[GHC] #15767: "StgCmmEnv: variable not found" with FunctionalDependencies and FlexibleContexts

[GHC]

#15767: "StgCmmEnv: variable not found" with FunctionalDependencies and
FlexibleContexts
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        Reporter:  roland            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.6.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"6b1102e2cfcffb265fd33cf8a99ab5e6b3f14906/ghc"
 6b1102e2/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="6b1102e2cfcffb265fd33cf8a99ab5e6b3f14906"
 Report a Wanted error even if there are Given ones

 We suppress some Given errors; see Note [Given errors]
 in TcErrors.  But we must be careful not to suppress
 Wanted errors because of the presence of these Given
 errors -- else we might allow compilation to bogusly
 proceed

 The rubber hits the road in TcRnTypes.insolubleCt,
 where we don't want to treat Givens as insoluble,
 nor (and this is the new bit) Deriveds that arise
 from Givens.  See Note [Given insolubles] in TcRnTypes.

 This fixes #15767.
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15767#comment:3>
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