[GHC] #14691: Replace EvTerm with CoreExpr

[GHC]

#14691: Replace EvTerm with CoreExpr
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        Reporter:  nomeata           |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.3
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by nomeata):

 >  I think you can. getEvTerm calls ctEvTerm which always returns either
 an EvId (which we can do in Core) or an EvCoercion (ditto). Aside from
 coercions (alas) all evidence is represented just by an Id.

 Ah, is that an invariant? Could we encode that in the types somehow?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14691#comment:25>
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