#1651: panic when interactively evaluating expression with a family type
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Reporter: chak | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler (Type checker) | Version: 6.7
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Os: Unknown | Testcase:
Architecture: Unknown |
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Comment (by simonpj):
Hmm. Here's a FD version:
{{{
foo 'x'
where
foo :: C a b => a -> b
class C a b | a -> b
instance C Char Bool
}}}
The call `(tcMonoExpr (foo 'x') box)`
will perform a subsumption check `b <= box`
and that will fill the box with a `TauTv`.
So what's missing is that when we defer we should fill `BoxTvs` with
`TauTvs`. I think that it'd be enough to call `unBox` instead of
`zonkTcType` in defer_unification.
Don't invest too much in this. I'm working with Dimitrios on rejigging
the whole over-complicated boxy-type story.
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1651>
GHC <http://www.haskell.org/ghc/>
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