[GHC] #10040: Add hint on typed-hole error message

[GHC]

#10040: Add hint on typed-hole error message
-------------------------------------+-------------------------------------
              Reporter:  simonpj     |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.8.4
              Keywords:              |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  None/Unknown
  Unknown/Multiple                   |        Blocked By:
             Test Case:              |   Related Tickets:
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------
 If you write
 {{{
 f flag = _flag + 4
 }}}
 it's possible that you didn't intend a typed hole; you just mis-typed
 `_flag`.  So I propose to add hint to the error message saying that
 {{{
     Found hole ‘_flag’ with type: t
     Where: ...blah blah...
     Or perhaps ‘_flag’ is mis-spelled, or not in scope
     Relevant bindings include it :: t (bound at <interactive>:9:1)
 }}}
 The third line is the new one.

 See [https://www.haskell.org/pipermail/glasgow-haskell-
 users/2015-January/025599.html this email trail].

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10040>
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