Broader checks for poisonous this references.

Replaces more VerifyErrors with implementation restrictions.

12 files changed, 146 insertions, 82 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/ExplicitOuter.scala b/src/compiler/scala/tools/nsc/transform/ExplicitOuter.scala
index 1003d417f6..a86d8aa2d6 100644
--- a/src/compiler/scala/tools/nsc/transform/ExplicitOuter.scala
+++ b/src/compiler/scala/tools/nsc/transform/ExplicitOuter.scala
@@ -8,6 +8,7 @@ package transform
 
 import symtab._
 import Flags.{ CASE => _, _ }
+import scala.collection.mutable
 import scala.collection.mutable.ListBuffer
 import matching.{ Patterns, ParallelMatching }
 
@@ -209,6 +210,8 @@ abstract class ExplicitOuter extends InfoTransform
 
     /** The first outer selection from currently transformed tree.
      *  The result is typed but not positioned.
+     *
+     * Will return `EmptyTree` if there is no outer accessor because of a premature self reference.
      */
     protected def outerValue: Tree =
       if (outerParam != NoSymbol) ID(outerParam)
@@ -218,25 +221,34 @@ abstract class ExplicitOuter extends InfoTransform
      *  The result is typed but not positioned.
      *  If the outer access is from current class and current class is final
      *  take outer field instead of accessor
+     *
+     *  Will return `EmptyTree` if there is no outer accessor because of a premature self reference.
      */
     private def outerSelect(base: Tree): Tree = {
-      val outerAcc = outerAccessor(base.tpe.typeSymbol.toInterface)
-      val currentClass = this.currentClass //todo: !!! if this line is removed, we get a build failure that protected$currentClass need an override modifier
-      // outerFld is the $outer field of the current class, if the reference can
-      // use it (i.e. reference is allowed to be of the form this.$outer),
-      // otherwise it is NoSymbol
-      val outerFld =
-        if (outerAcc.owner == currentClass &&
+      val baseSym = base.tpe.typeSymbol.toInterface
+      val outerAcc = outerAccessor(baseSym)
+      if (outerAcc == NoSymbol && baseSym.ownersIterator.exists(isUnderConstruction)) {
+         // e.g neg/t6666.scala
+         // The caller will report the error with more information.
+         EmptyTree
+      } else {
+        val currentClass = this.currentClass //todo: !!! if this line is removed, we get a build failure that protected$currentClass need an override modifier
+        // outerFld is the $outer field of the current class, if the reference can
+        // use it (i.e. reference is allowed to be of the form this.$outer),
+        // otherwise it is NoSymbol
+        val outerFld =
+          if (outerAcc.owner == currentClass &&
             base.tpe =:= currentClass.thisType &&
             outerAcc.owner.isEffectivelyFinal)
-          outerField(currentClass) suchThat (_.owner == currentClass)
-        else
-          NoSymbol
-      val path =
-        if (outerFld != NoSymbol) Select(base, outerFld)
-        else Apply(Select(base, outerAcc), Nil)
-
-      localTyper typed path
+            outerField(currentClass) suchThat (_.owner == currentClass)
+          else
+            NoSymbol
+        val path =
+          if (outerFld != NoSymbol) Select(base, outerFld)
+          else Apply(Select(base, outerAcc), Nil)
+
+        localTyper typed path
+      }
     }
 
     /** The path
@@ -256,6 +268,17 @@ abstract class ExplicitOuter extends InfoTransform
       else outerPath(outerSelect(base), from.outerClass, to)
     }
 
+
+    /** The stack of constructor symbols in which a call to this() or to the super
+      * constructor is active.
+      */
+    protected def isUnderConstruction(clazz: Symbol) = selfOrSuperCalls exists (_.owner == clazz)
+    protected val selfOrSuperCalls = mutable.Stack[Symbol]()
+    @inline protected def inSelfOrSuperCall[A](sym: Symbol)(a: => A) = {
+      selfOrSuperCalls push sym
+      try a finally selfOrSuperCalls.pop()
+    }
+
     override def transform(tree: Tree): Tree = {
       val savedOuterParam = outerParam
       try {
@@ -269,7 +292,10 @@ abstract class ExplicitOuter extends InfoTransform
             }
           case _ =>
         }
-        super.transform(tree)
+        if (treeInfo isSelfOrSuperConstrCall tree) // TODO also handle (and test) (treeInfo isEarlyDef tree)
+          inSelfOrSuperCall(currentOwner)(super.transform(tree))
+        else
+          super.transform(tree)
       }
       finally outerParam = savedOuterParam
     }
@@ -335,7 +361,8 @@ abstract class ExplicitOuter extends InfoTransform
 
     /** The definition tree of the outer accessor of current class
      */
-    def outerFieldDef: Tree = VAL(outerField(currentClass)) === EmptyTree
+    def outerFieldDef: Tree =
+      VAL(outerField(currentClass)) === EmptyTree
 
     /** The definition tree of the outer accessor of current class
      */
@@ -483,6 +510,9 @@ abstract class ExplicitOuter extends InfoTransform
                 val clazz = sym.owner
                 val vparamss1 =
                   if (isInner(clazz)) { // (4)
+                    if (isUnderConstruction(clazz.outerClass)) {
+                      reporter.error(tree.pos, s"Implementation restriction: ${clazz.fullLocationString} requires premature access to ${clazz.outerClass}.")
+                    }
                     val outerParam =
                       sym.newValueParameter(nme.OUTER, sym.pos) setInfo clazz.outerClass.thisType
                     ((ValDef(outerParam) setType NoType) :: vparamss.head) :: vparamss.tail
diff --git a/src/compiler/scala/tools/nsc/transform/LambdaLift.scala b/src/compiler/scala/tools/nsc/transform/LambdaLift.scala
index a4f75f424f..d912b76f68 100644
--- a/src/compiler/scala/tools/nsc/transform/LambdaLift.scala
+++ b/src/compiler/scala/tools/nsc/transform/LambdaLift.scala
@@ -317,7 +317,7 @@ abstract class LambdaLift extends InfoTransform {
       else searchIn(currentOwner)
     }
 
-    private def memberRef(sym: Symbol) = {
+    private def memberRef(sym: Symbol): Tree = {
       val clazz = sym.owner.enclClass
       //Console.println("memberRef from "+currentClass+" to "+sym+" in "+clazz)
       def prematureSelfReference() {
@@ -331,12 +331,17 @@ abstract class LambdaLift extends InfoTransform {
         if (clazz == currentClass) gen.mkAttributedThis(clazz)
         else {
           sym resetFlag (LOCAL | PRIVATE)
-          if (selfOrSuperCalls exists (_.owner == clazz)) {
+          if (isUnderConstruction(clazz)) {
             prematureSelfReference()
             EmptyTree
           }
           else if (clazz.isStaticOwner) gen.mkAttributedQualifier(clazz.thisType)
-          else outerPath(outerValue, currentClass.outerClass, clazz)
+          else {
+            outerValue match {
+              case EmptyTree => prematureSelfReference(); return EmptyTree
+              case o         => outerPath(o, currentClass.outerClass, clazz)
+            }
+          }
         }
       Select(qual, sym) setType sym.tpe
     }
@@ -507,25 +512,13 @@ abstract class LambdaLift extends InfoTransform {
 
     private def preTransform(tree: Tree) = super.transform(tree) setType lifted(tree.tpe)
 
-    /** The stack of constructor symbols in which a call to this() or to the super
-      * constructor is active.
-      */
-    private val selfOrSuperCalls = mutable.Stack[Symbol]()
-    @inline private def inSelfOrSuperCall[A](sym: Symbol)(a: => A) = try {
-      selfOrSuperCalls push sym
-      a
-    } finally selfOrSuperCalls.pop()
-
     override def transform(tree: Tree): Tree = tree match {
       case Select(ReferenceToBoxed(idt), elem) if elem == nme.elem =>
         postTransform(preTransform(idt), isBoxedRef = false)
       case ReferenceToBoxed(idt) =>
         postTransform(preTransform(idt), isBoxedRef = true)
       case _ =>
-        def transformTree = postTransform(preTransform(tree))
-        if (treeInfo isSelfOrSuperConstrCall tree)
-          inSelfOrSuperCall(currentOwner)(transformTree)
-        else transformTree
+        postTransform(preTransform(tree))
     }
 
     /** Transform statements and add lifted definitions to them. */
diff --git a/test/files/neg/t6666.check b/test/files/neg/t6666.check
index d0378173ea..63145f6ed7 100644
--- a/test/files/neg/t6666.check
+++ b/test/files/neg/t6666.check
@@ -16,25 +16,19 @@ t6666.scala:54: error: Implementation restriction: access of value x$7 in class
 t6666.scala:58: error: Implementation restriction: access of method x$8 in class C3 from anonymous class 9, would require illegal premature access to the unconstructed `this` of class C3
   F.hof(() => x)
               ^
-t6666.scala:62: error: Implementation restriction: access of method x$9 in class C4 from object Nested$5, would require illegal premature access to the unconstructed `this` of class C4
+t6666.scala:62: error: Implementation restriction: access of method x$9 in class C4 from object Nested$3, would require illegal premature access to the unconstructed `this` of class C4
   object Nested { def xx = x}
                            ^
-t6666.scala:68: error: Implementation restriction: access of method x$10 in class C5 from object Nested$6, would require illegal premature access to the unconstructed `this` of class C5
-    object Nested { def xx = x}
-                             ^
-t6666.scala:83: error: Implementation restriction: access of method x$12 in class C11 from anonymous class 12, would require illegal premature access to the unconstructed `this` of class C11
+t6666.scala:76: error: Implementation restriction: access of method x$11 in class C11 from anonymous class 12, would require illegal premature access to the unconstructed `this` of class C11
       F.byname(x)
                ^
-t6666.scala:102: error: Implementation restriction: access of method x$13 in class C13 from anonymous class 13, would require illegal premature access to the unconstructed `this` of class C13
+t6666.scala:95: error: Implementation restriction: access of method x$12 in class C13 from anonymous class 13, would require illegal premature access to the unconstructed `this` of class C13
       F.hof(() => x)
                   ^
-t6666.scala:111: error: Implementation restriction: access of method x$14 in class C14 from object Nested$7, would require illegal premature access to the unconstructed `this` of class C14
+t6666.scala:104: error: Implementation restriction: access of method x$13 in class C14 from object Nested$4, would require illegal premature access to the unconstructed `this` of class C14
       object Nested { def xx = x}
                                ^
-t6666.scala:122: error: Implementation restriction: access of method x$15 in class C15 from object Nested$8, would require illegal premature access to the unconstructed `this` of class C15
-        object Nested { def xx = x}
-                                 ^
-t6666.scala:131: error: Implementation restriction: access of method foo$1 in class COuter from class CInner$1, would require illegal premature access to the unconstructed `this` of class COuter
+t6666.scala:112: error: Implementation restriction: access of method foo$1 in class COuter from class CInner$1, would require illegal premature access to the unconstructed `this` of class COuter
   class CInner extends C({foo})
                           ^
-13 errors found
+11 errors found
diff --git a/test/files/neg/t6666.scala b/test/files/neg/t6666.scala
index d37ffaf141..19073884bd 100644
--- a/test/files/neg/t6666.scala
+++ b/test/files/neg/t6666.scala
@@ -62,13 +62,6 @@ class C4 extends C({
   object Nested { def xx = x}
   Nested.xx
 })
-class C5 extends C({
-  def x = "".toString
-  val y = {
-    object Nested { def xx = x}
-    Nested.xx
-  }
-})
 
 // okay, for same reason as O6
 class C6 extends C({
@@ -114,18 +107,6 @@ class C14(a: Any) {
   }
 }
 
-class C15(a: Any) {
-  def this() = {
-    this({
-      def x = "".toString
-      val y = {
-        object Nested { def xx = x}
-        Nested.xx
-      }
-    })
-  }
-}
-
 class COuter extends C({
   def foo = 0
   class CInner extends C({foo})
diff --git a/test/files/neg/t6666b.check b/test/files/neg/t6666b.check
index 090bee800d..c3ffc7cfa9 100644
--- a/test/files/neg/t6666b.check
+++ b/test/files/neg/t6666b.check
@@ -1,4 +1,7 @@
-t6666b.scala:6: error: Implementation restriction: access of object TreeOrd$1 from object TreeOrd$2, would require illegal premature access to the unconstructed `this` of class Test
-    implicit object TreeOrd extends Ordering[K](){
-                    ^
-one error found
+t6666b.scala:11: error: Implementation restriction: access of method x$1 in class C5 from object Nested$3, would require illegal premature access to the unconstructed `this` of class C5
+    object Nested { def xx = x}
+                             ^
+t6666b.scala:22: error: Implementation restriction: access of method x$2 in class C15 from object Nested$4, would require illegal premature access to the unconstructed `this` of class C15
+        object Nested { def xx = x}
+                                 ^
+two errors found
diff --git a/test/files/neg/t6666b.scala b/test/files/neg/t6666b.scala
index 0b8f1aa1a3..205ded76e5 100644
--- a/test/files/neg/t6666b.scala
+++ b/test/files/neg/t6666b.scala
@@ -1,17 +1,27 @@
-import scala.collection.immutable.TreeMap
-import scala.math.Ordering
-
-class Test[K](param:TreeMap[K,Int]){
-  def this() = this({
-    implicit object TreeOrd extends Ordering[K](){
-      def compare(a: K, b: K) = {
-        -1
-      }
-    }
-    new TreeMap[K, Int]()
-  })
+class C(a: Any)
+object F {
+  def byname(a: => Any) = println(a)
+  def hof(a: () => Any) = println(a())
 }
 
-object Test extends App {
-  new Test()
+
+class C5 extends C({
+  def x = "".toString
+  val y = {
+    object Nested { def xx = x}
+    Nested.xx
+  }
+})
+
+
+class C15(a: Any) {
+  def this() = {
+    this({
+      def x = "".toString
+      val y = {
+        object Nested { def xx = x}
+        Nested.xx
+      }
+    })
+  }
 }
diff --git a/test/files/neg/t6666c.check b/test/files/neg/t6666c.check
new file mode 100644
index 0000000000..8fb9f4ba14
--- /dev/null
+++ b/test/files/neg/t6666c.check
@@ -0,0 +1,10 @@
+t6666c.scala:2: error: Implementation restriction: access of method x$1 in class D from object X$4, would require illegal premature access to the unconstructed `this` of class D
+class D extends C({def x = 0; object X { x }})
+                                         ^
+t6666c.scala:5: error: Implementation restriction: access of method x$2 in class D1 from object X$5, would require illegal premature access to the unconstructed `this` of class D1
+class D1 extends C1({def x = 0; () => {object X { x }}})
+                                                  ^
+t6666c.scala:8: error: Implementation restriction: access of method x$3 from object X$6, would require illegal premature access to the unconstructed `this` of anonymous class 2
+class D2 extends C2({def x = 0; object X { x }})
+                                           ^
+three errors found
diff --git a/test/files/neg/t6666c.scala b/test/files/neg/t6666c.scala
new file mode 100644
index 0000000000..76cc358307
--- /dev/null
+++ b/test/files/neg/t6666c.scala
@@ -0,0 +1,8 @@
+class C(a: Any)
+class D extends C({def x = 0; object X { x }})
+
+class C1(a: () => Any)
+class D1 extends C1({def x = 0; () => {object X { x }}})
+
+class C2(a: => Any)
+class D2 extends C2({def x = 0; object X { x }})
diff --git a/test/files/neg/t6666d.check b/test/files/neg/t6666d.check
new file mode 100644
index 0000000000..b4785f0129
--- /dev/null
+++ b/test/files/neg/t6666d.check
@@ -0,0 +1,4 @@
+t6666d.scala:7: error: Implementation restriction: access of object TreeOrd$1 from object TreeOrd$2, would require illegal premature access to the unconstructed `this` of class Test
+    implicit object TreeOrd extends Ordering[K](){
+                    ^
+one error found
diff --git a/test/files/neg/t6666d.scala b/test/files/neg/t6666d.scala
new file mode 100644
index 0000000000..49a688f91b
--- /dev/null
+++ b/test/files/neg/t6666d.scala
@@ -0,0 +1,18 @@
+
+import scala.collection.immutable.TreeMap
+import scala.math.Ordering
+
+class Test[K](param:TreeMap[K,Int]){
+  def this() = this({
+    implicit object TreeOrd extends Ordering[K](){
+      def compare(a: K, b: K) = {
+        -1
+      }
+    }
+    new TreeMap[K, Int]()
+  })
+}
+
+object Test extends App {
+  new Test()
+}
diff --git a/test/files/neg/t6666e.check b/test/files/neg/t6666e.check
new file mode 100644
index 0000000000..9fcc3ab718
--- /dev/null
+++ b/test/files/neg/t6666e.check
@@ -0,0 +1,4 @@
+t6666e.scala:8: error: Implementation restriction: anonymous class $anonfun requires premature access to class Crash.
+    this(Nil.collect{case x =>})
+                    ^
+one error found
diff --git a/test/files/neg/t6666e.scala b/test/files/neg/t6666e.scala
new file mode 100644
index 0000000000..120a5878b2
--- /dev/null
+++ b/test/files/neg/t6666e.scala
@@ -0,0 +1,9 @@
+
+import scala.collection.immutable.TreeMap
+import scala.math.Ordering
+
+
+class Crash(a: Any) {
+  def this() =
+    this(Nil.collect{case x =>})
+}