[GHC] #15765: Make the "extract" functions in RnTypes pure

[GHC]

#15765: Make the "extract" functions in RnTypes pure
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        Reporter:  goldfire          |                Owner:  simonpj
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.6.1
      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 Simon Peyton Jones <simonpj@…>):

 In [changeset:"e6bf96c9700aacbd75169dbf2cc14c9216c0133f/ghc"
 e6bf96c9/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="e6bf96c9700aacbd75169dbf2cc14c9216c0133f"
 De-monadise the 'extract' functions in RnTypes

 As Trac #15765 says, Once upon a time, the extract functions
 at the bottom of RnTypes were pure. Then, along came -XTypeInType,
 which needed to do a check in these functions for users mixing
 type variables with kind variables.

 Now, however, with -XTypeInType gone again, we no longer
 do this check. Thus, there is no reason to keep these
 functions monadic.
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15765#comment:3>
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