diff --git a/compiler/src/dotty/tools/dotc/printing/DecompilerPrinter.scala b/compiler/src/dotty/tools/dotc/printing/DecompilerPrinter.scala
index 392d719cfefd..9e3c520985de 100644
--- a/compiler/src/dotty/tools/dotc/printing/DecompilerPrinter.scala
+++ b/compiler/src/dotty/tools/dotc/printing/DecompilerPrinter.scala
@@ -1,12 +1,13 @@
 package dotty.tools.dotc.printing
 
-import dotty.tools.dotc.ast.Trees.{Closure, DefDef, Untyped, ValDef}
+import dotty.tools.dotc.ast.Trees._
 import dotty.tools.dotc.ast.untpd.{PackageDef, Template, TypeDef}
 import dotty.tools.dotc.ast.{Trees, untpd}
 import dotty.tools.dotc.printing.Texts._
 import dotty.tools.dotc.core.Contexts._
 import dotty.tools.dotc.core.Flags._
 import dotty.tools.dotc.core.Symbols._
+import dotty.tools.dotc.core.StdNames._
 
 import scala.language.implicitConversions
 
@@ -16,7 +17,13 @@ class DecompilerPrinter(_ctx: Context) extends RefinedPrinter(_ctx) {
     annots.filter(_.tpe != defn.SourceFileAnnotType)
 
   override protected def blockText[T >: Untyped](trees: List[Trees.Tree[T]]): Text = {
-    super.blockText(trees.filterNot(_.isInstanceOf[Closure[_]]))
+    trees match {
+      case DefDef(_, _, _, _, Trees.If(cond, Trees.Block(body :: Nil, _), _)) :: y :: Nil if y.symbol.name == nme.WHILE_PREFIX =>
+        keywordText("while") ~ " (" ~ toText(cond) ~ ")" ~ toText(body)
+      case DefDef(_, _, _, _, Trees.Block(body :: Nil, Trees.If(cond, _, _))) :: y :: Nil if y.symbol.name == nme.DO_WHILE_PREFIX =>
+        keywordText("do") ~ toText(body) ~ keywordText("while") ~ " (" ~ toText(cond) ~ ")"
+      case _ => super.blockText(trees.filterNot(_.isInstanceOf[Closure[_]]))
+    }
   }
 
   override protected def packageDefText(tree: PackageDef): Text = {
@@ -29,8 +36,10 @@ class DecompilerPrinter(_ctx: Context) extends RefinedPrinter(_ctx) {
       case _ => toTextGlobal(stats, "\n")
     }
     val bodyText =
-      if (currentPrecedence == TopLevelPrec) "\n" ~ statsText else " {" ~ statsText ~ "}"
-    keywordStr("package ") ~ toTextPackageId(tree.pid) ~ bodyText
+      if (tree.pid.symbol.isEmptyPackage) statsText
+      else if (currentPrecedence == TopLevelPrec) "\n" ~ statsText
+      else " {" ~ statsText ~ "}"
+    (keywordStr("package ") ~ toTextPackageId(tree.pid)).provided(!tree.symbol.isEmptyPackage) ~ bodyText
   }
 
   override protected def templateText(tree: TypeDef, impl: Template): Text = {
@@ -40,6 +49,11 @@ class DecompilerPrinter(_ctx: Context) extends RefinedPrinter(_ctx) {
     decl ~~ typeText(nameIdText(tree)) ~ withEnclosingDef(tree) { toTextTemplate(impl) } ~ ""
   }
 
+  override protected def toTextTemplate(impl: Template, ofNew: Boolean = false): Text = {
+    val impl1 = impl.copy(parents = impl.parents.filterNot(_.symbol.maybeOwner == defn.ObjectClass))
+    super.toTextTemplate(impl1, ofNew)
+  }
+
   override protected def defDefToText[T >: Untyped](tree: DefDef[T]): Text = {
     import untpd.{modsDeco => _, _}
     dclTextOr(tree) {
diff --git a/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala b/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala
index 48bc992f8a47..1c1e05e5404e 100644
--- a/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala
+++ b/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala
@@ -654,7 +654,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
 
     val bodyText = "{" ~~ selfText ~~ toTextGlobal(primaryConstrs ::: body, "\n") ~ "}"
 
-    prefix ~ (keywordText(" extends") provided !ofNew) ~~ parentsText ~~ bodyText
+    prefix ~ (keywordText(" extends") provided (!ofNew && parents.nonEmpty)) ~~ parentsText ~~ bodyText
   }
 
   protected def templateText(tree: TypeDef, impl: Template): Text = {
diff --git a/tests/pos/lambda.decompiled b/tests/pos/lambda.decompiled
index e44e5770633a..b201feba55cc 100644
--- a/tests/pos/lambda.decompiled
+++ b/tests/pos/lambda.decompiled
@@ -2,7 +2,7 @@
 out/posTestFromTasty/pos/lambda/foo/Foo.class
 --------------------------------------------------------------------------------
 package foo {
-  class Foo() extends Object() {
+  class Foo() {
     val a: Int => Int =
       {
         (x: Int) => x.*(x)
diff --git a/tests/pos/methodTypes.decompiled b/tests/pos/methodTypes.decompiled
index 8b49ab2b402e..40cc677c5c03 100644
--- a/tests/pos/methodTypes.decompiled
+++ b/tests/pos/methodTypes.decompiled
@@ -1,11 +1,9 @@
 ================================================================================
 out/posTestFromTasty/pos/methodTypes/Foo.class
 --------------------------------------------------------------------------------
-package <empty> {
-  class Foo() extends Object() {
-    val x: Int = 1
-    def y: Int = 2
-    def z(): Int = 3
-  }
+class Foo() {
+  val x: Int = 1
+  def y: Int = 2
+  def z(): Int = 3
 }
 --------------------------------------------------------------------------------
\ No newline at end of file
diff --git a/tests/pos/simpleCaseObject.decompiled b/tests/pos/simpleCaseObject.decompiled
index 1ecd3759cb65..0692b8d5ac8b 100644
--- a/tests/pos/simpleCaseObject.decompiled
+++ b/tests/pos/simpleCaseObject.decompiled
@@ -2,9 +2,7 @@
 out/posTestFromTasty/pos/simpleCaseObject/foo/Foo.class
 --------------------------------------------------------------------------------
 package foo {
-  case object Foo() extends Object() with _root_.scala.Product {
-    this: foo.Foo.type =>
-
+  case object Foo() extends _root_.scala.Product { this: foo.Foo.type =>
     override def hashCode(): Int = 1045991777
     override def toString(): String = "Foo"
     override def canEqual(that: Any): Boolean = that.isInstanceOf[foo.Foo]
diff --git a/tests/pos/simpleClass-2.decompiled b/tests/pos/simpleClass-2.decompiled
index 78291f123ca2..23e04b8e8701 100644
--- a/tests/pos/simpleClass-2.decompiled
+++ b/tests/pos/simpleClass-2.decompiled
@@ -9,6 +9,6 @@ package foo {
 out/posTestFromTasty/pos/simpleClass-2/foo/B.class
 --------------------------------------------------------------------------------
 package foo {
-  class B() extends Object() {}
+  class B() {}
 }
 --------------------------------------------------------------------------------
\ No newline at end of file
diff --git a/tests/pos/simpleClass.decompiled b/tests/pos/simpleClass.decompiled
index f671605a89c7..814df8bceddc 100644
--- a/tests/pos/simpleClass.decompiled
+++ b/tests/pos/simpleClass.decompiled
@@ -2,7 +2,7 @@
 out/posTestFromTasty/pos/simpleClass/foo/A.class
 --------------------------------------------------------------------------------
 package foo {
-  class A() extends Object() {}
+  class A() {}
 }
 --------------------------------------------------------------------------------
 ================================================================================
diff --git a/tests/pos/simpleDoWhile.decompiled b/tests/pos/simpleDoWhile.decompiled
new file mode 100644
index 000000000000..811801631451
--- /dev/null
+++ b/tests/pos/simpleDoWhile.decompiled
@@ -0,0 +1,15 @@
+================================================================================
+out/posTestFromTasty/pos/simpleDoWhile/Foo.class
+--------------------------------------------------------------------------------
+class Foo() {
+  def foo: Unit =
+    {
+      var i: Int = 1
+      do
+        {
+          i = 0
+        }
+      while (i.!=(0))
+    }
+}
+--------------------------------------------------------------------------------
\ No newline at end of file
diff --git a/tests/pos/simpleDoWhile.scala b/tests/pos/simpleDoWhile.scala
new file mode 100644
index 000000000000..37419dc5d064
--- /dev/null
+++ b/tests/pos/simpleDoWhile.scala
@@ -0,0 +1,8 @@
+class Foo {
+  def foo = {
+    var i = 1
+    do {
+      i = 0
+    } while (i != 0)
+  }
+}
diff --git a/tests/pos/simpleWhile.decompiled b/tests/pos/simpleWhile.decompiled
new file mode 100644
index 000000000000..8ae185525386
--- /dev/null
+++ b/tests/pos/simpleWhile.decompiled
@@ -0,0 +1,14 @@
+================================================================================
+out/posTestFromTasty/pos/simpleWhile/Foo.class
+--------------------------------------------------------------------------------
+class Foo() {
+  def foo: Unit =
+    {
+      var i: Int = 1
+      while (i.!=(0))
+        {
+          i = 0
+        }
+    }
+}
+--------------------------------------------------------------------------------
\ No newline at end of file
diff --git a/tests/pos/simpleWhile.scala b/tests/pos/simpleWhile.scala
new file mode 100644
index 000000000000..a70399f0aaa7
--- /dev/null
+++ b/tests/pos/simpleWhile.scala
@@ -0,0 +1,8 @@
+class Foo {
+  def foo = {
+    var i = 1
+    while (i != 0) {
+      i = 0
+    }
+  }
+}
diff --git a/tests/run/puzzle.decompiled b/tests/run/puzzle.decompiled
index 4ce0c2cc3891..870c215b4a1d 100644
--- a/tests/run/puzzle.decompiled
+++ b/tests/run/puzzle.decompiled
@@ -1,17 +1,15 @@
 ================================================================================
 out/runTestFromTasty/run/puzzle/Test.class
 --------------------------------------------------------------------------------
-package <empty> {
-  object Test() extends Object() { this: Test.type =>
-    def main(args: Array[String]): Unit =
-      {
-        println(if false then 5.0 else 53.0)
-        val x: Double = if false then 5.0 else 53.0
-        println(x)
-        val z: Long = 1L
-        val y: Float = Long.long2float(z)
-        ()
-      }
-  }
+object Test() { this: Test.type =>
+  def main(args: Array[String]): Unit =
+    {
+      println(if false then 5.0 else 53.0)
+      val x: Double = if false then 5.0 else 53.0
+      println(x)
+      val z: Long = 1L
+      val y: Float = Long.long2float(z)
+      ()
+    }
 }
 --------------------------------------------------------------------------------
\ No newline at end of file