builtin: implement array.pop()

vlib/builtin/array_test.v

@@ -946,3 +946,29 @@ fn test_reverse_in_place() {
 	c.reverse_in_place()
 	assert c == [[5, 6], [3, 4], [1, 2]]
 }
+
+fn test_array_int_pop() {
+	mut a := [1,2,3,4,5]
+	assert a.len == 5
+	x := a.last()
+	y := a.pop()
+	assert x == y
+	assert a.len == 4
+	z := a.pop()
+	assert a.len == 3
+	assert z == 4
+	a.pop()
+	a.pop()
+	final := a.pop()
+	assert final == 1
+}
+
+fn test_array_string_pop() {
+	mut a := ['abc', 'def', 'xyz']
+	assert a.len == 3
+	assert a.pop() == 'xyz'
+	assert a.pop() == 'def'
+	assert a.pop() == 'abc'
+	assert a.len == 0
+	assert a.cap == 3
+}