#16191: GHC Panic deriving unbox vector (StrictData/unbox-strict-fields
interaction)
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Reporter: dbeacham | Owner: (none)
Type: bug | Status: closed
Priority: normal | Milestone: 8.8.1
Component: Compiler | Version: 8.6.3
Resolution: duplicate | Keywords:
Operating System: Linux | Architecture:
Type of failure: GHC rejects | Unknown/Multiple
valid program | Test Case:
Blocked By: | Blocking:
Related Tickets: #16141 | Differential Rev(s):
Wiki Page: |
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Comment (by Marge Bot ):
In [changeset:"a5373c1fe172dee31e07bcb7c7f6caff1035e6ba/ghc" a5373c1/ghc]:
{{{
#!CommitTicketReference repository="ghc"
revision="a5373c1fe172dee31e07bcb7c7f6caff1035e6ba"
Fix bogus worker for newtypes
The "worker" for a newtype is actually a function
with a small (compulsory) unfolding, namely a cast.
But the construction of this function was plain wrong
for newtype /instances/; it cast the arguemnt to the
family type rather than the representation type.
This never actually bit us because, in the case of a
family instance, we immediately cast the result to
the family type. So we get
\x. (x |> co1) |> co2
where the compositio of co1 and co2 is ill-kinded.
However the optimiser (even the simple optimiser)
just collapsed those casts, ignoring the mis-match
in the middle, so we never saw the problem.
Trac #16191 is indeed a dup of #16141; but the resaon
these tickets produce Lint errors is not the unnecessary
forcing; it's because of the ill-typed casts.
This patch fixes the ill-typed casts, properly. I can't
see a way to trigger an actual failure prior to this
patch, but it's still wrong wrong wrong to have ill-typed
casts, so better to get rid of them.
}}}
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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16191#comment:5
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