src/libsyntax/fold.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! A Folder represents an AST->AST fold; it accepts an AST piece,
  12 //! and returns a piece of the same type. So, for instance, macro
  13 //! expansion is a Folder that walks over an AST and produces another
  14 //! AST.
  15 //!
  16 //! Note: using a Folder (other than the MacroExpander Folder) on
  17 //! an AST before macro expansion is probably a bad idea. For instance,
  18 //! a folder renaming item names in a module will miss all of those
  19 //! that are created by the expansion of a macro.
  20
  21 use ast::*;
  22 use ast;
  23 use syntax_pos::Span;
  24 use codemap::{Spanned, respan};
  25 use parse::token::{self, Token};
  26 use ptr::P;
  27 use symbol::keywords;
  28 use tokenstream::*;
  29 use util::small_vector::SmallVector;
  30 use util::move_map::MoveMap;
  31
  32 use 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_use_tree(&mut self, use_tree: UseTree) -> UseTree {
  60         noop_fold_use_tree(use_tree, self)
  61     }
  62
  63     fn fold_foreign_item(&mut self, ni: ForeignItem) -> 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_label(&mut self, label: Label) -> Label {
 197         noop_fold_label(label, self)
 198     }
 199
 200     fn fold_lifetime(&mut self, l: Lifetime) -> Lifetime {
 201         noop_fold_lifetime(l, self)
 202     }
 203
 204     fn fold_lifetime_def(&mut self, l: LifetimeDef) -> LifetimeDef {
 205         noop_fold_lifetime_def(l, self)
 206     }
 207
 208     fn fold_attribute(&mut self, at: Attribute) -> Option<Attribute> {
 209         noop_fold_attribute(at, self)
 210     }
 211
 212     fn fold_arg(&mut self, a: Arg) -> Arg {
 213         noop_fold_arg(a, self)
 214     }
 215
 216     fn fold_generics(&mut self, generics: Generics) -> Generics {
 217         noop_fold_generics(generics, self)
 218     }
 219
 220     fn fold_trait_ref(&mut self, p: TraitRef) -> TraitRef {
 221         noop_fold_trait_ref(p, self)
 222     }
 223
 224     fn fold_poly_trait_ref(&mut self, p: PolyTraitRef) -> PolyTraitRef {
 225         noop_fold_poly_trait_ref(p, self)
 226     }
 227
 228     fn fold_variant_data(&mut self, vdata: VariantData) -> VariantData {
 229         noop_fold_variant_data(vdata, self)
 230     }
 231
 232     fn fold_lifetimes(&mut self, lts: Vec<Lifetime>) -> Vec<Lifetime> {
 233         noop_fold_lifetimes(lts, self)
 234     }
 235
 236     fn fold_lifetime_defs(&mut self, lts: Vec<LifetimeDef>) -> Vec<LifetimeDef> {
 237         noop_fold_lifetime_defs(lts, self)
 238     }
 239
 240     fn fold_ty_param(&mut self, tp: TyParam) -> TyParam {
 241         noop_fold_ty_param(tp, self)
 242     }
 243
 244     fn fold_generic_param(&mut self, param: GenericParam) -> GenericParam {
 245         noop_fold_generic_param(param, self)
 246     }
 247
 248     fn fold_generic_params(&mut self, params: Vec<GenericParam>) -> Vec<GenericParam> {
 249         noop_fold_generic_params(params, self)
 250     }
 251
 252     fn fold_tt(&mut self, tt: TokenTree) -> TokenTree {
 253         noop_fold_tt(tt, self)
 254     }
 255
 256     fn fold_tts(&mut self, tts: TokenStream) -> TokenStream {
 257         noop_fold_tts(tts, self)
 258     }
 259
 260     fn fold_token(&mut self, t: token::Token) -> token::Token {
 261         noop_fold_token(t, self)
 262     }
 263
 264     fn fold_interpolated(&mut self, nt: token::Nonterminal) -> token::Nonterminal {
 265         noop_fold_interpolated(nt, self)
 266     }
 267
 268     fn fold_opt_lifetime(&mut self, o_lt: Option<Lifetime>) -> Option<Lifetime> {
 269         noop_fold_opt_lifetime(o_lt, self)
 270     }
 271
 272     fn fold_opt_bounds(&mut self, b: Option<TyParamBounds>)
 273                        -> Option<TyParamBounds> {
 274         noop_fold_opt_bounds(b, self)
 275     }
 276
 277     fn fold_bounds(&mut self, b: TyParamBounds)
 278                        -> TyParamBounds {
 279         noop_fold_bounds(b, self)
 280     }
 281
 282     fn fold_ty_param_bound(&mut self, tpb: TyParamBound) -> TyParamBound {
 283         noop_fold_ty_param_bound(tpb, self)
 284     }
 285
 286     fn fold_mt(&mut self, mt: MutTy) -> MutTy {
 287         noop_fold_mt(mt, self)
 288     }
 289
 290     fn fold_field(&mut self, field: Field) -> Field {
 291         noop_fold_field(field, self)
 292     }
 293
 294     fn fold_where_clause(&mut self, where_clause: WhereClause)
 295                          -> WhereClause {
 296         noop_fold_where_clause(where_clause, self)
 297     }
 298
 299     fn fold_where_predicate(&mut self, where_predicate: WherePredicate)
 300                             -> WherePredicate {
 301         noop_fold_where_predicate(where_predicate, self)
 302     }
 303
 304     fn fold_vis(&mut self, vis: Visibility) -> Visibility {
 305         noop_fold_vis(vis, self)
 306     }
 307
 308     fn new_id(&mut self, i: NodeId) -> NodeId {
 309         i
 310     }
 311
 312     fn new_span(&mut self, sp: Span) -> Span {
 313         sp
 314     }
 315 }
 316
 317 pub fn noop_fold_meta_items<T: Folder>(meta_items: Vec<MetaItem>, fld: &mut T) -> Vec<MetaItem> {
 318     meta_items.move_map(|x| fld.fold_meta_item(x))
 319 }
 320
 321 pub fn noop_fold_use_tree<T: Folder>(use_tree: UseTree, fld: &mut T) -> UseTree {
 322     UseTree {
 323         span: fld.new_span(use_tree.span),
 324         prefix: fld.fold_path(use_tree.prefix),
 325         kind: match use_tree.kind {
 326             UseTreeKind::Simple(ident) => UseTreeKind::Simple(fld.fold_ident(ident)),
 327             UseTreeKind::Glob => UseTreeKind::Glob,
 328             UseTreeKind::Nested(items) => UseTreeKind::Nested(items.move_map(|(tree, id)| {
 329                 (fld.fold_use_tree(tree), fld.new_id(id))
 330             })),
 331         },
 332     }
 333 }
 334
 335 pub fn fold_attrs<T: Folder>(attrs: Vec<Attribute>, fld: &mut T) -> Vec<Attribute> {
 336     attrs.move_flat_map(|x| fld.fold_attribute(x))
 337 }
 338
 339 pub fn fold_thin_attrs<T: Folder>(attrs: ThinVec<Attribute>, fld: &mut T) -> ThinVec<Attribute> {
 340     fold_attrs(attrs.into(), fld).into()
 341 }
 342
 343 pub fn noop_fold_arm<T: Folder>(Arm {attrs, pats, guard, body, beginning_vert}: Arm,
 344     fld: &mut T) -> Arm {
 345     Arm {
 346         attrs: fold_attrs(attrs, fld),
 347         pats: pats.move_map(|x| fld.fold_pat(x)),
 348         guard: guard.map(|x| fld.fold_expr(x)),
 349         body: fld.fold_expr(body),
 350         beginning_vert,
 351     }
 352 }
 353
 354 pub fn noop_fold_ty_binding<T: Folder>(b: TypeBinding, fld: &mut T) -> TypeBinding {
 355     TypeBinding {
 356         id: fld.new_id(b.id),
 357         ident: fld.fold_ident(b.ident),
 358         ty: fld.fold_ty(b.ty),
 359         span: fld.new_span(b.span),
 360     }
 361 }
 362
 363 pub fn noop_fold_ty<T: Folder>(t: P<Ty>, fld: &mut T) -> P<Ty> {
 364     t.map(|Ty {id, node, span}| Ty {
 365         id: fld.new_id(id),
 366         node: match node {
 367             TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err => node,
 368             TyKind::Slice(ty) => TyKind::Slice(fld.fold_ty(ty)),
 369             TyKind::Ptr(mt) => TyKind::Ptr(fld.fold_mt(mt)),
 370             TyKind::Rptr(region, mt) => {
 371                 TyKind::Rptr(fld.fold_opt_lifetime(region), fld.fold_mt(mt))
 372             }
 373             TyKind::BareFn(f) => {
 374                 TyKind::BareFn(f.map(|BareFnTy {generic_params, unsafety, abi, decl}| BareFnTy {
 375                     generic_params: fld.fold_generic_params(generic_params),
 376                     unsafety,
 377                     abi,
 378                     decl: fld.fold_fn_decl(decl)
 379                 }))
 380             }
 381             TyKind::Never => node,
 382             TyKind::Tup(tys) => TyKind::Tup(tys.move_map(|ty| fld.fold_ty(ty))),
 383             TyKind::Paren(ty) => TyKind::Paren(fld.fold_ty(ty)),
 384             TyKind::Path(qself, path) => {
 385                 let qself = qself.map(|QSelf { ty, position }| {
 386                     QSelf {
 387                         ty: fld.fold_ty(ty),
 388                         position,
 389                     }
 390                 });
 391                 TyKind::Path(qself, fld.fold_path(path))
 392             }
 393             TyKind::Array(ty, e) => {
 394                 TyKind::Array(fld.fold_ty(ty), fld.fold_expr(e))
 395             }
 396             TyKind::Typeof(expr) => {
 397                 TyKind::Typeof(fld.fold_expr(expr))
 398             }
 399             TyKind::TraitObject(bounds, syntax) => {
 400                 TyKind::TraitObject(bounds.move_map(|b| fld.fold_ty_param_bound(b)), syntax)
 401             }
 402             TyKind::ImplTrait(bounds) => {
 403                 TyKind::ImplTrait(bounds.move_map(|b| fld.fold_ty_param_bound(b)))
 404             }
 405             TyKind::Mac(mac) => {
 406                 TyKind::Mac(fld.fold_mac(mac))
 407             }
 408         },
 409         span: fld.new_span(span)
 410     })
 411 }
 412
 413 pub fn noop_fold_foreign_mod<T: Folder>(ForeignMod {abi, items}: ForeignMod,
 414                                         fld: &mut T) -> ForeignMod {
 415     ForeignMod {
 416         abi,
 417         items: items.move_map(|x| fld.fold_foreign_item(x)),
 418     }
 419 }
 420
 421 pub fn noop_fold_global_asm<T: Folder>(ga: P<GlobalAsm>,
 422                                        _: &mut T) -> P<GlobalAsm> {
 423     ga
 424 }
 425
 426 pub fn noop_fold_variant<T: Folder>(v: Variant, fld: &mut T) -> Variant {
 427     Spanned {
 428         node: Variant_ {
 429             name: fld.fold_ident(v.node.name),
 430             attrs: fold_attrs(v.node.attrs, fld),
 431             data: fld.fold_variant_data(v.node.data),
 432             disr_expr: v.node.disr_expr.map(|e| fld.fold_expr(e)),
 433         },
 434         span: fld.new_span(v.span),
 435     }
 436 }
 437
 438 pub fn noop_fold_ident<T: Folder>(i: Ident, _: &mut T) -> Ident {
 439     i
 440 }
 441
 442 pub fn noop_fold_usize<T: Folder>(i: usize, _: &mut T) -> usize {
 443     i
 444 }
 445
 446 pub fn noop_fold_path<T: Folder>(Path { segments, span }: Path, fld: &mut T) -> Path {
 447     Path {
 448         segments: segments.move_map(|PathSegment {identifier, span, parameters}| PathSegment {
 449             identifier: fld.fold_ident(identifier),
 450             span: fld.new_span(span),
 451             parameters: parameters.map(|ps| ps.map(|ps| fld.fold_path_parameters(ps))),
 452         }),
 453         span: fld.new_span(span)
 454     }
 455 }
 456
 457 pub fn noop_fold_path_parameters<T: Folder>(path_parameters: PathParameters, fld: &mut T)
 458                                             -> PathParameters
 459 {
 460     match path_parameters {
 461         PathParameters::AngleBracketed(data) =>
 462             PathParameters::AngleBracketed(fld.fold_angle_bracketed_parameter_data(data)),
 463         PathParameters::Parenthesized(data) =>
 464             PathParameters::Parenthesized(fld.fold_parenthesized_parameter_data(data)),
 465     }
 466 }
 467
 468 pub fn noop_fold_angle_bracketed_parameter_data<T: Folder>(data: AngleBracketedParameterData,
 469                                                            fld: &mut T)
 470                                                            -> AngleBracketedParameterData
 471 {
 472     let AngleBracketedParameterData { lifetimes, types, bindings, span } = data;
 473     AngleBracketedParameterData { lifetimes: fld.fold_lifetimes(lifetimes),
 474                                   types: types.move_map(|ty| fld.fold_ty(ty)),
 475                                   bindings: bindings.move_map(|b| fld.fold_ty_binding(b)),
 476                                   span: fld.new_span(span) }
 477 }
 478
 479 pub fn noop_fold_parenthesized_parameter_data<T: Folder>(data: ParenthesizedParameterData,
 480                                                          fld: &mut T)
 481                                                          -> ParenthesizedParameterData
 482 {
 483     let ParenthesizedParameterData { inputs, output, span } = data;
 484     ParenthesizedParameterData { inputs: inputs.move_map(|ty| fld.fold_ty(ty)),
 485                                  output: output.map(|ty| fld.fold_ty(ty)),
 486                                  span: fld.new_span(span) }
 487 }
 488
 489 pub fn noop_fold_local<T: Folder>(l: P<Local>, fld: &mut T) -> P<Local> {
 490     l.map(|Local {id, pat, ty, init, span, attrs}| Local {
 491         id: fld.new_id(id),
 492         pat: fld.fold_pat(pat),
 493         ty: ty.map(|t| fld.fold_ty(t)),
 494         init: init.map(|e| fld.fold_expr(e)),
 495         span: fld.new_span(span),
 496         attrs: fold_attrs(attrs.into(), fld).into(),
 497     })
 498 }
 499
 500 pub fn noop_fold_attribute<T: Folder>(attr: Attribute, fld: &mut T) -> Option<Attribute> {
 501     Some(Attribute {
 502         id: attr.id,
 503         style: attr.style,
 504         path: fld.fold_path(attr.path),
 505         tokens: fld.fold_tts(attr.tokens),
 506         is_sugared_doc: attr.is_sugared_doc,
 507         span: fld.new_span(attr.span),
 508     })
 509 }
 510
 511 pub fn noop_fold_mac<T: Folder>(Spanned {node, span}: Mac, fld: &mut T) -> Mac {
 512     Spanned {
 513         node: Mac_ {
 514             tts: fld.fold_tts(node.stream()).into(),
 515             path: fld.fold_path(node.path),
 516         },
 517         span: fld.new_span(span)
 518     }
 519 }
 520
 521 pub fn noop_fold_macro_def<T: Folder>(def: MacroDef, fld: &mut T) -> MacroDef {
 522     MacroDef {
 523         tokens: fld.fold_tts(def.tokens.into()).into(),
 524         legacy: def.legacy,
 525     }
 526 }
 527
 528 pub fn noop_fold_meta_list_item<T: Folder>(li: NestedMetaItem, fld: &mut T)
 529     -> NestedMetaItem {
 530     Spanned {
 531         node: match li.node {
 532             NestedMetaItemKind::MetaItem(mi) =>  {
 533                 NestedMetaItemKind::MetaItem(fld.fold_meta_item(mi))
 534             },
 535             NestedMetaItemKind::Literal(lit) => NestedMetaItemKind::Literal(lit)
 536         },
 537         span: fld.new_span(li.span)
 538     }
 539 }
 540
 541 pub fn noop_fold_meta_item<T: Folder>(mi: MetaItem, fld: &mut T) -> MetaItem {
 542     MetaItem {
 543         name: mi.name,
 544         node: match mi.node {
 545             MetaItemKind::Word => MetaItemKind::Word,
 546             MetaItemKind::List(mis) => {
 547                 MetaItemKind::List(mis.move_map(|e| fld.fold_meta_list_item(e)))
 548             },
 549             MetaItemKind::NameValue(s) => MetaItemKind::NameValue(s),
 550         },
 551         span: fld.new_span(mi.span)
 552     }
 553 }
 554
 555 pub fn noop_fold_arg<T: Folder>(Arg {id, pat, ty}: Arg, fld: &mut T) -> Arg {
 556     Arg {
 557         id: fld.new_id(id),
 558         pat: fld.fold_pat(pat),
 559         ty: fld.fold_ty(ty)
 560     }
 561 }
 562
 563 pub fn noop_fold_tt<T: Folder>(tt: TokenTree, fld: &mut T) -> TokenTree {
 564     match tt {
 565         TokenTree::Token(span, tok) =>
 566             TokenTree::Token(fld.new_span(span), fld.fold_token(tok)),
 567         TokenTree::Delimited(span, delimed) => TokenTree::Delimited(fld.new_span(span), Delimited {
 568             tts: fld.fold_tts(delimed.stream()).into(),
 569             delim: delimed.delim,
 570         }),
 571     }
 572 }
 573
 574 pub fn noop_fold_tts<T: Folder>(tts: TokenStream, fld: &mut T) -> TokenStream {
 575     tts.map(|tt| fld.fold_tt(tt))
 576 }
 577
 578 // apply ident folder if it's an ident, apply other folds to interpolated nodes
 579 pub fn noop_fold_token<T: Folder>(t: token::Token, fld: &mut T) -> token::Token {
 580     match t {
 581         token::Ident(id) => token::Ident(fld.fold_ident(id)),
 582         token::Lifetime(id) => token::Lifetime(fld.fold_ident(id)),
 583         token::Interpolated(nt) => {
 584             let nt = match Rc::try_unwrap(nt) {
 585                 Ok(nt) => nt,
 586                 Err(nt) => (*nt).clone(),
 587             };
 588             Token::interpolated(fld.fold_interpolated(nt.0))
 589         }
 590         _ => t
 591     }
 592 }
 593
 594 /// apply folder to elements of interpolated nodes
 595 //
 596 // NB: this can occur only when applying a fold to partially expanded code, where
 597 // parsed pieces have gotten implanted ito *other* macro invocations. This is relevant
 598 // for macro hygiene, but possibly not elsewhere.
 599 //
 600 // One problem here occurs because the types for fold_item, fold_stmt, etc. allow the
 601 // folder to return *multiple* items; this is a problem for the nodes here, because
 602 // they insist on having exactly one piece. One solution would be to mangle the fold
 603 // trait to include one-to-many and one-to-one versions of these entry points, but that
 604 // would probably confuse a lot of people and help very few. Instead, I'm just going
 605 // to put in dynamic checks. I think the performance impact of this will be pretty much
 606 // nonexistent. The danger is that someone will apply a fold to a partially expanded
 607 // node, and will be confused by the fact that their "fold_item" or "fold_stmt" isn't
 608 // getting called on NtItem or NtStmt nodes. Hopefully they'll wind up reading this
 609 // comment, and doing something appropriate.
 610 //
 611 // BTW, design choice: I considered just changing the type of, e.g., NtItem to contain
 612 // multiple items, but decided against it when I looked at parse_item_or_view_item and
 613 // tried to figure out what I would do with multiple items there....
 614 pub fn noop_fold_interpolated<T: Folder>(nt: token::Nonterminal, fld: &mut T)
 615                                          -> token::Nonterminal {
 616     match nt {
 617         token::NtItem(item) =>
 618             token::NtItem(fld.fold_item(item)
 619                           // this is probably okay, because the only folds likely
 620                           // to peek inside interpolated nodes will be renamings/markings,
 621                           // which map single items to single items
 622                           .expect_one("expected fold to produce exactly one item")),
 623         token::NtBlock(block) => token::NtBlock(fld.fold_block(block)),
 624         token::NtStmt(stmt) =>
 625             token::NtStmt(fld.fold_stmt(stmt)
 626                           // this is probably okay, because the only folds likely
 627                           // to peek inside interpolated nodes will be renamings/markings,
 628                           // which map single items to single items
 629                           .expect_one("expected fold to produce exactly one statement")),
 630         token::NtPat(pat) => token::NtPat(fld.fold_pat(pat)),
 631         token::NtExpr(expr) => token::NtExpr(fld.fold_expr(expr)),
 632         token::NtTy(ty) => token::NtTy(fld.fold_ty(ty)),
 633         token::NtIdent(id) => token::NtIdent(Spanned::<Ident>{node: fld.fold_ident(id.node), ..id}),
 634         token::NtMeta(meta) => token::NtMeta(fld.fold_meta_item(meta)),
 635         token::NtPath(path) => token::NtPath(fld.fold_path(path)),
 636         token::NtTT(tt) => token::NtTT(fld.fold_tt(tt)),
 637         token::NtArm(arm) => token::NtArm(fld.fold_arm(arm)),
 638         token::NtImplItem(item) =>
 639             token::NtImplItem(fld.fold_impl_item(item)
 640                               .expect_one("expected fold to produce exactly one item")),
 641         token::NtTraitItem(item) =>
 642             token::NtTraitItem(fld.fold_trait_item(item)
 643                                .expect_one("expected fold to produce exactly one item")),
 644         token::NtGenerics(generics) => token::NtGenerics(fld.fold_generics(generics)),
 645         token::NtWhereClause(where_clause) =>
 646             token::NtWhereClause(fld.fold_where_clause(where_clause)),
 647         token::NtArg(arg) => token::NtArg(fld.fold_arg(arg)),
 648         token::NtVis(vis) => token::NtVis(fld.fold_vis(vis)),
 649         token::NtLifetime(lifetime) => token::NtLifetime(fld.fold_lifetime(lifetime)),
 650     }
 651 }
 652
 653 pub fn noop_fold_fn_decl<T: Folder>(decl: P<FnDecl>, fld: &mut T) -> P<FnDecl> {
 654     decl.map(|FnDecl {inputs, output, variadic}| FnDecl {
 655         inputs: inputs.move_map(|x| fld.fold_arg(x)),
 656         output: match output {
 657             FunctionRetTy::Ty(ty) => FunctionRetTy::Ty(fld.fold_ty(ty)),
 658             FunctionRetTy::Default(span) => FunctionRetTy::Default(fld.new_span(span)),
 659         },
 660         variadic,
 661     })
 662 }
 663
 664 pub fn noop_fold_ty_param_bound<T>(tpb: TyParamBound, fld: &mut T)
 665                                    -> TyParamBound
 666                                    where T: Folder {
 667     match tpb {
 668         TraitTyParamBound(ty, modifier) => TraitTyParamBound(fld.fold_poly_trait_ref(ty), modifier),
 669         RegionTyParamBound(lifetime) => RegionTyParamBound(fld.fold_lifetime(lifetime)),
 670     }
 671 }
 672
 673 pub fn noop_fold_ty_param<T: Folder>(tp: TyParam, fld: &mut T) -> TyParam {
 674     let TyParam {attrs, id, ident, bounds, default, span} = tp;
 675     let attrs: Vec<_> = attrs.into();
 676     TyParam {
 677         attrs: attrs.into_iter()
 678             .flat_map(|x| fld.fold_attribute(x).into_iter())
 679             .collect::<Vec<_>>()
 680             .into(),
 681         id: fld.new_id(id),
 682         ident: fld.fold_ident(ident),
 683         bounds: fld.fold_bounds(bounds),
 684         default: default.map(|x| fld.fold_ty(x)),
 685         span: fld.new_span(span),
 686     }
 687 }
 688
 689 pub fn noop_fold_generic_param<T: Folder>(param: GenericParam, fld: &mut T) -> GenericParam {
 690     match param {
 691         GenericParam::Lifetime(l) => GenericParam::Lifetime(fld.fold_lifetime_def(l)),
 692         GenericParam::Type(t) => GenericParam::Type(fld.fold_ty_param(t)),
 693     }
 694 }
 695
 696 pub fn noop_fold_generic_params<T: Folder>(
 697     params: Vec<GenericParam>,
 698     fld: &mut T
 699 ) -> Vec<GenericParam> {
 700     params.move_map(|p| fld.fold_generic_param(p))
 701 }
 702
 703 pub fn noop_fold_label<T: Folder>(label: Label, fld: &mut T) -> Label {
 704     Label {
 705         ident: fld.fold_ident(label.ident),
 706         span: fld.new_span(label.span),
 707     }
 708 }
 709
 710 pub fn noop_fold_lifetime<T: Folder>(l: Lifetime, fld: &mut T) -> Lifetime {
 711     Lifetime {
 712         id: fld.new_id(l.id),
 713         ident: fld.fold_ident(l.ident),
 714         span: fld.new_span(l.span)
 715     }
 716 }
 717
 718 pub fn noop_fold_lifetime_def<T: Folder>(l: LifetimeDef, fld: &mut T)
 719                                          -> LifetimeDef {
 720     let attrs: Vec<_> = l.attrs.into();
 721     LifetimeDef {
 722         attrs: attrs.into_iter()
 723             .flat_map(|x| fld.fold_attribute(x).into_iter())
 724             .collect::<Vec<_>>()
 725             .into(),
 726         lifetime: fld.fold_lifetime(l.lifetime),
 727         bounds: fld.fold_lifetimes(l.bounds),
 728     }
 729 }
 730
 731 pub fn noop_fold_lifetimes<T: Folder>(lts: Vec<Lifetime>, fld: &mut T) -> Vec<Lifetime> {
 732     lts.move_map(|l| fld.fold_lifetime(l))
 733 }
 734
 735 pub fn noop_fold_lifetime_defs<T: Folder>(lts: Vec<LifetimeDef>, fld: &mut T)
 736                                           -> Vec<LifetimeDef> {
 737     lts.move_map(|l| fld.fold_lifetime_def(l))
 738 }
 739
 740 pub fn noop_fold_opt_lifetime<T: Folder>(o_lt: Option<Lifetime>, fld: &mut T)
 741                                          -> Option<Lifetime> {
 742     o_lt.map(|lt| fld.fold_lifetime(lt))
 743 }
 744
 745 pub fn noop_fold_generics<T: Folder>(Generics { params, where_clause, span }: Generics,
 746                                      fld: &mut T) -> Generics {
 747     Generics {
 748         params: fld.fold_generic_params(params),
 749         where_clause: fld.fold_where_clause(where_clause),
 750         span: fld.new_span(span),
 751     }
 752 }
 753
 754 pub fn noop_fold_where_clause<T: Folder>(
 755                               WhereClause {id, predicates, span}: WhereClause,
 756                               fld: &mut T)
 757                               -> WhereClause {
 758     WhereClause {
 759         id: fld.new_id(id),
 760         predicates: predicates.move_map(|predicate| {
 761             fld.fold_where_predicate(predicate)
 762         }),
 763         span,
 764     }
 765 }
 766
 767 pub fn noop_fold_where_predicate<T: Folder>(
 768                                  pred: WherePredicate,
 769                                  fld: &mut T)
 770                                  -> WherePredicate {
 771     match pred {
 772         ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate{bound_generic_params,
 773                                                                      bounded_ty,
 774                                                                      bounds,
 775                                                                      span}) => {
 776             ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
 777                 bound_generic_params: fld.fold_generic_params(bound_generic_params),
 778                 bounded_ty: fld.fold_ty(bounded_ty),
 779                 bounds: bounds.move_map(|x| fld.fold_ty_param_bound(x)),
 780                 span: fld.new_span(span)
 781             })
 782         }
 783         ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate{lifetime,
 784                                                                        bounds,
 785                                                                        span}) => {
 786             ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
 787                 span: fld.new_span(span),
 788                 lifetime: fld.fold_lifetime(lifetime),
 789                 bounds: bounds.move_map(|bound| fld.fold_lifetime(bound))
 790             })
 791         }
 792         ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{id,
 793                                                                lhs_ty,
 794                                                                rhs_ty,
 795                                                                span}) => {
 796             ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{
 797                 id: fld.new_id(id),
 798                 lhs_ty: fld.fold_ty(lhs_ty),
 799                 rhs_ty: fld.fold_ty(rhs_ty),
 800                 span: fld.new_span(span)
 801             })
 802         }
 803     }
 804 }
 805
 806 pub fn noop_fold_variant_data<T: Folder>(vdata: VariantData, fld: &mut T) -> VariantData {
 807     match vdata {
 808         ast::VariantData::Struct(fields, id) => {
 809             ast::VariantData::Struct(fields.move_map(|f| fld.fold_struct_field(f)),
 810                                      fld.new_id(id))
 811         }
 812         ast::VariantData::Tuple(fields, id) => {
 813             ast::VariantData::Tuple(fields.move_map(|f| fld.fold_struct_field(f)),
 814                                     fld.new_id(id))
 815         }
 816         ast::VariantData::Unit(id) => ast::VariantData::Unit(fld.new_id(id))
 817     }
 818 }
 819
 820 pub fn noop_fold_trait_ref<T: Folder>(p: TraitRef, fld: &mut T) -> TraitRef {
 821     let id = fld.new_id(p.ref_id);
 822     let TraitRef {
 823         path,
 824         ref_id: _,
 825     } = p;
 826     ast::TraitRef {
 827         path: fld.fold_path(path),
 828         ref_id: id,
 829     }
 830 }
 831
 832 pub fn noop_fold_poly_trait_ref<T: Folder>(p: PolyTraitRef, fld: &mut T) -> PolyTraitRef {
 833     ast::PolyTraitRef {
 834         bound_generic_params: fld.fold_generic_params(p.bound_generic_params),
 835         trait_ref: fld.fold_trait_ref(p.trait_ref),
 836         span: fld.new_span(p.span),
 837     }
 838 }
 839
 840 pub fn noop_fold_struct_field<T: Folder>(f: StructField, fld: &mut T) -> StructField {
 841     StructField {
 842         span: fld.new_span(f.span),
 843         id: fld.new_id(f.id),
 844         ident: f.ident.map(|ident| fld.fold_ident(ident)),
 845         vis: fld.fold_vis(f.vis),
 846         ty: fld.fold_ty(f.ty),
 847         attrs: fold_attrs(f.attrs, fld),
 848     }
 849 }
 850
 851 pub fn noop_fold_field<T: Folder>(f: Field, folder: &mut T) -> Field {
 852     Field {
 853         ident: respan(f.ident.span, folder.fold_ident(f.ident.node)),
 854         expr: folder.fold_expr(f.expr),
 855         span: folder.new_span(f.span),
 856         is_shorthand: f.is_shorthand,
 857         attrs: fold_thin_attrs(f.attrs, folder),
 858     }
 859 }
 860
 861 pub fn noop_fold_mt<T: Folder>(MutTy {ty, mutbl}: MutTy, folder: &mut T) -> MutTy {
 862     MutTy {
 863         ty: folder.fold_ty(ty),
 864         mutbl,
 865     }
 866 }
 867
 868 pub fn noop_fold_opt_bounds<T: Folder>(b: Option<TyParamBounds>, folder: &mut T)
 869                                        -> Option<TyParamBounds> {
 870     b.map(|bounds| folder.fold_bounds(bounds))
 871 }
 872
 873 fn noop_fold_bounds<T: Folder>(bounds: TyParamBounds, folder: &mut T)
 874                           -> TyParamBounds {
 875     bounds.move_map(|bound| folder.fold_ty_param_bound(bound))
 876 }
 877
 878 pub fn noop_fold_block<T: Folder>(b: P<Block>, folder: &mut T) -> P<Block> {
 879     b.map(|Block {id, stmts, rules, span, recovered}| Block {
 880         id: folder.new_id(id),
 881         stmts: stmts.move_flat_map(|s| folder.fold_stmt(s).into_iter()),
 882         rules,
 883         span: folder.new_span(span),
 884         recovered,
 885     })
 886 }
 887
 888 pub fn noop_fold_item_kind<T: Folder>(i: ItemKind, folder: &mut T) -> ItemKind {
 889     match i {
 890         ItemKind::ExternCrate(string) => ItemKind::ExternCrate(string),
 891         ItemKind::Use(use_tree) => {
 892             ItemKind::Use(use_tree.map(|tree| folder.fold_use_tree(tree)))
 893         }
 894         ItemKind::Static(t, m, e) => {
 895             ItemKind::Static(folder.fold_ty(t), m, folder.fold_expr(e))
 896         }
 897         ItemKind::Const(t, e) => {
 898             ItemKind::Const(folder.fold_ty(t), folder.fold_expr(e))
 899         }
 900         ItemKind::Fn(decl, unsafety, constness, abi, generics, body) => {
 901             let generics = folder.fold_generics(generics);
 902             let decl = folder.fold_fn_decl(decl);
 903             let body = folder.fold_block(body);
 904             ItemKind::Fn(decl, unsafety, constness, abi, generics, body)
 905         }
 906         ItemKind::Mod(m) => ItemKind::Mod(folder.fold_mod(m)),
 907         ItemKind::ForeignMod(nm) => ItemKind::ForeignMod(folder.fold_foreign_mod(nm)),
 908         ItemKind::GlobalAsm(ga) => ItemKind::GlobalAsm(folder.fold_global_asm(ga)),
 909         ItemKind::Ty(t, generics) => {
 910             ItemKind::Ty(folder.fold_ty(t), folder.fold_generics(generics))
 911         }
 912         ItemKind::Enum(enum_definition, generics) => {
 913             let generics = folder.fold_generics(generics);
 914             let variants = enum_definition.variants.move_map(|x| folder.fold_variant(x));
 915             ItemKind::Enum(ast::EnumDef { variants: variants }, generics)
 916         }
 917         ItemKind::Struct(struct_def, generics) => {
 918             let generics = folder.fold_generics(generics);
 919             ItemKind::Struct(folder.fold_variant_data(struct_def), generics)
 920         }
 921         ItemKind::Union(struct_def, generics) => {
 922             let generics = folder.fold_generics(generics);
 923             ItemKind::Union(folder.fold_variant_data(struct_def), generics)
 924         }
 925         ItemKind::Impl(unsafety,
 926                        polarity,
 927                        defaultness,
 928                        generics,
 929                        ifce,
 930                        ty,
 931                        impl_items) => ItemKind::Impl(
 932             unsafety,
 933             polarity,
 934             defaultness,
 935             folder.fold_generics(generics),
 936             ifce.map(|trait_ref| folder.fold_trait_ref(trait_ref.clone())),
 937             folder.fold_ty(ty),
 938             impl_items.move_flat_map(|item| folder.fold_impl_item(item)),
 939         ),
 940         ItemKind::Trait(is_auto, unsafety, generics, bounds, items) => ItemKind::Trait(
 941             is_auto,
 942             unsafety,
 943             folder.fold_generics(generics),
 944             folder.fold_bounds(bounds),
 945             items.move_flat_map(|item| folder.fold_trait_item(item)),
 946         ),
 947         ItemKind::TraitAlias(generics, bounds) => ItemKind::TraitAlias(
 948             folder.fold_generics(generics),
 949             folder.fold_bounds(bounds)),
 950         ItemKind::Mac(m) => ItemKind::Mac(folder.fold_mac(m)),
 951         ItemKind::MacroDef(def) => ItemKind::MacroDef(folder.fold_macro_def(def)),
 952     }
 953 }
 954
 955 pub fn noop_fold_trait_item<T: Folder>(i: TraitItem, folder: &mut T)
 956                                        -> SmallVector<TraitItem> {
 957     SmallVector::one(TraitItem {
 958         id: folder.new_id(i.id),
 959         ident: folder.fold_ident(i.ident),
 960         attrs: fold_attrs(i.attrs, folder),
 961         generics: folder.fold_generics(i.generics),
 962         node: match i.node {
 963             TraitItemKind::Const(ty, default) => {
 964                 TraitItemKind::Const(folder.fold_ty(ty),
 965                                default.map(|x| folder.fold_expr(x)))
 966             }
 967             TraitItemKind::Method(sig, body) => {
 968                 TraitItemKind::Method(noop_fold_method_sig(sig, folder),
 969                                 body.map(|x| folder.fold_block(x)))
 970             }
 971             TraitItemKind::Type(bounds, default) => {
 972                 TraitItemKind::Type(folder.fold_bounds(bounds),
 973                               default.map(|x| folder.fold_ty(x)))
 974             }
 975             ast::TraitItemKind::Macro(mac) => {
 976                 TraitItemKind::Macro(folder.fold_mac(mac))
 977             }
 978         },
 979         span: folder.new_span(i.span),
 980         tokens: i.tokens,
 981     })
 982 }
 983
 984 pub fn noop_fold_impl_item<T: Folder>(i: ImplItem, folder: &mut T)
 985                                       -> SmallVector<ImplItem> {
 986     SmallVector::one(ImplItem {
 987         id: folder.new_id(i.id),
 988         vis: folder.fold_vis(i.vis),
 989         ident: folder.fold_ident(i.ident),
 990         attrs: fold_attrs(i.attrs, folder),
 991         generics: folder.fold_generics(i.generics),
 992         defaultness: i.defaultness,
 993         node: match i.node  {
 994             ast::ImplItemKind::Const(ty, expr) => {
 995                 ast::ImplItemKind::Const(folder.fold_ty(ty), folder.fold_expr(expr))
 996             }
 997             ast::ImplItemKind::Method(sig, body) => {
 998                 ast::ImplItemKind::Method(noop_fold_method_sig(sig, folder),
 999                                folder.fold_block(body))
1000             }
1001             ast::ImplItemKind::Type(ty) => ast::ImplItemKind::Type(folder.fold_ty(ty)),
1002             ast::ImplItemKind::Macro(mac) => ast::ImplItemKind::Macro(folder.fold_mac(mac))
1003         },
1004         span: folder.new_span(i.span),
1005         tokens: i.tokens,
1006     })
1007 }
1008
1009 pub fn noop_fold_mod<T: Folder>(Mod {inner, items}: Mod, folder: &mut T) -> Mod {
1010     Mod {
1011         inner: folder.new_span(inner),
1012         items: items.move_flat_map(|x| folder.fold_item(x)),
1013     }
1014 }
1015
1016 pub fn noop_fold_crate<T: Folder>(Crate {module, attrs, span}: Crate,
1017                                   folder: &mut T) -> Crate {
1018     let mut items = folder.fold_item(P(ast::Item {
1019         ident: keywords::Invalid.ident(),
1020         attrs,
1021         id: ast::DUMMY_NODE_ID,
1022         vis: ast::Visibility::Public,
1023         span,
1024         node: ast::ItemKind::Mod(module),
1025         tokens: None,
1026     })).into_iter();
1027
1028     let (module, attrs, span) = match items.next() {
1029         Some(item) => {
1030             assert!(items.next().is_none(),
1031                     "a crate cannot expand to more than one item");
1032             item.and_then(|ast::Item { attrs, span, node, .. }| {
1033                 match node {
1034                     ast::ItemKind::Mod(m) => (m, attrs, span),
1035                     _ => panic!("fold converted a module to not a module"),
1036                 }
1037             })
1038         }
1039         None => (ast::Mod {
1040             inner: span,
1041             items: vec![],
1042         }, vec![], span)
1043     };
1044
1045     Crate {
1046         module,
1047         attrs,
1048         span,
1049     }
1050 }
1051
1052 // fold one item into possibly many items
1053 pub fn noop_fold_item<T: Folder>(i: P<Item>, folder: &mut T) -> SmallVector<P<Item>> {
1054     SmallVector::one(i.map(|i| folder.fold_item_simple(i)))
1055 }
1056
1057 // fold one item into exactly one item
1058 pub fn noop_fold_item_simple<T: Folder>(Item {id, ident, attrs, node, vis, span, tokens}: Item,
1059                                         folder: &mut T) -> Item {
1060     Item {
1061         id: folder.new_id(id),
1062         vis: folder.fold_vis(vis),
1063         ident: folder.fold_ident(ident),
1064         attrs: fold_attrs(attrs, folder),
1065         node: folder.fold_item_kind(node),
1066         span: folder.new_span(span),
1067
1068         // FIXME: if this is replaced with a call to `folder.fold_tts` it causes
1069         //        an ICE during resolve... odd!
1070         tokens,
1071     }
1072 }
1073
1074 pub fn noop_fold_foreign_item<T: Folder>(ni: ForeignItem, folder: &mut T) -> ForeignItem {
1075     ForeignItem {
1076         id: folder.new_id(ni.id),
1077         vis: folder.fold_vis(ni.vis),
1078         ident: folder.fold_ident(ni.ident),
1079         attrs: fold_attrs(ni.attrs, folder),
1080         node: match ni.node {
1081             ForeignItemKind::Fn(fdec, generics) => {
1082                 ForeignItemKind::Fn(folder.fold_fn_decl(fdec), folder.fold_generics(generics))
1083             }
1084             ForeignItemKind::Static(t, m) => {
1085                 ForeignItemKind::Static(folder.fold_ty(t), m)
1086             }
1087             ForeignItemKind::Ty => ForeignItemKind::Ty,
1088         },
1089         span: folder.new_span(ni.span)
1090     }
1091 }
1092
1093 pub fn noop_fold_method_sig<T: Folder>(sig: MethodSig, folder: &mut T) -> MethodSig {
1094     MethodSig {
1095         abi: sig.abi,
1096         unsafety: sig.unsafety,
1097         constness: sig.constness,
1098         decl: folder.fold_fn_decl(sig.decl)
1099     }
1100 }
1101
1102 pub fn noop_fold_pat<T: Folder>(p: P<Pat>, folder: &mut T) -> P<Pat> {
1103     p.map(|Pat {id, node, span}| Pat {
1104         id: folder.new_id(id),
1105         node: match node {
1106             PatKind::Wild => PatKind::Wild,
1107             PatKind::Ident(binding_mode, pth1, sub) => {
1108                 PatKind::Ident(binding_mode,
1109                         Spanned{span: folder.new_span(pth1.span),
1110                                 node: folder.fold_ident(pth1.node)},
1111                         sub.map(|x| folder.fold_pat(x)))
1112             }
1113             PatKind::Lit(e) => PatKind::Lit(folder.fold_expr(e)),
1114             PatKind::TupleStruct(pth, pats, ddpos) => {
1115                 PatKind::TupleStruct(folder.fold_path(pth),
1116                         pats.move_map(|x| folder.fold_pat(x)), ddpos)
1117             }
1118             PatKind::Path(opt_qself, pth) => {
1119                 let opt_qself = opt_qself.map(|qself| {
1120                     QSelf { ty: folder.fold_ty(qself.ty), position: qself.position }
1121                 });
1122                 PatKind::Path(opt_qself, folder.fold_path(pth))
1123             }
1124             PatKind::Struct(pth, fields, etc) => {
1125                 let pth = folder.fold_path(pth);
1126                 let fs = fields.move_map(|f| {
1127                     Spanned { span: folder.new_span(f.span),
1128                               node: ast::FieldPat {
1129                                   ident: folder.fold_ident(f.node.ident),
1130                                   pat: folder.fold_pat(f.node.pat),
1131                                   is_shorthand: f.node.is_shorthand,
1132                                   attrs: fold_attrs(f.node.attrs.into(), folder).into()
1133                               }}
1134                 });
1135                 PatKind::Struct(pth, fs, etc)
1136             }
1137             PatKind::Tuple(elts, ddpos) => {
1138                 PatKind::Tuple(elts.move_map(|x| folder.fold_pat(x)), ddpos)
1139             }
1140             PatKind::Box(inner) => PatKind::Box(folder.fold_pat(inner)),
1141             PatKind::Ref(inner, mutbl) => PatKind::Ref(folder.fold_pat(inner), mutbl),
1142             PatKind::Range(e1, e2, end) => {
1143                 PatKind::Range(folder.fold_expr(e1),
1144                                folder.fold_expr(e2),
1145                                folder.fold_range_end(end))
1146             },
1147             PatKind::Slice(before, slice, after) => {
1148                 PatKind::Slice(before.move_map(|x| folder.fold_pat(x)),
1149                        slice.map(|x| folder.fold_pat(x)),
1150                        after.move_map(|x| folder.fold_pat(x)))
1151             }
1152             PatKind::Mac(mac) => PatKind::Mac(folder.fold_mac(mac))
1153         },
1154         span: folder.new_span(span)
1155     })
1156 }
1157
1158 pub fn noop_fold_range_end<T: Folder>(end: RangeEnd, _folder: &mut T) -> RangeEnd {
1159     end
1160 }
1161
1162 pub fn noop_fold_expr<T: Folder>(Expr {id, node, span, attrs}: Expr, folder: &mut T) -> Expr {
1163     Expr {
1164         node: match node {
1165             ExprKind::Box(e) => {
1166                 ExprKind::Box(folder.fold_expr(e))
1167             }
1168             ExprKind::InPlace(p, e) => {
1169                 ExprKind::InPlace(folder.fold_expr(p), folder.fold_expr(e))
1170             }
1171             ExprKind::Array(exprs) => {
1172                 ExprKind::Array(folder.fold_exprs(exprs))
1173             }
1174             ExprKind::Repeat(expr, count) => {
1175                 ExprKind::Repeat(folder.fold_expr(expr), folder.fold_expr(count))
1176             }
1177             ExprKind::Tup(exprs) => ExprKind::Tup(folder.fold_exprs(exprs)),
1178             ExprKind::Call(f, args) => {
1179                 ExprKind::Call(folder.fold_expr(f),
1180                          folder.fold_exprs(args))
1181             }
1182             ExprKind::MethodCall(seg, args) => {
1183                 ExprKind::MethodCall(
1184                     PathSegment {
1185                         identifier: folder.fold_ident(seg.identifier),
1186                         span: folder.new_span(seg.span),
1187                         parameters: seg.parameters.map(|ps| {
1188                             ps.map(|ps| folder.fold_path_parameters(ps))
1189                         }),
1190                     },
1191                     folder.fold_exprs(args))
1192             }
1193             ExprKind::Binary(binop, lhs, rhs) => {
1194                 ExprKind::Binary(binop,
1195                         folder.fold_expr(lhs),
1196                         folder.fold_expr(rhs))
1197             }
1198             ExprKind::Unary(binop, ohs) => {
1199                 ExprKind::Unary(binop, folder.fold_expr(ohs))
1200             }
1201             ExprKind::Lit(l) => ExprKind::Lit(l),
1202             ExprKind::Cast(expr, ty) => {
1203                 ExprKind::Cast(folder.fold_expr(expr), folder.fold_ty(ty))
1204             }
1205             ExprKind::Type(expr, ty) => {
1206                 ExprKind::Type(folder.fold_expr(expr), folder.fold_ty(ty))
1207             }
1208             ExprKind::AddrOf(m, ohs) => ExprKind::AddrOf(m, folder.fold_expr(ohs)),
1209             ExprKind::If(cond, tr, fl) => {
1210                 ExprKind::If(folder.fold_expr(cond),
1211                        folder.fold_block(tr),
1212                        fl.map(|x| folder.fold_expr(x)))
1213             }
1214             ExprKind::IfLet(pat, expr, tr, fl) => {
1215                 ExprKind::IfLet(folder.fold_pat(pat),
1216                           folder.fold_expr(expr),
1217                           folder.fold_block(tr),
1218                           fl.map(|x| folder.fold_expr(x)))
1219             }
1220             ExprKind::While(cond, body, opt_label) => {
1221                 ExprKind::While(folder.fold_expr(cond),
1222                           folder.fold_block(body),
1223                           opt_label.map(|label| folder.fold_label(label)))
1224             }
1225             ExprKind::WhileLet(pat, expr, body, opt_label) => {
1226                 ExprKind::WhileLet(folder.fold_pat(pat),
1227                              folder.fold_expr(expr),
1228                              folder.fold_block(body),
1229                              opt_label.map(|label| folder.fold_label(label)))
1230             }
1231             ExprKind::ForLoop(pat, iter, body, opt_label) => {
1232                 ExprKind::ForLoop(folder.fold_pat(pat),
1233                             folder.fold_expr(iter),
1234                             folder.fold_block(body),
1235                             opt_label.map(|label| folder.fold_label(label)))
1236             }
1237             ExprKind::Loop(body, opt_label) => {
1238                 ExprKind::Loop(folder.fold_block(body),
1239                                opt_label.map(|label| folder.fold_label(label)))
1240             }
1241             ExprKind::Match(expr, arms) => {
1242                 ExprKind::Match(folder.fold_expr(expr),
1243                           arms.move_map(|x| folder.fold_arm(x)))
1244             }
1245             ExprKind::Closure(capture_clause, movability, decl, body, span) => {
1246                 ExprKind::Closure(capture_clause,
1247                                   movability,
1248                                   folder.fold_fn_decl(decl),
1249                                   folder.fold_expr(body),
1250                                   folder.new_span(span))
1251             }
1252             ExprKind::Block(blk) => ExprKind::Block(folder.fold_block(blk)),
1253             ExprKind::Assign(el, er) => {
1254                 ExprKind::Assign(folder.fold_expr(el), folder.fold_expr(er))
1255             }
1256             ExprKind::AssignOp(op, el, er) => {
1257                 ExprKind::AssignOp(op,
1258                             folder.fold_expr(el),
1259                             folder.fold_expr(er))
1260             }
1261             ExprKind::Field(el, ident) => {
1262                 ExprKind::Field(folder.fold_expr(el),
1263                           respan(folder.new_span(ident.span),
1264                                  folder.fold_ident(ident.node)))
1265             }
1266             ExprKind::TupField(el, ident) => {
1267                 ExprKind::TupField(folder.fold_expr(el),
1268                              respan(folder.new_span(ident.span),
1269                                     folder.fold_usize(ident.node)))
1270             }
1271             ExprKind::Index(el, er) => {
1272                 ExprKind::Index(folder.fold_expr(el), folder.fold_expr(er))
1273             }
1274             ExprKind::Range(e1, e2, lim) => {
1275                 ExprKind::Range(e1.map(|x| folder.fold_expr(x)),
1276                                 e2.map(|x| folder.fold_expr(x)),
1277                                 lim)
1278             }
1279             ExprKind::Path(qself, path) => {
1280                 let qself = qself.map(|QSelf { ty, position }| {
1281                     QSelf {
1282                         ty: folder.fold_ty(ty),
1283                         position,
1284                     }
1285                 });
1286                 ExprKind::Path(qself, folder.fold_path(path))
1287             }
1288             ExprKind::Break(opt_label, opt_expr) => {
1289                 ExprKind::Break(opt_label.map(|label| folder.fold_label(label)),
1290                                 opt_expr.map(|e| folder.fold_expr(e)))
1291             }
1292             ExprKind::Continue(opt_label) => {
1293                 ExprKind::Continue(opt_label.map(|label| folder.fold_label(label)))
1294             }
1295             ExprKind::Ret(e) => ExprKind::Ret(e.map(|x| folder.fold_expr(x))),
1296             ExprKind::InlineAsm(asm) => ExprKind::InlineAsm(asm.map(|asm| {
1297                 InlineAsm {
1298                     inputs: asm.inputs.move_map(|(c, input)| {
1299                         (c, folder.fold_expr(input))
1300                     }),
1301                     outputs: asm.outputs.move_map(|out| {
1302                         InlineAsmOutput {
1303                             constraint: out.constraint,
1304                             expr: folder.fold_expr(out.expr),
1305                             is_rw: out.is_rw,
1306                             is_indirect: out.is_indirect,
1307                         }
1308                     }),
1309                     ..asm
1310                 }
1311             })),
1312             ExprKind::Mac(mac) => ExprKind::Mac(folder.fold_mac(mac)),
1313             ExprKind::Struct(path, fields, maybe_expr) => {
1314                 ExprKind::Struct(folder.fold_path(path),
1315                         fields.move_map(|x| folder.fold_field(x)),
1316                         maybe_expr.map(|x| folder.fold_expr(x)))
1317             },
1318             ExprKind::Paren(ex) => {
1319                 let sub_expr = folder.fold_expr(ex);
1320                 return Expr {
1321                     // Nodes that are equal modulo `Paren` sugar no-ops should have the same ids.
1322                     id: sub_expr.id,
1323                     node: ExprKind::Paren(sub_expr),
1324                     span: folder.new_span(span),
1325                     attrs: fold_attrs(attrs.into(), folder).into(),
1326                 };
1327             }
1328             ExprKind::Yield(ex) => ExprKind::Yield(ex.map(|x| folder.fold_expr(x))),
1329             ExprKind::Try(ex) => ExprKind::Try(folder.fold_expr(ex)),
1330             ExprKind::Catch(body) => ExprKind::Catch(folder.fold_block(body)),
1331         },
1332         id: folder.new_id(id),
1333         span: folder.new_span(span),
1334         attrs: fold_attrs(attrs.into(), folder).into(),
1335     }
1336 }
1337
1338 pub fn noop_fold_opt_expr<T: Folder>(e: P<Expr>, folder: &mut T) -> Option<P<Expr>> {
1339     Some(folder.fold_expr(e))
1340 }
1341
1342 pub fn noop_fold_exprs<T: Folder>(es: Vec<P<Expr>>, folder: &mut T) -> Vec<P<Expr>> {
1343     es.move_flat_map(|e| folder.fold_opt_expr(e))
1344 }
1345
1346 pub fn noop_fold_stmt<T: Folder>(Stmt {node, span, id}: Stmt, folder: &mut T) -> SmallVector<Stmt> {
1347     let id = folder.new_id(id);
1348     let span = folder.new_span(span);
1349     noop_fold_stmt_kind(node, folder).into_iter().map(|node| {
1350         Stmt { id: id, node: node, span: span }
1351     }).collect()
1352 }
1353
1354 pub fn noop_fold_stmt_kind<T: Folder>(node: StmtKind, folder: &mut T) -> SmallVector<StmtKind> {
1355     match node {
1356         StmtKind::Local(local) => SmallVector::one(StmtKind::Local(folder.fold_local(local))),
1357         StmtKind::Item(item) => folder.fold_item(item).into_iter().map(StmtKind::Item).collect(),
1358         StmtKind::Expr(expr) => {
1359             folder.fold_opt_expr(expr).into_iter().map(StmtKind::Expr).collect()
1360         }
1361         StmtKind::Semi(expr) => {
1362             folder.fold_opt_expr(expr).into_iter().map(StmtKind::Semi).collect()
1363         }
1364         StmtKind::Mac(mac) => SmallVector::one(StmtKind::Mac(mac.map(|(mac, semi, attrs)| {
1365             (folder.fold_mac(mac), semi, fold_attrs(attrs.into(), folder).into())
1366         }))),
1367     }
1368 }
1369
1370 pub fn noop_fold_vis<T: Folder>(vis: Visibility, folder: &mut T) -> Visibility {
1371     match vis {
1372         Visibility::Restricted { path, id } => Visibility::Restricted {
1373             path: path.map(|path| folder.fold_path(path)),
1374             id: folder.new_id(id)
1375         },
1376         _ => vis,
1377     }
1378 }
1379
1380 #[cfg(test)]
1381 mod tests {
1382     use std::io;
1383     use ast::{self, Ident};
1384     use util::parser_testing::{string_to_crate, matches_codepattern};
1385     use print::pprust;
1386     use fold;
1387     use super::*;
1388
1389     // this version doesn't care about getting comments or docstrings in.
1390     fn fake_print_crate(s: &mut pprust::State,
1391                         krate: &ast::Crate) -> io::Result<()> {
1392         s.print_mod(&krate.module, &krate.attrs)
1393     }
1394
1395     // change every identifier to "zz"
1396     struct ToZzIdentFolder;
1397
1398     impl Folder for ToZzIdentFolder {
1399         fn fold_ident(&mut self, _: ast::Ident) -> ast::Ident {
1400             Ident::from_str("zz")
1401         }
1402         fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
1403             fold::noop_fold_mac(mac, self)
1404         }
1405     }
1406
1407     // maybe add to expand.rs...
1408     macro_rules! assert_pred {
1409         ($pred:expr, $predname:expr, $a:expr , $b:expr) => (
1410             {
1411                 let pred_val = $pred;
1412                 let a_val = $a;
1413                 let b_val = $b;
1414                 if !(pred_val(&a_val, &b_val)) {
1415                     panic!("expected args satisfying {}, got {} and {}",
1416                           $predname, a_val, b_val);
1417                 }
1418             }
1419         )
1420     }
1421
1422     // make sure idents get transformed everywhere
1423     #[test] fn ident_transformation () {
1424         let mut zz_fold = ToZzIdentFolder;
1425         let ast = string_to_crate(
1426             "#[a] mod b {fn c (d : e, f : g) {h!(i,j,k);l;m}}".to_string());
1427         let folded_crate = zz_fold.fold_crate(ast);
1428         assert_pred!(
1429             matches_codepattern,
1430             "matches_codepattern",
1431             pprust::to_string(|s| fake_print_crate(s, &folded_crate)),
1432             "#[zz]mod zz{fn zz(zz:zz,zz:zz){zz!(zz,zz,zz);zz;zz}}".to_string());
1433     }
1434
1435     // even inside macro defs....
1436     #[test] fn ident_transformation_in_defs () {
1437         let mut zz_fold = ToZzIdentFolder;
1438         let ast = string_to_crate(
1439             "macro_rules! a {(b $c:expr $(d $e:token)f+ => \
1440              (g $(d $d $e)+))} ".to_string());
1441         let folded_crate = zz_fold.fold_crate(ast);
1442         assert_pred!(
1443             matches_codepattern,
1444             "matches_codepattern",
1445             pprust::to_string(|s| fake_print_crate(s, &folded_crate)),
1446             "macro_rules! zz((zz$zz:zz$(zz $zz:zz)zz+=>(zz$(zz$zz$zz)+)));".to_string());
1447     }
1448 }