From f0b4a103325e150faa3c2bd0a06594b2e62fae43 Mon Sep 17 00:00:00 2001
From: Alasdair
Date: Fri, 8 Mar 2019 00:16:47 +0000
Subject: Fix: Never consider single variable types to be ambiguous

---
 src/type_check.ml | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/type_check.ml b/src/type_check.ml
index 603052b5..48a64226 100644
--- a/src/type_check.ml
+++ b/src/type_check.ml
@@ -1851,7 +1851,7 @@ let instantiate_quants quants unifier =
    they'll be unambigiously unified with the argument types so it's
    better to just not bother with the return type.
 *)
-let rec ambiguous_vars (Typ_aux (aux, _)) =
+let rec ambiguous_vars' (Typ_aux (aux, _)) =
   match aux with
   | Typ_app (_, args) -> List.fold_left KidSet.union KidSet.empty (List.map ambiguous_arg_vars args)
   | _ -> KidSet.empty
@@ -1876,6 +1876,10 @@ and ambiguous_nexp_vars (Nexp_aux (aux, _)) =
   | Nexp_sum (nexp1, nexp2) -> KidSet.union (tyvars_of_nexp nexp1) (tyvars_of_nexp nexp2)
   | _ -> KidSet.empty
 
+let ambiguous_vars typ =
+  let vars = ambiguous_vars' typ in
+  if KidSet.cardinal vars > 1 then vars else KidSet.empty
+
 (**************************************************************************)
 (* 3.5. Subtyping with existentials                                       *)
 (**************************************************************************)
-- 
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