[GHC] #9813: Error when reifying type constructor

[GHC]

#9813: Error when reifying type constructor
-------------------------------------+-------------------------------------
        Reporter:  owst              |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Template Haskell  |              Version:  7.8.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D1899
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by goldfire):

 Recent arguments have not shifted me from my proposal in comment:15.

 What about

 {{{
 f = g 5
 g = $(...)
 }}}

 The suggestion to process declarations that do not contain a splice before
 declarations that do fails here. Instead, we recognize that `f` and `g`
 are in a mutually recursive group and process them together. `g` cannot
 reify `f`. Note that comment:15 says that only already-processed
 declarations (that is, not in the same mutually recursive group) are
 available.

 It does strike me (inspired by comment:16) that with all this toposorting
 going on, we may be able to avoid having top-level splices break the file
 up into declaration groups. The current behavior seems something like a
 feeble attempt at a toposort, anyway. I suppose changing this would break

 {{{
 f = $(...)
 $( ... reify 'f ... )
 }}}

 though. (That code would work now.) So, upon further thought, this
 particular aspect of the change seems dead in the water. Note that my
 pessimism here is only about comment:16, not comment:15.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9813#comment:21>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler