[GHC] #15422: GHCi debugger doesn't see free variables when using ApplicativeDo

[GHC]

#15422: GHCi debugger doesn't see free variables when using ApplicativeDo
-------------------------------------+-------------------------------------
           Reporter:  simonmar       |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.6.1
          Component:  Compiler       |           Version:  8.4.3
           Keywords:  ApplicativeDo  |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):  Phab:D4991     |         Wiki Page:
-------------------------------------+-------------------------------------
 ```
 > ghci break029.hs
 GHCi, version 8.2.2: http://www.haskell.org/ghc/  :? for help
 [1 of 1] Compiling Main             ( break029.hs, interpreted )
 Ok, one module loaded.
 *Main> :!cat break029.hs
 {-# LANGUAGE ApplicativeDo #-}

 f :: Int -> IO Int
 f x = do
   y <- return (x + 1)
   return (y * 2)
 *Main> :step f 3
 Stopped in Main.f, break029.hs:(4,7)-(6,16)
 _result :: IO Int = _
 x :: Int = 3
 [break029.hs:(4,7)-(6,16)] [break029.hs:(4,7)-(6,16)] *Main> :list
 3  f :: Int -> IO Int
 4  f x = do
 5    y <- return (x + 1)
 6    return (y * 2)
 7
 [break029.hs:(4,7)-(6,16)] [break029.hs:(4,7)-(6,16)] *Main> :step
 Stopped in Main.f, break029.hs:5:8-21
 _result :: IO Int = _
 x :: Int = 3
 [break029.hs:5:8-21] [break029.hs:5:8-21] *Main> :list
 4  f x = do
 5    y <- return (x + 1)
 6    return (y * 2)
 [break029.hs:5:8-21] [break029.hs:5:8-21] *Main> :step
 Stopped in Main.f, break029.hs:6:11-15
 _result :: Int = _
 [break029.hs:6:11-15] [break029.hs:6:11-15] *Main> y

 <interactive>:7:1: error: Variable not in scope: y
 ```

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15422>
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