[GHC] #11643: Core lint error in simplifier when compiling Rules1 with -O -dcore-lint (was: Core lint error in simplifier when compiling Rules1 with -O -prof -dcore-lint)

[GHC]

#11643: Core lint error in simplifier when compiling Rules1 with -O -dcore-lint
-------------------------------------+-------------------------------------
        Reporter:  thomie            |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  8.0.1-rc2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:  indexed-
                                     |  types/should_compile/Rules1
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

@@ -1,1 +1,1 @@
- Running `make TEST=Rules1 WAY=profasm` results in a core lint error (see
+ Running `make TEST=Rules1 WAY=optasm` results in a core lint error (see
@@ -33,1 +33,1 @@
- $ ghc-8.0.1 -O -prof Rules1.hs -dcore-lint
+ $ ghc-8.0.1 -O Rules1.hs -dcore-lint

New description:

 Running `make TEST=Rules1 WAY=optasm` results in a core lint error (see
 attachment) with ghc-8.0.1-rc2.

 This is the code:
 {{{#!hs
 {-# LANGUAGE TypeFamilies #-}

 module Rules1 where

 class C a where
   data T a

 instance (C a, C b) => C (a,b) where
   data T (a,b) = TPair (T a) (T b)

 mapT :: (C a, C b) => (a -> b) -> T a -> T b
 {-# NOINLINE mapT #-}  -- Otherwwise we get a warning from the rule
 mapT = undefined

 zipT :: (C a, C b) => T a -> T b -> T (a,b)
 {-# NOINLINE [1] zipT #-}
 zipT = undefined

 {-# RULES

 "zipT/mapT" forall f x y.
   zipT (mapT f x) y = mapT (\(x,y) -> (f x, y)) (zipT x y)

  #-}
 }}}

 {{{
 $ ghc-8.0.1 -O Rules1.hs -dcore-lint
 }}}

 This is a regression from 7.10.3, and core lint errors are bad, so setting
 priority to highest.

--

Comment (by thomie):

 Update: also without `-prof`.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11643#comment:2>
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