Revert "[SPARK-43849][BUILD] Enable unused imports check for Scala 2.13"

This reverts commit a9f13e1.

connector/connect/server/src/main/scala/org/apache/spark/sql/connect/planner/SparkConnectPlanner.scala

@@ -31,9 +31,13 @@ import org.apache.spark.connect.proto
 import org.apache.spark.connect.proto.{ExecutePlanResponse, SqlCommand, StreamingQueryCommand, StreamingQueryCommandResult, StreamingQueryInstanceId, WriteStreamOperationStart, WriteStreamOperationStartResult}
 import org.apache.spark.connect.proto.ExecutePlanResponse.SqlCommandResult
 import org.apache.spark.connect.proto.Parse.ParseFormat
+import org.apache.spark.connect.proto.StreamingQueryCommand
+import org.apache.spark.connect.proto.StreamingQueryCommandResult
+import org.apache.spark.connect.proto.StreamingQueryInstanceId
 import org.apache.spark.connect.proto.StreamingQueryManagerCommand
 import org.apache.spark.connect.proto.StreamingQueryManagerCommandResult
 import org.apache.spark.connect.proto.StreamingQueryManagerCommandResult.StreamingQueryInstance
+import org.apache.spark.connect.proto.WriteStreamOperationStart
 import org.apache.spark.connect.proto.WriteStreamOperationStart.TriggerCase
 import org.apache.spark.ml.{functions => MLFunctions}
 import org.apache.spark.sql.{Column, Dataset, Encoders, ForeachWriter, RelationalGroupedDataset, SparkSession}

pom.xml

@@ -2867,9 +2867,9 @@
               <arg>-explaintypes</arg>
               <arg>-target:jvm-1.8</arg>
               <arg>-Wconf:cat=deprecation:wv,any:e</arg>
-              <arg>-Wunused:imports</arg>
               <!--
                 TODO(SPARK-33805): Undo the corresponding deprecated usage suppression rule after fixed
+                <arg>-Wunused:imports</arg>
               -->
               <arg>-Wconf:cat=scaladoc:wv</arg>
               <arg>-Wconf:cat=lint-multiarg-infix:wv</arg>
@@ -2903,12 +2903,6 @@
               <arg>-Wconf:cat=unchecked&amp;msg=outer reference:s</arg>
               <arg>-Wconf:cat=unchecked&amp;msg=eliminated by erasure:s</arg>
               <arg>-Wconf:msg=^(?=.*?a value of type)(?=.*?cannot also be).+$:s</arg>
-              <!--
-                TODO(SPARK-43850): Remove the following suppression rules and remove `import scala.language.higherKinds`
-                from the corresponding files when Scala 2.12 is no longer supported.
-              -->
-              <arg>-Wconf:cat=unused-imports&amp;src=org\/apache\/spark\/graphx\/impl\/VertexPartitionBase.scala:s</arg>
-              <arg>-Wconf:cat=unused-imports&amp;src=org\/apache\/spark\/graphx\/impl\/VertexPartitionBaseOps.scala:s</arg>
             </args>
             <jvmArgs>
               <jvmArg>-Xss128m</jvmArg>

project/SparkBuild.scala

@@ -256,7 +256,8 @@ object SparkBuild extends PomBuild {
           // see `scalac -Wconf:help` for details
           "-Wconf:cat=deprecation:wv,any:e",
           // 2.13-specific warning hits to be muted (as narrowly as possible) and addressed separately
-          "-Wunused:imports",
+          // TODO(SPARK-33499): Enable this option when Scala 2.12 is no longer supported.
+          // "-Wunused:imports",
           "-Wconf:cat=lint-multiarg-infix:wv",
           "-Wconf:cat=other-nullary-override:wv",
           "-Wconf:cat=other-match-analysis&site=org.apache.spark.sql.catalyst.catalog.SessionCatalog.lookupFunction.catalogFunction:wv",
@@ -282,11 +283,7 @@ object SparkBuild extends PomBuild {
           // 4. `fruitless type test: a value of TypeA cannot also be a TypeB`
           "-Wconf:cat=unchecked&msg=outer reference:s",
           "-Wconf:cat=unchecked&msg=eliminated by erasure:s",
-          "-Wconf:msg=^(?=.*?a value of type)(?=.*?cannot also be).+$:s",
-          // TODO(SPARK-43850): Remove the following suppression rules and remove `import scala.language.higherKinds`
-          // from the corresponding files when Scala 2.12 is no longer supported.
-          "-Wconf:cat=unused-imports&src=org\\/apache\\/spark\\/graphx\\/impl\\/VertexPartitionBase.scala:s",
-          "-Wconf:cat=unused-imports&src=org\\/apache\\/spark\\/graphx\\/impl\\/VertexPartitionBaseOps.scala:s"
+          "-Wconf:msg=^(?=.*?a value of type)(?=.*?cannot also be).+$:s"
         )
       }
     }

sql/catalyst/src/main/scala-2.13/org/apache/spark/sql/catalyst/expressions/ExpressionSet.scala

@@ -17,7 +17,7 @@
 
 package org.apache.spark.sql.catalyst.expressions
 
-import scala.collection.mutable
+import scala.collection.{mutable, IterableFactory, IterableOps}
 import scala.collection.mutable.ArrayBuffer
 
 object ExpressionSet {