[AURON #1870][BUILD] Add -Xfatal-warnings and resolve existing -Ywarn-unused warnings

Author: yew1eb

pom.xml

@@ -375,6 +375,7 @@
           <scalaVersion>${scalaLongVersion}</scalaVersion>
           <args>
             <arg>-Ywarn-unused</arg>
+            <arg>-Xfatal-warnings</arg>
           </args>
         </configuration>
         <dependencies>
@@ -839,6 +840,7 @@
                 <!-- In Scala 2.13, the plugin's functionality has been included in the compiler -->
                 <!-- directly under the -Ymacro-annotations flag.  -->
                 <arg>-Ymacro-annotations</arg>
+                <arg>-Xfatal-warnings</arg>
               </args>
               <compilerPlugins>
                 <compilerPlugin>

spark-version-annotation-macros/src/main/scala/org/apache/auron/sparkver.scala

@@ -16,8 +16,7 @@
  */
 package org.apache.auron
 
-import scala.annotation.StaticAnnotation
-import scala.annotation.compileTimeOnly
+import scala.annotation.{compileTimeOnly, nowarn, StaticAnnotation}
 import scala.language.experimental._
 import scala.reflect.macros.whitebox
 
@@ -97,16 +96,16 @@ object sparkver {
 }
 
 @compileTimeOnly("enable macro paradise to expand macro annotations")
-final class sparkver(vers: String) extends StaticAnnotation {
+final class sparkver(@nowarn vers: String) extends StaticAnnotation {
   def macroTransform(annottees: Any*): Any = macro sparkver.Macros.verEnable
 }
 
 @compileTimeOnly("enable macro paradise to expand macro annotations")
-final class sparkverEnableMembers(vers: String) extends StaticAnnotation {
+final class sparkverEnableMembers(@nowarn vers: String) extends StaticAnnotation {
   def macroTransform(annottees: Any*): Any = macro sparkver.Macros.verEnableMembers
 }
 
 @compileTimeOnly("enable macro paradise to expand macro annotations")
-final class sparkverEnableOverride(vers: String) extends StaticAnnotation {
+final class sparkverEnableOverride(@nowarn vers: String) extends StaticAnnotation {
   def macroTransform(annottees: Any*): Any = macro sparkver.Macros.verEnableOverride
 }