[GHC] #9768: reify returns only first instance of class

[GHC]

#9768: reify returns only first instance of class
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              Reporter:  qnikst      |            Owner:  goldfire
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:
             Component:  Compiler    |          Version:  7.8.3
            Resolution:              |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
  https://gist.github.com/qnikst/b93e7154e78bcc159be2|
              Blocking:              |
Differential Revisions:              |
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Changes (by goldfire):

 * owner:   => goldfire


Comment:

 If you change your `test.hs` to

 {{{
 {-# LANGUAGE TemplateHaskell #-}

 import Test

 def "A"
 def "B"

 $(return [])

 main = $(test)
 }}}

 it works. The extra splice changes the order of processing of top-level
 blocks. GHC breaks a module into a sequence of mutually-recursive blocks,
 separated by top-level declaration splices. But, it seems that the
 processing of these blocks does not proceed in strict top-to-bottom order.

 This doesn't quite go against spec -- TH claims to process splices in a
 non-deterministic order -- but I think we can do better for top-level
 declaration splices.

 I'll take a look at this.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9768#comment:1>
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