[Haskell-cafe] can the default instances in GHC be recompiled with overlap?

Jason Dusek jason.dusek at gmail.com
Mon Aug 25 15:00:07 EDT 2008

  Per the GHC manual section on instance overlap:

    If an instance declaration is compiled without
    -XOverlappingInstances, then that instance can never be
    overlapped. This could perhaps be inconvenient.

  It is inconvenient for certain things. If I want to declare a
  special `instance Show [MyType] where...` I am out of luck.
  However, the solution need not involve a change to the way
  instances are handled -- if all the `GHC.*` instances were
  compiled with overlapping instances, I'd be able to declare my

  Is there a substantial barrier, either theoretical or
  practical, to recompiling GHC this way?


 |...GHC manual section...|

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