diff --git a/compiler/src/dotty/tools/dotc/Driver.scala b/compiler/src/dotty/tools/dotc/Driver.scala
index 327ee29756b4..804f5379e8f0 100644
--- a/compiler/src/dotty/tools/dotc/Driver.scala
+++ b/compiler/src/dotty/tools/dotc/Driver.scala
@@ -16,7 +16,7 @@ import fromtasty.TASTYCompiler
  *  process, but in most cases you only need to call [[process]] on the
  *  existing object [[Main]].
  */
-class Driver extends DotClass {
+class Driver {
 
   protected def newCompiler(implicit ctx: Context): Compiler =
     if (ctx.settings.fromTasty.value) new TASTYCompiler
diff --git a/compiler/src/dotty/tools/dotc/ast/Positioned.scala b/compiler/src/dotty/tools/dotc/ast/Positioned.scala
index bb4721cfd065..87d46eb9a9bf 100644
--- a/compiler/src/dotty/tools/dotc/ast/Positioned.scala
+++ b/compiler/src/dotty/tools/dotc/ast/Positioned.scala
@@ -10,7 +10,7 @@ import core.StdNames.nme
 
 /** A base class for things that have positions (currently: modifiers and trees)
  */
-abstract class Positioned extends DotClass with Product {
+abstract class Positioned extends Product {
 
   private[this] var curPos: Position = _
 
diff --git a/compiler/src/dotty/tools/dotc/ast/Trees.scala b/compiler/src/dotty/tools/dotc/ast/Trees.scala
index c2ce0f27a308..cf3b1359cfe6 100644
--- a/compiler/src/dotty/tools/dotc/ast/Trees.scala
+++ b/compiler/src/dotty/tools/dotc/ast/Trees.scala
@@ -853,7 +853,7 @@ object Trees {
 
   // ----- Generic Tree Instances, inherited from `tpt` and `untpd`.
 
-  abstract class Instance[T >: Untyped <: Type] extends DotClass { inst =>
+  abstract class Instance[T >: Untyped <: Type] { inst =>
 
     type Tree = Trees.Tree[T]
     type TypTree = Trees.TypTree[T]
diff --git a/compiler/src/dotty/tools/dotc/config/CompilerCommand.scala b/compiler/src/dotty/tools/dotc/config/CompilerCommand.scala
index 12b19b472431..383c2aa9b906 100644
--- a/compiler/src/dotty/tools/dotc/config/CompilerCommand.scala
+++ b/compiler/src/dotty/tools/dotc/config/CompilerCommand.scala
@@ -10,7 +10,7 @@ import Properties._
 
 import scala.collection.JavaConverters._
 
-object CompilerCommand extends DotClass {
+object CompilerCommand {
 
   /** The name of the command */
   def cmdName = "dotc"
diff --git a/compiler/src/dotty/tools/dotc/core/Contexts.scala b/compiler/src/dotty/tools/dotc/core/Contexts.scala
index cf4da2cba87a..d165e521dc17 100644
--- a/compiler/src/dotty/tools/dotc/core/Contexts.scala
+++ b/compiler/src/dotty/tools/dotc/core/Contexts.scala
@@ -710,7 +710,7 @@ object Contexts {
       else assert(thread == Thread.currentThread(), "illegal multithreaded access to ContextBase")
   }
 
-  class GADTMap(initBounds: SimpleIdentityMap[Symbol, TypeBounds]) extends util.DotClass {
+  class GADTMap(initBounds: SimpleIdentityMap[Symbol, TypeBounds]) {
     private[this] var myBounds = initBounds
     def setBounds(sym: Symbol, b: TypeBounds): Unit =
       myBounds = myBounds.updated(sym, b)
diff --git a/compiler/src/dotty/tools/dotc/core/Denotations.scala b/compiler/src/dotty/tools/dotc/core/Denotations.scala
index 82f071859a5d..2100db069eb0 100644
--- a/compiler/src/dotty/tools/dotc/core/Denotations.scala
+++ b/compiler/src/dotty/tools/dotc/core/Denotations.scala
@@ -76,7 +76,7 @@ object Denotations {
   /** A PreDenotation represents a group of single denotations or a single multi-denotation
    *  It is used as an optimization to avoid forming MultiDenotations too eagerly.
    */
-  abstract class PreDenotation extends util.DotClass {
+  abstract class PreDenotation {
 
     /** A denotation in the group exists */
     def exists: Boolean
diff --git a/compiler/src/dotty/tools/dotc/core/NameKinds.scala b/compiler/src/dotty/tools/dotc/core/NameKinds.scala
index 5920b6b29af0..2c69f6339f1c 100644
--- a/compiler/src/dotty/tools/dotc/core/NameKinds.scala
+++ b/compiler/src/dotty/tools/dotc/core/NameKinds.scala
@@ -25,14 +25,14 @@ object NameKinds {
   @sharable private val uniqueNameKinds = new mutable.HashMap[String, UniqueNameKind]
 
   /** A class for the info stored in a derived name */
-  abstract class NameInfo extends DotClass {
+  abstract class NameInfo {
     def kind: NameKind
     def mkString(underlying: TermName): String
     def map(f: SimpleName => SimpleName): NameInfo = this
   }
 
   /** An abstract base class of classes that define the kind of a derived name info */
-  abstract class NameKind(val tag: Int) extends DotClass { self =>
+  abstract class NameKind(val tag: Int) { self =>
 
     /** The info class defined by this kind */
     type ThisInfo <: Info
diff --git a/compiler/src/dotty/tools/dotc/core/Names.scala b/compiler/src/dotty/tools/dotc/core/Names.scala
index fc1774cfd4a9..3de657629fcb 100644
--- a/compiler/src/dotty/tools/dotc/core/Names.scala
+++ b/compiler/src/dotty/tools/dotc/core/Names.scala
@@ -34,7 +34,7 @@ object Names {
   /** A common superclass of Name and Symbol. After bootstrap, this should be
    *  just the type alias Name | Symbol
    */
-  abstract class Designator extends util.DotClass
+  abstract class Designator
 
   /** A name if either a term name or a type name. Term names can be simple
    *  or derived. A simple term name is essentially an interned string stored
diff --git a/compiler/src/dotty/tools/dotc/core/Periods.scala b/compiler/src/dotty/tools/dotc/core/Periods.scala
index 3d4a288915d6..381593246495 100644
--- a/compiler/src/dotty/tools/dotc/core/Periods.scala
+++ b/compiler/src/dotty/tools/dotc/core/Periods.scala
@@ -8,7 +8,7 @@ import dotty.tools.dotc.util.DotClass
  *  run ids represent compiler runs
  *  phase ids represent compiler phases
  */
-abstract class Periods extends DotClass { self: Context =>
+abstract class Periods { self: Context =>
   import Periods._
 
   /** The current phase identifier */
diff --git a/compiler/src/dotty/tools/dotc/core/Phases.scala b/compiler/src/dotty/tools/dotc/core/Phases.scala
index 3894ef445c47..0269c6f536ee 100644
--- a/compiler/src/dotty/tools/dotc/core/Phases.scala
+++ b/compiler/src/dotty/tools/dotc/core/Phases.scala
@@ -1,4 +1,5 @@
-package dotty.tools.dotc
+package dotty.tools
+package dotc
 package core
 
 import Periods._
@@ -263,7 +264,7 @@ object Phases {
     final def isAfterTyper(phase: Phase): Boolean = phase.id > typerPhase.id
   }
 
-  trait Phase extends DotClass {
+  trait Phase {
 
     /** A name given to the `Phase` that can be used to debug the compiler. For
      *  instance, it is possible to print trees after a given phase using:
diff --git a/compiler/src/dotty/tools/dotc/core/Scopes.scala b/compiler/src/dotty/tools/dotc/core/Scopes.scala
index 25c52413bfe9..d4d6f6d734de 100644
--- a/compiler/src/dotty/tools/dotc/core/Scopes.scala
+++ b/compiler/src/dotty/tools/dotc/core/Scopes.scala
@@ -3,7 +3,8 @@
  * @author  Martin Odersky
  */
 
-package dotty.tools.dotc
+package dotty.tools
+package dotc
 package core
 
 import Symbols._
@@ -66,7 +67,7 @@ object Scopes {
    *  or to delete them. These methods are provided by subclass
    *  MutableScope.
    */
-  abstract class Scope extends DotClass with printing.Showable {
+  abstract class Scope extends printing.Showable {
 
     /** The last scope-entry from which all others are reachable via `prev` */
     private[dotc] def lastEntry: ScopeEntry
diff --git a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
index 84400206a7b6..0f54da0573a2 100644
--- a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
+++ b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -16,7 +16,7 @@ import reporting.trace
 
 /** Provides methods to compare types.
  */
-class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling {
+class TypeComparer(initctx: Context) extends ConstraintHandling {
   import TypeComparer._
   implicit val ctx = initctx
 
diff --git a/compiler/src/dotty/tools/dotc/core/TypeErasure.scala b/compiler/src/dotty/tools/dotc/core/TypeErasure.scala
index 3e6f3f29d0ce..36cb45233771 100644
--- a/compiler/src/dotty/tools/dotc/core/TypeErasure.scala
+++ b/compiler/src/dotty/tools/dotc/core/TypeErasure.scala
@@ -343,7 +343,7 @@ import TypeErasure._
  *  @param wildcardOK    Wildcards are acceptable (true when using the erasure
  *                       for computing a signature name).
  */
-class TypeErasure(isJava: Boolean, semiEraseVCs: Boolean, isConstructor: Boolean, wildcardOK: Boolean) extends DotClass {
+class TypeErasure(isJava: Boolean, semiEraseVCs: Boolean, isConstructor: Boolean, wildcardOK: Boolean) {
 
   /**  The erasure |T| of a type T. This is:
    *
diff --git a/compiler/src/dotty/tools/dotc/core/Types.scala b/compiler/src/dotty/tools/dotc/core/Types.scala
index e6b2b92d01d9..40b843cee067 100644
--- a/compiler/src/dotty/tools/dotc/core/Types.scala
+++ b/compiler/src/dotty/tools/dotc/core/Types.scala
@@ -84,7 +84,7 @@ object Types {
    *
    *  Note: please keep in sync with copy in `docs/docs/internals/type-system.md`.
    */
-  abstract class Type extends DotClass with Hashable with printing.Showable {
+  abstract class Type extends Hashable with printing.Showable {
 
 // ----- Tests -----------------------------------------------------
 
diff --git a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
index 18baba35ea6c..fc443e3c5367 100644
--- a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -64,7 +64,7 @@ object Parsers {
     if (source.isSelfContained) new ScriptParser(source)
     else new Parser(source)
 
-  abstract class ParserCommon(val source: SourceFile)(implicit ctx: Context) extends DotClass {
+  abstract class ParserCommon(val source: SourceFile)(implicit ctx: Context) {
 
     val in: ScannerCommon
 
diff --git a/compiler/src/dotty/tools/dotc/transform/TransformByNameApply.scala b/compiler/src/dotty/tools/dotc/transform/TransformByNameApply.scala
index c0825c7e8bea..1e8aa9c72278 100644
--- a/compiler/src/dotty/tools/dotc/transform/TransformByNameApply.scala
+++ b/compiler/src/dotty/tools/dotc/transform/TransformByNameApply.scala
@@ -1,4 +1,5 @@
-package dotty.tools.dotc
+package dotty.tools
+package dotc
 package transform
 
 import MegaPhase._
diff --git a/compiler/src/dotty/tools/dotc/typer/Namer.scala b/compiler/src/dotty/tools/dotc/typer/Namer.scala
index 2933c3dc92a5..f8d83964e82b 100644
--- a/compiler/src/dotty/tools/dotc/typer/Namer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Namer.scala
@@ -102,7 +102,7 @@ trait NamerContextOps { this: Context =>
   }
 
   /** A new context for the interior of a class */
-  def inClassContext(selfInfo: DotClass /* Should be Type | Symbol*/): Context = {
+  def inClassContext(selfInfo: AnyRef /* Should be Type | Symbol*/): Context = {
     val localCtx: Context = ctx.fresh.setNewScope
     selfInfo match {
       case sym: Symbol if sym.exists && sym.name != nme.WILDCARD => localCtx.scope.openForMutations.enter(sym)
diff --git a/compiler/src/dotty/tools/dotc/typer/RefChecks.scala b/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
index e1d755db1b69..41b955c907bb 100644
--- a/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
+++ b/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
@@ -843,7 +843,7 @@ object RefChecks {
 
   type LevelAndIndex = immutable.Map[Symbol, (LevelInfo, Int)]
 
-  class OptLevelInfo extends DotClass {
+  class OptLevelInfo {
     def levelAndIndex: LevelAndIndex = Map()
     def enterReference(sym: Symbol, pos: Position): Unit = ()
   }
diff --git a/compiler/src/dotty/tools/dotc/util/DotClass.scala b/compiler/src/dotty/tools/dotc/util/DotClass.scala
index cdb697a458d0..f9e7e97a219d 100644
--- a/compiler/src/dotty/tools/dotc/util/DotClass.scala
+++ b/compiler/src/dotty/tools/dotc/util/DotClass.scala
@@ -5,8 +5,4 @@ package dotty.tools.dotc.util
  */
 class DotClass {
 
-  /** Throws an `UnsupportedOperationException` with the given method name. */
-  def unsupported(methodName: String): Nothing =
-    throw new UnsupportedOperationException(s"$getClass.$methodName")
-
 }
diff --git a/compiler/src/dotty/tools/package.scala b/compiler/src/dotty/tools/package.scala
index d0501e53fed8..aace5e3e7da1 100644
--- a/compiler/src/dotty/tools/package.scala
+++ b/compiler/src/dotty/tools/package.scala
@@ -20,4 +20,8 @@ package object tools {
       }
     case _ => ys.isEmpty
   }
+
+  /** Throws an `UnsupportedOperationException` with the given method name. */
+  def unsupported(methodName: String): Nothing =
+    throw new UnsupportedOperationException(methodName)
 }