Add test cases for iterator to const iterator assignment

test/src/unit-iterators1.cpp

@@ -1519,48 +1519,64 @@ TEST_CASE("iterators 1")
             json j = true;
 			json::const_iterator it = j.begin();
 			CHECK(it == j.cbegin());
+			it = j.begin();
+			CHECK(it == j.cbegin());
 		}
         SECTION("string")
 		{
             json j = "hello world";
 			json::const_iterator it = j.begin();
 			CHECK(it == j.cbegin());
+			it = j.begin();
+			CHECK(it == j.cbegin());
 		}
         SECTION("array")
 		{
             json j = {1, 2, 3};
 			json::const_iterator it = j.begin();
 			CHECK(it == j.cbegin());
+			it = j.begin();
+			CHECK(it == j.cbegin());
 		}
         SECTION("object")
 		{
             json j = {{"A", 1}, {"B", 2}, {"C", 3}};
 			json::const_iterator it = j.begin();
 			CHECK(it == j.cbegin());
+			it = j.begin();
+			CHECK(it == j.cbegin());
 		}
         SECTION("number (integer)")
 		{
             json j = 23;
 			json::const_iterator it = j.begin();
 			CHECK(it == j.cbegin());
+			it = j.begin();
+			CHECK(it == j.cbegin());
 		}
         SECTION("number (unsigned)")
 		{
             json j = 23u;
 			json::const_iterator it = j.begin();
 			CHECK(it == j.cbegin());
+			it = j.begin();
+			CHECK(it == j.cbegin());
 		}
         SECTION("number (float)")
 		{
             json j = 23.42;
 			json::const_iterator it = j.begin();
 			CHECK(it == j.cbegin());
+			it = j.begin();
+			CHECK(it == j.cbegin());
 		}
         SECTION("null")
 		{
             json j = nullptr;
 			json::const_iterator it = j.begin();
 			CHECK(it == j.cbegin());
+			it = j.begin();
+			CHECK(it == j.cbegin());
 		}
 	}
 }