[GHC] #8159: Uses of Binary decode should have a proper error message

[GHC]

#8159: Uses of Binary decode should have a proper error message
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       Reporter:  nh2                      |             Owner:
           Type:  bug                      |            Status:  new
       Priority:  low                      |         Milestone:
      Component:  Compiler                 |           Version:  7.6.3
       Keywords:                           |  Operating System:
   Architecture:  Unknown/Multiple         |  Unknown/Multiple
     Difficulty:  Easy (less than 1 hour)  |   Type of failure:
     Blocked By:                           |  None/Unknown
Related Tickets:                           |         Test Case:
                                           |          Blocking:
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 In #8144 I changed the interface file format.

 That can happen without you noticing because it just uses the Binary
 instance.

 To deserialize it, we also use Binary. When that fails, the error message
 is

 {{{
 Binary.get(Usage): 50
 }}}

 The error message should at least also mention:
 {{{
 Reading the interface file failed
 }}}

 This is not a specific problem with interface files (it is actually a
 minor problem there since ghc will refrain from reading .hi files created
 by an older version), but it is in development, and independent from that,
 all uses of Binary decode should be guarded as it is a very partial
 function.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8159>
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