traversing the ast using libtooling

Hi,

When I want to walk over the complete ast and visit each node (by using
a RecursiveASTVisitor<...>), do I need to implement all of TraverseDecl,
TraverseStmt and TraverseType? Because with all of those it looks like
some code is processed twice.

Second question: there are other Traverse...-methods as well:
TraverseAttr for example. Shouldn't I implement that one as well to get
all data?

Folkert van Heusden