Disables NotNull checking unless -Ynotnull is given. Closes #3568,

review by odersky.

git-svn-id: http://lampsvn.epfl.ch/svn-repos/scala/scala/trunk@22303 5e8d7ff9-d8ef-0310-90f0-a4852d11357a

src/compiler/scala/tools/nsc/settings/ScalaSettings.scala

@@ -138,6 +138,7 @@ trait ScalaSettings extends AbsScalaSettings with StandardScalaSettings {
   val Ycompletion   = BooleanSetting    ("-Ycompletion-debug", "Trace all tab completion activity.")
   val Ypmatnaive    = BooleanSetting    ("-Ypmat-naive", "Desugar matches as naively as possible..")
   val Yjenkins      = BooleanSetting    ("-Yjenkins-hashCodes", "Use jenkins hash algorithm for case class generated hashCodes.")
+  val Ynotnull      = BooleanSetting    ("-Ynotnull", "Enable the experimental and incomplete scala.NotNull")
 
   // Warnings
   val Ywarndeadcode = BooleanSetting    ("-Ywarn-dead-code", "Emit warnings for dead code")

src/compiler/scala/tools/nsc/symtab/Types.scala

@@ -385,9 +385,12 @@ trait Types extends reflect.generic.Types { self: SymbolTable =>
      *  the empty list for all other types */
     def boundSyms: List[Symbol] = List()
 
-    /** Mixin a NotNull trait unless type already has one */
-    def notNull: Type = 
-      if (isNotNull || phase.erasedTypes) this else NotNullType(this)
+    /** Mixin a NotNull trait unless type already has one
+     *  ...if the option is given, since it is causing typing bugs.
+     */
+    def notNull: Type =
+      if (!settings.Ynotnull.value || isNotNull || phase.erasedTypes) this
+      else NotNullType(this)
     
     /** Replace formal type parameter symbols with actual type arguments. 
      *

test/files/pos/bug3568.scala

@@ -0,0 +1,46 @@
+import scala.annotation._
+import scala.annotation.unchecked._
+import scala.collection._
+
+
+package object buffer {
+  val broken = new ArrayVec2() // commenting out this line causes the file to compile.
+
+  val works = Class.forName("buffer.ArrayVec2").newInstance().asInstanceOf[ArrayVec2]
+}
+
+package buffer {
+  object Main {
+    // ArrayVec2 can be compiled, instantiated and used.
+    def main(args: Array[String]) { println(works) }
+  }
+  
+  trait ElemType { type Element; type Component <: ElemType }
+  trait Float1 extends ElemType { type Element = Float; type Component = Float1}
+  class Vec2 extends ElemType { type Element = Vec2;  type Component = Float1 }
+
+  abstract class BaseSeq[T <: ElemType, E]
+  extends IndexedSeq[E] with IndexedSeqOptimized[E, IndexedSeq[E]] {
+    def length = 1
+    def apply(i: Int) :E
+  }
+
+  abstract class GenericSeq[T <: ElemType] extends BaseSeq[T, T#Element]
+  trait DataArray[T <: ElemType] extends BaseSeq[T, T#Element]
+  trait DataView[T <: ElemType] extends BaseSeq[T, T#Element]
+  abstract class BaseFloat1 extends BaseSeq[Float1, Float]
+
+  class ArrayFloat1 extends BaseFloat1 with DataArray[Float1] {
+    def apply(i: Int) :Float = 0f
+  }
+
+  class ViewFloat1 extends BaseFloat1 with DataView[Float1] {
+    def apply(i: Int) :Float = 0f
+  }
+
+  class ArrayVec2(val backingSeq: ArrayFloat1)
+  extends GenericSeq[Vec2] with DataArray[Vec2] {
+    def this() = this(new ArrayFloat1)
+    def apply(i: Int) :Vec2 = null
+  }
+}