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