[GHC] #12410: Somehow detect splicing in ghci

[GHC]

#12410: Somehow detect splicing in ghci
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        Reporter:  Iceland_jack      |                Owner:  (none)
            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 RyanGlScott):

 The GHCi prompt is only flexible because it has syntactic cues that it
 uses to distinguish between expressions, declarations, imports, etc. With
 Template Haskell splices, you have no such syntactic cues. The only way I
 could envision comment:3 ever being feasible is if we hacked the
 typechecker to treat `Q Exp` and `Q [Dec]`-returning splices differently,
 which is a lot of work for questionable benefit.

 comment:6 has the advantage that it's simple, works today, and is
 consistent with how other expressions and declarations are treated in GHCi
 (for instance, `3;` won't parse in GHCi's prompt). In light of this, I'm
 inclined to favor the simpler solution.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12410#comment:8>
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