Set scene for Predef.$scope's demise.

When there's no Predef.$scope but xml is being used,
the compiler aliases scala.xml.TopScope to $scope.

There must be a scala.xml package when xml literals were parsed.

For compatibility with the old library, which relied on $scope being in scope,
synthesize a `import scala.xml.{TopScope => $scope}` when xml is needed,
but there's no Predef.$scope and the old library is detected (scala.xml.TopScope exists).

4 files changed, 11 insertions, 2 deletions

diff --git a/src/reflect/scala/reflect/internal/Definitions.scala b/src/reflect/scala/reflect/internal/Definitions.scala
index 4f2b7e2642..3470b05495 100644
--- a/src/reflect/scala/reflect/internal/Definitions.scala
+++ b/src/reflect/scala/reflect/internal/Definitions.scala
@@ -16,7 +16,7 @@ import scala.reflect.api.{Universe => ApiUniverse}
 trait Definitions extends api.StandardDefinitions {
   self: SymbolTable =>
 
-  import rootMirror.{getModule, getPackage, getClassByName, getRequiredClass, getRequiredModule, getClassIfDefined, getModuleIfDefined, getPackageObject, getPackageObjectIfDefined, requiredClass, requiredModule}
+  import rootMirror.{getModule, getPackage, getClassByName, getRequiredClass, getRequiredModule, getClassIfDefined, getModuleIfDefined, getPackageObject, getPackageIfDefined, getPackageObjectIfDefined, requiredClass, requiredModule}
 
   object definitions extends DefinitionsClass
 
@@ -471,6 +471,10 @@ trait Definitions extends api.StandardDefinitions {
       def methodCache_find          = getMemberMethod(MethodCacheClass, nme.find_)
       def methodCache_add           = getMemberMethod(MethodCacheClass, nme.add_)
 
+    // XML
+    lazy val ScalaXmlTopScope = getModuleIfDefined("scala.xml.TopScope")
+    lazy val ScalaXmlPackage  = getPackageIfDefined("scala.xml")
+
     // scala.reflect
     lazy val ReflectPackage              = requiredModule[scala.reflect.`package`.type]
     lazy val ReflectApiPackage           = getPackageObjectIfDefined("scala.reflect.api") // defined in scala-reflect.jar, so we need to be careful
diff --git a/src/reflect/scala/reflect/internal/Mirrors.scala b/src/reflect/scala/reflect/internal/Mirrors.scala
index bf38c3bf1e..6ed9de8e20 100644
--- a/src/reflect/scala/reflect/internal/Mirrors.scala
+++ b/src/reflect/scala/reflect/internal/Mirrors.scala
@@ -176,6 +176,9 @@ trait Mirrors extends api.Mirrors {
     def getPackage(fullname: TermName): ModuleSymbol =
       ensurePackageSymbol(fullname.toString, getModuleOrClass(fullname), allowModules = true)
 
+    def getPackageIfDefined(fullname: TermName): Symbol =
+      wrapMissing(getPackage(fullname))
+
     @deprecated("Use getPackage", "2.11.0") def getRequiredPackage(fullname: String): ModuleSymbol =
       getPackage(newTermNameCached(fullname))
 
diff --git a/src/reflect/scala/reflect/internal/StdNames.scala b/src/reflect/scala/reflect/internal/StdNames.scala
index 81fffc833c..30aaaa1f3a 100644
--- a/src/reflect/scala/reflect/internal/StdNames.scala
+++ b/src/reflect/scala/reflect/internal/StdNames.scala
@@ -599,6 +599,7 @@ trait StdNames {
     val currentMirror: NameType        = "currentMirror"
     val delayedInit: NameType          = "delayedInit"
     val delayedInitArg: NameType       = "delayedInit$body"
+    val dollarScope: NameType          = "$scope"
     val drop: NameType                 = "drop"
     val elem: NameType                 = "elem"
     val emptyValDef: NameType          = "emptyValDef"
@@ -684,6 +685,7 @@ trait StdNames {
     val thisPrefix : NameType          = "thisPrefix"
     val toArray: NameType              = "toArray"
     val toObjectArray : NameType       = "toObjectArray"
+    val TopScope: NameType             = "TopScope"
     val toString_ : NameType           = "toString"
     val toTypeConstructor: NameType    = "toTypeConstructor"
     val tpe : NameType                 = "tpe"
diff --git a/src/reflect/scala/reflect/internal/Trees.scala b/src/reflect/scala/reflect/internal/Trees.scala
index 8781423a6d..ceb3b383d7 100644
--- a/src/reflect/scala/reflect/internal/Trees.scala
+++ b/src/reflect/scala/reflect/internal/Trees.scala
@@ -327,7 +327,7 @@ trait Trees extends api.Trees { self: SymbolTable =>
   case class ImportSelector(name: Name, namePos: Int, rename: Name, renamePos: Int) extends ImportSelectorApi
   object ImportSelector extends ImportSelectorExtractor {
     val wild     = ImportSelector(nme.WILDCARD, -1, null, -1)
-    val wildList = List(wild)
+    val wildList = List(wild) // OPT This list is shared for performance.
   }
 
   case class Import(expr: Tree, selectors: List[ImportSelector])