[commit: ghc] ghc-8.0: Use implicit CallStacks for ASSERT when available (ec85e1e)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : ghc-8.0
Link       : http://ghc.haskell.org/trac/ghc/changeset/ec85e1e58fdcea165c4bd9881b091f07f2989014/ghc

>---------------------------------------------------------------

commit ec85e1e58fdcea165c4bd9881b091f07f2989014
Author: Bartosz Nitka <niteria at gmail.com>
Date:   Wed Jan 13 14:44:58 2016 +0100

    Use implicit CallStacks for ASSERT when available
    
    This aids with debugging, since all you have to do to get more
    stack frames is add a constraint `(?callStack :: CallStack) =>`.
    
    Old output:
    ```
    ghc-stage2: panic! (the 'impossible' happened)
      (GHC version 8.1.20160107 for x86_64-unknown-linux):
            ASSERT failed!
      file compiler/types/TyCoRep.hs line 1800
      InScope []
      [Xuv :-> n_av5[sk]]
      []
    ```
    
    New output:
    ```
    ghc-stage2: panic! (the 'impossible' happened)
      (GHC version 8.1.20160107 for x86_64-unknown-linux):
            ASSERT failed!
      CallStack (from ImplicitParams):
      assertPprPanic, called at compiler/types/TyCoRep.hs:1800:95 in
    ghc:TyCoRep
      InScope []
      [Xuv :-> n_av5[sk]]
      []
    ```
    
    Test Plan:
    harbormaster
    manual testing
    
    Reviewers: austin, gridaphobe, bgamari
    
    Reviewed By: gridaphobe, bgamari
    
    Subscribers: thomie
    
    Differential Revision: https://phabricator.haskell.org/D1751
    
    (cherry picked from commit 88d6d5aae2ae86646084f3a060ae911eff589b7a)


>---------------------------------------------------------------

ec85e1e58fdcea165c4bd9881b091f07f2989014
 compiler/utils/Outputable.hs | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/compiler/utils/Outputable.hs b/compiler/utils/Outputable.hs
index c3bdf5e..35a59c6 100644
--- a/compiler/utils/Outputable.hs
+++ b/compiler/utils/Outputable.hs
@@ -1096,15 +1096,24 @@ warnPprTrace True   file  line  msg x
   where
     heading = hsep [text "WARNING: file", text file <> comma, text "line", int line]
 
+-- | Panic with an assertation failure, recording the given file and
+-- line number. Should typically be accessed with the ASSERT family of macros
+#if __GLASGOW_HASKELL__ > 710
+assertPprPanic :: (?callStack :: CallStack) => String -> Int -> SDoc -> a
+assertPprPanic _file _line msg
+  = pprPanic "ASSERT failed!" doc
+  where
+    doc = sep [ text (prettyCallStack ?callStack)
+              , msg ]
+#else
 assertPprPanic :: String -> Int -> SDoc -> a
--- ^ Panic with an assertation failure, recording the given file and line number.
--- Should typically be accessed with the ASSERT family of macros
 assertPprPanic file line msg
   = pprPanic "ASSERT failed!" doc
   where
     doc = sep [ hsep [ text "file", text file
                      , text "line", int line ]
               , msg ]
+#endif
 
 pprDebugAndThen :: DynFlags -> (String -> a) -> SDoc -> SDoc -> a
 pprDebugAndThen dflags cont heading pretty_msg