SI-8085 Fix BrowserTraverser for package objects

A source file like:

    import foo.bar
    package object baz

Is parsed into:

    package <empty> {
       import foo.bar
       package baz {
          object `package`
       }
    }

A special case in Namers compensates by adjusting the owner of
`baz` to be `<root>`, rather than `<empty>`.

This wasn't being accounted for in `BrowserTraverser`, which
underpins `-sourcepath`, and allows the presentation compiler to
load top level symbols from sources outside those passes as
the list of sources to compile.

This bug did not appear in sources like:

    package p1
    package object p2 { ... }

... because the parser does not wrap this in the `package <empty> {}`

This goes some way to explaining why it has gone unnoticed for
so long.

1 files changed, 4 insertions, 2 deletions

diff --git a/src/compiler/scala/tools/nsc/symtab/BrowsingLoaders.scala b/src/compiler/scala/tools/nsc/symtab/BrowsingLoaders.scala
index f2aab36b51..c7bd678385 100644
--- a/src/compiler/scala/tools/nsc/symtab/BrowsingLoaders.scala
+++ b/src/compiler/scala/tools/nsc/symtab/BrowsingLoaders.scala
@@ -64,8 +64,10 @@ abstract class BrowsingLoaders extends SymbolLoaders {
           addPackagePrefix(pre)
           packagePrefix += ("." + name)
         case Ident(name) =>
-          if (packagePrefix.length != 0) packagePrefix += "."
-          packagePrefix += name
+          if (name != nme.EMPTY_PACKAGE_NAME) { // mirrors logic in Namers, see createPackageSymbol
+            if (packagePrefix.length != 0) packagePrefix += "."
+            packagePrefix += name
+          }
         case _ =>
           throw new MalformedInput(pkg.pos.point, "illegal tree node in package prefix: "+pkg)
       }