[Haskell-cafe] Re: coherence when overlapping?
simonpj at microsoft.com
Thu Apr 13 04:52:47 EDT 2006
| I believe that GHC's overlapping instance extensions
| effectively uses inequalities.
I tried to write down GHC's rules in the manual:
The short summary is:
- find candidate instances that match
- if there is exactly one, choose it
- if the is more than one, choose the best fit UNLESS that choice
would be changed if a type variable was instantiated
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