Change type of TcGadt.refineType, plus consequences

[ghc-hetmet.git] / compiler / typecheck / TcPat.lhs

diff --git a/compiler/typecheck/TcPat.lhs b/compiler/typecheck/TcPat.lhs
index e1a1f24..c9b5d6e 100644 (file)
--- a/compiler/typecheck/TcPat.lhs
+++ b/compiler/typecheck/TcPat.lhs
@@ -279,7 +279,9 @@ tc_lpat :: LPat Name
 tc_lpat (L span pat) pat_ty pstate thing_inside
   = setSrcSpan span              $
     maybeAddErrCtxt (patCtxt pat) $
-    do { let (coercion, pat_ty') = refineType (pat_reft pstate) pat_ty
+    do { let mb_reft = refineType (pat_reft pstate) pat_ty
+             pat_ty' = case mb_reft of { Just (_, ty') -> ty'; Nothing -> pat_ty }
+
                -- Make sure the result type reflects the current refinement
                -- We must do this here, so that it correctly ``sees'' all
                -- the refinements to the left.  Example:
@@ -289,7 +291,10 @@ tc_lpat (L span pat) pat_ty pstate thing_inside
                -- pattern had better see it.
 
        ; (pat', tvs, res) <- tc_pat pstate pat pat_ty' thing_inside
-       ; return (mkCoPat coercion (L span pat') pat_ty, tvs, res) }
+       ; let final_pat = case mb_reft of
+                               Nothing     -> pat'
+                               Just (co,_) -> CoPat (WpCo co) pat' pat_ty
+       ; return (L span final_pat, tvs, res) }
 
 --------------------
 tc_pat :: PatState