[commit: ghc] master: Wrap a bracket quotation in a coercion that makes it have the right type (0b2a6a0)

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/0b2a6a0580c34e4fcb77a67719d77b358bb4d69d

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

commit 0b2a6a0580c34e4fcb77a67719d77b358bb4d69d
Author: Simon Peyton Jones <[email protected]>
Date:   Mon Oct 15 15:07:16 2012 +0100

    Wrap a bracket quotation in a coercion that makes it have the right type
    
    This is the right fix to Trac #7276 (part 2), which makes the
    interaction with -fdefer-type-errors and TH work properly.

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

 compiler/typecheck/TcSplice.lhs |   14 +++++++-------
 1 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/compiler/typecheck/TcSplice.lhs b/compiler/typecheck/TcSplice.lhs
index c5f0af3..7c064b8 100644
--- a/compiler/typecheck/TcSplice.lhs
+++ b/compiler/typecheck/TcSplice.lhs
@@ -350,22 +350,22 @@ tcBracket brack res_ty
           -- We build a single implication constraint with a BracketSkol;
           -- that in turn tells simplifyTop to report only definite
           -- errors
-       ; (_,lie) <- captureConstraints $
-                    newImplication BracketSkol [] [] $
-                    setStage brack_stage $
-                    do { meta_ty <- tc_bracket cur_stage brack
-                       ; unifyType meta_ty res_ty }
+       ; ((_binds1, meta_ty), lie) <- captureConstraints $
+                          newImplication BracketSkol [] [] $
+                          setStage brack_stage $
+                          tc_bracket cur_stage brack
 
           -- It's best to simplify the constraint now, even though in
           -- principle some later unification might be useful for it,
           -- because we don't want these essentially-junk TH implication
           -- contraints floating around nested inside other constraints
           -- See for example Trac #4949
-       ; _ <- simplifyTop lie
+       ; _binds2 <- simplifyTop lie
 
         -- Return the original expression, not the type-decorated one
        ; pendings <- readMutVar pending_splices
-       ; return (noLoc (HsBracketOut brack pendings)) }
+       ; co <- unifyType meta_ty res_ty
+       ; return (noLoc (mkHsWrapCo co (HsBracketOut brack pendings))) }
 
 tc_bracket :: ThStage -> HsBracket Name -> TcM TcType
 tc_bracket outer_stage br@(VarBr _ name)     -- Note [Quoting names]