Bug 14644 - clang confuses scope operator for global namespace giving extra qualification on member
This is a fix for this bug: https://llvm.org/bugs/show_bug.cgi?id=14644
Essentially the diagnostic needs to distinguish between a "global-specifier with no nested-name-specifier" and nested-name-specifier (everything else) in order to provide a more helpful error message.
Can drop the N-paper reference, and replace "3.4.4, section 3" with [basic.lookup.elab]p3