[GHC] #11588: haddock documents misleading type signature for TypeError in GHC.TypeLits

[GHC]

#11588: haddock documents misleading type signature for TypeError in GHC.TypeLits
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        Reporter:  carter            |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Documentation     |              Version:  8.0.1-rc2
      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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@@ -18,0 +18,4 @@
+
+ the relevant haddocks can be seen in the RC2 docs currently hosted at
+ http://downloads.haskell.org/~ghc/8.0.1-rc2/docs/html/libraries/base-4.9.0.0
+ /GHC-TypeLits.html

New description:

 {{{
 type family TypeError a :: b
 }}}

 is what is shown in the haddocks, which is misleading, at least to those
 accustomed to reading vanilla type families.

    1) its impossible from the haddock info to know that the actual type
 signature is `type family TypeError (a :: ErrorMessage) :: b` , that
 requires reading the source of the module (a generally useful thing
 always, but still, disappointing that its needed to understand this)

    2) i also need  read the source to notice that the definition of the
 type family is a closed with no cases! It seems odd (at least to me) that
 haddock doesn't disclose the closedness. (this might be an artifact of it
 being an empty closed type family, which wasn't possible prior to ghc 8.0
 anyways)

 the relevant haddocks can be seen in the RC2 docs currently hosted at
 http://downloads.haskell.org/~ghc/8.0.1-rc2/docs/html/libraries/base-4.9.0.0
 /GHC-TypeLits.html

--

Comment (by carter):

 http://downloads.haskell.org/~ghc/8.0.1-rc2/docs/html/libraries/base-4.9.0.0
 /GHC-TypeLits.html
 is a link

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11588#comment:1>
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