Handle these properly in check-below (with test).
Use NoFilter and NoObject to make if typechecking work properly with filters.
Reject mismatched filters/objects (with test).
New version of require/typed that handles opaque and struct requires.
Reorganize docs around this.
svn: r15155
original commit: 7b82069fa0805e3de16c9a49d6c303789fc75419