[SPARK-34881][SQL][FOLLOWUP] Implement toString() and sql() methods for TRY_CAST

### What changes were proposed in this pull request?

Implement toString() and sql() methods for TRY_CAST

### Why are the changes needed?

The new expression should have a different name from `CAST` in SQL/String representation.

### Does this PR introduce _any_ user-facing change?

Yes, in the result of `explain()`, users can see try_cast if the new expression is used.

### How was this patch tested?

Unit tests.

Closes #32098 from gengliangwang/tryCastString.

Authored-by: Gengliang Wang <ltnwgl@gmail.com>
Signed-off-by: Gengliang Wang <ltnwgl@gmail.com>

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

@@ -84,4 +84,10 @@ case class TryCast(child: Expression, dataType: DataType, timeZoneId: Option[Str
 
   override def typeCheckFailureMessage: String =
     AnsiCast.typeCheckFailureMessage(child.dataType, dataType, None, None)
+
+  override def toString: String = {
+    s"try_cast($child as ${dataType.simpleString})"
+  }
+
+  override def sql: String = s"TRY_CAST(${child.sql} AS ${dataType.sql})"
 }

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

@@ -20,7 +20,7 @@ package org.apache.spark.sql.catalyst.expressions
 import scala.reflect.ClassTag
 
 import org.apache.spark.sql.catalyst.InternalRow
-import org.apache.spark.sql.types.DataType
+import org.apache.spark.sql.types.{DataType, IntegerType}
 
 class TryCastSuite extends AnsiCastSuiteBase {
   override protected def cast(v: Any, targetType: DataType, timeZoneId: Option[String]) = {
@@ -48,4 +48,8 @@ class TryCastSuite extends AnsiCastSuiteBase {
   override def checkCastToNumericError(l: Literal, to: DataType, tryCastResult: Any): Unit = {
     checkEvaluation(cast(l, to), tryCastResult, InternalRow(l.value))
   }
+
+  test("try_cast: to_string") {
+    assert(TryCast(Literal("1"), IntegerType).toString == "try_cast(1 as int)")
+  }
 }

sql/core/src/test/resources/sql-tests/results/try_cast.sql.out

@@ -5,7 +5,7 @@
 -- !query
 SELECT TRY_CAST('1.23' AS int)
 -- !query schema
-struct<CAST(1.23 AS INT):int>
+struct<TRY_CAST(1.23 AS INT):int>
 -- !query output
 NULL
 
@@ -13,7 +13,7 @@ NULL
 -- !query
 SELECT TRY_CAST('1.23' AS long)
 -- !query schema
-struct<CAST(1.23 AS BIGINT):bigint>
+struct<TRY_CAST(1.23 AS BIGINT):bigint>
 -- !query output
 NULL
 
@@ -21,7 +21,7 @@ NULL
 -- !query
 SELECT TRY_CAST('-4.56' AS int)
 -- !query schema
-struct<CAST(-4.56 AS INT):int>
+struct<TRY_CAST(-4.56 AS INT):int>
 -- !query output
 NULL
 
@@ -29,7 +29,7 @@ NULL
 -- !query
 SELECT TRY_CAST('-4.56' AS long)
 -- !query schema
-struct<CAST(-4.56 AS BIGINT):bigint>
+struct<TRY_CAST(-4.56 AS BIGINT):bigint>
 -- !query output
 NULL
 
@@ -37,7 +37,7 @@ NULL
 -- !query
 SELECT TRY_CAST('abc' AS int)
 -- !query schema
-struct<CAST(abc AS INT):int>
+struct<TRY_CAST(abc AS INT):int>
 -- !query output
 NULL
 
@@ -45,7 +45,7 @@ NULL
 -- !query
 SELECT TRY_CAST('abc' AS long)
 -- !query schema
-struct<CAST(abc AS BIGINT):bigint>
+struct<TRY_CAST(abc AS BIGINT):bigint>
 -- !query output
 NULL
 
@@ -53,7 +53,7 @@ NULL
 -- !query
 SELECT TRY_CAST('' AS int)
 -- !query schema
-struct<CAST( AS INT):int>
+struct<TRY_CAST( AS INT):int>
 -- !query output
 NULL
 
@@ -61,7 +61,7 @@ NULL
 -- !query
 SELECT TRY_CAST('' AS long)
 -- !query schema
-struct<CAST( AS BIGINT):bigint>
+struct<TRY_CAST( AS BIGINT):bigint>
 -- !query output
 NULL
 
@@ -69,7 +69,7 @@ NULL
 -- !query
 SELECT TRY_CAST(NULL AS int)
 -- !query schema
-struct<CAST(NULL AS INT):int>
+struct<TRY_CAST(NULL AS INT):int>
 -- !query output
 NULL
 
@@ -77,7 +77,7 @@ NULL
 -- !query
 SELECT TRY_CAST(NULL AS long)
 -- !query schema
-struct<CAST(NULL AS BIGINT):bigint>
+struct<TRY_CAST(NULL AS BIGINT):bigint>
 -- !query output
 NULL
 
@@ -85,7 +85,7 @@ NULL
 -- !query
 SELECT TRY_CAST('123.a' AS int)
 -- !query schema
-struct<CAST(123.a AS INT):int>
+struct<TRY_CAST(123.a AS INT):int>
 -- !query output
 NULL
 
@@ -93,7 +93,7 @@ NULL
 -- !query
 SELECT TRY_CAST('123.a' AS long)
 -- !query schema
-struct<CAST(123.a AS BIGINT):bigint>
+struct<TRY_CAST(123.a AS BIGINT):bigint>
 -- !query output
 NULL
 
@@ -101,7 +101,7 @@ NULL
 -- !query
 SELECT TRY_CAST('-2147483648' AS int)
 -- !query schema
-struct<CAST(-2147483648 AS INT):int>
+struct<TRY_CAST(-2147483648 AS INT):int>
 -- !query output
 -2147483648
 
@@ -109,7 +109,7 @@ struct<CAST(-2147483648 AS INT):int>
 -- !query
 SELECT TRY_CAST('-2147483649' AS int)
 -- !query schema
-struct<CAST(-2147483649 AS INT):int>
+struct<TRY_CAST(-2147483649 AS INT):int>
 -- !query output
 NULL
 
@@ -117,7 +117,7 @@ NULL
 -- !query
 SELECT TRY_CAST('2147483647' AS int)
 -- !query schema
-struct<CAST(2147483647 AS INT):int>
+struct<TRY_CAST(2147483647 AS INT):int>
 -- !query output
 2147483647
 
@@ -125,7 +125,7 @@ struct<CAST(2147483647 AS INT):int>
 -- !query
 SELECT TRY_CAST('2147483648' AS int)
 -- !query schema
-struct<CAST(2147483648 AS INT):int>
+struct<TRY_CAST(2147483648 AS INT):int>
 -- !query output
 NULL
 
@@ -133,7 +133,7 @@ NULL
 -- !query
 SELECT TRY_CAST('-9223372036854775808' AS long)
 -- !query schema
-struct<CAST(-9223372036854775808 AS BIGINT):bigint>
+struct<TRY_CAST(-9223372036854775808 AS BIGINT):bigint>
 -- !query output
 -9223372036854775808
 
@@ -141,7 +141,7 @@ struct<CAST(-9223372036854775808 AS BIGINT):bigint>
 -- !query
 SELECT TRY_CAST('-9223372036854775809' AS long)
 -- !query schema
-struct<CAST(-9223372036854775809 AS BIGINT):bigint>
+struct<TRY_CAST(-9223372036854775809 AS BIGINT):bigint>
 -- !query output
 NULL
 
@@ -149,7 +149,7 @@ NULL
 -- !query
 SELECT TRY_CAST('9223372036854775807' AS long)
 -- !query schema
-struct<CAST(9223372036854775807 AS BIGINT):bigint>
+struct<TRY_CAST(9223372036854775807 AS BIGINT):bigint>
 -- !query output
 9223372036854775807
 
@@ -157,7 +157,7 @@ struct<CAST(9223372036854775807 AS BIGINT):bigint>
 -- !query
 SELECT TRY_CAST('9223372036854775808' AS long)
 -- !query schema
-struct<CAST(9223372036854775808 AS BIGINT):bigint>
+struct<TRY_CAST(9223372036854775808 AS BIGINT):bigint>
 -- !query output
 NULL
 
@@ -165,7 +165,7 @@ NULL
 -- !query
 SELECT TRY_CAST('interval 3 month 1 hour' AS interval)
 -- !query schema
-struct<CAST(interval 3 month 1 hour AS INTERVAL):interval>
+struct<TRY_CAST(interval 3 month 1 hour AS INTERVAL):interval>
 -- !query output
 3 months 1 hours
 
@@ -173,7 +173,7 @@ struct<CAST(interval 3 month 1 hour AS INTERVAL):interval>
 -- !query
 SELECT TRY_CAST('abc' AS interval)
 -- !query schema
-struct<CAST(abc AS INTERVAL):interval>
+struct<TRY_CAST(abc AS INTERVAL):interval>
 -- !query output
 NULL
 
@@ -181,7 +181,7 @@ NULL
 -- !query
 select TRY_CAST('true' as boolean)
 -- !query schema
-struct<CAST(true AS BOOLEAN):boolean>
+struct<TRY_CAST(true AS BOOLEAN):boolean>
 -- !query output
 true
 
@@ -189,7 +189,7 @@ true
 -- !query
 select TRY_CAST('false' as boolean)
 -- !query schema
-struct<CAST(false AS BOOLEAN):boolean>
+struct<TRY_CAST(false AS BOOLEAN):boolean>
 -- !query output
 false
 
@@ -197,7 +197,7 @@ false
 -- !query
 select TRY_CAST('abc' as boolean)
 -- !query schema
-struct<CAST(abc AS BOOLEAN):boolean>
+struct<TRY_CAST(abc AS BOOLEAN):boolean>
 -- !query output
 NULL
 
@@ -205,7 +205,7 @@ NULL
 -- !query
 SELECT TRY_CAST("2021-01-01" AS date)
 -- !query schema
-struct<CAST(2021-01-01 AS DATE):date>
+struct<TRY_CAST(2021-01-01 AS DATE):date>
 -- !query output
 2021-01-01
 
@@ -213,7 +213,7 @@ struct<CAST(2021-01-01 AS DATE):date>
 -- !query
 SELECT TRY_CAST("2021-101-01" AS date)
 -- !query schema
-struct<CAST(2021-101-01 AS DATE):date>
+struct<TRY_CAST(2021-101-01 AS DATE):date>
 -- !query output
 NULL
 
@@ -221,7 +221,7 @@ NULL
 -- !query
 SELECT TRY_CAST("2021-01-01 00:00:00" AS timestamp)
 -- !query schema
-struct<CAST(2021-01-01 00:00:00 AS TIMESTAMP):timestamp>
+struct<TRY_CAST(2021-01-01 00:00:00 AS TIMESTAMP):timestamp>
 -- !query output
 2021-01-01 00:00:00
 
@@ -229,6 +229,6 @@ struct<CAST(2021-01-01 00:00:00 AS TIMESTAMP):timestamp>
 -- !query
 SELECT TRY_CAST("2021-101-01 00:00:00" AS timestamp)
 -- !query schema
-struct<CAST(2021-101-01 00:00:00 AS TIMESTAMP):timestamp>
+struct<TRY_CAST(2021-101-01 00:00:00 AS TIMESTAMP):timestamp>
 -- !query output
 NULL