[GHC] #7631: Allow to differentiate between newtypes and datatypes

[GHC]

#7631: Allow to differentiate between newtypes and datatypes
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Reporter:  Feuerbach         |          Owner:                   
    Type:  feature request   |         Status:  new              
Priority:  normal            |      Component:  libraries (other)
 Version:  7.6.1             |       Keywords:  generics         
      Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple 
 Failure:  None/Unknown      |      Blockedby:                   
Blocking:                    |        Related:                   
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 When writing a generic instance, I would like to be able to tell whether
 the type under consideration has been declared using newtype or data.

 For example, in SmallCheck we generate values of certain "depth". It is
 natural to treat datatype constructors as increasing the depth of the
 constructed value, and newtype constructors as preserving the depth.

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7631>
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