1 files changed, 36 insertions, 0 deletions
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/analysis/TypeFlowInterpreter.scala b/src/compiler/scala/tools/nsc/backend/jvm/analysis/TypeFlowInterpreter.scala
new file mode 100644
index 0000000000..bcf9978c16
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/backend/jvm/analysis/TypeFlowInterpreter.scala
@@ -0,0 +1,36 @@
+package scala.tools.nsc
+package backend.jvm
+package analysis
+
+import scala.tools.asm.Type
+import scala.tools.asm.tree.analysis.{BasicValue, BasicInterpreter}
+
+abstract class TypeFlowInterpreter extends BasicInterpreter {
+  override def newValue(tp: Type) = {
+    if (tp == null) super.newValue(tp)
+    else if (isRef(tp)) new BasicValue(tp)
+    else super.newValue(tp)
+  }
+
+  def isRef(tp: Type) = tp != null && (tp.getSort match {
+    case Type.OBJECT | Type.ARRAY => true
+    case _ => false
+  })
+
+  def refLub(a: BasicValue, b: BasicValue): BasicValue
+
+  override def merge(a: BasicValue, b: BasicValue): BasicValue = {
+    if (a == b) a
+    else if (isRef(a.getType) && isRef(b.getType)) refLub(a, b)
+    else BasicValue.UNINITIALIZED_VALUE
+  }
+}
+
+/**
+ * A [[TypeFlowInterpreter]] which collapses LUBs of non-equal reference types to Object.
+ * This could be made more precise by looking up ClassBTypes for the two reference types and using
+ * the `jvmWiseLUB` method.
+ */
+class NonLubbingTypeFlowInterpreter extends TypeFlowInterpreter {
+  def refLub(a: BasicValue, b: BasicValue): BasicValue = BasicValue.REFERENCE_VALUE // java/lang/Object
+}