Change ast::path into a struct.
Convert ast::def_id into a struct.
change ast::ty_param into a struct.
convert ast::foreign_item to a struct
convert ast::struct_dtor_ into a struct
convert ast::item into a struct
convert ast::struct_def to a struct
convert ast::struct_field_ into a struct
convert ast::attribute_ and ast::view_item to a struct
convert ast::pat_list_ident_ to a struct