[GHC] #13773: Types are not normalized in instance declarations

[GHC]

#13773: Types are not normalized in instance declarations
-------------------------------------+-------------------------------------
        Reporter:  augustss          |                Owner:  (none)
            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:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by augustss):

 No, I don't think GHC should accept (5*2) in a function definition.
 But I think it should accept my instance declaration.
 Here are two reasons:
   * GHC already does some normalization of types in instance declarations
 as it allows me to use type synonyms.
   * In the case of function definitions there is a workaround (guards),
 but there is no such workaround for instances.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13773#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler