where
tc_elt elt_ty expr = tcPolyExpr expr elt_ty
+-- For tuples, take care to preserve rigidity
+-- E.g. case (x,y) of ....
+-- The scrutinee should have a rigid type if x,y do
+-- The general scheme is the same as in tcIdApp
tcExpr (ExplicitTuple exprs boxity) res_ty
- = do { arg_tys <- boxySplitTyConApp (tupleTyCon boxity (length exprs)) res_ty
- ; exprs' <- tcPolyExprs exprs arg_tys
- ; return (ExplicitTuple exprs' boxity) }
+ = 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
+ ; arg_tys' <- mapM refineBox arg_tys
+ ; 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
= do { (pat', cmd') <- tcProc pat cmd res_ty