Digging into why the repl is so slow, discovere...

Digging into why the repl is so slow, discovered that fsc is once again
never reusing compiler instances (but for a different reason than
#1683.) Small changes break equality and the little troopers are so darn
quiet about it. Steady state, hot fsc repl startup times before this
patch:

  0m1.747s 0m1.789s 0m1.842s 0m1.690s

After this patch:

  0m1.139s 0m1.148s 0m1.090s 0m1.091s

No review. Could use a test case but I have trouble coaxing partest this
far outside the box.

4 files changed, 67 insertions, 61 deletions

diff --git a/src/compiler/scala/tools/nsc/CompileServer.scala b/src/compiler/scala/tools/nsc/CompileServer.scala
index 67276b861f..36af000937 100644
--- a/src/compiler/scala/tools/nsc/CompileServer.scala
+++ b/src/compiler/scala/tools/nsc/CompileServer.scala
@@ -82,63 +82,70 @@ class StandardCompileServer extends SocketServer
     val password = compileSocket getPassword port
     val guessedPassword = in.readLine()
     val input = in.readLine()
-    if ((input ne null) && password == guessedPassword) {
-      val args = input.split("\0",-1).toList
-      if (args contains "-shutdown") {
-        out.println("[Compile server exited]")
-        shutDown = true
-        return
-      }
-      if (args contains "-reset") {
-        out.println("[Compile server was reset]")
-        compiler = null
-        return
-      }
-      def error(msg: String) {
-        out.println(/*new Position*/ FakePos("fsc"),
-                    msg + "\n  fsc -help  gives more information")
-      }
-      val command = newOfflineCompilerCommand(args, new Settings(error), error, false)
 
-      reporter = new ConsoleReporter(command.settings, in, out) {
-        // disable prompts, so that compile server cannot block
-        override def displayPrompt = ()
-      }
+    if (input == null || password != guessedPassword)
+      return
 
-      if (command.shouldStopWithInfo) {
-        reporter.info(null,
-                        command.getInfoMessage(newGlobal(command.settings, reporter)), true)
-        } else if (command.files.isEmpty)
-            reporter.info(null, command.usageMsg, true)
-          else {
-            try {
-              if ((compiler ne null) && settingsAreCompatible(command.settings, compiler.settings)) {
-                compiler.settings = command.settings
-                compiler.reporter = reporter
-              } else {
-                if (args contains "-verbose")
-                  out.println("[Starting new compile server instance]")
-                compiler = newGlobal(command.settings, reporter)
-              }
-              val c = compiler
-              val run = new c.Run()
-              run compile command.files
-            } catch {
-              case ex @ FatalError(msg) =>
-                if (command.settings.debug.value)
-                  ex.printStackTrace(out);
-              reporter.error(null, "fatal error: " + msg)
-              compiler = null
-              case ex: Throwable =>
-                ex.printStackTrace(out);
-              reporter.error(null, "fatal error (server aborted): " + ex.getMessage())
-              shutDown = true
-            }
-            reporter.printSummary()
-            if (isMemoryFullEnough)
-              compiler = null
+    val args = input.split("\0", -1).toList
+    if (args contains "-shutdown") {
+      out.println("[Compile server exited]")
+      shutDown = true
+      return
+    }
+    if (args contains "-reset") {
+      out.println("[Compile server was reset]")
+      compiler = null
+      return
+    }
+
+    def error(msg: String) {
+      out.println(FakePos("fsc"), msg + "\n  fsc -help  gives more information")
+    }
+
+    val command = newOfflineCompilerCommand(args, new Settings(error), error, false)
+
+    reporter = new ConsoleReporter(command.settings, in, out) {
+      // disable prompts, so that compile server cannot block
+      override def displayPrompt = ()
+    }
+
+    if (command.shouldStopWithInfo)
+      reporter.info(null, command.getInfoMessage(newGlobal(command.settings, reporter)), true)
+    else if (command.files.isEmpty)
+      reporter.info(null, command.usageMsg, true)
+    else {
+      try {
+        if (compiler != null && command.settings == compiler.settings) {
+          compiler.settings = command.settings
+          compiler.reporter = reporter
+        }
+        else {
+          if (args contains "-verbose") {
+            val reason = if (compiler == null) "compiler is null" else "settings not equal"
+            out.println("[Starting new compile server instance because %s]".format(reason))
           }
+          compiler = newGlobal(command.settings, reporter)
+        }
+        val c = compiler
+        val run = new c.Run()
+        run compile command.files
+      }
+      catch {
+        case ex @ FatalError(msg) =>
+          if (command.settings.debug.value)
+            ex.printStackTrace(out);
+        reporter.error(null, "fatal error: " + msg)
+        compiler = null
+        case ex: Throwable =>
+          ex.printStackTrace(out);
+        reporter.error(null, "fatal error (server aborted): " + ex.getMessage())
+        shutDown = true
+      }
     }
+
+    reporter.printSummary()
+    if (isMemoryFullEnough)
+      compiler = null
   }
 
   /** A directory holding redirected output */
diff --git a/src/compiler/scala/tools/nsc/CompilerCommand.scala b/src/compiler/scala/tools/nsc/CompilerCommand.scala
index 8465227133..75a3414d75 100644
--- a/src/compiler/scala/tools/nsc/CompilerCommand.scala
+++ b/src/compiler/scala/tools/nsc/CompilerCommand.scala
@@ -33,7 +33,7 @@ class CompilerCommand(
   val cmdName = "scalac"
 
   private val helpSyntaxColumnWidth: Int =
-    (settings.allSettings map (_.helpSyntax.length)) max
+    (settings.settingSet map (_.helpSyntax.length)) max
 
   private def format(s: String): String = {
     val buf = new StringBuilder(s)
@@ -44,7 +44,7 @@ class CompilerCommand(
 
   /** Creates a help message for a subset of options based on cond */
   def createUsageMsg(label: String, cond: (Setting) => Boolean): String =
-    settings.allSettings .
+    settings.settingSet .
       filter(cond) .
       map(s => format(s.helpSyntax) + "  " + s.helpDescription) .
       mkString("Usage: %s <options> <source files>\n%s options include:\n  " .
diff --git a/src/compiler/scala/tools/nsc/ScriptRunner.scala b/src/compiler/scala/tools/nsc/ScriptRunner.scala
index 3423f8f45f..f9d4d7983a 100644
--- a/src/compiler/scala/tools/nsc/ScriptRunner.scala
+++ b/src/compiler/scala/tools/nsc/ScriptRunner.scala
@@ -204,8 +204,8 @@ object ScriptRunner
       }
     }
 
-    val compSettingNames  = new Settings(error).allSettings map (_.name)
-    val compSettings      = settings.allSettings filter (compSettingNames contains _.name)
+    val compSettingNames  = new Settings(error).settingSet.toList map (_.name)
+    val compSettings      = settings.settingSet.toList filter (compSettingNames contains _.name)
     val coreCompArgs      = compSettings flatMap (_.unparse)
     val compArgs          = coreCompArgs ::: List("-Xscript", scriptMain(settings), scriptFile)
     var compok            = true
diff --git a/src/compiler/scala/tools/nsc/Settings.scala b/src/compiler/scala/tools/nsc/Settings.scala
index 157bc2dc1f..4242d0df47 100644
--- a/src/compiler/scala/tools/nsc/Settings.scala
+++ b/src/compiler/scala/tools/nsc/Settings.scala
@@ -61,9 +61,9 @@ class Settings(errorFn: String => Unit) extends ScalacSettings {
   private def guessedScalaExtDirs: Option[String] =
     guess(List("lib"), _.isDirectory)
 
-  override def hashCode() = allSettings.hashCode
+  override def hashCode() = settingSet.hashCode
   override def equals(that: Any) = that match {
-    case s: Settings  => this.allSettings == s.allSettings
+    case s: Settings  => this.settingSet == s.settingSet
     case _            => false
   }
 
@@ -75,7 +75,7 @@ class Settings(errorFn: String => Unit) extends ScalacSettings {
       case _ => "" == value
     }
 
-    for (setting <- allSettings ; (dep, value) <- setting.dependency)
+    for (setting <- settingSet ; (dep, value) <- setting.dependency)
       if (!setting.isDefault && !hasValue(dep, value)) {
         errorFn("incomplete option " + setting.name + " (requires " + dep.name + ")")
         return false
@@ -811,7 +811,6 @@ trait ScalacSettings {
   /** A list of all settings */
   protected var allsettings: Set[Setting] = TreeSet[Setting]()
   def settingSet: Set[Setting] = allsettings
-  def allSettings: List[Setting] = settingSet.toList
 
   /** Disable a setting */
   def disable(s: Setting) = allsettings -= s