#1496: Newtypes and type families combine to produce inconsistent FC(X) axiom
sets
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Reporter: sorear | Owner: simonpj
Type: bug | Status: new
Priority: normal | Milestone: 6.12 branch
Component: Compiler (Type checker) | Version: 6.7
Severity: critical | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Os: Unknown/Multiple
Architecture: Unknown/Multiple |
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Comment (by SamB):
Well, we had a conversation about this on IRC today, and Cale has
convinced me that there is a bug in the definition of ~ in your papers.
<Cale> The main reason that newtypes exist is 1) to ensure that things are
not confused with the original type, and 2) to allow separate instances to
be written without overhead.[[BR]]
<Cale> For ~ to resolve them as the same type goes against both.[[BR]]
<Cale> Basically, the way that ~ is treating newtype right now is how it
ought to be treating 'type'
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1496#comment:23>
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