Fixed bug in unicity check in linear typing

Test case included

compiler/heptagon/analysis/linear_typing.ml

@@ -774,8 +774,9 @@ and expect env lin e =
   let l, env = match e.e_desc with
     | Evar x ->
       let actual_lin = lin_of_ident x env in
-      let env = check_linearity_exp env e lin in
-        unify_lin lin actual_lin, env
+      let found_lin = unify_lin lin actual_lin in
+      let env = check_linearity_exp env e found_lin in
+        found_lin, env
 
     | Emerge (_, c_e_list) ->
         let env = List.fold_left (fun env (_, e) -> safe_expect env lin e) env c_e_list in

test/bad/linear_fun.ept

@@ -0,0 +1,20 @@
+const n:int = 100
+
+type tab = float^n
+
+node f(x : tab at r) returns (o : tab at r)
+let
+  o = x;
+tel
+
+node main() returns (o:float)
+var u : tab at r;
+    z1 : tab; z2 : tab at r;
+let
+  init<<r>> u = (0.0)^n;
+
+  z1 = f(u);
+  z2 = f(u);
+
+  o = 0.0;
+tel