diff --git a/compiler/src/dotty/tools/dotc/reporting/MessageRendering.scala b/compiler/src/dotty/tools/dotc/reporting/MessageRendering.scala
index dfdcbde73a66..65443a2377e3 100644
--- a/compiler/src/dotty/tools/dotc/reporting/MessageRendering.scala
+++ b/compiler/src/dotty/tools/dotc/reporting/MessageRendering.scala
@@ -140,7 +140,8 @@ trait MessageRendering {
   /** The whole message rendered from `msg` */
   def messageAndPos(msg: Message, pos: SourcePosition, diagnosticLevel: String)(implicit ctx: Context): String = {
     val sb = mutable.StringBuilder.newBuilder
-    sb.append(posStr(pos, diagnosticLevel, msg)).append('\n')
+    val posString = posStr(pos, diagnosticLevel, msg)
+    if (posString.nonEmpty) sb.append(posString).append('\n')
     if (pos.exists) {
       val (srcBefore, srcAfter, offset) = sourceLines(pos)
       val marker = columnMarker(pos, offset)
diff --git a/compiler/src/dotty/tools/repl/ParseResult.scala b/compiler/src/dotty/tools/repl/ParseResult.scala
index 89e6a868eed0..7a16fa0a26ca 100644
--- a/compiler/src/dotty/tools/repl/ParseResult.scala
+++ b/compiler/src/dotty/tools/repl/ParseResult.scala
@@ -98,7 +98,9 @@ object ParseResult {
 
   @sharable private[this] val CommandExtract = """(:[\S]+)\s*(.*)""".r
 
-  private def parseStats(parser: Parser): List[untpd.Tree] = {
+  private def parseStats(sourceCode: String)(implicit ctx: Context): List[untpd.Tree] = {
+    val source = new SourceFile("<console>", sourceCode.toCharArray)
+    val parser = new Parser(source)
     val stats = parser.blockStatSeq()
     parser.accept(Tokens.EOF)
     stats
@@ -118,10 +120,7 @@ object ParseResult {
         case _ => UnknownCommand(cmd)
       }
       case _ => {
-        val source = new SourceFile("<console>", sourceCode.toCharArray)
-        val parser = new Parser(source)
-
-        val stats = parseStats(parser)
+        val stats = parseStats(sourceCode)
 
         if (ctx.reporter.hasErrors) {
           SyntaxErrors(sourceCode,
@@ -145,9 +144,7 @@ object ParseResult {
         val reporter = storeReporter
         var needsMore = false
         reporter.withIncompleteHandler(_ => _ => needsMore = true) {
-          val source = new SourceFile("<console>", sourceCode.toCharArray)
-          val parser = new Parser(source)(ctx.fresh.setReporter(reporter))
-          parseStats(parser)
+          parseStats(sourceCode)(ctx.fresh.setReporter(reporter))
           !reporter.hasErrors && needsMore
         }
       }
diff --git a/compiler/src/dotty/tools/repl/ReplCompiler.scala b/compiler/src/dotty/tools/repl/ReplCompiler.scala
index cf220fd58ae7..579ef637315b 100644
--- a/compiler/src/dotty/tools/repl/ReplCompiler.scala
+++ b/compiler/src/dotty/tools/repl/ReplCompiler.scala
@@ -33,7 +33,7 @@ class ReplCompiler(val directory: AbstractFile) extends Compiler {
 
   /** A GenBCode phase that outputs to a virtual directory */
   private class REPLGenBCode extends GenBCode {
-    override def phaseName = "replGenBCode"
+    override def phaseName = "genBCode"
     override def outputDir(implicit ctx: Context) = directory
   }
 
@@ -51,6 +51,25 @@ class ReplCompiler(val directory: AbstractFile) extends Compiler {
     )
   }
 
+  def newRun(initCtx: Context, objectIndex: Int) = new Run(this, initCtx) {
+    override protected[this] def rootContext(implicit ctx: Context) =
+      addMagicImports(super.rootContext.fresh.setReporter(storeReporter))
+
+    private def addMagicImports(initCtx: Context): Context = {
+      def addImport(path: TermName)(implicit ctx: Context) = {
+        val importInfo = ImportInfo.rootImport { () =>
+          ctx.requiredModuleRef(path)
+        }
+        ctx.fresh.setNewScope.setImportInfo(importInfo)
+      }
+
+      (1 to objectIndex)
+        .foldLeft(addImport("dotty.Show".toTermName)(initCtx)) { (ictx, i) =>
+          addImport(nme.EMPTY_PACKAGE ++ "." ++ objectNames(i))(ictx)
+        }
+    }
+  }
+
   private[this] var objectNames = Map.empty[Int, TermName]
   private def objectName(state: State) =
     objectNames.get(state.objectIndex).getOrElse {
@@ -59,9 +78,9 @@ class ReplCompiler(val directory: AbstractFile) extends Compiler {
       newName
     }
 
-  sealed case class Definitions(stats: List[untpd.Tree], state: State)
+  private case class Definitions(stats: List[untpd.Tree], state: State)
 
-  def definitions(trees: List[untpd.Tree], state: State): Result[Definitions] = {
+  private def definitions(trees: List[untpd.Tree], state: State): Definitions = {
     import untpd._
 
     implicit val ctx: Context = state.run.runContext
@@ -80,7 +99,7 @@ class ReplCompiler(val directory: AbstractFile) extends Compiler {
 
     def createPatDefShows(patDef: PatDef) = {
       def createDeepShows(tree: untpd.Tree) = {
-        object PatFolder extends UntypedDeepFolder[List[DefDef]] (
+        class PatFolder extends UntypedDeepFolder[List[DefDef]] (
           (acc, tree) => tree match {
             case Ident(name) if name.isVariableName && name != nme.WILDCARD =>
               createShow(name.toTermName, tree.pos) :: acc
@@ -90,7 +109,7 @@ class ReplCompiler(val directory: AbstractFile) extends Compiler {
               acc
           }
         )
-        PatFolder.apply(Nil, tree).reverse
+        (new PatFolder).apply(Nil, tree).reverse
       }
 
       // cannot fold over the whole tree because we need to generate show methods
@@ -130,12 +149,12 @@ class ReplCompiler(val directory: AbstractFile) extends Compiler {
     }
 
     Definitions(
-      state.imports.map(_._1) ++ defs,
+      state.imports ++ defs,
       state.copy(
         objectIndex = state.objectIndex + (if (defs.isEmpty) 0 else 1),
         valIndex = valIdx
       )
-    ).result
+    )
   }
 
   /** Wrap trees in an object and add imports from the previous compilations
@@ -153,65 +172,40 @@ class ReplCompiler(val directory: AbstractFile) extends Compiler {
    *  }
    *  ```
    */
-  def wrapped(defs: Definitions, sourceCode: String): untpd.PackageDef = {
+  private def wrapped(defs: Definitions): untpd.PackageDef = {
     import untpd._
 
-    implicit val ctx: Context = defs.state.run.runContext
+    assert(defs.stats.nonEmpty)
 
-    val module = {
-      val tmpl = Template(emptyConstructor(ctx), Nil, EmptyValDef, defs.stats)
-      List(
-        ModuleDef(objectName(defs.state), tmpl)
-          .withMods(new Modifiers(Module | Final))
-          .withPos(Position(0, sourceCode.length))
-      )
-    }
+    implicit val ctx: Context = defs.state.run.runContext
 
-    PackageDef(Ident(nme.EMPTY_PACKAGE), module)
-  }
+    val tmpl = Template(emptyConstructor, Nil, EmptyValDef, defs.stats)
+    val module = ModuleDef(objectName(defs.state), tmpl)
+      .withMods(new Modifiers(Module | Final))
+      .withPos(Position(0, defs.stats.last.pos.end))
 
-  def newRun(initCtx: Context, objectIndex: Int) = new Run(this, initCtx) {
-    override protected[this] def rootContext(implicit ctx: Context) =
-      addMagicImports(super.rootContext.fresh.setReporter(storeReporter), objectIndex)
+    PackageDef(Ident(nme.EMPTY_PACKAGE), List(module))
   }
 
-  def createUnit(defs: Definitions, sourceCode: String): Result[CompilationUnit] = {
+  private def createUnit(defs: Definitions, sourceCode: String): CompilationUnit = {
     val unit = new CompilationUnit(new SourceFile(objectName(defs.state).toString, sourceCode))
-    unit.untpdTree = wrapped(defs, sourceCode)
-    unit.result
+    unit.untpdTree = wrapped(defs)
+    unit
   }
 
-  def runCompilation(unit: CompilationUnit, state: State): Result[State] = {
+  private def runCompilationUnit(unit: CompilationUnit, state: State): Result[(CompilationUnit, State)] = {
     val run = state.run
     val reporter = state.run.runContext.reporter
     run.compileUnits(unit :: Nil)
 
-    if (!reporter.hasErrors) state.result
+    if (!reporter.hasErrors) (unit, state).result
     else run.runContext.flushBufferedMessages().errors
   }
 
   def compile(parsed: Parsed)(implicit state: State): Result[(CompilationUnit, State)] = {
-    for {
-      defs  <- definitions(parsed.trees, state)
-      unit  <- createUnit(defs, parsed.sourceCode)
-      state <- runCompilation(unit, defs.state)
-    } yield (unit, state)
-  }
-
-  private[this] def addMagicImports(initCtx: Context, objectIndex: Int): Context = {
-    def addImport(path: TermName)(implicit ctx: Context) = {
-      val ref = tpd.ref(ctx.requiredModuleRef(path.toTermName))
-      val symbol = ctx.newImportSymbol(ctx.owner, ref)
-      val importInfo =
-        new ImportInfo(implicit ctx => symbol, untpd.Ident(nme.WILDCARD) :: Nil, None)
-      ctx.fresh.setNewScope.setImportInfo(importInfo)
-    }
-
-    List
-      .range(1, objectIndex + 1)
-      .foldLeft(addImport("dotty.Show".toTermName)(initCtx)) { (ictx, i) =>
-        addImport(nme.EMPTY_PACKAGE ++ "." ++ objectNames(i))(ictx)
-      }
+    val defs = definitions(parsed.trees, state)
+    val unit = createUnit(defs, parsed.sourceCode)
+    runCompilationUnit(unit, defs.state)
   }
 
   def typeOf(expr: String)(implicit state: State): Result[String] =
@@ -223,7 +217,7 @@ class ReplCompiler(val directory: AbstractFile) extends Compiler {
         case _ =>
           """Couldn't compute the type of your expression, so sorry :(
             |
-            |Please report this to my masters at Github.com/lampepfl/dotty
+            |Please report this to my masters at github.com/lampepfl/dotty
           """.stripMargin
       }
     }
@@ -240,7 +234,7 @@ class ReplCompiler(val directory: AbstractFile) extends Compiler {
         val tmpl = Template(emptyConstructor,
                             List(Ident(tpnme.Any)),
                             EmptyValDef,
-                            state.imports.map(_._1) :+ valdef)
+                            state.imports :+ valdef)
 
         PackageDef(Ident(nme.EMPTY_PACKAGE),
           TypeDef("EvaluateExpr".toTypeName, tmpl)
@@ -286,7 +280,7 @@ class ReplCompiler(val directory: AbstractFile) extends Compiler {
     val src = new SourceFile(s"EvaluateExpr", expr)
     val runCtx =
       run.runContext.fresh
-         .setSetting(run.runContext.settings.YstopAfter, List("replFrontEnd"))
+         .setSetting(run.runContext.settings.YstopAfter, List("frontend"))
 
     wrapped(expr, src, state)(runCtx).flatMap { pkg =>
       val unit = new CompilationUnit(src)
diff --git a/compiler/src/dotty/tools/repl/ReplDriver.scala b/compiler/src/dotty/tools/repl/ReplDriver.scala
index 4f5c01505c5f..14f96438509d 100644
--- a/compiler/src/dotty/tools/repl/ReplDriver.scala
+++ b/compiler/src/dotty/tools/repl/ReplDriver.scala
@@ -25,7 +25,10 @@ import dotc.core.NameKinds.SimpleNameKind
 import dotc.config.CompilerCommand
 import dotc.{ Compiler, Driver }
 import dotc.printing.SyntaxHighlighting
+import dotc.reporting.diagnostic.Message
 import dotc.util.Positions.Position
+import dotc.util.SourcePosition
+
 import io._
 
 import AmmoniteReader._
@@ -56,7 +59,7 @@ import results._
 case class State(objectIndex: Int,
                  valIndex: Int,
                  history: History,
-                 imports: List[(untpd.Import, String)],
+                 imports: List[untpd.Import],
                  run: Run) {
 
   def withHistory(newEntry: String) = copy(history = newEntry :: history)
@@ -184,8 +187,8 @@ class ReplDriver(settings: Array[String],
   private def readLine()(implicit state: State): ParseResult =
     AmmoniteReader(out, state.history, completions(_, _, state))(state.run.runContext).prompt
 
-  private def extractImports(trees: List[untpd.Tree])(implicit context: Context): List[(untpd.Import, String)] =
-    trees.collect { case imp: untpd.Import => (imp, imp.show) }
+  private def extractImports(trees: List[untpd.Tree]): List[untpd.Import] =
+    trees.collect { case imp: untpd.Import => imp }
 
   private def interpret(res: ParseResult)(implicit state: State): State =
     res match {
@@ -223,7 +226,7 @@ class ReplDriver(settings: Array[String],
         {
           case (unit: CompilationUnit, newState: State) => {
             val newestWrapper = extractNewestWrapper(unit.untpdTree)
-            val newImports = newState.imports ++ extractImports(parsed.trees)(newState.run.runContext)
+            val newImports = newState.imports ++ extractImports(parsed.trees)
             val newStateWithImports = newState.copy(imports = newImports)
 
             displayDefinitions(unit.tpdTree, newestWrapper)(newStateWithImports)
@@ -323,7 +326,7 @@ class ReplDriver(settings: Array[String],
     }
 
     case Imports => {
-      state.imports foreach { case (_, i) => println(SyntaxHighlighting(i)) }
+      state.imports.foreach(i => out.println(SyntaxHighlighting(i.show(state.run.runContext))))
       state.withHistory(Imports.command)
     }
 
@@ -361,18 +364,7 @@ class ReplDriver(settings: Array[String],
 
   /** A `MessageRenderer` without file positions */
   private val messageRenderer = new MessageRendering {
-    import dotc.reporting.diagnostic._
-    import dotc.util._
-    override def messageAndPos(msg: Message, pos: SourcePosition, diagnosticLevel: String)(implicit ctx: Context): String = {
-      val sb = scala.collection.mutable.StringBuilder.newBuilder
-      if (pos.exists) {
-        val (srcBefore, srcAfter, offset) = sourceLines(pos)
-        val marker = columnMarker(pos, offset)
-        val err = errorMsg(pos, msg.msg, offset)
-        sb.append((srcBefore ::: marker :: err :: outer(pos, " " * (offset - 1)) ::: srcAfter).mkString("\n"))
-      }
-      sb.toString
-    }
+    override def posStr(pos: SourcePosition, diagnosticLevel: String, message: Message)(implicit ctx: Context): String = ""
   }
 
   /** Render messages using the `MessageRendering` trait */
diff --git a/compiler/src/dotty/tools/repl/ReplFrontEnd.scala b/compiler/src/dotty/tools/repl/ReplFrontEnd.scala
index e02053dacd92..da950eafb44b 100644
--- a/compiler/src/dotty/tools/repl/ReplFrontEnd.scala
+++ b/compiler/src/dotty/tools/repl/ReplFrontEnd.scala
@@ -12,19 +12,17 @@ import dotc.core.Contexts.Context
  *  compiler pipeline.
  */
 private[repl] class REPLFrontEnd extends FrontEnd {
-  override def phaseName = "replFrontEnd"
+  override def phaseName = "frontend"
 
   override def isRunnable(implicit ctx: Context) = true
 
   override def runOn(units: List[CompilationUnit])(implicit ctx: Context) = {
-    val unitContexts = for (unit <- units) yield ctx.fresh.setCompilationUnit(unit)
-    var remaining = unitContexts
-    while (remaining.nonEmpty) {
-      enterSyms(remaining.head)
-      remaining = remaining.tail
-    }
-    unitContexts.foreach(enterAnnotations(_))
-    unitContexts.foreach(typeCheck(_))
-    unitContexts.map(_.compilationUnit).filterNot(discardAfterTyper)
+    assert(units.size == 1) // REPl runs one compilation unit at a time
+
+    val unitContext = ctx.fresh.setCompilationUnit(units.head)
+    enterSyms(unitContext)
+    enterAnnotations(unitContext)
+    typeCheck(unitContext)
+    List(unitContext.compilationUnit)
   }
 }
diff --git a/compiler/test-resources/repl/patdef b/compiler/test-resources/repl/patdef
index a6ebf9688fde..c7ca5d287ce7 100644
--- a/compiler/test-resources/repl/patdef
+++ b/compiler/test-resources/repl/patdef
@@ -22,5 +22,5 @@ val x: Int = 1
 scala> val List(_ @ List(x)) = List(List(2))
 val x: Int = 2
 scala> val B @ List(), C: List[Int] = List()
-val B: List[Int] = Nil
-val C: List[Int] = Nil
+val B: List[Int] = List()
+val C: List[Int] = List()
diff --git a/dist/bin/dotr b/dist/bin/dotr
index 568f201f38ad..7b14f243e1b3 100755
--- a/dist/bin/dotr
+++ b/dist/bin/dotr
@@ -60,7 +60,7 @@ if [ $run_repl == true ] || [ ${#residual_args[@]} -eq 0 ]; then
   if [ "$CLASS_PATH" ]; then
     cp_arg="-classpath $CLASS_PATH"
   fi
-  echo "Starting dotty REPL"
+  echo "Starting dotty REPL..."
   eval "$PROG_HOME/bin/dotc $cp_arg -repl ${residual_args[@]}"
 else
   cp_arg="-classpath $DOTTY_LIB$PSEP$SCALA_LIB"
diff --git a/library/src/dotty/Show.scala b/library/src/dotty/Show.scala
index 2feeb29efbcc..64794e7955c9 100644
--- a/library/src/dotty/Show.scala
+++ b/library/src/dotty/Show.scala
@@ -28,21 +28,22 @@ object Show {
   implicit val stringShow: Show[String] = new Show[String] {
     // From 2.12 spec, `charEscapeSeq`:
     // ‘\‘ (‘b‘ | ‘t‘ | ‘n‘ | ‘f‘ | ‘r‘ | ‘"‘ | ‘'‘ | ‘\‘)
-    def show(str: String) =
-      "\"" + {
-        val sb = new StringBuilder
-        str.foreach {
-          case '\b' => sb.append("\\b")
-          case '\t' => sb.append("\\t")
-          case '\n' => sb.append("\\n")
-          case '\f' => sb.append("\\f")
-          case '\r' => sb.append("\\r")
-          case '\'' => sb.append("\\'")
-          case '\"' => sb.append("\\\"")
-          case c => sb.append(c)
-        }
-        sb.toString
-      } + "\""
+    def show(str: String) = {
+      val sb = new StringBuilder
+      sb.append("\"")
+      str.foreach {
+        case '\b' => sb.append("\\b")
+        case '\t' => sb.append("\\t")
+        case '\n' => sb.append("\\n")
+        case '\f' => sb.append("\\f")
+        case '\r' => sb.append("\\r")
+        case '\'' => sb.append("\\'")
+        case '\"' => sb.append("\\\"")
+        case c => sb.append(c)
+      }
+      sb.append("\"")
+      sb.toString
+    }
   }
 
   implicit val intShow: Show[Int] = new Show[Int] {
@@ -72,12 +73,12 @@ object Show {
 
   implicit def showList[T](implicit st: Show[T]): Show[List[T]] = new Show[List[T]] {
     def show(xs: List[T]) =
-      if (xs.isEmpty) "Nil"
+      if (xs.isEmpty) "List()"
       else "List(" + xs.map(_.show).mkString(", ") + ")"
   }
 
   implicit val showNil: Show[Nil.type] = new Show[Nil.type] {
-    def show(xs: Nil.type) = "Nil"
+    def show(xs: Nil.type) = "List()"
   }
 
   implicit def showOption[T](implicit st: Show[T]): Show[Option[T]] = new Show[Option[T]] {