No warn when discarding r.f(): r.type

The paradigm is `def add(x: X): Unit = listBuffer += x`.

The value that is discarded is not new information.

Also cleans up the recent tweaks to help messaging.

Adds newlines in case they ask for multiple helps.

5 files changed, 17 insertions, 21 deletions

diff --git a/src/compiler/scala/tools/nsc/CompilerCommand.scala b/src/compiler/scala/tools/nsc/CompilerCommand.scala
index 3879d7b425..24da6ba487 100644
--- a/src/compiler/scala/tools/nsc/CompilerCommand.scala
+++ b/src/compiler/scala/tools/nsc/CompilerCommand.scala
@@ -103,15 +103,7 @@ class CompilerCommand(arguments: List[String], val settings: Settings) {
       val components = global.phaseNames  // global.phaseDescriptors // one initializes
       s"Phase graph of ${components.size} components output to ${genPhaseGraph.value}*.dot."
     }
-    // would be nicer if we could ask all the options for their helpful messages
-    else {
-      val sb = new StringBuilder
-      allSettings foreach {
-        case s if s.isHelping => sb append s.help
-        case _ =>
-      }
-      sb.toString
-    }
+    else allSettings.filter(_.isHelping).map(_.help).mkString("\n\n")
   }
 
   /**
diff --git a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
index e10fa3a114..d81d688267 100644
--- a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
@@ -38,11 +38,8 @@ trait ScalaSettings extends AbsScalaSettings
   /** If any of these settings is enabled, the compiler should print a message and exit.  */
   def infoSettings = List[Setting](version, help, Xhelp, Yhelp, showPlugins, showPhases, genPhaseGraph)
 
-  /** Any -option:help? */
-  private def multihelp = allSettings exists { case s => s.isHelping case _ => false }
-
-  /** Is an info setting set? */
-  def isInfo = (infoSettings exists (_.isSetByUser)) || multihelp
+  /** Is an info setting set? Any -option:help? */
+  def isInfo = infoSettings.exists(_.isSetByUser) || allSettings.exists(_.isHelping)
 
   /** Disable a setting */
   def disable(s: Setting) = allSettings -= s
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index d8183ea8df..7d48c548a1 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -1060,8 +1060,13 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
           @inline def tpdPos(transformed: Tree) = typedPos(tree.pos, mode, pt)(transformed)
           @inline def tpd(transformed: Tree)    = typed(transformed, mode, pt)
 
-          @inline def warnValueDiscard(): Unit =
-            if (!isPastTyper && settings.warnValueDiscard) context.warning(tree.pos, "discarded non-Unit value")
+          @inline def warnValueDiscard(): Unit = if (!isPastTyper && settings.warnValueDiscard) {
+            def isThisTypeResult = (tree, tree.tpe) match {
+              case (Apply(Select(receiver, _), _), SingleType(_, sym)) => sym == receiver.symbol
+              case _ => false
+            }
+            if (!isThisTypeResult) context.warning(tree.pos, "discarded non-Unit value")
+          }
           @inline def warnNumericWiden(): Unit =
             if (!isPastTyper && settings.warnNumericWiden) context.warning(tree.pos, "implicit numeric widening")
 
diff --git a/src/repl/scala/tools/nsc/MainGenericRunner.scala b/src/repl/scala/tools/nsc/MainGenericRunner.scala
index a09e797e07..894157ff6c 100644
--- a/src/repl/scala/tools/nsc/MainGenericRunner.scala
+++ b/src/repl/scala/tools/nsc/MainGenericRunner.scala
@@ -49,10 +49,6 @@ class MainGenericRunner {
       def isI   = !settings.loadfiles.isDefault
       def dashi = settings.loadfiles.value
 
-      // Deadlocks on startup under -i unless we disable async.
-      if (isI)
-        settings.Yreplsync.value = true
-
       def combinedCode  = {
         val files   = if (isI) dashi map (file => File(file).slurp()) else Nil
         val str     = if (isE) List(dashe) else Nil
@@ -98,7 +94,7 @@ class MainGenericRunner {
     if (!command.ok)
       errorFn(f"%n$shortUsageMsg")
     else if (shouldStopWithInfo)
-      errorFn(command getInfoMessage sampleCompiler, isFailure = false)
+      errorFn(command.getInfoMessage(sampleCompiler), isFailure = false)
     else
       run()
   }
diff --git a/test/files/pos/t9020.scala b/test/files/pos/t9020.scala
index 16e31e2572..c77a63cb1a 100644
--- a/test/files/pos/t9020.scala
+++ b/test/files/pos/t9020.scala
@@ -8,3 +8,9 @@ test/files/pos/t9020.scala:2: warning: discarded non-Unit value
       ^
 one warning found
 */
+
+trait DiscardThis {
+  import collection.mutable.ListBuffer
+  val b = ListBuffer.empty[String]
+  def add(s: String): Unit = b += s
+}