[GHC] #12959: GHC doesn't warn about missing implementations for class methods beginning with an underscore

[GHC]

#12959: GHC doesn't warn about missing implementations for class methods beginning
with an underscore
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Other             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by RyanGlScott):

 * cc: simonpj (added)


Comment:

 At the very least, I've found the commit (
 http://git.haskell.org/ghc.git/commit/96f33e63fe913298becbef33bf95daee98fbe44d
 ) all the way back from 2001 which introduced this quirk:

 {{{
 From 96f33e63fe913298becbef33bf95daee98fbe44d Mon Sep 17 00:00:00 2001
 From: unknown <simonpj at MSRC-4971295.europe.corp.microsoft.com>
 Date: Tue, 24 Sep 2013 20:01:31 +0100
 Subject: [PATCH] Move defaultClassMinimalDef from BuildTyCl to TcClassDcl

 Simple refactoring.

 Also in Vectorise.Types/TyConDecl, simply propagate the classMinimalDef
 from the class we are vectorising. Simpler and more direct.
 ---
  compiler/iface/BuildTyCl.lhs                   | 12 +-----------
  compiler/typecheck/TcClassDcl.lhs              | 18 +++++++++++++-----
  compiler/vectorise/Vectorise/Type/TyConDecl.hs |  4 ++--
  3 files changed, 16 insertions(+), 18 deletions(-)
 }}}

 Simon, do you remember why you made this change? The commit description
 doesn't really allude to it (other than "Simple refactoring").

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12959#comment:3>
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