SI-6287 fixes synthetic symbol clashes in toolbox

Apparently synthetic classes like $anonfun$1 have two properties:
1) Their names are generated using a counter unique to a compilation unit
2) After flatten they levitate to the nearest enclosing package

As a result if we use an empty package to wrap toolbox codegen,
then this package will soon be overflown by $anonfun$1 symbols, because:
1) New codegen session = new compilation unit = new counter which starts at 0
2) New codegen session = new anon funs that end up as children of empty package

Creating a freshly named package for each codegen session fixed the problem.
Now anonfuns from different sessions end up with different parents.

3 files changed, 17 insertions, 3 deletions

diff --git a/src/compiler/scala/tools/reflect/ToolBoxFactory.scala b/src/compiler/scala/tools/reflect/ToolBoxFactory.scala
index d941519958..091224c88a 100644
--- a/src/compiler/scala/tools/reflect/ToolBoxFactory.scala
+++ b/src/compiler/scala/tools/reflect/ToolBoxFactory.scala
@@ -175,7 +175,7 @@ abstract class ToolBoxFactory[U <: JavaUniverse](val u: U) { factorySelf =>
         val thunks = freeTerms map (fte => () => fte.value) // need to be lazy in order not to distort evaluation order
         verify(expr)
 
-        def wrap(expr0: Tree): Tree = {
+        def wrap(expr0: Tree): ModuleDef = {
           val (expr, freeTerms) = extractFreeTerms(expr0, wrapFreeTermRefs = true)
 
           val (obj, mclazz) = rootMirror.EmptyPackageClass.newModuleAndClassSymbol(
@@ -213,11 +213,11 @@ abstract class ToolBoxFactory[U <: JavaUniverse](val u: U) { factorySelf =>
 
           var cleanedUp = resetLocalAttrs(moduledef)
           trace("cleaned up: ")(showAttributed(cleanedUp, true, true, settings.Yshowsymkinds.value))
-          cleanedUp
+          cleanedUp.asInstanceOf[ModuleDef]
         }
 
         val mdef = wrap(expr)
-        val pdef = PackageDef(Ident(nme.EMPTY_PACKAGE_NAME), List(mdef))
+        val pdef = PackageDef(Ident(mdef.name), List(mdef))
         val unit = new CompilationUnit(NoSourceFile)
         unit.body = pdef
 
diff --git a/test/files/run/t6287.check b/test/files/run/t6287.check
new file mode 100644
index 0000000000..2a783704a2
--- /dev/null
+++ b/test/files/run/t6287.check
@@ -0,0 +1,3 @@
+Vector(2, 3, 4)

+Vector(2, 3, 4)

+Vector(2, 3, 4)

diff --git a/test/files/run/t6287.scala b/test/files/run/t6287.scala
new file mode 100644
index 0000000000..0c75d1081b
--- /dev/null
+++ b/test/files/run/t6287.scala
@@ -0,0 +1,11 @@
+import scala.reflect.runtime.universe._
+import scala.reflect.runtime.{currentMirror => cm}
+import scala.tools.reflect._
+
+object Test extends App {
+  val tb = cm.mkToolBox()
+  val t1 = tb.parse("1 to 3 map (_+1)")
+  println(tb.eval(t1))
+  println(tb.eval(t1))
+  println(tb.eval(t1))
+}
\ No newline at end of file