Loss "template <class T> " in Decl::dump().

Hello all!

I use RecursiveASTVisitor to pass over the top level declarations.
I determined the VisitDecl method in class derived from RecursiveASTVisitor
bool MyASTVisitor::VisitDecl (Decl * D){
  D -> dump();

I use the test example:
--- 1.cpp ---
template <class T> void templ_a(T x){
  int b = 123;

int main(){
  int a = 123;
  return 0;

The question is: why do you need it? dump() is as far as I understand
considered a debugging aid, not a (for some definition correct)