From eef3633d9a42dfed03e751e6af3d2917ad566a38 Mon Sep 17 00:00:00 2001
From: Jeremie Dimino <jdimino@janestreet.com>
Date: Mon, 12 Mar 2018 11:22:54 +0000
Subject: [PATCH] Tweak error messages

---
 src/env.ml | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/env.ml b/src/env.ml
index 7c7947d5..7b625243 100644
--- a/src/env.ml
+++ b/src/env.ml
@@ -41,10 +41,18 @@ let of_unix arr =
   |> List.map ~f:(fun s ->
     match String.lsplit2 s ~on:'=' with
     | None ->
-      Sexp.code_error "Env.of_unix doesn't support env vars without '='"
+      Sexp.code_error "Env.of_unix: entry without '=' found in the environ"
         ["var", Sexp.To_sexp.string s]
     | Some (k, v) -> (k, v))
-  |> Map.of_list_exn
+  |> Map.of_list
+  |> function
+  | Ok x -> x
+  | Error (var, v1, v2) ->
+    Sexp.code_error "Env.of_unix: duplicated variable found in the environment"
+      [ "var"   , Sexp.To_sexp.string var
+      ; "value1", Sexp.To_sexp.string v1
+      ; "value2", Sexp.To_sexp.string v2
+      ]
 
 let initial =
   let i =