src/libsyntax/fold.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! A Folder represents an AST->AST fold; it accepts an AST piece,
  12 //! and returns a piece of the same type. So, for instance, macro
  13 //! expansion is a Folder that walks over an AST and produces another
  14 //! AST.
  15 //!
  16 //! Note: using a Folder (other than the MacroExpander Folder) on
  17 //! an AST before macro expansion is probably a bad idea. For instance,
  18 //! a folder renaming item names in a module will miss all of those
  19 //! that are created by the expansion of a macro.
  20
  21 use ast::*;
  22 use ast;
  23 use syntax_pos::Span;
  24 use codemap::{Spanned, respan};
  25 use parse::token::{self, Token};
  26 use ptr::P;
  27 use symbol::keywords;
  28 use tokenstream::*;
  29 use util::small_vector::SmallVector;
  30 use util::move_map::MoveMap;
  31
  32 use rustc_data_structures::sync::Lrc;
  33
  34 pub trait Folder : Sized {
  35     // Any additions to this trait should happen in form
  36     // of a call to a public `noop_*` function that only calls
  37     // out to the folder again, not other `noop_*` functions.
  38     //
  39     // This is a necessary API workaround to the problem of not
  40     // being able to call out to the super default method
  41     // in an overridden default method.
  42
  43     fn fold_crate(&mut self, c: Crate) -> Crate {
  44         noop_fold_crate(c, self)
  45     }
  46
  47     fn fold_meta_items(&mut self, meta_items: Vec<MetaItem>) -> Vec<MetaItem> {
  48         noop_fold_meta_items(meta_items, self)
  49     }
  50
  51     fn fold_meta_list_item(&mut self, list_item: NestedMetaItem) -> NestedMetaItem {
  52         noop_fold_meta_list_item(list_item, self)
  53     }
  54
  55     fn fold_meta_item(&mut self, meta_item: MetaItem) -> MetaItem {
  56         noop_fold_meta_item(meta_item, self)
  57     }
  58
  59     fn fold_use_tree(&mut self, use_tree: UseTree) -> UseTree {
  60         noop_fold_use_tree(use_tree, self)
  61     }
  62
  63     fn fold_foreign_item(&mut self, ni: ForeignItem) -> SmallVector<ForeignItem> {
  64         noop_fold_foreign_item(ni, self)
  65     }
  66
  67     fn fold_foreign_item_simple(&mut self, ni: ForeignItem) -> ForeignItem {
  68         noop_fold_foreign_item_simple(ni, self)
  69     }
  70
  71     fn fold_item(&mut self, i: P<Item>) -> SmallVector<P<Item>> {
  72         noop_fold_item(i, self)
  73     }
  74
  75     fn fold_item_simple(&mut self, i: Item) -> Item {
  76         noop_fold_item_simple(i, self)
  77     }
  78
  79     fn fold_struct_field(&mut self, sf: StructField) -> StructField {
  80         noop_fold_struct_field(sf, self)
  81     }
  82
  83     fn fold_item_kind(&mut self, i: ItemKind) -> ItemKind {
  84         noop_fold_item_kind(i, self)
  85     }
  86
  87     fn fold_trait_item(&mut self, i: TraitItem) -> SmallVector<TraitItem> {
  88         noop_fold_trait_item(i, self)
  89     }
  90
  91     fn fold_impl_item(&mut self, i: ImplItem) -> SmallVector<ImplItem> {
  92         noop_fold_impl_item(i, self)
  93     }
  94
  95     fn fold_fn_decl(&mut self, d: P<FnDecl>) -> P<FnDecl> {
  96         noop_fold_fn_decl(d, self)
  97     }
  98
  99     fn fold_block(&mut self, b: P<Block>) -> P<Block> {
 100         noop_fold_block(b, self)
 101     }
 102
 103     fn fold_stmt(&mut self, s: Stmt) -> SmallVector<Stmt> {
 104         noop_fold_stmt(s, self)
 105     }
 106
 107     fn fold_arm(&mut self, a: Arm) -> Arm {
 108         noop_fold_arm(a, self)
 109     }
 110
 111     fn fold_pat(&mut self, p: P<Pat>) -> P<Pat> {
 112         noop_fold_pat(p, self)
 113     }
 114
 115     fn fold_expr(&mut self, e: P<Expr>) -> P<Expr> {
 116         e.map(|e| noop_fold_expr(e, self))
 117     }
 118
 119     fn fold_range_end(&mut self, re: RangeEnd) -> RangeEnd {
 120         noop_fold_range_end(re, self)
 121     }
 122
 123     fn fold_opt_expr(&mut self, e: P<Expr>) -> Option<P<Expr>> {
 124         noop_fold_opt_expr(e, self)
 125     }
 126
 127     fn fold_exprs(&mut self, es: Vec<P<Expr>>) -> Vec<P<Expr>> {
 128         noop_fold_exprs(es, self)
 129     }
 130
 131     fn fold_ty(&mut self, t: P<Ty>) -> P<Ty> {
 132         noop_fold_ty(t, self)
 133     }
 134
 135     fn fold_ty_binding(&mut self, t: TypeBinding) -> TypeBinding {
 136         noop_fold_ty_binding(t, self)
 137     }
 138
 139     fn fold_mod(&mut self, m: Mod) -> Mod {
 140         noop_fold_mod(m, self)
 141     }
 142
 143     fn fold_foreign_mod(&mut self, nm: ForeignMod) -> ForeignMod {
 144         noop_fold_foreign_mod(nm, self)
 145     }
 146
 147     fn fold_global_asm(&mut self, ga: P<GlobalAsm>) -> P<GlobalAsm> {
 148         noop_fold_global_asm(ga, self)
 149     }
 150
 151     fn fold_variant(&mut self, v: Variant) -> Variant {
 152         noop_fold_variant(v, self)
 153     }
 154
 155     fn fold_ident(&mut self, i: Ident) -> Ident {
 156         noop_fold_ident(i, self)
 157     }
 158
 159     fn fold_usize(&mut self, i: usize) -> usize {
 160         noop_fold_usize(i, self)
 161     }
 162
 163     fn fold_path(&mut self, p: Path) -> Path {
 164         noop_fold_path(p, self)
 165     }
 166
 167     fn fold_path_parameters(&mut self, p: PathParameters) -> PathParameters {
 168         noop_fold_path_parameters(p, self)
 169     }
 170
 171     fn fold_angle_bracketed_parameter_data(&mut self, p: AngleBracketedParameterData)
 172                                            -> AngleBracketedParameterData
 173     {
 174         noop_fold_angle_bracketed_parameter_data(p, self)
 175     }
 176
 177     fn fold_parenthesized_parameter_data(&mut self, p: ParenthesizedParameterData)
 178                                          -> ParenthesizedParameterData
 179     {
 180         noop_fold_parenthesized_parameter_data(p, self)
 181     }
 182
 183     fn fold_local(&mut self, l: P<Local>) -> P<Local> {
 184         noop_fold_local(l, self)
 185     }
 186
 187     fn fold_mac(&mut self, _mac: Mac) -> Mac {
 188         panic!("fold_mac disabled by default");
 189         // NB: see note about macros above.
 190         // if you really want a folder that
 191         // works on macros, use this
 192         // definition in your trait impl:
 193         // fold::noop_fold_mac(_mac, self)
 194     }
 195
 196     fn fold_macro_def(&mut self, def: MacroDef) -> MacroDef {
 197         noop_fold_macro_def(def, self)
 198     }
 199
 200     fn fold_label(&mut self, label: Label) -> Label {
 201         noop_fold_label(label, self)
 202     }
 203
 204     fn fold_lifetime(&mut self, l: Lifetime) -> Lifetime {
 205         noop_fold_lifetime(l, self)
 206     }
 207
 208     fn fold_lifetime_def(&mut self, l: LifetimeDef) -> LifetimeDef {
 209         noop_fold_lifetime_def(l, self)
 210     }
 211
 212     fn fold_attribute(&mut self, at: Attribute) -> Option<Attribute> {
 213         noop_fold_attribute(at, self)
 214     }
 215
 216     fn fold_arg(&mut self, a: Arg) -> Arg {
 217         noop_fold_arg(a, self)
 218     }
 219
 220     fn fold_generics(&mut self, generics: Generics) -> Generics {
 221         noop_fold_generics(generics, self)
 222     }
 223
 224     fn fold_trait_ref(&mut self, p: TraitRef) -> TraitRef {
 225         noop_fold_trait_ref(p, self)
 226     }
 227
 228     fn fold_poly_trait_ref(&mut self, p: PolyTraitRef) -> PolyTraitRef {
 229         noop_fold_poly_trait_ref(p, self)
 230     }
 231
 232     fn fold_variant_data(&mut self, vdata: VariantData) -> VariantData {
 233         noop_fold_variant_data(vdata, self)
 234     }
 235
 236     fn fold_lifetimes(&mut self, lts: Vec<Lifetime>) -> Vec<Lifetime> {
 237         noop_fold_lifetimes(lts, self)
 238     }
 239
 240     fn fold_lifetime_defs(&mut self, lts: Vec<LifetimeDef>) -> Vec<LifetimeDef> {
 241         noop_fold_lifetime_defs(lts, self)
 242     }
 243
 244     fn fold_ty_param(&mut self, tp: TyParam) -> TyParam {
 245         noop_fold_ty_param(tp, self)
 246     }
 247
 248     fn fold_generic_param(&mut self, param: GenericParam) -> GenericParam {
 249         noop_fold_generic_param(param, self)
 250     }
 251
 252     fn fold_generic_params(&mut self, params: Vec<GenericParam>) -> Vec<GenericParam> {
 253         noop_fold_generic_params(params, self)
 254     }
 255
 256     fn fold_tt(&mut self, tt: TokenTree) -> TokenTree {
 257         noop_fold_tt(tt, self)
 258     }
 259
 260     fn fold_tts(&mut self, tts: TokenStream) -> TokenStream {
 261         noop_fold_tts(tts, self)
 262     }
 263
 264     fn fold_token(&mut self, t: token::Token) -> token::Token {
 265         noop_fold_token(t, self)
 266     }
 267
 268     fn fold_interpolated(&mut self, nt: token::Nonterminal) -> token::Nonterminal {
 269         noop_fold_interpolated(nt, self)
 270     }
 271
 272     fn fold_opt_lifetime(&mut self, o_lt: Option<Lifetime>) -> Option<Lifetime> {
 273         noop_fold_opt_lifetime(o_lt, self)
 274     }
 275
 276     fn fold_opt_bounds(&mut self, b: Option<TyParamBounds>)
 277                        -> Option<TyParamBounds> {
 278         noop_fold_opt_bounds(b, self)
 279     }
 280
 281     fn fold_bounds(&mut self, b: TyParamBounds)
 282                        -> TyParamBounds {
 283         noop_fold_bounds(b, self)
 284     }
 285
 286     fn fold_ty_param_bound(&mut self, tpb: TyParamBound) -> TyParamBound {
 287         noop_fold_ty_param_bound(tpb, self)
 288     }
 289
 290     fn fold_mt(&mut self, mt: MutTy) -> MutTy {
 291         noop_fold_mt(mt, self)
 292     }
 293
 294     fn fold_field(&mut self, field: Field) -> Field {
 295         noop_fold_field(field, self)
 296     }
 297
 298     fn fold_where_clause(&mut self, where_clause: WhereClause)
 299                          -> WhereClause {
 300         noop_fold_where_clause(where_clause, self)
 301     }
 302
 303     fn fold_where_predicate(&mut self, where_predicate: WherePredicate)
 304                             -> WherePredicate {
 305         noop_fold_where_predicate(where_predicate, self)
 306     }
 307
 308     fn fold_vis(&mut self, vis: Visibility) -> Visibility {
 309         noop_fold_vis(vis, self)
 310     }
 311
 312     fn new_id(&mut self, i: NodeId) -> NodeId {
 313         i
 314     }
 315
 316     fn new_span(&mut self, sp: Span) -> Span {
 317         sp
 318     }
 319 }
 320
 321 pub fn noop_fold_meta_items<T: Folder>(meta_items: Vec<MetaItem>, fld: &mut T) -> Vec<MetaItem> {
 322     meta_items.move_map(|x| fld.fold_meta_item(x))
 323 }
 324
 325 pub fn noop_fold_use_tree<T: Folder>(use_tree: UseTree, fld: &mut T) -> UseTree {
 326     UseTree {
 327         span: fld.new_span(use_tree.span),
 328         prefix: fld.fold_path(use_tree.prefix),
 329         kind: match use_tree.kind {
 330             UseTreeKind::Simple(rename) =>
 331                 UseTreeKind::Simple(rename.map(|ident| fld.fold_ident(ident))),
 332             UseTreeKind::Glob => UseTreeKind::Glob,
 333             UseTreeKind::Nested(items) => UseTreeKind::Nested(items.move_map(|(tree, id)| {
 334                 (fld.fold_use_tree(tree), fld.new_id(id))
 335             })),
 336         },
 337     }
 338 }
 339
 340 pub fn fold_attrs<T: Folder>(attrs: Vec<Attribute>, fld: &mut T) -> Vec<Attribute> {
 341     attrs.move_flat_map(|x| fld.fold_attribute(x))
 342 }
 343
 344 pub fn fold_thin_attrs<T: Folder>(attrs: ThinVec<Attribute>, fld: &mut T) -> ThinVec<Attribute> {
 345     fold_attrs(attrs.into(), fld).into()
 346 }
 347
 348 pub fn noop_fold_arm<T: Folder>(Arm {attrs, pats, guard, body}: Arm,
 349     fld: &mut T) -> Arm {
 350     Arm {
 351         attrs: fold_attrs(attrs, fld),
 352         pats: pats.move_map(|x| fld.fold_pat(x)),
 353         guard: guard.map(|x| fld.fold_expr(x)),
 354         body: fld.fold_expr(body),
 355     }
 356 }
 357
 358 pub fn noop_fold_ty_binding<T: Folder>(b: TypeBinding, fld: &mut T) -> TypeBinding {
 359     TypeBinding {
 360         id: fld.new_id(b.id),
 361         ident: fld.fold_ident(b.ident),
 362         ty: fld.fold_ty(b.ty),
 363         span: fld.new_span(b.span),
 364     }
 365 }
 366
 367 pub fn noop_fold_ty<T: Folder>(t: P<Ty>, fld: &mut T) -> P<Ty> {
 368     t.map(|Ty {id, node, span}| Ty {
 369         id: fld.new_id(id),
 370         node: match node {
 371             TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err => node,
 372             TyKind::Slice(ty) => TyKind::Slice(fld.fold_ty(ty)),
 373             TyKind::Ptr(mt) => TyKind::Ptr(fld.fold_mt(mt)),
 374             TyKind::Rptr(region, mt) => {
 375                 TyKind::Rptr(fld.fold_opt_lifetime(region), fld.fold_mt(mt))
 376             }
 377             TyKind::BareFn(f) => {
 378                 TyKind::BareFn(f.map(|BareFnTy {generic_params, unsafety, abi, decl}| BareFnTy {
 379                     generic_params: fld.fold_generic_params(generic_params),
 380                     unsafety,
 381                     abi,
 382                     decl: fld.fold_fn_decl(decl)
 383                 }))
 384             }
 385             TyKind::Never => node,
 386             TyKind::Tup(tys) => TyKind::Tup(tys.move_map(|ty| fld.fold_ty(ty))),
 387             TyKind::Paren(ty) => TyKind::Paren(fld.fold_ty(ty)),
 388             TyKind::Path(qself, path) => {
 389                 let qself = qself.map(|QSelf { ty, position }| {
 390                     QSelf {
 391                         ty: fld.fold_ty(ty),
 392                         position,
 393                     }
 394                 });
 395                 TyKind::Path(qself, fld.fold_path(path))
 396             }
 397             TyKind::Array(ty, e) => {
 398                 TyKind::Array(fld.fold_ty(ty), fld.fold_expr(e))
 399             }
 400             TyKind::Typeof(expr) => {
 401                 TyKind::Typeof(fld.fold_expr(expr))
 402             }
 403             TyKind::TraitObject(bounds, syntax) => {
 404                 TyKind::TraitObject(bounds.move_map(|b| fld.fold_ty_param_bound(b)), syntax)
 405             }
 406             TyKind::ImplTrait(bounds) => {
 407                 TyKind::ImplTrait(bounds.move_map(|b| fld.fold_ty_param_bound(b)))
 408             }
 409             TyKind::Mac(mac) => {
 410                 TyKind::Mac(fld.fold_mac(mac))
 411             }
 412         },
 413         span: fld.new_span(span)
 414     })
 415 }
 416
 417 pub fn noop_fold_foreign_mod<T: Folder>(ForeignMod {abi, items}: ForeignMod,
 418                                         fld: &mut T) -> ForeignMod {
 419     ForeignMod {
 420         abi,
 421         items: items.move_flat_map(|x| fld.fold_foreign_item(x)),
 422     }
 423 }
 424
 425 pub fn noop_fold_global_asm<T: Folder>(ga: P<GlobalAsm>,
 426                                        _: &mut T) -> P<GlobalAsm> {
 427     ga
 428 }
 429
 430 pub fn noop_fold_variant<T: Folder>(v: Variant, fld: &mut T) -> Variant {
 431     Spanned {
 432         node: Variant_ {
 433             ident: fld.fold_ident(v.node.ident),
 434             attrs: fold_attrs(v.node.attrs, fld),
 435             data: fld.fold_variant_data(v.node.data),
 436             disr_expr: v.node.disr_expr.map(|e| fld.fold_expr(e)),
 437         },
 438         span: fld.new_span(v.span),
 439     }
 440 }
 441
 442 pub fn noop_fold_ident<T: Folder>(ident: Ident, fld: &mut T) -> Ident {
 443     Ident::new(ident.name, fld.new_span(ident.span))
 444 }
 445
 446 pub fn noop_fold_usize<T: Folder>(i: usize, _: &mut T) -> usize {
 447     i
 448 }
 449
 450 pub fn noop_fold_path<T: Folder>(Path { segments, span }: Path, fld: &mut T) -> Path {
 451     Path {
 452         segments: segments.move_map(|PathSegment {ident, parameters}| PathSegment {
 453             ident: fld.fold_ident(ident),
 454             parameters: parameters.map(|ps| ps.map(|ps| fld.fold_path_parameters(ps))),
 455         }),
 456         span: fld.new_span(span)
 457     }
 458 }
 459
 460 pub fn noop_fold_path_parameters<T: Folder>(path_parameters: PathParameters, fld: &mut T)
 461                                             -> PathParameters
 462 {
 463     match path_parameters {
 464         PathParameters::AngleBracketed(data) =>
 465             PathParameters::AngleBracketed(fld.fold_angle_bracketed_parameter_data(data)),
 466         PathParameters::Parenthesized(data) =>
 467             PathParameters::Parenthesized(fld.fold_parenthesized_parameter_data(data)),
 468     }
 469 }
 470
 471 pub fn noop_fold_angle_bracketed_parameter_data<T: Folder>(data: AngleBracketedParameterData,
 472                                                            fld: &mut T)
 473                                                            -> AngleBracketedParameterData
 474 {
 475     let AngleBracketedParameterData { lifetimes, types, bindings, span } = data;
 476     AngleBracketedParameterData { lifetimes: fld.fold_lifetimes(lifetimes),
 477                                   types: types.move_map(|ty| fld.fold_ty(ty)),
 478                                   bindings: bindings.move_map(|b| fld.fold_ty_binding(b)),
 479                                   span: fld.new_span(span) }
 480 }
 481
 482 pub fn noop_fold_parenthesized_parameter_data<T: Folder>(data: ParenthesizedParameterData,
 483                                                          fld: &mut T)
 484                                                          -> ParenthesizedParameterData
 485 {
 486     let ParenthesizedParameterData { inputs, output, span } = data;
 487     ParenthesizedParameterData { inputs: inputs.move_map(|ty| fld.fold_ty(ty)),
 488                                  output: output.map(|ty| fld.fold_ty(ty)),
 489                                  span: fld.new_span(span) }
 490 }
 491
 492 pub fn noop_fold_local<T: Folder>(l: P<Local>, fld: &mut T) -> P<Local> {
 493     l.map(|Local {id, pat, ty, init, span, attrs}| Local {
 494         id: fld.new_id(id),
 495         pat: fld.fold_pat(pat),
 496         ty: ty.map(|t| fld.fold_ty(t)),
 497         init: init.map(|e| fld.fold_expr(e)),
 498         span: fld.new_span(span),
 499         attrs: fold_attrs(attrs.into(), fld).into(),
 500     })
 501 }
 502
 503 pub fn noop_fold_attribute<T: Folder>(attr: Attribute, fld: &mut T) -> Option<Attribute> {
 504     Some(Attribute {
 505         id: attr.id,
 506         style: attr.style,
 507         path: fld.fold_path(attr.path),
 508         tokens: fld.fold_tts(attr.tokens),
 509         is_sugared_doc: attr.is_sugared_doc,
 510         span: fld.new_span(attr.span),
 511     })
 512 }
 513
 514 pub fn noop_fold_mac<T: Folder>(Spanned {node, span}: Mac, fld: &mut T) -> Mac {
 515     Spanned {
 516         node: Mac_ {
 517             tts: fld.fold_tts(node.stream()).into(),
 518             path: fld.fold_path(node.path),
 519         },
 520         span: fld.new_span(span)
 521     }
 522 }
 523
 524 pub fn noop_fold_macro_def<T: Folder>(def: MacroDef, fld: &mut T) -> MacroDef {
 525     MacroDef {
 526         tokens: fld.fold_tts(def.tokens.into()).into(),
 527         legacy: def.legacy,
 528     }
 529 }
 530
 531 pub fn noop_fold_meta_list_item<T: Folder>(li: NestedMetaItem, fld: &mut T)
 532     -> NestedMetaItem {
 533     Spanned {
 534         node: match li.node {
 535             NestedMetaItemKind::MetaItem(mi) =>  {
 536                 NestedMetaItemKind::MetaItem(fld.fold_meta_item(mi))
 537             },
 538             NestedMetaItemKind::Literal(lit) => NestedMetaItemKind::Literal(lit)
 539         },
 540         span: fld.new_span(li.span)
 541     }
 542 }
 543
 544 pub fn noop_fold_meta_item<T: Folder>(mi: MetaItem, fld: &mut T) -> MetaItem {
 545     MetaItem {
 546         name: mi.name,
 547         node: match mi.node {
 548             MetaItemKind::Word => MetaItemKind::Word,
 549             MetaItemKind::List(mis) => {
 550                 MetaItemKind::List(mis.move_map(|e| fld.fold_meta_list_item(e)))
 551             },
 552             MetaItemKind::NameValue(s) => MetaItemKind::NameValue(s),
 553         },
 554         span: fld.new_span(mi.span)
 555     }
 556 }
 557
 558 pub fn noop_fold_arg<T: Folder>(Arg {id, pat, ty}: Arg, fld: &mut T) -> Arg {
 559     Arg {
 560         id: fld.new_id(id),
 561         pat: fld.fold_pat(pat),
 562         ty: fld.fold_ty(ty)
 563     }
 564 }
 565
 566 pub fn noop_fold_tt<T: Folder>(tt: TokenTree, fld: &mut T) -> TokenTree {
 567     match tt {
 568         TokenTree::Token(span, tok) =>
 569             TokenTree::Token(fld.new_span(span), fld.fold_token(tok)),
 570         TokenTree::Delimited(span, delimed) => TokenTree::Delimited(fld.new_span(span), Delimited {
 571             tts: fld.fold_tts(delimed.stream()).into(),
 572             delim: delimed.delim,
 573         }),
 574     }
 575 }
 576
 577 pub fn noop_fold_tts<T: Folder>(tts: TokenStream, fld: &mut T) -> TokenStream {
 578     tts.map(|tt| fld.fold_tt(tt))
 579 }
 580
 581 // apply ident folder if it's an ident, apply other folds to interpolated nodes
 582 pub fn noop_fold_token<T: Folder>(t: token::Token, fld: &mut T) -> token::Token {
 583     match t {
 584         token::Ident(id, is_raw) => token::Ident(fld.fold_ident(id), is_raw),
 585         token::Lifetime(id) => token::Lifetime(fld.fold_ident(id)),
 586         token::Interpolated(nt) => {
 587             let nt = match Lrc::try_unwrap(nt) {
 588                 Ok(nt) => nt,
 589                 Err(nt) => (*nt).clone(),
 590             };
 591             Token::interpolated(fld.fold_interpolated(nt.0))
 592         }
 593         _ => t
 594     }
 595 }
 596
 597 /// apply folder to elements of interpolated nodes
 598 //
 599 // NB: this can occur only when applying a fold to partially expanded code, where
 600 // parsed pieces have gotten implanted ito *other* macro invocations. This is relevant
 601 // for macro hygiene, but possibly not elsewhere.
 602 //
 603 // One problem here occurs because the types for fold_item, fold_stmt, etc. allow the
 604 // folder to return *multiple* items; this is a problem for the nodes here, because
 605 // they insist on having exactly one piece. One solution would be to mangle the fold
 606 // trait to include one-to-many and one-to-one versions of these entry points, but that
 607 // would probably confuse a lot of people and help very few. Instead, I'm just going
 608 // to put in dynamic checks. I think the performance impact of this will be pretty much
 609 // nonexistent. The danger is that someone will apply a fold to a partially expanded
 610 // node, and will be confused by the fact that their "fold_item" or "fold_stmt" isn't
 611 // getting called on NtItem or NtStmt nodes. Hopefully they'll wind up reading this
 612 // comment, and doing something appropriate.
 613 //
 614 // BTW, design choice: I considered just changing the type of, e.g., NtItem to contain
 615 // multiple items, but decided against it when I looked at parse_item_or_view_item and
 616 // tried to figure out what I would do with multiple items there....
 617 pub fn noop_fold_interpolated<T: Folder>(nt: token::Nonterminal, fld: &mut T)
 618                                          -> token::Nonterminal {
 619     match nt {
 620         token::NtItem(item) =>
 621             token::NtItem(fld.fold_item(item)
 622                           // this is probably okay, because the only folds likely
 623                           // to peek inside interpolated nodes will be renamings/markings,
 624                           // which map single items to single items
 625                           .expect_one("expected fold to produce exactly one item")),
 626         token::NtBlock(block) => token::NtBlock(fld.fold_block(block)),
 627         token::NtStmt(stmt) =>
 628             token::NtStmt(fld.fold_stmt(stmt)
 629                           // this is probably okay, because the only folds likely
 630                           // to peek inside interpolated nodes will be renamings/markings,
 631                           // which map single items to single items
 632                           .expect_one("expected fold to produce exactly one statement")),
 633         token::NtPat(pat) => token::NtPat(fld.fold_pat(pat)),
 634         token::NtExpr(expr) => token::NtExpr(fld.fold_expr(expr)),
 635         token::NtTy(ty) => token::NtTy(fld.fold_ty(ty)),
 636         token::NtIdent(ident, is_raw) => token::NtIdent(fld.fold_ident(ident), is_raw),
 637         token::NtLifetime(ident) => token::NtLifetime(fld.fold_ident(ident)),
 638         token::NtMeta(meta) => token::NtMeta(fld.fold_meta_item(meta)),
 639         token::NtPath(path) => token::NtPath(fld.fold_path(path)),
 640         token::NtTT(tt) => token::NtTT(fld.fold_tt(tt)),
 641         token::NtArm(arm) => token::NtArm(fld.fold_arm(arm)),
 642         token::NtImplItem(item) =>
 643             token::NtImplItem(fld.fold_impl_item(item)
 644                               .expect_one("expected fold to produce exactly one item")),
 645         token::NtTraitItem(item) =>
 646             token::NtTraitItem(fld.fold_trait_item(item)
 647                                .expect_one("expected fold to produce exactly one item")),
 648         token::NtGenerics(generics) => token::NtGenerics(fld.fold_generics(generics)),
 649         token::NtWhereClause(where_clause) =>
 650             token::NtWhereClause(fld.fold_where_clause(where_clause)),
 651         token::NtArg(arg) => token::NtArg(fld.fold_arg(arg)),
 652         token::NtVis(vis) => token::NtVis(fld.fold_vis(vis)),
 653         token::NtForeignItem(ni) =>
 654             token::NtForeignItem(fld.fold_foreign_item(ni)
 655                                  // see reasoning above
 656                                  .expect_one("expected fold to produce exactly one item")),
 657     }
 658 }
 659
 660 pub fn noop_fold_fn_decl<T: Folder>(decl: P<FnDecl>, fld: &mut T) -> P<FnDecl> {
 661     decl.map(|FnDecl {inputs, output, variadic}| FnDecl {
 662         inputs: inputs.move_map(|x| fld.fold_arg(x)),
 663         output: match output {
 664             FunctionRetTy::Ty(ty) => FunctionRetTy::Ty(fld.fold_ty(ty)),
 665             FunctionRetTy::Default(span) => FunctionRetTy::Default(fld.new_span(span)),
 666         },
 667         variadic,
 668     })
 669 }
 670
 671 pub fn noop_fold_ty_param_bound<T>(tpb: TyParamBound, fld: &mut T)
 672                                    -> TyParamBound
 673                                    where T: Folder {
 674     match tpb {
 675         TraitTyParamBound(ty, modifier) => TraitTyParamBound(fld.fold_poly_trait_ref(ty), modifier),
 676         RegionTyParamBound(lifetime) => RegionTyParamBound(fld.fold_lifetime(lifetime)),
 677     }
 678 }
 679
 680 pub fn noop_fold_ty_param<T: Folder>(tp: TyParam, fld: &mut T) -> TyParam {
 681     let TyParam {attrs, id, ident, bounds, default} = tp;
 682     let attrs: Vec<_> = attrs.into();
 683     TyParam {
 684         attrs: attrs.into_iter()
 685             .flat_map(|x| fld.fold_attribute(x).into_iter())
 686             .collect::<Vec<_>>()
 687             .into(),
 688         id: fld.new_id(id),
 689         ident: fld.fold_ident(ident),
 690         bounds: fld.fold_bounds(bounds),
 691         default: default.map(|x| fld.fold_ty(x)),
 692     }
 693 }
 694
 695 pub fn noop_fold_generic_param<T: Folder>(param: GenericParam, fld: &mut T) -> GenericParam {
 696     match param {
 697         GenericParam::Lifetime(l) => GenericParam::Lifetime(fld.fold_lifetime_def(l)),
 698         GenericParam::Type(t) => GenericParam::Type(fld.fold_ty_param(t)),
 699     }
 700 }
 701
 702 pub fn noop_fold_generic_params<T: Folder>(
 703     params: Vec<GenericParam>,
 704     fld: &mut T
 705 ) -> Vec<GenericParam> {
 706     params.move_map(|p| fld.fold_generic_param(p))
 707 }
 708
 709 pub fn noop_fold_label<T: Folder>(label: Label, fld: &mut T) -> Label {
 710     Label {
 711         ident: fld.fold_ident(label.ident),
 712     }
 713 }
 714
 715 pub fn noop_fold_lifetime<T: Folder>(l: Lifetime, fld: &mut T) -> Lifetime {
 716     Lifetime {
 717         id: fld.new_id(l.id),
 718         ident: fld.fold_ident(l.ident),
 719     }
 720 }
 721
 722 pub fn noop_fold_lifetime_def<T: Folder>(l: LifetimeDef, fld: &mut T)
 723                                          -> LifetimeDef {
 724     let attrs: Vec<_> = l.attrs.into();
 725     LifetimeDef {
 726         attrs: attrs.into_iter()
 727             .flat_map(|x| fld.fold_attribute(x).into_iter())
 728             .collect::<Vec<_>>()
 729             .into(),
 730         lifetime: fld.fold_lifetime(l.lifetime),
 731         bounds: fld.fold_lifetimes(l.bounds),
 732     }
 733 }
 734
 735 pub fn noop_fold_lifetimes<T: Folder>(lts: Vec<Lifetime>, fld: &mut T) -> Vec<Lifetime> {
 736     lts.move_map(|l| fld.fold_lifetime(l))
 737 }
 738
 739 pub fn noop_fold_lifetime_defs<T: Folder>(lts: Vec<LifetimeDef>, fld: &mut T)
 740                                           -> Vec<LifetimeDef> {
 741     lts.move_map(|l| fld.fold_lifetime_def(l))
 742 }
 743
 744 pub fn noop_fold_opt_lifetime<T: Folder>(o_lt: Option<Lifetime>, fld: &mut T)
 745                                          -> Option<Lifetime> {
 746     o_lt.map(|lt| fld.fold_lifetime(lt))
 747 }
 748
 749 pub fn noop_fold_generics<T: Folder>(Generics { params, where_clause, span }: Generics,
 750                                      fld: &mut T) -> Generics {
 751     Generics {
 752         params: fld.fold_generic_params(params),
 753         where_clause: fld.fold_where_clause(where_clause),
 754         span: fld.new_span(span),
 755     }
 756 }
 757
 758 pub fn noop_fold_where_clause<T: Folder>(
 759                               WhereClause {id, predicates, span}: WhereClause,
 760                               fld: &mut T)
 761                               -> WhereClause {
 762     WhereClause {
 763         id: fld.new_id(id),
 764         predicates: predicates.move_map(|predicate| {
 765             fld.fold_where_predicate(predicate)
 766         }),
 767         span,
 768     }
 769 }
 770
 771 pub fn noop_fold_where_predicate<T: Folder>(
 772                                  pred: WherePredicate,
 773                                  fld: &mut T)
 774                                  -> WherePredicate {
 775     match pred {
 776         ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate{bound_generic_params,
 777                                                                      bounded_ty,
 778                                                                      bounds,
 779                                                                      span}) => {
 780             ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
 781                 bound_generic_params: fld.fold_generic_params(bound_generic_params),
 782                 bounded_ty: fld.fold_ty(bounded_ty),
 783                 bounds: bounds.move_map(|x| fld.fold_ty_param_bound(x)),
 784                 span: fld.new_span(span)
 785             })
 786         }
 787         ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate{lifetime,
 788                                                                        bounds,
 789                                                                        span}) => {
 790             ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
 791                 span: fld.new_span(span),
 792                 lifetime: fld.fold_lifetime(lifetime),
 793                 bounds: bounds.move_map(|bound| fld.fold_lifetime(bound))
 794             })
 795         }
 796         ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{id,
 797                                                                lhs_ty,
 798                                                                rhs_ty,
 799                                                                span}) => {
 800             ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{
 801                 id: fld.new_id(id),
 802                 lhs_ty: fld.fold_ty(lhs_ty),
 803                 rhs_ty: fld.fold_ty(rhs_ty),
 804                 span: fld.new_span(span)
 805             })
 806         }
 807     }
 808 }
 809
 810 pub fn noop_fold_variant_data<T: Folder>(vdata: VariantData, fld: &mut T) -> VariantData {
 811     match vdata {
 812         ast::VariantData::Struct(fields, id) => {
 813             ast::VariantData::Struct(fields.move_map(|f| fld.fold_struct_field(f)),
 814                                      fld.new_id(id))
 815         }
 816         ast::VariantData::Tuple(fields, id) => {
 817             ast::VariantData::Tuple(fields.move_map(|f| fld.fold_struct_field(f)),
 818                                     fld.new_id(id))
 819         }
 820         ast::VariantData::Unit(id) => ast::VariantData::Unit(fld.new_id(id))
 821     }
 822 }
 823
 824 pub fn noop_fold_trait_ref<T: Folder>(p: TraitRef, fld: &mut T) -> TraitRef {
 825     let id = fld.new_id(p.ref_id);
 826     let TraitRef {
 827         path,
 828         ref_id: _,
 829     } = p;
 830     ast::TraitRef {
 831         path: fld.fold_path(path),
 832         ref_id: id,
 833     }
 834 }
 835
 836 pub fn noop_fold_poly_trait_ref<T: Folder>(p: PolyTraitRef, fld: &mut T) -> PolyTraitRef {
 837     ast::PolyTraitRef {
 838         bound_generic_params: fld.fold_generic_params(p.bound_generic_params),
 839         trait_ref: fld.fold_trait_ref(p.trait_ref),
 840         span: fld.new_span(p.span),
 841     }
 842 }
 843
 844 pub fn noop_fold_struct_field<T: Folder>(f: StructField, fld: &mut T) -> StructField {
 845     StructField {
 846         span: fld.new_span(f.span),
 847         id: fld.new_id(f.id),
 848         ident: f.ident.map(|ident| fld.fold_ident(ident)),
 849         vis: fld.fold_vis(f.vis),
 850         ty: fld.fold_ty(f.ty),
 851         attrs: fold_attrs(f.attrs, fld),
 852     }
 853 }
 854
 855 pub fn noop_fold_field<T: Folder>(f: Field, folder: &mut T) -> Field {
 856     Field {
 857         ident: folder.fold_ident(f.ident),
 858         expr: folder.fold_expr(f.expr),
 859         span: folder.new_span(f.span),
 860         is_shorthand: f.is_shorthand,
 861         attrs: fold_thin_attrs(f.attrs, folder),
 862     }
 863 }
 864
 865 pub fn noop_fold_mt<T: Folder>(MutTy {ty, mutbl}: MutTy, folder: &mut T) -> MutTy {
 866     MutTy {
 867         ty: folder.fold_ty(ty),
 868         mutbl,
 869     }
 870 }
 871
 872 pub fn noop_fold_opt_bounds<T: Folder>(b: Option<TyParamBounds>, folder: &mut T)
 873                                        -> Option<TyParamBounds> {
 874     b.map(|bounds| folder.fold_bounds(bounds))
 875 }
 876
 877 fn noop_fold_bounds<T: Folder>(bounds: TyParamBounds, folder: &mut T)
 878                           -> TyParamBounds {
 879     bounds.move_map(|bound| folder.fold_ty_param_bound(bound))
 880 }
 881
 882 pub fn noop_fold_block<T: Folder>(b: P<Block>, folder: &mut T) -> P<Block> {
 883     b.map(|Block {id, stmts, rules, span, recovered}| Block {
 884         id: folder.new_id(id),
 885         stmts: stmts.move_flat_map(|s| folder.fold_stmt(s).into_iter()),
 886         rules,
 887         span: folder.new_span(span),
 888         recovered,
 889     })
 890 }
 891
 892 pub fn noop_fold_item_kind<T: Folder>(i: ItemKind, folder: &mut T) -> ItemKind {
 893     match i {
 894         ItemKind::ExternCrate(orig_name) => ItemKind::ExternCrate(orig_name),
 895         ItemKind::Use(use_tree) => {
 896             ItemKind::Use(use_tree.map(|tree| folder.fold_use_tree(tree)))
 897         }
 898         ItemKind::Static(t, m, e) => {
 899             ItemKind::Static(folder.fold_ty(t), m, folder.fold_expr(e))
 900         }
 901         ItemKind::Const(t, e) => {
 902             ItemKind::Const(folder.fold_ty(t), folder.fold_expr(e))
 903         }
 904         ItemKind::Fn(decl, unsafety, constness, abi, generics, body) => {
 905             let generics = folder.fold_generics(generics);
 906             let decl = folder.fold_fn_decl(decl);
 907             let body = folder.fold_block(body);
 908             ItemKind::Fn(decl, unsafety, constness, abi, generics, body)
 909         }
 910         ItemKind::Mod(m) => ItemKind::Mod(folder.fold_mod(m)),
 911         ItemKind::ForeignMod(nm) => ItemKind::ForeignMod(folder.fold_foreign_mod(nm)),
 912         ItemKind::GlobalAsm(ga) => ItemKind::GlobalAsm(folder.fold_global_asm(ga)),
 913         ItemKind::Ty(t, generics) => {
 914             ItemKind::Ty(folder.fold_ty(t), folder.fold_generics(generics))
 915         }
 916         ItemKind::Enum(enum_definition, generics) => {
 917             let generics = folder.fold_generics(generics);
 918             let variants = enum_definition.variants.move_map(|x| folder.fold_variant(x));
 919             ItemKind::Enum(ast::EnumDef { variants: variants }, generics)
 920         }
 921         ItemKind::Struct(struct_def, generics) => {
 922             let generics = folder.fold_generics(generics);
 923             ItemKind::Struct(folder.fold_variant_data(struct_def), generics)
 924         }
 925         ItemKind::Union(struct_def, generics) => {
 926             let generics = folder.fold_generics(generics);
 927             ItemKind::Union(folder.fold_variant_data(struct_def), generics)
 928         }
 929         ItemKind::Impl(unsafety,
 930                        polarity,
 931                        defaultness,
 932                        generics,
 933                        ifce,
 934                        ty,
 935                        impl_items) => ItemKind::Impl(
 936             unsafety,
 937             polarity,
 938             defaultness,
 939             folder.fold_generics(generics),
 940             ifce.map(|trait_ref| folder.fold_trait_ref(trait_ref.clone())),
 941             folder.fold_ty(ty),
 942             impl_items.move_flat_map(|item| folder.fold_impl_item(item)),
 943         ),
 944         ItemKind::Trait(is_auto, unsafety, generics, bounds, items) => ItemKind::Trait(
 945             is_auto,
 946             unsafety,
 947             folder.fold_generics(generics),
 948             folder.fold_bounds(bounds),
 949             items.move_flat_map(|item| folder.fold_trait_item(item)),
 950         ),
 951         ItemKind::TraitAlias(generics, bounds) => ItemKind::TraitAlias(
 952             folder.fold_generics(generics),
 953             folder.fold_bounds(bounds)),
 954         ItemKind::Mac(m) => ItemKind::Mac(folder.fold_mac(m)),
 955         ItemKind::MacroDef(def) => ItemKind::MacroDef(folder.fold_macro_def(def)),
 956     }
 957 }
 958
 959 pub fn noop_fold_trait_item<T: Folder>(i: TraitItem, folder: &mut T)
 960                                        -> SmallVector<TraitItem> {
 961     SmallVector::one(TraitItem {
 962         id: folder.new_id(i.id),
 963         ident: folder.fold_ident(i.ident),
 964         attrs: fold_attrs(i.attrs, folder),
 965         generics: folder.fold_generics(i.generics),
 966         node: match i.node {
 967             TraitItemKind::Const(ty, default) => {
 968                 TraitItemKind::Const(folder.fold_ty(ty),
 969                                default.map(|x| folder.fold_expr(x)))
 970             }
 971             TraitItemKind::Method(sig, body) => {
 972                 TraitItemKind::Method(noop_fold_method_sig(sig, folder),
 973                                 body.map(|x| folder.fold_block(x)))
 974             }
 975             TraitItemKind::Type(bounds, default) => {
 976                 TraitItemKind::Type(folder.fold_bounds(bounds),
 977                               default.map(|x| folder.fold_ty(x)))
 978             }
 979             ast::TraitItemKind::Macro(mac) => {
 980                 TraitItemKind::Macro(folder.fold_mac(mac))
 981             }
 982         },
 983         span: folder.new_span(i.span),
 984         tokens: i.tokens,
 985     })
 986 }
 987
 988 pub fn noop_fold_impl_item<T: Folder>(i: ImplItem, folder: &mut T)
 989                                       -> SmallVector<ImplItem> {
 990     SmallVector::one(ImplItem {
 991         id: folder.new_id(i.id),
 992         vis: folder.fold_vis(i.vis),
 993         ident: folder.fold_ident(i.ident),
 994         attrs: fold_attrs(i.attrs, folder),
 995         generics: folder.fold_generics(i.generics),
 996         defaultness: i.defaultness,
 997         node: match i.node  {
 998             ast::ImplItemKind::Const(ty, expr) => {
 999                 ast::ImplItemKind::Const(folder.fold_ty(ty), folder.fold_expr(expr))
1000             }
1001             ast::ImplItemKind::Method(sig, body) => {
1002                 ast::ImplItemKind::Method(noop_fold_method_sig(sig, folder),
1003                                folder.fold_block(body))
1004             }
1005             ast::ImplItemKind::Type(ty) => ast::ImplItemKind::Type(folder.fold_ty(ty)),
1006             ast::ImplItemKind::Macro(mac) => ast::ImplItemKind::Macro(folder.fold_mac(mac))
1007         },
1008         span: folder.new_span(i.span),
1009         tokens: i.tokens,
1010     })
1011 }
1012
1013 pub fn noop_fold_mod<T: Folder>(Mod {inner, items}: Mod, folder: &mut T) -> Mod {
1014     Mod {
1015         inner: folder.new_span(inner),
1016         items: items.move_flat_map(|x| folder.fold_item(x)),
1017     }
1018 }
1019
1020 pub fn noop_fold_crate<T: Folder>(Crate {module, attrs, span}: Crate,
1021                                   folder: &mut T) -> Crate {
1022     let mut items = folder.fold_item(P(ast::Item {
1023         ident: keywords::Invalid.ident(),
1024         attrs,
1025         id: ast::DUMMY_NODE_ID,
1026         vis: respan(span.shrink_to_lo(), ast::VisibilityKind::Public),
1027         span,
1028         node: ast::ItemKind::Mod(module),
1029         tokens: None,
1030     })).into_iter();
1031
1032     let (module, attrs, span) = match items.next() {
1033         Some(item) => {
1034             assert!(items.next().is_none(),
1035                     "a crate cannot expand to more than one item");
1036             item.and_then(|ast::Item { attrs, span, node, .. }| {
1037                 match node {
1038                     ast::ItemKind::Mod(m) => (m, attrs, span),
1039                     _ => panic!("fold converted a module to not a module"),
1040                 }
1041             })
1042         }
1043         None => (ast::Mod {
1044             inner: span,
1045             items: vec![],
1046         }, vec![], span)
1047     };
1048
1049     Crate {
1050         module,
1051         attrs,
1052         span,
1053     }
1054 }
1055
1056 // fold one item into possibly many items
1057 pub fn noop_fold_item<T: Folder>(i: P<Item>, folder: &mut T) -> SmallVector<P<Item>> {
1058     SmallVector::one(i.map(|i| folder.fold_item_simple(i)))
1059 }
1060
1061 // fold one item into exactly one item
1062 pub fn noop_fold_item_simple<T: Folder>(Item {id, ident, attrs, node, vis, span, tokens}: Item,
1063                                         folder: &mut T) -> Item {
1064     Item {
1065         id: folder.new_id(id),
1066         vis: folder.fold_vis(vis),
1067         ident: folder.fold_ident(ident),
1068         attrs: fold_attrs(attrs, folder),
1069         node: folder.fold_item_kind(node),
1070         span: folder.new_span(span),
1071
1072         // FIXME: if this is replaced with a call to `folder.fold_tts` it causes
1073         //        an ICE during resolve... odd!
1074         tokens,
1075     }
1076 }
1077
1078 pub fn noop_fold_foreign_item<T: Folder>(ni: ForeignItem, folder: &mut T)
1079 -> SmallVector<ForeignItem> {
1080     SmallVector::one(folder.fold_foreign_item_simple(ni))
1081 }
1082
1083 pub fn noop_fold_foreign_item_simple<T: Folder>(ni: ForeignItem, folder: &mut T) -> ForeignItem {
1084     ForeignItem {
1085         id: folder.new_id(ni.id),
1086         vis: folder.fold_vis(ni.vis),
1087         ident: folder.fold_ident(ni.ident),
1088         attrs: fold_attrs(ni.attrs, folder),
1089         node: match ni.node {
1090             ForeignItemKind::Fn(fdec, generics) => {
1091                 ForeignItemKind::Fn(folder.fold_fn_decl(fdec), folder.fold_generics(generics))
1092             }
1093             ForeignItemKind::Static(t, m) => {
1094                 ForeignItemKind::Static(folder.fold_ty(t), m)
1095             }
1096             ForeignItemKind::Ty => ForeignItemKind::Ty,
1097             ForeignItemKind::Macro(mac) => ForeignItemKind::Macro(folder.fold_mac(mac)),
1098         },
1099         span: folder.new_span(ni.span)
1100     }
1101 }
1102
1103 pub fn noop_fold_method_sig<T: Folder>(sig: MethodSig, folder: &mut T) -> MethodSig {
1104     MethodSig {
1105         abi: sig.abi,
1106         unsafety: sig.unsafety,
1107         constness: sig.constness,
1108         decl: folder.fold_fn_decl(sig.decl)
1109     }
1110 }
1111
1112 pub fn noop_fold_pat<T: Folder>(p: P<Pat>, folder: &mut T) -> P<Pat> {
1113     p.map(|Pat {id, node, span}| Pat {
1114         id: folder.new_id(id),
1115         node: match node {
1116             PatKind::Wild => PatKind::Wild,
1117             PatKind::Ident(binding_mode, ident, sub) => {
1118                 PatKind::Ident(binding_mode,
1119                                folder.fold_ident(ident),
1120                                sub.map(|x| folder.fold_pat(x)))
1121             }
1122             PatKind::Lit(e) => PatKind::Lit(folder.fold_expr(e)),
1123             PatKind::TupleStruct(pth, pats, ddpos) => {
1124                 PatKind::TupleStruct(folder.fold_path(pth),
1125                         pats.move_map(|x| folder.fold_pat(x)), ddpos)
1126             }
1127             PatKind::Path(opt_qself, pth) => {
1128                 let opt_qself = opt_qself.map(|qself| {
1129                     QSelf { ty: folder.fold_ty(qself.ty), position: qself.position }
1130                 });
1131                 PatKind::Path(opt_qself, folder.fold_path(pth))
1132             }
1133             PatKind::Struct(pth, fields, etc) => {
1134                 let pth = folder.fold_path(pth);
1135                 let fs = fields.move_map(|f| {
1136                     Spanned { span: folder.new_span(f.span),
1137                               node: ast::FieldPat {
1138                                   ident: folder.fold_ident(f.node.ident),
1139                                   pat: folder.fold_pat(f.node.pat),
1140                                   is_shorthand: f.node.is_shorthand,
1141                                   attrs: fold_attrs(f.node.attrs.into(), folder).into()
1142                               }}
1143                 });
1144                 PatKind::Struct(pth, fs, etc)
1145             }
1146             PatKind::Tuple(elts, ddpos) => {
1147                 PatKind::Tuple(elts.move_map(|x| folder.fold_pat(x)), ddpos)
1148             }
1149             PatKind::Box(inner) => PatKind::Box(folder.fold_pat(inner)),
1150             PatKind::Ref(inner, mutbl) => PatKind::Ref(folder.fold_pat(inner), mutbl),
1151             PatKind::Range(e1, e2, end) => {
1152                 PatKind::Range(folder.fold_expr(e1),
1153                                folder.fold_expr(e2),
1154                                folder.fold_range_end(end))
1155             },
1156             PatKind::Slice(before, slice, after) => {
1157                 PatKind::Slice(before.move_map(|x| folder.fold_pat(x)),
1158                        slice.map(|x| folder.fold_pat(x)),
1159                        after.move_map(|x| folder.fold_pat(x)))
1160             }
1161             PatKind::Paren(inner) => PatKind::Paren(folder.fold_pat(inner)),
1162             PatKind::Mac(mac) => PatKind::Mac(folder.fold_mac(mac))
1163         },
1164         span: folder.new_span(span)
1165     })
1166 }
1167
1168 pub fn noop_fold_range_end<T: Folder>(end: RangeEnd, _folder: &mut T) -> RangeEnd {
1169     end
1170 }
1171
1172 pub fn noop_fold_expr<T: Folder>(Expr {id, node, span, attrs}: Expr, folder: &mut T) -> Expr {
1173     Expr {
1174         node: match node {
1175             ExprKind::Box(e) => {
1176                 ExprKind::Box(folder.fold_expr(e))
1177             }
1178             ExprKind::Array(exprs) => {
1179                 ExprKind::Array(folder.fold_exprs(exprs))
1180             }
1181             ExprKind::Repeat(expr, count) => {
1182                 ExprKind::Repeat(folder.fold_expr(expr), folder.fold_expr(count))
1183             }
1184             ExprKind::Tup(exprs) => ExprKind::Tup(folder.fold_exprs(exprs)),
1185             ExprKind::Call(f, args) => {
1186                 ExprKind::Call(folder.fold_expr(f),
1187                          folder.fold_exprs(args))
1188             }
1189             ExprKind::MethodCall(seg, args) => {
1190                 ExprKind::MethodCall(
1191                     PathSegment {
1192                         ident: folder.fold_ident(seg.ident),
1193                         parameters: seg.parameters.map(|ps| {
1194                             ps.map(|ps| folder.fold_path_parameters(ps))
1195                         }),
1196                     },
1197                     folder.fold_exprs(args))
1198             }
1199             ExprKind::Binary(binop, lhs, rhs) => {
1200                 ExprKind::Binary(binop,
1201                         folder.fold_expr(lhs),
1202                         folder.fold_expr(rhs))
1203             }
1204             ExprKind::Unary(binop, ohs) => {
1205                 ExprKind::Unary(binop, folder.fold_expr(ohs))
1206             }
1207             ExprKind::Lit(l) => ExprKind::Lit(l),
1208             ExprKind::Cast(expr, ty) => {
1209                 ExprKind::Cast(folder.fold_expr(expr), folder.fold_ty(ty))
1210             }
1211             ExprKind::Type(expr, ty) => {
1212                 ExprKind::Type(folder.fold_expr(expr), folder.fold_ty(ty))
1213             }
1214             ExprKind::AddrOf(m, ohs) => ExprKind::AddrOf(m, folder.fold_expr(ohs)),
1215             ExprKind::If(cond, tr, fl) => {
1216                 ExprKind::If(folder.fold_expr(cond),
1217                        folder.fold_block(tr),
1218                        fl.map(|x| folder.fold_expr(x)))
1219             }
1220             ExprKind::IfLet(pats, expr, tr, fl) => {
1221                 ExprKind::IfLet(pats.move_map(|pat| folder.fold_pat(pat)),
1222                           folder.fold_expr(expr),
1223                           folder.fold_block(tr),
1224                           fl.map(|x| folder.fold_expr(x)))
1225             }
1226             ExprKind::While(cond, body, opt_label) => {
1227                 ExprKind::While(folder.fold_expr(cond),
1228                           folder.fold_block(body),
1229                           opt_label.map(|label| folder.fold_label(label)))
1230             }
1231             ExprKind::WhileLet(pats, expr, body, opt_label) => {
1232                 ExprKind::WhileLet(pats.move_map(|pat| folder.fold_pat(pat)),
1233                              folder.fold_expr(expr),
1234                              folder.fold_block(body),
1235                              opt_label.map(|label| folder.fold_label(label)))
1236             }
1237             ExprKind::ForLoop(pat, iter, body, opt_label) => {
1238                 ExprKind::ForLoop(folder.fold_pat(pat),
1239                             folder.fold_expr(iter),
1240                             folder.fold_block(body),
1241                             opt_label.map(|label| folder.fold_label(label)))
1242             }
1243             ExprKind::Loop(body, opt_label) => {
1244                 ExprKind::Loop(folder.fold_block(body),
1245                                opt_label.map(|label| folder.fold_label(label)))
1246             }
1247             ExprKind::Match(expr, arms) => {
1248                 ExprKind::Match(folder.fold_expr(expr),
1249                           arms.move_map(|x| folder.fold_arm(x)))
1250             }
1251             ExprKind::Closure(capture_clause, movability, decl, body, span) => {
1252                 ExprKind::Closure(capture_clause,
1253                                   movability,
1254                                   folder.fold_fn_decl(decl),
1255                                   folder.fold_expr(body),
1256                                   folder.new_span(span))
1257             }
1258             ExprKind::Block(blk) => ExprKind::Block(folder.fold_block(blk)),
1259             ExprKind::Assign(el, er) => {
1260                 ExprKind::Assign(folder.fold_expr(el), folder.fold_expr(er))
1261             }
1262             ExprKind::AssignOp(op, el, er) => {
1263                 ExprKind::AssignOp(op,
1264                             folder.fold_expr(el),
1265                             folder.fold_expr(er))
1266             }
1267             ExprKind::Field(el, ident) => {
1268                 ExprKind::Field(folder.fold_expr(el), folder.fold_ident(ident))
1269             }
1270             ExprKind::TupField(el, index) => {
1271                 ExprKind::TupField(folder.fold_expr(el),
1272                              respan(folder.new_span(index.span),
1273                                     folder.fold_usize(index.node)))
1274             }
1275             ExprKind::Index(el, er) => {
1276                 ExprKind::Index(folder.fold_expr(el), folder.fold_expr(er))
1277             }
1278             ExprKind::Range(e1, e2, lim) => {
1279                 ExprKind::Range(e1.map(|x| folder.fold_expr(x)),
1280                                 e2.map(|x| folder.fold_expr(x)),
1281                                 lim)
1282             }
1283             ExprKind::Path(qself, path) => {
1284                 let qself = qself.map(|QSelf { ty, position }| {
1285                     QSelf {
1286                         ty: folder.fold_ty(ty),
1287                         position,
1288                     }
1289                 });
1290                 ExprKind::Path(qself, folder.fold_path(path))
1291             }
1292             ExprKind::Break(opt_label, opt_expr) => {
1293                 ExprKind::Break(opt_label.map(|label| folder.fold_label(label)),
1294                                 opt_expr.map(|e| folder.fold_expr(e)))
1295             }
1296             ExprKind::Continue(opt_label) => {
1297                 ExprKind::Continue(opt_label.map(|label| folder.fold_label(label)))
1298             }
1299             ExprKind::Ret(e) => ExprKind::Ret(e.map(|x| folder.fold_expr(x))),
1300             ExprKind::InlineAsm(asm) => ExprKind::InlineAsm(asm.map(|asm| {
1301                 InlineAsm {
1302                     inputs: asm.inputs.move_map(|(c, input)| {
1303                         (c, folder.fold_expr(input))
1304                     }),
1305                     outputs: asm.outputs.move_map(|out| {
1306                         InlineAsmOutput {
1307                             constraint: out.constraint,
1308                             expr: folder.fold_expr(out.expr),
1309                             is_rw: out.is_rw,
1310                             is_indirect: out.is_indirect,
1311                         }
1312                     }),
1313                     ..asm
1314                 }
1315             })),
1316             ExprKind::Mac(mac) => ExprKind::Mac(folder.fold_mac(mac)),
1317             ExprKind::Struct(path, fields, maybe_expr) => {
1318                 ExprKind::Struct(folder.fold_path(path),
1319                         fields.move_map(|x| folder.fold_field(x)),
1320                         maybe_expr.map(|x| folder.fold_expr(x)))
1321             },
1322             ExprKind::Paren(ex) => {
1323                 let sub_expr = folder.fold_expr(ex);
1324                 return Expr {
1325                     // Nodes that are equal modulo `Paren` sugar no-ops should have the same ids.
1326                     id: sub_expr.id,
1327                     node: ExprKind::Paren(sub_expr),
1328                     span: folder.new_span(span),
1329                     attrs: fold_attrs(attrs.into(), folder).into(),
1330                 };
1331             }
1332             ExprKind::Yield(ex) => ExprKind::Yield(ex.map(|x| folder.fold_expr(x))),
1333             ExprKind::Try(ex) => ExprKind::Try(folder.fold_expr(ex)),
1334             ExprKind::Catch(body) => ExprKind::Catch(folder.fold_block(body)),
1335         },
1336         id: folder.new_id(id),
1337         span: folder.new_span(span),
1338         attrs: fold_attrs(attrs.into(), folder).into(),
1339     }
1340 }
1341
1342 pub fn noop_fold_opt_expr<T: Folder>(e: P<Expr>, folder: &mut T) -> Option<P<Expr>> {
1343     Some(folder.fold_expr(e))
1344 }
1345
1346 pub fn noop_fold_exprs<T: Folder>(es: Vec<P<Expr>>, folder: &mut T) -> Vec<P<Expr>> {
1347     es.move_flat_map(|e| folder.fold_opt_expr(e))
1348 }
1349
1350 pub fn noop_fold_stmt<T: Folder>(Stmt {node, span, id}: Stmt, folder: &mut T) -> SmallVector<Stmt> {
1351     let id = folder.new_id(id);
1352     let span = folder.new_span(span);
1353     noop_fold_stmt_kind(node, folder).into_iter().map(|node| {
1354         Stmt { id: id, node: node, span: span }
1355     }).collect()
1356 }
1357
1358 pub fn noop_fold_stmt_kind<T: Folder>(node: StmtKind, folder: &mut T) -> SmallVector<StmtKind> {
1359     match node {
1360         StmtKind::Local(local) => SmallVector::one(StmtKind::Local(folder.fold_local(local))),
1361         StmtKind::Item(item) => folder.fold_item(item).into_iter().map(StmtKind::Item).collect(),
1362         StmtKind::Expr(expr) => {
1363             folder.fold_opt_expr(expr).into_iter().map(StmtKind::Expr).collect()
1364         }
1365         StmtKind::Semi(expr) => {
1366             folder.fold_opt_expr(expr).into_iter().map(StmtKind::Semi).collect()
1367         }
1368         StmtKind::Mac(mac) => SmallVector::one(StmtKind::Mac(mac.map(|(mac, semi, attrs)| {
1369             (folder.fold_mac(mac), semi, fold_attrs(attrs.into(), folder).into())
1370         }))),
1371     }
1372 }
1373
1374 pub fn noop_fold_vis<T: Folder>(vis: Visibility, folder: &mut T) -> Visibility {
1375     match vis.node {
1376         VisibilityKind::Restricted { path, id } => {
1377             respan(vis.span, VisibilityKind::Restricted {
1378                 path: path.map(|path| folder.fold_path(path)),
1379                 id: folder.new_id(id),
1380             })
1381         }
1382         _ => vis,
1383     }
1384 }
1385
1386 #[cfg(test)]
1387 mod tests {
1388     use std::io;
1389     use ast::{self, Ident};
1390     use util::parser_testing::{string_to_crate, matches_codepattern};
1391     use print::pprust;
1392     use fold;
1393     use with_globals;
1394     use super::*;
1395
1396     // this version doesn't care about getting comments or docstrings in.
1397     fn fake_print_crate(s: &mut pprust::State,
1398                         krate: &ast::Crate) -> io::Result<()> {
1399         s.print_mod(&krate.module, &krate.attrs)
1400     }
1401
1402     // change every identifier to "zz"
1403     struct ToZzIdentFolder;
1404
1405     impl Folder for ToZzIdentFolder {
1406         fn fold_ident(&mut self, _: ast::Ident) -> ast::Ident {
1407             Ident::from_str("zz")
1408         }
1409         fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
1410             fold::noop_fold_mac(mac, self)
1411         }
1412     }
1413
1414     // maybe add to expand.rs...
1415     macro_rules! assert_pred {
1416         ($pred:expr, $predname:expr, $a:expr , $b:expr) => (
1417             {
1418                 let pred_val = $pred;
1419                 let a_val = $a;
1420                 let b_val = $b;
1421                 if !(pred_val(&a_val, &b_val)) {
1422                     panic!("expected args satisfying {}, got {} and {}",
1423                           $predname, a_val, b_val);
1424                 }
1425             }
1426         )
1427     }
1428
1429     // make sure idents get transformed everywhere
1430     #[test] fn ident_transformation () {
1431         with_globals(|| {
1432             let mut zz_fold = ToZzIdentFolder;
1433             let ast = string_to_crate(
1434                 "#[a] mod b {fn c (d : e, f : g) {h!(i,j,k);l;m}}".to_string());
1435             let folded_crate = zz_fold.fold_crate(ast);
1436             assert_pred!(
1437                 matches_codepattern,
1438                 "matches_codepattern",
1439                 pprust::to_string(|s| fake_print_crate(s, &folded_crate)),
1440                 "#[zz]mod zz{fn zz(zz:zz,zz:zz){zz!(zz,zz,zz);zz;zz}}".to_string());
1441         })
1442     }
1443
1444     // even inside macro defs....
1445     #[test] fn ident_transformation_in_defs () {
1446         with_globals(|| {
1447             let mut zz_fold = ToZzIdentFolder;
1448             let ast = string_to_crate(
1449                 "macro_rules! a {(b $c:expr $(d $e:token)f+ => \
1450                 (g $(d $d $e)+))} ".to_string());
1451             let folded_crate = zz_fold.fold_crate(ast);
1452             assert_pred!(
1453                 matches_codepattern,
1454                 "matches_codepattern",
1455                 pprust::to_string(|s| fake_print_crate(s, &folded_crate)),
1456                 "macro_rules! zz((zz$zz:zz$(zz $zz:zz)zz+=>(zz$(zz$zz$zz)+)));".to_string());
1457         })
1458     }
1459 }