#4485: Unexplained change in type-inference + OverlappingInstances in
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Reporter: JeremyShaw | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.0.1 RC1
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: GHC rejects valid program
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Comment(by simonpj):
Right. I think you need !IncoherentInstances. With this flag, and the new
typechecker patches, your module compiles ok.
Currently GHC crashes without !IncoherentInstances, for a tiresome reason;
Dimitrios is fixing that.
To make !IncoherentInstances behave as well as possible, we should really
wait until all ''other'' equalities are solved, to minimise the chance of
a bogus choice (as you say). We'll do that in due course.
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4485#comment:4>
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