Fix a few compiler warnings

src/main/scala/chisel3/compatibility.scala

@@ -10,6 +10,7 @@ package object Chisel {     // scalastyle:ignore package.object.name
   import scala.language.experimental.macros
   import scala.annotation.StaticAnnotation
   import scala.annotation.compileTimeOnly
+  import scala.language.implicitConversions
 
   implicit val defaultCompileOptions = chisel3.core.ExplicitCompileOptions.NotStrict
 

src/test/scala/chiselTests/IOCompatibility.scala

@@ -30,7 +30,7 @@ class IOCModuleVec(val n: Int) extends Module {
 
 class IOCModuleWire extends Module {
   val io = IO(new IOCSimpleIO)
-  val inc = Wire(Module(new IOCPlusOne).io.chiselCloneType)
+  val inc = Wire(chiselTypeOf(Module(new IOCPlusOne).io))
   inc.in := io.in
   io.out := inc.out
 }

src/test/scala/chiselTests/Printf.scala

@@ -14,7 +14,7 @@ class SinglePrintfTester() extends BasicTester {
 }
 
 class ASCIIPrintfTester() extends BasicTester {
-  printf((0x20 to 0x7e).map(_ toChar).mkString.replace("%", "%%"))
+  printf((0x20 to 0x7e).map(_.toChar).mkString.replace("%", "%%"))
   stop()
 }
 

src/test/scala/chiselTests/RecordSpec.scala

@@ -5,14 +5,18 @@ package chiselTests
 import chisel3._
 import chisel3.testers.BasicTester
 import chisel3.util.{Counter, Queue}
+import chisel3.experimental.requireIsChiselType
 import scala.collection.immutable.ListMap
 
 // An example of how Record might be extended
 // In this case, CustomBundle is a Record constructed from a Tuple of (String, Data)
 //   it is a possible implementation of a programmatic "Bundle"
 //   (and can by connected to MyBundle below)
 final class CustomBundle(elts: (String, Data)*) extends Record {
-  val elements = ListMap(elts map { case (field, elt) => field -> elt.chiselCloneType }: _*)
+  val elements = ListMap(elts map { case (field, elt) =>
+    requireIsChiselType(elt)
+    field -> elt
+  }: _*)
   def apply(elt: String): Data = elements(elt)
   override def cloneType = (new CustomBundle(elements.toList: _*)).asInstanceOf[this.type]
 }