Removed -Ynotnull setting.

It never worked and it would periodically jump out and bite
someone. Slash and burn so new plants can take root. Eliminated
NotNullType and NotNullClass, internal elements. Removed notNull
method on Type, which no longer has a purpose. Retained 'def
isNotNull' because there are types which are known by construction
not to be null (ThisType, ConstantType as long as the constant
isn't null, etc.) and that's still useful to know.

3 files changed, 16 insertions, 26 deletions

diff --git a/src/compiler/scala/tools/nsc/ast/TreeGen.scala b/src/compiler/scala/tools/nsc/ast/TreeGen.scala
index b9eb511a9a..d195d195af 100644
--- a/src/compiler/scala/tools/nsc/ast/TreeGen.scala
+++ b/src/compiler/scala/tools/nsc/ast/TreeGen.scala
@@ -19,16 +19,17 @@ abstract class TreeGen extends scala.reflect.internal.TreeGen with TreeDSL {
   import global._
   import definitions._
 
-  def mkCheckInit(tree: Tree): Tree = {
-    val tpe =
-      if (tree.tpe != null || !tree.hasSymbolField) tree.tpe
-      else tree.symbol.tpe
-
-    if (!global.phase.erasedTypes && settings.warnSelectNullable.value &&
-        tpe <:< NotNullClass.tpe && !tpe.isNotNull)
-      mkRuntimeCall(nme.checkInitialized, List(tree))
-    else
-      tree
+  def mkCheckInit(tree: Tree): Tree = { tree
+    // Leaving in the next commit...
+    // val tpe =
+    //   if (tree.tpe != null || !tree.hasSymbolField) tree.tpe
+    //   else tree.symbol.tpe
+
+    // if (!global.phase.erasedTypes && settings.warnSelectNullable.value &&
+    //     tpe <:< NotNullClass.tpe && !tpe.isNotNull)
+    //   mkRuntimeCall(nme.checkInitialized, List(tree))
+    // else
+    //   tree
   }
 
   /** Builds a fully attributed wildcard import node.
diff --git a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
index 9469113238..7572b0ef90 100644
--- a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
@@ -166,7 +166,6 @@ trait ScalaSettings extends AbsScalaSettings
   val Yreifycopypaste = BooleanSetting    ("-Yreify-copypaste", "Dump the reified trees in copypasteable representation.")
   val Yreplsync       = BooleanSetting    ("-Yrepl-sync", "Do not use asynchronous code for repl startup")
   val Yreploutdir     = StringSetting     ("-Yrepl-outdir", "path", "Write repl-generated classfiles to given output directory (use \"\" to generate a temporary dir)" , "")
-  val Ynotnull        = BooleanSetting    ("-Ynotnull", "Enable (experimental and incomplete) scala.NotNull.")
   val YmethodInfer    = BooleanSetting    ("-Yinfer-argument-types", "Infer types for arguments of overriden methods.")
   val etaExpandKeepsStar = BooleanSetting ("-Yeta-expand-keeps-star", "Eta-expand varargs methods to T* rather than Seq[T].  This is a temporary option to ease transition.").
                                           withDeprecationMessage("This flag is scheduled for removal in 2.12. If you have a case where you need this flag then please report a bug.")
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index ba34ae4871..bc3440380c 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -4187,11 +4187,11 @@ trait Typers extends Adaptations with Tags {
 
       def typedArrayValue(tree: ArrayValue) = {
         val elemtpt1 = typedType(tree.elemtpt, mode)
-        val elems1 = tree.elems mapConserve (elem => typed(elem, mode, elemtpt1.tpe))
-        treeCopy.ArrayValue(tree, elemtpt1, elems1)
-          .setType(
-            (if (isFullyDefined(pt) && !phase.erasedTypes) pt
-             else arrayType(elemtpt1.tpe)).notNull)
+        val elems1   = tree.elems mapConserve (elem => typed(elem, mode, elemtpt1.tpe))
+        // see run/t6126 for an example where `pt` does not suffice (tagged types)
+        val tpe1     = if (isFullyDefined(pt) && !phase.erasedTypes) pt else arrayType(elemtpt1.tpe)
+
+        treeCopy.ArrayValue(tree, elemtpt1, elems1) setType tpe1
       }
 
       def typedAssign(lhs: Tree, rhs: Tree): Tree = {
@@ -4738,16 +4738,6 @@ trait Typers extends Adaptations with Tags {
               (stabilize(treeAndPre._1, treeAndPre._2, mode, pt), None)
           }
 
-          def isPotentialNullDeference() = {
-            !isPastTyper &&
-            !sym.isConstructor &&
-            !(qual.tpe <:< NotNullClass.tpe) && !qual.tpe.isNotNull &&
-            !(List(Any_isInstanceOf, Any_asInstanceOf) contains result.symbol)  // null.is/as is not a dereference
-          }
-          // unit is null here sometimes; how are we to know when unit might be null? (See bug #2467.)
-          if (settings.warnSelectNullable.value && isPotentialNullDeference && unit != null)
-            unit.warning(tree.pos, "potential null pointer dereference: "+tree)
-
           result match {
             // could checkAccessible (called by makeAccessible) potentially have skipped checking a type application in qual?
             case SelectFromTypeTree(qual@TypeTree(), name) if qual.tpe.typeArgs.nonEmpty => // TODO: somehow the new qual is not checked in refchecks