[commit: ghc] master: DsBinds: Avoid using String when desugaring CallStack construction (65bf7ba)

[git at git.haskell.org]

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

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/65bf7baa81772b7f07a4c74d3510dbd2ef03592d/ghc

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

commit 65bf7baa81772b7f07a4c74d3510dbd2ef03592d
Author: Ben Gamari <ben at smart-cactus.org>
Date:   Wed Sep 23 00:56:03 2015 +0200

    DsBinds: Avoid using String when desugaring CallStack construction
    
    Previously CallStacks would be built using String, which would pull in
    GHC.Base while compiling GHC.Err. Use [Char] instead.


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

65bf7baa81772b7f07a4c74d3510dbd2ef03592d
 compiler/deSugar/DsBinds.hs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/compiler/deSugar/DsBinds.hs b/compiler/deSugar/DsBinds.hs
index 6576093..28e866d 100644
--- a/compiler/deSugar/DsBinds.hs
+++ b/compiler/deSugar/DsBinds.hs
@@ -47,7 +47,7 @@ import Type
 import Kind (returnsConstraintKind)
 import Coercion hiding (substCo)
 import TysWiredIn ( eqBoxDataCon, coercibleDataCon, mkListTy
-                  , mkBoxedTupleTy, stringTy, typeNatKind, typeSymbolKind )
+                  , mkBoxedTupleTy, charTy, typeNatKind, typeSymbolKind )
 import Id
 import MkId(proxyHashId)
 import Class
@@ -1023,7 +1023,10 @@ dsEvCallStack cs = do
                         , return $ mkIntExprInt df (srcSpanEndCol l)
                         ])
 
-  let callSiteTy = mkBoxedTupleTy [stringTy, srcLocTy]
+  -- Be careful to use [Char] instead of String here to avoid
+  -- unnecessary dependencies on GHC.Base, particularly when
+  -- building GHC.Err.absentError
+  let callSiteTy = mkBoxedTupleTy [mkListTy charTy, srcLocTy]
 
   matchId         <- newSysLocalDs $ mkListTy callSiteTy