Re: [GHC] #10103: Outdated comment (or bug?) in `types/TyCon.hs` (was: Outdated comment (or bug?) in TyCon.hs)

20 Feb 2015

      #10103: Outdated comment (or bug?) in `types/TyCon.hs`
-------------------------------------+-------------------------------------
        Reporter:  thomie            |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  7.8.4
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
-------------------------------------+-------------------------------------
Description changed by thomie:

Old description:
...
The docstring for `coreExpandTyCon_maybe` says it should do something
different than `tcExpandTyCon_maybe`, but it doesn't:
{{{#!haskell
-- ^ Used to create the view the /typechecker/ has on 'TyCon's.
-- We expand (closed) synonyms only, cf. 'coreExpandTyCon_maybe'
tcExpandTyCon_maybe = ...
-- ^ Used to create the view /Core/ has on 'TyCon's. We expand
-- not only closed synonyms like 'tcExpandTyCon_maybe',
-- but also non-recursive @newtype@s
coreExpandTyCon_maybe tycon tys = tcExpandTyCon_maybe tycon tys
}}}
If the code is correct, and the comment is just outdated, than Note
[Newtype eta] and the docstring for `Type.coreView` should be updated as
well.
The last big change to `coreExpandTyCon_maybe` was made in commit
fdf8656855d26105ff36bdd24d41827b05037b91.
New description:

 The docstring for `coreExpandTyCon_maybe` says it should do something
 different than `tcExpandTyCon_maybe`, but it doesn't:

 {{{#!haskell
 -- ^ Used to create the view the /typechecker/ has on 'TyCon's.
 -- We expand (closed) synonyms only, cf. 'coreExpandTyCon_maybe'
 tcExpandTyCon_maybe = ...

 -- ^ Used to create the view /Core/ has on 'TyCon's. We expand
 -- not only closed synonyms like 'tcExpandTyCon_maybe',
 -- but also non-recursive @newtype@s
 coreExpandTyCon_maybe tycon tys = tcExpandTyCon_maybe tycon tys
 }}}

 If the code is correct, and the comment is just outdated, than Note
 [Newtype eta] and the docstrings for `Type.coreView` and `Type.tcView`
 should be updated as well.

 The last big change to `coreExpandTyCon_maybe` was made in commit
 fdf8656855d26105ff36bdd24d41827b05037b91.

--

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10103#comment:1
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