[GHC] #12249: Template Haskell top level scoping error

[GHC]

#12249: Template Haskell top level scoping error
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        Reporter:  simonpj           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Template Haskell  |              Version:  8.0.1
      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 simonpj):

 > But why do we want this behavior?

 Consider the code in the Description.  It seems perfectly reasonable to
 me; the two quasiquotes both bind 'x' but in each case it's clear what
 binds the occurrence of `x` on the RHS of `f1`, `f2`.  I'm thinking of
 splices that generate a wad of code that needs some auxiliary bindings; we
 don't want to have to worry about a clash if we happen to re-use the same
 name when generating the auxiliary bindings in a different splice.

 For example, `deriving` code.  In fact it's this that is causing #12245,
 although that code is generated by GHC itself, not by TH, but it's the
 same idea.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12249#comment:4>
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