convert ast::expr into a struct
convert ast::ty into a struct
convert ast::{ty_field_,ty_method} into a struct
convert the remaining ast record types into structs

These are: region,arg,fn_decl,method,_mod,foreign_mod,
variant_arg,enum_def_,variant_,trait_ref.
convert librustc record types to structs

specifically:

freevars::freevar_entry
ty::{field_ty,AutoAdjustment,AutoRef}
mod::{method_param,method_map_entry}
Convert many libsyntax records into structs

Specifically:

ast_map::ctx
ast_util::id_range
diagnostic::{handler_t,codemap_t}
auto_encode::field
ext::base::{macro_def,syntax_expander_tt,syntax_expander_tt_item}
ext::pipes::proto::next_state