[GHC] #9207: Detect obvious cases of infinite recursion.

[GHC]

#9207: Detect obvious cases of infinite recursion.
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        Reporter:  mrugiero          |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.4.4
      Resolution:                    |             Keywords:  infinite
                                     |  recursion
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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Comment (by svenpanne):

 OK, let's forget about the warning caused by not using `loadImg` for a
 moment.

 Why should a compiler warn about the body of `loadImage`? I seriously hope
 that it doesn't warn, because `liftIO` is a method of the `MonadIO` type
 class, so the compiler has no knowledge whatsoever about it, apart from
 its type. So passing `loadImage fpath` to it might actually make sense,
 see the `repeat` example above. If you are lucky and the compiler uses
 enough optimizations, you might get a warning at `loadImage`'s use sites,
 because then it might see enough context, but the function alone is
 perfectly OK from a compiler's point of view.

 In a lazy language, it's quite hard to distinguish between "wanted
 infinite recursion" and "unwanted infinite recursion".

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9207#comment:12>
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