[GHC] #15901: Assert and record that code generation requires distinct uiques for let-binders

[GHC]

#15901: Assert and record that code generation requires distinct uiques for let-
binders
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        Reporter:  sgraf             |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:  ⊥
       Component:  Compiler          |              Version:  8.6.2
      Resolution:                    |             Keywords:  CodeGen
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 simonmar):

 This is currently done by CorePrep, and noted explicitly in the comments
 (`CorePrep.hs`):

 {{{
 6.  Clone all local Ids.
     This means that all such Ids are unique, rather than the
     weaker guarantee of no clashes which the simplifier provides.
     And that is what the code generator needs.

     We don't clone TyVars or CoVars. The code gen doesn't need that,
     and doing so would be tiresome because then we'd need
     to substitute in types and coercions.
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15901#comment:2>
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