SI-5604, selections on package objects.

[backport]
mkAttributedSelect, which creates a Select tree based on
a symbol, has been a major source of package object bugs,
because it has not been accurately identifying selections
on package objects.  When selecting foo.bar, if foo turns
out to be a package object, the created Select tree must be

  foo.`package`.bar

However mkAttributedSelect was only examining the owner of
the symbol, which means it would work if the package object
defined bar directly, but not if it inherited it.

src/reflect/scala/reflect/internal/TreeGen.scala

@@ -172,10 +172,29 @@ abstract class TreeGen extends macros.TreeBuilder {
     if (qual.symbol != null && (qual.symbol.isEffectiveRoot || qual.symbol.isEmptyPackage))
       mkAttributedIdent(sym)
     else {
+      // Have to recognize anytime a selection is made on a package
+      // so it can be rewritten to foo.bar.`package`.name rather than
+      // foo.bar.name if name is in the package object.
+      // TODO - factor out the common logic between this and
+      // the Typers method "isInPackageObject", used in typedIdent.
+      val qualsym = (
+        if (qual.tpe ne null) qual.tpe.typeSymbol
+        else if (qual.symbol ne null) qual.symbol
+        else NoSymbol
+      )
+      val needsPackageQualifier = (
+           (sym ne null)
+        && qualsym.isPackage
+        && !sym.isDefinedInPackage
+      )
       val pkgQualifier =
-        if (sym != null && sym.owner.isPackageObjectClass && sym.effectiveOwner == qual.tpe.typeSymbol) {
-          val obj = sym.owner.sourceModule
-          Select(qual, nme.PACKAGE) setSymbol obj setType singleType(qual.tpe, obj)
+        if (needsPackageQualifier) {
+          // The owner of a symbol which requires package qualification may be the
+          // package object iself, but it also could be any superclass of the package
+          // object.  In the latter case, we must go through the qualifier's info
+          // to obtain the right symbol.
+          val packageObject = if (sym.owner.isModuleClass) sym.owner.sourceModule else qual.tpe member nme.PACKAGE
+          Select(qual, nme.PACKAGE) setSymbol packageObject setType singleType(qual.tpe, packageObject)
         }
         else qual
 

test/files/pos/t5604b/T_1.scala

@@ -0,0 +1,6 @@
+// sandbox/t5604/T.scala
+package t6504
+
+trait T {
+  def foo: Boolean = false
+}

test/files/pos/t5604b/T_2.scala

@@ -0,0 +1,6 @@
+// sandbox/t5604/T.scala
+package t6504
+
+trait T {
+  def foo: Boolean = false
+}

test/files/pos/t5604b/Test_1.scala

@@ -0,0 +1,7 @@
+// sandbox/t5604/Test.scala
+package t6504
+
+object Test {
+  def blerg1(a: Any): Any = if (foo) blerg1(0)
+  def blerg2(a: Any): Any = if (t6504.foo) blerg2(0)
+}

test/files/pos/t5604b/Test_2.scala

@@ -0,0 +1,7 @@
+// sandbox/t5604/Test.scala
+package t6504
+
+object Test {
+  def blerg1(a: Any): Any = if (foo) blerg1(0)
+  def blerg2(a: Any): Any = if (t6504.foo) blerg2(0)
+}

test/files/pos/t5604b/pack_1.scala

@@ -0,0 +1,5 @@
+// sandbox/t5604/pack.scala
+package t6504
+
+object `package` extends T {
+}

test/files/run/t5604.check

@@ -0,0 +1,8 @@
+long
+double
+long
+double
+long
+double
+long
+double

test/files/run/t5604.scala

@@ -0,0 +1,50 @@
+// a.scala
+// Fri Jan 13 11:31:47 PST 2012
+
+package foo {
+  object regular extends Duh {
+    def buh(n: Long)   = println("long")
+    def buh(n: Double) = println("double")
+  }
+  class regular {
+    import regular._
+
+    duh(33L)
+    duh(3.0d)
+    foo.regular.duh(33L)
+    foo.regular.duh(3.0d)
+    buh(66L)
+    buh(6.0d)
+    foo.regular.buh(66L)
+    foo.regular.buh(6.0d)
+  }
+
+  trait Duh {
+    def duh(n: Long)   = println("long")
+    def duh(n: Double) = println("double")
+  }
+  package object bar extends Duh {
+    def buh(n: Long)   = println("long")
+    def buh(n: Double) = println("double")
+  }
+  package bar {
+    object Main {
+      def main(args:Array[String]) {
+        duh(33L)
+        duh(3.0d)
+        foo.bar.duh(33L)
+        foo.bar.duh(3.0d)
+        buh(66L)
+        buh(6.0d)
+        foo.bar.buh(66L)
+        foo.bar.buh(6.0d)
+      }
+    }
+  }
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    foo.bar.Main.main(null)
+  }
+}