Disallow upcasting complex data types to string type

Author: gengliangwang

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala

@@ -131,7 +131,8 @@ object Cast {
     case (from: DecimalType, to: NumericType) if from.isTighterThan(to) => true
     case (f, t) if legalNumericPrecedence(f, t) => true
     case (DateType, TimestampType) => true
-    case (_, StringType) => true
+    case (_: AtomicType, StringType) => true
+    case (_: CalendarIntervalType, StringType) => true
 
     // Spark supports casting between long and timestamp, please see `longToTimestamp` and
     // `timestampToLong` for details.

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala

@@ -1002,6 +1002,11 @@ class CastSuite extends SparkFunSuite with ExpressionEvalHelper {
         }
       }
     }
+    numericTypes.foreach { dt =>
+      makeComplexTypes(dt, true).foreach { complexType =>
+        assert(!Cast.canUpCast(dt, StringType))
+      }
+    }
   }
 
   test("SPARK-27671: cast from nested null type in struct") {