Avoid copying Arrays

One last request to avoid copying Arrays when the underlying storage is
already an Array.

distribution/lib/Standard/Base/0.0.0-dev/src/Data/Vector.enso

@@ -114,7 +114,15 @@ type Vector
     type Vector storage
 
     to_array self =
-        self.storage.to_array
+        arr = self.storage.to_array
+        case arr of
+            Array ->
+                arr
+            _     ->
+                len = self.storage.length
+                a = Array.new len
+                Array.copy arr 0 a 0 len
+                a
 
     ## Returns the number of elements stored in this vector.
 

distribution/lib/Standard/Base/0.0.0-dev/src/Polyglot/Proxy_Polyglot_Array.enso

@@ -21,7 +21,4 @@ type Proxy_Polyglot_Array
 
     to_array : Array Any
     to_array self =
-        len = self.length
-        a = Array.new len
-        0.up_to len . each ix-> a.set_at ix (self.at ix)
-        a
+        self.arr

test/Tests/src/Semantic/Js_Interop_Spec.enso

@@ -45,6 +45,9 @@ foreign js make_object = """
 foreign js make_array = """
     return [{ x: 10}, {x: 20}, {x: 30}];
 
+foreign js make_simple_array = """
+    return [10, 20, 30];
+
 foreign js make_str str = """
     return "foo " + str + " bar"
 
@@ -95,6 +98,8 @@ spec = Test.group "Polyglot JS" <|
     Test.specify "should expose array interfaces for JS arrays" <|
         vec = Vector.from_polyglot_array make_array
         vec.map .x . should_equal [10, 20, 30]
+        vec2 = Vector.from_polyglot_array make_simple_array
+        vec2.to_array.at 0 . should_equal 10
 
     Test.specify "should correctly marshall strings" <|
         str = make_str "x" + " baz"