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