[GHC] #16261: [] interpreted as an overloaded list in rule LHS

[GHC]

#16261: [] interpreted as an overloaded list in rule LHS
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.10.1
       Component:  Compiler          |              Version:  8.6.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  error/warning at compile-time      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by dfeuer):

 Replying to [comment:10 simonpj]:
 > > Yes, that's it. But the module doesn't even enable OverloadedLists.
 >
 > That is indeed odd. Digging into why would be v helpful.

 I don't know anything about the implementation of the `RULES` system. What
 determines which extensions are in play in `RULES`? Do you agree with my
 opinion that `OverloadedLists` should ''never'' be enabled in a rule LHS,
 regardless of which extensions are enabled in the module?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16261#comment:11>
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