src/libsyntax/fold.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! A Folder represents an AST->AST fold; it accepts an AST piece,
  12 //! and returns a piece of the same type. So, for instance, macro
  13 //! expansion is a Folder that walks over an AST and produces another
  14 //! AST.
  15 //!
  16 //! Note: using a Folder (other than the MacroExpander Folder) on
  17 //! an AST before macro expansion is probably a bad idea. For instance,
  18 //! a folder renaming item names in a module will miss all of those
  19 //! that are created by the expansion of a macro.
  20
  21 use ast::*;
  22 use ast;
  23 use syntax_pos::Span;
  24 use codemap::{Spanned, respan};
  25 use parse::token;
  26 use ptr::P;
  27 use symbol::keywords;
  28 use tokenstream::*;
  29 use util::small_vector::SmallVector;
  30 use util::move_map::MoveMap;
  31
  32 use std::rc::Rc;
  33
  34 pub trait Folder : Sized {
  35     // Any additions to this trait should happen in form
  36     // of a call to a public `noop_*` function that only calls
  37     // out to the folder again, not other `noop_*` functions.
  38     //
  39     // This is a necessary API workaround to the problem of not
  40     // being able to call out to the super default method
  41     // in an overridden default method.
  42
  43     fn fold_crate(&mut self, c: Crate) -> Crate {
  44         noop_fold_crate(c, self)
  45     }
  46
  47     fn fold_meta_items(&mut self, meta_items: Vec<MetaItem>) -> Vec<MetaItem> {
  48         noop_fold_meta_items(meta_items, self)
  49     }
  50
  51     fn fold_meta_list_item(&mut self, list_item: NestedMetaItem) -> NestedMetaItem {
  52         noop_fold_meta_list_item(list_item, self)
  53     }
  54
  55     fn fold_meta_item(&mut self, meta_item: MetaItem) -> MetaItem {
  56         noop_fold_meta_item(meta_item, self)
  57     }
  58
  59     fn fold_view_path(&mut self, view_path: P<ViewPath>) -> P<ViewPath> {
  60         noop_fold_view_path(view_path, self)
  61     }
  62
  63     fn fold_foreign_item(&mut self, ni: ForeignItem) -> ForeignItem {
  64         noop_fold_foreign_item(ni, self)
  65     }
  66
  67     fn fold_item(&mut self, i: P<Item>) -> SmallVector<P<Item>> {
  68         noop_fold_item(i, self)
  69     }
  70
  71     fn fold_item_simple(&mut self, i: Item) -> Item {
  72         noop_fold_item_simple(i, self)
  73     }
  74
  75     fn fold_struct_field(&mut self, sf: StructField) -> StructField {
  76         noop_fold_struct_field(sf, self)
  77     }
  78
  79     fn fold_item_kind(&mut self, i: ItemKind) -> ItemKind {
  80         noop_fold_item_kind(i, self)
  81     }
  82
  83     fn fold_trait_item(&mut self, i: TraitItem) -> SmallVector<TraitItem> {
  84         noop_fold_trait_item(i, self)
  85     }
  86
  87     fn fold_impl_item(&mut self, i: ImplItem) -> SmallVector<ImplItem> {
  88         noop_fold_impl_item(i, self)
  89     }
  90
  91     fn fold_fn_decl(&mut self, d: P<FnDecl>) -> P<FnDecl> {
  92         noop_fold_fn_decl(d, self)
  93     }
  94
  95     fn fold_block(&mut self, b: P<Block>) -> P<Block> {
  96         noop_fold_block(b, self)
  97     }
  98
  99     fn fold_stmt(&mut self, s: Stmt) -> SmallVector<Stmt> {
 100         noop_fold_stmt(s, self)
 101     }
 102
 103     fn fold_arm(&mut self, a: Arm) -> Arm {
 104         noop_fold_arm(a, self)
 105     }
 106
 107     fn fold_pat(&mut self, p: P<Pat>) -> P<Pat> {
 108         noop_fold_pat(p, self)
 109     }
 110
 111     fn fold_expr(&mut self, e: P<Expr>) -> P<Expr> {
 112         e.map(|e| noop_fold_expr(e, self))
 113     }
 114
 115     fn fold_range_end(&mut self, re: RangeEnd) -> RangeEnd {
 116         noop_fold_range_end(re, self)
 117     }
 118
 119     fn fold_opt_expr(&mut self, e: P<Expr>) -> Option<P<Expr>> {
 120         noop_fold_opt_expr(e, self)
 121     }
 122
 123     fn fold_exprs(&mut self, es: Vec<P<Expr>>) -> Vec<P<Expr>> {
 124         noop_fold_exprs(es, self)
 125     }
 126
 127     fn fold_ty(&mut self, t: P<Ty>) -> P<Ty> {
 128         noop_fold_ty(t, self)
 129     }
 130
 131     fn fold_ty_binding(&mut self, t: TypeBinding) -> TypeBinding {
 132         noop_fold_ty_binding(t, self)
 133     }
 134
 135     fn fold_mod(&mut self, m: Mod) -> Mod {
 136         noop_fold_mod(m, self)
 137     }
 138
 139     fn fold_foreign_mod(&mut self, nm: ForeignMod) -> ForeignMod {
 140         noop_fold_foreign_mod(nm, self)
 141     }
 142
 143     fn fold_global_asm(&mut self, ga: P<GlobalAsm>) -> P<GlobalAsm> {
 144         noop_fold_global_asm(ga, self)
 145     }
 146
 147     fn fold_variant(&mut self, v: Variant) -> Variant {
 148         noop_fold_variant(v, self)
 149     }
 150
 151     fn fold_ident(&mut self, i: Ident) -> Ident {
 152         noop_fold_ident(i, self)
 153     }
 154
 155     fn fold_usize(&mut self, i: usize) -> usize {
 156         noop_fold_usize(i, self)
 157     }
 158
 159     fn fold_path(&mut self, p: Path) -> Path {
 160         noop_fold_path(p, self)
 161     }
 162
 163     fn fold_path_parameters(&mut self, p: PathParameters) -> PathParameters {
 164         noop_fold_path_parameters(p, self)
 165     }
 166
 167     fn fold_angle_bracketed_parameter_data(&mut self, p: AngleBracketedParameterData)
 168                                            -> AngleBracketedParameterData
 169     {
 170         noop_fold_angle_bracketed_parameter_data(p, self)
 171     }
 172
 173     fn fold_parenthesized_parameter_data(&mut self, p: ParenthesizedParameterData)
 174                                          -> ParenthesizedParameterData
 175     {
 176         noop_fold_parenthesized_parameter_data(p, self)
 177     }
 178
 179     fn fold_local(&mut self, l: P<Local>) -> P<Local> {
 180         noop_fold_local(l, self)
 181     }
 182
 183     fn fold_mac(&mut self, _mac: Mac) -> Mac {
 184         panic!("fold_mac disabled by default");
 185         // NB: see note about macros above.
 186         // if you really want a folder that
 187         // works on macros, use this
 188         // definition in your trait impl:
 189         // fold::noop_fold_mac(_mac, self)
 190     }
 191
 192     fn fold_macro_def(&mut self, def: MacroDef) -> MacroDef {
 193         noop_fold_macro_def(def, self)
 194     }
 195
 196     fn fold_lifetime(&mut self, l: Lifetime) -> Lifetime {
 197         noop_fold_lifetime(l, self)
 198     }
 199
 200     fn fold_lifetime_def(&mut self, l: LifetimeDef) -> LifetimeDef {
 201         noop_fold_lifetime_def(l, self)
 202     }
 203
 204     fn fold_attribute(&mut self, at: Attribute) -> Option<Attribute> {
 205         noop_fold_attribute(at, self)
 206     }
 207
 208     fn fold_arg(&mut self, a: Arg) -> Arg {
 209         noop_fold_arg(a, self)
 210     }
 211
 212     fn fold_generics(&mut self, generics: Generics) -> Generics {
 213         noop_fold_generics(generics, self)
 214     }
 215
 216     fn fold_trait_ref(&mut self, p: TraitRef) -> TraitRef {
 217         noop_fold_trait_ref(p, self)
 218     }
 219
 220     fn fold_poly_trait_ref(&mut self, p: PolyTraitRef) -> PolyTraitRef {
 221         noop_fold_poly_trait_ref(p, self)
 222     }
 223
 224     fn fold_variant_data(&mut self, vdata: VariantData) -> VariantData {
 225         noop_fold_variant_data(vdata, self)
 226     }
 227
 228     fn fold_lifetimes(&mut self, lts: Vec<Lifetime>) -> Vec<Lifetime> {
 229         noop_fold_lifetimes(lts, self)
 230     }
 231
 232     fn fold_lifetime_defs(&mut self, lts: Vec<LifetimeDef>) -> Vec<LifetimeDef> {
 233         noop_fold_lifetime_defs(lts, self)
 234     }
 235
 236     fn fold_ty_param(&mut self, tp: TyParam) -> TyParam {
 237         noop_fold_ty_param(tp, self)
 238     }
 239
 240     fn fold_ty_params(&mut self, tps: Vec<TyParam>) -> Vec<TyParam> {
 241         noop_fold_ty_params(tps, self)
 242     }
 243
 244     fn fold_tt(&mut self, tt: TokenTree) -> TokenTree {
 245         noop_fold_tt(tt, self)
 246     }
 247
 248     fn fold_tts(&mut self, tts: TokenStream) -> TokenStream {
 249         noop_fold_tts(tts, self)
 250     }
 251
 252     fn fold_token(&mut self, t: token::Token) -> token::Token {
 253         noop_fold_token(t, self)
 254     }
 255
 256     fn fold_interpolated(&mut self, nt: token::Nonterminal) -> token::Nonterminal {
 257         noop_fold_interpolated(nt, self)
 258     }
 259
 260     fn fold_opt_lifetime(&mut self, o_lt: Option<Lifetime>) -> Option<Lifetime> {
 261         noop_fold_opt_lifetime(o_lt, self)
 262     }
 263
 264     fn fold_opt_bounds(&mut self, b: Option<TyParamBounds>)
 265                        -> Option<TyParamBounds> {
 266         noop_fold_opt_bounds(b, self)
 267     }
 268
 269     fn fold_bounds(&mut self, b: TyParamBounds)
 270                        -> TyParamBounds {
 271         noop_fold_bounds(b, self)
 272     }
 273
 274     fn fold_ty_param_bound(&mut self, tpb: TyParamBound) -> TyParamBound {
 275         noop_fold_ty_param_bound(tpb, self)
 276     }
 277
 278     fn fold_mt(&mut self, mt: MutTy) -> MutTy {
 279         noop_fold_mt(mt, self)
 280     }
 281
 282     fn fold_field(&mut self, field: Field) -> Field {
 283         noop_fold_field(field, self)
 284     }
 285
 286     fn fold_where_clause(&mut self, where_clause: WhereClause)
 287                          -> WhereClause {
 288         noop_fold_where_clause(where_clause, self)
 289     }
 290
 291     fn fold_where_predicate(&mut self, where_predicate: WherePredicate)
 292                             -> WherePredicate {
 293         noop_fold_where_predicate(where_predicate, self)
 294     }
 295
 296     fn fold_vis(&mut self, vis: Visibility) -> Visibility {
 297         noop_fold_vis(vis, self)
 298     }
 299
 300     fn new_id(&mut self, i: NodeId) -> NodeId {
 301         i
 302     }
 303
 304     fn new_span(&mut self, sp: Span) -> Span {
 305         sp
 306     }
 307 }
 308
 309 pub fn noop_fold_meta_items<T: Folder>(meta_items: Vec<MetaItem>, fld: &mut T) -> Vec<MetaItem> {
 310     meta_items.move_map(|x| fld.fold_meta_item(x))
 311 }
 312
 313 pub fn noop_fold_view_path<T: Folder>(view_path: P<ViewPath>, fld: &mut T) -> P<ViewPath> {
 314     view_path.map(|Spanned {node, span}| Spanned {
 315         node: match node {
 316             ViewPathSimple(ident, path) => {
 317                 ViewPathSimple(fld.fold_ident(ident), fld.fold_path(path))
 318             }
 319             ViewPathGlob(path) => {
 320                 ViewPathGlob(fld.fold_path(path))
 321             }
 322             ViewPathList(path, path_list_idents) => {
 323                 let path = fld.fold_path(path);
 324                 let path_list_idents = path_list_idents.move_map(|path_list_ident| Spanned {
 325                     node: PathListItem_ {
 326                         id: fld.new_id(path_list_ident.node.id),
 327                         rename: path_list_ident.node.rename.map(|ident| fld.fold_ident(ident)),
 328                         name: fld.fold_ident(path_list_ident.node.name),
 329                     },
 330                     span: fld.new_span(path_list_ident.span)
 331                 });
 332                 ViewPathList(path, path_list_idents)
 333             }
 334         },
 335         span: fld.new_span(span)
 336     })
 337 }
 338
 339 pub fn fold_attrs<T: Folder>(attrs: Vec<Attribute>, fld: &mut T) -> Vec<Attribute> {
 340     attrs.move_flat_map(|x| fld.fold_attribute(x))
 341 }
 342
 343 pub fn fold_thin_attrs<T: Folder>(attrs: ThinVec<Attribute>, fld: &mut T) -> ThinVec<Attribute> {
 344     fold_attrs(attrs.into(), fld).into()
 345 }
 346
 347 pub fn noop_fold_arm<T: Folder>(Arm {attrs, pats, guard, body}: Arm, fld: &mut T) -> Arm {
 348     Arm {
 349         attrs: fold_attrs(attrs, fld),
 350         pats: pats.move_map(|x| fld.fold_pat(x)),
 351         guard: guard.map(|x| fld.fold_expr(x)),
 352         body: fld.fold_expr(body),
 353     }
 354 }
 355
 356 pub fn noop_fold_ty_binding<T: Folder>(b: TypeBinding, fld: &mut T) -> TypeBinding {
 357     TypeBinding {
 358         id: fld.new_id(b.id),
 359         ident: fld.fold_ident(b.ident),
 360         ty: fld.fold_ty(b.ty),
 361         span: fld.new_span(b.span),
 362     }
 363 }
 364
 365 pub fn noop_fold_ty<T: Folder>(t: P<Ty>, fld: &mut T) -> P<Ty> {
 366     t.map(|Ty {id, node, span}| Ty {
 367         id: fld.new_id(id),
 368         node: match node {
 369             TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err => node,
 370             TyKind::Slice(ty) => TyKind::Slice(fld.fold_ty(ty)),
 371             TyKind::Ptr(mt) => TyKind::Ptr(fld.fold_mt(mt)),
 372             TyKind::Rptr(region, mt) => {
 373                 TyKind::Rptr(fld.fold_opt_lifetime(region), fld.fold_mt(mt))
 374             }
 375             TyKind::BareFn(f) => {
 376                 TyKind::BareFn(f.map(|BareFnTy {lifetimes, unsafety, abi, decl}| BareFnTy {
 377                     lifetimes: fld.fold_lifetime_defs(lifetimes),
 378                     unsafety: unsafety,
 379                     abi: abi,
 380                     decl: fld.fold_fn_decl(decl)
 381                 }))
 382             }
 383             TyKind::Never => node,
 384             TyKind::Tup(tys) => TyKind::Tup(tys.move_map(|ty| fld.fold_ty(ty))),
 385             TyKind::Paren(ty) => TyKind::Paren(fld.fold_ty(ty)),
 386             TyKind::Path(qself, path) => {
 387                 let qself = qself.map(|QSelf { ty, position }| {
 388                     QSelf {
 389                         ty: fld.fold_ty(ty),
 390                         position: position
 391                     }
 392                 });
 393                 TyKind::Path(qself, fld.fold_path(path))
 394             }
 395             TyKind::Array(ty, e) => {
 396                 TyKind::Array(fld.fold_ty(ty), fld.fold_expr(e))
 397             }
 398             TyKind::Typeof(expr) => {
 399                 TyKind::Typeof(fld.fold_expr(expr))
 400             }
 401             TyKind::TraitObject(bounds) => {
 402                 TyKind::TraitObject(bounds.move_map(|b| fld.fold_ty_param_bound(b)))
 403             }
 404             TyKind::ImplTrait(bounds) => {
 405                 TyKind::ImplTrait(bounds.move_map(|b| fld.fold_ty_param_bound(b)))
 406             }
 407             TyKind::Mac(mac) => {
 408                 TyKind::Mac(fld.fold_mac(mac))
 409             }
 410         },
 411         span: fld.new_span(span)
 412     })
 413 }
 414
 415 pub fn noop_fold_foreign_mod<T: Folder>(ForeignMod {abi, items}: ForeignMod,
 416                                         fld: &mut T) -> ForeignMod {
 417     ForeignMod {
 418         abi: abi,
 419         items: items.move_map(|x| fld.fold_foreign_item(x)),
 420     }
 421 }
 422
 423 pub fn noop_fold_global_asm<T: Folder>(ga: P<GlobalAsm>,
 424                                        _: &mut T) -> P<GlobalAsm> {
 425     ga
 426 }
 427
 428 pub fn noop_fold_variant<T: Folder>(v: Variant, fld: &mut T) -> Variant {
 429     Spanned {
 430         node: Variant_ {
 431             name: fld.fold_ident(v.node.name),
 432             attrs: fold_attrs(v.node.attrs, fld),
 433             data: fld.fold_variant_data(v.node.data),
 434             disr_expr: v.node.disr_expr.map(|e| fld.fold_expr(e)),
 435         },
 436         span: fld.new_span(v.span),
 437     }
 438 }
 439
 440 pub fn noop_fold_ident<T: Folder>(i: Ident, _: &mut T) -> Ident {
 441     i
 442 }
 443
 444 pub fn noop_fold_usize<T: Folder>(i: usize, _: &mut T) -> usize {
 445     i
 446 }
 447
 448 pub fn noop_fold_path<T: Folder>(Path { segments, span }: Path, fld: &mut T) -> Path {
 449     Path {
 450         segments: segments.move_map(|PathSegment {identifier, span, parameters}| PathSegment {
 451             identifier: fld.fold_ident(identifier),
 452             span: fld.new_span(span),
 453             parameters: parameters.map(|ps| ps.map(|ps| fld.fold_path_parameters(ps))),
 454         }),
 455         span: fld.new_span(span)
 456     }
 457 }
 458
 459 pub fn noop_fold_path_parameters<T: Folder>(path_parameters: PathParameters, fld: &mut T)
 460                                             -> PathParameters
 461 {
 462     match path_parameters {
 463         PathParameters::AngleBracketed(data) =>
 464             PathParameters::AngleBracketed(fld.fold_angle_bracketed_parameter_data(data)),
 465         PathParameters::Parenthesized(data) =>
 466             PathParameters::Parenthesized(fld.fold_parenthesized_parameter_data(data)),
 467     }
 468 }
 469
 470 pub fn noop_fold_angle_bracketed_parameter_data<T: Folder>(data: AngleBracketedParameterData,
 471                                                            fld: &mut T)
 472                                                            -> AngleBracketedParameterData
 473 {
 474     let AngleBracketedParameterData { lifetimes, types, bindings } = data;
 475     AngleBracketedParameterData { lifetimes: fld.fold_lifetimes(lifetimes),
 476                                   types: types.move_map(|ty| fld.fold_ty(ty)),
 477                                   bindings: bindings.move_map(|b| fld.fold_ty_binding(b)) }
 478 }
 479
 480 pub fn noop_fold_parenthesized_parameter_data<T: Folder>(data: ParenthesizedParameterData,
 481                                                          fld: &mut T)
 482                                                          -> ParenthesizedParameterData
 483 {
 484     let ParenthesizedParameterData { inputs, output, span } = data;
 485     ParenthesizedParameterData { inputs: inputs.move_map(|ty| fld.fold_ty(ty)),
 486                                  output: output.map(|ty| fld.fold_ty(ty)),
 487                                  span: fld.new_span(span) }
 488 }
 489
 490 pub fn noop_fold_local<T: Folder>(l: P<Local>, fld: &mut T) -> P<Local> {
 491     l.map(|Local {id, pat, ty, init, span, attrs}| Local {
 492         id: fld.new_id(id),
 493         pat: fld.fold_pat(pat),
 494         ty: ty.map(|t| fld.fold_ty(t)),
 495         init: init.map(|e| fld.fold_expr(e)),
 496         span: fld.new_span(span),
 497         attrs: fold_attrs(attrs.into(), fld).into(),
 498     })
 499 }
 500
 501 pub fn noop_fold_attribute<T: Folder>(attr: Attribute, fld: &mut T) -> Option<Attribute> {
 502     Some(Attribute {
 503         id: attr.id,
 504         style: attr.style,
 505         path: fld.fold_path(attr.path),
 506         tokens: fld.fold_tts(attr.tokens),
 507         is_sugared_doc: attr.is_sugared_doc,
 508         span: fld.new_span(attr.span),
 509     })
 510 }
 511
 512 pub fn noop_fold_mac<T: Folder>(Spanned {node, span}: Mac, fld: &mut T) -> Mac {
 513     Spanned {
 514         node: Mac_ {
 515             tts: fld.fold_tts(node.stream()).into(),
 516             path: fld.fold_path(node.path),
 517         },
 518         span: fld.new_span(span)
 519     }
 520 }
 521
 522 pub fn noop_fold_macro_def<T: Folder>(def: MacroDef, fld: &mut T) -> MacroDef {
 523     MacroDef {
 524         tokens: fld.fold_tts(def.tokens.into()).into(),
 525         legacy: def.legacy,
 526     }
 527 }
 528
 529 pub fn noop_fold_meta_list_item<T: Folder>(li: NestedMetaItem, fld: &mut T)
 530     -> NestedMetaItem {
 531     Spanned {
 532         node: match li.node {
 533             NestedMetaItemKind::MetaItem(mi) =>  {
 534                 NestedMetaItemKind::MetaItem(fld.fold_meta_item(mi))
 535             },
 536             NestedMetaItemKind::Literal(lit) => NestedMetaItemKind::Literal(lit)
 537         },
 538         span: fld.new_span(li.span)
 539     }
 540 }
 541
 542 pub fn noop_fold_meta_item<T: Folder>(mi: MetaItem, fld: &mut T) -> MetaItem {
 543     MetaItem {
 544         name: mi.name,
 545         node: match mi.node {
 546             MetaItemKind::Word => MetaItemKind::Word,
 547             MetaItemKind::List(mis) => {
 548                 MetaItemKind::List(mis.move_map(|e| fld.fold_meta_list_item(e)))
 549             },
 550             MetaItemKind::NameValue(s) => MetaItemKind::NameValue(s),
 551         },
 552         span: fld.new_span(mi.span)
 553     }
 554 }
 555
 556 pub fn noop_fold_arg<T: Folder>(Arg {id, pat, ty}: Arg, fld: &mut T) -> Arg {
 557     Arg {
 558         id: fld.new_id(id),
 559         pat: fld.fold_pat(pat),
 560         ty: fld.fold_ty(ty)
 561     }
 562 }
 563
 564 pub fn noop_fold_tt<T: Folder>(tt: TokenTree, fld: &mut T) -> TokenTree {
 565     match tt {
 566         TokenTree::Token(span, tok) =>
 567             TokenTree::Token(fld.new_span(span), fld.fold_token(tok)),
 568         TokenTree::Delimited(span, delimed) => TokenTree::Delimited(fld.new_span(span), Delimited {
 569             tts: fld.fold_tts(delimed.stream()).into(),
 570             delim: delimed.delim,
 571         }),
 572     }
 573 }
 574
 575 pub fn noop_fold_tts<T: Folder>(tts: TokenStream, fld: &mut T) -> TokenStream {
 576     tts.trees().map(|tt| fld.fold_tt(tt)).collect()
 577 }
 578
 579 // apply ident folder if it's an ident, apply other folds to interpolated nodes
 580 pub fn noop_fold_token<T: Folder>(t: token::Token, fld: &mut T) -> token::Token {
 581     match t {
 582         token::Ident(id) => token::Ident(fld.fold_ident(id)),
 583         token::Lifetime(id) => token::Lifetime(fld.fold_ident(id)),
 584         token::Interpolated(nt) => {
 585             let nt = match Rc::try_unwrap(nt) {
 586                 Ok(nt) => nt,
 587                 Err(nt) => (*nt).clone(),
 588             };
 589             token::Interpolated(Rc::new(fld.fold_interpolated(nt)))
 590         }
 591         token::SubstNt(ident) => token::SubstNt(fld.fold_ident(ident)),
 592         _ => t
 593     }
 594 }
 595
 596 /// apply folder to elements of interpolated nodes
 597 //
 598 // NB: this can occur only when applying a fold to partially expanded code, where
 599 // parsed pieces have gotten implanted ito *other* macro invocations. This is relevant
 600 // for macro hygiene, but possibly not elsewhere.
 601 //
 602 // One problem here occurs because the types for fold_item, fold_stmt, etc. allow the
 603 // folder to return *multiple* items; this is a problem for the nodes here, because
 604 // they insist on having exactly one piece. One solution would be to mangle the fold
 605 // trait to include one-to-many and one-to-one versions of these entry points, but that
 606 // would probably confuse a lot of people and help very few. Instead, I'm just going
 607 // to put in dynamic checks. I think the performance impact of this will be pretty much
 608 // nonexistent. The danger is that someone will apply a fold to a partially expanded
 609 // node, and will be confused by the fact that their "fold_item" or "fold_stmt" isn't
 610 // getting called on NtItem or NtStmt nodes. Hopefully they'll wind up reading this
 611 // comment, and doing something appropriate.
 612 //
 613 // BTW, design choice: I considered just changing the type of, e.g., NtItem to contain
 614 // multiple items, but decided against it when I looked at parse_item_or_view_item and
 615 // tried to figure out what I would do with multiple items there....
 616 pub fn noop_fold_interpolated<T: Folder>(nt: token::Nonterminal, fld: &mut T)
 617                                          -> token::Nonterminal {
 618     match nt {
 619         token::NtItem(item) =>
 620             token::NtItem(fld.fold_item(item)
 621                           // this is probably okay, because the only folds likely
 622                           // to peek inside interpolated nodes will be renamings/markings,
 623                           // which map single items to single items
 624                           .expect_one("expected fold to produce exactly one item")),
 625         token::NtBlock(block) => token::NtBlock(fld.fold_block(block)),
 626         token::NtStmt(stmt) =>
 627             token::NtStmt(fld.fold_stmt(stmt)
 628                           // this is probably okay, because the only folds likely
 629                           // to peek inside interpolated nodes will be renamings/markings,
 630                           // which map single items to single items
 631                           .expect_one("expected fold to produce exactly one statement")),
 632         token::NtPat(pat) => token::NtPat(fld.fold_pat(pat)),
 633         token::NtExpr(expr) => token::NtExpr(fld.fold_expr(expr)),
 634         token::NtTy(ty) => token::NtTy(fld.fold_ty(ty)),
 635         token::NtIdent(id) => token::NtIdent(Spanned::<Ident>{node: fld.fold_ident(id.node), ..id}),
 636         token::NtMeta(meta) => token::NtMeta(fld.fold_meta_item(meta)),
 637         token::NtPath(path) => token::NtPath(fld.fold_path(path)),
 638         token::NtTT(tt) => token::NtTT(fld.fold_tt(tt)),
 639         token::NtArm(arm) => token::NtArm(fld.fold_arm(arm)),
 640         token::NtImplItem(item) =>
 641             token::NtImplItem(fld.fold_impl_item(item)
 642                               .expect_one("expected fold to produce exactly one item")),
 643         token::NtTraitItem(item) =>
 644             token::NtTraitItem(fld.fold_trait_item(item)
 645                                .expect_one("expected fold to produce exactly one item")),
 646         token::NtGenerics(generics) => token::NtGenerics(fld.fold_generics(generics)),
 647         token::NtWhereClause(where_clause) =>
 648             token::NtWhereClause(fld.fold_where_clause(where_clause)),
 649         token::NtArg(arg) => token::NtArg(fld.fold_arg(arg)),
 650         token::NtVis(vis) => token::NtVis(fld.fold_vis(vis)),
 651     }
 652 }
 653
 654 pub fn noop_fold_fn_decl<T: Folder>(decl: P<FnDecl>, fld: &mut T) -> P<FnDecl> {
 655     decl.map(|FnDecl {inputs, output, variadic}| FnDecl {
 656         inputs: inputs.move_map(|x| fld.fold_arg(x)),
 657         output: match output {
 658             FunctionRetTy::Ty(ty) => FunctionRetTy::Ty(fld.fold_ty(ty)),
 659             FunctionRetTy::Default(span) => FunctionRetTy::Default(fld.new_span(span)),
 660         },
 661         variadic: variadic
 662     })
 663 }
 664
 665 pub fn noop_fold_ty_param_bound<T>(tpb: TyParamBound, fld: &mut T)
 666                                    -> TyParamBound
 667                                    where T: Folder {
 668     match tpb {
 669         TraitTyParamBound(ty, modifier) => TraitTyParamBound(fld.fold_poly_trait_ref(ty), modifier),
 670         RegionTyParamBound(lifetime) => RegionTyParamBound(fld.fold_lifetime(lifetime)),
 671     }
 672 }
 673
 674 pub fn noop_fold_ty_param<T: Folder>(tp: TyParam, fld: &mut T) -> TyParam {
 675     let TyParam {attrs, id, ident, bounds, default, span} = tp;
 676     let attrs: Vec<_> = attrs.into();
 677     TyParam {
 678         attrs: attrs.into_iter()
 679             .flat_map(|x| fld.fold_attribute(x).into_iter())
 680             .collect::<Vec<_>>()
 681             .into(),
 682         id: fld.new_id(id),
 683         ident: fld.fold_ident(ident),
 684         bounds: fld.fold_bounds(bounds),
 685         default: default.map(|x| fld.fold_ty(x)),
 686         span: fld.new_span(span),
 687     }
 688 }
 689
 690 pub fn noop_fold_ty_params<T: Folder>(tps: Vec<TyParam>, fld: &mut T) -> Vec<TyParam> {
 691     tps.move_map(|tp| fld.fold_ty_param(tp))
 692 }
 693
 694 pub fn noop_fold_lifetime<T: Folder>(l: Lifetime, fld: &mut T) -> Lifetime {
 695     Lifetime {
 696         id: fld.new_id(l.id),
 697         ident: fld.fold_ident(l.ident),
 698         span: fld.new_span(l.span)
 699     }
 700 }
 701
 702 pub fn noop_fold_lifetime_def<T: Folder>(l: LifetimeDef, fld: &mut T)
 703                                          -> LifetimeDef {
 704     let attrs: Vec<_> = l.attrs.into();
 705     LifetimeDef {
 706         attrs: attrs.into_iter()
 707             .flat_map(|x| fld.fold_attribute(x).into_iter())
 708             .collect::<Vec<_>>()
 709             .into(),
 710         lifetime: fld.fold_lifetime(l.lifetime),
 711         bounds: fld.fold_lifetimes(l.bounds),
 712     }
 713 }
 714
 715 pub fn noop_fold_lifetimes<T: Folder>(lts: Vec<Lifetime>, fld: &mut T) -> Vec<Lifetime> {
 716     lts.move_map(|l| fld.fold_lifetime(l))
 717 }
 718
 719 pub fn noop_fold_lifetime_defs<T: Folder>(lts: Vec<LifetimeDef>, fld: &mut T)
 720                                           -> Vec<LifetimeDef> {
 721     lts.move_map(|l| fld.fold_lifetime_def(l))
 722 }
 723
 724 pub fn noop_fold_opt_lifetime<T: Folder>(o_lt: Option<Lifetime>, fld: &mut T)
 725                                          -> Option<Lifetime> {
 726     o_lt.map(|lt| fld.fold_lifetime(lt))
 727 }
 728
 729 pub fn noop_fold_generics<T: Folder>(Generics {ty_params, lifetimes, where_clause, span}: Generics,
 730                                      fld: &mut T) -> Generics {
 731     Generics {
 732         ty_params: fld.fold_ty_params(ty_params),
 733         lifetimes: fld.fold_lifetime_defs(lifetimes),
 734         where_clause: fld.fold_where_clause(where_clause),
 735         span: fld.new_span(span),
 736     }
 737 }
 738
 739 pub fn noop_fold_where_clause<T: Folder>(
 740                               WhereClause {id, predicates}: WhereClause,
 741                               fld: &mut T)
 742                               -> WhereClause {
 743     WhereClause {
 744         id: fld.new_id(id),
 745         predicates: predicates.move_map(|predicate| {
 746             fld.fold_where_predicate(predicate)
 747         })
 748     }
 749 }
 750
 751 pub fn noop_fold_where_predicate<T: Folder>(
 752                                  pred: WherePredicate,
 753                                  fld: &mut T)
 754                                  -> WherePredicate {
 755     match pred {
 756         ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate{bound_lifetimes,
 757                                                                      bounded_ty,
 758                                                                      bounds,
 759                                                                      span}) => {
 760             ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
 761                 bound_lifetimes: fld.fold_lifetime_defs(bound_lifetimes),
 762                 bounded_ty: fld.fold_ty(bounded_ty),
 763                 bounds: bounds.move_map(|x| fld.fold_ty_param_bound(x)),
 764                 span: fld.new_span(span)
 765             })
 766         }
 767         ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate{lifetime,
 768                                                                        bounds,
 769                                                                        span}) => {
 770             ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
 771                 span: fld.new_span(span),
 772                 lifetime: fld.fold_lifetime(lifetime),
 773                 bounds: bounds.move_map(|bound| fld.fold_lifetime(bound))
 774             })
 775         }
 776         ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{id,
 777                                                                lhs_ty,
 778                                                                rhs_ty,
 779                                                                span}) => {
 780             ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{
 781                 id: fld.new_id(id),
 782                 lhs_ty: fld.fold_ty(lhs_ty),
 783                 rhs_ty: fld.fold_ty(rhs_ty),
 784                 span: fld.new_span(span)
 785             })
 786         }
 787     }
 788 }
 789
 790 pub fn noop_fold_variant_data<T: Folder>(vdata: VariantData, fld: &mut T) -> VariantData {
 791     match vdata {
 792         ast::VariantData::Struct(fields, id) => {
 793             ast::VariantData::Struct(fields.move_map(|f| fld.fold_struct_field(f)),
 794                                      fld.new_id(id))
 795         }
 796         ast::VariantData::Tuple(fields, id) => {
 797             ast::VariantData::Tuple(fields.move_map(|f| fld.fold_struct_field(f)),
 798                                     fld.new_id(id))
 799         }
 800         ast::VariantData::Unit(id) => ast::VariantData::Unit(fld.new_id(id))
 801     }
 802 }
 803
 804 pub fn noop_fold_trait_ref<T: Folder>(p: TraitRef, fld: &mut T) -> TraitRef {
 805     let id = fld.new_id(p.ref_id);
 806     let TraitRef {
 807         path,
 808         ref_id: _,
 809     } = p;
 810     ast::TraitRef {
 811         path: fld.fold_path(path),
 812         ref_id: id,
 813     }
 814 }
 815
 816 pub fn noop_fold_poly_trait_ref<T: Folder>(p: PolyTraitRef, fld: &mut T) -> PolyTraitRef {
 817     ast::PolyTraitRef {
 818         bound_lifetimes: fld.fold_lifetime_defs(p.bound_lifetimes),
 819         trait_ref: fld.fold_trait_ref(p.trait_ref),
 820         span: fld.new_span(p.span),
 821     }
 822 }
 823
 824 pub fn noop_fold_struct_field<T: Folder>(f: StructField, fld: &mut T) -> StructField {
 825     StructField {
 826         span: fld.new_span(f.span),
 827         id: fld.new_id(f.id),
 828         ident: f.ident.map(|ident| fld.fold_ident(ident)),
 829         vis: fld.fold_vis(f.vis),
 830         ty: fld.fold_ty(f.ty),
 831         attrs: fold_attrs(f.attrs, fld),
 832     }
 833 }
 834
 835 pub fn noop_fold_field<T: Folder>(f: Field, folder: &mut T) -> Field {
 836     Field {
 837         ident: respan(f.ident.span, folder.fold_ident(f.ident.node)),
 838         expr: folder.fold_expr(f.expr),
 839         span: folder.new_span(f.span),
 840         is_shorthand: f.is_shorthand,
 841         attrs: fold_thin_attrs(f.attrs, folder),
 842     }
 843 }
 844
 845 pub fn noop_fold_mt<T: Folder>(MutTy {ty, mutbl}: MutTy, folder: &mut T) -> MutTy {
 846     MutTy {
 847         ty: folder.fold_ty(ty),
 848         mutbl: mutbl,
 849     }
 850 }
 851
 852 pub fn noop_fold_opt_bounds<T: Folder>(b: Option<TyParamBounds>, folder: &mut T)
 853                                        -> Option<TyParamBounds> {
 854     b.map(|bounds| folder.fold_bounds(bounds))
 855 }
 856
 857 fn noop_fold_bounds<T: Folder>(bounds: TyParamBounds, folder: &mut T)
 858                           -> TyParamBounds {
 859     bounds.move_map(|bound| folder.fold_ty_param_bound(bound))
 860 }
 861
 862 pub fn noop_fold_block<T: Folder>(b: P<Block>, folder: &mut T) -> P<Block> {
 863     b.map(|Block {id, stmts, rules, span}| Block {
 864         id: folder.new_id(id),
 865         stmts: stmts.move_flat_map(|s| folder.fold_stmt(s).into_iter()),
 866         rules: rules,
 867         span: folder.new_span(span),
 868     })
 869 }
 870
 871 pub fn noop_fold_item_kind<T: Folder>(i: ItemKind, folder: &mut T) -> ItemKind {
 872     match i {
 873         ItemKind::ExternCrate(string) => ItemKind::ExternCrate(string),
 874         ItemKind::Use(view_path) => {
 875             ItemKind::Use(folder.fold_view_path(view_path))
 876         }
 877         ItemKind::Static(t, m, e) => {
 878             ItemKind::Static(folder.fold_ty(t), m, folder.fold_expr(e))
 879         }
 880         ItemKind::Const(t, e) => {
 881             ItemKind::Const(folder.fold_ty(t), folder.fold_expr(e))
 882         }
 883         ItemKind::Fn(decl, unsafety, constness, abi, generics, body) => {
 884             let generics = folder.fold_generics(generics);
 885             let decl = folder.fold_fn_decl(decl);
 886             let body = folder.fold_block(body);
 887             ItemKind::Fn(decl, unsafety, constness, abi, generics, body)
 888         }
 889         ItemKind::Mod(m) => ItemKind::Mod(folder.fold_mod(m)),
 890         ItemKind::ForeignMod(nm) => ItemKind::ForeignMod(folder.fold_foreign_mod(nm)),
 891         ItemKind::GlobalAsm(ga) => ItemKind::GlobalAsm(folder.fold_global_asm(ga)),
 892         ItemKind::Ty(t, generics) => {
 893             ItemKind::Ty(folder.fold_ty(t), folder.fold_generics(generics))
 894         }
 895         ItemKind::Enum(enum_definition, generics) => {
 896             let generics = folder.fold_generics(generics);
 897             let variants = enum_definition.variants.move_map(|x| folder.fold_variant(x));
 898             ItemKind::Enum(ast::EnumDef { variants: variants }, generics)
 899         }
 900         ItemKind::Struct(struct_def, generics) => {
 901             let generics = folder.fold_generics(generics);
 902             ItemKind::Struct(folder.fold_variant_data(struct_def), generics)
 903         }
 904         ItemKind::Union(struct_def, generics) => {
 905             let generics = folder.fold_generics(generics);
 906             ItemKind::Union(folder.fold_variant_data(struct_def), generics)
 907         }
 908         ItemKind::DefaultImpl(unsafety, ref trait_ref) => {
 909             ItemKind::DefaultImpl(unsafety, folder.fold_trait_ref((*trait_ref).clone()))
 910         }
 911         ItemKind::Impl(unsafety,
 912                        polarity,
 913                        defaultness,
 914                        generics,
 915                        ifce,
 916                        ty,
 917                        impl_items) => ItemKind::Impl(
 918             unsafety,
 919             polarity,
 920             defaultness,
 921             folder.fold_generics(generics),
 922             ifce.map(|trait_ref| folder.fold_trait_ref(trait_ref.clone())),
 923             folder.fold_ty(ty),
 924             impl_items.move_flat_map(|item| folder.fold_impl_item(item)),
 925         ),
 926         ItemKind::Trait(unsafety, generics, bounds, items) => ItemKind::Trait(
 927             unsafety,
 928             folder.fold_generics(generics),
 929             folder.fold_bounds(bounds),
 930             items.move_flat_map(|item| folder.fold_trait_item(item)),
 931         ),
 932         ItemKind::Mac(m) => ItemKind::Mac(folder.fold_mac(m)),
 933         ItemKind::MacroDef(def) => ItemKind::MacroDef(folder.fold_macro_def(def)),
 934     }
 935 }
 936
 937 pub fn noop_fold_trait_item<T: Folder>(i: TraitItem, folder: &mut T)
 938                                        -> SmallVector<TraitItem> {
 939     SmallVector::one(TraitItem {
 940         id: folder.new_id(i.id),
 941         ident: folder.fold_ident(i.ident),
 942         attrs: fold_attrs(i.attrs, folder),
 943         node: match i.node {
 944             TraitItemKind::Const(ty, default) => {
 945                 TraitItemKind::Const(folder.fold_ty(ty),
 946                                default.map(|x| folder.fold_expr(x)))
 947             }
 948             TraitItemKind::Method(sig, body) => {
 949                 TraitItemKind::Method(noop_fold_method_sig(sig, folder),
 950                                 body.map(|x| folder.fold_block(x)))
 951             }
 952             TraitItemKind::Type(bounds, default) => {
 953                 TraitItemKind::Type(folder.fold_bounds(bounds),
 954                               default.map(|x| folder.fold_ty(x)))
 955             }
 956             ast::TraitItemKind::Macro(mac) => {
 957                 TraitItemKind::Macro(folder.fold_mac(mac))
 958             }
 959         },
 960         span: folder.new_span(i.span)
 961     })
 962 }
 963
 964 pub fn noop_fold_impl_item<T: Folder>(i: ImplItem, folder: &mut T)
 965                                       -> SmallVector<ImplItem> {
 966     SmallVector::one(ImplItem {
 967         id: folder.new_id(i.id),
 968         vis: folder.fold_vis(i.vis),
 969         ident: folder.fold_ident(i.ident),
 970         attrs: fold_attrs(i.attrs, folder),
 971         defaultness: i.defaultness,
 972         node: match i.node  {
 973             ast::ImplItemKind::Const(ty, expr) => {
 974                 ast::ImplItemKind::Const(folder.fold_ty(ty), folder.fold_expr(expr))
 975             }
 976             ast::ImplItemKind::Method(sig, body) => {
 977                 ast::ImplItemKind::Method(noop_fold_method_sig(sig, folder),
 978                                folder.fold_block(body))
 979             }
 980             ast::ImplItemKind::Type(ty) => ast::ImplItemKind::Type(folder.fold_ty(ty)),
 981             ast::ImplItemKind::Macro(mac) => ast::ImplItemKind::Macro(folder.fold_mac(mac))
 982         },
 983         span: folder.new_span(i.span)
 984     })
 985 }
 986
 987 pub fn noop_fold_mod<T: Folder>(Mod {inner, items}: Mod, folder: &mut T) -> Mod {
 988     Mod {
 989         inner: folder.new_span(inner),
 990         items: items.move_flat_map(|x| folder.fold_item(x)),
 991     }
 992 }
 993
 994 pub fn noop_fold_crate<T: Folder>(Crate {module, attrs, span}: Crate,
 995                                   folder: &mut T) -> Crate {
 996     let mut items = folder.fold_item(P(ast::Item {
 997         ident: keywords::Invalid.ident(),
 998         attrs: attrs,
 999         id: ast::DUMMY_NODE_ID,
1000         vis: ast::Visibility::Public,
1001         span: span,
1002         node: ast::ItemKind::Mod(module),
1003     })).into_iter();
1004
1005     let (module, attrs, span) = match items.next() {
1006         Some(item) => {
1007             assert!(items.next().is_none(),
1008                     "a crate cannot expand to more than one item");
1009             item.and_then(|ast::Item { attrs, span, node, .. }| {
1010                 match node {
1011                     ast::ItemKind::Mod(m) => (m, attrs, span),
1012                     _ => panic!("fold converted a module to not a module"),
1013                 }
1014             })
1015         }
1016         None => (ast::Mod {
1017             inner: span,
1018             items: vec![],
1019         }, vec![], span)
1020     };
1021
1022     Crate {
1023         module: module,
1024         attrs: attrs,
1025         span: span,
1026     }
1027 }
1028
1029 // fold one item into possibly many items
1030 pub fn noop_fold_item<T: Folder>(i: P<Item>, folder: &mut T) -> SmallVector<P<Item>> {
1031     SmallVector::one(i.map(|i| folder.fold_item_simple(i)))
1032 }
1033
1034 // fold one item into exactly one item
1035 pub fn noop_fold_item_simple<T: Folder>(Item {id, ident, attrs, node, vis, span}: Item,
1036                                         folder: &mut T) -> Item {
1037     Item {
1038         id: folder.new_id(id),
1039         vis: folder.fold_vis(vis),
1040         ident: folder.fold_ident(ident),
1041         attrs: fold_attrs(attrs, folder),
1042         node: folder.fold_item_kind(node),
1043         span: folder.new_span(span)
1044     }
1045 }
1046
1047 pub fn noop_fold_foreign_item<T: Folder>(ni: ForeignItem, folder: &mut T) -> ForeignItem {
1048     ForeignItem {
1049         id: folder.new_id(ni.id),
1050         vis: folder.fold_vis(ni.vis),
1051         ident: folder.fold_ident(ni.ident),
1052         attrs: fold_attrs(ni.attrs, folder),
1053         node: match ni.node {
1054             ForeignItemKind::Fn(fdec, generics) => {
1055                 ForeignItemKind::Fn(folder.fold_fn_decl(fdec), folder.fold_generics(generics))
1056             }
1057             ForeignItemKind::Static(t, m) => {
1058                 ForeignItemKind::Static(folder.fold_ty(t), m)
1059             }
1060         },
1061         span: folder.new_span(ni.span)
1062     }
1063 }
1064
1065 pub fn noop_fold_method_sig<T: Folder>(sig: MethodSig, folder: &mut T) -> MethodSig {
1066     MethodSig {
1067         generics: folder.fold_generics(sig.generics),
1068         abi: sig.abi,
1069         unsafety: sig.unsafety,
1070         constness: sig.constness,
1071         decl: folder.fold_fn_decl(sig.decl)
1072     }
1073 }
1074
1075 pub fn noop_fold_pat<T: Folder>(p: P<Pat>, folder: &mut T) -> P<Pat> {
1076     p.map(|Pat {id, node, span}| Pat {
1077         id: folder.new_id(id),
1078         node: match node {
1079             PatKind::Wild => PatKind::Wild,
1080             PatKind::Ident(binding_mode, pth1, sub) => {
1081                 PatKind::Ident(binding_mode,
1082                         Spanned{span: folder.new_span(pth1.span),
1083                                 node: folder.fold_ident(pth1.node)},
1084                         sub.map(|x| folder.fold_pat(x)))
1085             }
1086             PatKind::Lit(e) => PatKind::Lit(folder.fold_expr(e)),
1087             PatKind::TupleStruct(pth, pats, ddpos) => {
1088                 PatKind::TupleStruct(folder.fold_path(pth),
1089                         pats.move_map(|x| folder.fold_pat(x)), ddpos)
1090             }
1091             PatKind::Path(opt_qself, pth) => {
1092                 let opt_qself = opt_qself.map(|qself| {
1093                     QSelf { ty: folder.fold_ty(qself.ty), position: qself.position }
1094                 });
1095                 PatKind::Path(opt_qself, folder.fold_path(pth))
1096             }
1097             PatKind::Struct(pth, fields, etc) => {
1098                 let pth = folder.fold_path(pth);
1099                 let fs = fields.move_map(|f| {
1100                     Spanned { span: folder.new_span(f.span),
1101                               node: ast::FieldPat {
1102                                   ident: folder.fold_ident(f.node.ident),
1103                                   pat: folder.fold_pat(f.node.pat),
1104                                   is_shorthand: f.node.is_shorthand,
1105                                   attrs: fold_attrs(f.node.attrs.into(), folder).into()
1106                               }}
1107                 });
1108                 PatKind::Struct(pth, fs, etc)
1109             }
1110             PatKind::Tuple(elts, ddpos) => {
1111                 PatKind::Tuple(elts.move_map(|x| folder.fold_pat(x)), ddpos)
1112             }
1113             PatKind::Box(inner) => PatKind::Box(folder.fold_pat(inner)),
1114             PatKind::Ref(inner, mutbl) => PatKind::Ref(folder.fold_pat(inner), mutbl),
1115             PatKind::Range(e1, e2, end) => {
1116                 PatKind::Range(folder.fold_expr(e1),
1117                                folder.fold_expr(e2),
1118                                folder.fold_range_end(end))
1119             },
1120             PatKind::Slice(before, slice, after) => {
1121                 PatKind::Slice(before.move_map(|x| folder.fold_pat(x)),
1122                        slice.map(|x| folder.fold_pat(x)),
1123                        after.move_map(|x| folder.fold_pat(x)))
1124             }
1125             PatKind::Mac(mac) => PatKind::Mac(folder.fold_mac(mac))
1126         },
1127         span: folder.new_span(span)
1128     })
1129 }
1130
1131 pub fn noop_fold_range_end<T: Folder>(end: RangeEnd, _folder: &mut T) -> RangeEnd {
1132     end
1133 }
1134
1135 pub fn noop_fold_expr<T: Folder>(Expr {id, node, span, attrs}: Expr, folder: &mut T) -> Expr {
1136     Expr {
1137         node: match node {
1138             ExprKind::Box(e) => {
1139                 ExprKind::Box(folder.fold_expr(e))
1140             }
1141             ExprKind::InPlace(p, e) => {
1142                 ExprKind::InPlace(folder.fold_expr(p), folder.fold_expr(e))
1143             }
1144             ExprKind::Array(exprs) => {
1145                 ExprKind::Array(folder.fold_exprs(exprs))
1146             }
1147             ExprKind::Repeat(expr, count) => {
1148                 ExprKind::Repeat(folder.fold_expr(expr), folder.fold_expr(count))
1149             }
1150             ExprKind::Tup(exprs) => ExprKind::Tup(folder.fold_exprs(exprs)),
1151             ExprKind::Call(f, args) => {
1152                 ExprKind::Call(folder.fold_expr(f),
1153                          folder.fold_exprs(args))
1154             }
1155             ExprKind::MethodCall(i, tps, args) => {
1156                 ExprKind::MethodCall(
1157                     respan(folder.new_span(i.span), folder.fold_ident(i.node)),
1158                     tps.move_map(|x| folder.fold_ty(x)),
1159                     folder.fold_exprs(args))
1160             }
1161             ExprKind::Binary(binop, lhs, rhs) => {
1162                 ExprKind::Binary(binop,
1163                         folder.fold_expr(lhs),
1164                         folder.fold_expr(rhs))
1165             }
1166             ExprKind::Unary(binop, ohs) => {
1167                 ExprKind::Unary(binop, folder.fold_expr(ohs))
1168             }
1169             ExprKind::Lit(l) => ExprKind::Lit(l),
1170             ExprKind::Cast(expr, ty) => {
1171                 ExprKind::Cast(folder.fold_expr(expr), folder.fold_ty(ty))
1172             }
1173             ExprKind::Type(expr, ty) => {
1174                 ExprKind::Type(folder.fold_expr(expr), folder.fold_ty(ty))
1175             }
1176             ExprKind::AddrOf(m, ohs) => ExprKind::AddrOf(m, folder.fold_expr(ohs)),
1177             ExprKind::If(cond, tr, fl) => {
1178                 ExprKind::If(folder.fold_expr(cond),
1179                        folder.fold_block(tr),
1180                        fl.map(|x| folder.fold_expr(x)))
1181             }
1182             ExprKind::IfLet(pat, expr, tr, fl) => {
1183                 ExprKind::IfLet(folder.fold_pat(pat),
1184                           folder.fold_expr(expr),
1185                           folder.fold_block(tr),
1186                           fl.map(|x| folder.fold_expr(x)))
1187             }
1188             ExprKind::While(cond, body, opt_ident) => {
1189                 ExprKind::While(folder.fold_expr(cond),
1190                           folder.fold_block(body),
1191                           opt_ident.map(|label| respan(folder.new_span(label.span),
1192                                                        folder.fold_ident(label.node))))
1193             }
1194             ExprKind::WhileLet(pat, expr, body, opt_ident) => {
1195                 ExprKind::WhileLet(folder.fold_pat(pat),
1196                              folder.fold_expr(expr),
1197                              folder.fold_block(body),
1198                              opt_ident.map(|label| respan(folder.new_span(label.span),
1199                                                           folder.fold_ident(label.node))))
1200             }
1201             ExprKind::ForLoop(pat, iter, body, opt_ident) => {
1202                 ExprKind::ForLoop(folder.fold_pat(pat),
1203                             folder.fold_expr(iter),
1204                             folder.fold_block(body),
1205                             opt_ident.map(|label| respan(folder.new_span(label.span),
1206                                                          folder.fold_ident(label.node))))
1207             }
1208             ExprKind::Loop(body, opt_ident) => {
1209                 ExprKind::Loop(folder.fold_block(body),
1210                                opt_ident.map(|label| respan(folder.new_span(label.span),
1211                                                             folder.fold_ident(label.node))))
1212             }
1213             ExprKind::Match(expr, arms) => {
1214                 ExprKind::Match(folder.fold_expr(expr),
1215                           arms.move_map(|x| folder.fold_arm(x)))
1216             }
1217             ExprKind::Closure(capture_clause, decl, body, span) => {
1218                 ExprKind::Closure(capture_clause,
1219                                   folder.fold_fn_decl(decl),
1220                                   folder.fold_expr(body),
1221                                   folder.new_span(span))
1222             }
1223             ExprKind::Block(blk) => ExprKind::Block(folder.fold_block(blk)),
1224             ExprKind::Assign(el, er) => {
1225                 ExprKind::Assign(folder.fold_expr(el), folder.fold_expr(er))
1226             }
1227             ExprKind::AssignOp(op, el, er) => {
1228                 ExprKind::AssignOp(op,
1229                             folder.fold_expr(el),
1230                             folder.fold_expr(er))
1231             }
1232             ExprKind::Field(el, ident) => {
1233                 ExprKind::Field(folder.fold_expr(el),
1234                           respan(folder.new_span(ident.span),
1235                                  folder.fold_ident(ident.node)))
1236             }
1237             ExprKind::TupField(el, ident) => {
1238                 ExprKind::TupField(folder.fold_expr(el),
1239                              respan(folder.new_span(ident.span),
1240                                     folder.fold_usize(ident.node)))
1241             }
1242             ExprKind::Index(el, er) => {
1243                 ExprKind::Index(folder.fold_expr(el), folder.fold_expr(er))
1244             }
1245             ExprKind::Range(e1, e2, lim) => {
1246                 ExprKind::Range(e1.map(|x| folder.fold_expr(x)),
1247                                 e2.map(|x| folder.fold_expr(x)),
1248                                 lim)
1249             }
1250             ExprKind::Path(qself, path) => {
1251                 let qself = qself.map(|QSelf { ty, position }| {
1252                     QSelf {
1253                         ty: folder.fold_ty(ty),
1254                         position: position
1255                     }
1256                 });
1257                 ExprKind::Path(qself, folder.fold_path(path))
1258             }
1259             ExprKind::Break(opt_ident, opt_expr) => {
1260                 ExprKind::Break(opt_ident.map(|label| respan(folder.new_span(label.span),
1261                                                              folder.fold_ident(label.node))),
1262                                 opt_expr.map(|e| folder.fold_expr(e)))
1263             }
1264             ExprKind::Continue(opt_ident) => ExprKind::Continue(opt_ident.map(|label|
1265                 respan(folder.new_span(label.span),
1266                        folder.fold_ident(label.node)))
1267             ),
1268             ExprKind::Ret(e) => ExprKind::Ret(e.map(|x| folder.fold_expr(x))),
1269             ExprKind::InlineAsm(asm) => ExprKind::InlineAsm(asm.map(|asm| {
1270                 InlineAsm {
1271                     inputs: asm.inputs.move_map(|(c, input)| {
1272                         (c, folder.fold_expr(input))
1273                     }),
1274                     outputs: asm.outputs.move_map(|out| {
1275                         InlineAsmOutput {
1276                             constraint: out.constraint,
1277                             expr: folder.fold_expr(out.expr),
1278                             is_rw: out.is_rw,
1279                             is_indirect: out.is_indirect,
1280                         }
1281                     }),
1282                     ..asm
1283                 }
1284             })),
1285             ExprKind::Mac(mac) => ExprKind::Mac(folder.fold_mac(mac)),
1286             ExprKind::Struct(path, fields, maybe_expr) => {
1287                 ExprKind::Struct(folder.fold_path(path),
1288                         fields.move_map(|x| folder.fold_field(x)),
1289                         maybe_expr.map(|x| folder.fold_expr(x)))
1290             },
1291             ExprKind::Paren(ex) => {
1292                 let sub_expr = folder.fold_expr(ex);
1293                 return Expr {
1294                     // Nodes that are equal modulo `Paren` sugar no-ops should have the same ids.
1295                     id: sub_expr.id,
1296                     node: ExprKind::Paren(sub_expr),
1297                     span: folder.new_span(span),
1298                     attrs: fold_attrs(attrs.into(), folder).into(),
1299                 };
1300             }
1301             ExprKind::Try(ex) => ExprKind::Try(folder.fold_expr(ex)),
1302             ExprKind::Catch(body) => ExprKind::Catch(folder.fold_block(body)),
1303         },
1304         id: folder.new_id(id),
1305         span: folder.new_span(span),
1306         attrs: fold_attrs(attrs.into(), folder).into(),
1307     }
1308 }
1309
1310 pub fn noop_fold_opt_expr<T: Folder>(e: P<Expr>, folder: &mut T) -> Option<P<Expr>> {
1311     Some(folder.fold_expr(e))
1312 }
1313
1314 pub fn noop_fold_exprs<T: Folder>(es: Vec<P<Expr>>, folder: &mut T) -> Vec<P<Expr>> {
1315     es.move_flat_map(|e| folder.fold_opt_expr(e))
1316 }
1317
1318 pub fn noop_fold_stmt<T: Folder>(Stmt {node, span, id}: Stmt, folder: &mut T) -> SmallVector<Stmt> {
1319     let id = folder.new_id(id);
1320     let span = folder.new_span(span);
1321     noop_fold_stmt_kind(node, folder).into_iter().map(|node| {
1322         Stmt { id: id, node: node, span: span }
1323     }).collect()
1324 }
1325
1326 pub fn noop_fold_stmt_kind<T: Folder>(node: StmtKind, folder: &mut T) -> SmallVector<StmtKind> {
1327     match node {
1328         StmtKind::Local(local) => SmallVector::one(StmtKind::Local(folder.fold_local(local))),
1329         StmtKind::Item(item) => folder.fold_item(item).into_iter().map(StmtKind::Item).collect(),
1330         StmtKind::Expr(expr) => {
1331             folder.fold_opt_expr(expr).into_iter().map(StmtKind::Expr).collect()
1332         }
1333         StmtKind::Semi(expr) => {
1334             folder.fold_opt_expr(expr).into_iter().map(StmtKind::Semi).collect()
1335         }
1336         StmtKind::Mac(mac) => SmallVector::one(StmtKind::Mac(mac.map(|(mac, semi, attrs)| {
1337             (folder.fold_mac(mac), semi, fold_attrs(attrs.into(), folder).into())
1338         }))),
1339     }
1340 }
1341
1342 pub fn noop_fold_vis<T: Folder>(vis: Visibility, folder: &mut T) -> Visibility {
1343     match vis {
1344         Visibility::Restricted { path, id } => Visibility::Restricted {
1345             path: path.map(|path| folder.fold_path(path)),
1346             id: folder.new_id(id)
1347         },
1348         _ => vis,
1349     }
1350 }
1351
1352 #[cfg(test)]
1353 mod tests {
1354     use std::io;
1355     use ast::{self, Ident};
1356     use util::parser_testing::{string_to_crate, matches_codepattern};
1357     use print::pprust;
1358     use fold;
1359     use super::*;
1360
1361     // this version doesn't care about getting comments or docstrings in.
1362     fn fake_print_crate(s: &mut pprust::State,
1363                         krate: &ast::Crate) -> io::Result<()> {
1364         s.print_mod(&krate.module, &krate.attrs)
1365     }
1366
1367     // change every identifier to "zz"
1368     struct ToZzIdentFolder;
1369
1370     impl Folder for ToZzIdentFolder {
1371         fn fold_ident(&mut self, _: ast::Ident) -> ast::Ident {
1372             Ident::from_str("zz")
1373         }
1374         fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
1375             fold::noop_fold_mac(mac, self)
1376         }
1377     }
1378
1379     // maybe add to expand.rs...
1380     macro_rules! assert_pred {
1381         ($pred:expr, $predname:expr, $a:expr , $b:expr) => (
1382             {
1383                 let pred_val = $pred;
1384                 let a_val = $a;
1385                 let b_val = $b;
1386                 if !(pred_val(&a_val, &b_val)) {
1387                     panic!("expected args satisfying {}, got {} and {}",
1388                           $predname, a_val, b_val);
1389                 }
1390             }
1391         )
1392     }
1393
1394     // make sure idents get transformed everywhere
1395     #[test] fn ident_transformation () {
1396         let mut zz_fold = ToZzIdentFolder;
1397         let ast = string_to_crate(
1398             "#[a] mod b {fn c (d : e, f : g) {h!(i,j,k);l;m}}".to_string());
1399         let folded_crate = zz_fold.fold_crate(ast);
1400         assert_pred!(
1401             matches_codepattern,
1402             "matches_codepattern",
1403             pprust::to_string(|s| fake_print_crate(s, &folded_crate)),
1404             "#[zz]mod zz{fn zz(zz:zz,zz:zz){zz!(zz,zz,zz);zz;zz}}".to_string());
1405     }
1406
1407     // even inside macro defs....
1408     #[test] fn ident_transformation_in_defs () {
1409         let mut zz_fold = ToZzIdentFolder;
1410         let ast = string_to_crate(
1411             "macro_rules! a {(b $c:expr $(d $e:token)f+ => \
1412              (g $(d $d $e)+))} ".to_string());
1413         let folded_crate = zz_fold.fold_crate(ast);
1414         assert_pred!(
1415             matches_codepattern,
1416             "matches_codepattern",
1417             pprust::to_string(|s| fake_print_crate(s, &folded_crate)),
1418             "macro_rules! zz((zz$zz:zz$(zz $zz:zz)zz+=>(zz$(zz$zz$zz)+)));".to_string());
1419     }
1420 }