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Diffstat (limited to 'compiler/deSugar/MatchCon.lhs')
| -rw-r--r-- | compiler/deSugar/MatchCon.lhs | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/compiler/deSugar/MatchCon.lhs b/compiler/deSugar/MatchCon.lhs index 10270e50ca..5c4f4273b0 100644 --- a/compiler/deSugar/MatchCon.lhs +++ b/compiler/deSugar/MatchCon.lhs @@ -134,7 +134,8 @@ matchOneCon vars ty (eqn1 : eqns) -- All eqns for a single constructor match_group :: [Id] -> [(ConArgPats, EquationInfo)] -> DsM MatchResult -- All members of the group have compatible ConArgPats match_group arg_vars arg_eqn_prs - = do { (wraps, eqns') <- liftM unzip (mapM shift arg_eqn_prs) + = ASSERT( notNull arg_eqn_prs ) + do { (wraps, eqns') <- liftM unzip (mapM shift arg_eqn_prs) ; let group_arg_vars = select_arg_vars arg_vars arg_eqn_prs ; match_result <- match (group_arg_vars ++ vars) ty eqns' ; return (adjustMatchResult (foldr1 (.) wraps) match_result) } |