[GHC] #7445: template-haskell : need a good error message instead of just an unexplained panic (was: template-haskell : the impossible happened)

[GHC]

#7445: template-haskell : need a good error message instead of just an unexplained
panic
-------------------------------+--------------------------------------------
Reporter:  erikd               |          Owner:                  
    Type:  bug                 |         Status:  new             
Priority:  normal              |      Component:  Template Haskell
 Version:  7.6.1               |       Keywords:                  
      Os:  Unknown/Multiple    |   Architecture:  Unknown/Multiple
 Failure:  Compile-time crash  |      Blockedby:                  
Blocking:                      |        Related:                  
-------------------------------+--------------------------------------------

Comment(by erikd):

 Found the problem, for ```QuasiArith.hs``` I had:

 {{{
 module QuasiArith
     ( eval
     , expr
     ) where
 }}}

 If I change the module declaration to:

 {{{
 module QuasiArith where
 }}}

 it no longer panics and in fact even works and generates the correct
 result.

 I'm not sure what was causing it to fail. I tried exporting all top level
 functions and values in ```QuasiArith.hs``` and it still failed.

 Would in be sensible to disallow restricted exports for all files that
 import ```Language.Haskell.TH.Quote```?

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7445#comment:3>
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