src/libsyntax/fold.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! A Folder represents an AST->AST fold; it accepts an AST piece,
  12 //! and returns a piece of the same type. So, for instance, macro
  13 //! expansion is a Folder that walks over an AST and produces another
  14 //! AST.
  15 //!
  16 //! Note: using a Folder (other than the MacroExpander Folder) on
  17 //! an AST before macro expansion is probably a bad idea. For instance,
  18 //! a folder renaming item names in a module will miss all of those
  19 //! that are created by the expansion of a macro.
  20
  21 use ast::*;
  22 use ast;
  23 use syntax_pos::Span;
  24 use codemap::{Spanned, respan};
  25 use parse::token::{self, Token};
  26 use ptr::P;
  27 use symbol::keywords;
  28 use tokenstream::*;
  29 use util::small_vector::SmallVector;
  30 use util::move_map::MoveMap;
  31
  32 use rustc_data_structures::sync::Lrc;
  33
  34 pub trait Folder : Sized {
  35     // Any additions to this trait should happen in form
  36     // of a call to a public `noop_*` function that only calls
  37     // out to the folder again, not other `noop_*` functions.
  38     //
  39     // This is a necessary API workaround to the problem of not
  40     // being able to call out to the super default method
  41     // in an overridden default method.
  42
  43     fn fold_crate(&mut self, c: Crate) -> Crate {
  44         noop_fold_crate(c, self)
  45     }
  46
  47     fn fold_meta_items(&mut self, meta_items: Vec<MetaItem>) -> Vec<MetaItem> {
  48         noop_fold_meta_items(meta_items, self)
  49     }
  50
  51     fn fold_meta_list_item(&mut self, list_item: NestedMetaItem) -> NestedMetaItem {
  52         noop_fold_meta_list_item(list_item, self)
  53     }
  54
  55     fn fold_meta_item(&mut self, meta_item: MetaItem) -> MetaItem {
  56         noop_fold_meta_item(meta_item, self)
  57     }
  58
  59     fn fold_use_tree(&mut self, use_tree: UseTree) -> UseTree {
  60         noop_fold_use_tree(use_tree, self)
  61     }
  62
  63     fn fold_foreign_item(&mut self, ni: ForeignItem) -> SmallVector<ForeignItem> {
  64         noop_fold_foreign_item(ni, self)
  65     }
  66
  67     fn fold_foreign_item_simple(&mut self, ni: ForeignItem) -> ForeignItem {
  68         noop_fold_foreign_item_simple(ni, self)
  69     }
  70
  71     fn fold_item(&mut self, i: P<Item>) -> SmallVector<P<Item>> {
  72         noop_fold_item(i, self)
  73     }
  74
  75     fn fold_item_simple(&mut self, i: Item) -> Item {
  76         noop_fold_item_simple(i, self)
  77     }
  78
  79     fn fold_fn_header(&mut self, header: FnHeader) -> FnHeader {
  80         noop_fold_fn_header(header, self)
  81     }
  82
  83     fn fold_struct_field(&mut self, sf: StructField) -> StructField {
  84         noop_fold_struct_field(sf, self)
  85     }
  86
  87     fn fold_item_kind(&mut self, i: ItemKind) -> ItemKind {
  88         noop_fold_item_kind(i, self)
  89     }
  90
  91     fn fold_trait_item(&mut self, i: TraitItem) -> SmallVector<TraitItem> {
  92         noop_fold_trait_item(i, self)
  93     }
  94
  95     fn fold_impl_item(&mut self, i: ImplItem) -> SmallVector<ImplItem> {
  96         noop_fold_impl_item(i, self)
  97     }
  98
  99     fn fold_fn_decl(&mut self, d: P<FnDecl>) -> P<FnDecl> {
 100         noop_fold_fn_decl(d, self)
 101     }
 102
 103     fn fold_block(&mut self, b: P<Block>) -> P<Block> {
 104         noop_fold_block(b, self)
 105     }
 106
 107     fn fold_stmt(&mut self, s: Stmt) -> SmallVector<Stmt> {
 108         noop_fold_stmt(s, self)
 109     }
 110
 111     fn fold_arm(&mut self, a: Arm) -> Arm {
 112         noop_fold_arm(a, self)
 113     }
 114
 115     fn fold_pat(&mut self, p: P<Pat>) -> P<Pat> {
 116         noop_fold_pat(p, self)
 117     }
 118
 119     fn fold_anon_const(&mut self, c: AnonConst) -> AnonConst {
 120         noop_fold_anon_const(c, self)
 121     }
 122
 123     fn fold_expr(&mut self, e: P<Expr>) -> P<Expr> {
 124         e.map(|e| noop_fold_expr(e, self))
 125     }
 126
 127     fn fold_range_end(&mut self, re: RangeEnd) -> RangeEnd {
 128         noop_fold_range_end(re, self)
 129     }
 130
 131     fn fold_opt_expr(&mut self, e: P<Expr>) -> Option<P<Expr>> {
 132         noop_fold_opt_expr(e, self)
 133     }
 134
 135     fn fold_exprs(&mut self, es: Vec<P<Expr>>) -> Vec<P<Expr>> {
 136         noop_fold_exprs(es, self)
 137     }
 138
 139     fn fold_generic_arg(&mut self, arg: GenericArg) -> GenericArg {
 140         match arg {
 141             GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.fold_lifetime(lt)),
 142             GenericArg::Type(ty) => GenericArg::Type(self.fold_ty(ty)),
 143         }
 144     }
 145
 146     fn fold_ty(&mut self, t: P<Ty>) -> P<Ty> {
 147         noop_fold_ty(t, self)
 148     }
 149
 150     fn fold_lifetime(&mut self, l: Lifetime) -> Lifetime {
 151         noop_fold_lifetime(l, self)
 152     }
 153
 154     fn fold_ty_binding(&mut self, t: TypeBinding) -> TypeBinding {
 155         noop_fold_ty_binding(t, self)
 156     }
 157
 158     fn fold_mod(&mut self, m: Mod) -> Mod {
 159         noop_fold_mod(m, self)
 160     }
 161
 162     fn fold_foreign_mod(&mut self, nm: ForeignMod) -> ForeignMod {
 163         noop_fold_foreign_mod(nm, self)
 164     }
 165
 166     fn fold_global_asm(&mut self, ga: P<GlobalAsm>) -> P<GlobalAsm> {
 167         noop_fold_global_asm(ga, self)
 168     }
 169
 170     fn fold_variant(&mut self, v: Variant) -> Variant {
 171         noop_fold_variant(v, self)
 172     }
 173
 174     fn fold_ident(&mut self, i: Ident) -> Ident {
 175         noop_fold_ident(i, self)
 176     }
 177
 178     fn fold_usize(&mut self, i: usize) -> usize {
 179         noop_fold_usize(i, self)
 180     }
 181
 182     fn fold_path(&mut self, p: Path) -> Path {
 183         noop_fold_path(p, self)
 184     }
 185
 186     fn fold_qpath(&mut self, qs: Option<QSelf>, p: Path) -> (Option<QSelf>, Path) {
 187         noop_fold_qpath(qs, p, self)
 188     }
 189
 190     fn fold_generic_args(&mut self, p: GenericArgs) -> GenericArgs {
 191         noop_fold_generic_args(p, self)
 192     }
 193
 194     fn fold_angle_bracketed_parameter_data(&mut self, p: AngleBracketedArgs)
 195                                            -> AngleBracketedArgs
 196     {
 197         noop_fold_angle_bracketed_parameter_data(p, self)
 198     }
 199
 200     fn fold_parenthesized_parameter_data(&mut self, p: ParenthesisedArgs)
 201                                          -> ParenthesisedArgs
 202     {
 203         noop_fold_parenthesized_parameter_data(p, self)
 204     }
 205
 206     fn fold_local(&mut self, l: P<Local>) -> P<Local> {
 207         noop_fold_local(l, self)
 208     }
 209
 210     fn fold_mac(&mut self, _mac: Mac) -> Mac {
 211         panic!("fold_mac disabled by default");
 212         // NB: see note about macros above.
 213         // if you really want a folder that
 214         // works on macros, use this
 215         // definition in your trait impl:
 216         // fold::noop_fold_mac(_mac, self)
 217     }
 218
 219     fn fold_macro_def(&mut self, def: MacroDef) -> MacroDef {
 220         noop_fold_macro_def(def, self)
 221     }
 222
 223     fn fold_label(&mut self, label: Label) -> Label {
 224         noop_fold_label(label, self)
 225     }
 226
 227     fn fold_attribute(&mut self, at: Attribute) -> Option<Attribute> {
 228         noop_fold_attribute(at, self)
 229     }
 230
 231     fn fold_arg(&mut self, a: Arg) -> Arg {
 232         noop_fold_arg(a, self)
 233     }
 234
 235     fn fold_generics(&mut self, generics: Generics) -> Generics {
 236         noop_fold_generics(generics, self)
 237     }
 238
 239     fn fold_trait_ref(&mut self, p: TraitRef) -> TraitRef {
 240         noop_fold_trait_ref(p, self)
 241     }
 242
 243     fn fold_poly_trait_ref(&mut self, p: PolyTraitRef) -> PolyTraitRef {
 244         noop_fold_poly_trait_ref(p, self)
 245     }
 246
 247     fn fold_variant_data(&mut self, vdata: VariantData) -> VariantData {
 248         noop_fold_variant_data(vdata, self)
 249     }
 250
 251     fn fold_generic_param(&mut self, param: GenericParam) -> GenericParam {
 252         noop_fold_generic_param(param, self)
 253     }
 254
 255     fn fold_generic_params(&mut self, params: Vec<GenericParam>) -> Vec<GenericParam> {
 256         noop_fold_generic_params(params, self)
 257     }
 258
 259     fn fold_tt(&mut self, tt: TokenTree) -> TokenTree {
 260         noop_fold_tt(tt, self)
 261     }
 262
 263     fn fold_tts(&mut self, tts: TokenStream) -> TokenStream {
 264         noop_fold_tts(tts, self)
 265     }
 266
 267     fn fold_token(&mut self, t: token::Token) -> token::Token {
 268         noop_fold_token(t, self)
 269     }
 270
 271     fn fold_interpolated(&mut self, nt: token::Nonterminal) -> token::Nonterminal {
 272         noop_fold_interpolated(nt, self)
 273     }
 274
 275     fn fold_opt_bounds(&mut self, b: Option<GenericBounds>) -> Option<GenericBounds> {
 276         noop_fold_opt_bounds(b, self)
 277     }
 278
 279     fn fold_bounds(&mut self, b: GenericBounds) -> GenericBounds {
 280         noop_fold_bounds(b, self)
 281     }
 282
 283     fn fold_param_bound(&mut self, tpb: GenericBound) -> GenericBound {
 284         noop_fold_param_bound(tpb, self)
 285     }
 286
 287     fn fold_mt(&mut self, mt: MutTy) -> MutTy {
 288         noop_fold_mt(mt, self)
 289     }
 290
 291     fn fold_field(&mut self, field: Field) -> Field {
 292         noop_fold_field(field, self)
 293     }
 294
 295     fn fold_where_clause(&mut self, where_clause: WhereClause)
 296                          -> WhereClause {
 297         noop_fold_where_clause(where_clause, self)
 298     }
 299
 300     fn fold_where_predicate(&mut self, where_predicate: WherePredicate)
 301                             -> WherePredicate {
 302         noop_fold_where_predicate(where_predicate, self)
 303     }
 304
 305     fn fold_vis(&mut self, vis: Visibility) -> Visibility {
 306         noop_fold_vis(vis, self)
 307     }
 308
 309     fn new_id(&mut self, i: NodeId) -> NodeId {
 310         i
 311     }
 312
 313     fn new_span(&mut self, sp: Span) -> Span {
 314         sp
 315     }
 316 }
 317
 318 pub fn noop_fold_meta_items<T: Folder>(meta_items: Vec<MetaItem>, fld: &mut T) -> Vec<MetaItem> {
 319     meta_items.move_map(|x| fld.fold_meta_item(x))
 320 }
 321
 322 pub fn noop_fold_use_tree<T: Folder>(use_tree: UseTree, fld: &mut T) -> UseTree {
 323     UseTree {
 324         span: fld.new_span(use_tree.span),
 325         prefix: fld.fold_path(use_tree.prefix),
 326         kind: match use_tree.kind {
 327             UseTreeKind::Simple(rename, id1, id2) =>
 328                 UseTreeKind::Simple(rename.map(|ident| fld.fold_ident(ident)),
 329                                     fld.new_id(id1), fld.new_id(id2)),
 330             UseTreeKind::Glob => UseTreeKind::Glob,
 331             UseTreeKind::Nested(items) => UseTreeKind::Nested(items.move_map(|(tree, id)| {
 332                 (fld.fold_use_tree(tree), fld.new_id(id))
 333             })),
 334         },
 335     }
 336 }
 337
 338 pub fn fold_attrs<T: Folder>(attrs: Vec<Attribute>, fld: &mut T) -> Vec<Attribute> {
 339     attrs.move_flat_map(|x| fld.fold_attribute(x))
 340 }
 341
 342 pub fn fold_thin_attrs<T: Folder>(attrs: ThinVec<Attribute>, fld: &mut T) -> ThinVec<Attribute> {
 343     fold_attrs(attrs.into(), fld).into()
 344 }
 345
 346 pub fn noop_fold_arm<T: Folder>(Arm {attrs, pats, guard, body}: Arm,
 347     fld: &mut T) -> Arm {
 348     Arm {
 349         attrs: fold_attrs(attrs, fld),
 350         pats: pats.move_map(|x| fld.fold_pat(x)),
 351         guard: guard.map(|x| fld.fold_expr(x)),
 352         body: fld.fold_expr(body),
 353     }
 354 }
 355
 356 pub fn noop_fold_ty_binding<T: Folder>(b: TypeBinding, fld: &mut T) -> TypeBinding {
 357     TypeBinding {
 358         id: fld.new_id(b.id),
 359         ident: fld.fold_ident(b.ident),
 360         ty: fld.fold_ty(b.ty),
 361         span: fld.new_span(b.span),
 362     }
 363 }
 364
 365 pub fn noop_fold_ty<T: Folder>(t: P<Ty>, fld: &mut T) -> P<Ty> {
 366     t.map(|Ty {id, node, span}| Ty {
 367         id: fld.new_id(id),
 368         node: match node {
 369             TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err => node,
 370             TyKind::Slice(ty) => TyKind::Slice(fld.fold_ty(ty)),
 371             TyKind::Ptr(mt) => TyKind::Ptr(fld.fold_mt(mt)),
 372             TyKind::Rptr(region, mt) => {
 373                 TyKind::Rptr(region.map(|lt| noop_fold_lifetime(lt, fld)), fld.fold_mt(mt))
 374             }
 375             TyKind::BareFn(f) => {
 376                 TyKind::BareFn(f.map(|BareFnTy {generic_params, unsafety, abi, decl}| BareFnTy {
 377                     generic_params: fld.fold_generic_params(generic_params),
 378                     unsafety,
 379                     abi,
 380                     decl: fld.fold_fn_decl(decl)
 381                 }))
 382             }
 383             TyKind::Never => node,
 384             TyKind::Tup(tys) => TyKind::Tup(tys.move_map(|ty| fld.fold_ty(ty))),
 385             TyKind::Paren(ty) => TyKind::Paren(fld.fold_ty(ty)),
 386             TyKind::Path(qself, path) => {
 387                 let (qself, path) = fld.fold_qpath(qself, path);
 388                 TyKind::Path(qself, path)
 389             }
 390             TyKind::Array(ty, length) => {
 391                 TyKind::Array(fld.fold_ty(ty), fld.fold_anon_const(length))
 392             }
 393             TyKind::Typeof(expr) => {
 394                 TyKind::Typeof(fld.fold_anon_const(expr))
 395             }
 396             TyKind::TraitObject(bounds, syntax) => {
 397                 TyKind::TraitObject(bounds.move_map(|b| fld.fold_param_bound(b)), syntax)
 398             }
 399             TyKind::ImplTrait(bounds) => {
 400                 TyKind::ImplTrait(bounds.move_map(|b| fld.fold_param_bound(b)))
 401             }
 402             TyKind::Mac(mac) => {
 403                 TyKind::Mac(fld.fold_mac(mac))
 404             }
 405         },
 406         span: fld.new_span(span)
 407     })
 408 }
 409
 410 pub fn noop_fold_foreign_mod<T: Folder>(ForeignMod {abi, items}: ForeignMod,
 411                                         fld: &mut T) -> ForeignMod {
 412     ForeignMod {
 413         abi,
 414         items: items.move_flat_map(|x| fld.fold_foreign_item(x)),
 415     }
 416 }
 417
 418 pub fn noop_fold_global_asm<T: Folder>(ga: P<GlobalAsm>,
 419                                        _: &mut T) -> P<GlobalAsm> {
 420     ga
 421 }
 422
 423 pub fn noop_fold_variant<T: Folder>(v: Variant, fld: &mut T) -> Variant {
 424     Spanned {
 425         node: Variant_ {
 426             ident: fld.fold_ident(v.node.ident),
 427             attrs: fold_attrs(v.node.attrs, fld),
 428             data: fld.fold_variant_data(v.node.data),
 429             disr_expr: v.node.disr_expr.map(|e| fld.fold_anon_const(e)),
 430         },
 431         span: fld.new_span(v.span),
 432     }
 433 }
 434
 435 pub fn noop_fold_ident<T: Folder>(ident: Ident, fld: &mut T) -> Ident {
 436     Ident::new(ident.name, fld.new_span(ident.span))
 437 }
 438
 439 pub fn noop_fold_usize<T: Folder>(i: usize, _: &mut T) -> usize {
 440     i
 441 }
 442
 443 pub fn noop_fold_path<T: Folder>(Path { segments, span }: Path, fld: &mut T) -> Path {
 444     Path {
 445         segments: segments.move_map(|PathSegment { ident, args }| PathSegment {
 446             ident: fld.fold_ident(ident),
 447             args: args.map(|args| args.map(|args| fld.fold_generic_args(args))),
 448         }),
 449         span: fld.new_span(span)
 450     }
 451 }
 452
 453 pub fn noop_fold_qpath<T: Folder>(qself: Option<QSelf>,
 454                                   path: Path,
 455                                   fld: &mut T) -> (Option<QSelf>, Path) {
 456     let qself = qself.map(|QSelf { ty, path_span, position }| {
 457         QSelf {
 458             ty: fld.fold_ty(ty),
 459             path_span: fld.new_span(path_span),
 460             position,
 461         }
 462     });
 463     (qself, fld.fold_path(path))
 464 }
 465
 466 pub fn noop_fold_generic_args<T: Folder>(generic_args: GenericArgs, fld: &mut T) -> GenericArgs
 467 {
 468     match generic_args {
 469         GenericArgs::AngleBracketed(data) => {
 470             GenericArgs::AngleBracketed(fld.fold_angle_bracketed_parameter_data(data))
 471         }
 472         GenericArgs::Parenthesized(data) => {
 473             GenericArgs::Parenthesized(fld.fold_parenthesized_parameter_data(data))
 474         }
 475     }
 476 }
 477
 478 pub fn noop_fold_angle_bracketed_parameter_data<T: Folder>(data: AngleBracketedArgs,
 479                                                            fld: &mut T)
 480                                                            -> AngleBracketedArgs
 481 {
 482     let AngleBracketedArgs { args, bindings, span } = data;
 483     AngleBracketedArgs {
 484         args: args.move_map(|arg| fld.fold_generic_arg(arg)),
 485         bindings: bindings.move_map(|b| fld.fold_ty_binding(b)),
 486         span: fld.new_span(span)
 487     }
 488 }
 489
 490 pub fn noop_fold_parenthesized_parameter_data<T: Folder>(data: ParenthesisedArgs,
 491                                                          fld: &mut T)
 492                                                          -> ParenthesisedArgs
 493 {
 494     let ParenthesisedArgs { inputs, output, span } = data;
 495     ParenthesisedArgs {
 496         inputs: inputs.move_map(|ty| fld.fold_ty(ty)),
 497         output: output.map(|ty| fld.fold_ty(ty)),
 498         span: fld.new_span(span)
 499     }
 500 }
 501
 502 pub fn noop_fold_local<T: Folder>(l: P<Local>, fld: &mut T) -> P<Local> {
 503     l.map(|Local {id, pat, ty, init, span, attrs}| Local {
 504         id: fld.new_id(id),
 505         pat: fld.fold_pat(pat),
 506         ty: ty.map(|t| fld.fold_ty(t)),
 507         init: init.map(|e| fld.fold_expr(e)),
 508         span: fld.new_span(span),
 509         attrs: fold_attrs(attrs.into(), fld).into(),
 510     })
 511 }
 512
 513 pub fn noop_fold_attribute<T: Folder>(attr: Attribute, fld: &mut T) -> Option<Attribute> {
 514     Some(Attribute {
 515         id: attr.id,
 516         style: attr.style,
 517         path: fld.fold_path(attr.path),
 518         tokens: fld.fold_tts(attr.tokens),
 519         is_sugared_doc: attr.is_sugared_doc,
 520         span: fld.new_span(attr.span),
 521     })
 522 }
 523
 524 pub fn noop_fold_mac<T: Folder>(Spanned {node, span}: Mac, fld: &mut T) -> Mac {
 525     Spanned {
 526         node: Mac_ {
 527             tts: fld.fold_tts(node.stream()).into(),
 528             path: fld.fold_path(node.path),
 529             delim: node.delim,
 530         },
 531         span: fld.new_span(span)
 532     }
 533 }
 534
 535 pub fn noop_fold_macro_def<T: Folder>(def: MacroDef, fld: &mut T) -> MacroDef {
 536     MacroDef {
 537         tokens: fld.fold_tts(def.tokens.into()).into(),
 538         legacy: def.legacy,
 539     }
 540 }
 541
 542 pub fn noop_fold_meta_list_item<T: Folder>(li: NestedMetaItem, fld: &mut T)
 543     -> NestedMetaItem {
 544     Spanned {
 545         node: match li.node {
 546             NestedMetaItemKind::MetaItem(mi) =>  {
 547                 NestedMetaItemKind::MetaItem(fld.fold_meta_item(mi))
 548             },
 549             NestedMetaItemKind::Literal(lit) => NestedMetaItemKind::Literal(lit)
 550         },
 551         span: fld.new_span(li.span)
 552     }
 553 }
 554
 555 pub fn noop_fold_meta_item<T: Folder>(mi: MetaItem, fld: &mut T) -> MetaItem {
 556     MetaItem {
 557         ident: mi.ident,
 558         node: match mi.node {
 559             MetaItemKind::Word => MetaItemKind::Word,
 560             MetaItemKind::List(mis) => {
 561                 MetaItemKind::List(mis.move_map(|e| fld.fold_meta_list_item(e)))
 562             },
 563             MetaItemKind::NameValue(s) => MetaItemKind::NameValue(s),
 564         },
 565         span: fld.new_span(mi.span)
 566     }
 567 }
 568
 569 pub fn noop_fold_arg<T: Folder>(Arg {id, pat, ty}: Arg, fld: &mut T) -> Arg {
 570     Arg {
 571         id: fld.new_id(id),
 572         pat: fld.fold_pat(pat),
 573         ty: fld.fold_ty(ty)
 574     }
 575 }
 576
 577 pub fn noop_fold_tt<T: Folder>(tt: TokenTree, fld: &mut T) -> TokenTree {
 578     match tt {
 579         TokenTree::Token(span, tok) =>
 580             TokenTree::Token(fld.new_span(span), fld.fold_token(tok)),
 581         TokenTree::Delimited(span, delimed) => TokenTree::Delimited(fld.new_span(span), Delimited {
 582             tts: fld.fold_tts(delimed.stream()).into(),
 583             delim: delimed.delim,
 584         }),
 585     }
 586 }
 587
 588 pub fn noop_fold_tts<T: Folder>(tts: TokenStream, fld: &mut T) -> TokenStream {
 589     tts.map(|tt| fld.fold_tt(tt))
 590 }
 591
 592 // apply ident folder if it's an ident, apply other folds to interpolated nodes
 593 pub fn noop_fold_token<T: Folder>(t: token::Token, fld: &mut T) -> token::Token {
 594     match t {
 595         token::Ident(id, is_raw) => token::Ident(fld.fold_ident(id), is_raw),
 596         token::Lifetime(id) => token::Lifetime(fld.fold_ident(id)),
 597         token::Interpolated(nt) => {
 598             let nt = match Lrc::try_unwrap(nt) {
 599                 Ok(nt) => nt,
 600                 Err(nt) => (*nt).clone(),
 601             };
 602             Token::interpolated(fld.fold_interpolated(nt.0))
 603         }
 604         _ => t
 605     }
 606 }
 607
 608 /// apply folder to elements of interpolated nodes
 609 //
 610 // NB: this can occur only when applying a fold to partially expanded code, where
 611 // parsed pieces have gotten implanted ito *other* macro invocations. This is relevant
 612 // for macro hygiene, but possibly not elsewhere.
 613 //
 614 // One problem here occurs because the types for fold_item, fold_stmt, etc. allow the
 615 // folder to return *multiple* items; this is a problem for the nodes here, because
 616 // they insist on having exactly one piece. One solution would be to mangle the fold
 617 // trait to include one-to-many and one-to-one versions of these entry points, but that
 618 // would probably confuse a lot of people and help very few. Instead, I'm just going
 619 // to put in dynamic checks. I think the performance impact of this will be pretty much
 620 // nonexistent. The danger is that someone will apply a fold to a partially expanded
 621 // node, and will be confused by the fact that their "fold_item" or "fold_stmt" isn't
 622 // getting called on NtItem or NtStmt nodes. Hopefully they'll wind up reading this
 623 // comment, and doing something appropriate.
 624 //
 625 // BTW, design choice: I considered just changing the type of, e.g., NtItem to contain
 626 // multiple items, but decided against it when I looked at parse_item_or_view_item and
 627 // tried to figure out what I would do with multiple items there....
 628 pub fn noop_fold_interpolated<T: Folder>(nt: token::Nonterminal, fld: &mut T)
 629                                          -> token::Nonterminal {
 630     match nt {
 631         token::NtItem(item) =>
 632             token::NtItem(fld.fold_item(item)
 633                           // this is probably okay, because the only folds likely
 634                           // to peek inside interpolated nodes will be renamings/markings,
 635                           // which map single items to single items
 636                           .expect_one("expected fold to produce exactly one item")),
 637         token::NtBlock(block) => token::NtBlock(fld.fold_block(block)),
 638         token::NtStmt(stmt) =>
 639             token::NtStmt(fld.fold_stmt(stmt)
 640                           // this is probably okay, because the only folds likely
 641                           // to peek inside interpolated nodes will be renamings/markings,
 642                           // which map single items to single items
 643                           .expect_one("expected fold to produce exactly one statement")),
 644         token::NtPat(pat) => token::NtPat(fld.fold_pat(pat)),
 645         token::NtExpr(expr) => token::NtExpr(fld.fold_expr(expr)),
 646         token::NtTy(ty) => token::NtTy(fld.fold_ty(ty)),
 647         token::NtIdent(ident, is_raw) => token::NtIdent(fld.fold_ident(ident), is_raw),
 648         token::NtLifetime(ident) => token::NtLifetime(fld.fold_ident(ident)),
 649         token::NtLiteral(expr) => token::NtLiteral(fld.fold_expr(expr)),
 650         token::NtMeta(meta) => token::NtMeta(fld.fold_meta_item(meta)),
 651         token::NtPath(path) => token::NtPath(fld.fold_path(path)),
 652         token::NtTT(tt) => token::NtTT(fld.fold_tt(tt)),
 653         token::NtArm(arm) => token::NtArm(fld.fold_arm(arm)),
 654         token::NtImplItem(item) =>
 655             token::NtImplItem(fld.fold_impl_item(item)
 656                               .expect_one("expected fold to produce exactly one item")),
 657         token::NtTraitItem(item) =>
 658             token::NtTraitItem(fld.fold_trait_item(item)
 659                                .expect_one("expected fold to produce exactly one item")),
 660         token::NtGenerics(generics) => token::NtGenerics(fld.fold_generics(generics)),
 661         token::NtWhereClause(where_clause) =>
 662             token::NtWhereClause(fld.fold_where_clause(where_clause)),
 663         token::NtArg(arg) => token::NtArg(fld.fold_arg(arg)),
 664         token::NtVis(vis) => token::NtVis(fld.fold_vis(vis)),
 665         token::NtForeignItem(ni) =>
 666             token::NtForeignItem(fld.fold_foreign_item(ni)
 667                                  // see reasoning above
 668                                  .expect_one("expected fold to produce exactly one item")),
 669     }
 670 }
 671
 672 pub fn noop_fold_fn_decl<T: Folder>(decl: P<FnDecl>, fld: &mut T) -> P<FnDecl> {
 673     decl.map(|FnDecl {inputs, output, variadic}| FnDecl {
 674         inputs: inputs.move_map(|x| fld.fold_arg(x)),
 675         output: match output {
 676             FunctionRetTy::Ty(ty) => FunctionRetTy::Ty(fld.fold_ty(ty)),
 677             FunctionRetTy::Default(span) => FunctionRetTy::Default(fld.new_span(span)),
 678         },
 679         variadic,
 680     })
 681 }
 682
 683 pub fn noop_fold_param_bound<T>(pb: GenericBound, fld: &mut T) -> GenericBound where T: Folder {
 684     match pb {
 685         GenericBound::Trait(ty, modifier) => {
 686             GenericBound::Trait(fld.fold_poly_trait_ref(ty), modifier)
 687         }
 688         GenericBound::Outlives(lifetime) => {
 689             GenericBound::Outlives(noop_fold_lifetime(lifetime, fld))
 690         }
 691     }
 692 }
 693
 694 pub fn noop_fold_generic_param<T: Folder>(param: GenericParam, fld: &mut T) -> GenericParam {
 695     let attrs: Vec<_> = param.attrs.into();
 696     GenericParam {
 697         ident: fld.fold_ident(param.ident),
 698         id: fld.new_id(param.id),
 699         attrs: attrs.into_iter()
 700                     .flat_map(|x| fld.fold_attribute(x).into_iter())
 701                     .collect::<Vec<_>>()
 702                     .into(),
 703         bounds: param.bounds.move_map(|l| noop_fold_param_bound(l, fld)),
 704         kind: match param.kind {
 705             GenericParamKind::Lifetime => GenericParamKind::Lifetime,
 706             GenericParamKind::Type { default } => GenericParamKind::Type {
 707                 default: default.map(|ty| fld.fold_ty(ty))
 708             }
 709         }
 710     }
 711 }
 712
 713 pub fn noop_fold_generic_params<T: Folder>(
 714     params: Vec<GenericParam>,
 715     fld: &mut T
 716 ) -> Vec<GenericParam> {
 717     params.move_map(|p| fld.fold_generic_param(p))
 718 }
 719
 720 pub fn noop_fold_label<T: Folder>(label: Label, fld: &mut T) -> Label {
 721     Label {
 722         ident: fld.fold_ident(label.ident),
 723     }
 724 }
 725
 726 fn noop_fold_lifetime<T: Folder>(l: Lifetime, fld: &mut T) -> Lifetime {
 727     Lifetime {
 728         id: fld.new_id(l.id),
 729         ident: fld.fold_ident(l.ident),
 730     }
 731 }
 732
 733 pub fn noop_fold_generics<T: Folder>(Generics { params, where_clause, span }: Generics,
 734                                      fld: &mut T) -> Generics {
 735     Generics {
 736         params: fld.fold_generic_params(params),
 737         where_clause: fld.fold_where_clause(where_clause),
 738         span: fld.new_span(span),
 739     }
 740 }
 741
 742 pub fn noop_fold_where_clause<T: Folder>(
 743                               WhereClause {id, predicates, span}: WhereClause,
 744                               fld: &mut T)
 745                               -> WhereClause {
 746     WhereClause {
 747         id: fld.new_id(id),
 748         predicates: predicates.move_map(|predicate| {
 749             fld.fold_where_predicate(predicate)
 750         }),
 751         span,
 752     }
 753 }
 754
 755 pub fn noop_fold_where_predicate<T: Folder>(
 756                                  pred: WherePredicate,
 757                                  fld: &mut T)
 758                                  -> WherePredicate {
 759     match pred {
 760         ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate{bound_generic_params,
 761                                                                      bounded_ty,
 762                                                                      bounds,
 763                                                                      span}) => {
 764             ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
 765                 bound_generic_params: fld.fold_generic_params(bound_generic_params),
 766                 bounded_ty: fld.fold_ty(bounded_ty),
 767                 bounds: bounds.move_map(|x| fld.fold_param_bound(x)),
 768                 span: fld.new_span(span)
 769             })
 770         }
 771         ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate{lifetime,
 772                                                                        bounds,
 773                                                                        span}) => {
 774             ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
 775                 span: fld.new_span(span),
 776                 lifetime: noop_fold_lifetime(lifetime, fld),
 777                 bounds: bounds.move_map(|bound| noop_fold_param_bound(bound, fld))
 778             })
 779         }
 780         ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{id,
 781                                                                lhs_ty,
 782                                                                rhs_ty,
 783                                                                span}) => {
 784             ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{
 785                 id: fld.new_id(id),
 786                 lhs_ty: fld.fold_ty(lhs_ty),
 787                 rhs_ty: fld.fold_ty(rhs_ty),
 788                 span: fld.new_span(span)
 789             })
 790         }
 791     }
 792 }
 793
 794 pub fn noop_fold_variant_data<T: Folder>(vdata: VariantData, fld: &mut T) -> VariantData {
 795     match vdata {
 796         ast::VariantData::Struct(fields, id) => {
 797             ast::VariantData::Struct(fields.move_map(|f| fld.fold_struct_field(f)),
 798                                      fld.new_id(id))
 799         }
 800         ast::VariantData::Tuple(fields, id) => {
 801             ast::VariantData::Tuple(fields.move_map(|f| fld.fold_struct_field(f)),
 802                                     fld.new_id(id))
 803         }
 804         ast::VariantData::Unit(id) => ast::VariantData::Unit(fld.new_id(id))
 805     }
 806 }
 807
 808 pub fn noop_fold_trait_ref<T: Folder>(p: TraitRef, fld: &mut T) -> TraitRef {
 809     let id = fld.new_id(p.ref_id);
 810     let TraitRef {
 811         path,
 812         ref_id: _,
 813     } = p;
 814     ast::TraitRef {
 815         path: fld.fold_path(path),
 816         ref_id: id,
 817     }
 818 }
 819
 820 pub fn noop_fold_poly_trait_ref<T: Folder>(p: PolyTraitRef, fld: &mut T) -> PolyTraitRef {
 821     ast::PolyTraitRef {
 822         bound_generic_params: fld.fold_generic_params(p.bound_generic_params),
 823         trait_ref: fld.fold_trait_ref(p.trait_ref),
 824         span: fld.new_span(p.span),
 825     }
 826 }
 827
 828 pub fn noop_fold_struct_field<T: Folder>(f: StructField, fld: &mut T) -> StructField {
 829     StructField {
 830         span: fld.new_span(f.span),
 831         id: fld.new_id(f.id),
 832         ident: f.ident.map(|ident| fld.fold_ident(ident)),
 833         vis: fld.fold_vis(f.vis),
 834         ty: fld.fold_ty(f.ty),
 835         attrs: fold_attrs(f.attrs, fld),
 836     }
 837 }
 838
 839 pub fn noop_fold_field<T: Folder>(f: Field, folder: &mut T) -> Field {
 840     Field {
 841         ident: folder.fold_ident(f.ident),
 842         expr: folder.fold_expr(f.expr),
 843         span: folder.new_span(f.span),
 844         is_shorthand: f.is_shorthand,
 845         attrs: fold_thin_attrs(f.attrs, folder),
 846     }
 847 }
 848
 849 pub fn noop_fold_mt<T: Folder>(MutTy {ty, mutbl}: MutTy, folder: &mut T) -> MutTy {
 850     MutTy {
 851         ty: folder.fold_ty(ty),
 852         mutbl,
 853     }
 854 }
 855
 856 pub fn noop_fold_opt_bounds<T: Folder>(b: Option<GenericBounds>, folder: &mut T)
 857                                        -> Option<GenericBounds> {
 858     b.map(|bounds| folder.fold_bounds(bounds))
 859 }
 860
 861 fn noop_fold_bounds<T: Folder>(bounds: GenericBounds, folder: &mut T)
 862                           -> GenericBounds {
 863     bounds.move_map(|bound| folder.fold_param_bound(bound))
 864 }
 865
 866 pub fn noop_fold_block<T: Folder>(b: P<Block>, folder: &mut T) -> P<Block> {
 867     b.map(|Block {id, stmts, rules, span, recovered}| Block {
 868         id: folder.new_id(id),
 869         stmts: stmts.move_flat_map(|s| folder.fold_stmt(s).into_iter()),
 870         rules,
 871         span: folder.new_span(span),
 872         recovered,
 873     })
 874 }
 875
 876 pub fn noop_fold_item_kind<T: Folder>(i: ItemKind, folder: &mut T) -> ItemKind {
 877     match i {
 878         ItemKind::ExternCrate(orig_name) => ItemKind::ExternCrate(orig_name),
 879         ItemKind::Use(use_tree) => {
 880             ItemKind::Use(use_tree.map(|tree| folder.fold_use_tree(tree)))
 881         }
 882         ItemKind::Static(t, m, e) => {
 883             ItemKind::Static(folder.fold_ty(t), m, folder.fold_expr(e))
 884         }
 885         ItemKind::Const(t, e) => {
 886             ItemKind::Const(folder.fold_ty(t), folder.fold_expr(e))
 887         }
 888         ItemKind::Fn(decl, header, generics, body) => {
 889             let generics = folder.fold_generics(generics);
 890             let header = folder.fold_fn_header(header);
 891             let decl = folder.fold_fn_decl(decl);
 892             let body = folder.fold_block(body);
 893             ItemKind::Fn(decl, header, generics, body)
 894         }
 895         ItemKind::Mod(m) => ItemKind::Mod(folder.fold_mod(m)),
 896         ItemKind::ForeignMod(nm) => ItemKind::ForeignMod(folder.fold_foreign_mod(nm)),
 897         ItemKind::GlobalAsm(ga) => ItemKind::GlobalAsm(folder.fold_global_asm(ga)),
 898         ItemKind::Ty(t, generics) => {
 899             ItemKind::Ty(folder.fold_ty(t), folder.fold_generics(generics))
 900         }
 901         ItemKind::Enum(enum_definition, generics) => {
 902             let generics = folder.fold_generics(generics);
 903             let variants = enum_definition.variants.move_map(|x| folder.fold_variant(x));
 904             ItemKind::Enum(ast::EnumDef { variants: variants }, generics)
 905         }
 906         ItemKind::Struct(struct_def, generics) => {
 907             let generics = folder.fold_generics(generics);
 908             ItemKind::Struct(folder.fold_variant_data(struct_def), generics)
 909         }
 910         ItemKind::Union(struct_def, generics) => {
 911             let generics = folder.fold_generics(generics);
 912             ItemKind::Union(folder.fold_variant_data(struct_def), generics)
 913         }
 914         ItemKind::Impl(unsafety,
 915                        polarity,
 916                        defaultness,
 917                        generics,
 918                        ifce,
 919                        ty,
 920                        impl_items) => ItemKind::Impl(
 921             unsafety,
 922             polarity,
 923             defaultness,
 924             folder.fold_generics(generics),
 925             ifce.map(|trait_ref| folder.fold_trait_ref(trait_ref.clone())),
 926             folder.fold_ty(ty),
 927             impl_items.move_flat_map(|item| folder.fold_impl_item(item)),
 928         ),
 929         ItemKind::Trait(is_auto, unsafety, generics, bounds, items) => ItemKind::Trait(
 930             is_auto,
 931             unsafety,
 932             folder.fold_generics(generics),
 933             folder.fold_bounds(bounds),
 934             items.move_flat_map(|item| folder.fold_trait_item(item)),
 935         ),
 936         ItemKind::TraitAlias(generics, bounds) => ItemKind::TraitAlias(
 937             folder.fold_generics(generics),
 938             folder.fold_bounds(bounds)),
 939         ItemKind::Mac(m) => ItemKind::Mac(folder.fold_mac(m)),
 940         ItemKind::MacroDef(def) => ItemKind::MacroDef(folder.fold_macro_def(def)),
 941     }
 942 }
 943
 944 pub fn noop_fold_trait_item<T: Folder>(i: TraitItem, folder: &mut T)
 945                                        -> SmallVector<TraitItem> {
 946     SmallVector::one(TraitItem {
 947         id: folder.new_id(i.id),
 948         ident: folder.fold_ident(i.ident),
 949         attrs: fold_attrs(i.attrs, folder),
 950         generics: folder.fold_generics(i.generics),
 951         node: match i.node {
 952             TraitItemKind::Const(ty, default) => {
 953                 TraitItemKind::Const(folder.fold_ty(ty),
 954                                default.map(|x| folder.fold_expr(x)))
 955             }
 956             TraitItemKind::Method(sig, body) => {
 957                 TraitItemKind::Method(noop_fold_method_sig(sig, folder),
 958                                 body.map(|x| folder.fold_block(x)))
 959             }
 960             TraitItemKind::Type(bounds, default) => {
 961                 TraitItemKind::Type(folder.fold_bounds(bounds),
 962                               default.map(|x| folder.fold_ty(x)))
 963             }
 964             ast::TraitItemKind::Macro(mac) => {
 965                 TraitItemKind::Macro(folder.fold_mac(mac))
 966             }
 967         },
 968         span: folder.new_span(i.span),
 969         tokens: i.tokens,
 970     })
 971 }
 972
 973 pub fn noop_fold_impl_item<T: Folder>(i: ImplItem, folder: &mut T)
 974                                       -> SmallVector<ImplItem> {
 975     SmallVector::one(ImplItem {
 976         id: folder.new_id(i.id),
 977         vis: folder.fold_vis(i.vis),
 978         ident: folder.fold_ident(i.ident),
 979         attrs: fold_attrs(i.attrs, folder),
 980         generics: folder.fold_generics(i.generics),
 981         defaultness: i.defaultness,
 982         node: match i.node  {
 983             ast::ImplItemKind::Const(ty, expr) => {
 984                 ast::ImplItemKind::Const(folder.fold_ty(ty), folder.fold_expr(expr))
 985             }
 986             ast::ImplItemKind::Method(sig, body) => {
 987                 ast::ImplItemKind::Method(noop_fold_method_sig(sig, folder),
 988                                folder.fold_block(body))
 989             }
 990             ast::ImplItemKind::Type(ty) => ast::ImplItemKind::Type(folder.fold_ty(ty)),
 991             ast::ImplItemKind::Macro(mac) => ast::ImplItemKind::Macro(folder.fold_mac(mac))
 992         },
 993         span: folder.new_span(i.span),
 994         tokens: i.tokens,
 995     })
 996 }
 997
 998 pub fn noop_fold_fn_header<T: Folder>(mut header: FnHeader, folder: &mut T) -> FnHeader {
 999     header.asyncness = match header.asyncness {
1000         IsAsync::Async(node_id) => IsAsync::Async(folder.new_id(node_id)),
1001         IsAsync::NotAsync => IsAsync::NotAsync,
1002     };
1003     header
1004 }
1005
1006 pub fn noop_fold_mod<T: Folder>(Mod {inner, items}: Mod, folder: &mut T) -> Mod {
1007     Mod {
1008         inner: folder.new_span(inner),
1009         items: items.move_flat_map(|x| folder.fold_item(x)),
1010     }
1011 }
1012
1013 pub fn noop_fold_crate<T: Folder>(Crate {module, attrs, span}: Crate,
1014                                   folder: &mut T) -> Crate {
1015     let mut items = folder.fold_item(P(ast::Item {
1016         ident: keywords::Invalid.ident(),
1017         attrs,
1018         id: ast::DUMMY_NODE_ID,
1019         vis: respan(span.shrink_to_lo(), ast::VisibilityKind::Public),
1020         span,
1021         node: ast::ItemKind::Mod(module),
1022         tokens: None,
1023     })).into_iter();
1024
1025     let (module, attrs, span) = match items.next() {
1026         Some(item) => {
1027             assert!(items.next().is_none(),
1028                     "a crate cannot expand to more than one item");
1029             item.and_then(|ast::Item { attrs, span, node, .. }| {
1030                 match node {
1031                     ast::ItemKind::Mod(m) => (m, attrs, span),
1032                     _ => panic!("fold converted a module to not a module"),
1033                 }
1034             })
1035         }
1036         None => (ast::Mod {
1037             inner: span,
1038             items: vec![],
1039         }, vec![], span)
1040     };
1041
1042     Crate {
1043         module,
1044         attrs,
1045         span,
1046     }
1047 }
1048
1049 // fold one item into possibly many items
1050 pub fn noop_fold_item<T: Folder>(i: P<Item>, folder: &mut T) -> SmallVector<P<Item>> {
1051     SmallVector::one(i.map(|i| folder.fold_item_simple(i)))
1052 }
1053
1054 // fold one item into exactly one item
1055 pub fn noop_fold_item_simple<T: Folder>(Item {id, ident, attrs, node, vis, span, tokens}: Item,
1056                                         folder: &mut T) -> Item {
1057     Item {
1058         id: folder.new_id(id),
1059         vis: folder.fold_vis(vis),
1060         ident: folder.fold_ident(ident),
1061         attrs: fold_attrs(attrs, folder),
1062         node: folder.fold_item_kind(node),
1063         span: folder.new_span(span),
1064
1065         // FIXME: if this is replaced with a call to `folder.fold_tts` it causes
1066         //        an ICE during resolve... odd!
1067         tokens,
1068     }
1069 }
1070
1071 pub fn noop_fold_foreign_item<T: Folder>(ni: ForeignItem, folder: &mut T)
1072 -> SmallVector<ForeignItem> {
1073     SmallVector::one(folder.fold_foreign_item_simple(ni))
1074 }
1075
1076 pub fn noop_fold_foreign_item_simple<T: Folder>(ni: ForeignItem, folder: &mut T) -> ForeignItem {
1077     ForeignItem {
1078         id: folder.new_id(ni.id),
1079         vis: folder.fold_vis(ni.vis),
1080         ident: folder.fold_ident(ni.ident),
1081         attrs: fold_attrs(ni.attrs, folder),
1082         node: match ni.node {
1083             ForeignItemKind::Fn(fdec, generics) => {
1084                 ForeignItemKind::Fn(folder.fold_fn_decl(fdec), folder.fold_generics(generics))
1085             }
1086             ForeignItemKind::Static(t, m) => {
1087                 ForeignItemKind::Static(folder.fold_ty(t), m)
1088             }
1089             ForeignItemKind::Ty => ForeignItemKind::Ty,
1090             ForeignItemKind::Macro(mac) => ForeignItemKind::Macro(folder.fold_mac(mac)),
1091         },
1092         span: folder.new_span(ni.span)
1093     }
1094 }
1095
1096 pub fn noop_fold_method_sig<T: Folder>(sig: MethodSig, folder: &mut T) -> MethodSig {
1097     MethodSig {
1098         header: folder.fold_fn_header(sig.header),
1099         decl: folder.fold_fn_decl(sig.decl)
1100     }
1101 }
1102
1103 pub fn noop_fold_pat<T: Folder>(p: P<Pat>, folder: &mut T) -> P<Pat> {
1104     p.map(|Pat {id, node, span}| Pat {
1105         id: folder.new_id(id),
1106         node: match node {
1107             PatKind::Wild => PatKind::Wild,
1108             PatKind::Ident(binding_mode, ident, sub) => {
1109                 PatKind::Ident(binding_mode,
1110                                folder.fold_ident(ident),
1111                                sub.map(|x| folder.fold_pat(x)))
1112             }
1113             PatKind::Lit(e) => PatKind::Lit(folder.fold_expr(e)),
1114             PatKind::TupleStruct(pth, pats, ddpos) => {
1115                 PatKind::TupleStruct(folder.fold_path(pth),
1116                         pats.move_map(|x| folder.fold_pat(x)), ddpos)
1117             }
1118             PatKind::Path(qself, pth) => {
1119                 let (qself, pth) = folder.fold_qpath(qself, pth);
1120                 PatKind::Path(qself, pth)
1121             }
1122             PatKind::Struct(pth, fields, etc) => {
1123                 let pth = folder.fold_path(pth);
1124                 let fs = fields.move_map(|f| {
1125                     Spanned { span: folder.new_span(f.span),
1126                               node: ast::FieldPat {
1127                                   ident: folder.fold_ident(f.node.ident),
1128                                   pat: folder.fold_pat(f.node.pat),
1129                                   is_shorthand: f.node.is_shorthand,
1130                                   attrs: fold_attrs(f.node.attrs.into(), folder).into()
1131                               }}
1132                 });
1133                 PatKind::Struct(pth, fs, etc)
1134             }
1135             PatKind::Tuple(elts, ddpos) => {
1136                 PatKind::Tuple(elts.move_map(|x| folder.fold_pat(x)), ddpos)
1137             }
1138             PatKind::Box(inner) => PatKind::Box(folder.fold_pat(inner)),
1139             PatKind::Ref(inner, mutbl) => PatKind::Ref(folder.fold_pat(inner), mutbl),
1140             PatKind::Range(e1, e2, end) => {
1141                 PatKind::Range(folder.fold_expr(e1),
1142                                folder.fold_expr(e2),
1143                                folder.fold_range_end(end))
1144             },
1145             PatKind::Slice(before, slice, after) => {
1146                 PatKind::Slice(before.move_map(|x| folder.fold_pat(x)),
1147                        slice.map(|x| folder.fold_pat(x)),
1148                        after.move_map(|x| folder.fold_pat(x)))
1149             }
1150             PatKind::Paren(inner) => PatKind::Paren(folder.fold_pat(inner)),
1151             PatKind::Mac(mac) => PatKind::Mac(folder.fold_mac(mac))
1152         },
1153         span: folder.new_span(span)
1154     })
1155 }
1156
1157 pub fn noop_fold_range_end<T: Folder>(end: RangeEnd, _folder: &mut T) -> RangeEnd {
1158     end
1159 }
1160
1161 pub fn noop_fold_anon_const<T: Folder>(constant: AnonConst, folder: &mut T) -> AnonConst {
1162     let AnonConst {id, value} = constant;
1163     AnonConst {
1164         id: folder.new_id(id),
1165         value: folder.fold_expr(value),
1166     }
1167 }
1168
1169 pub fn noop_fold_expr<T: Folder>(Expr {id, node, span, attrs}: Expr, folder: &mut T) -> Expr {
1170     Expr {
1171         node: match node {
1172             ExprKind::Box(e) => {
1173                 ExprKind::Box(folder.fold_expr(e))
1174             }
1175             ExprKind::ObsoleteInPlace(a, b) => {
1176                 ExprKind::ObsoleteInPlace(folder.fold_expr(a), folder.fold_expr(b))
1177             }
1178             ExprKind::Array(exprs) => {
1179                 ExprKind::Array(folder.fold_exprs(exprs))
1180             }
1181             ExprKind::Repeat(expr, count) => {
1182                 ExprKind::Repeat(folder.fold_expr(expr), folder.fold_anon_const(count))
1183             }
1184             ExprKind::Tup(exprs) => ExprKind::Tup(folder.fold_exprs(exprs)),
1185             ExprKind::Call(f, args) => {
1186                 ExprKind::Call(folder.fold_expr(f),
1187                          folder.fold_exprs(args))
1188             }
1189             ExprKind::MethodCall(seg, args) => {
1190                 ExprKind::MethodCall(
1191                     PathSegment {
1192                         ident: folder.fold_ident(seg.ident),
1193                         args: seg.args.map(|args| {
1194                             args.map(|args| folder.fold_generic_args(args))
1195                         }),
1196                     },
1197                     folder.fold_exprs(args))
1198             }
1199             ExprKind::Binary(binop, lhs, rhs) => {
1200                 ExprKind::Binary(binop,
1201                         folder.fold_expr(lhs),
1202                         folder.fold_expr(rhs))
1203             }
1204             ExprKind::Unary(binop, ohs) => {
1205                 ExprKind::Unary(binop, folder.fold_expr(ohs))
1206             }
1207             ExprKind::Lit(l) => ExprKind::Lit(l),
1208             ExprKind::Cast(expr, ty) => {
1209                 ExprKind::Cast(folder.fold_expr(expr), folder.fold_ty(ty))
1210             }
1211             ExprKind::Type(expr, ty) => {
1212                 ExprKind::Type(folder.fold_expr(expr), folder.fold_ty(ty))
1213             }
1214             ExprKind::AddrOf(m, ohs) => ExprKind::AddrOf(m, folder.fold_expr(ohs)),
1215             ExprKind::If(cond, tr, fl) => {
1216                 ExprKind::If(folder.fold_expr(cond),
1217                        folder.fold_block(tr),
1218                        fl.map(|x| folder.fold_expr(x)))
1219             }
1220             ExprKind::IfLet(pats, expr, tr, fl) => {
1221                 ExprKind::IfLet(pats.move_map(|pat| folder.fold_pat(pat)),
1222                           folder.fold_expr(expr),
1223                           folder.fold_block(tr),
1224                           fl.map(|x| folder.fold_expr(x)))
1225             }
1226             ExprKind::While(cond, body, opt_label) => {
1227                 ExprKind::While(folder.fold_expr(cond),
1228                           folder.fold_block(body),
1229                           opt_label.map(|label| folder.fold_label(label)))
1230             }
1231             ExprKind::WhileLet(pats, expr, body, opt_label) => {
1232                 ExprKind::WhileLet(pats.move_map(|pat| folder.fold_pat(pat)),
1233                              folder.fold_expr(expr),
1234                              folder.fold_block(body),
1235                              opt_label.map(|label| folder.fold_label(label)))
1236             }
1237             ExprKind::ForLoop(pat, iter, body, opt_label) => {
1238                 ExprKind::ForLoop(folder.fold_pat(pat),
1239                             folder.fold_expr(iter),
1240                             folder.fold_block(body),
1241                             opt_label.map(|label| folder.fold_label(label)))
1242             }
1243             ExprKind::Loop(body, opt_label) => {
1244                 ExprKind::Loop(folder.fold_block(body),
1245                                opt_label.map(|label| folder.fold_label(label)))
1246             }
1247             ExprKind::Match(expr, arms) => {
1248                 ExprKind::Match(folder.fold_expr(expr),
1249                           arms.move_map(|x| folder.fold_arm(x)))
1250             }
1251             ExprKind::Closure(capture_clause, asyncness, movability, decl, body, span) => {
1252                 let asyncness = match asyncness {
1253                     IsAsync::Async(node_id) => IsAsync::Async(folder.new_id(node_id)),
1254                     IsAsync::NotAsync => IsAsync::NotAsync,
1255                 };
1256                 ExprKind::Closure(capture_clause,
1257                                   asyncness,
1258                                   movability,
1259                                   folder.fold_fn_decl(decl),
1260                                   folder.fold_expr(body),
1261                                   folder.new_span(span))
1262             }
1263             ExprKind::Block(blk, opt_label) => {
1264                 ExprKind::Block(folder.fold_block(blk),
1265                                 opt_label.map(|label| folder.fold_label(label)))
1266             }
1267             ExprKind::Async(capture_clause, node_id, body) => {
1268                 ExprKind::Async(capture_clause, folder.new_id(node_id), folder.fold_block(body))
1269             }
1270             ExprKind::Assign(el, er) => {
1271                 ExprKind::Assign(folder.fold_expr(el), folder.fold_expr(er))
1272             }
1273             ExprKind::AssignOp(op, el, er) => {
1274                 ExprKind::AssignOp(op,
1275                             folder.fold_expr(el),
1276                             folder.fold_expr(er))
1277             }
1278             ExprKind::Field(el, ident) => {
1279                 ExprKind::Field(folder.fold_expr(el), folder.fold_ident(ident))
1280             }
1281             ExprKind::Index(el, er) => {
1282                 ExprKind::Index(folder.fold_expr(el), folder.fold_expr(er))
1283             }
1284             ExprKind::Range(e1, e2, lim) => {
1285                 ExprKind::Range(e1.map(|x| folder.fold_expr(x)),
1286                                 e2.map(|x| folder.fold_expr(x)),
1287                                 lim)
1288             }
1289             ExprKind::Path(qself, path) => {
1290                 let (qself, path) = folder.fold_qpath(qself, path);
1291                 ExprKind::Path(qself, path)
1292             }
1293             ExprKind::Break(opt_label, opt_expr) => {
1294                 ExprKind::Break(opt_label.map(|label| folder.fold_label(label)),
1295                                 opt_expr.map(|e| folder.fold_expr(e)))
1296             }
1297             ExprKind::Continue(opt_label) => {
1298                 ExprKind::Continue(opt_label.map(|label| folder.fold_label(label)))
1299             }
1300             ExprKind::Ret(e) => ExprKind::Ret(e.map(|x| folder.fold_expr(x))),
1301             ExprKind::InlineAsm(asm) => ExprKind::InlineAsm(asm.map(|asm| {
1302                 InlineAsm {
1303                     inputs: asm.inputs.move_map(|(c, input)| {
1304                         (c, folder.fold_expr(input))
1305                     }),
1306                     outputs: asm.outputs.move_map(|out| {
1307                         InlineAsmOutput {
1308                             constraint: out.constraint,
1309                             expr: folder.fold_expr(out.expr),
1310                             is_rw: out.is_rw,
1311                             is_indirect: out.is_indirect,
1312                         }
1313                     }),
1314                     ..asm
1315                 }
1316             })),
1317             ExprKind::Mac(mac) => ExprKind::Mac(folder.fold_mac(mac)),
1318             ExprKind::Struct(path, fields, maybe_expr) => {
1319                 ExprKind::Struct(folder.fold_path(path),
1320                         fields.move_map(|x| folder.fold_field(x)),
1321                         maybe_expr.map(|x| folder.fold_expr(x)))
1322             },
1323             ExprKind::Paren(ex) => {
1324                 let sub_expr = folder.fold_expr(ex);
1325                 return Expr {
1326                     // Nodes that are equal modulo `Paren` sugar no-ops should have the same ids.
1327                     id: sub_expr.id,
1328                     node: ExprKind::Paren(sub_expr),
1329                     span: folder.new_span(span),
1330                     attrs: fold_attrs(attrs.into(), folder).into(),
1331                 };
1332             }
1333             ExprKind::Yield(ex) => ExprKind::Yield(ex.map(|x| folder.fold_expr(x))),
1334             ExprKind::Try(ex) => ExprKind::Try(folder.fold_expr(ex)),
1335             ExprKind::Catch(body) => ExprKind::Catch(folder.fold_block(body)),
1336         },
1337         id: folder.new_id(id),
1338         span: folder.new_span(span),
1339         attrs: fold_attrs(attrs.into(), folder).into(),
1340     }
1341 }
1342
1343 pub fn noop_fold_opt_expr<T: Folder>(e: P<Expr>, folder: &mut T) -> Option<P<Expr>> {
1344     Some(folder.fold_expr(e))
1345 }
1346
1347 pub fn noop_fold_exprs<T: Folder>(es: Vec<P<Expr>>, folder: &mut T) -> Vec<P<Expr>> {
1348     es.move_flat_map(|e| folder.fold_opt_expr(e))
1349 }
1350
1351 pub fn noop_fold_stmt<T: Folder>(Stmt {node, span, id}: Stmt, folder: &mut T) -> SmallVector<Stmt> {
1352     let id = folder.new_id(id);
1353     let span = folder.new_span(span);
1354     noop_fold_stmt_kind(node, folder).into_iter().map(|node| {
1355         Stmt { id: id, node: node, span: span }
1356     }).collect()
1357 }
1358
1359 pub fn noop_fold_stmt_kind<T: Folder>(node: StmtKind, folder: &mut T) -> SmallVector<StmtKind> {
1360     match node {
1361         StmtKind::Local(local) => SmallVector::one(StmtKind::Local(folder.fold_local(local))),
1362         StmtKind::Item(item) => folder.fold_item(item).into_iter().map(StmtKind::Item).collect(),
1363         StmtKind::Expr(expr) => {
1364             folder.fold_opt_expr(expr).into_iter().map(StmtKind::Expr).collect()
1365         }
1366         StmtKind::Semi(expr) => {
1367             folder.fold_opt_expr(expr).into_iter().map(StmtKind::Semi).collect()
1368         }
1369         StmtKind::Mac(mac) => SmallVector::one(StmtKind::Mac(mac.map(|(mac, semi, attrs)| {
1370             (folder.fold_mac(mac), semi, fold_attrs(attrs.into(), folder).into())
1371         }))),
1372     }
1373 }
1374
1375 pub fn noop_fold_vis<T: Folder>(vis: Visibility, folder: &mut T) -> Visibility {
1376     match vis.node {
1377         VisibilityKind::Restricted { path, id } => {
1378             respan(vis.span, VisibilityKind::Restricted {
1379                 path: path.map(|path| folder.fold_path(path)),
1380                 id: folder.new_id(id),
1381             })
1382         }
1383         _ => vis,
1384     }
1385 }
1386
1387 #[cfg(test)]
1388 mod tests {
1389     use std::io;
1390     use ast::{self, Ident};
1391     use util::parser_testing::{string_to_crate, matches_codepattern};
1392     use print::pprust;
1393     use fold;
1394     use with_globals;
1395     use super::*;
1396
1397     // this version doesn't care about getting comments or docstrings in.
1398     fn fake_print_crate(s: &mut pprust::State,
1399                         krate: &ast::Crate) -> io::Result<()> {
1400         s.print_mod(&krate.module, &krate.attrs)
1401     }
1402
1403     // change every identifier to "zz"
1404     struct ToZzIdentFolder;
1405
1406     impl Folder for ToZzIdentFolder {
1407         fn fold_ident(&mut self, _: ast::Ident) -> ast::Ident {
1408             Ident::from_str("zz")
1409         }
1410         fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
1411             fold::noop_fold_mac(mac, self)
1412         }
1413     }
1414
1415     // maybe add to expand.rs...
1416     macro_rules! assert_pred {
1417         ($pred:expr, $predname:expr, $a:expr , $b:expr) => (
1418             {
1419                 let pred_val = $pred;
1420                 let a_val = $a;
1421                 let b_val = $b;
1422                 if !(pred_val(&a_val, &b_val)) {
1423                     panic!("expected args satisfying {}, got {} and {}",
1424                           $predname, a_val, b_val);
1425                 }
1426             }
1427         )
1428     }
1429
1430     // make sure idents get transformed everywhere
1431     #[test] fn ident_transformation () {
1432         with_globals(|| {
1433             let mut zz_fold = ToZzIdentFolder;
1434             let ast = string_to_crate(
1435                 "#[a] mod b {fn c (d : e, f : g) {h!(i,j,k);l;m}}".to_string());
1436             let folded_crate = zz_fold.fold_crate(ast);
1437             assert_pred!(
1438                 matches_codepattern,
1439                 "matches_codepattern",
1440                 pprust::to_string(|s| fake_print_crate(s, &folded_crate)),
1441                 "#[zz]mod zz{fn zz(zz:zz,zz:zz){zz!(zz,zz,zz);zz;zz}}".to_string());
1442         })
1443     }
1444
1445     // even inside macro defs....
1446     #[test] fn ident_transformation_in_defs () {
1447         with_globals(|| {
1448             let mut zz_fold = ToZzIdentFolder;
1449             let ast = string_to_crate(
1450                 "macro_rules! a {(b $c:expr $(d $e:token)f+ => \
1451                 (g $(d $d $e)+))} ".to_string());
1452             let folded_crate = zz_fold.fold_crate(ast);
1453             assert_pred!(
1454                 matches_codepattern,
1455                 "matches_codepattern",
1456                 pprust::to_string(|s| fake_print_crate(s, &folded_crate)),
1457                 "macro_rules! zz((zz$zz:zz$(zz $zz:zz)zz+=>(zz$(zz$zz$zz)+)));".to_string());
1458         })
1459     }
1460 }