Fix DataMirror.internal.chiselTypeClone to preserve Scala type (#3553)

(cherry picked from commit e6c07b3)

core/src/main/scala/chisel3/reflect/DataMirror.scala

@@ -174,8 +174,8 @@ object DataMirror {
   object internal {
     def isSynthesizable(target: Data): Boolean = target.isSynthesizable
     // For those odd cases where you need to care about object reference and uniqueness
-    def chiselTypeClone[T <: Data](target: Data): T = {
-      target.cloneTypeFull.asInstanceOf[T]
+    def chiselTypeClone[T <: Data](target: T): T = {
+      target.cloneTypeFull
     }
   }
 

src/test/scala/chiselTests/reflect/DataMirrorSpec.scala

@@ -111,4 +111,15 @@ class DataMirrorSpec extends ChiselFlatSpec {
   it should "not support name guesses for non-hardware" in {
     an[ExpectedHardwareException] should be thrownBy DataMirror.queryNameGuess(UInt(8.W))
   }
+
+  "chiselTypeClone" should "preserve Scala type information" in {
+    class MyModule extends Module {
+      val in = IO(Input(UInt(8.W)))
+      val out = IO(Output(DataMirror.internal.chiselTypeClone(in)))
+      // The connection checks the types
+      out :#= in
+    }
+    ChiselStage.emitCHIRRTL(new MyModule)
+  }
+
 }