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 source_map::{Spanned, respan};
  25 use parse::token::{self, Token};
  26 use ptr::P;
  27 use smallvec::{Array, SmallVec};
  28 use symbol::keywords;
  29 use ThinVec;
  30 use tokenstream::*;
  31 use util::move_map::MoveMap;
  32
  33 use rustc_data_structures::sync::Lrc;
  34
  35 pub trait ExpectOne<A: Array> {
  36     fn expect_one(self, err: &'static str) -> A::Item;
  37 }
  38
  39 impl<A: Array> ExpectOne<A> for SmallVec<A> {
  40     fn expect_one(self, err: &'static str) -> A::Item {
  41         assert!(self.len() == 1, err);
  42         self.into_iter().next().unwrap()
  43     }
  44 }
  45
  46 pub trait Folder : Sized {
  47     // Any additions to this trait should happen in form
  48     // of a call to a public `noop_*` function that only calls
  49     // out to the folder again, not other `noop_*` functions.
  50     //
  51     // This is a necessary API workaround to the problem of not
  52     // being able to call out to the super default method
  53     // in an overridden default method.
  54
  55     fn fold_crate(&mut self, c: Crate) -> Crate {
  56         noop_fold_crate(c, self)
  57     }
  58
  59     fn fold_meta_items(&mut self, meta_items: Vec<MetaItem>) -> Vec<MetaItem> {
  60         noop_fold_meta_items(meta_items, self)
  61     }
  62
  63     fn fold_meta_list_item(&mut self, list_item: NestedMetaItem) -> NestedMetaItem {
  64         noop_fold_meta_list_item(list_item, self)
  65     }
  66
  67     fn fold_meta_item(&mut self, meta_item: MetaItem) -> MetaItem {
  68         noop_fold_meta_item(meta_item, self)
  69     }
  70
  71     fn fold_use_tree(&mut self, use_tree: UseTree) -> UseTree {
  72         noop_fold_use_tree(use_tree, self)
  73     }
  74
  75     fn fold_foreign_item(&mut self, ni: ForeignItem) -> SmallVec<[ForeignItem; 1]> {
  76         noop_fold_foreign_item(ni, self)
  77     }
  78
  79     fn fold_foreign_item_simple(&mut self, ni: ForeignItem) -> ForeignItem {
  80         noop_fold_foreign_item_simple(ni, self)
  81     }
  82
  83     fn fold_item(&mut self, i: P<Item>) -> SmallVec<[P<Item>; 1]> {
  84         noop_fold_item(i, self)
  85     }
  86
  87     fn fold_item_simple(&mut self, i: Item) -> Item {
  88         noop_fold_item_simple(i, self)
  89     }
  90
  91     fn fold_fn_header(&mut self, header: FnHeader) -> FnHeader {
  92         noop_fold_fn_header(header, self)
  93     }
  94
  95     fn fold_struct_field(&mut self, sf: StructField) -> StructField {
  96         noop_fold_struct_field(sf, self)
  97     }
  98
  99     fn fold_item_kind(&mut self, i: ItemKind) -> ItemKind {
 100         noop_fold_item_kind(i, self)
 101     }
 102
 103     fn fold_trait_item(&mut self, i: TraitItem) -> SmallVec<[TraitItem; 1]> {
 104         noop_fold_trait_item(i, self)
 105     }
 106
 107     fn fold_impl_item(&mut self, i: ImplItem) -> SmallVec<[ImplItem; 1]> {
 108         noop_fold_impl_item(i, self)
 109     }
 110
 111     fn fold_fn_decl(&mut self, d: P<FnDecl>) -> P<FnDecl> {
 112         noop_fold_fn_decl(d, self)
 113     }
 114
 115     fn fold_asyncness(&mut self, a: IsAsync) -> IsAsync {
 116         noop_fold_asyncness(a, self)
 117     }
 118
 119     fn fold_block(&mut self, b: P<Block>) -> P<Block> {
 120         noop_fold_block(b, self)
 121     }
 122
 123     fn fold_stmt(&mut self, s: Stmt) -> SmallVec<[Stmt; 1]> {
 124         noop_fold_stmt(s, self)
 125     }
 126
 127     fn fold_arm(&mut self, a: Arm) -> Arm {
 128         noop_fold_arm(a, self)
 129     }
 130
 131     fn fold_guard(&mut self, g: Guard) -> Guard {
 132         noop_fold_guard(g, self)
 133     }
 134
 135     fn fold_pat(&mut self, p: P<Pat>) -> P<Pat> {
 136         noop_fold_pat(p, self)
 137     }
 138
 139     fn fold_anon_const(&mut self, c: AnonConst) -> AnonConst {
 140         noop_fold_anon_const(c, self)
 141     }
 142
 143     fn fold_expr(&mut self, e: P<Expr>) -> P<Expr> {
 144         e.map(|e| noop_fold_expr(e, self))
 145     }
 146
 147     fn fold_range_end(&mut self, re: RangeEnd) -> RangeEnd {
 148         noop_fold_range_end(re, self)
 149     }
 150
 151     fn fold_opt_expr(&mut self, e: P<Expr>) -> Option<P<Expr>> {
 152         noop_fold_opt_expr(e, self)
 153     }
 154
 155     fn fold_exprs(&mut self, es: Vec<P<Expr>>) -> Vec<P<Expr>> {
 156         noop_fold_exprs(es, self)
 157     }
 158
 159     fn fold_generic_arg(&mut self, arg: GenericArg) -> GenericArg {
 160         match arg {
 161             GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.fold_lifetime(lt)),
 162             GenericArg::Type(ty) => GenericArg::Type(self.fold_ty(ty)),
 163         }
 164     }
 165
 166     fn fold_ty(&mut self, t: P<Ty>) -> P<Ty> {
 167         noop_fold_ty(t, self)
 168     }
 169
 170     fn fold_lifetime(&mut self, l: Lifetime) -> Lifetime {
 171         noop_fold_lifetime(l, self)
 172     }
 173
 174     fn fold_ty_binding(&mut self, t: TypeBinding) -> TypeBinding {
 175         noop_fold_ty_binding(t, self)
 176     }
 177
 178     fn fold_mod(&mut self, m: Mod) -> Mod {
 179         noop_fold_mod(m, self)
 180     }
 181
 182     fn fold_foreign_mod(&mut self, nm: ForeignMod) -> ForeignMod {
 183         noop_fold_foreign_mod(nm, self)
 184     }
 185
 186     fn fold_global_asm(&mut self, ga: P<GlobalAsm>) -> P<GlobalAsm> {
 187         noop_fold_global_asm(ga, self)
 188     }
 189
 190     fn fold_variant(&mut self, v: Variant) -> Variant {
 191         noop_fold_variant(v, self)
 192     }
 193
 194     fn fold_ident(&mut self, i: Ident) -> Ident {
 195         noop_fold_ident(i, self)
 196     }
 197
 198     fn fold_usize(&mut self, i: usize) -> usize {
 199         noop_fold_usize(i, self)
 200     }
 201
 202     fn fold_path(&mut self, p: Path) -> Path {
 203         noop_fold_path(p, self)
 204     }
 205
 206     fn fold_qpath(&mut self, qs: Option<QSelf>, p: Path) -> (Option<QSelf>, Path) {
 207         noop_fold_qpath(qs, p, self)
 208     }
 209
 210     fn fold_generic_args(&mut self, p: GenericArgs) -> GenericArgs {
 211         noop_fold_generic_args(p, self)
 212     }
 213
 214     fn fold_angle_bracketed_parameter_data(&mut self, p: AngleBracketedArgs)
 215                                            -> AngleBracketedArgs
 216     {
 217         noop_fold_angle_bracketed_parameter_data(p, self)
 218     }
 219
 220     fn fold_parenthesized_parameter_data(&mut self, p: ParenthesisedArgs)
 221                                          -> ParenthesisedArgs
 222     {
 223         noop_fold_parenthesized_parameter_data(p, self)
 224     }
 225
 226     fn fold_local(&mut self, l: P<Local>) -> P<Local> {
 227         noop_fold_local(l, self)
 228     }
 229
 230     fn fold_mac(&mut self, _mac: Mac) -> Mac {
 231         panic!("fold_mac disabled by default");
 232         // N.B., see note about macros above.
 233         // if you really want a folder that
 234         // works on macros, use this
 235         // definition in your trait impl:
 236         // fold::noop_fold_mac(_mac, self)
 237     }
 238
 239     fn fold_macro_def(&mut self, def: MacroDef) -> MacroDef {
 240         noop_fold_macro_def(def, self)
 241     }
 242
 243     fn fold_label(&mut self, label: Label) -> Label {
 244         noop_fold_label(label, self)
 245     }
 246
 247     fn fold_attribute(&mut self, at: Attribute) -> Option<Attribute> {
 248         noop_fold_attribute(at, self)
 249     }
 250
 251     fn fold_arg(&mut self, a: Arg) -> Arg {
 252         noop_fold_arg(a, self)
 253     }
 254
 255     fn fold_generics(&mut self, generics: Generics) -> Generics {
 256         noop_fold_generics(generics, self)
 257     }
 258
 259     fn fold_trait_ref(&mut self, p: TraitRef) -> TraitRef {
 260         noop_fold_trait_ref(p, self)
 261     }
 262
 263     fn fold_poly_trait_ref(&mut self, p: PolyTraitRef) -> PolyTraitRef {
 264         noop_fold_poly_trait_ref(p, self)
 265     }
 266
 267     fn fold_variant_data(&mut self, vdata: VariantData) -> VariantData {
 268         noop_fold_variant_data(vdata, self)
 269     }
 270
 271     fn fold_generic_param(&mut self, param: GenericParam) -> GenericParam {
 272         noop_fold_generic_param(param, self)
 273     }
 274
 275     fn fold_generic_params(&mut self, params: Vec<GenericParam>) -> Vec<GenericParam> {
 276         noop_fold_generic_params(params, self)
 277     }
 278
 279     fn fold_tt(&mut self, tt: TokenTree) -> TokenTree {
 280         noop_fold_tt(tt, self)
 281     }
 282
 283     fn fold_tts(&mut self, tts: TokenStream) -> TokenStream {
 284         noop_fold_tts(tts, self)
 285     }
 286
 287     fn fold_token(&mut self, t: token::Token) -> token::Token {
 288         noop_fold_token(t, self)
 289     }
 290
 291     fn fold_interpolated(&mut self, nt: token::Nonterminal) -> token::Nonterminal {
 292         noop_fold_interpolated(nt, self)
 293     }
 294
 295     fn fold_opt_bounds(&mut self, b: Option<GenericBounds>) -> Option<GenericBounds> {
 296         noop_fold_opt_bounds(b, self)
 297     }
 298
 299     fn fold_bounds(&mut self, b: GenericBounds) -> GenericBounds {
 300         noop_fold_bounds(b, self)
 301     }
 302
 303     fn fold_param_bound(&mut self, tpb: GenericBound) -> GenericBound {
 304         noop_fold_param_bound(tpb, self)
 305     }
 306
 307     fn fold_mt(&mut self, mt: MutTy) -> MutTy {
 308         noop_fold_mt(mt, self)
 309     }
 310
 311     fn fold_field(&mut self, field: Field) -> Field {
 312         noop_fold_field(field, self)
 313     }
 314
 315     fn fold_where_clause(&mut self, where_clause: WhereClause)
 316                          -> WhereClause {
 317         noop_fold_where_clause(where_clause, self)
 318     }
 319
 320     fn fold_where_predicate(&mut self, where_predicate: WherePredicate)
 321                             -> WherePredicate {
 322         noop_fold_where_predicate(where_predicate, self)
 323     }
 324
 325     fn fold_vis(&mut self, vis: Visibility) -> Visibility {
 326         noop_fold_vis(vis, self)
 327     }
 328
 329     fn new_id(&mut self, i: NodeId) -> NodeId {
 330         i
 331     }
 332
 333     fn new_span(&mut self, sp: Span) -> Span {
 334         sp
 335     }
 336 }
 337
 338 pub fn noop_fold_meta_items<T: Folder>(meta_items: Vec<MetaItem>, fld: &mut T) -> Vec<MetaItem> {
 339     meta_items.move_map(|x| fld.fold_meta_item(x))
 340 }
 341
 342 pub fn noop_fold_use_tree<T: Folder>(use_tree: UseTree, fld: &mut T) -> UseTree {
 343     UseTree {
 344         span: fld.new_span(use_tree.span),
 345         prefix: fld.fold_path(use_tree.prefix),
 346         kind: match use_tree.kind {
 347             UseTreeKind::Simple(rename, id1, id2) =>
 348                 UseTreeKind::Simple(rename.map(|ident| fld.fold_ident(ident)),
 349                                     fld.new_id(id1), fld.new_id(id2)),
 350             UseTreeKind::Glob => UseTreeKind::Glob,
 351             UseTreeKind::Nested(items) => UseTreeKind::Nested(items.move_map(|(tree, id)| {
 352                 (fld.fold_use_tree(tree), fld.new_id(id))
 353             })),
 354         },
 355     }
 356 }
 357
 358 pub fn fold_attrs<T: Folder>(attrs: Vec<Attribute>, fld: &mut T) -> Vec<Attribute> {
 359     attrs.move_flat_map(|x| fld.fold_attribute(x))
 360 }
 361
 362 pub fn fold_thin_attrs<T: Folder>(attrs: ThinVec<Attribute>, fld: &mut T) -> ThinVec<Attribute> {
 363     fold_attrs(attrs.into(), fld).into()
 364 }
 365
 366 pub fn noop_fold_arm<T: Folder>(Arm {attrs, pats, guard, body}: Arm,
 367     fld: &mut T) -> Arm {
 368     Arm {
 369         attrs: fold_attrs(attrs, fld),
 370         pats: pats.move_map(|x| fld.fold_pat(x)),
 371         guard: guard.map(|x| fld.fold_guard(x)),
 372         body: fld.fold_expr(body),
 373     }
 374 }
 375
 376 pub fn noop_fold_guard<T: Folder>(g: Guard, fld: &mut T) -> Guard {
 377     match g {
 378         Guard::If(e) => Guard::If(fld.fold_expr(e)),
 379     }
 380 }
 381
 382 pub fn noop_fold_ty_binding<T: Folder>(b: TypeBinding, fld: &mut T) -> TypeBinding {
 383     TypeBinding {
 384         id: fld.new_id(b.id),
 385         ident: fld.fold_ident(b.ident),
 386         ty: fld.fold_ty(b.ty),
 387         span: fld.new_span(b.span),
 388     }
 389 }
 390
 391 pub fn noop_fold_ty<T: Folder>(t: P<Ty>, fld: &mut T) -> P<Ty> {
 392     t.map(|Ty {id, node, span}| Ty {
 393         id: fld.new_id(id),
 394         node: match node {
 395             TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err => node,
 396             TyKind::Slice(ty) => TyKind::Slice(fld.fold_ty(ty)),
 397             TyKind::Ptr(mt) => TyKind::Ptr(fld.fold_mt(mt)),
 398             TyKind::Rptr(region, mt) => {
 399                 TyKind::Rptr(region.map(|lt| noop_fold_lifetime(lt, fld)), fld.fold_mt(mt))
 400             }
 401             TyKind::BareFn(f) => {
 402                 TyKind::BareFn(f.map(|BareFnTy {generic_params, unsafety, abi, decl}| BareFnTy {
 403                     generic_params: fld.fold_generic_params(generic_params),
 404                     unsafety,
 405                     abi,
 406                     decl: fld.fold_fn_decl(decl)
 407                 }))
 408             }
 409             TyKind::Never => node,
 410             TyKind::Tup(tys) => TyKind::Tup(tys.move_map(|ty| fld.fold_ty(ty))),
 411             TyKind::Paren(ty) => TyKind::Paren(fld.fold_ty(ty)),
 412             TyKind::Path(qself, path) => {
 413                 let (qself, path) = fld.fold_qpath(qself, path);
 414                 TyKind::Path(qself, path)
 415             }
 416             TyKind::Array(ty, length) => {
 417                 TyKind::Array(fld.fold_ty(ty), fld.fold_anon_const(length))
 418             }
 419             TyKind::Typeof(expr) => {
 420                 TyKind::Typeof(fld.fold_anon_const(expr))
 421             }
 422             TyKind::TraitObject(bounds, syntax) => {
 423                 TyKind::TraitObject(bounds.move_map(|b| fld.fold_param_bound(b)), syntax)
 424             }
 425             TyKind::ImplTrait(id, bounds) => {
 426                 TyKind::ImplTrait(fld.new_id(id), bounds.move_map(|b| fld.fold_param_bound(b)))
 427             }
 428             TyKind::Mac(mac) => {
 429                 TyKind::Mac(fld.fold_mac(mac))
 430             }
 431         },
 432         span: fld.new_span(span)
 433     })
 434 }
 435
 436 pub fn noop_fold_foreign_mod<T: Folder>(ForeignMod {abi, items}: ForeignMod,
 437                                         fld: &mut T) -> ForeignMod {
 438     ForeignMod {
 439         abi,
 440         items: items.move_flat_map(|x| fld.fold_foreign_item(x)),
 441     }
 442 }
 443
 444 pub fn noop_fold_global_asm<T: Folder>(ga: P<GlobalAsm>,
 445                                        _: &mut T) -> P<GlobalAsm> {
 446     ga
 447 }
 448
 449 pub fn noop_fold_variant<T: Folder>(v: Variant, fld: &mut T) -> Variant {
 450     Spanned {
 451         node: Variant_ {
 452             ident: fld.fold_ident(v.node.ident),
 453             attrs: fold_attrs(v.node.attrs, fld),
 454             data: fld.fold_variant_data(v.node.data),
 455             disr_expr: v.node.disr_expr.map(|e| fld.fold_anon_const(e)),
 456         },
 457         span: fld.new_span(v.span),
 458     }
 459 }
 460
 461 pub fn noop_fold_ident<T: Folder>(ident: Ident, fld: &mut T) -> Ident {
 462     Ident::new(ident.name, fld.new_span(ident.span))
 463 }
 464
 465 pub fn noop_fold_usize<T: Folder>(i: usize, _: &mut T) -> usize {
 466     i
 467 }
 468
 469 pub fn noop_fold_path<T: Folder>(Path { segments, span }: Path, fld: &mut T) -> Path {
 470     Path {
 471         segments: segments.move_map(|PathSegment { ident, id, args }| PathSegment {
 472             ident: fld.fold_ident(ident),
 473             id: fld.new_id(id),
 474             args: args.map(|args| args.map(|args| fld.fold_generic_args(args))),
 475         }),
 476         span: fld.new_span(span)
 477     }
 478 }
 479
 480 pub fn noop_fold_qpath<T: Folder>(qself: Option<QSelf>,
 481                                   path: Path,
 482                                   fld: &mut T) -> (Option<QSelf>, Path) {
 483     let qself = qself.map(|QSelf { ty, path_span, position }| {
 484         QSelf {
 485             ty: fld.fold_ty(ty),
 486             path_span: fld.new_span(path_span),
 487             position,
 488         }
 489     });
 490     (qself, fld.fold_path(path))
 491 }
 492
 493 pub fn noop_fold_generic_args<T: Folder>(generic_args: GenericArgs, fld: &mut T) -> GenericArgs
 494 {
 495     match generic_args {
 496         GenericArgs::AngleBracketed(data) => {
 497             GenericArgs::AngleBracketed(fld.fold_angle_bracketed_parameter_data(data))
 498         }
 499         GenericArgs::Parenthesized(data) => {
 500             GenericArgs::Parenthesized(fld.fold_parenthesized_parameter_data(data))
 501         }
 502     }
 503 }
 504
 505 pub fn noop_fold_angle_bracketed_parameter_data<T: Folder>(data: AngleBracketedArgs,
 506                                                            fld: &mut T)
 507                                                            -> AngleBracketedArgs
 508 {
 509     let AngleBracketedArgs { args, bindings, span } = data;
 510     AngleBracketedArgs {
 511         args: args.move_map(|arg| fld.fold_generic_arg(arg)),
 512         bindings: bindings.move_map(|b| fld.fold_ty_binding(b)),
 513         span: fld.new_span(span)
 514     }
 515 }
 516
 517 pub fn noop_fold_parenthesized_parameter_data<T: Folder>(data: ParenthesisedArgs,
 518                                                          fld: &mut T)
 519                                                          -> ParenthesisedArgs
 520 {
 521     let ParenthesisedArgs { inputs, output, span } = data;
 522     ParenthesisedArgs {
 523         inputs: inputs.move_map(|ty| fld.fold_ty(ty)),
 524         output: output.map(|ty| fld.fold_ty(ty)),
 525         span: fld.new_span(span)
 526     }
 527 }
 528
 529 pub fn noop_fold_local<T: Folder>(l: P<Local>, fld: &mut T) -> P<Local> {
 530     l.map(|Local {id, pat, ty, init, span, attrs}| Local {
 531         id: fld.new_id(id),
 532         pat: fld.fold_pat(pat),
 533         ty: ty.map(|t| fld.fold_ty(t)),
 534         init: init.map(|e| fld.fold_expr(e)),
 535         span: fld.new_span(span),
 536         attrs: fold_attrs(attrs.into(), fld).into(),
 537     })
 538 }
 539
 540 pub fn noop_fold_attribute<T: Folder>(attr: Attribute, fld: &mut T) -> Option<Attribute> {
 541     Some(Attribute {
 542         id: attr.id,
 543         style: attr.style,
 544         path: fld.fold_path(attr.path),
 545         tokens: fld.fold_tts(attr.tokens),
 546         is_sugared_doc: attr.is_sugared_doc,
 547         span: fld.new_span(attr.span),
 548     })
 549 }
 550
 551 pub fn noop_fold_mac<T: Folder>(Spanned {node, span}: Mac, fld: &mut T) -> Mac {
 552     Spanned {
 553         node: Mac_ {
 554             tts: fld.fold_tts(node.stream()).into(),
 555             path: fld.fold_path(node.path),
 556             delim: node.delim,
 557         },
 558         span: fld.new_span(span)
 559     }
 560 }
 561
 562 pub fn noop_fold_macro_def<T: Folder>(def: MacroDef, fld: &mut T) -> MacroDef {
 563     MacroDef {
 564         tokens: fld.fold_tts(def.tokens.into()).into(),
 565         legacy: def.legacy,
 566     }
 567 }
 568
 569 pub fn noop_fold_meta_list_item<T: Folder>(li: NestedMetaItem, fld: &mut T)
 570     -> NestedMetaItem {
 571     Spanned {
 572         node: match li.node {
 573             NestedMetaItemKind::MetaItem(mi) =>  {
 574                 NestedMetaItemKind::MetaItem(fld.fold_meta_item(mi))
 575             },
 576             NestedMetaItemKind::Literal(lit) => NestedMetaItemKind::Literal(lit)
 577         },
 578         span: fld.new_span(li.span)
 579     }
 580 }
 581
 582 pub fn noop_fold_meta_item<T: Folder>(mi: MetaItem, fld: &mut T) -> MetaItem {
 583     MetaItem {
 584         ident: mi.ident,
 585         node: match mi.node {
 586             MetaItemKind::Word => MetaItemKind::Word,
 587             MetaItemKind::List(mis) => {
 588                 MetaItemKind::List(mis.move_map(|e| fld.fold_meta_list_item(e)))
 589             },
 590             MetaItemKind::NameValue(s) => MetaItemKind::NameValue(s),
 591         },
 592         span: fld.new_span(mi.span)
 593     }
 594 }
 595
 596 pub fn noop_fold_arg<T: Folder>(Arg {id, pat, ty}: Arg, fld: &mut T) -> Arg {
 597     Arg {
 598         id: fld.new_id(id),
 599         pat: fld.fold_pat(pat),
 600         ty: fld.fold_ty(ty)
 601     }
 602 }
 603
 604 pub fn noop_fold_tt<T: Folder>(tt: TokenTree, fld: &mut T) -> TokenTree {
 605     match tt {
 606         TokenTree::Token(span, tok) =>
 607             TokenTree::Token(fld.new_span(span), fld.fold_token(tok)),
 608         TokenTree::Delimited(span, delim, tts) => TokenTree::Delimited(
 609             DelimSpan::from_pair(fld.new_span(span.open), fld.new_span(span.close)),
 610             delim,
 611             fld.fold_tts(tts.stream()).into(),
 612         ),
 613     }
 614 }
 615
 616 pub fn noop_fold_tts<T: Folder>(tts: TokenStream, fld: &mut T) -> TokenStream {
 617     tts.map(|tt| fld.fold_tt(tt))
 618 }
 619
 620 // apply ident folder if it's an ident, apply other folds to interpolated nodes
 621 pub fn noop_fold_token<T: Folder>(t: token::Token, fld: &mut T) -> token::Token {
 622     match t {
 623         token::Ident(id, is_raw) => token::Ident(fld.fold_ident(id), is_raw),
 624         token::Lifetime(id) => token::Lifetime(fld.fold_ident(id)),
 625         token::Interpolated(nt) => {
 626             let nt = match Lrc::try_unwrap(nt) {
 627                 Ok(nt) => nt,
 628                 Err(nt) => (*nt).clone(),
 629             };
 630             Token::interpolated(fld.fold_interpolated(nt.0))
 631         }
 632         _ => t
 633     }
 634 }
 635
 636 /// apply folder to elements of interpolated nodes
 637 //
 638 // N.B., this can occur only when applying a fold to partially expanded code, where
 639 // parsed pieces have gotten implanted ito *other* macro invocations. This is relevant
 640 // for macro hygiene, but possibly not elsewhere.
 641 //
 642 // One problem here occurs because the types for fold_item, fold_stmt, etc. allow the
 643 // folder to return *multiple* items; this is a problem for the nodes here, because
 644 // they insist on having exactly one piece. One solution would be to mangle the fold
 645 // trait to include one-to-many and one-to-one versions of these entry points, but that
 646 // would probably confuse a lot of people and help very few. Instead, I'm just going
 647 // to put in dynamic checks. I think the performance impact of this will be pretty much
 648 // nonexistent. The danger is that someone will apply a fold to a partially expanded
 649 // node, and will be confused by the fact that their "fold_item" or "fold_stmt" isn't
 650 // getting called on NtItem or NtStmt nodes. Hopefully they'll wind up reading this
 651 // comment, and doing something appropriate.
 652 //
 653 // BTW, design choice: I considered just changing the type of, e.g., NtItem to contain
 654 // multiple items, but decided against it when I looked at parse_item_or_view_item and
 655 // tried to figure out what I would do with multiple items there....
 656 pub fn noop_fold_interpolated<T: Folder>(nt: token::Nonterminal, fld: &mut T)
 657                                          -> token::Nonterminal {
 658     match nt {
 659         token::NtItem(item) =>
 660             token::NtItem(fld.fold_item(item)
 661                           // this is probably okay, because the only folds likely
 662                           // to peek inside interpolated nodes will be renamings/markings,
 663                           // which map single items to single items
 664                           .expect_one("expected fold to produce exactly one item")),
 665         token::NtBlock(block) => token::NtBlock(fld.fold_block(block)),
 666         token::NtStmt(stmt) =>
 667             token::NtStmt(fld.fold_stmt(stmt)
 668                           // this is probably okay, because the only folds likely
 669                           // to peek inside interpolated nodes will be renamings/markings,
 670                           // which map single items to single items
 671                           .expect_one("expected fold to produce exactly one statement")),
 672         token::NtPat(pat) => token::NtPat(fld.fold_pat(pat)),
 673         token::NtExpr(expr) => token::NtExpr(fld.fold_expr(expr)),
 674         token::NtTy(ty) => token::NtTy(fld.fold_ty(ty)),
 675         token::NtIdent(ident, is_raw) => token::NtIdent(fld.fold_ident(ident), is_raw),
 676         token::NtLifetime(ident) => token::NtLifetime(fld.fold_ident(ident)),
 677         token::NtLiteral(expr) => token::NtLiteral(fld.fold_expr(expr)),
 678         token::NtMeta(meta) => token::NtMeta(fld.fold_meta_item(meta)),
 679         token::NtPath(path) => token::NtPath(fld.fold_path(path)),
 680         token::NtTT(tt) => token::NtTT(fld.fold_tt(tt)),
 681         token::NtArm(arm) => token::NtArm(fld.fold_arm(arm)),
 682         token::NtImplItem(item) =>
 683             token::NtImplItem(fld.fold_impl_item(item)
 684                               .expect_one("expected fold to produce exactly one item")),
 685         token::NtTraitItem(item) =>
 686             token::NtTraitItem(fld.fold_trait_item(item)
 687                                .expect_one("expected fold to produce exactly one item")),
 688         token::NtGenerics(generics) => token::NtGenerics(fld.fold_generics(generics)),
 689         token::NtWhereClause(where_clause) =>
 690             token::NtWhereClause(fld.fold_where_clause(where_clause)),
 691         token::NtArg(arg) => token::NtArg(fld.fold_arg(arg)),
 692         token::NtVis(vis) => token::NtVis(fld.fold_vis(vis)),
 693         token::NtForeignItem(ni) =>
 694             token::NtForeignItem(fld.fold_foreign_item(ni)
 695                                  // see reasoning above
 696                                  .expect_one("expected fold to produce exactly one item")),
 697     }
 698 }
 699
 700 pub fn noop_fold_asyncness<T: Folder>(asyncness: IsAsync, fld: &mut T) -> IsAsync {
 701     match asyncness {
 702         IsAsync::Async { closure_id, return_impl_trait_id } => IsAsync::Async {
 703             closure_id: fld.new_id(closure_id),
 704             return_impl_trait_id: fld.new_id(return_impl_trait_id),
 705         },
 706         IsAsync::NotAsync => IsAsync::NotAsync,
 707     }
 708 }
 709
 710 pub fn noop_fold_fn_decl<T: Folder>(decl: P<FnDecl>, fld: &mut T) -> P<FnDecl> {
 711     decl.map(|FnDecl {inputs, output, variadic}| FnDecl {
 712         inputs: inputs.move_map(|x| fld.fold_arg(x)),
 713         output: match output {
 714             FunctionRetTy::Ty(ty) => FunctionRetTy::Ty(fld.fold_ty(ty)),
 715             FunctionRetTy::Default(span) => FunctionRetTy::Default(fld.new_span(span)),
 716         },
 717         variadic,
 718     })
 719 }
 720
 721 pub fn noop_fold_param_bound<T>(pb: GenericBound, fld: &mut T) -> GenericBound where T: Folder {
 722     match pb {
 723         GenericBound::Trait(ty, modifier) => {
 724             GenericBound::Trait(fld.fold_poly_trait_ref(ty), modifier)
 725         }
 726         GenericBound::Outlives(lifetime) => {
 727             GenericBound::Outlives(noop_fold_lifetime(lifetime, fld))
 728         }
 729     }
 730 }
 731
 732 pub fn noop_fold_generic_param<T: Folder>(param: GenericParam, fld: &mut T) -> GenericParam {
 733     let attrs: Vec<_> = param.attrs.into();
 734     GenericParam {
 735         ident: fld.fold_ident(param.ident),
 736         id: fld.new_id(param.id),
 737         attrs: attrs.into_iter()
 738                     .flat_map(|x| fld.fold_attribute(x).into_iter())
 739                     .collect::<Vec<_>>()
 740                     .into(),
 741         bounds: param.bounds.move_map(|l| noop_fold_param_bound(l, fld)),
 742         kind: match param.kind {
 743             GenericParamKind::Lifetime => GenericParamKind::Lifetime,
 744             GenericParamKind::Type { default } => GenericParamKind::Type {
 745                 default: default.map(|ty| fld.fold_ty(ty))
 746             }
 747         }
 748     }
 749 }
 750
 751 pub fn noop_fold_generic_params<T: Folder>(
 752     params: Vec<GenericParam>,
 753     fld: &mut T
 754 ) -> Vec<GenericParam> {
 755     params.move_map(|p| fld.fold_generic_param(p))
 756 }
 757
 758 pub fn noop_fold_label<T: Folder>(label: Label, fld: &mut T) -> Label {
 759     Label {
 760         ident: fld.fold_ident(label.ident),
 761     }
 762 }
 763
 764 fn noop_fold_lifetime<T: Folder>(l: Lifetime, fld: &mut T) -> Lifetime {
 765     Lifetime {
 766         id: fld.new_id(l.id),
 767         ident: fld.fold_ident(l.ident),
 768     }
 769 }
 770
 771 pub fn noop_fold_generics<T: Folder>(Generics { params, where_clause, span }: Generics,
 772                                      fld: &mut T) -> Generics {
 773     Generics {
 774         params: fld.fold_generic_params(params),
 775         where_clause: fld.fold_where_clause(where_clause),
 776         span: fld.new_span(span),
 777     }
 778 }
 779
 780 pub fn noop_fold_where_clause<T: Folder>(
 781                               WhereClause {id, predicates, span}: WhereClause,
 782                               fld: &mut T)
 783                               -> WhereClause {
 784     WhereClause {
 785         id: fld.new_id(id),
 786         predicates: predicates.move_map(|predicate| {
 787             fld.fold_where_predicate(predicate)
 788         }),
 789         span,
 790     }
 791 }
 792
 793 pub fn noop_fold_where_predicate<T: Folder>(
 794                                  pred: WherePredicate,
 795                                  fld: &mut T)
 796                                  -> WherePredicate {
 797     match pred {
 798         ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate{bound_generic_params,
 799                                                                      bounded_ty,
 800                                                                      bounds,
 801                                                                      span}) => {
 802             ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
 803                 bound_generic_params: fld.fold_generic_params(bound_generic_params),
 804                 bounded_ty: fld.fold_ty(bounded_ty),
 805                 bounds: bounds.move_map(|x| fld.fold_param_bound(x)),
 806                 span: fld.new_span(span)
 807             })
 808         }
 809         ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate{lifetime,
 810                                                                        bounds,
 811                                                                        span}) => {
 812             ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
 813                 span: fld.new_span(span),
 814                 lifetime: noop_fold_lifetime(lifetime, fld),
 815                 bounds: bounds.move_map(|bound| noop_fold_param_bound(bound, fld))
 816             })
 817         }
 818         ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{id,
 819                                                                lhs_ty,
 820                                                                rhs_ty,
 821                                                                span}) => {
 822             ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{
 823                 id: fld.new_id(id),
 824                 lhs_ty: fld.fold_ty(lhs_ty),
 825                 rhs_ty: fld.fold_ty(rhs_ty),
 826                 span: fld.new_span(span)
 827             })
 828         }
 829     }
 830 }
 831
 832 pub fn noop_fold_variant_data<T: Folder>(vdata: VariantData, fld: &mut T) -> VariantData {
 833     match vdata {
 834         ast::VariantData::Struct(fields, id) => {
 835             ast::VariantData::Struct(fields.move_map(|f| fld.fold_struct_field(f)),
 836                                      fld.new_id(id))
 837         }
 838         ast::VariantData::Tuple(fields, id) => {
 839             ast::VariantData::Tuple(fields.move_map(|f| fld.fold_struct_field(f)),
 840                                     fld.new_id(id))
 841         }
 842         ast::VariantData::Unit(id) => ast::VariantData::Unit(fld.new_id(id))
 843     }
 844 }
 845
 846 pub fn noop_fold_trait_ref<T: Folder>(p: TraitRef, fld: &mut T) -> TraitRef {
 847     let id = fld.new_id(p.ref_id);
 848     let TraitRef {
 849         path,
 850         ref_id: _,
 851     } = p;
 852     ast::TraitRef {
 853         path: fld.fold_path(path),
 854         ref_id: id,
 855     }
 856 }
 857
 858 pub fn noop_fold_poly_trait_ref<T: Folder>(p: PolyTraitRef, fld: &mut T) -> PolyTraitRef {
 859     ast::PolyTraitRef {
 860         bound_generic_params: fld.fold_generic_params(p.bound_generic_params),
 861         trait_ref: fld.fold_trait_ref(p.trait_ref),
 862         span: fld.new_span(p.span),
 863     }
 864 }
 865
 866 pub fn noop_fold_struct_field<T: Folder>(f: StructField, fld: &mut T) -> StructField {
 867     StructField {
 868         span: fld.new_span(f.span),
 869         id: fld.new_id(f.id),
 870         ident: f.ident.map(|ident| fld.fold_ident(ident)),
 871         vis: fld.fold_vis(f.vis),
 872         ty: fld.fold_ty(f.ty),
 873         attrs: fold_attrs(f.attrs, fld),
 874     }
 875 }
 876
 877 pub fn noop_fold_field<T: Folder>(f: Field, folder: &mut T) -> Field {
 878     Field {
 879         ident: folder.fold_ident(f.ident),
 880         expr: folder.fold_expr(f.expr),
 881         span: folder.new_span(f.span),
 882         is_shorthand: f.is_shorthand,
 883         attrs: fold_thin_attrs(f.attrs, folder),
 884     }
 885 }
 886
 887 pub fn noop_fold_mt<T: Folder>(MutTy {ty, mutbl}: MutTy, folder: &mut T) -> MutTy {
 888     MutTy {
 889         ty: folder.fold_ty(ty),
 890         mutbl,
 891     }
 892 }
 893
 894 pub fn noop_fold_opt_bounds<T: Folder>(b: Option<GenericBounds>, folder: &mut T)
 895                                        -> Option<GenericBounds> {
 896     b.map(|bounds| folder.fold_bounds(bounds))
 897 }
 898
 899 fn noop_fold_bounds<T: Folder>(bounds: GenericBounds, folder: &mut T)
 900                           -> GenericBounds {
 901     bounds.move_map(|bound| folder.fold_param_bound(bound))
 902 }
 903
 904 pub fn noop_fold_block<T: Folder>(b: P<Block>, folder: &mut T) -> P<Block> {
 905     b.map(|Block {id, stmts, rules, span, recovered}| Block {
 906         id: folder.new_id(id),
 907         stmts: stmts.move_flat_map(|s| folder.fold_stmt(s).into_iter()),
 908         rules,
 909         span: folder.new_span(span),
 910         recovered,
 911     })
 912 }
 913
 914 pub fn noop_fold_item_kind<T: Folder>(i: ItemKind, folder: &mut T) -> ItemKind {
 915     match i {
 916         ItemKind::ExternCrate(orig_name) => ItemKind::ExternCrate(orig_name),
 917         ItemKind::Use(use_tree) => {
 918             ItemKind::Use(use_tree.map(|tree| folder.fold_use_tree(tree)))
 919         }
 920         ItemKind::Static(t, m, e) => {
 921             ItemKind::Static(folder.fold_ty(t), m, folder.fold_expr(e))
 922         }
 923         ItemKind::Const(t, e) => {
 924             ItemKind::Const(folder.fold_ty(t), folder.fold_expr(e))
 925         }
 926         ItemKind::Fn(decl, header, generics, body) => {
 927             let generics = folder.fold_generics(generics);
 928             let header = folder.fold_fn_header(header);
 929             let decl = folder.fold_fn_decl(decl);
 930             let body = folder.fold_block(body);
 931             ItemKind::Fn(decl, header, generics, body)
 932         }
 933         ItemKind::Mod(m) => ItemKind::Mod(folder.fold_mod(m)),
 934         ItemKind::ForeignMod(nm) => ItemKind::ForeignMod(folder.fold_foreign_mod(nm)),
 935         ItemKind::GlobalAsm(ga) => ItemKind::GlobalAsm(folder.fold_global_asm(ga)),
 936         ItemKind::Ty(t, generics) => {
 937             ItemKind::Ty(folder.fold_ty(t), folder.fold_generics(generics))
 938         }
 939         ItemKind::Existential(bounds, generics) => ItemKind::Existential(
 940             folder.fold_bounds(bounds),
 941             folder.fold_generics(generics),
 942         ),
 943         ItemKind::Enum(enum_definition, generics) => {
 944             let generics = folder.fold_generics(generics);
 945             let variants = enum_definition.variants.move_map(|x| folder.fold_variant(x));
 946             ItemKind::Enum(ast::EnumDef { variants }, generics)
 947         }
 948         ItemKind::Struct(struct_def, generics) => {
 949             let generics = folder.fold_generics(generics);
 950             ItemKind::Struct(folder.fold_variant_data(struct_def), generics)
 951         }
 952         ItemKind::Union(struct_def, generics) => {
 953             let generics = folder.fold_generics(generics);
 954             ItemKind::Union(folder.fold_variant_data(struct_def), generics)
 955         }
 956         ItemKind::Impl(unsafety,
 957                        polarity,
 958                        defaultness,
 959                        generics,
 960                        ifce,
 961                        ty,
 962                        impl_items) => ItemKind::Impl(
 963             unsafety,
 964             polarity,
 965             defaultness,
 966             folder.fold_generics(generics),
 967             ifce.map(|trait_ref| folder.fold_trait_ref(trait_ref)),
 968             folder.fold_ty(ty),
 969             impl_items.move_flat_map(|item| folder.fold_impl_item(item)),
 970         ),
 971         ItemKind::Trait(is_auto, unsafety, generics, bounds, items) => ItemKind::Trait(
 972             is_auto,
 973             unsafety,
 974             folder.fold_generics(generics),
 975             folder.fold_bounds(bounds),
 976             items.move_flat_map(|item| folder.fold_trait_item(item)),
 977         ),
 978         ItemKind::TraitAlias(generics, bounds) => ItemKind::TraitAlias(
 979             folder.fold_generics(generics),
 980             folder.fold_bounds(bounds)),
 981         ItemKind::Mac(m) => ItemKind::Mac(folder.fold_mac(m)),
 982         ItemKind::MacroDef(def) => ItemKind::MacroDef(folder.fold_macro_def(def)),
 983     }
 984 }
 985
 986 pub fn noop_fold_trait_item<T: Folder>(i: TraitItem, folder: &mut T) -> SmallVec<[TraitItem; 1]> {
 987     smallvec![TraitItem {
 988         id: folder.new_id(i.id),
 989         ident: folder.fold_ident(i.ident),
 990         attrs: fold_attrs(i.attrs, folder),
 991         generics: folder.fold_generics(i.generics),
 992         node: match i.node {
 993             TraitItemKind::Const(ty, default) => {
 994                 TraitItemKind::Const(folder.fold_ty(ty),
 995                                default.map(|x| folder.fold_expr(x)))
 996             }
 997             TraitItemKind::Method(sig, body) => {
 998                 TraitItemKind::Method(noop_fold_method_sig(sig, folder),
 999                                 body.map(|x| folder.fold_block(x)))
1000             }
1001             TraitItemKind::Type(bounds, default) => {
1002                 TraitItemKind::Type(folder.fold_bounds(bounds),
1003                               default.map(|x| folder.fold_ty(x)))
1004             }
1005             ast::TraitItemKind::Macro(mac) => {
1006                 TraitItemKind::Macro(folder.fold_mac(mac))
1007             }
1008         },
1009         span: folder.new_span(i.span),
1010         tokens: i.tokens,
1011     }]
1012 }
1013
1014 pub fn noop_fold_impl_item<T: Folder>(i: ImplItem, folder: &mut T)-> SmallVec<[ImplItem; 1]> {
1015     smallvec![ImplItem {
1016         id: folder.new_id(i.id),
1017         vis: folder.fold_vis(i.vis),
1018         ident: folder.fold_ident(i.ident),
1019         attrs: fold_attrs(i.attrs, folder),
1020         generics: folder.fold_generics(i.generics),
1021         defaultness: i.defaultness,
1022         node: match i.node  {
1023             ast::ImplItemKind::Const(ty, expr) => {
1024                 ast::ImplItemKind::Const(folder.fold_ty(ty), folder.fold_expr(expr))
1025             }
1026             ast::ImplItemKind::Method(sig, body) => {
1027                 ast::ImplItemKind::Method(noop_fold_method_sig(sig, folder),
1028                                folder.fold_block(body))
1029             }
1030             ast::ImplItemKind::Type(ty) => ast::ImplItemKind::Type(folder.fold_ty(ty)),
1031             ast::ImplItemKind::Existential(bounds) => {
1032                 ast::ImplItemKind::Existential(folder.fold_bounds(bounds))
1033             },
1034             ast::ImplItemKind::Macro(mac) => ast::ImplItemKind::Macro(folder.fold_mac(mac))
1035         },
1036         span: folder.new_span(i.span),
1037         tokens: i.tokens,
1038     }]
1039 }
1040
1041 pub fn noop_fold_fn_header<T: Folder>(mut header: FnHeader, folder: &mut T) -> FnHeader {
1042     header.asyncness = folder.fold_asyncness(header.asyncness);
1043     header
1044 }
1045
1046 pub fn noop_fold_mod<T: Folder>(Mod {inner, items, inline}: Mod, folder: &mut T) -> Mod {
1047     Mod {
1048         inner: folder.new_span(inner),
1049         items: items.move_flat_map(|x| folder.fold_item(x)),
1050         inline: inline,
1051     }
1052 }
1053
1054 pub fn noop_fold_crate<T: Folder>(Crate {module, attrs, span}: Crate,
1055                                   folder: &mut T) -> Crate {
1056     let mut items = folder.fold_item(P(ast::Item {
1057         ident: keywords::Invalid.ident(),
1058         attrs,
1059         id: ast::DUMMY_NODE_ID,
1060         vis: respan(span.shrink_to_lo(), ast::VisibilityKind::Public),
1061         span,
1062         node: ast::ItemKind::Mod(module),
1063         tokens: None,
1064     })).into_iter();
1065
1066     let (module, attrs, span) = match items.next() {
1067         Some(item) => {
1068             assert!(items.next().is_none(),
1069                     "a crate cannot expand to more than one item");
1070             item.and_then(|ast::Item { attrs, span, node, .. }| {
1071                 match node {
1072                     ast::ItemKind::Mod(m) => (m, attrs, span),
1073                     _ => panic!("fold converted a module to not a module"),
1074                 }
1075             })
1076         }
1077         None => (ast::Mod {
1078             inner: span,
1079             items: vec![],
1080             inline: true,
1081         }, vec![], span)
1082     };
1083
1084     Crate {
1085         module,
1086         attrs,
1087         span,
1088     }
1089 }
1090
1091 // fold one item into possibly many items
1092 pub fn noop_fold_item<T: Folder>(i: P<Item>, folder: &mut T) -> SmallVec<[P<Item>; 1]> {
1093     smallvec![i.map(|i| folder.fold_item_simple(i))]
1094 }
1095
1096 // fold one item into exactly one item
1097 pub fn noop_fold_item_simple<T: Folder>(Item {id, ident, attrs, node, vis, span, tokens}: Item,
1098                                         folder: &mut T) -> Item {
1099     Item {
1100         id: folder.new_id(id),
1101         vis: folder.fold_vis(vis),
1102         ident: folder.fold_ident(ident),
1103         attrs: fold_attrs(attrs, folder),
1104         node: folder.fold_item_kind(node),
1105         span: folder.new_span(span),
1106
1107         // FIXME: if this is replaced with a call to `folder.fold_tts` it causes
1108         //        an ICE during resolve... odd!
1109         tokens,
1110     }
1111 }
1112
1113 pub fn noop_fold_foreign_item<T: Folder>(ni: ForeignItem, folder: &mut T)
1114     -> SmallVec<[ForeignItem; 1]>
1115 {
1116     smallvec![folder.fold_foreign_item_simple(ni)]
1117 }
1118
1119 pub fn noop_fold_foreign_item_simple<T: Folder>(ni: ForeignItem, folder: &mut T) -> ForeignItem {
1120     ForeignItem {
1121         id: folder.new_id(ni.id),
1122         vis: folder.fold_vis(ni.vis),
1123         ident: folder.fold_ident(ni.ident),
1124         attrs: fold_attrs(ni.attrs, folder),
1125         node: match ni.node {
1126             ForeignItemKind::Fn(fdec, generics) => {
1127                 ForeignItemKind::Fn(folder.fold_fn_decl(fdec), folder.fold_generics(generics))
1128             }
1129             ForeignItemKind::Static(t, m) => {
1130                 ForeignItemKind::Static(folder.fold_ty(t), m)
1131             }
1132             ForeignItemKind::Ty => ForeignItemKind::Ty,
1133             ForeignItemKind::Macro(mac) => ForeignItemKind::Macro(folder.fold_mac(mac)),
1134         },
1135         span: folder.new_span(ni.span)
1136     }
1137 }
1138
1139 pub fn noop_fold_method_sig<T: Folder>(sig: MethodSig, folder: &mut T) -> MethodSig {
1140     MethodSig {
1141         header: folder.fold_fn_header(sig.header),
1142         decl: folder.fold_fn_decl(sig.decl)
1143     }
1144 }
1145
1146 pub fn noop_fold_pat<T: Folder>(p: P<Pat>, folder: &mut T) -> P<Pat> {
1147     p.map(|Pat {id, node, span}| Pat {
1148         id: folder.new_id(id),
1149         node: match node {
1150             PatKind::Wild => PatKind::Wild,
1151             PatKind::Ident(binding_mode, ident, sub) => {
1152                 PatKind::Ident(binding_mode,
1153                                folder.fold_ident(ident),
1154                                sub.map(|x| folder.fold_pat(x)))
1155             }
1156             PatKind::Lit(e) => PatKind::Lit(folder.fold_expr(e)),
1157             PatKind::TupleStruct(pth, pats, ddpos) => {
1158                 PatKind::TupleStruct(folder.fold_path(pth),
1159                         pats.move_map(|x| folder.fold_pat(x)), ddpos)
1160             }
1161             PatKind::Path(qself, pth) => {
1162                 let (qself, pth) = folder.fold_qpath(qself, pth);
1163                 PatKind::Path(qself, pth)
1164             }
1165             PatKind::Struct(pth, fields, etc) => {
1166                 let pth = folder.fold_path(pth);
1167                 let fs = fields.move_map(|f| {
1168                     Spanned { span: folder.new_span(f.span),
1169                               node: ast::FieldPat {
1170                                   ident: folder.fold_ident(f.node.ident),
1171                                   pat: folder.fold_pat(f.node.pat),
1172                                   is_shorthand: f.node.is_shorthand,
1173                                   attrs: fold_attrs(f.node.attrs.into(), folder).into()
1174                               }}
1175                 });
1176                 PatKind::Struct(pth, fs, etc)
1177             }
1178             PatKind::Tuple(elts, ddpos) => {
1179                 PatKind::Tuple(elts.move_map(|x| folder.fold_pat(x)), ddpos)
1180             }
1181             PatKind::Box(inner) => PatKind::Box(folder.fold_pat(inner)),
1182             PatKind::Ref(inner, mutbl) => PatKind::Ref(folder.fold_pat(inner), mutbl),
1183             PatKind::Range(e1, e2, Spanned { span, node: end }) => {
1184                 PatKind::Range(folder.fold_expr(e1),
1185                                folder.fold_expr(e2),
1186                                Spanned { span, node: folder.fold_range_end(end) })
1187             },
1188             PatKind::Slice(before, slice, after) => {
1189                 PatKind::Slice(before.move_map(|x| folder.fold_pat(x)),
1190                        slice.map(|x| folder.fold_pat(x)),
1191                        after.move_map(|x| folder.fold_pat(x)))
1192             }
1193             PatKind::Paren(inner) => PatKind::Paren(folder.fold_pat(inner)),
1194             PatKind::Mac(mac) => PatKind::Mac(folder.fold_mac(mac))
1195         },
1196         span: folder.new_span(span)
1197     })
1198 }
1199
1200 pub fn noop_fold_range_end<T: Folder>(end: RangeEnd, _folder: &mut T) -> RangeEnd {
1201     end
1202 }
1203
1204 pub fn noop_fold_anon_const<T: Folder>(constant: AnonConst, folder: &mut T) -> AnonConst {
1205     let AnonConst {id, value} = constant;
1206     AnonConst {
1207         id: folder.new_id(id),
1208         value: folder.fold_expr(value),
1209     }
1210 }
1211
1212 pub fn noop_fold_expr<T: Folder>(Expr {id, node, span, attrs}: Expr, folder: &mut T) -> Expr {
1213     Expr {
1214         node: match node {
1215             ExprKind::Box(e) => {
1216                 ExprKind::Box(folder.fold_expr(e))
1217             }
1218             ExprKind::ObsoleteInPlace(a, b) => {
1219                 ExprKind::ObsoleteInPlace(folder.fold_expr(a), folder.fold_expr(b))
1220             }
1221             ExprKind::Array(exprs) => {
1222                 ExprKind::Array(folder.fold_exprs(exprs))
1223             }
1224             ExprKind::Repeat(expr, count) => {
1225                 ExprKind::Repeat(folder.fold_expr(expr), folder.fold_anon_const(count))
1226             }
1227             ExprKind::Tup(exprs) => ExprKind::Tup(folder.fold_exprs(exprs)),
1228             ExprKind::Call(f, args) => {
1229                 ExprKind::Call(folder.fold_expr(f),
1230                          folder.fold_exprs(args))
1231             }
1232             ExprKind::MethodCall(seg, args) => {
1233                 ExprKind::MethodCall(
1234                     PathSegment {
1235                         ident: folder.fold_ident(seg.ident),
1236                         id: folder.new_id(seg.id),
1237                         args: seg.args.map(|args| {
1238                             args.map(|args| folder.fold_generic_args(args))
1239                         }),
1240                     },
1241                     folder.fold_exprs(args))
1242             }
1243             ExprKind::Binary(binop, lhs, rhs) => {
1244                 ExprKind::Binary(binop,
1245                         folder.fold_expr(lhs),
1246                         folder.fold_expr(rhs))
1247             }
1248             ExprKind::Unary(binop, ohs) => {
1249                 ExprKind::Unary(binop, folder.fold_expr(ohs))
1250             }
1251             ExprKind::Lit(l) => ExprKind::Lit(l),
1252             ExprKind::Cast(expr, ty) => {
1253                 ExprKind::Cast(folder.fold_expr(expr), folder.fold_ty(ty))
1254             }
1255             ExprKind::Type(expr, ty) => {
1256                 ExprKind::Type(folder.fold_expr(expr), folder.fold_ty(ty))
1257             }
1258             ExprKind::AddrOf(m, ohs) => ExprKind::AddrOf(m, folder.fold_expr(ohs)),
1259             ExprKind::If(cond, tr, fl) => {
1260                 ExprKind::If(folder.fold_expr(cond),
1261                        folder.fold_block(tr),
1262                        fl.map(|x| folder.fold_expr(x)))
1263             }
1264             ExprKind::IfLet(pats, expr, tr, fl) => {
1265                 ExprKind::IfLet(pats.move_map(|pat| folder.fold_pat(pat)),
1266                           folder.fold_expr(expr),
1267                           folder.fold_block(tr),
1268                           fl.map(|x| folder.fold_expr(x)))
1269             }
1270             ExprKind::While(cond, body, opt_label) => {
1271                 ExprKind::While(folder.fold_expr(cond),
1272                           folder.fold_block(body),
1273                           opt_label.map(|label| folder.fold_label(label)))
1274             }
1275             ExprKind::WhileLet(pats, expr, body, opt_label) => {
1276                 ExprKind::WhileLet(pats.move_map(|pat| folder.fold_pat(pat)),
1277                              folder.fold_expr(expr),
1278                              folder.fold_block(body),
1279                              opt_label.map(|label| folder.fold_label(label)))
1280             }
1281             ExprKind::ForLoop(pat, iter, body, opt_label) => {
1282                 ExprKind::ForLoop(folder.fold_pat(pat),
1283                             folder.fold_expr(iter),
1284                             folder.fold_block(body),
1285                             opt_label.map(|label| folder.fold_label(label)))
1286             }
1287             ExprKind::Loop(body, opt_label) => {
1288                 ExprKind::Loop(folder.fold_block(body),
1289                                opt_label.map(|label| folder.fold_label(label)))
1290             }
1291             ExprKind::Match(expr, arms) => {
1292                 ExprKind::Match(folder.fold_expr(expr),
1293                           arms.move_map(|x| folder.fold_arm(x)))
1294             }
1295             ExprKind::Closure(capture_clause, asyncness, movability, decl, body, span) => {
1296                 ExprKind::Closure(capture_clause,
1297                                   folder.fold_asyncness(asyncness),
1298                                   movability,
1299                                   folder.fold_fn_decl(decl),
1300                                   folder.fold_expr(body),
1301                                   folder.new_span(span))
1302             }
1303             ExprKind::Block(blk, opt_label) => {
1304                 ExprKind::Block(folder.fold_block(blk),
1305                                 opt_label.map(|label| folder.fold_label(label)))
1306             }
1307             ExprKind::Async(capture_clause, node_id, body) => {
1308                 ExprKind::Async(
1309                     capture_clause,
1310                     folder.new_id(node_id),
1311                     folder.fold_block(body),
1312                 )
1313             }
1314             ExprKind::Assign(el, er) => {
1315                 ExprKind::Assign(folder.fold_expr(el), folder.fold_expr(er))
1316             }
1317             ExprKind::AssignOp(op, el, er) => {
1318                 ExprKind::AssignOp(op,
1319                             folder.fold_expr(el),
1320                             folder.fold_expr(er))
1321             }
1322             ExprKind::Field(el, ident) => {
1323                 ExprKind::Field(folder.fold_expr(el), folder.fold_ident(ident))
1324             }
1325             ExprKind::Index(el, er) => {
1326                 ExprKind::Index(folder.fold_expr(el), folder.fold_expr(er))
1327             }
1328             ExprKind::Range(e1, e2, lim) => {
1329                 ExprKind::Range(e1.map(|x| folder.fold_expr(x)),
1330                                 e2.map(|x| folder.fold_expr(x)),
1331                                 lim)
1332             }
1333             ExprKind::Path(qself, path) => {
1334                 let (qself, path) = folder.fold_qpath(qself, path);
1335                 ExprKind::Path(qself, path)
1336             }
1337             ExprKind::Break(opt_label, opt_expr) => {
1338                 ExprKind::Break(opt_label.map(|label| folder.fold_label(label)),
1339                                 opt_expr.map(|e| folder.fold_expr(e)))
1340             }
1341             ExprKind::Continue(opt_label) => {
1342                 ExprKind::Continue(opt_label.map(|label| folder.fold_label(label)))
1343             }
1344             ExprKind::Ret(e) => ExprKind::Ret(e.map(|x| folder.fold_expr(x))),
1345             ExprKind::InlineAsm(asm) => ExprKind::InlineAsm(asm.map(|asm| {
1346                 InlineAsm {
1347                     inputs: asm.inputs.move_map(|(c, input)| {
1348                         (c, folder.fold_expr(input))
1349                     }),
1350                     outputs: asm.outputs.move_map(|out| {
1351                         InlineAsmOutput {
1352                             constraint: out.constraint,
1353                             expr: folder.fold_expr(out.expr),
1354                             is_rw: out.is_rw,
1355                             is_indirect: out.is_indirect,
1356                         }
1357                     }),
1358                     ..asm
1359                 }
1360             })),
1361             ExprKind::Mac(mac) => ExprKind::Mac(folder.fold_mac(mac)),
1362             ExprKind::Struct(path, fields, maybe_expr) => {
1363                 ExprKind::Struct(folder.fold_path(path),
1364                         fields.move_map(|x| folder.fold_field(x)),
1365                         maybe_expr.map(|x| folder.fold_expr(x)))
1366             },
1367             ExprKind::Paren(ex) => {
1368                 let sub_expr = folder.fold_expr(ex);
1369                 return Expr {
1370                     // Nodes that are equal modulo `Paren` sugar no-ops should have the same ids.
1371                     id: sub_expr.id,
1372                     node: ExprKind::Paren(sub_expr),
1373                     span: folder.new_span(span),
1374                     attrs: fold_attrs(attrs.into(), folder).into(),
1375                 };
1376             }
1377             ExprKind::Yield(ex) => ExprKind::Yield(ex.map(|x| folder.fold_expr(x))),
1378             ExprKind::Try(ex) => ExprKind::Try(folder.fold_expr(ex)),
1379             ExprKind::TryBlock(body) => ExprKind::TryBlock(folder.fold_block(body)),
1380         },
1381         id: folder.new_id(id),
1382         span: folder.new_span(span),
1383         attrs: fold_attrs(attrs.into(), folder).into(),
1384     }
1385 }
1386
1387 pub fn noop_fold_opt_expr<T: Folder>(e: P<Expr>, folder: &mut T) -> Option<P<Expr>> {
1388     Some(folder.fold_expr(e))
1389 }
1390
1391 pub fn noop_fold_exprs<T: Folder>(es: Vec<P<Expr>>, folder: &mut T) -> Vec<P<Expr>> {
1392     es.move_flat_map(|e| folder.fold_opt_expr(e))
1393 }
1394
1395 pub fn noop_fold_stmt<T: Folder>(Stmt {node, span, id}: Stmt, folder: &mut T) -> SmallVec<[Stmt; 1]>
1396 {
1397     let id = folder.new_id(id);
1398     let span = folder.new_span(span);
1399     noop_fold_stmt_kind(node, folder).into_iter().map(|node| {
1400         Stmt { id: id, node: node, span: span }
1401     }).collect()
1402 }
1403
1404 pub fn noop_fold_stmt_kind<T: Folder>(node: StmtKind, folder: &mut T) -> SmallVec<[StmtKind; 1]> {
1405     match node {
1406         StmtKind::Local(local) => smallvec![StmtKind::Local(folder.fold_local(local))],
1407         StmtKind::Item(item) => folder.fold_item(item).into_iter().map(StmtKind::Item).collect(),
1408         StmtKind::Expr(expr) => {
1409             folder.fold_opt_expr(expr).into_iter().map(StmtKind::Expr).collect()
1410         }
1411         StmtKind::Semi(expr) => {
1412             folder.fold_opt_expr(expr).into_iter().map(StmtKind::Semi).collect()
1413         }
1414         StmtKind::Mac(mac) => smallvec![StmtKind::Mac(mac.map(|(mac, semi, attrs)| {
1415             (folder.fold_mac(mac), semi, fold_attrs(attrs.into(), folder).into())
1416         }))],
1417     }
1418 }
1419
1420 pub fn noop_fold_vis<T: Folder>(vis: Visibility, folder: &mut T) -> Visibility {
1421     match vis.node {
1422         VisibilityKind::Restricted { path, id } => {
1423             respan(vis.span, VisibilityKind::Restricted {
1424                 path: path.map(|path| folder.fold_path(path)),
1425                 id: folder.new_id(id),
1426             })
1427         }
1428         _ => vis,
1429     }
1430 }
1431
1432 #[cfg(test)]
1433 mod tests {
1434     use std::io;
1435     use ast::{self, Ident};
1436     use util::parser_testing::{string_to_crate, matches_codepattern};
1437     use print::pprust;
1438     use fold;
1439     use with_globals;
1440     use super::*;
1441
1442     // this version doesn't care about getting comments or docstrings in.
1443     fn fake_print_crate(s: &mut pprust::State,
1444                         krate: &ast::Crate) -> io::Result<()> {
1445         s.print_mod(&krate.module, &krate.attrs)
1446     }
1447
1448     // change every identifier to "zz"
1449     struct ToZzIdentFolder;
1450
1451     impl Folder for ToZzIdentFolder {
1452         fn fold_ident(&mut self, _: ast::Ident) -> ast::Ident {
1453             Ident::from_str("zz")
1454         }
1455         fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
1456             fold::noop_fold_mac(mac, self)
1457         }
1458     }
1459
1460     // maybe add to expand.rs...
1461     macro_rules! assert_pred {
1462         ($pred:expr, $predname:expr, $a:expr , $b:expr) => (
1463             {
1464                 let pred_val = $pred;
1465                 let a_val = $a;
1466                 let b_val = $b;
1467                 if !(pred_val(&a_val, &b_val)) {
1468                     panic!("expected args satisfying {}, got {} and {}",
1469                           $predname, a_val, b_val);
1470                 }
1471             }
1472         )
1473     }
1474
1475     // make sure idents get transformed everywhere
1476     #[test] fn ident_transformation () {
1477         with_globals(|| {
1478             let mut zz_fold = ToZzIdentFolder;
1479             let ast = string_to_crate(
1480                 "#[a] mod b {fn c (d : e, f : g) {h!(i,j,k);l;m}}".to_string());
1481             let folded_crate = zz_fold.fold_crate(ast);
1482             assert_pred!(
1483                 matches_codepattern,
1484                 "matches_codepattern",
1485                 pprust::to_string(|s| fake_print_crate(s, &folded_crate)),
1486                 "#[zz]mod zz{fn zz(zz:zz,zz:zz){zz!(zz,zz,zz);zz;zz}}".to_string());
1487         })
1488     }
1489
1490     // even inside macro defs....
1491     #[test] fn ident_transformation_in_defs () {
1492         with_globals(|| {
1493             let mut zz_fold = ToZzIdentFolder;
1494             let ast = string_to_crate(
1495                 "macro_rules! a {(b $c:expr $(d $e:token)f+ => \
1496                 (g $(d $d $e)+))} ".to_string());
1497             let folded_crate = zz_fold.fold_crate(ast);
1498             assert_pred!(
1499                 matches_codepattern,
1500                 "matches_codepattern",
1501                 pprust::to_string(|s| fake_print_crate(s, &folded_crate)),
1502                 "macro_rules! zz((zz$zz:zz$(zz $zz:zz)zz+=>(zz$(zz$zz$zz)+)));".to_string());
1503         })
1504     }
1505 }