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