Added AsInstanceOf and demoted ArraysEquals to Info

input/src/main/scala/fix/AsInstanceOf.scala

@@ -0,0 +1,33 @@
+/*
+rule = AsInstanceOf
+ */
+package fix
+
+object AsInstanceOf {
+  // In the original Scapegoat test code, there are tests with SuppressWarning annotations.
+  // We chose to not include these as the same could be done for every rule. If a user wants to suppress a rule, they can simply remove it from the configuration.
+  def test(): Unit = {
+    val s: Any = "sammy"
+    println(s.asInstanceOf[String]) // assert: AsInstanceOf
+
+    case class MappingCharFilter(name: String, mappings: (String, String)*) // scalafix: ok;
+
+    val pf: PartialFunction[Any, Unit] = {
+      case s: String        => println(s) // scalafix: ok;
+      case i: Int if i == 4 => println(i) // scalafix: ok;
+      case _                => println("no match :(") // scalafix: ok;
+    }
+
+    sealed trait MyGADT[T]
+    final case class VariantInt(value: Int) extends MyGADT[Int]
+    final case class VariantString(value: String) extends MyGADT[String]
+
+    def doStuff[T](gadt: MyGADT[T]): T = { // scalafix: ok;
+      gadt match {
+        case VariantInt(value)    => value
+        case VariantString(value) => value
+      }
+    }
+  }
+
+}

rules/src/main/resources/META-INF/services/scalafix.v1.Rule

@@ -51,4 +51,5 @@ fix.InterpolationToString
 fix.EitherGet
 fix.NullParameter
 fix.ArraysEquals
-fix.ArraysToString
+fix.ArraysToString
+fix.AsInstanceOf

rules/src/main/scala/fix/ArraysEquals.scala

@@ -15,7 +15,7 @@ class ArraysEquals extends SemanticRule("ArraysEquals") {
     "Checks for comparison of arrays using == which will always return false.",
     pos,
     "Array equals is not an equality check. Use sameElements or convert to another collection type.",
-    LintSeverity.Warning
+    LintSeverity.Info
   )
 
   override def fix(implicit doc: SemanticDocument): Patch = {

rules/src/main/scala/fix/AsInstanceOf.scala

@@ -0,0 +1,28 @@
+/*
+rule = AsInstanceOf
+ */
+package fix
+
+import scalafix.lint.LintSeverity
+import scalafix.v1._
+
+import scala.meta._
+
+class AsInstanceOf extends SemanticRule("AsInstanceOf") {
+
+  private def diag(pos: Position) = Diagnostic(
+    "",
+    "Checks for use of asInstanceOf.",
+    pos,
+    "Use of asInstanceOf is considered a bad practice - consider using pattern matching instead.",
+    LintSeverity.Warning
+  )
+
+  override def fix(implicit doc: SemanticDocument): Patch = {
+    doc.tree.collect {
+      // Corresponds to a.asInstanceOf(...) or a.asInstanceOf[...]
+      case t @ Term.Select(_, Term.Name("asInstanceOf")) => Patch.lint(diag(t.pos))
+    }.asPatch
+  }
+
+}