Add documentation

Author: nicolasstucki

compiler/src/dotty/tools/dotc/core/Denotations.scala

@@ -1199,9 +1199,16 @@ object Denotations {
             val alt =
               if (generateStubs) missingHook(owner.symbol.moduleClass, selector)
               else NoSymbol
+
+            def isPackageFromCoreLibMissing: Boolean = {
+              owner.symbol == defn.RootClass &&
+              {
+                selector == nme.scala_ || // if the scala package is missing, the stdlib must be missing
+                selector == nme.scalaShadowing // if the scalaShadowing package is missing, the dotty library must be missing
+              }
+            }
             if (alt.exists) alt.denot
-            else if (owner.symbol == defn.RootClass && (selector == nme.scala_ || selector == nme.scalaShadowing))
-              throw new MissingCoreLibraryException(selector.toString)
+            else if (isPackageFromCoreLibMissing) throw new MissingCoreLibraryException(selector.toString)
             else MissingRef(owner, selector)
           }
         }

compiler/test/dotty/tools/vulpix/TestConfiguration.scala

@@ -25,7 +25,7 @@ object TestConfiguration {
 
   val classPath = mkClassPath(Jars.dottyTestDeps)
 
-  def mkClassPath(deps: List[String]) = {
+  def mkClassPath(deps: List[String]): Array[String] = {
     val paths = deps map { p =>
       val file = new java.io.File(p)
       assert(