[MINOR] Resolve a number of miscellaneous build warnings

## What changes were proposed in this pull request?

This change resolves a number of build warnings that have accumulated, before 2.x. It does not address a large number of deprecation warnings, especially related to the Accumulator API. That will happen separately.

## How was this patch tested?

Jenkins

Author: Sean Owen <sowen@cloudera.com>

Closes #13377 from srowen/BuildWarnings.

4 files changed, 7 insertions, 2 deletions

diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/ScalaReflectionSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/ScalaReflectionSuite.scala
index 1b25f5d7d0..85563ddedc 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/ScalaReflectionSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/ScalaReflectionSuite.scala
@@ -288,7 +288,7 @@ class ScalaReflectionSuite extends SparkFunSuite {
     assert(serializer.children.head.asInstanceOf[Literal].value === UTF8String.fromString("value"))
     assert(serializer.children.last.isInstanceOf[NewInstance])
     assert(serializer.children.last.asInstanceOf[NewInstance]
-      .cls.isInstanceOf[Class[org.apache.spark.sql.catalyst.util.GenericArrayData]])
+      .cls.isAssignableFrom(classOf[org.apache.spark.sql.catalyst.util.GenericArrayData]))
   }
 
   private val dataTypeForComplexData = dataTypeFor[ComplexData]
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoderSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoderSuite.scala
index 3d97113b52..232dcc9ee5 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoderSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoderSuite.scala
@@ -365,7 +365,8 @@ class ExpressionEncoderSuite extends PlanTest with AnalysisTest {
           Arrays.deepEquals(b1.asInstanceOf[Array[AnyRef]], b2.asInstanceOf[Array[AnyRef]])
         case (b1: Array[_], b2: Array[_]) =>
           Arrays.equals(b1.asInstanceOf[Array[AnyRef]], b2.asInstanceOf[Array[AnyRef]])
-        case (left: Comparable[Any], right: Comparable[Any]) => left.compareTo(right) == 0
+        case (left: Comparable[_], right: Comparable[_]) =>
+          left.asInstanceOf[Comparable[Any]].compareTo(right) == 0
         case _ => input == convertedBack
       }
 
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala
index cbf4a8a612..44889d92ee 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala
@@ -17,6 +17,8 @@
 
 package org.apache.spark.sql
 
+import scala.language.existentials
+
 import org.apache.spark.sql.catalyst.analysis.UnresolvedRelation
 import org.apache.spark.sql.catalyst.TableIdentifier
 import org.apache.spark.sql.execution.joins._
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/FileCatalogSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/FileCatalogSuite.scala
index 85c2e8ba55..0d9ea51272 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/FileCatalogSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/FileCatalogSuite.scala
@@ -19,6 +19,8 @@ package org.apache.spark.sql.execution.datasources
 
 import java.io.File
 
+import scala.language.reflectiveCalls
+
 import org.apache.hadoop.fs.Path
 
 import org.apache.spark.sql.catalyst.util._