fix usingnamespace

It used to be that usingnamespace was only allowed at top level. This
made it OK to put the state inside the AST node data structure. However,
now usingnamespace can occur inside any aggregate data structure, and
therefore the state must be in the TopLevelDeclaration rather than in
the AST node.

There were two other problems with the usingnamespace implementation:

 * It was passing the wrong destination ScopeDecl, so it could cause an
   incorrect error such as "import of file outside package path".
 * When doing `usingnamespace` on a file that already had
   `pub usingnamespace` in it would "steal" the usingnamespace, causing
   incorrect "use of undeclared identifier" errors in the target file.

closes #2632
closes #2580

0 files changed, 0 insertions, 0 deletions