FIX #1385: make sure tuple instances are loaded

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

diff --git a/compiler/typecheck/TcExpr.lhs b/compiler/typecheck/TcExpr.lhs
index c3bc64b..39e8a5c 100644 (file)
--- a/compiler/typecheck/TcExpr.lhs
+++ b/compiler/typecheck/TcExpr.lhs
@@ -29,6 +29,7 @@ import TcHsType
 import TcPat
 import TcMType
 import TcType
+import TcIface ( checkWiredInTyCon )
 import Id
 import DataCon
 import Name
@@ -302,10 +303,11 @@ tcExpr (ExplicitTuple exprs boxity) res_ty
   = do { tvs <- newBoxyTyVars [argTypeKind | e <- exprs]
        ; let tup_tc     = tupleTyCon boxity (length exprs)
              tup_res_ty = mkTyConApp tup_tc (mkTyVarTys tvs)
-       ; arg_tys   <- preSubType tvs (mkVarSet tvs) tup_res_ty res_ty
-       ; exprs'    <-  tcPolyExprs exprs arg_tys
+       ; checkWiredInTyCon tup_tc      -- Ensure instances are available
+       ; arg_tys  <- preSubType tvs (mkVarSet tvs) tup_res_ty res_ty
+       ; exprs'   <- tcPolyExprs exprs arg_tys
        ; arg_tys' <- mapM refineBox arg_tys
-       ; co_fn <- tcFunResTy (tyConName tup_tc) (mkTyConApp tup_tc arg_tys') res_ty
+       ; co_fn    <- tcFunResTy (tyConName tup_tc) (mkTyConApp tup_tc arg_tys') res_ty
        ; return (mkHsWrap co_fn (ExplicitTuple exprs' boxity)) }
 
 tcExpr (HsProc pat cmd) res_ty