[GHC] #15007: Don't keep shadowed variables in ghci, both renamer and type checker

[GHC]

#15007: Don't keep shadowed variables in ghci, both renamer and type checker
-------------------------------------+-------------------------------------
        Reporter:  sighingnow        |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  GHCi              |              Version:  8.5
      Resolution:                    |             Keywords:  TypedHoles
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  error/warning at compile-time      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11547 #14052     |  Differential Rev(s):  Phab:D4909
  #15202                             |
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by sighingnow):

 osa1: I still get the same assertion failure with comment:14 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 comment:17.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15007#comment:20>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler