rust/src/comp/syntax/fold.rs

import syntax::codemap::span;
import ast::*;

import std::ivec;
import std::option;

export ast_fold_precursor;
export ast_fold;
export default_ast_fold;
export make_fold;
export dummy_out;
export noop_fold_crate;
export noop_fold_item;
export noop_fold_expr;
export noop_fold_mod;

type ast_fold = @mutable a_f;

// We may eventually want to be able to fold over type parameters, too

type ast_fold_precursor =
    //unlike the others, item_ is non-trivial
    {fold_crate: fn(&crate_, ast_fold) -> crate_ ,
     fold_crate_directive:
         fn(&crate_directive_, ast_fold) -> crate_directive_ ,
     fold_view_item: fn(&view_item_, ast_fold) -> view_item_ ,
     fold_native_item: fn(&@native_item, ast_fold) -> @native_item ,
     fold_item: fn(&@item, ast_fold) -> @item ,
     fold_item_underscore: fn(&item_, ast_fold) -> item_ ,
     fold_method: fn(&method_, ast_fold) -> method_ ,
     fold_block: fn(&blk_, ast_fold) -> blk_ ,
     fold_stmt: fn(&stmt_, ast_fold) -> stmt_ ,
     fold_arm: fn(&arm, ast_fold) -> arm ,
     fold_pat: fn(&pat_, ast_fold) -> pat_ ,
     fold_decl: fn(&decl_, ast_fold) -> decl_ ,
     fold_expr: fn(&expr_, ast_fold) -> expr_ ,
     fold_ty: fn(&ty_, ast_fold) -> ty_ ,
     fold_constr: fn(&ast::constr_, ast_fold) -> constr_ ,
     fold_fn: fn(&_fn, ast_fold) -> _fn ,
     fold_mod: fn(&_mod, ast_fold) -> _mod ,
     fold_native_mod: fn(&native_mod, ast_fold) -> native_mod ,
     fold_variant: fn(&variant_, ast_fold) -> variant_ ,
     fold_ident: fn(&ident, ast_fold) -> ident ,
     fold_path: fn(&path_, ast_fold) -> path_ ,
     fold_local: fn(&local_, ast_fold) -> local_ ,
     map_exprs: fn(fn(&@expr) -> @expr , (@expr)[]) -> (@expr)[] };

type a_f =
    {fold_crate: fn(&crate) -> crate ,
     fold_crate_directive: fn(&@crate_directive) -> @crate_directive ,
     fold_view_item: fn(&@view_item) -> @view_item ,
     fold_native_item: fn(&@native_item) -> @native_item ,
     fold_item: fn(&@item) -> @item ,
     fold_item_underscore: fn(&item_) -> item_ ,
     fold_method: fn(&@method) -> @method ,
     fold_block: fn(&blk) -> blk ,
     fold_stmt: fn(&@stmt) -> @stmt ,
     fold_arm: fn(&arm) -> arm ,
     fold_pat: fn(&@pat) -> @pat ,
     fold_decl: fn(&@decl) -> @decl ,
     fold_expr: fn(&@expr) -> @expr ,
     fold_ty: fn(&@ty) -> @ty ,
     fold_constr: fn(&@constr) -> @constr ,
     fold_fn: fn(&_fn) -> _fn ,
     fold_mod: fn(&_mod) -> _mod ,
     fold_native_mod: fn(&native_mod) -> native_mod ,
     fold_variant: fn(&variant) -> variant ,
     fold_ident: fn(&ident) -> ident ,
     fold_path: fn(&path) -> path ,
     fold_local: fn(&@local) -> @local ,
     map_exprs: fn(fn(&@expr) -> @expr , (@expr)[]) -> (@expr)[] };

//fn nf_dummy[T](&T node) -> T { fail; }
fn nf_crate_dummy(c: &crate) -> crate { fail; }
fn nf_crate_directive_dummy(c: &@crate_directive) -> @crate_directive {
    fail;
}
fn nf_view_item_dummy(v: &@view_item) -> @view_item { fail; }
fn nf_native_item_dummy(n: &@native_item) -> @native_item { fail; }
fn nf_item_dummy(i: &@item) -> @item { fail; }
fn nf_item_underscore_dummy(i: &item_) -> item_ { fail; }
fn nf_method_dummy(m: &@method) -> @method { fail; }
fn nf_blk_dummy(b: &blk) -> blk { fail; }
fn nf_stmt_dummy(s: &@stmt) -> @stmt { fail; }
fn nf_arm_dummy(a: &arm) -> arm { fail; }
fn nf_pat_dummy(p: &@pat) -> @pat { fail; }
fn nf_decl_dummy(d: &@decl) -> @decl { fail; }
fn nf_expr_dummy(e: &@expr) -> @expr { fail; }
fn nf_ty_dummy(t: &@ty) -> @ty { fail; }
fn nf_constr_dummy(c: &@constr) -> @constr { fail; }
fn nf_fn_dummy(f: &_fn) -> _fn { fail; }
fn nf_mod_dummy(m: &_mod) -> _mod { fail; }
fn nf_native_mod_dummy(n: &native_mod) -> native_mod { fail; }
fn nf_variant_dummy(v: &variant) -> variant { fail; }
fn nf_ident_dummy(i: &ident) -> ident { fail; }
fn nf_path_dummy(p: &path) -> path { fail; }
fn nf_obj_field_dummy(o: &obj_field) -> obj_field { fail; }
fn nf_local_dummy(o: &@local) -> @local { fail; }

/* some little folds that probably aren't useful to have in ast_fold itself*/

//used in noop_fold_item and noop_fold_crate and noop_fold_crate_directive
fn fold_meta_item_(mi: &@meta_item, fld: ast_fold) -> @meta_item {
    ret @{node:
              alt mi.node {
                meta_word(id) { meta_word(fld.fold_ident(id)) }
                meta_list(id, mis) {
                  let fold_meta_item = bind fold_meta_item_(_, fld);
                  meta_list(id, ivec::map(fold_meta_item, mis))
                }
                meta_name_value(id, s) {
                  meta_name_value(fld.fold_ident(id), s)
                }
              },
          span: mi.span};
}
//used in noop_fold_item and noop_fold_crate
fn fold_attribute_(at: &attribute, fmi: fn(&@meta_item) -> @meta_item ) ->
   attribute {
    ret {node: {style: at.node.style, value: *fmi(@at.node.value)},
         span: at.span};
}
//used in noop_fold_native_item and noop_fold_fn
fn fold_arg_(a: &arg, fld: ast_fold) -> arg {
    ret {mode: a.mode,
         ty: fld.fold_ty(a.ty),
         ident: fld.fold_ident(a.ident),
         id: a.id};
}
//used in noop_fold_expr, and possibly elsewhere in the future
fn fold_mac_(m: &mac, fld: ast_fold) -> mac {
    ret {node:
         alt m.node {
           mac_invoc(pth, arg, body) {
             mac_invoc(fld.fold_path(pth), fld.fold_expr(arg), body)
           }
           mac_embed_type(ty) { mac_embed_type(fld.fold_ty(ty)) }
           mac_embed_block(blk) { mac_embed_block(fld.fold_block(blk)) }
           mac_ellipsis. { mac_ellipsis }
         },
         span: m.span};
}





fn noop_fold_crate(c: &crate_, fld: ast_fold) -> crate_ {
    let fold_meta_item = bind fold_meta_item_(_, fld);
    let fold_attribute = bind fold_attribute_(_, fold_meta_item);

    ret {directives: ivec::map(fld.fold_crate_directive, c.directives),
         module: fld.fold_mod(c.module),
         attrs: ivec::map(fold_attribute, c.attrs),
         config: ivec::map(fold_meta_item, c.config)};
}

fn noop_fold_crate_directive(cd: &crate_directive_, fld: ast_fold) ->
   crate_directive_ {
    ret alt cd {
          cdir_src_mod(id, fname, attrs) {
            cdir_src_mod(fld.fold_ident(id), fname, attrs)
          }
          cdir_dir_mod(id, fname, cds, attrs) {
            cdir_dir_mod(fld.fold_ident(id), fname,
                         ivec::map(fld.fold_crate_directive, cds), attrs)
          }
          cdir_view_item(vi) { cdir_view_item(fld.fold_view_item(vi)) }
          cdir_syntax(_) { cd }
          cdir_auth(_, _) { cd }
        }
}

fn noop_fold_view_item(vi: &view_item_, fld: ast_fold) -> view_item_ {
    ret vi;
}


fn noop_fold_native_item(ni: &@native_item, fld: ast_fold) -> @native_item {
    let fold_arg = bind fold_arg_(_, fld);
    let fold_meta_item = bind fold_meta_item_(_, fld);
    let fold_attribute = bind fold_attribute_(_, fold_meta_item);

    ret @{ident: fld.fold_ident(ni.ident),
          attrs: ivec::map(fold_attribute, ni.attrs),
          node:
              alt ni.node {
                native_item_ty. { native_item_ty }
                native_item_fn(st, fdec, typms) {
                  native_item_fn(st,
                                 {inputs: ivec::map(fold_arg, fdec.inputs),
                                  output: fld.fold_ty(fdec.output),
                                  purity: fdec.purity,
                                  cf: fdec.cf,
                                  constraints:
                                      ivec::map(fld.fold_constr,
                                                fdec.constraints)}, typms)
                }
              },
          id: ni.id,
          span: ni.span};
}

fn noop_fold_item(i: &@item, fld: ast_fold) -> @item {
    let fold_meta_item = bind fold_meta_item_(_, fld);
    let fold_attribute = bind fold_attribute_(_, fold_meta_item);

    ret @{ident: fld.fold_ident(i.ident),
          attrs: ivec::map(fold_attribute, i.attrs),
          id: i.id,
          node: fld.fold_item_underscore(i.node),
          span: i.span};
}

fn noop_fold_item_underscore(i: &item_, fld: ast_fold) -> item_ {
    fn fold_obj_field_(of: &obj_field, fld: ast_fold) -> obj_field {
        ret {mut: of.mut,
             ty: fld.fold_ty(of.ty),
             ident: fld.fold_ident(of.ident),
             id: of.id};
    }
    let fold_obj_field = bind fold_obj_field_(_, fld);

    ret alt i {
          item_const(t, e) { item_const(fld.fold_ty(t), fld.fold_expr(e)) }
          item_fn(f, typms, il) { item_fn(fld.fold_fn(f), typms, il) }
          item_mod(m) { item_mod(fld.fold_mod(m)) }
          item_native_mod(nm) { item_native_mod(fld.fold_native_mod(nm)) }
          item_ty(t, typms) { item_ty(fld.fold_ty(t), typms) }
          item_tag(variants, typms) {
            item_tag(ivec::map(fld.fold_variant, variants), typms)
          }
          item_obj(o, typms, d) {
            item_obj({fields: ivec::map(fold_obj_field, o.fields),
                      methods: ivec::map(fld.fold_method, o.methods)},
                     typms, d)
          }
          item_res(dtor, did, typms, cid) {
            item_res(fld.fold_fn(dtor), did, typms, cid)
          }
        };
}

fn noop_fold_method(m: &method_, fld: ast_fold) -> method_ {
    ret {ident: fld.fold_ident(m.ident), meth: fld.fold_fn(m.meth), id: m.id};
}


fn noop_fold_block(b: &blk_, fld: ast_fold) -> blk_ {
    ret {stmts: ivec::map(fld.fold_stmt, b.stmts),
         expr: option::map(fld.fold_expr, b.expr),
         id: b.id};
}

fn noop_fold_stmt(s: &stmt_, fld: ast_fold) -> stmt_ {
    ret alt s {
          stmt_decl(d, nid) { stmt_decl(fld.fold_decl(d), nid) }
          stmt_expr(e, nid) { stmt_expr(fld.fold_expr(e), nid) }
          stmt_crate_directive(cd) {
            stmt_crate_directive(fld.fold_crate_directive(cd))
          }
        };
}

fn noop_fold_arm(a: &arm, fld: ast_fold) -> arm {
    ret {pats: ivec::map(fld.fold_pat, a.pats),
         block: fld.fold_block(a.block)};
}

fn noop_fold_pat(p: &pat_, fld: ast_fold) -> pat_ {
    ret alt p {
          pat_wild. { p }
          pat_bind(ident) { pat_bind(fld.fold_ident(ident)) }
          pat_lit(_) { p }
          pat_tag(pth, pats) {
            pat_tag(fld.fold_path(pth), ivec::map(fld.fold_pat, pats))
          }
          pat_rec(fields, etc) {
            let fs = ~[];
            for f: ast::field_pat  in fields {
                fs += ~[{ident: f.ident, pat: fld.fold_pat(f.pat)}];
            }
            pat_rec(fs, etc)
          }
          pat_box(inner) { pat_box(fld.fold_pat(inner)) }
        };
}

fn noop_fold_decl(d: &decl_, fld: ast_fold) -> decl_ {
    ret alt d {
          decl_local(ls) { decl_local(ivec::map(fld.fold_local, ls)) }
          decl_item(it) { decl_item(fld.fold_item(it)) }
        }
}

fn noop_fold_expr(e: &expr_, fld: ast_fold) -> expr_ {
    fn fold_field_(field: &field, fld: ast_fold) -> field {
        ret {node:
                 {mut: field.node.mut,
                  ident: fld.fold_ident(field.node.ident),
                  expr: fld.fold_expr(field.node.expr)},
             span: field.span};
    }
    let fold_field = bind fold_field_(_, fld);
    fn fold_anon_obj_(ao: &anon_obj, fld: ast_fold) -> anon_obj {
        fn fold_anon_obj_field_(aof: &anon_obj_field, fld: ast_fold) ->
           anon_obj_field {
            ret {mut: aof.mut,
                 ty: fld.fold_ty(aof.ty),
                 expr: fld.fold_expr(aof.expr),
                 ident: fld.fold_ident(aof.ident),
                 id: aof.id};
        }
        let fold_anon_obj_field = bind fold_anon_obj_field_(_, fld);


        ret {fields:
                 alt ao.fields {
                   option::none. { ao.fields }
                   option::some(v) {
                     option::some(ivec::map(fold_anon_obj_field, v))
                   }
                 },
             methods: ivec::map(fld.fold_method, ao.methods),
             inner_obj: option::map(fld.fold_expr, ao.inner_obj)}
    }
    let fold_anon_obj = bind fold_anon_obj_(_, fld);

    let fold_mac = bind fold_mac_(_, fld);


    ret alt e {
          expr_vec(exprs, mut, seq_kind) {
            expr_vec(fld.map_exprs(fld.fold_expr, exprs), mut, seq_kind)
          }
          expr_rec(fields, maybe_expr) {
            expr_rec(ivec::map(fold_field, fields),
                     option::map(fld.fold_expr, maybe_expr))
          }
          expr_call(f, args) {
            expr_call(fld.fold_expr(f), fld.map_exprs(fld.fold_expr, args))
          }
          expr_self_method(id) { expr_self_method(fld.fold_ident(id)) }
          expr_bind(f, args) {
            let opt_map_se = bind option::map(fld.fold_expr, _);
            expr_bind(fld.fold_expr(f), ivec::map(opt_map_se, args))
          }
          expr_spawn(spawn_dom, name, f, args) {
            expr_spawn(spawn_dom, name, fld.fold_expr(f),
                       fld.map_exprs(fld.fold_expr, args))
          }
          expr_binary(binop, lhs, rhs) {
            expr_binary(binop, fld.fold_expr(lhs), fld.fold_expr(rhs))
          }
          expr_unary(binop, ohs) { expr_unary(binop, fld.fold_expr(ohs)) }
          expr_lit(_) { e }
          expr_cast(expr, ty) { expr_cast(fld.fold_expr(expr), ty) }
          expr_if(cond, tr, fl) {
            expr_if(fld.fold_expr(cond), fld.fold_block(tr),
                    option::map(fld.fold_expr, fl))
          }
          expr_ternary(cond, tr, fl) {
            expr_ternary(fld.fold_expr(cond), fld.fold_expr(tr),
                         fld.fold_expr(fl))
          }
          expr_while(cond, body) {
            expr_while(fld.fold_expr(cond), fld.fold_block(body))
          }
          expr_for(decl, expr, blk) {
            expr_for(fld.fold_local(decl), fld.fold_expr(expr),
                     fld.fold_block(blk))
          }
          expr_for_each(decl, expr, blk) {
            expr_for_each(fld.fold_local(decl), fld.fold_expr(expr),
                          fld.fold_block(blk))
          }
          expr_do_while(blk, expr) {
            expr_do_while(fld.fold_block(blk), fld.fold_expr(expr))
          }
          expr_alt(expr, arms) {
            expr_alt(fld.fold_expr(expr), ivec::map(fld.fold_arm, arms))
          }
          expr_fn(f) { expr_fn(fld.fold_fn(f)) }
          expr_block(blk) { expr_block(fld.fold_block(blk)) }
          expr_move(el, er) {
            expr_move(fld.fold_expr(el), fld.fold_expr(er))
          }
          expr_assign(el, er) {
            expr_assign(fld.fold_expr(el), fld.fold_expr(er))
          }
          expr_swap(el, er) {
            expr_swap(fld.fold_expr(el), fld.fold_expr(er))
          }
          expr_assign_op(op, el, er) {
            expr_assign_op(op, fld.fold_expr(el), fld.fold_expr(er))
          }
          expr_send(el, er) {
            expr_send(fld.fold_expr(el), fld.fold_expr(er))
          }
          expr_recv(el, er) {
            expr_recv(fld.fold_expr(el), fld.fold_expr(er))
          }
          expr_field(el, id) {
            expr_field(fld.fold_expr(el), fld.fold_ident(id))
          }
          expr_index(el, er) {
            expr_index(fld.fold_expr(el), fld.fold_expr(er))
          }
          expr_path(pth) { expr_path(fld.fold_path(pth)) }
          expr_fail(e) { expr_fail(option::map(fld.fold_expr, e)) }
          expr_break. { e }
          expr_cont. { e }
          expr_ret(e) { expr_ret(option::map(fld.fold_expr, e)) }
          expr_put(e) { expr_put(option::map(fld.fold_expr, e)) }
          expr_be(e) { expr_be(fld.fold_expr(e)) }
          expr_log(lv, e) { expr_log(lv, fld.fold_expr(e)) }
          expr_assert(e) { expr_assert(fld.fold_expr(e)) }
          expr_check(m, e) { expr_check(m, fld.fold_expr(e)) }
          expr_if_check(cond, tr, fl) {
            expr_if_check(fld.fold_expr(cond), fld.fold_block(tr),
                          option::map(fld.fold_expr, fl))
          }
          expr_port(ot) {
            expr_port(alt ot {
                        option::some(t) { option::some(fld.fold_ty(t)) }
                        option::none. { option::none }
                      })
          }
          expr_chan(e) { expr_chan(fld.fold_expr(e)) }
          expr_anon_obj(ao) { expr_anon_obj(fold_anon_obj(ao)) }
          expr_mac(mac) { expr_mac(fold_mac(mac)) }
        }
}

fn noop_fold_ty(t: &ty_, fld: ast_fold) -> ty_ {
    //drop in ty::fold_ty here if necessary
    ret t;
}

fn noop_fold_constr(c: &constr_, fld: ast_fold) -> constr_ {
    {path: fld.fold_path(c.path), args: c.args, id: c.id}
}

// functions just don't get spans, for some reason
fn noop_fold_fn(f: &_fn, fld: ast_fold) -> _fn {
    let fold_arg = bind fold_arg_(_, fld);

    ret {decl:
             {inputs: ivec::map(fold_arg, f.decl.inputs),
              output: fld.fold_ty(f.decl.output),
              purity: f.decl.purity,
              cf: f.decl.cf,
              constraints: ivec::map(fld.fold_constr, f.decl.constraints)},
         proto: f.proto,
         body: fld.fold_block(f.body)};
}

// ...nor do modules
fn noop_fold_mod(m: &_mod, fld: ast_fold) -> _mod {
    ret {view_items: ivec::map(fld.fold_view_item, m.view_items),
         items: ivec::map(fld.fold_item, m.items)};
}

fn noop_fold_native_mod(nm: &native_mod, fld: ast_fold) -> native_mod {
    ret {native_name: nm.native_name,
         abi: nm.abi,
         view_items: ivec::map(fld.fold_view_item, nm.view_items),
         items: ivec::map(fld.fold_native_item, nm.items)}
}

fn noop_fold_variant(v: &variant_, fld: ast_fold) -> variant_ {
    fn fold_variant_arg_(va: &variant_arg, fld: ast_fold) -> variant_arg {
        ret {ty: fld.fold_ty(va.ty), id: va.id};
    }
    let fold_variant_arg = bind fold_variant_arg_(_, fld);
    ret {name: v.name, args: ivec::map(fold_variant_arg, v.args), id: v.id};
}

fn noop_fold_ident(i: &ident, fld: ast_fold) -> ident { ret i; }

fn noop_fold_path(p: &path_, fld: ast_fold) -> path_ {
    ret {global: p.global,
         idents: ivec::map(fld.fold_ident, p.idents),
         types: ivec::map(fld.fold_ty, p.types)};
}

fn noop_fold_local(l: &local_, fld: ast_fold) -> local_ {
    ret {ty: option::map(fld.fold_ty, l.ty),
         pat: fld.fold_pat(l.pat),
         init: alt l.init {
           option::none[initializer]. { l.init }
           option::some[initializer](init) {
             option::some[initializer]({op: init.op,
                                        expr: fld.fold_expr(init.expr)})
           }
         },
         id: l.id};
}

/* temporarily eta-expand because of a compiler bug with using `fn[T]` as a
   value */
fn noop_map_exprs(f: fn(&@expr) -> @expr , es: (@expr)[]) -> (@expr)[] {
    ret ivec::map(f, es);
}


fn default_ast_fold() -> @ast_fold_precursor {
    ret @{fold_crate: noop_fold_crate,
          fold_crate_directive: noop_fold_crate_directive,
          fold_view_item: noop_fold_view_item,
          fold_native_item: noop_fold_native_item,
          fold_item: noop_fold_item,
          fold_item_underscore: noop_fold_item_underscore,
          fold_method: noop_fold_method,
          fold_block: noop_fold_block,
          fold_stmt: noop_fold_stmt,
          fold_arm: noop_fold_arm,
          fold_pat: noop_fold_pat,
          fold_decl: noop_fold_decl,
          fold_expr: noop_fold_expr,
          fold_ty: noop_fold_ty,
          fold_constr: noop_fold_constr,
          fold_fn: noop_fold_fn,
          fold_mod: noop_fold_mod,
          fold_native_mod: noop_fold_native_mod,
          fold_variant: noop_fold_variant,
          fold_ident: noop_fold_ident,
          fold_path: noop_fold_path,
          fold_local: noop_fold_local,
          map_exprs: noop_map_exprs};
}

fn dummy_out(a: ast_fold) {
    *a =
        {fold_crate: nf_crate_dummy,
         fold_crate_directive: nf_crate_directive_dummy,
         fold_view_item: nf_view_item_dummy,
         fold_native_item: nf_native_item_dummy,
         fold_item: nf_item_dummy,
         fold_item_underscore: nf_item_underscore_dummy,
         fold_method: nf_method_dummy,
         fold_block: nf_blk_dummy,
         fold_stmt: nf_stmt_dummy,
         fold_arm: nf_arm_dummy,
         fold_pat: nf_pat_dummy,
         fold_decl: nf_decl_dummy,
         fold_expr: nf_expr_dummy,
         fold_ty: nf_ty_dummy,
         fold_constr: nf_constr_dummy,
         fold_fn: nf_fn_dummy,
         fold_mod: nf_mod_dummy,
         fold_native_mod: nf_native_mod_dummy,
         fold_variant: nf_variant_dummy,
         fold_ident: nf_ident_dummy,
         fold_path: nf_path_dummy,
         fold_local: nf_local_dummy,
         map_exprs: noop_map_exprs};
}


fn make_fold(afp: &ast_fold_precursor) -> ast_fold {
    let result: ast_fold =
        @mutable {fold_crate: nf_crate_dummy,
                  fold_crate_directive: nf_crate_directive_dummy,
                  fold_view_item: nf_view_item_dummy,
                  fold_native_item: nf_native_item_dummy,
                  fold_item: nf_item_dummy,
                  fold_item_underscore: nf_item_underscore_dummy,
                  fold_method: nf_method_dummy,
                  fold_block: nf_blk_dummy,
                  fold_stmt: nf_stmt_dummy,
                  fold_arm: nf_arm_dummy,
                  fold_pat: nf_pat_dummy,
                  fold_decl: nf_decl_dummy,
                  fold_expr: nf_expr_dummy,
                  fold_ty: nf_ty_dummy,
                  fold_constr: nf_constr_dummy,
                  fold_fn: nf_fn_dummy,
                  fold_mod: nf_mod_dummy,
                  fold_native_mod: nf_native_mod_dummy,
                  fold_variant: nf_variant_dummy,
                  fold_ident: nf_ident_dummy,
                  fold_path: nf_path_dummy,
                  fold_local: nf_local_dummy,
                  map_exprs: noop_map_exprs};

    /* naturally, a macro to write these would be nice */
    fn f_crate(afp: &ast_fold_precursor, f: ast_fold, c: &crate) -> crate {
        ret {node: afp.fold_crate(c.node, f), span: c.span};
    }
    fn f_crate_directive(afp: &ast_fold_precursor, f: ast_fold,
                         c: &@crate_directive) -> @crate_directive {
        ret @{node: afp.fold_crate_directive(c.node, f), span: c.span};
    }
    fn f_view_item(afp: &ast_fold_precursor, f: ast_fold, x: &@view_item) ->
       @view_item {
        ret @{node: afp.fold_view_item(x.node, f), span: x.span};
    }
    fn f_native_item(afp: &ast_fold_precursor, f: ast_fold, x: &@native_item)
       -> @native_item {
        ret afp.fold_native_item(x, f);
    }
    fn f_item(afp: &ast_fold_precursor, f: ast_fold, i: &@item) -> @item {
        ret afp.fold_item(i, f);
    }
    fn f_item_underscore(afp: &ast_fold_precursor, f: ast_fold, i: &item_) ->
       item_ {
        ret afp.fold_item_underscore(i, f);
    }
    fn f_method(afp: &ast_fold_precursor, f: ast_fold, x: &@method) ->
       @method {
        ret @{node: afp.fold_method(x.node, f), span: x.span};
    }
    fn f_block(afp: &ast_fold_precursor, f: ast_fold, x: &blk) -> blk {
        ret {node: afp.fold_block(x.node, f), span: x.span};
    }
    fn f_stmt(afp: &ast_fold_precursor, f: ast_fold, x: &@stmt) -> @stmt {
        ret @{node: afp.fold_stmt(x.node, f), span: x.span};
    }
    fn f_arm(afp: &ast_fold_precursor, f: ast_fold, x: &arm) -> arm {
        ret afp.fold_arm(x, f);
    }
    fn f_pat(afp: &ast_fold_precursor, f: ast_fold, x: &@pat) -> @pat {
        ret @{id: x.id, node: afp.fold_pat(x.node, f), span: x.span};
    }
    fn f_decl(afp: &ast_fold_precursor, f: ast_fold, x: &@decl) -> @decl {
        ret @{node: afp.fold_decl(x.node, f), span: x.span};
    }
    fn f_expr(afp: &ast_fold_precursor, f: ast_fold, x: &@expr) -> @expr {
        ret @{id: x.id, node: afp.fold_expr(x.node, f), span: x.span};
    }
    fn f_ty(afp: &ast_fold_precursor, f: ast_fold, x: &@ty) -> @ty {
        ret @{node: afp.fold_ty(x.node, f), span: x.span};
    }
    fn f_constr(afp: &ast_fold_precursor, f: ast_fold, x: &@ast::constr) ->
       @ast::constr {
        ret @{node: afp.fold_constr(x.node, f), span: x.span};
    }
    fn f_fn(afp: &ast_fold_precursor, f: ast_fold, x: &_fn) -> _fn {
        ret afp.fold_fn(x, f);
    }
    fn f_mod(afp: &ast_fold_precursor, f: ast_fold, x: &_mod) -> _mod {
        ret afp.fold_mod(x, f);
    }
    fn f_native_mod(afp: &ast_fold_precursor, f: ast_fold, x: &native_mod) ->
       native_mod {
        ret afp.fold_native_mod(x, f);
    }
    fn f_variant(afp: &ast_fold_precursor, f: ast_fold, x: &variant) ->
       variant {
        ret {node: afp.fold_variant(x.node, f), span: x.span};
    }
    fn f_ident(afp: &ast_fold_precursor, f: ast_fold, x: &ident) -> ident {
        ret afp.fold_ident(x, f);
    }
    fn f_path(afp: &ast_fold_precursor, f: ast_fold, x: &path) -> path {
        ret {node: afp.fold_path(x.node, f), span: x.span};
    }
    fn f_local(afp: &ast_fold_precursor, f: ast_fold, x: &@local) -> @local {
        ret @{node: afp.fold_local(x.node, f), span: x.span};
    }

    *result =
        {fold_crate: bind f_crate(afp, result, _),
         fold_crate_directive: bind f_crate_directive(afp, result, _),
         fold_view_item: bind f_view_item(afp, result, _),
         fold_native_item: bind f_native_item(afp, result, _),
         fold_item: bind f_item(afp, result, _),
         fold_item_underscore: bind f_item_underscore(afp, result, _),
         fold_method: bind f_method(afp, result, _),
         fold_block: bind f_block(afp, result, _),
         fold_stmt: bind f_stmt(afp, result, _),
         fold_arm: bind f_arm(afp, result, _),
         fold_pat: bind f_pat(afp, result, _),
         fold_decl: bind f_decl(afp, result, _),
         fold_expr: bind f_expr(afp, result, _),
         fold_ty: bind f_ty(afp, result, _),
         fold_constr: bind f_constr(afp, result, _),
         fold_fn: bind f_fn(afp, result, _),
         fold_mod: bind f_mod(afp, result, _),
         fold_native_mod: bind f_native_mod(afp, result, _),
         fold_variant: bind f_variant(afp, result, _),
         fold_ident: bind f_ident(afp, result, _),
         fold_path: bind f_path(afp, result, _),
         fold_local: bind f_local(afp, result, _),
         map_exprs: afp.map_exprs};
    ret result;
}


//
// Local Variables:
// mode: rust
// fill-column: 78;
// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
// compile-command: "make -k -C $RBUILD 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
// End:
//