src/libsyntax/fold.rs

   1 //! A Folder represents an AST->AST fold; it accepts an AST piece,
   2 //! and returns a piece of the same type. So, for instance, macro
   3 //! expansion is a Folder that walks over an AST and produces another
   4 //! AST.
   5 //!
   6 //! Note: using a Folder (other than the MacroExpander Folder) on
   7 //! an AST before macro expansion is probably a bad idea. For instance,
   8 //! a folder renaming item names in a module will miss all of those
   9 //! that are created by the expansion of a macro.
  10
  11 use ast::*;
  12 use ast;
  13 use syntax_pos::Span;
  14 use source_map::{Spanned, respan};
  15 use parse::token::{self, Token};
  16 use ptr::P;
  17 use smallvec::{Array, SmallVec};
  18 use symbol::keywords;
  19 use ThinVec;
  20 use tokenstream::*;
  21 use util::move_map::MoveMap;
  22
  23 use rustc_data_structures::sync::Lrc;
  24
  25 pub trait ExpectOne<A: Array> {
  26     fn expect_one(self, err: &'static str) -> A::Item;
  27 }
  28
  29 impl<A: Array> ExpectOne<A> for SmallVec<A> {
  30     fn expect_one(self, err: &'static str) -> A::Item {
  31         assert!(self.len() == 1, err);
  32         self.into_iter().next().unwrap()
  33     }
  34 }
  35
  36 pub trait Folder : Sized {
  37     // Any additions to this trait should happen in form
  38     // of a call to a public `noop_*` function that only calls
  39     // out to the folder again, not other `noop_*` functions.
  40     //
  41     // This is a necessary API workaround to the problem of not
  42     // being able to call out to the super default method
  43     // in an overridden default method.
  44
  45     fn fold_crate(&mut self, c: Crate) -> Crate {
  46         noop_fold_crate(c, self)
  47     }
  48
  49     fn fold_meta_items(&mut self, meta_items: Vec<MetaItem>) -> Vec<MetaItem> {
  50         noop_fold_meta_items(meta_items, self)
  51     }
  52
  53     fn fold_meta_list_item(&mut self, list_item: NestedMetaItem) -> NestedMetaItem {
  54         noop_fold_meta_list_item(list_item, self)
  55     }
  56
  57     fn fold_meta_item(&mut self, meta_item: MetaItem) -> MetaItem {
  58         noop_fold_meta_item(meta_item, self)
  59     }
  60
  61     fn fold_use_tree(&mut self, use_tree: UseTree) -> UseTree {
  62         noop_fold_use_tree(use_tree, self)
  63     }
  64
  65     fn fold_foreign_item(&mut self, ni: ForeignItem) -> SmallVec<[ForeignItem; 1]> {
  66         noop_fold_foreign_item(ni, self)
  67     }
  68
  69     fn fold_foreign_item_simple(&mut self, ni: ForeignItem) -> ForeignItem {
  70         noop_fold_foreign_item_simple(ni, self)
  71     }
  72
  73     fn fold_item(&mut self, i: P<Item>) -> SmallVec<[P<Item>; 1]> {
  74         noop_fold_item(i, self)
  75     }
  76
  77     fn fold_item_simple(&mut self, i: Item) -> Item {
  78         noop_fold_item_simple(i, self)
  79     }
  80
  81     fn fold_fn_header(&mut self, header: FnHeader) -> FnHeader {
  82         noop_fold_fn_header(header, self)
  83     }
  84
  85     fn fold_struct_field(&mut self, sf: StructField) -> StructField {
  86         noop_fold_struct_field(sf, self)
  87     }
  88
  89     fn fold_item_kind(&mut self, i: ItemKind) -> ItemKind {
  90         noop_fold_item_kind(i, self)
  91     }
  92
  93     fn fold_trait_item(&mut self, i: TraitItem) -> SmallVec<[TraitItem; 1]> {
  94         noop_fold_trait_item(i, self)
  95     }
  96
  97     fn fold_impl_item(&mut self, i: ImplItem) -> SmallVec<[ImplItem; 1]> {
  98         noop_fold_impl_item(i, self)
  99     }
 100
 101     fn fold_fn_decl(&mut self, d: P<FnDecl>) -> P<FnDecl> {
 102         noop_fold_fn_decl(d, self)
 103     }
 104
 105     fn fold_asyncness(&mut self, a: IsAsync) -> IsAsync {
 106         noop_fold_asyncness(a, self)
 107     }
 108
 109     fn fold_block(&mut self, b: P<Block>) -> P<Block> {
 110         noop_fold_block(b, self)
 111     }
 112
 113     fn fold_stmt(&mut self, s: Stmt) -> SmallVec<[Stmt; 1]> {
 114         noop_fold_stmt(s, self)
 115     }
 116
 117     fn fold_arm(&mut self, a: Arm) -> Arm {
 118         noop_fold_arm(a, self)
 119     }
 120
 121     fn fold_guard(&mut self, g: Guard) -> Guard {
 122         noop_fold_guard(g, self)
 123     }
 124
 125     fn fold_pat(&mut self, p: P<Pat>) -> P<Pat> {
 126         noop_fold_pat(p, self)
 127     }
 128
 129     fn fold_anon_const(&mut self, c: AnonConst) -> AnonConst {
 130         noop_fold_anon_const(c, self)
 131     }
 132
 133     fn fold_expr(&mut self, e: P<Expr>) -> P<Expr> {
 134         e.map(|e| noop_fold_expr(e, self))
 135     }
 136
 137     fn fold_range_end(&mut self, re: RangeEnd) -> RangeEnd {
 138         noop_fold_range_end(re, self)
 139     }
 140
 141     fn fold_opt_expr(&mut self, e: P<Expr>) -> Option<P<Expr>> {
 142         noop_fold_opt_expr(e, self)
 143     }
 144
 145     fn fold_exprs(&mut self, es: Vec<P<Expr>>) -> Vec<P<Expr>> {
 146         noop_fold_exprs(es, self)
 147     }
 148
 149     fn fold_generic_arg(&mut self, arg: GenericArg) -> GenericArg {
 150         match arg {
 151             GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.fold_lifetime(lt)),
 152             GenericArg::Type(ty) => GenericArg::Type(self.fold_ty(ty)),
 153         }
 154     }
 155
 156     fn fold_ty(&mut self, t: P<Ty>) -> P<Ty> {
 157         noop_fold_ty(t, self)
 158     }
 159
 160     fn fold_lifetime(&mut self, l: Lifetime) -> Lifetime {
 161         noop_fold_lifetime(l, self)
 162     }
 163
 164     fn fold_ty_binding(&mut self, t: TypeBinding) -> TypeBinding {
 165         noop_fold_ty_binding(t, self)
 166     }
 167
 168     fn fold_mod(&mut self, m: Mod) -> Mod {
 169         noop_fold_mod(m, self)
 170     }
 171
 172     fn fold_foreign_mod(&mut self, nm: ForeignMod) -> ForeignMod {
 173         noop_fold_foreign_mod(nm, self)
 174     }
 175
 176     fn fold_global_asm(&mut self, ga: P<GlobalAsm>) -> P<GlobalAsm> {
 177         noop_fold_global_asm(ga, self)
 178     }
 179
 180     fn fold_variant(&mut self, v: Variant) -> Variant {
 181         noop_fold_variant(v, self)
 182     }
 183
 184     fn fold_ident(&mut self, i: Ident) -> Ident {
 185         noop_fold_ident(i, self)
 186     }
 187
 188     fn fold_usize(&mut self, i: usize) -> usize {
 189         noop_fold_usize(i, self)
 190     }
 191
 192     fn fold_path(&mut self, p: Path) -> Path {
 193         noop_fold_path(p, self)
 194     }
 195
 196     fn fold_qpath(&mut self, qs: Option<QSelf>, p: Path) -> (Option<QSelf>, Path) {
 197         noop_fold_qpath(qs, p, self)
 198     }
 199
 200     fn fold_generic_args(&mut self, p: GenericArgs) -> GenericArgs {
 201         noop_fold_generic_args(p, self)
 202     }
 203
 204     fn fold_angle_bracketed_parameter_data(&mut self, p: AngleBracketedArgs)
 205                                            -> AngleBracketedArgs
 206     {
 207         noop_fold_angle_bracketed_parameter_data(p, self)
 208     }
 209
 210     fn fold_parenthesized_parameter_data(&mut self, p: ParenthesisedArgs)
 211                                          -> ParenthesisedArgs
 212     {
 213         noop_fold_parenthesized_parameter_data(p, self)
 214     }
 215
 216     fn fold_local(&mut self, l: P<Local>) -> P<Local> {
 217         noop_fold_local(l, self)
 218     }
 219
 220     fn fold_mac(&mut self, _mac: Mac) -> Mac {
 221         panic!("fold_mac disabled by default");
 222         // N.B., see note about macros above.
 223         // if you really want a folder that
 224         // works on macros, use this
 225         // definition in your trait impl:
 226         // fold::noop_fold_mac(_mac, self)
 227     }
 228
 229     fn fold_macro_def(&mut self, def: MacroDef) -> MacroDef {
 230         noop_fold_macro_def(def, self)
 231     }
 232
 233     fn fold_label(&mut self, label: Label) -> Label {
 234         noop_fold_label(label, self)
 235     }
 236
 237     fn fold_attribute(&mut self, at: Attribute) -> Option<Attribute> {
 238         noop_fold_attribute(at, self)
 239     }
 240
 241     fn fold_arg(&mut self, a: Arg) -> Arg {
 242         noop_fold_arg(a, self)
 243     }
 244
 245     fn fold_generics(&mut self, generics: Generics) -> Generics {
 246         noop_fold_generics(generics, self)
 247     }
 248
 249     fn fold_trait_ref(&mut self, p: TraitRef) -> TraitRef {
 250         noop_fold_trait_ref(p, self)
 251     }
 252
 253     fn fold_poly_trait_ref(&mut self, p: PolyTraitRef) -> PolyTraitRef {
 254         noop_fold_poly_trait_ref(p, self)
 255     }
 256
 257     fn fold_variant_data(&mut self, vdata: VariantData) -> VariantData {
 258         noop_fold_variant_data(vdata, self)
 259     }
 260
 261     fn fold_generic_param(&mut self, param: GenericParam) -> GenericParam {
 262         noop_fold_generic_param(param, self)
 263     }
 264
 265     fn fold_generic_params(&mut self, params: Vec<GenericParam>) -> Vec<GenericParam> {
 266         noop_fold_generic_params(params, self)
 267     }
 268
 269     fn fold_tt(&mut self, tt: TokenTree) -> TokenTree {
 270         noop_fold_tt(tt, self)
 271     }
 272
 273     fn fold_tts(&mut self, tts: TokenStream) -> TokenStream {
 274         noop_fold_tts(tts, self)
 275     }
 276
 277     fn fold_token(&mut self, t: token::Token) -> token::Token {
 278         noop_fold_token(t, self)
 279     }
 280
 281     fn fold_interpolated(&mut self, nt: token::Nonterminal) -> token::Nonterminal {
 282         noop_fold_interpolated(nt, self)
 283     }
 284
 285     fn fold_opt_bounds(&mut self, b: Option<GenericBounds>) -> Option<GenericBounds> {
 286         noop_fold_opt_bounds(b, self)
 287     }
 288
 289     fn fold_bounds(&mut self, b: GenericBounds) -> GenericBounds {
 290         noop_fold_bounds(b, self)
 291     }
 292
 293     fn fold_param_bound(&mut self, tpb: GenericBound) -> GenericBound {
 294         noop_fold_param_bound(tpb, self)
 295     }
 296
 297     fn fold_mt(&mut self, mt: MutTy) -> MutTy {
 298         noop_fold_mt(mt, self)
 299     }
 300
 301     fn fold_field(&mut self, field: Field) -> Field {
 302         noop_fold_field(field, self)
 303     }
 304
 305     fn fold_where_clause(&mut self, where_clause: WhereClause)
 306                          -> WhereClause {
 307         noop_fold_where_clause(where_clause, self)
 308     }
 309
 310     fn fold_where_predicate(&mut self, where_predicate: WherePredicate)
 311                             -> WherePredicate {
 312         noop_fold_where_predicate(where_predicate, self)
 313     }
 314
 315     fn fold_vis(&mut self, vis: Visibility) -> Visibility {
 316         noop_fold_vis(vis, self)
 317     }
 318
 319     fn new_id(&mut self, i: NodeId) -> NodeId {
 320         i
 321     }
 322
 323     fn new_span(&mut self, sp: Span) -> Span {
 324         sp
 325     }
 326 }
 327
 328 pub fn noop_fold_meta_items<T: Folder>(meta_items: Vec<MetaItem>, fld: &mut T) -> Vec<MetaItem> {
 329     meta_items.move_map(|x| fld.fold_meta_item(x))
 330 }
 331
 332 pub fn noop_fold_use_tree<T: Folder>(use_tree: UseTree, fld: &mut T) -> UseTree {
 333     UseTree {
 334         span: fld.new_span(use_tree.span),
 335         prefix: fld.fold_path(use_tree.prefix),
 336         kind: match use_tree.kind {
 337             UseTreeKind::Simple(rename, id1, id2) =>
 338                 UseTreeKind::Simple(rename.map(|ident| fld.fold_ident(ident)),
 339                                     fld.new_id(id1), fld.new_id(id2)),
 340             UseTreeKind::Glob => UseTreeKind::Glob,
 341             UseTreeKind::Nested(items) => UseTreeKind::Nested(items.move_map(|(tree, id)| {
 342                 (fld.fold_use_tree(tree), fld.new_id(id))
 343             })),
 344         },
 345     }
 346 }
 347
 348 pub fn fold_attrs<T: Folder>(attrs: Vec<Attribute>, fld: &mut T) -> Vec<Attribute> {
 349     attrs.move_flat_map(|x| fld.fold_attribute(x))
 350 }
 351
 352 pub fn fold_thin_attrs<T: Folder>(attrs: ThinVec<Attribute>, fld: &mut T) -> ThinVec<Attribute> {
 353     fold_attrs(attrs.into(), fld).into()
 354 }
 355
 356 pub fn noop_fold_arm<T: Folder>(Arm {attrs, pats, guard, body}: Arm,
 357     fld: &mut T) -> Arm {
 358     Arm {
 359         attrs: fold_attrs(attrs, fld),
 360         pats: pats.move_map(|x| fld.fold_pat(x)),
 361         guard: guard.map(|x| fld.fold_guard(x)),
 362         body: fld.fold_expr(body),
 363     }
 364 }
 365
 366 pub fn noop_fold_guard<T: Folder>(g: Guard, fld: &mut T) -> Guard {
 367     match g {
 368         Guard::If(e) => Guard::If(fld.fold_expr(e)),
 369     }
 370 }
 371
 372 pub fn noop_fold_ty_binding<T: Folder>(b: TypeBinding, fld: &mut T) -> TypeBinding {
 373     TypeBinding {
 374         id: fld.new_id(b.id),
 375         ident: fld.fold_ident(b.ident),
 376         ty: fld.fold_ty(b.ty),
 377         span: fld.new_span(b.span),
 378     }
 379 }
 380
 381 pub fn noop_fold_ty<T: Folder>(t: P<Ty>, fld: &mut T) -> P<Ty> {
 382     t.map(|Ty {id, node, span}| Ty {
 383         id: fld.new_id(id),
 384         node: match node {
 385             TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err => node,
 386             TyKind::Slice(ty) => TyKind::Slice(fld.fold_ty(ty)),
 387             TyKind::Ptr(mt) => TyKind::Ptr(fld.fold_mt(mt)),
 388             TyKind::Rptr(region, mt) => {
 389                 TyKind::Rptr(region.map(|lt| noop_fold_lifetime(lt, fld)), fld.fold_mt(mt))
 390             }
 391             TyKind::BareFn(f) => {
 392                 TyKind::BareFn(f.map(|BareFnTy {generic_params, unsafety, abi, decl}| BareFnTy {
 393                     generic_params: fld.fold_generic_params(generic_params),
 394                     unsafety,
 395                     abi,
 396                     decl: fld.fold_fn_decl(decl)
 397                 }))
 398             }
 399             TyKind::Never => node,
 400             TyKind::Tup(tys) => TyKind::Tup(tys.move_map(|ty| fld.fold_ty(ty))),
 401             TyKind::Paren(ty) => TyKind::Paren(fld.fold_ty(ty)),
 402             TyKind::Path(qself, path) => {
 403                 let (qself, path) = fld.fold_qpath(qself, path);
 404                 TyKind::Path(qself, path)
 405             }
 406             TyKind::Array(ty, length) => {
 407                 TyKind::Array(fld.fold_ty(ty), fld.fold_anon_const(length))
 408             }
 409             TyKind::Typeof(expr) => {
 410                 TyKind::Typeof(fld.fold_anon_const(expr))
 411             }
 412             TyKind::TraitObject(bounds, syntax) => {
 413                 TyKind::TraitObject(bounds.move_map(|b| fld.fold_param_bound(b)), syntax)
 414             }
 415             TyKind::ImplTrait(id, bounds) => {
 416                 TyKind::ImplTrait(fld.new_id(id), bounds.move_map(|b| fld.fold_param_bound(b)))
 417             }
 418             TyKind::Mac(mac) => {
 419                 TyKind::Mac(fld.fold_mac(mac))
 420             }
 421         },
 422         span: fld.new_span(span)
 423     })
 424 }
 425
 426 pub fn noop_fold_foreign_mod<T: Folder>(ForeignMod {abi, items}: ForeignMod,
 427                                         fld: &mut T) -> ForeignMod {
 428     ForeignMod {
 429         abi,
 430         items: items.move_flat_map(|x| fld.fold_foreign_item(x)),
 431     }
 432 }
 433
 434 pub fn noop_fold_global_asm<T: Folder>(ga: P<GlobalAsm>,
 435                                        _: &mut T) -> P<GlobalAsm> {
 436     ga
 437 }
 438
 439 pub fn noop_fold_variant<T: Folder>(v: Variant, fld: &mut T) -> Variant {
 440     Spanned {
 441         node: Variant_ {
 442             ident: fld.fold_ident(v.node.ident),
 443             attrs: fold_attrs(v.node.attrs, fld),
 444             data: fld.fold_variant_data(v.node.data),
 445             disr_expr: v.node.disr_expr.map(|e| fld.fold_anon_const(e)),
 446         },
 447         span: fld.new_span(v.span),
 448     }
 449 }
 450
 451 pub fn noop_fold_ident<T: Folder>(ident: Ident, fld: &mut T) -> Ident {
 452     Ident::new(ident.name, fld.new_span(ident.span))
 453 }
 454
 455 pub fn noop_fold_usize<T: Folder>(i: usize, _: &mut T) -> usize {
 456     i
 457 }
 458
 459 pub fn noop_fold_path<T: Folder>(Path { segments, span }: Path, fld: &mut T) -> Path {
 460     Path {
 461         segments: segments.move_map(|PathSegment { ident, id, args }| PathSegment {
 462             ident: fld.fold_ident(ident),
 463             id: fld.new_id(id),
 464             args: args.map(|args| args.map(|args| fld.fold_generic_args(args))),
 465         }),
 466         span: fld.new_span(span)
 467     }
 468 }
 469
 470 pub fn noop_fold_qpath<T: Folder>(qself: Option<QSelf>,
 471                                   path: Path,
 472                                   fld: &mut T) -> (Option<QSelf>, Path) {
 473     let qself = qself.map(|QSelf { ty, path_span, position }| {
 474         QSelf {
 475             ty: fld.fold_ty(ty),
 476             path_span: fld.new_span(path_span),
 477             position,
 478         }
 479     });
 480     (qself, fld.fold_path(path))
 481 }
 482
 483 pub fn noop_fold_generic_args<T: Folder>(generic_args: GenericArgs, fld: &mut T) -> GenericArgs
 484 {
 485     match generic_args {
 486         GenericArgs::AngleBracketed(data) => {
 487             GenericArgs::AngleBracketed(fld.fold_angle_bracketed_parameter_data(data))
 488         }
 489         GenericArgs::Parenthesized(data) => {
 490             GenericArgs::Parenthesized(fld.fold_parenthesized_parameter_data(data))
 491         }
 492     }
 493 }
 494
 495 pub fn noop_fold_angle_bracketed_parameter_data<T: Folder>(data: AngleBracketedArgs,
 496                                                            fld: &mut T)
 497                                                            -> AngleBracketedArgs
 498 {
 499     let AngleBracketedArgs { args, bindings, span } = data;
 500     AngleBracketedArgs {
 501         args: args.move_map(|arg| fld.fold_generic_arg(arg)),
 502         bindings: bindings.move_map(|b| fld.fold_ty_binding(b)),
 503         span: fld.new_span(span)
 504     }
 505 }
 506
 507 pub fn noop_fold_parenthesized_parameter_data<T: Folder>(data: ParenthesisedArgs,
 508                                                          fld: &mut T)
 509                                                          -> ParenthesisedArgs
 510 {
 511     let ParenthesisedArgs { inputs, output, span } = data;
 512     ParenthesisedArgs {
 513         inputs: inputs.move_map(|ty| fld.fold_ty(ty)),
 514         output: output.map(|ty| fld.fold_ty(ty)),
 515         span: fld.new_span(span)
 516     }
 517 }
 518
 519 pub fn noop_fold_local<T: Folder>(l: P<Local>, fld: &mut T) -> P<Local> {
 520     l.map(|Local {id, pat, ty, init, span, attrs}| Local {
 521         id: fld.new_id(id),
 522         pat: fld.fold_pat(pat),
 523         ty: ty.map(|t| fld.fold_ty(t)),
 524         init: init.map(|e| fld.fold_expr(e)),
 525         span: fld.new_span(span),
 526         attrs: fold_attrs(attrs.into(), fld).into(),
 527     })
 528 }
 529
 530 pub fn noop_fold_attribute<T: Folder>(attr: Attribute, fld: &mut T) -> Option<Attribute> {
 531     Some(Attribute {
 532         id: attr.id,
 533         style: attr.style,
 534         path: fld.fold_path(attr.path),
 535         tokens: fld.fold_tts(attr.tokens),
 536         is_sugared_doc: attr.is_sugared_doc,
 537         span: fld.new_span(attr.span),
 538     })
 539 }
 540
 541 pub fn noop_fold_mac<T: Folder>(Spanned {node, span}: Mac, fld: &mut T) -> Mac {
 542     Spanned {
 543         node: Mac_ {
 544             tts: fld.fold_tts(node.stream()).into(),
 545             path: fld.fold_path(node.path),
 546             delim: node.delim,
 547         },
 548         span: fld.new_span(span)
 549     }
 550 }
 551
 552 pub fn noop_fold_macro_def<T: Folder>(def: MacroDef, fld: &mut T) -> MacroDef {
 553     MacroDef {
 554         tokens: fld.fold_tts(def.tokens.into()).into(),
 555         legacy: def.legacy,
 556     }
 557 }
 558
 559 pub fn noop_fold_meta_list_item<T: Folder>(li: NestedMetaItem, fld: &mut T)
 560     -> NestedMetaItem {
 561     Spanned {
 562         node: match li.node {
 563             NestedMetaItemKind::MetaItem(mi) =>  {
 564                 NestedMetaItemKind::MetaItem(fld.fold_meta_item(mi))
 565             },
 566             NestedMetaItemKind::Literal(lit) => NestedMetaItemKind::Literal(lit)
 567         },
 568         span: fld.new_span(li.span)
 569     }
 570 }
 571
 572 pub fn noop_fold_meta_item<T: Folder>(mi: MetaItem, fld: &mut T) -> MetaItem {
 573     MetaItem {
 574         ident: mi.ident,
 575         node: match mi.node {
 576             MetaItemKind::Word => MetaItemKind::Word,
 577             MetaItemKind::List(mis) => {
 578                 MetaItemKind::List(mis.move_map(|e| fld.fold_meta_list_item(e)))
 579             },
 580             MetaItemKind::NameValue(s) => MetaItemKind::NameValue(s),
 581         },
 582         span: fld.new_span(mi.span)
 583     }
 584 }
 585
 586 pub fn noop_fold_arg<T: Folder>(Arg {id, pat, ty}: Arg, fld: &mut T) -> Arg {
 587     Arg {
 588         id: fld.new_id(id),
 589         pat: fld.fold_pat(pat),
 590         ty: fld.fold_ty(ty)
 591     }
 592 }
 593
 594 pub fn noop_fold_tt<T: Folder>(tt: TokenTree, fld: &mut T) -> TokenTree {
 595     match tt {
 596         TokenTree::Token(span, tok) =>
 597             TokenTree::Token(fld.new_span(span), fld.fold_token(tok)),
 598         TokenTree::Delimited(span, delim, tts) => TokenTree::Delimited(
 599             DelimSpan::from_pair(fld.new_span(span.open), fld.new_span(span.close)),
 600             delim,
 601             fld.fold_tts(tts.stream()).into(),
 602         ),
 603     }
 604 }
 605
 606 pub fn noop_fold_tts<T: Folder>(tts: TokenStream, fld: &mut T) -> TokenStream {
 607     tts.map(|tt| fld.fold_tt(tt))
 608 }
 609
 610 // apply ident folder if it's an ident, apply other folds to interpolated nodes
 611 pub fn noop_fold_token<T: Folder>(t: token::Token, fld: &mut T) -> token::Token {
 612     match t {
 613         token::Ident(id, is_raw) => token::Ident(fld.fold_ident(id), is_raw),
 614         token::Lifetime(id) => token::Lifetime(fld.fold_ident(id)),
 615         token::Interpolated(nt) => {
 616             let nt = match Lrc::try_unwrap(nt) {
 617                 Ok(nt) => nt,
 618                 Err(nt) => (*nt).clone(),
 619             };
 620             Token::interpolated(fld.fold_interpolated(nt.0))
 621         }
 622         _ => t
 623     }
 624 }
 625
 626 /// apply folder to elements of interpolated nodes
 627 //
 628 // N.B., this can occur only when applying a fold to partially expanded code, where
 629 // parsed pieces have gotten implanted ito *other* macro invocations. This is relevant
 630 // for macro hygiene, but possibly not elsewhere.
 631 //
 632 // One problem here occurs because the types for fold_item, fold_stmt, etc. allow the
 633 // folder to return *multiple* items; this is a problem for the nodes here, because
 634 // they insist on having exactly one piece. One solution would be to mangle the fold
 635 // trait to include one-to-many and one-to-one versions of these entry points, but that
 636 // would probably confuse a lot of people and help very few. Instead, I'm just going
 637 // to put in dynamic checks. I think the performance impact of this will be pretty much
 638 // nonexistent. The danger is that someone will apply a fold to a partially expanded
 639 // node, and will be confused by the fact that their "fold_item" or "fold_stmt" isn't
 640 // getting called on NtItem or NtStmt nodes. Hopefully they'll wind up reading this
 641 // comment, and doing something appropriate.
 642 //
 643 // BTW, design choice: I considered just changing the type of, e.g., NtItem to contain
 644 // multiple items, but decided against it when I looked at parse_item_or_view_item and
 645 // tried to figure out what I would do with multiple items there....
 646 pub fn noop_fold_interpolated<T: Folder>(nt: token::Nonterminal, fld: &mut T)
 647                                          -> token::Nonterminal {
 648     match nt {
 649         token::NtItem(item) =>
 650             token::NtItem(fld.fold_item(item)
 651                           // this is probably okay, because the only folds likely
 652                           // to peek inside interpolated nodes will be renamings/markings,
 653                           // which map single items to single items
 654                           .expect_one("expected fold to produce exactly one item")),
 655         token::NtBlock(block) => token::NtBlock(fld.fold_block(block)),
 656         token::NtStmt(stmt) =>
 657             token::NtStmt(fld.fold_stmt(stmt)
 658                           // this is probably okay, because the only folds likely
 659                           // to peek inside interpolated nodes will be renamings/markings,
 660                           // which map single items to single items
 661                           .expect_one("expected fold to produce exactly one statement")),
 662         token::NtPat(pat) => token::NtPat(fld.fold_pat(pat)),
 663         token::NtExpr(expr) => token::NtExpr(fld.fold_expr(expr)),
 664         token::NtTy(ty) => token::NtTy(fld.fold_ty(ty)),
 665         token::NtIdent(ident, is_raw) => token::NtIdent(fld.fold_ident(ident), is_raw),
 666         token::NtLifetime(ident) => token::NtLifetime(fld.fold_ident(ident)),
 667         token::NtLiteral(expr) => token::NtLiteral(fld.fold_expr(expr)),
 668         token::NtMeta(meta) => token::NtMeta(fld.fold_meta_item(meta)),
 669         token::NtPath(path) => token::NtPath(fld.fold_path(path)),
 670         token::NtTT(tt) => token::NtTT(fld.fold_tt(tt)),
 671         token::NtArm(arm) => token::NtArm(fld.fold_arm(arm)),
 672         token::NtImplItem(item) =>
 673             token::NtImplItem(fld.fold_impl_item(item)
 674                               .expect_one("expected fold to produce exactly one item")),
 675         token::NtTraitItem(item) =>
 676             token::NtTraitItem(fld.fold_trait_item(item)
 677                                .expect_one("expected fold to produce exactly one item")),
 678         token::NtGenerics(generics) => token::NtGenerics(fld.fold_generics(generics)),
 679         token::NtWhereClause(where_clause) =>
 680             token::NtWhereClause(fld.fold_where_clause(where_clause)),
 681         token::NtArg(arg) => token::NtArg(fld.fold_arg(arg)),
 682         token::NtVis(vis) => token::NtVis(fld.fold_vis(vis)),
 683         token::NtForeignItem(ni) =>
 684             token::NtForeignItem(fld.fold_foreign_item(ni)
 685                                  // see reasoning above
 686                                  .expect_one("expected fold to produce exactly one item")),
 687     }
 688 }
 689
 690 pub fn noop_fold_asyncness<T: Folder>(asyncness: IsAsync, fld: &mut T) -> IsAsync {
 691     match asyncness {
 692         IsAsync::Async { closure_id, return_impl_trait_id } => IsAsync::Async {
 693             closure_id: fld.new_id(closure_id),
 694             return_impl_trait_id: fld.new_id(return_impl_trait_id),
 695         },
 696         IsAsync::NotAsync => IsAsync::NotAsync,
 697     }
 698 }
 699
 700 pub fn noop_fold_fn_decl<T: Folder>(decl: P<FnDecl>, fld: &mut T) -> P<FnDecl> {
 701     decl.map(|FnDecl {inputs, output, variadic}| FnDecl {
 702         inputs: inputs.move_map(|x| fld.fold_arg(x)),
 703         output: match output {
 704             FunctionRetTy::Ty(ty) => FunctionRetTy::Ty(fld.fold_ty(ty)),
 705             FunctionRetTy::Default(span) => FunctionRetTy::Default(fld.new_span(span)),
 706         },
 707         variadic,
 708     })
 709 }
 710
 711 pub fn noop_fold_param_bound<T>(pb: GenericBound, fld: &mut T) -> GenericBound where T: Folder {
 712     match pb {
 713         GenericBound::Trait(ty, modifier) => {
 714             GenericBound::Trait(fld.fold_poly_trait_ref(ty), modifier)
 715         }
 716         GenericBound::Outlives(lifetime) => {
 717             GenericBound::Outlives(noop_fold_lifetime(lifetime, fld))
 718         }
 719     }
 720 }
 721
 722 pub fn noop_fold_generic_param<T: Folder>(param: GenericParam, fld: &mut T) -> GenericParam {
 723     let attrs: Vec<_> = param.attrs.into();
 724     GenericParam {
 725         ident: fld.fold_ident(param.ident),
 726         id: fld.new_id(param.id),
 727         attrs: attrs.into_iter()
 728                     .flat_map(|x| fld.fold_attribute(x).into_iter())
 729                     .collect::<Vec<_>>()
 730                     .into(),
 731         bounds: param.bounds.move_map(|l| noop_fold_param_bound(l, fld)),
 732         kind: match param.kind {
 733             GenericParamKind::Lifetime => GenericParamKind::Lifetime,
 734             GenericParamKind::Type { default } => GenericParamKind::Type {
 735                 default: default.map(|ty| fld.fold_ty(ty))
 736             }
 737         }
 738     }
 739 }
 740
 741 pub fn noop_fold_generic_params<T: Folder>(
 742     params: Vec<GenericParam>,
 743     fld: &mut T
 744 ) -> Vec<GenericParam> {
 745     params.move_map(|p| fld.fold_generic_param(p))
 746 }
 747
 748 pub fn noop_fold_label<T: Folder>(label: Label, fld: &mut T) -> Label {
 749     Label {
 750         ident: fld.fold_ident(label.ident),
 751     }
 752 }
 753
 754 fn noop_fold_lifetime<T: Folder>(l: Lifetime, fld: &mut T) -> Lifetime {
 755     Lifetime {
 756         id: fld.new_id(l.id),
 757         ident: fld.fold_ident(l.ident),
 758     }
 759 }
 760
 761 pub fn noop_fold_generics<T: Folder>(Generics { params, where_clause, span }: Generics,
 762                                      fld: &mut T) -> Generics {
 763     Generics {
 764         params: fld.fold_generic_params(params),
 765         where_clause: fld.fold_where_clause(where_clause),
 766         span: fld.new_span(span),
 767     }
 768 }
 769
 770 pub fn noop_fold_where_clause<T: Folder>(
 771                               WhereClause {id, predicates, span}: WhereClause,
 772                               fld: &mut T)
 773                               -> WhereClause {
 774     WhereClause {
 775         id: fld.new_id(id),
 776         predicates: predicates.move_map(|predicate| {
 777             fld.fold_where_predicate(predicate)
 778         }),
 779         span,
 780     }
 781 }
 782
 783 pub fn noop_fold_where_predicate<T: Folder>(
 784                                  pred: WherePredicate,
 785                                  fld: &mut T)
 786                                  -> WherePredicate {
 787     match pred {
 788         ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate{bound_generic_params,
 789                                                                      bounded_ty,
 790                                                                      bounds,
 791                                                                      span}) => {
 792             ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
 793                 bound_generic_params: fld.fold_generic_params(bound_generic_params),
 794                 bounded_ty: fld.fold_ty(bounded_ty),
 795                 bounds: bounds.move_map(|x| fld.fold_param_bound(x)),
 796                 span: fld.new_span(span)
 797             })
 798         }
 799         ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate{lifetime,
 800                                                                        bounds,
 801                                                                        span}) => {
 802             ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
 803                 span: fld.new_span(span),
 804                 lifetime: noop_fold_lifetime(lifetime, fld),
 805                 bounds: bounds.move_map(|bound| noop_fold_param_bound(bound, fld))
 806             })
 807         }
 808         ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{id,
 809                                                                lhs_ty,
 810                                                                rhs_ty,
 811                                                                span}) => {
 812             ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{
 813                 id: fld.new_id(id),
 814                 lhs_ty: fld.fold_ty(lhs_ty),
 815                 rhs_ty: fld.fold_ty(rhs_ty),
 816                 span: fld.new_span(span)
 817             })
 818         }
 819     }
 820 }
 821
 822 pub fn noop_fold_variant_data<T: Folder>(vdata: VariantData, fld: &mut T) -> VariantData {
 823     match vdata {
 824         ast::VariantData::Struct(fields, id) => {
 825             ast::VariantData::Struct(fields.move_map(|f| fld.fold_struct_field(f)),
 826                                      fld.new_id(id))
 827         }
 828         ast::VariantData::Tuple(fields, id) => {
 829             ast::VariantData::Tuple(fields.move_map(|f| fld.fold_struct_field(f)),
 830                                     fld.new_id(id))
 831         }
 832         ast::VariantData::Unit(id) => ast::VariantData::Unit(fld.new_id(id))
 833     }
 834 }
 835
 836 pub fn noop_fold_trait_ref<T: Folder>(p: TraitRef, fld: &mut T) -> TraitRef {
 837     let id = fld.new_id(p.ref_id);
 838     let TraitRef {
 839         path,
 840         ref_id: _,
 841     } = p;
 842     ast::TraitRef {
 843         path: fld.fold_path(path),
 844         ref_id: id,
 845     }
 846 }
 847
 848 pub fn noop_fold_poly_trait_ref<T: Folder>(p: PolyTraitRef, fld: &mut T) -> PolyTraitRef {
 849     ast::PolyTraitRef {
 850         bound_generic_params: fld.fold_generic_params(p.bound_generic_params),
 851         trait_ref: fld.fold_trait_ref(p.trait_ref),
 852         span: fld.new_span(p.span),
 853     }
 854 }
 855
 856 pub fn noop_fold_struct_field<T: Folder>(f: StructField, fld: &mut T) -> StructField {
 857     StructField {
 858         span: fld.new_span(f.span),
 859         id: fld.new_id(f.id),
 860         ident: f.ident.map(|ident| fld.fold_ident(ident)),
 861         vis: fld.fold_vis(f.vis),
 862         ty: fld.fold_ty(f.ty),
 863         attrs: fold_attrs(f.attrs, fld),
 864     }
 865 }
 866
 867 pub fn noop_fold_field<T: Folder>(f: Field, folder: &mut T) -> Field {
 868     Field {
 869         ident: folder.fold_ident(f.ident),
 870         expr: folder.fold_expr(f.expr),
 871         span: folder.new_span(f.span),
 872         is_shorthand: f.is_shorthand,
 873         attrs: fold_thin_attrs(f.attrs, folder),
 874     }
 875 }
 876
 877 pub fn noop_fold_mt<T: Folder>(MutTy {ty, mutbl}: MutTy, folder: &mut T) -> MutTy {
 878     MutTy {
 879         ty: folder.fold_ty(ty),
 880         mutbl,
 881     }
 882 }
 883
 884 pub fn noop_fold_opt_bounds<T: Folder>(b: Option<GenericBounds>, folder: &mut T)
 885                                        -> Option<GenericBounds> {
 886     b.map(|bounds| folder.fold_bounds(bounds))
 887 }
 888
 889 fn noop_fold_bounds<T: Folder>(bounds: GenericBounds, folder: &mut T)
 890                           -> GenericBounds {
 891     bounds.move_map(|bound| folder.fold_param_bound(bound))
 892 }
 893
 894 pub fn noop_fold_block<T: Folder>(b: P<Block>, folder: &mut T) -> P<Block> {
 895     b.map(|Block {id, stmts, rules, span}| Block {
 896         id: folder.new_id(id),
 897         stmts: stmts.move_flat_map(|s| folder.fold_stmt(s).into_iter()),
 898         rules,
 899         span: folder.new_span(span),
 900     })
 901 }
 902
 903 pub fn noop_fold_item_kind<T: Folder>(i: ItemKind, folder: &mut T) -> ItemKind {
 904     match i {
 905         ItemKind::ExternCrate(orig_name) => ItemKind::ExternCrate(orig_name),
 906         ItemKind::Use(use_tree) => {
 907             ItemKind::Use(use_tree.map(|tree| folder.fold_use_tree(tree)))
 908         }
 909         ItemKind::Static(t, m, e) => {
 910             ItemKind::Static(folder.fold_ty(t), m, folder.fold_expr(e))
 911         }
 912         ItemKind::Const(t, e) => {
 913             ItemKind::Const(folder.fold_ty(t), folder.fold_expr(e))
 914         }
 915         ItemKind::Fn(decl, header, generics, body) => {
 916             let generics = folder.fold_generics(generics);
 917             let header = folder.fold_fn_header(header);
 918             let decl = folder.fold_fn_decl(decl);
 919             let body = folder.fold_block(body);
 920             ItemKind::Fn(decl, header, generics, body)
 921         }
 922         ItemKind::Mod(m) => ItemKind::Mod(folder.fold_mod(m)),
 923         ItemKind::ForeignMod(nm) => ItemKind::ForeignMod(folder.fold_foreign_mod(nm)),
 924         ItemKind::GlobalAsm(ga) => ItemKind::GlobalAsm(folder.fold_global_asm(ga)),
 925         ItemKind::Ty(t, generics) => {
 926             ItemKind::Ty(folder.fold_ty(t), folder.fold_generics(generics))
 927         }
 928         ItemKind::Existential(bounds, generics) => ItemKind::Existential(
 929             folder.fold_bounds(bounds),
 930             folder.fold_generics(generics),
 931         ),
 932         ItemKind::Enum(enum_definition, generics) => {
 933             let generics = folder.fold_generics(generics);
 934             let variants = enum_definition.variants.move_map(|x| folder.fold_variant(x));
 935             ItemKind::Enum(ast::EnumDef { variants }, generics)
 936         }
 937         ItemKind::Struct(struct_def, generics) => {
 938             let generics = folder.fold_generics(generics);
 939             ItemKind::Struct(folder.fold_variant_data(struct_def), generics)
 940         }
 941         ItemKind::Union(struct_def, generics) => {
 942             let generics = folder.fold_generics(generics);
 943             ItemKind::Union(folder.fold_variant_data(struct_def), generics)
 944         }
 945         ItemKind::Impl(unsafety,
 946                        polarity,
 947                        defaultness,
 948                        generics,
 949                        ifce,
 950                        ty,
 951                        impl_items) => ItemKind::Impl(
 952             unsafety,
 953             polarity,
 954             defaultness,
 955             folder.fold_generics(generics),
 956             ifce.map(|trait_ref| folder.fold_trait_ref(trait_ref)),
 957             folder.fold_ty(ty),
 958             impl_items.move_flat_map(|item| folder.fold_impl_item(item)),
 959         ),
 960         ItemKind::Trait(is_auto, unsafety, generics, bounds, items) => ItemKind::Trait(
 961             is_auto,
 962             unsafety,
 963             folder.fold_generics(generics),
 964             folder.fold_bounds(bounds),
 965             items.move_flat_map(|item| folder.fold_trait_item(item)),
 966         ),
 967         ItemKind::TraitAlias(generics, bounds) => ItemKind::TraitAlias(
 968             folder.fold_generics(generics),
 969             folder.fold_bounds(bounds)),
 970         ItemKind::Mac(m) => ItemKind::Mac(folder.fold_mac(m)),
 971         ItemKind::MacroDef(def) => ItemKind::MacroDef(folder.fold_macro_def(def)),
 972     }
 973 }
 974
 975 pub fn noop_fold_trait_item<T: Folder>(i: TraitItem, folder: &mut T) -> SmallVec<[TraitItem; 1]> {
 976     smallvec![TraitItem {
 977         id: folder.new_id(i.id),
 978         ident: folder.fold_ident(i.ident),
 979         attrs: fold_attrs(i.attrs, folder),
 980         generics: folder.fold_generics(i.generics),
 981         node: match i.node {
 982             TraitItemKind::Const(ty, default) => {
 983                 TraitItemKind::Const(folder.fold_ty(ty),
 984                                default.map(|x| folder.fold_expr(x)))
 985             }
 986             TraitItemKind::Method(sig, body) => {
 987                 TraitItemKind::Method(noop_fold_method_sig(sig, folder),
 988                                 body.map(|x| folder.fold_block(x)))
 989             }
 990             TraitItemKind::Type(bounds, default) => {
 991                 TraitItemKind::Type(folder.fold_bounds(bounds),
 992                               default.map(|x| folder.fold_ty(x)))
 993             }
 994             ast::TraitItemKind::Macro(mac) => {
 995                 TraitItemKind::Macro(folder.fold_mac(mac))
 996             }
 997         },
 998         span: folder.new_span(i.span),
 999         tokens: i.tokens,
1000     }]
1001 }
1002
1003 pub fn noop_fold_impl_item<T: Folder>(i: ImplItem, folder: &mut T)-> SmallVec<[ImplItem; 1]> {
1004     smallvec![ImplItem {
1005         id: folder.new_id(i.id),
1006         vis: folder.fold_vis(i.vis),
1007         ident: folder.fold_ident(i.ident),
1008         attrs: fold_attrs(i.attrs, folder),
1009         generics: folder.fold_generics(i.generics),
1010         defaultness: i.defaultness,
1011         node: match i.node  {
1012             ast::ImplItemKind::Const(ty, expr) => {
1013                 ast::ImplItemKind::Const(folder.fold_ty(ty), folder.fold_expr(expr))
1014             }
1015             ast::ImplItemKind::Method(sig, body) => {
1016                 ast::ImplItemKind::Method(noop_fold_method_sig(sig, folder),
1017                                folder.fold_block(body))
1018             }
1019             ast::ImplItemKind::Type(ty) => ast::ImplItemKind::Type(folder.fold_ty(ty)),
1020             ast::ImplItemKind::Existential(bounds) => {
1021                 ast::ImplItemKind::Existential(folder.fold_bounds(bounds))
1022             },
1023             ast::ImplItemKind::Macro(mac) => ast::ImplItemKind::Macro(folder.fold_mac(mac))
1024         },
1025         span: folder.new_span(i.span),
1026         tokens: i.tokens,
1027     }]
1028 }
1029
1030 pub fn noop_fold_fn_header<T: Folder>(mut header: FnHeader, folder: &mut T) -> FnHeader {
1031     header.asyncness = folder.fold_asyncness(header.asyncness);
1032     header
1033 }
1034
1035 pub fn noop_fold_mod<T: Folder>(Mod {inner, items, inline}: Mod, folder: &mut T) -> Mod {
1036     Mod {
1037         inner: folder.new_span(inner),
1038         items: items.move_flat_map(|x| folder.fold_item(x)),
1039         inline: inline,
1040     }
1041 }
1042
1043 pub fn noop_fold_crate<T: Folder>(Crate {module, attrs, span}: Crate,
1044                                   folder: &mut T) -> Crate {
1045     let mut items = folder.fold_item(P(ast::Item {
1046         ident: keywords::Invalid.ident(),
1047         attrs,
1048         id: ast::DUMMY_NODE_ID,
1049         vis: respan(span.shrink_to_lo(), ast::VisibilityKind::Public),
1050         span,
1051         node: ast::ItemKind::Mod(module),
1052         tokens: None,
1053     })).into_iter();
1054
1055     let (module, attrs, span) = match items.next() {
1056         Some(item) => {
1057             assert!(items.next().is_none(),
1058                     "a crate cannot expand to more than one item");
1059             item.and_then(|ast::Item { attrs, span, node, .. }| {
1060                 match node {
1061                     ast::ItemKind::Mod(m) => (m, attrs, span),
1062                     _ => panic!("fold converted a module to not a module"),
1063                 }
1064             })
1065         }
1066         None => (ast::Mod {
1067             inner: span,
1068             items: vec![],
1069             inline: true,
1070         }, vec![], span)
1071     };
1072
1073     Crate {
1074         module,
1075         attrs,
1076         span,
1077     }
1078 }
1079
1080 // fold one item into possibly many items
1081 pub fn noop_fold_item<T: Folder>(i: P<Item>, folder: &mut T) -> SmallVec<[P<Item>; 1]> {
1082     smallvec![i.map(|i| folder.fold_item_simple(i))]
1083 }
1084
1085 // fold one item into exactly one item
1086 pub fn noop_fold_item_simple<T: Folder>(Item {id, ident, attrs, node, vis, span, tokens}: Item,
1087                                         folder: &mut T) -> Item {
1088     Item {
1089         id: folder.new_id(id),
1090         vis: folder.fold_vis(vis),
1091         ident: folder.fold_ident(ident),
1092         attrs: fold_attrs(attrs, folder),
1093         node: folder.fold_item_kind(node),
1094         span: folder.new_span(span),
1095
1096         // FIXME: if this is replaced with a call to `folder.fold_tts` it causes
1097         //        an ICE during resolve... odd!
1098         tokens,
1099     }
1100 }
1101
1102 pub fn noop_fold_foreign_item<T: Folder>(ni: ForeignItem, folder: &mut T)
1103     -> SmallVec<[ForeignItem; 1]>
1104 {
1105     smallvec![folder.fold_foreign_item_simple(ni)]
1106 }
1107
1108 pub fn noop_fold_foreign_item_simple<T: Folder>(ni: ForeignItem, folder: &mut T) -> ForeignItem {
1109     ForeignItem {
1110         id: folder.new_id(ni.id),
1111         vis: folder.fold_vis(ni.vis),
1112         ident: folder.fold_ident(ni.ident),
1113         attrs: fold_attrs(ni.attrs, folder),
1114         node: match ni.node {
1115             ForeignItemKind::Fn(fdec, generics) => {
1116                 ForeignItemKind::Fn(folder.fold_fn_decl(fdec), folder.fold_generics(generics))
1117             }
1118             ForeignItemKind::Static(t, m) => {
1119                 ForeignItemKind::Static(folder.fold_ty(t), m)
1120             }
1121             ForeignItemKind::Ty => ForeignItemKind::Ty,
1122             ForeignItemKind::Macro(mac) => ForeignItemKind::Macro(folder.fold_mac(mac)),
1123         },
1124         span: folder.new_span(ni.span)
1125     }
1126 }
1127
1128 pub fn noop_fold_method_sig<T: Folder>(sig: MethodSig, folder: &mut T) -> MethodSig {
1129     MethodSig {
1130         header: folder.fold_fn_header(sig.header),
1131         decl: folder.fold_fn_decl(sig.decl)
1132     }
1133 }
1134
1135 pub fn noop_fold_pat<T: Folder>(p: P<Pat>, folder: &mut T) -> P<Pat> {
1136     p.map(|Pat {id, node, span}| Pat {
1137         id: folder.new_id(id),
1138         node: match node {
1139             PatKind::Wild => PatKind::Wild,
1140             PatKind::Ident(binding_mode, ident, sub) => {
1141                 PatKind::Ident(binding_mode,
1142                                folder.fold_ident(ident),
1143                                sub.map(|x| folder.fold_pat(x)))
1144             }
1145             PatKind::Lit(e) => PatKind::Lit(folder.fold_expr(e)),
1146             PatKind::TupleStruct(pth, pats, ddpos) => {
1147                 PatKind::TupleStruct(folder.fold_path(pth),
1148                         pats.move_map(|x| folder.fold_pat(x)), ddpos)
1149             }
1150             PatKind::Path(qself, pth) => {
1151                 let (qself, pth) = folder.fold_qpath(qself, pth);
1152                 PatKind::Path(qself, pth)
1153             }
1154             PatKind::Struct(pth, fields, etc) => {
1155                 let pth = folder.fold_path(pth);
1156                 let fs = fields.move_map(|f| {
1157                     Spanned { span: folder.new_span(f.span),
1158                               node: ast::FieldPat {
1159                                   ident: folder.fold_ident(f.node.ident),
1160                                   pat: folder.fold_pat(f.node.pat),
1161                                   is_shorthand: f.node.is_shorthand,
1162                                   attrs: fold_attrs(f.node.attrs.into(), folder).into()
1163                               }}
1164                 });
1165                 PatKind::Struct(pth, fs, etc)
1166             }
1167             PatKind::Tuple(elts, ddpos) => {
1168                 PatKind::Tuple(elts.move_map(|x| folder.fold_pat(x)), ddpos)
1169             }
1170             PatKind::Box(inner) => PatKind::Box(folder.fold_pat(inner)),
1171             PatKind::Ref(inner, mutbl) => PatKind::Ref(folder.fold_pat(inner), mutbl),
1172             PatKind::Range(e1, e2, Spanned { span, node: end }) => {
1173                 PatKind::Range(folder.fold_expr(e1),
1174                                folder.fold_expr(e2),
1175                                Spanned { span, node: folder.fold_range_end(end) })
1176             },
1177             PatKind::Slice(before, slice, after) => {
1178                 PatKind::Slice(before.move_map(|x| folder.fold_pat(x)),
1179                        slice.map(|x| folder.fold_pat(x)),
1180                        after.move_map(|x| folder.fold_pat(x)))
1181             }
1182             PatKind::Paren(inner) => PatKind::Paren(folder.fold_pat(inner)),
1183             PatKind::Mac(mac) => PatKind::Mac(folder.fold_mac(mac))
1184         },
1185         span: folder.new_span(span)
1186     })
1187 }
1188
1189 pub fn noop_fold_range_end<T: Folder>(end: RangeEnd, _folder: &mut T) -> RangeEnd {
1190     end
1191 }
1192
1193 pub fn noop_fold_anon_const<T: Folder>(constant: AnonConst, folder: &mut T) -> AnonConst {
1194     let AnonConst {id, value} = constant;
1195     AnonConst {
1196         id: folder.new_id(id),
1197         value: folder.fold_expr(value),
1198     }
1199 }
1200
1201 pub fn noop_fold_expr<T: Folder>(Expr {id, node, span, attrs}: Expr, folder: &mut T) -> Expr {
1202     Expr {
1203         node: match node {
1204             ExprKind::Box(e) => {
1205                 ExprKind::Box(folder.fold_expr(e))
1206             }
1207             ExprKind::ObsoleteInPlace(a, b) => {
1208                 ExprKind::ObsoleteInPlace(folder.fold_expr(a), folder.fold_expr(b))
1209             }
1210             ExprKind::Array(exprs) => {
1211                 ExprKind::Array(folder.fold_exprs(exprs))
1212             }
1213             ExprKind::Repeat(expr, count) => {
1214                 ExprKind::Repeat(folder.fold_expr(expr), folder.fold_anon_const(count))
1215             }
1216             ExprKind::Tup(exprs) => ExprKind::Tup(folder.fold_exprs(exprs)),
1217             ExprKind::Call(f, args) => {
1218                 ExprKind::Call(folder.fold_expr(f),
1219                          folder.fold_exprs(args))
1220             }
1221             ExprKind::MethodCall(seg, args) => {
1222                 ExprKind::MethodCall(
1223                     PathSegment {
1224                         ident: folder.fold_ident(seg.ident),
1225                         id: folder.new_id(seg.id),
1226                         args: seg.args.map(|args| {
1227                             args.map(|args| folder.fold_generic_args(args))
1228                         }),
1229                     },
1230                     folder.fold_exprs(args))
1231             }
1232             ExprKind::Binary(binop, lhs, rhs) => {
1233                 ExprKind::Binary(binop,
1234                         folder.fold_expr(lhs),
1235                         folder.fold_expr(rhs))
1236             }
1237             ExprKind::Unary(binop, ohs) => {
1238                 ExprKind::Unary(binop, folder.fold_expr(ohs))
1239             }
1240             ExprKind::Lit(l) => ExprKind::Lit(l),
1241             ExprKind::Cast(expr, ty) => {
1242                 ExprKind::Cast(folder.fold_expr(expr), folder.fold_ty(ty))
1243             }
1244             ExprKind::Type(expr, ty) => {
1245                 ExprKind::Type(folder.fold_expr(expr), folder.fold_ty(ty))
1246             }
1247             ExprKind::AddrOf(m, ohs) => ExprKind::AddrOf(m, folder.fold_expr(ohs)),
1248             ExprKind::If(cond, tr, fl) => {
1249                 ExprKind::If(folder.fold_expr(cond),
1250                        folder.fold_block(tr),
1251                        fl.map(|x| folder.fold_expr(x)))
1252             }
1253             ExprKind::IfLet(pats, expr, tr, fl) => {
1254                 ExprKind::IfLet(pats.move_map(|pat| folder.fold_pat(pat)),
1255                           folder.fold_expr(expr),
1256                           folder.fold_block(tr),
1257                           fl.map(|x| folder.fold_expr(x)))
1258             }
1259             ExprKind::While(cond, body, opt_label) => {
1260                 ExprKind::While(folder.fold_expr(cond),
1261                           folder.fold_block(body),
1262                           opt_label.map(|label| folder.fold_label(label)))
1263             }
1264             ExprKind::WhileLet(pats, expr, body, opt_label) => {
1265                 ExprKind::WhileLet(pats.move_map(|pat| folder.fold_pat(pat)),
1266                              folder.fold_expr(expr),
1267                              folder.fold_block(body),
1268                              opt_label.map(|label| folder.fold_label(label)))
1269             }
1270             ExprKind::ForLoop(pat, iter, body, opt_label) => {
1271                 ExprKind::ForLoop(folder.fold_pat(pat),
1272                             folder.fold_expr(iter),
1273                             folder.fold_block(body),
1274                             opt_label.map(|label| folder.fold_label(label)))
1275             }
1276             ExprKind::Loop(body, opt_label) => {
1277                 ExprKind::Loop(folder.fold_block(body),
1278                                opt_label.map(|label| folder.fold_label(label)))
1279             }
1280             ExprKind::Match(expr, arms) => {
1281                 ExprKind::Match(folder.fold_expr(expr),
1282                           arms.move_map(|x| folder.fold_arm(x)))
1283             }
1284             ExprKind::Closure(capture_clause, asyncness, movability, decl, body, span) => {
1285                 ExprKind::Closure(capture_clause,
1286                                   folder.fold_asyncness(asyncness),
1287                                   movability,
1288                                   folder.fold_fn_decl(decl),
1289                                   folder.fold_expr(body),
1290                                   folder.new_span(span))
1291             }
1292             ExprKind::Block(blk, opt_label) => {
1293                 ExprKind::Block(folder.fold_block(blk),
1294                                 opt_label.map(|label| folder.fold_label(label)))
1295             }
1296             ExprKind::Async(capture_clause, node_id, body) => {
1297                 ExprKind::Async(
1298                     capture_clause,
1299                     folder.new_id(node_id),
1300                     folder.fold_block(body),
1301                 )
1302             }
1303             ExprKind::Assign(el, er) => {
1304                 ExprKind::Assign(folder.fold_expr(el), folder.fold_expr(er))
1305             }
1306             ExprKind::AssignOp(op, el, er) => {
1307                 ExprKind::AssignOp(op,
1308                             folder.fold_expr(el),
1309                             folder.fold_expr(er))
1310             }
1311             ExprKind::Field(el, ident) => {
1312                 ExprKind::Field(folder.fold_expr(el), folder.fold_ident(ident))
1313             }
1314             ExprKind::Index(el, er) => {
1315                 ExprKind::Index(folder.fold_expr(el), folder.fold_expr(er))
1316             }
1317             ExprKind::Range(e1, e2, lim) => {
1318                 ExprKind::Range(e1.map(|x| folder.fold_expr(x)),
1319                                 e2.map(|x| folder.fold_expr(x)),
1320                                 lim)
1321             }
1322             ExprKind::Path(qself, path) => {
1323                 let (qself, path) = folder.fold_qpath(qself, path);
1324                 ExprKind::Path(qself, path)
1325             }
1326             ExprKind::Break(opt_label, opt_expr) => {
1327                 ExprKind::Break(opt_label.map(|label| folder.fold_label(label)),
1328                                 opt_expr.map(|e| folder.fold_expr(e)))
1329             }
1330             ExprKind::Continue(opt_label) => {
1331                 ExprKind::Continue(opt_label.map(|label| folder.fold_label(label)))
1332             }
1333             ExprKind::Ret(e) => ExprKind::Ret(e.map(|x| folder.fold_expr(x))),
1334             ExprKind::InlineAsm(asm) => ExprKind::InlineAsm(asm.map(|asm| {
1335                 InlineAsm {
1336                     inputs: asm.inputs.move_map(|(c, input)| {
1337                         (c, folder.fold_expr(input))
1338                     }),
1339                     outputs: asm.outputs.move_map(|out| {
1340                         InlineAsmOutput {
1341                             constraint: out.constraint,
1342                             expr: folder.fold_expr(out.expr),
1343                             is_rw: out.is_rw,
1344                             is_indirect: out.is_indirect,
1345                         }
1346                     }),
1347                     ..asm
1348                 }
1349             })),
1350             ExprKind::Mac(mac) => ExprKind::Mac(folder.fold_mac(mac)),
1351             ExprKind::Struct(path, fields, maybe_expr) => {
1352                 ExprKind::Struct(folder.fold_path(path),
1353                         fields.move_map(|x| folder.fold_field(x)),
1354                         maybe_expr.map(|x| folder.fold_expr(x)))
1355             },
1356             ExprKind::Paren(ex) => {
1357                 let sub_expr = folder.fold_expr(ex);
1358                 return Expr {
1359                     // Nodes that are equal modulo `Paren` sugar no-ops should have the same ids.
1360                     id: sub_expr.id,
1361                     node: ExprKind::Paren(sub_expr),
1362                     span: folder.new_span(span),
1363                     attrs: fold_attrs(attrs.into(), folder).into(),
1364                 };
1365             }
1366             ExprKind::Yield(ex) => ExprKind::Yield(ex.map(|x| folder.fold_expr(x))),
1367             ExprKind::Try(ex) => ExprKind::Try(folder.fold_expr(ex)),
1368             ExprKind::TryBlock(body) => ExprKind::TryBlock(folder.fold_block(body)),
1369             ExprKind::Err => ExprKind::Err,
1370         },
1371         id: folder.new_id(id),
1372         span: folder.new_span(span),
1373         attrs: fold_attrs(attrs.into(), folder).into(),
1374     }
1375 }
1376
1377 pub fn noop_fold_opt_expr<T: Folder>(e: P<Expr>, folder: &mut T) -> Option<P<Expr>> {
1378     Some(folder.fold_expr(e))
1379 }
1380
1381 pub fn noop_fold_exprs<T: Folder>(es: Vec<P<Expr>>, folder: &mut T) -> Vec<P<Expr>> {
1382     es.move_flat_map(|e| folder.fold_opt_expr(e))
1383 }
1384
1385 pub fn noop_fold_stmt<T: Folder>(Stmt {node, span, id}: Stmt, folder: &mut T) -> SmallVec<[Stmt; 1]>
1386 {
1387     let id = folder.new_id(id);
1388     let span = folder.new_span(span);
1389     noop_fold_stmt_kind(node, folder).into_iter().map(|node| {
1390         Stmt { id: id, node: node, span: span }
1391     }).collect()
1392 }
1393
1394 pub fn noop_fold_stmt_kind<T: Folder>(node: StmtKind, folder: &mut T) -> SmallVec<[StmtKind; 1]> {
1395     match node {
1396         StmtKind::Local(local) => smallvec![StmtKind::Local(folder.fold_local(local))],
1397         StmtKind::Item(item) => folder.fold_item(item).into_iter().map(StmtKind::Item).collect(),
1398         StmtKind::Expr(expr) => {
1399             folder.fold_opt_expr(expr).into_iter().map(StmtKind::Expr).collect()
1400         }
1401         StmtKind::Semi(expr) => {
1402             folder.fold_opt_expr(expr).into_iter().map(StmtKind::Semi).collect()
1403         }
1404         StmtKind::Mac(mac) => smallvec![StmtKind::Mac(mac.map(|(mac, semi, attrs)| {
1405             (folder.fold_mac(mac), semi, fold_attrs(attrs.into(), folder).into())
1406         }))],
1407     }
1408 }
1409
1410 pub fn noop_fold_vis<T: Folder>(vis: Visibility, folder: &mut T) -> Visibility {
1411     match vis.node {
1412         VisibilityKind::Restricted { path, id } => {
1413             respan(vis.span, VisibilityKind::Restricted {
1414                 path: path.map(|path| folder.fold_path(path)),
1415                 id: folder.new_id(id),
1416             })
1417         }
1418         _ => vis,
1419     }
1420 }
1421
1422 #[cfg(test)]
1423 mod tests {
1424     use std::io;
1425     use ast::{self, Ident};
1426     use util::parser_testing::{string_to_crate, matches_codepattern};
1427     use print::pprust;
1428     use fold;
1429     use with_globals;
1430     use super::*;
1431
1432     // this version doesn't care about getting comments or docstrings in.
1433     fn fake_print_crate(s: &mut pprust::State,
1434                         krate: &ast::Crate) -> io::Result<()> {
1435         s.print_mod(&krate.module, &krate.attrs)
1436     }
1437
1438     // change every identifier to "zz"
1439     struct ToZzIdentFolder;
1440
1441     impl Folder for ToZzIdentFolder {
1442         fn fold_ident(&mut self, _: ast::Ident) -> ast::Ident {
1443             Ident::from_str("zz")
1444         }
1445         fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
1446             fold::noop_fold_mac(mac, self)
1447         }
1448     }
1449
1450     // maybe add to expand.rs...
1451     macro_rules! assert_pred {
1452         ($pred:expr, $predname:expr, $a:expr , $b:expr) => (
1453             {
1454                 let pred_val = $pred;
1455                 let a_val = $a;
1456                 let b_val = $b;
1457                 if !(pred_val(&a_val, &b_val)) {
1458                     panic!("expected args satisfying {}, got {} and {}",
1459                           $predname, a_val, b_val);
1460                 }
1461             }
1462         )
1463     }
1464
1465     // make sure idents get transformed everywhere
1466     #[test] fn ident_transformation () {
1467         with_globals(|| {
1468             let mut zz_fold = ToZzIdentFolder;
1469             let ast = string_to_crate(
1470                 "#[a] mod b {fn c (d : e, f : g) {h!(i,j,k);l;m}}".to_string());
1471             let folded_crate = zz_fold.fold_crate(ast);
1472             assert_pred!(
1473                 matches_codepattern,
1474                 "matches_codepattern",
1475                 pprust::to_string(|s| fake_print_crate(s, &folded_crate)),
1476                 "#[zz]mod zz{fn zz(zz:zz,zz:zz){zz!(zz,zz,zz);zz;zz}}".to_string());
1477         })
1478     }
1479
1480     // even inside macro defs....
1481     #[test] fn ident_transformation_in_defs () {
1482         with_globals(|| {
1483             let mut zz_fold = ToZzIdentFolder;
1484             let ast = string_to_crate(
1485                 "macro_rules! a {(b $c:expr $(d $e:token)f+ => \
1486                 (g $(d $d $e)+))} ".to_string());
1487             let folded_crate = zz_fold.fold_crate(ast);
1488             assert_pred!(
1489                 matches_codepattern,
1490                 "matches_codepattern",
1491                 pprust::to_string(|s| fake_print_crate(s, &folded_crate)),
1492                 "macro_rules! zz((zz$zz:zz$(zz $zz:zz)zz+=>(zz$(zz$zz$zz)+)));".to_string());
1493         })
1494     }
1495 }