Warning fix for unused and redundant imports

[ghc-hetmet.git] / compiler / deSugar / Match.lhs

diff --git a/compiler/deSugar/Match.lhs b/compiler/deSugar/Match.lhs
index a31494e..5294320 100644 (file)
--- a/compiler/deSugar/Match.lhs
+++ b/compiler/deSugar/Match.lhs
@@ -26,7 +26,6 @@ import DataCon
 import MatchCon
 import MatchLit
 import PrelInfo
-import TcType
 import Type
 import TysWiredIn
 import BasicTypes
@@ -610,7 +609,8 @@ JJQC 30-Nov-1997
 
 \begin{code}
 matchWrapper ctxt (MatchGroup matches match_ty)
-  = do { eqns_info   <- mapM mk_eqn_info matches
+  = ASSERT( notNull matches )
+    do { eqns_info   <- mapM mk_eqn_info matches
        ; new_vars    <- selectMatchVars arg_pats
        ; result_expr <- matchEquations ctxt new_vars eqns_info rhs_ty
        ; return (new_vars, result_expr) }