Don't keep shadowed variables in ghci, both renamer and type checker

In #14052 (closed), we reverted D2447, then #11547 (closed) exists in HEAD again. In ticket:14052#comment:151549 and ticket:14052#comment:140478, we decide that shadowed variables shouldn't be keep at all. This ticket is created to track the idea.

The same error of #11547 (closed) was also reported in ticket:14996#comment:151477,

$ inplace/bin/ghc-stage2 --interactive
GHCi, version 8.5.20180403: http://www.haskell.org/ghc/  :? for help
Prelude> 1
1
Prelude> 1
1
Prelude> _

<interactive>:1:1: error:
GHC internal error: ‘Ghci1.it’ is not in scope during type > checking, but it passed the renamer
tcl_env of environment: []

(giving "1" twice is needed to reproduce the error)

NB: input "1" twice to create shadowed context is necessary to reproduce this bug.

mentioned in issue #14996 (closed)

changed milestone to %8.6.1

changed weight to 5

added GHCi Tbug Trac import labels

assigned to @sighingnow

mentioned in issue #15037 (closed)

changed the description

added typed holes label

Similar shenanigans:

$ ~/Software/ghc/inplace/bin/ghc-stage2 --interactive
GHCi, version 8.5.20180420: http://www.haskell.org/ghc/  :? for help
Loaded GHCi configuration from /home/rgscott/.ghci
λ> data F
λ> data F
λ> _

<interactive>:1:1: error:
    GHC internal error: ‘Ghci1.$trModule’ is not in scope during type checking, but it passed the renamer
    tcl_env of environment: []

mentioned in issue #15202 (closed)

Another example from #15202 (closed):

Run ghc --interactive, and at the prompt type

default ()
fish :: Eq a => a; fish = undefined
foo :: String; foo = show _

The following error appears:

<interactive>:1:1: error:
GHC internal error: ‘Ghci1.$trModule’ is not in scope during type checking, but it passed the renamer
tcl_env of environment: [r2CZ :-> Identifier[foo::String, TopLevelLet]]

Trac metadata

Trac field	Value
Related	#11547 (closed), #14052 (closed) → #11547 (closed), #14052 (closed), #15202 (closed)

changed milestone to %8.8.1

These won't be addressed in GHC 8.6.

mentioned in issue #15314 (closed)

mentioned in issue #15321 (closed)

This is fixed in https://phabricator.haskell.org/D4909

changed milestone to %8.6.1

Trac metadata

Trac field	Value
Differential revisions	- → D4909

mentioned in commit 39de4e3d

Reverting this back to "new". It seems to me that the patch doesn't actually fix this problem, but works around it. Please make the status "patch" again if I'm wrong.

I don't see a regression test -- please add one?

This ticket isn't fixed by D4909. With a debug-enabled stage2 compiler, for the script in description, we will get a panic:

Prelude> 1
1
(0.02 secs, 65,728 bytes)
Prelude> 1
1
(0.00 secs, 64,352 bytes)
Prelude> _
ghc-stage2.exe: panic! (the 'impossible' happened)
  (GHC version 8.7.20180629 for x86_64-unknown-mingw32):
        ASSERT failed!
  Cur lvl = 1
  Imp lvl = 1
  Call stack:
      CallStack (from HasCallStack):
        callStackDoc, called at compiler\utils\Outputable.hs:1164:37 in ghc:Outputable
        pprPanic, called at compiler\utils\Outputable.hs:1223:5 in ghc:Outputable
        assertPprPanic, called at compiler\\typecheck\\TcSimplify.hs:1548:120 in ghc:TcSimplify
CallStack (from -prof):
  HscMain.ioMsgMaybe (compiler\main\HscMain.hs:(252,1)-(257,128))
  HscMain.hscParsedStmt (compiler\main\HscMain.hs:(1548,1)-(1564,36))
  HscMain.hscStmtWithLocation (compiler\main\HscMain.hs:(1533,1)-(1541,50))
  GHC.withCleanupSession (compiler\main\GHC.hs:(469,1)-(477,27))
  GHC.runGhc (compiler\main\GHC.hs:(444,1)-(449,26))
  GHC.defaultErrorHandler (compiler\main\GHC.hs:(384,1)-(416,7))

Besides, this ticket is intend to solve the problem described in #11547 (closed), the GHC internal error (for script reported by #11547 (closed)) still occurs after D4909.

mentioned in commit f6ac0833

The program in #15314 (closed) now triggers the same assertion failure as ticket:15007#comment:156301 after D4909.

Prelude> let x = ()
Prelude> let x = ()
Prelude> :t _

sighingnow, are you sure you rebuilt it correctly? I'm also using a debug-enabled compiler and here are the outputs I'm getting:

~ $ ghc-stage2 --interactive
GHCi, version 8.7.20180704: http://www.haskell.org/ghc/  :? for help
Prelude> 1
1
Prelude> 1
1
Prelude> _

<interactive>:3:1: error:
    • Found hole: _ :: t
      Where: ‘t’ is a rigid type variable bound by
               the inferred type of it :: t
               at <interactive>:3:1
    • In the expression: _
      In an equation for ‘it’: it = _
    • Relevant bindings include it :: t (bound at <interactive>:3:1)
Prelude>

~ $ ghc-stage2 --interactive
GHCi, version 8.7.20180704: http://www.haskell.org/ghc/  :? for help
Prelude> let x = ()
Prelude> let x = ()
Prelude> :t _

<interactive>:1:1: error:
    • Found hole: _ :: t
      Where: ‘t’ is a rigid type variable bound by
               the inferred type of it :: t
               at <interactive>:1:1
    • In the expression: _
Prelude>

I have rebuilt the stage2 compiler after manually delete all .o and .hi files in compiler/stage2/build and still get the same panic. I will try a fresh build later.

I just validated with the regression tests so it should be fine after a make clean.

osa1: I still get the same assertion failure with ticket:15007#comment:156301 after a fresh debug-enabled build. My build flavors is:

SRC_HC_OPTS        = -O -H64m
GhcStage1HcOpts    = -O
GhcStage2HcOpts    = -O -DDEBUG
GhcLibHcOpts       = -O -dcore-lint
BUILD_PROF_LIBS    = YES
SplitObjs          = NO
SplitSections      = NO
HADDOCK_DOCS       = NO
BUILD_SPHINX_HTML  = NO
BUILD_SPHINX_PDF   = NO
BUILD_MAN          = NO

LAX_DEPENDENCIES   = YES
GhcProfiled        = YES
INTEGER_LIBRARY      = integer-simple

If I remove the -DDEBUG in GhcStage2HcOpts and rebuild ghc-stage2, I can get the same error message with ticket:15007#comment:156304.

I was using GhcDebugged = YES but apparently that doesn't add -DDEBUG, it just adds -debug.

It seems this ticket needs more work.

#15007 (closed) merged with 22c951e6.

mentioned in issue #15384

mentioned in issue #15401 (closed)

closed

We have a ticket for the panic this caused: #15384. Closing this one as fixed.

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedFixed

mentioned in issue #15511 (closed)

added error messages label

added Pnormal label

mentioned in issue #20455 (closed)