBase.== w then
  43                                                           (y
  44                                                            PrelBase.: (new_range
  45                                                                            xys w))
  46                                                       else
  47                                                           (new_range
  48                                                                xys w)
  49                                       swap
  50                                           (x, y)  =   (y, (x))
  51                                       reversed_edges ::
  52                                           _forall_ [v] {PrelBase.Eq v} => [Edge v]
  53                                       reversed_edges
  54                                           =   PrelBase.map
  55                                                   swap es'
  56
  57
  58 Compilation had errors