[GHC] #12526: regression in type inference with respect to type families

[GHC]

#12526: regression in type inference with respect to type families
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        Reporter:  Lemming           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler (Type    |              Version:  8.1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  10634             |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by simonpj):

 * milestone:  8.0.2 => 8.2.1


Comment:

 I am in the middle of an upheaval of the constraint solver that fixes this
 among other things. But the change is too big to put in the 8.0.2 branch.

 So I suggest we re-milestone for 8.2, and treat this as something to work-
 around with 8.0.2.  The workaround is simple, as comment:11 says: a type
 signature seems to do the job.  I think it's a fluke that it worked
 before.

 Is that acceptable? I think it'll be hard to fix in 8.0.2.  Yell if that'd
 be really bad for you.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12526#comment:12>
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