Make printing of binding results optional in GHCi, and document it

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

diff --git a/compiler/typecheck/TcRnDriver.lhs b/compiler/typecheck/TcRnDriver.lhs
index 875d4f6..acf003f 100644 (file)
--- a/compiler/typecheck/TcRnDriver.lhs
+++ b/compiler/typecheck/TcRnDriver.lhs
@@ -965,15 +965,20 @@ mkPlan stmt@(L loc (BindStmt {}))
   | [L _ v] <- collectLStmtBinders stmt                -- One binder, for a bind stmt 
   = do { let print_v  = L loc $ ExprStmt (nlHsApp (nlHsVar printName) (nlHsVar v))
                                           (HsVar thenIOName) placeHolderType
+
+       ; print_bind_result <- doptM Opt_PrintBindResult
+       ; let print_plan = do
+                 { stuff@([v_id], _) <- tcGhciStmts [stmt, print_v]
+                 ; v_ty <- zonkTcType (idType v_id)
+                 ; ifM (isUnitTy v_ty || not (isTauTy v_ty)) failM
+                 ; return stuff }
+
        -- The plans are:
        --      [stmt; print v]         but not if v::()
        --      [stmt]
-       ; runPlans [do { stuff@([v_id], _) <- tcGhciStmts [stmt, print_v]
-                      ; v_ty <- zonkTcType (idType v_id)
-                      ; ifM (isUnitTy v_ty || not (isTauTy v_ty)) failM
-                      ; return stuff },
-                   tcGhciStmts [stmt]
-         ]}
+       ; runPlans ((if print_bind_result then [print_plan] else []) ++
+                   [tcGhciStmts [stmt]])
+       }
 
 mkPlan stmt
   = tcGhciStmts [stmt]