Don't want to chase NPEs around for the rest of...

Don't want to chase NPEs around for the rest of my life. Created
"NoCompilationUnit" and "NoSourceFile" objects to represent not-present
versions of these items. Seems a lot better than null. References
SI-4859, got past NPE only to uncover the actual problem. No review.

1 files changed, 11 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/CompilationUnits.scala b/src/compiler/scala/tools/nsc/CompilationUnits.scala
index aba17ca290..f5e32fbb09 100644
--- a/src/compiler/scala/tools/nsc/CompilationUnits.scala
+++ b/src/compiler/scala/tools/nsc/CompilationUnits.scala
@@ -5,12 +5,20 @@
 
 package scala.tools.nsc
 
-import util.{ FreshNameCreator,Position,NoPosition,SourceFile }
+import util.{ FreshNameCreator, Position, NoPosition, SourceFile, NoSourceFile }
 import scala.collection.mutable
 import scala.collection.mutable.{ LinkedHashSet, ListBuffer }
 
 trait CompilationUnits { self: Global =>
 
+  /** An object representing a missing compilation unit.
+   */
+  object NoCompilationUnit extends CompilationUnit(NoSourceFile) {
+    override lazy val isJava = false
+    override def exists = false
+    override def toString() = "NoCompilationUnit"
+  }
+
   /** One unit of compilation that has been submitted to the compiler.
     * It typically corresponds to a single file of source code.  It includes
     * error-reporting hooks.  */
@@ -25,6 +33,8 @@ trait CompilationUnits { self: Global =>
     /** the content of the compilation unit in tree form */
     var body: Tree = EmptyTree
 
+    def exists = source != NoSourceFile && source != null
+
 //    def parseSettings() = {
 //      val argsmarker = "SCALAC_ARGS"
 //      if(comments nonEmpty) {