In principle this is very similar to the normal scope search. If the
provided name belongs to a type that can contain members (contrary to a
variable in scope search), perform the namespace search. With namespace
search show all possible members that are at the given scope.
Since we perform the scope search at file level, don't perform the
namespace search for tags that can span multiple files otherwise we get
incomplete results which could be confusing to users. This involves
namespaces and packages.
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