#7401: Can't derive instance for Eq when datatype has no constructor, while it
is
trivial do do so.
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Reporter: jpbernardy | Owner:
Type: feature request | Status: infoneeded
Priority: normal | Milestone: 7.8.1
Component: Compiler | Version: 7.6.1
Keywords: deriving | Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: GHC rejects valid program
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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Comment(by kosmikus):
It's useful for example when you're using such a type as an argument to
another datatype, which happens to place an Eq constraint on its argument.
However, it seems that this works when standalone deriving is used. That
might be a viable workaround if it's somehow difficult to fix.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7401#comment:5>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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