Test fix in #1457

Author: goldfirere

ocaml/testsuite/tests/lib-array/test_iarray.ml

@@ -519,3 +519,9 @@ ifarray;;
 [%%expect{|
 - : float iarray = [:1.5; 2.5; 3.5; 4.5; 5.5:]
 |}];;
+
+let singleton x = [: x :]
+
+[%%expect{|
+val singleton : 'a -> 'a iarray = <fun>
+|}]