From c4723c747fec4557776858641b03e1eb4a0a5878 Mon Sep 17 00:00:00 2001
From: Alasdair
Date: Mon, 23 Nov 2020 14:18:58 +0000
Subject: Don't allow type synonyms with the same name as existing types

---
 src/type_check.ml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'src')

diff --git a/src/type_check.ml b/src/type_check.ml
index aeb9cf01..1ada515e 100644
--- a/src/type_check.ml
+++ b/src/type_check.ml
@@ -647,8 +647,8 @@ end = struct
     else typ_error env (id_loc id) ("Could not prove " ^ string_of_list ", " string_of_n_constraint ncs ^ " for type constructor " ^ string_of_id id)
 
   let add_typ_synonym id typq arg env =
-    if Bindings.mem id env.typ_synonyms then
-      typ_error env (id_loc id) ("Type synonym " ^ string_of_id id ^ " already exists")
+    if bound_typ_id env id then
+      typ_error env (id_loc id) ("Cannot define type synonym " ^ string_of_id id ^ ", as a type or synonym with that name already exists")
     else
       begin
         typ_print (lazy (adding ^ "type synonym " ^ string_of_id id));
-- 
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