[GHC] #12003: Improve error message about closed variables

[GHC]

#12003: Improve error message about closed variables
-------------------------------------+-------------------------------------
        Reporter:                    |                Owner:
  facundo.dominguez                  |
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
                                     |  StaticPointers
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11656            |  Differential Rev(s):  Phab:D2167
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"e9dfb6e51f0cd585611a742ce7167e307ee7e7e8/ghc" e9dfb6e/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="e9dfb6e51f0cd585611a742ce7167e307ee7e7e8"
 Improve the error messages for static forms.

 Now the message explains why closed variables are not closed when
 encountered in the body of (static ...).

 This required adding to the local environment the free variables of
 the local bindings in scope. Thus we can analyze and explain why a
 variable is not closed when encountered.

 Test Plan: ./validate

 Reviewers: austin, simonpj, bgamari

 Reviewed By: bgamari

 Subscribers: mboes, thomie

 Differential Revision: https://phabricator.haskell.org/D2167

 GHC Trac Issues: #12003
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12003#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler