[GHC] #7897: MakeTypeRep fingerprints be proper, robust fingerprints

[GHC]

#7897: MakeTypeRep fingerprints be proper, robust fingerprints
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    Reporter:  simonpj           |       Owner:                  
        Type:  bug               |      Status:  new             
    Priority:  normal            |   Milestone:                  
   Component:  Compiler          |     Version:  7.6.3           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Comment(by dreixel):

 Just to add two comments as to why this might not have a good cost/benefit
 ratio:

 1) The problem is not easily seen in practice. In Cloud Haskell, all nodes
 are supposed to run the same binary (currently, at least). And even in the
 example given, the result is a failed deserialisation (possibly with a
 sensible runtime failure), not a segfault.

 2) This will complicate giving `Typeable` instances for data families.
 Right now, since `Typeable` only depends on the LHS of a data declaration,
 we can give a `Typeable` instance as soon as the family is declared; this
 `Typeable` instance it will work for all data instances, current and
 future. If we have to look at the RHS, though, we will need one separate
 `Typeable` instance per data family instance.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7897#comment:1>
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