[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
      Resolution:                    |             Keywords:  ApplicativeDo
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4991
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Description changed by simonmar:

Old description:

> ```
> > 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
> ```

New description:

 {{{
 > 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#comment:1>
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