Fix error messages not being doubled and being on a new line

Author: felixmulder

src/dotty/tools/dotc/repl/CompilingInterpreter.scala

@@ -80,15 +80,13 @@ class CompilingInterpreter(out: PrintWriter, ictx: Context) extends Compiler wit
   private var printResults: Boolean = true
   private var delayOutput: Boolean = false
 
-  var previousOutput: String = null
-
-  override def lastOutput() =
-    if (previousOutput == null) None
-    else {
-      val ret = Some(previousOutput)
-      previousOutput = null
-      ret
-    }
+  var previousOutput: List[String] = Nil
+
+  override def lastOutput() = {
+    val prev = previousOutput
+    previousOutput = Nil
+    prev
+  }
 
   override def delayOutputDuring[T](operation: => T): T = {
     val old = delayOutput
@@ -113,14 +111,18 @@ class CompilingInterpreter(out: PrintWriter, ictx: Context) extends Compiler wit
 
   private def newReporter = new ConsoleReporter(Console.in, out) {
     override def printMessage(msg: String) = {
-      out.print(/*clean*/(msg) + "\n")
-        // Suppress clean for now for compiler messages
-        // Otherwise we will completely delete all references to
-        // line$object$ module classes. The previous interpreter did not
-        // have the project because the module class was written without the final `$'
-        // and therefore escaped the purge. We can turn this back on once
-        // we drop the final `$' from module classes.
-      out.flush()
+      if (!delayOutput) {
+        out.print(/*clean*/(msg) + "\n")
+          // Suppress clean for now for compiler messages
+          // Otherwise we will completely delete all references to
+          // line$object$ module classes. The previous interpreter did not
+          // have the project because the module class was written without the final `$'
+          // and therefore escaped the purge. We can turn this back on once
+          // we drop the final `$' from module classes.
+        out.flush()
+      } else {
+        previousOutput = (/*clean*/(msg) + "\n") :: previousOutput
+      }
     }
   }
 
@@ -210,7 +212,7 @@ class CompilingInterpreter(out: PrintWriter, ictx: Context) extends Compiler wit
         else {
           val (interpreterResultString, succeeded) = req.loadAndRun()
           if (delayOutput)
-            previousOutput = clean(interpreterResultString)
+            previousOutput = clean(interpreterResultString) :: previousOutput
           else if (printResults || !succeeded)
             out.print(clean(interpreterResultString))
           if (succeeded) {

src/dotty/tools/dotc/repl/Interpreter.scala

@@ -38,5 +38,5 @@ trait Interpreter {
   def delayOutputDuring[T](operation: => T): T
 
   /** Gets the last output not printed immediately */
-  def lastOutput(): Option[String]
+  def lastOutput(): List[String]
 }

src/dotty/tools/dotc/repl/InterpreterLoop.scala

@@ -167,10 +167,10 @@ class InterpreterLoop(compiler: Compiler, config: REPL.Config)(implicit ctx: Con
       output.println("Unknown command.  Type :help for help.")
     else
       shouldReplay = interpreter.lastOutput() match { // don't interpret twice
-        case Some(oldRes) =>
-          output.print(oldRes)
+        case Nil => interpretStartingWith(line)
+        case oldRes =>
+          oldRes foreach output.print
           Some(line)
-        case None => interpretStartingWith(line)
       }
 
     (true, shouldReplay)