[GHC] #12955: Confusing error (module is not loaded) when more hsigs provided than -instantiated-with

[GHC]

#12955: Confusing error (module is not loaded) when more hsigs provided than
-instantiated-with
-------------------------------------+-------------------------------------
        Reporter:  ezyang            |                Owner:  ezyang
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:  backpack
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 Edward Z. Yang <ezyang@…>):

 In [changeset:"24f6bec94411aa6c39a2c94ce5154ffe96ae330f/ghc"
 24f6bec9/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="24f6bec94411aa6c39a2c94ce5154ffe96ae330f"
 Sanity check if we pick up an hsig file without -instantiated-with.

 Summary:
 Previously we would just let compilation proceed along until
 we tried to pull up the Module for the hsig file, and get
 main:A instead of <A>, and get a mysterious error.  Check
 for this earlier!

 Fixes #12955.

 Signed-off-by: Edward Z. Yang <ezyang at cs.stanford.edu>

 Test Plan: validate

 Reviewers: simonpj, austin, bgamari

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D2815

 GHC Trac Issues: #12955
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12955#comment:1>
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