src/librustc/hir/lowering.rs

   1 // Copyright 2015 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 // Lowers the AST to the HIR.
  12 //
  13 // Since the AST and HIR are fairly similar, this is mostly a simple procedure,
  14 // much like a fold. Where lowering involves a bit more work things get more
  15 // interesting and there are some invariants you should know about. These mostly
  16 // concern spans and ids.
  17 //
  18 // Spans are assigned to AST nodes during parsing and then are modified during
  19 // expansion to indicate the origin of a node and the process it went through
  20 // being expanded. Ids are assigned to AST nodes just before lowering.
  21 //
  22 // For the simpler lowering steps, ids and spans should be preserved. Unlike
  23 // expansion we do not preserve the process of lowering in the spans, so spans
  24 // should not be modified here. When creating a new node (as opposed to
  25 // 'folding' an existing one), then you create a new id using `next_id()`.
  26 //
  27 // You must ensure that ids are unique. That means that you should only use the
  28 // id from an AST node in a single HIR node (you can assume that AST node ids
  29 // are unique). Every new node must have a unique id. Avoid cloning HIR nodes.
  30 // If you do, you must then set the new node's id to a fresh one.
  31 //
  32 // Spans are used for error messages and for tools to map semantics back to
  33 // source code. It is therefore not as important with spans as ids to be strict
  34 // about use (you can't break the compiler by screwing up a span). Obviously, a
  35 // HIR node can only have a single span. But multiple nodes can have the same
  36 // span and spans don't need to be kept in order, etc. Where code is preserved
  37 // by lowering, it should have the same span as in the AST. Where HIR nodes are
  38 // new it is probably best to give a span for the whole AST node being lowered.
  39 // All nodes should have real spans, don't use dummy spans. Tools are likely to
  40 // get confused if the spans from leaf AST nodes occur in multiple places
  41 // in the HIR, especially for multiple identifiers.
  42
  43 use hir;
  44 use hir::map::Definitions;
  45 use hir::map::definitions::DefPathData;
  46 use hir::def_id::{DefIndex, DefId};
  47 use hir::def::{Def, PathResolution};
  48 use session::Session;
  49
  50 use std::collections::BTreeMap;
  51 use std::iter;
  52 use syntax::ast::*;
  53 use syntax::errors;
  54 use syntax::ptr::P;
  55 use syntax::codemap::{respan, Spanned};
  56 use syntax::parse::token;
  57 use syntax::std_inject;
  58 use syntax::visit::{self, Visitor};
  59 use syntax_pos::Span;
  60
  61 pub struct LoweringContext<'a> {
  62     crate_root: Option<&'static str>,
  63     // Use to assign ids to hir nodes that do not directly correspond to an ast node
  64     sess: Option<&'a Session>,
  65     // As we walk the AST we must keep track of the current 'parent' def id (in
  66     // the form of a DefIndex) so that if we create a new node which introduces
  67     // a definition, then we can properly create the def id.
  68     parent_def: Option<DefIndex>,
  69     resolver: &'a mut Resolver,
  70 }
  71
  72 pub trait Resolver {
  73     // Resolve a global hir path generated by the lowerer when expanding `for`, `if let`, etc.
  74     fn resolve_generated_global_path(&mut self, path: &hir::Path, is_value: bool) -> Def;
  75
  76     // Obtain the resolution for a node id
  77     fn get_resolution(&mut self, id: NodeId) -> Option<PathResolution>;
  78
  79     // Record the resolution of a path or binding generated by the lowerer when expanding.
  80     fn record_resolution(&mut self, id: NodeId, def: Def);
  81
  82     // We must keep the set of definitions up to date as we add nodes that weren't in the AST.
  83     // This should only return `None` during testing.
  84     fn definitions(&mut self) -> Option<&mut Definitions>;
  85 }
  86
  87 pub struct DummyResolver;
  88 impl Resolver for DummyResolver {
  89     fn resolve_generated_global_path(&mut self, _path: &hir::Path, _is_value: bool) -> Def {
  90         Def::Err
  91     }
  92     fn get_resolution(&mut self, _id: NodeId) -> Option<PathResolution> {
  93         None
  94     }
  95     fn record_resolution(&mut self, _id: NodeId, _def: Def) {}
  96     fn definitions(&mut self) -> Option<&mut Definitions> {
  97         None
  98     }
  99 }
 100
 101 pub fn lower_crate(sess: &Session,
 102                    krate: &Crate,
 103                    resolver: &mut Resolver)
 104                    -> hir::Crate {
 105     // We're constructing the HIR here; we don't care what we will
 106     // read, since we haven't even constructed the *input* to
 107     // incr. comp. yet.
 108     let _ignore = sess.dep_graph.in_ignore();
 109
 110     LoweringContext {
 111         crate_root: if std_inject::no_core(krate) {
 112             None
 113         } else if std_inject::no_std(krate) {
 114             Some("core")
 115         } else {
 116             Some("std")
 117         },
 118         sess: Some(sess),
 119         parent_def: None,
 120         resolver: resolver,
 121     }.lower_crate(krate)
 122 }
 123
 124 impl<'a> LoweringContext<'a> {
 125     pub fn testing_context(resolver: &'a mut Resolver) -> Self {
 126         LoweringContext {
 127             crate_root: None,
 128             sess: None,
 129             parent_def: None,
 130             resolver: resolver,
 131         }
 132     }
 133
 134     fn lower_crate(&mut self, c: &Crate) -> hir::Crate {
 135         struct ItemLowerer<'lcx, 'interner: 'lcx> {
 136             items: BTreeMap<NodeId, hir::Item>,
 137             lctx: &'lcx mut LoweringContext<'interner>,
 138         }
 139
 140         impl<'lcx, 'interner> Visitor for ItemLowerer<'lcx, 'interner> {
 141             fn visit_item(&mut self, item: &Item) {
 142                 self.items.insert(item.id, self.lctx.lower_item(item));
 143                 visit::walk_item(self, item);
 144             }
 145         }
 146
 147         let items = {
 148             let mut item_lowerer = ItemLowerer { items: BTreeMap::new(), lctx: self };
 149             visit::walk_crate(&mut item_lowerer, c);
 150             item_lowerer.items
 151         };
 152
 153         hir::Crate {
 154             module: self.lower_mod(&c.module),
 155             attrs: self.lower_attrs(&c.attrs),
 156             config: c.config.clone().into(),
 157             span: c.span,
 158             exported_macros: c.exported_macros.iter().map(|m| self.lower_macro_def(m)).collect(),
 159             items: items,
 160         }
 161     }
 162
 163     fn next_id(&self) -> NodeId {
 164         self.sess.map(Session::next_node_id).unwrap_or(0)
 165     }
 166
 167     fn diagnostic(&self) -> &errors::Handler {
 168         self.sess.map(Session::diagnostic)
 169                  .unwrap_or_else(|| panic!("this lowerer cannot emit diagnostics"))
 170     }
 171
 172     fn str_to_ident(&self, s: &'static str) -> Name {
 173         token::gensym(s)
 174     }
 175
 176     fn with_parent_def<T, F>(&mut self, parent_id: NodeId, f: F) -> T
 177         where F: FnOnce(&mut LoweringContext) -> T
 178     {
 179         let old_def = self.parent_def;
 180         self.parent_def = match self.resolver.definitions() {
 181             Some(defs) => Some(defs.opt_def_index(parent_id).unwrap()),
 182             None => old_def,
 183         };
 184
 185         let result = f(self);
 186
 187         self.parent_def = old_def;
 188         result
 189     }
 190
 191     fn lower_opt_sp_ident(&mut self, o_id: Option<Spanned<Ident>>) -> Option<Spanned<Name>> {
 192         o_id.map(|sp_ident| respan(sp_ident.span, sp_ident.node.name))
 193     }
 194
 195     fn lower_attrs(&mut self, attrs: &Vec<Attribute>) -> hir::HirVec<Attribute> {
 196         attrs.clone().into()
 197     }
 198
 199     fn lower_view_path(&mut self, view_path: &ViewPath) -> P<hir::ViewPath> {
 200         P(Spanned {
 201             node: match view_path.node {
 202                 ViewPathSimple(ident, ref path) => {
 203                     hir::ViewPathSimple(ident.name, self.lower_path(path))
 204                 }
 205                 ViewPathGlob(ref path) => {
 206                     hir::ViewPathGlob(self.lower_path(path))
 207                 }
 208                 ViewPathList(ref path, ref path_list_idents) => {
 209                     hir::ViewPathList(self.lower_path(path),
 210                                       path_list_idents.iter()
 211                                                       .map(|item| self.lower_path_list_item(item))
 212                                                       .collect())
 213                 }
 214             },
 215             span: view_path.span,
 216         })
 217     }
 218
 219     fn lower_path_list_item(&mut self, path_list_ident: &PathListItem) -> hir::PathListItem {
 220         Spanned {
 221             node: hir::PathListItem_ {
 222                 id: path_list_ident.node.id,
 223                 name: path_list_ident.node.name.name,
 224                 rename: path_list_ident.node.rename.map(|rename| rename.name),
 225             },
 226             span: path_list_ident.span,
 227         }
 228     }
 229
 230     fn lower_arm(&mut self, arm: &Arm) -> hir::Arm {
 231         hir::Arm {
 232             attrs: self.lower_attrs(&arm.attrs),
 233             pats: arm.pats.iter().map(|x| self.lower_pat(x)).collect(),
 234             guard: arm.guard.as_ref().map(|ref x| self.lower_expr(x)),
 235             body: self.lower_expr(&arm.body),
 236         }
 237     }
 238
 239     fn lower_ty_binding(&mut self, b: &TypeBinding) -> hir::TypeBinding {
 240         hir::TypeBinding {
 241             id: b.id,
 242             name: b.ident.name,
 243             ty: self.lower_ty(&b.ty),
 244             span: b.span,
 245         }
 246     }
 247
 248     fn lower_ty(&mut self, t: &Ty) -> P<hir::Ty> {
 249         use syntax::ast::TyKind::*;
 250         P(hir::Ty {
 251             id: t.id,
 252             node: match t.node {
 253                 Infer | ImplicitSelf => hir::TyInfer,
 254                 Vec(ref ty) => hir::TyVec(self.lower_ty(ty)),
 255                 Ptr(ref mt) => hir::TyPtr(self.lower_mt(mt)),
 256                 Rptr(ref region, ref mt) => {
 257                     hir::TyRptr(self.lower_opt_lifetime(region), self.lower_mt(mt))
 258                 }
 259                 BareFn(ref f) => {
 260                     hir::TyBareFn(P(hir::BareFnTy {
 261                         lifetimes: self.lower_lifetime_defs(&f.lifetimes),
 262                         unsafety: self.lower_unsafety(f.unsafety),
 263                         abi: f.abi,
 264                         decl: self.lower_fn_decl(&f.decl),
 265                     }))
 266                 }
 267                 Never => hir::TyNever,
 268                 Tup(ref tys) => hir::TyTup(tys.iter().map(|ty| self.lower_ty(ty)).collect()),
 269                 Paren(ref ty) => {
 270                     return self.lower_ty(ty);
 271                 }
 272                 Path(ref qself, ref path) => {
 273                     let qself = qself.as_ref().map(|&QSelf { ref ty, position }| {
 274                         hir::QSelf {
 275                             ty: self.lower_ty(ty),
 276                             position: position,
 277                         }
 278                     });
 279                     hir::TyPath(qself, self.lower_path(path))
 280                 }
 281                 ObjectSum(ref ty, ref bounds) => {
 282                     hir::TyObjectSum(self.lower_ty(ty), self.lower_bounds(bounds))
 283                 }
 284                 FixedLengthVec(ref ty, ref e) => {
 285                     hir::TyFixedLengthVec(self.lower_ty(ty), self.lower_expr(e))
 286                 }
 287                 Typeof(ref expr) => {
 288                     hir::TyTypeof(self.lower_expr(expr))
 289                 }
 290                 PolyTraitRef(ref bounds) => {
 291                     hir::TyPolyTraitRef(self.lower_bounds(bounds))
 292                 }
 293                 ImplTrait(ref bounds) => {
 294                     hir::TyImplTrait(self.lower_bounds(bounds))
 295                 }
 296                 Mac(_) => panic!("TyMac should have been expanded by now."),
 297             },
 298             span: t.span,
 299         })
 300     }
 301
 302     fn lower_foreign_mod(&mut self, fm: &ForeignMod) -> hir::ForeignMod {
 303         hir::ForeignMod {
 304             abi: fm.abi,
 305             items: fm.items.iter().map(|x| self.lower_foreign_item(x)).collect(),
 306         }
 307     }
 308
 309     fn lower_variant(&mut self, v: &Variant) -> hir::Variant {
 310         Spanned {
 311             node: hir::Variant_ {
 312                 name: v.node.name.name,
 313                 attrs: self.lower_attrs(&v.node.attrs),
 314                 data: self.lower_variant_data(&v.node.data),
 315                 disr_expr: v.node.disr_expr.as_ref().map(|e| self.lower_expr(e)),
 316             },
 317             span: v.span,
 318         }
 319     }
 320
 321     fn lower_path(&mut self, p: &Path) -> hir::Path {
 322         hir::Path {
 323             global: p.global,
 324             segments: p.segments
 325                        .iter()
 326                        .map(|&PathSegment { identifier, ref parameters }| {
 327                            hir::PathSegment {
 328                                name: identifier.name,
 329                                parameters: self.lower_path_parameters(parameters),
 330                            }
 331                        })
 332                        .collect(),
 333             span: p.span,
 334         }
 335     }
 336
 337     fn lower_path_parameters(&mut self, path_parameters: &PathParameters) -> hir::PathParameters {
 338         match *path_parameters {
 339             PathParameters::AngleBracketed(ref data) =>
 340                 hir::AngleBracketedParameters(self.lower_angle_bracketed_parameter_data(data)),
 341             PathParameters::Parenthesized(ref data) =>
 342                 hir::ParenthesizedParameters(self.lower_parenthesized_parameter_data(data)),
 343         }
 344     }
 345
 346     fn lower_angle_bracketed_parameter_data(&mut self,
 347                                             data: &AngleBracketedParameterData)
 348                                             -> hir::AngleBracketedParameterData {
 349         let &AngleBracketedParameterData { ref lifetimes, ref types, ref bindings } = data;
 350         hir::AngleBracketedParameterData {
 351             lifetimes: self.lower_lifetimes(lifetimes),
 352             types: types.iter().map(|ty| self.lower_ty(ty)).collect(),
 353             bindings: bindings.iter().map(|b| self.lower_ty_binding(b)).collect(),
 354         }
 355     }
 356
 357     fn lower_parenthesized_parameter_data(&mut self,
 358                                           data: &ParenthesizedParameterData)
 359                                           -> hir::ParenthesizedParameterData {
 360         let &ParenthesizedParameterData { ref inputs, ref output, span } = data;
 361         hir::ParenthesizedParameterData {
 362             inputs: inputs.iter().map(|ty| self.lower_ty(ty)).collect(),
 363             output: output.as_ref().map(|ty| self.lower_ty(ty)),
 364             span: span,
 365         }
 366     }
 367
 368     fn lower_local(&mut self, l: &Local) -> P<hir::Local> {
 369         P(hir::Local {
 370             id: l.id,
 371             ty: l.ty.as_ref().map(|t| self.lower_ty(t)),
 372             pat: self.lower_pat(&l.pat),
 373             init: l.init.as_ref().map(|e| self.lower_expr(e)),
 374             span: l.span,
 375             attrs: l.attrs.clone(),
 376         })
 377     }
 378
 379     fn lower_mutability(&mut self, m: Mutability) -> hir::Mutability {
 380         match m {
 381             Mutability::Mutable => hir::MutMutable,
 382             Mutability::Immutable => hir::MutImmutable,
 383         }
 384     }
 385
 386     fn lower_arg(&mut self, arg: &Arg) -> hir::Arg {
 387         hir::Arg {
 388             id: arg.id,
 389             pat: self.lower_pat(&arg.pat),
 390             ty: self.lower_ty(&arg.ty),
 391         }
 392     }
 393
 394     fn lower_fn_decl(&mut self, decl: &FnDecl) -> P<hir::FnDecl> {
 395         P(hir::FnDecl {
 396             inputs: decl.inputs.iter().map(|x| self.lower_arg(x)).collect(),
 397             output: match decl.output {
 398                 FunctionRetTy::Ty(ref ty) => hir::Return(self.lower_ty(ty)),
 399                 FunctionRetTy::Default(span) => hir::DefaultReturn(span),
 400             },
 401             variadic: decl.variadic,
 402         })
 403     }
 404
 405     fn lower_ty_param_bound(&mut self, tpb: &TyParamBound) -> hir::TyParamBound {
 406         match *tpb {
 407             TraitTyParamBound(ref ty, modifier) => {
 408                 hir::TraitTyParamBound(self.lower_poly_trait_ref(ty),
 409                                        self.lower_trait_bound_modifier(modifier))
 410             }
 411             RegionTyParamBound(ref lifetime) => {
 412                 hir::RegionTyParamBound(self.lower_lifetime(lifetime))
 413             }
 414         }
 415     }
 416
 417     fn lower_ty_param(&mut self, tp: &TyParam) -> hir::TyParam {
 418         hir::TyParam {
 419             id: tp.id,
 420             name: tp.ident.name,
 421             bounds: self.lower_bounds(&tp.bounds),
 422             default: tp.default.as_ref().map(|x| self.lower_ty(x)),
 423             span: tp.span,
 424         }
 425     }
 426
 427     fn lower_ty_params(&mut self, tps: &P<[TyParam]>) -> hir::HirVec<hir::TyParam> {
 428         tps.iter().map(|tp| self.lower_ty_param(tp)).collect()
 429     }
 430
 431     fn lower_lifetime(&mut self, l: &Lifetime) -> hir::Lifetime {
 432         hir::Lifetime {
 433             id: l.id,
 434             name: l.name,
 435             span: l.span,
 436         }
 437     }
 438
 439     fn lower_lifetime_def(&mut self, l: &LifetimeDef) -> hir::LifetimeDef {
 440         hir::LifetimeDef {
 441             lifetime: self.lower_lifetime(&l.lifetime),
 442             bounds: self.lower_lifetimes(&l.bounds),
 443         }
 444     }
 445
 446     fn lower_lifetimes(&mut self, lts: &Vec<Lifetime>) -> hir::HirVec<hir::Lifetime> {
 447         lts.iter().map(|l| self.lower_lifetime(l)).collect()
 448     }
 449
 450     fn lower_lifetime_defs(&mut self, lts: &Vec<LifetimeDef>) -> hir::HirVec<hir::LifetimeDef> {
 451         lts.iter().map(|l| self.lower_lifetime_def(l)).collect()
 452     }
 453
 454     fn lower_opt_lifetime(&mut self, o_lt: &Option<Lifetime>) -> Option<hir::Lifetime> {
 455         o_lt.as_ref().map(|lt| self.lower_lifetime(lt))
 456     }
 457
 458     fn lower_generics(&mut self, g: &Generics) -> hir::Generics {
 459         hir::Generics {
 460             ty_params: self.lower_ty_params(&g.ty_params),
 461             lifetimes: self.lower_lifetime_defs(&g.lifetimes),
 462             where_clause: self.lower_where_clause(&g.where_clause),
 463         }
 464     }
 465
 466     fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause {
 467         hir::WhereClause {
 468             id: wc.id,
 469             predicates: wc.predicates
 470                           .iter()
 471                           .map(|predicate| self.lower_where_predicate(predicate))
 472                           .collect(),
 473         }
 474     }
 475
 476     fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate {
 477         match *pred {
 478             WherePredicate::BoundPredicate(WhereBoundPredicate{ ref bound_lifetimes,
 479                                                                 ref bounded_ty,
 480                                                                 ref bounds,
 481                                                                 span}) => {
 482                 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
 483                     bound_lifetimes: self.lower_lifetime_defs(bound_lifetimes),
 484                     bounded_ty: self.lower_ty(bounded_ty),
 485                     bounds: bounds.iter().map(|x| self.lower_ty_param_bound(x)).collect(),
 486                     span: span,
 487                 })
 488             }
 489             WherePredicate::RegionPredicate(WhereRegionPredicate{ ref lifetime,
 490                                                                   ref bounds,
 491                                                                   span}) => {
 492                 hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
 493                     span: span,
 494                     lifetime: self.lower_lifetime(lifetime),
 495                     bounds: bounds.iter().map(|bound| self.lower_lifetime(bound)).collect(),
 496                 })
 497             }
 498             WherePredicate::EqPredicate(WhereEqPredicate{ id,
 499                                                           ref path,
 500                                                           ref ty,
 501                                                           span}) => {
 502                 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
 503                     id: id,
 504                     path: self.lower_path(path),
 505                     ty: self.lower_ty(ty),
 506                     span: span,
 507                 })
 508             }
 509         }
 510     }
 511
 512     fn lower_variant_data(&mut self, vdata: &VariantData) -> hir::VariantData {
 513         match *vdata {
 514             VariantData::Struct(ref fields, id) => {
 515                 hir::VariantData::Struct(fields.iter()
 516                                                .enumerate()
 517                                                .map(|f| self.lower_struct_field(f))
 518                                                .collect(),
 519                                          id)
 520             }
 521             VariantData::Tuple(ref fields, id) => {
 522                 hir::VariantData::Tuple(fields.iter()
 523                                               .enumerate()
 524                                               .map(|f| self.lower_struct_field(f))
 525                                               .collect(),
 526                                         id)
 527             }
 528             VariantData::Unit(id) => hir::VariantData::Unit(id),
 529         }
 530     }
 531
 532     fn lower_trait_ref(&mut self, p: &TraitRef) -> hir::TraitRef {
 533         hir::TraitRef {
 534             path: self.lower_path(&p.path),
 535             ref_id: p.ref_id,
 536         }
 537     }
 538
 539     fn lower_poly_trait_ref(&mut self, p: &PolyTraitRef) -> hir::PolyTraitRef {
 540         hir::PolyTraitRef {
 541             bound_lifetimes: self.lower_lifetime_defs(&p.bound_lifetimes),
 542             trait_ref: self.lower_trait_ref(&p.trait_ref),
 543             span: p.span,
 544         }
 545     }
 546
 547     fn lower_struct_field(&mut self, (index, f): (usize, &StructField)) -> hir::StructField {
 548         hir::StructField {
 549             span: f.span,
 550             id: f.id,
 551             name: f.ident.map(|ident| ident.name).unwrap_or(token::intern(&index.to_string())),
 552             vis: self.lower_visibility(&f.vis),
 553             ty: self.lower_ty(&f.ty),
 554             attrs: self.lower_attrs(&f.attrs),
 555         }
 556     }
 557
 558     fn lower_field(&mut self, f: &Field) -> hir::Field {
 559         hir::Field {
 560             name: respan(f.ident.span, f.ident.node.name),
 561             expr: self.lower_expr(&f.expr),
 562             span: f.span,
 563         }
 564     }
 565
 566     fn lower_mt(&mut self, mt: &MutTy) -> hir::MutTy {
 567         hir::MutTy {
 568             ty: self.lower_ty(&mt.ty),
 569             mutbl: self.lower_mutability(mt.mutbl),
 570         }
 571     }
 572
 573     fn lower_bounds(&mut self, bounds: &TyParamBounds) -> hir::TyParamBounds {
 574         bounds.iter().map(|bound| self.lower_ty_param_bound(bound)).collect()
 575     }
 576
 577     fn lower_block(&mut self, b: &Block) -> P<hir::Block> {
 578         let mut stmts = Vec::new();
 579         let mut expr = None;
 580
 581         if let Some((last, rest)) = b.stmts.split_last() {
 582             stmts = rest.iter().map(|s| self.lower_stmt(s)).collect::<Vec<_>>();
 583             let last = self.lower_stmt(last);
 584             if let hir::StmtExpr(e, _) = last.node {
 585                 expr = Some(e);
 586             } else {
 587                 stmts.push(last);
 588             }
 589         }
 590
 591         P(hir::Block {
 592             id: b.id,
 593             stmts: stmts.into(),
 594             expr: expr,
 595             rules: self.lower_block_check_mode(&b.rules),
 596             span: b.span,
 597         })
 598     }
 599
 600     fn lower_item_kind(&mut self, i: &ItemKind) -> hir::Item_ {
 601         match *i {
 602             ItemKind::ExternCrate(string) => hir::ItemExternCrate(string),
 603             ItemKind::Use(ref view_path) => {
 604                 hir::ItemUse(self.lower_view_path(view_path))
 605             }
 606             ItemKind::Static(ref t, m, ref e) => {
 607                 hir::ItemStatic(self.lower_ty(t),
 608                                 self.lower_mutability(m),
 609                                 self.lower_expr(e))
 610             }
 611             ItemKind::Const(ref t, ref e) => {
 612                 hir::ItemConst(self.lower_ty(t), self.lower_expr(e))
 613             }
 614             ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 615                 hir::ItemFn(self.lower_fn_decl(decl),
 616                             self.lower_unsafety(unsafety),
 617                             self.lower_constness(constness),
 618                             abi,
 619                             self.lower_generics(generics),
 620                             self.lower_block(body))
 621             }
 622             ItemKind::Mod(ref m) => hir::ItemMod(self.lower_mod(m)),
 623             ItemKind::ForeignMod(ref nm) => hir::ItemForeignMod(self.lower_foreign_mod(nm)),
 624             ItemKind::Ty(ref t, ref generics) => {
 625                 hir::ItemTy(self.lower_ty(t), self.lower_generics(generics))
 626             }
 627             ItemKind::Enum(ref enum_definition, ref generics) => {
 628                 hir::ItemEnum(hir::EnumDef {
 629                                   variants: enum_definition.variants
 630                                                            .iter()
 631                                                            .map(|x| self.lower_variant(x))
 632                                                            .collect(),
 633                               },
 634                               self.lower_generics(generics))
 635             }
 636             ItemKind::Struct(ref struct_def, ref generics) => {
 637                 let struct_def = self.lower_variant_data(struct_def);
 638                 hir::ItemStruct(struct_def, self.lower_generics(generics))
 639             }
 640             ItemKind::DefaultImpl(unsafety, ref trait_ref) => {
 641                 hir::ItemDefaultImpl(self.lower_unsafety(unsafety),
 642                                      self.lower_trait_ref(trait_ref))
 643             }
 644             ItemKind::Impl(unsafety, polarity, ref generics, ref ifce, ref ty, ref impl_items) => {
 645                 let new_impl_items = impl_items.iter()
 646                                                .map(|item| self.lower_impl_item(item))
 647                                                .collect();
 648                 let ifce = ifce.as_ref().map(|trait_ref| self.lower_trait_ref(trait_ref));
 649                 hir::ItemImpl(self.lower_unsafety(unsafety),
 650                               self.lower_impl_polarity(polarity),
 651                               self.lower_generics(generics),
 652                               ifce,
 653                               self.lower_ty(ty),
 654                               new_impl_items)
 655             }
 656             ItemKind::Trait(unsafety, ref generics, ref bounds, ref items) => {
 657                 let bounds = self.lower_bounds(bounds);
 658                 let items = items.iter().map(|item| self.lower_trait_item(item)).collect();
 659                 hir::ItemTrait(self.lower_unsafety(unsafety),
 660                                self.lower_generics(generics),
 661                                bounds,
 662                                items)
 663             }
 664             ItemKind::Mac(_) => panic!("Shouldn't still be around"),
 665         }
 666     }
 667
 668     fn lower_trait_item(&mut self, i: &TraitItem) -> hir::TraitItem {
 669         self.with_parent_def(i.id, |this| {
 670             hir::TraitItem {
 671                 id: i.id,
 672                 name: i.ident.name,
 673                 attrs: this.lower_attrs(&i.attrs),
 674                 node: match i.node {
 675                     TraitItemKind::Const(ref ty, ref default) => {
 676                         hir::ConstTraitItem(this.lower_ty(ty),
 677                                             default.as_ref().map(|x| this.lower_expr(x)))
 678                     }
 679                     TraitItemKind::Method(ref sig, ref body) => {
 680                         hir::MethodTraitItem(this.lower_method_sig(sig),
 681                                              body.as_ref().map(|x| this.lower_block(x)))
 682                     }
 683                     TraitItemKind::Type(ref bounds, ref default) => {
 684                         hir::TypeTraitItem(this.lower_bounds(bounds),
 685                                            default.as_ref().map(|x| this.lower_ty(x)))
 686                     }
 687                     TraitItemKind::Macro(..) => panic!("Shouldn't exist any more"),
 688                 },
 689                 span: i.span,
 690             }
 691         })
 692     }
 693
 694     fn lower_impl_item(&mut self, i: &ImplItem) -> hir::ImplItem {
 695         self.with_parent_def(i.id, |this| {
 696             hir::ImplItem {
 697                 id: i.id,
 698                 name: i.ident.name,
 699                 attrs: this.lower_attrs(&i.attrs),
 700                 vis: this.lower_visibility(&i.vis),
 701                 defaultness: this.lower_defaultness(i.defaultness),
 702                 node: match i.node {
 703                     ImplItemKind::Const(ref ty, ref expr) => {
 704                         hir::ImplItemKind::Const(this.lower_ty(ty), this.lower_expr(expr))
 705                     }
 706                     ImplItemKind::Method(ref sig, ref body) => {
 707                         hir::ImplItemKind::Method(this.lower_method_sig(sig),
 708                                                   this.lower_block(body))
 709                     }
 710                     ImplItemKind::Type(ref ty) => hir::ImplItemKind::Type(this.lower_ty(ty)),
 711                     ImplItemKind::Macro(..) => panic!("Shouldn't exist any more"),
 712                 },
 713                 span: i.span,
 714             }
 715         })
 716     }
 717
 718     fn lower_mod(&mut self, m: &Mod) -> hir::Mod {
 719         hir::Mod {
 720             inner: m.inner,
 721             item_ids: m.items.iter().map(|x| self.lower_item_id(x)).collect(),
 722         }
 723     }
 724
 725     fn lower_macro_def(&mut self, m: &MacroDef) -> hir::MacroDef {
 726         hir::MacroDef {
 727             name: m.ident.name,
 728             attrs: self.lower_attrs(&m.attrs),
 729             id: m.id,
 730             span: m.span,
 731             imported_from: m.imported_from.map(|x| x.name),
 732             export: m.export,
 733             use_locally: m.use_locally,
 734             allow_internal_unstable: m.allow_internal_unstable,
 735             body: m.body.clone().into(),
 736         }
 737     }
 738
 739     fn lower_item_id(&mut self, i: &Item) -> hir::ItemId {
 740         hir::ItemId { id: i.id }
 741     }
 742
 743     pub fn lower_item(&mut self, i: &Item) -> hir::Item {
 744         let node = self.with_parent_def(i.id, |this| {
 745             this.lower_item_kind(&i.node)
 746         });
 747
 748         hir::Item {
 749             id: i.id,
 750             name: i.ident.name,
 751             attrs: self.lower_attrs(&i.attrs),
 752             node: node,
 753             vis: self.lower_visibility(&i.vis),
 754             span: i.span,
 755         }
 756     }
 757
 758     fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem {
 759         self.with_parent_def(i.id, |this| {
 760             hir::ForeignItem {
 761                 id: i.id,
 762                 name: i.ident.name,
 763                 attrs: this.lower_attrs(&i.attrs),
 764                 node: match i.node {
 765                     ForeignItemKind::Fn(ref fdec, ref generics) => {
 766                         hir::ForeignItemFn(this.lower_fn_decl(fdec), this.lower_generics(generics))
 767                     }
 768                     ForeignItemKind::Static(ref t, m) => {
 769                         hir::ForeignItemStatic(this.lower_ty(t), m)
 770                     }
 771                 },
 772                 vis: this.lower_visibility(&i.vis),
 773                 span: i.span,
 774             }
 775         })
 776     }
 777
 778     fn lower_method_sig(&mut self, sig: &MethodSig) -> hir::MethodSig {
 779         let hir_sig = hir::MethodSig {
 780             generics: self.lower_generics(&sig.generics),
 781             abi: sig.abi,
 782             unsafety: self.lower_unsafety(sig.unsafety),
 783             constness: self.lower_constness(sig.constness),
 784             decl: self.lower_fn_decl(&sig.decl),
 785         };
 786         // Check for `self: _` and `self: &_`
 787         if let Some(SelfKind::Explicit(..)) = sig.decl.get_self().map(|eself| eself.node) {
 788             match hir_sig.decl.get_self().map(|eself| eself.node) {
 789                 Some(hir::SelfKind::Value(..)) | Some(hir::SelfKind::Region(..)) => {
 790                     self.diagnostic().span_err(sig.decl.inputs[0].ty.span,
 791                         "the type placeholder `_` is not allowed within types on item signatures");
 792                 }
 793                 _ => {}
 794             }
 795         }
 796         hir_sig
 797     }
 798
 799     fn lower_unsafety(&mut self, u: Unsafety) -> hir::Unsafety {
 800         match u {
 801             Unsafety::Unsafe => hir::Unsafety::Unsafe,
 802             Unsafety::Normal => hir::Unsafety::Normal,
 803         }
 804     }
 805
 806     fn lower_constness(&mut self, c: Constness) -> hir::Constness {
 807         match c {
 808             Constness::Const => hir::Constness::Const,
 809             Constness::NotConst => hir::Constness::NotConst,
 810         }
 811     }
 812
 813     fn lower_unop(&mut self, u: UnOp) -> hir::UnOp {
 814         match u {
 815             UnOp::Deref => hir::UnDeref,
 816             UnOp::Not => hir::UnNot,
 817             UnOp::Neg => hir::UnNeg,
 818         }
 819     }
 820
 821     fn lower_binop(&mut self, b: BinOp) -> hir::BinOp {
 822         Spanned {
 823             node: match b.node {
 824                 BinOpKind::Add => hir::BiAdd,
 825                 BinOpKind::Sub => hir::BiSub,
 826                 BinOpKind::Mul => hir::BiMul,
 827                 BinOpKind::Div => hir::BiDiv,
 828                 BinOpKind::Rem => hir::BiRem,
 829                 BinOpKind::And => hir::BiAnd,
 830                 BinOpKind::Or => hir::BiOr,
 831                 BinOpKind::BitXor => hir::BiBitXor,
 832                 BinOpKind::BitAnd => hir::BiBitAnd,
 833                 BinOpKind::BitOr => hir::BiBitOr,
 834                 BinOpKind::Shl => hir::BiShl,
 835                 BinOpKind::Shr => hir::BiShr,
 836                 BinOpKind::Eq => hir::BiEq,
 837                 BinOpKind::Lt => hir::BiLt,
 838                 BinOpKind::Le => hir::BiLe,
 839                 BinOpKind::Ne => hir::BiNe,
 840                 BinOpKind::Ge => hir::BiGe,
 841                 BinOpKind::Gt => hir::BiGt,
 842             },
 843             span: b.span,
 844         }
 845     }
 846
 847     fn lower_pat(&mut self, p: &Pat) -> P<hir::Pat> {
 848         P(hir::Pat {
 849             id: p.id,
 850             node: match p.node {
 851                 PatKind::Wild => hir::PatKind::Wild,
 852                 PatKind::Ident(ref binding_mode, pth1, ref sub) => {
 853                     self.with_parent_def(p.id, |this| {
 854                         match this.resolver.get_resolution(p.id).map(|d| d.base_def) {
 855                             // `None` can occur in body-less function signatures
 856                             None | Some(Def::Local(..)) => {
 857                                 hir::PatKind::Binding(this.lower_binding_mode(binding_mode),
 858                                                       respan(pth1.span, pth1.node.name),
 859                                                       sub.as_ref().map(|x| this.lower_pat(x)))
 860                             }
 861                             _ => hir::PatKind::Path(None, hir::Path::from_name(pth1.span,
 862                                                                                pth1.node.name))
 863                         }
 864                     })
 865                 }
 866                 PatKind::Lit(ref e) => hir::PatKind::Lit(self.lower_expr(e)),
 867                 PatKind::TupleStruct(ref pth, ref pats, ddpos) => {
 868                     hir::PatKind::TupleStruct(self.lower_path(pth),
 869                                               pats.iter().map(|x| self.lower_pat(x)).collect(),
 870                                               ddpos)
 871                 }
 872                 PatKind::Path(ref opt_qself, ref path) => {
 873                     let opt_qself = opt_qself.as_ref().map(|qself| {
 874                         hir::QSelf { ty: self.lower_ty(&qself.ty), position: qself.position }
 875                     });
 876                     hir::PatKind::Path(opt_qself, self.lower_path(path))
 877                 }
 878                 PatKind::Struct(ref pth, ref fields, etc) => {
 879                     let pth = self.lower_path(pth);
 880                     let fs = fields.iter()
 881                                    .map(|f| {
 882                                        Spanned {
 883                                            span: f.span,
 884                                            node: hir::FieldPat {
 885                                                name: f.node.ident.name,
 886                                                pat: self.lower_pat(&f.node.pat),
 887                                                is_shorthand: f.node.is_shorthand,
 888                                            },
 889                                        }
 890                                    })
 891                                    .collect();
 892                     hir::PatKind::Struct(pth, fs, etc)
 893                 }
 894                 PatKind::Tuple(ref elts, ddpos) => {
 895                     hir::PatKind::Tuple(elts.iter().map(|x| self.lower_pat(x)).collect(), ddpos)
 896                 }
 897                 PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)),
 898                 PatKind::Ref(ref inner, mutbl) => {
 899                     hir::PatKind::Ref(self.lower_pat(inner), self.lower_mutability(mutbl))
 900                 }
 901                 PatKind::Range(ref e1, ref e2) => {
 902                     hir::PatKind::Range(self.lower_expr(e1), self.lower_expr(e2))
 903                 }
 904                 PatKind::Vec(ref before, ref slice, ref after) => {
 905                     hir::PatKind::Vec(before.iter().map(|x| self.lower_pat(x)).collect(),
 906                                 slice.as_ref().map(|x| self.lower_pat(x)),
 907                                 after.iter().map(|x| self.lower_pat(x)).collect())
 908                 }
 909                 PatKind::Mac(_) => panic!("Shouldn't exist here"),
 910             },
 911             span: p.span,
 912         })
 913     }
 914
 915     fn lower_expr(&mut self, e: &Expr) -> P<hir::Expr> {
 916         P(hir::Expr {
 917             id: e.id,
 918             node: match e.node {
 919                 // Issue #22181:
 920                 // Eventually a desugaring for `box EXPR`
 921                 // (similar to the desugaring above for `in PLACE BLOCK`)
 922                 // should go here, desugaring
 923                 //
 924                 // to:
 925                 //
 926                 // let mut place = BoxPlace::make_place();
 927                 // let raw_place = Place::pointer(&mut place);
 928                 // let value = $value;
 929                 // unsafe {
 930                 //     ::std::ptr::write(raw_place, value);
 931                 //     Boxed::finalize(place)
 932                 // }
 933                 //
 934                 // But for now there are type-inference issues doing that.
 935                 ExprKind::Box(ref e) => {
 936                     hir::ExprBox(self.lower_expr(e))
 937                 }
 938
 939                 // Desugar ExprBox: `in (PLACE) EXPR`
 940                 ExprKind::InPlace(ref placer, ref value_expr) => {
 941                     // to:
 942                     //
 943                     // let p = PLACE;
 944                     // let mut place = Placer::make_place(p);
 945                     // let raw_place = Place::pointer(&mut place);
 946                     // push_unsafe!({
 947                     //     std::intrinsics::move_val_init(raw_place, pop_unsafe!( EXPR ));
 948                     //     InPlace::finalize(place)
 949                     // })
 950                     let placer_expr = self.lower_expr(placer);
 951                     let value_expr = self.lower_expr(value_expr);
 952
 953                     let placer_ident = self.str_to_ident("placer");
 954                     let place_ident = self.str_to_ident("place");
 955                     let p_ptr_ident = self.str_to_ident("p_ptr");
 956
 957                     let make_place = ["ops", "Placer", "make_place"];
 958                     let place_pointer = ["ops", "Place", "pointer"];
 959                     let move_val_init = ["intrinsics", "move_val_init"];
 960                     let inplace_finalize = ["ops", "InPlace", "finalize"];
 961
 962                     let make_call = |this: &mut LoweringContext, p, args| {
 963                         let path = this.core_path(e.span, p);
 964                         let path = this.expr_path(path, ThinVec::new());
 965                         this.expr_call(e.span, path, args)
 966                     };
 967
 968                     let mk_stmt_let = |this: &mut LoweringContext, bind, expr| {
 969                         this.stmt_let(e.span, false, bind, expr)
 970                     };
 971
 972                     let mk_stmt_let_mut = |this: &mut LoweringContext, bind, expr| {
 973                         this.stmt_let(e.span, true, bind, expr)
 974                     };
 975
 976                     // let placer = <placer_expr> ;
 977                     let (s1, placer_binding) = {
 978                         let placer_expr = self.signal_block_expr(hir_vec![],
 979                                                                  placer_expr,
 980                                                                  e.span,
 981                                                                  hir::PopUnstableBlock,
 982                                                                  ThinVec::new());
 983                         mk_stmt_let(self, placer_ident, placer_expr)
 984                     };
 985
 986                     // let mut place = Placer::make_place(placer);
 987                     let (s2, place_binding) = {
 988                         let placer = self.expr_ident(e.span, placer_ident, placer_binding);
 989                         let call = make_call(self, &make_place, hir_vec![placer]);
 990                         mk_stmt_let_mut(self, place_ident, call)
 991                     };
 992
 993                     // let p_ptr = Place::pointer(&mut place);
 994                     let (s3, p_ptr_binding) = {
 995                         let agent = self.expr_ident(e.span, place_ident, place_binding);
 996                         let args = hir_vec![self.expr_mut_addr_of(e.span, agent)];
 997                         let call = make_call(self, &place_pointer, args);
 998                         mk_stmt_let(self, p_ptr_ident, call)
 999                     };
1000
1001                     // pop_unsafe!(EXPR));
1002                     let pop_unsafe_expr = {
1003                         let value_expr = self.signal_block_expr(hir_vec![],
1004                                                                 value_expr,
1005                                                                 e.span,
1006                                                                 hir::PopUnstableBlock,
1007                                                                 ThinVec::new());
1008                         self.signal_block_expr(hir_vec![],
1009                                                value_expr,
1010                                                e.span,
1011                                                hir::PopUnsafeBlock(hir::CompilerGenerated),
1012                                                ThinVec::new())
1013                     };
1014
1015                     // push_unsafe!({
1016                     //     std::intrinsics::move_val_init(raw_place, pop_unsafe!( EXPR ));
1017                     //     InPlace::finalize(place)
1018                     // })
1019                     let expr = {
1020                         let ptr = self.expr_ident(e.span, p_ptr_ident, p_ptr_binding);
1021                         let call_move_val_init =
1022                             hir::StmtSemi(
1023                                 make_call(self, &move_val_init, hir_vec![ptr, pop_unsafe_expr]),
1024                                 self.next_id());
1025                         let call_move_val_init = respan(e.span, call_move_val_init);
1026
1027                         let place = self.expr_ident(e.span, place_ident, place_binding);
1028                         let call = make_call(self, &inplace_finalize, hir_vec![place]);
1029                         self.signal_block_expr(hir_vec![call_move_val_init],
1030                                                call,
1031                                                e.span,
1032                                                hir::PushUnsafeBlock(hir::CompilerGenerated),
1033                                                ThinVec::new())
1034                     };
1035
1036                     return self.signal_block_expr(hir_vec![s1, s2, s3],
1037                                                   expr,
1038                                                   e.span,
1039                                                   hir::PushUnstableBlock,
1040                                                   e.attrs.clone());
1041                 }
1042
1043                 ExprKind::Vec(ref exprs) => {
1044                     hir::ExprVec(exprs.iter().map(|x| self.lower_expr(x)).collect())
1045                 }
1046                 ExprKind::Repeat(ref expr, ref count) => {
1047                     let expr = self.lower_expr(expr);
1048                     let count = self.lower_expr(count);
1049                     hir::ExprRepeat(expr, count)
1050                 }
1051                 ExprKind::Tup(ref elts) => {
1052                     hir::ExprTup(elts.iter().map(|x| self.lower_expr(x)).collect())
1053                 }
1054                 ExprKind::Call(ref f, ref args) => {
1055                     let f = self.lower_expr(f);
1056                     hir::ExprCall(f, args.iter().map(|x| self.lower_expr(x)).collect())
1057                 }
1058                 ExprKind::MethodCall(i, ref tps, ref args) => {
1059                     let tps = tps.iter().map(|x| self.lower_ty(x)).collect();
1060                     let args = args.iter().map(|x| self.lower_expr(x)).collect();
1061                     hir::ExprMethodCall(respan(i.span, i.node.name), tps, args)
1062                 }
1063                 ExprKind::Binary(binop, ref lhs, ref rhs) => {
1064                     let binop = self.lower_binop(binop);
1065                     let lhs = self.lower_expr(lhs);
1066                     let rhs = self.lower_expr(rhs);
1067                     hir::ExprBinary(binop, lhs, rhs)
1068                 }
1069                 ExprKind::Unary(op, ref ohs) => {
1070                     let op = self.lower_unop(op);
1071                     let ohs = self.lower_expr(ohs);
1072                     hir::ExprUnary(op, ohs)
1073                 }
1074                 ExprKind::Lit(ref l) => hir::ExprLit(P((**l).clone())),
1075                 ExprKind::Cast(ref expr, ref ty) => {
1076                     let expr = self.lower_expr(expr);
1077                     hir::ExprCast(expr, self.lower_ty(ty))
1078                 }
1079                 ExprKind::Type(ref expr, ref ty) => {
1080                     let expr = self.lower_expr(expr);
1081                     hir::ExprType(expr, self.lower_ty(ty))
1082                 }
1083                 ExprKind::AddrOf(m, ref ohs) => {
1084                     let m = self.lower_mutability(m);
1085                     let ohs = self.lower_expr(ohs);
1086                     hir::ExprAddrOf(m, ohs)
1087                 }
1088                 // More complicated than you might expect because the else branch
1089                 // might be `if let`.
1090                 ExprKind::If(ref cond, ref blk, ref else_opt) => {
1091                     let else_opt = else_opt.as_ref().map(|els| {
1092                         match els.node {
1093                             ExprKind::IfLet(..) => {
1094                                 // wrap the if-let expr in a block
1095                                 let span = els.span;
1096                                 let els = self.lower_expr(els);
1097                                 let id = self.next_id();
1098                                 let blk = P(hir::Block {
1099                                     stmts: hir_vec![],
1100                                     expr: Some(els),
1101                                     id: id,
1102                                     rules: hir::DefaultBlock,
1103                                     span: span,
1104                                 });
1105                                 self.expr_block(blk, ThinVec::new())
1106                             }
1107                             _ => self.lower_expr(els),
1108                         }
1109                     });
1110
1111                     hir::ExprIf(self.lower_expr(cond), self.lower_block(blk), else_opt)
1112                 }
1113                 ExprKind::While(ref cond, ref body, opt_ident) => {
1114                     hir::ExprWhile(self.lower_expr(cond), self.lower_block(body),
1115                                    self.lower_opt_sp_ident(opt_ident))
1116                 }
1117                 ExprKind::Loop(ref body, opt_ident) => {
1118                     hir::ExprLoop(self.lower_block(body), self.lower_opt_sp_ident(opt_ident))
1119                 }
1120                 ExprKind::Match(ref expr, ref arms) => {
1121                     hir::ExprMatch(self.lower_expr(expr),
1122                                    arms.iter().map(|x| self.lower_arm(x)).collect(),
1123                                    hir::MatchSource::Normal)
1124                 }
1125                 ExprKind::Closure(capture_clause, ref decl, ref body, fn_decl_span) => {
1126                     self.with_parent_def(e.id, |this| {
1127                         hir::ExprClosure(this.lower_capture_clause(capture_clause),
1128                                          this.lower_fn_decl(decl),
1129                                          this.lower_block(body),
1130                                          fn_decl_span)
1131                     })
1132                 }
1133                 ExprKind::Block(ref blk) => hir::ExprBlock(self.lower_block(blk)),
1134                 ExprKind::Assign(ref el, ref er) => {
1135                     hir::ExprAssign(self.lower_expr(el), self.lower_expr(er))
1136                 }
1137                 ExprKind::AssignOp(op, ref el, ref er) => {
1138                     hir::ExprAssignOp(self.lower_binop(op),
1139                                       self.lower_expr(el),
1140                                       self.lower_expr(er))
1141                 }
1142                 ExprKind::Field(ref el, ident) => {
1143                     hir::ExprField(self.lower_expr(el), respan(ident.span, ident.node.name))
1144                 }
1145                 ExprKind::TupField(ref el, ident) => {
1146                     hir::ExprTupField(self.lower_expr(el), ident)
1147                 }
1148                 ExprKind::Index(ref el, ref er) => {
1149                     hir::ExprIndex(self.lower_expr(el), self.lower_expr(er))
1150                 }
1151                 ExprKind::Range(ref e1, ref e2, lims) => {
1152                     fn make_struct(this: &mut LoweringContext,
1153                                    ast_expr: &Expr,
1154                                    path: &[&str],
1155                                    fields: &[(&str, &P<Expr>)]) -> P<hir::Expr> {
1156                         let strs = this.std_path(&iter::once(&"ops")
1157                                                         .chain(path)
1158                                                         .map(|s| *s)
1159                                                         .collect::<Vec<_>>());
1160
1161                         let structpath = this.path_global(ast_expr.span, strs);
1162
1163                         let hir_expr = if fields.len() == 0 {
1164                             this.expr_path(structpath, ast_expr.attrs.clone())
1165                         } else {
1166                             let fields = fields.into_iter().map(|&(s, e)| {
1167                                 let expr = this.lower_expr(&e);
1168                                 let signal_block = this.signal_block_expr(hir_vec![],
1169                                                                           expr,
1170                                                                           e.span,
1171                                                                           hir::PopUnstableBlock,
1172                                                                           ThinVec::new());
1173                                 this.field(token::intern(s), signal_block, ast_expr.span)
1174                             }).collect();
1175                             let attrs = ast_expr.attrs.clone();
1176
1177                             this.expr_struct(ast_expr.span, structpath, fields, None, attrs)
1178                         };
1179
1180                         this.signal_block_expr(hir_vec![],
1181                                                hir_expr,
1182                                                ast_expr.span,
1183                                                hir::PushUnstableBlock,
1184                                                ThinVec::new())
1185                     }
1186
1187                     use syntax::ast::RangeLimits::*;
1188
1189                     return match (e1, e2, lims) {
1190                         (&None,         &None,         HalfOpen) =>
1191                             make_struct(self, e, &["RangeFull"], &[]),
1192
1193                         (&Some(ref e1), &None,         HalfOpen) =>
1194                             make_struct(self, e, &["RangeFrom"],
1195                                                  &[("start", e1)]),
1196
1197                         (&None,         &Some(ref e2), HalfOpen) =>
1198                             make_struct(self, e, &["RangeTo"],
1199                                                  &[("end", e2)]),
1200
1201                         (&Some(ref e1), &Some(ref e2), HalfOpen) =>
1202                             make_struct(self, e, &["Range"],
1203                                                  &[("start", e1), ("end", e2)]),
1204
1205                         (&None,         &Some(ref e2), Closed)   =>
1206                             make_struct(self, e, &["RangeToInclusive"],
1207                                                  &[("end", e2)]),
1208
1209                         (&Some(ref e1), &Some(ref e2), Closed)   =>
1210                             make_struct(self, e, &["RangeInclusive", "NonEmpty"],
1211                                                  &[("start", e1), ("end", e2)]),
1212
1213                         _ => panic!(self.diagnostic()
1214                                         .span_fatal(e.span, "inclusive range with no end")),
1215                     };
1216                 }
1217                 ExprKind::Path(ref qself, ref path) => {
1218                     let hir_qself = qself.as_ref().map(|&QSelf { ref ty, position }| {
1219                         hir::QSelf {
1220                             ty: self.lower_ty(ty),
1221                             position: position,
1222                         }
1223                     });
1224                     hir::ExprPath(hir_qself, self.lower_path(path))
1225                 }
1226                 ExprKind::Break(opt_ident) => hir::ExprBreak(self.lower_opt_sp_ident(opt_ident)),
1227                 ExprKind::Continue(opt_ident) => hir::ExprAgain(self.lower_opt_sp_ident(opt_ident)),
1228                 ExprKind::Ret(ref e) => hir::ExprRet(e.as_ref().map(|x| self.lower_expr(x))),
1229                 ExprKind::InlineAsm(InlineAsm {
1230                         ref inputs,
1231                         ref outputs,
1232                         ref asm,
1233                         asm_str_style,
1234                         ref clobbers,
1235                         volatile,
1236                         alignstack,
1237                         dialect,
1238                         expn_id,
1239                     }) => hir::ExprInlineAsm(hir::InlineAsm {
1240                     inputs: inputs.iter().map(|&(ref c, _)| c.clone()).collect(),
1241                     outputs: outputs.iter()
1242                                     .map(|out| {
1243                                         hir::InlineAsmOutput {
1244                                             constraint: out.constraint.clone(),
1245                                             is_rw: out.is_rw,
1246                                             is_indirect: out.is_indirect,
1247                                         }
1248                                     })
1249                                     .collect(),
1250                     asm: asm.clone(),
1251                     asm_str_style: asm_str_style,
1252                     clobbers: clobbers.clone().into(),
1253                     volatile: volatile,
1254                     alignstack: alignstack,
1255                     dialect: dialect,
1256                     expn_id: expn_id,
1257                 }, outputs.iter().map(|out| self.lower_expr(&out.expr)).collect(),
1258                    inputs.iter().map(|&(_, ref input)| self.lower_expr(input)).collect()),
1259                 ExprKind::Struct(ref path, ref fields, ref maybe_expr) => {
1260                     hir::ExprStruct(self.lower_path(path),
1261                                     fields.iter().map(|x| self.lower_field(x)).collect(),
1262                                     maybe_expr.as_ref().map(|x| self.lower_expr(x)))
1263                 }
1264                 ExprKind::Paren(ref ex) => {
1265                     return self.lower_expr(ex).map(|mut ex| {
1266                         // include parens in span, but only if it is a super-span.
1267                         if e.span.contains(ex.span) {
1268                             ex.span = e.span;
1269                         }
1270                         // merge attributes into the inner expression.
1271                         let mut attrs = e.attrs.clone();
1272                         attrs.extend::<Vec<_>>(ex.attrs.into());
1273                         ex.attrs = attrs;
1274                         ex
1275                     });
1276                 }
1277
1278                 // Desugar ExprIfLet
1279                 // From: `if let <pat> = <sub_expr> <body> [<else_opt>]`
1280                 ExprKind::IfLet(ref pat, ref sub_expr, ref body, ref else_opt) => {
1281                     // to:
1282                     //
1283                     //   match <sub_expr> {
1284                     //     <pat> => <body>,
1285                     //     [_ if <else_opt_if_cond> => <else_opt_if_body>,]
1286                     //     _ => [<else_opt> | ()]
1287                     //   }
1288
1289                     // `<pat> => <body>`
1290                     let pat_arm = {
1291                         let body = self.lower_block(body);
1292                         let body_expr = self.expr_block(body, ThinVec::new());
1293                         let pat = self.lower_pat(pat);
1294                         self.arm(hir_vec![pat], body_expr)
1295                     };
1296
1297                     // `[_ if <else_opt_if_cond> => <else_opt_if_body>,]`
1298                     let mut else_opt = else_opt.as_ref().map(|e| self.lower_expr(e));
1299                     let else_if_arms = {
1300                         let mut arms = vec![];
1301                         loop {
1302                             let else_opt_continue = else_opt.and_then(|els| {
1303                                 els.and_then(|els| {
1304                                     match els.node {
1305                                         // else if
1306                                         hir::ExprIf(cond, then, else_opt) => {
1307                                             let pat_under = self.pat_wild(e.span);
1308                                             arms.push(hir::Arm {
1309                                                 attrs: hir_vec![],
1310                                                 pats: hir_vec![pat_under],
1311                                                 guard: Some(cond),
1312                                                 body: self.expr_block(then, ThinVec::new()),
1313                                             });
1314                                             else_opt.map(|else_opt| (else_opt, true))
1315                                         }
1316                                         _ => Some((P(els), false)),
1317                                     }
1318                                 })
1319                             });
1320                             match else_opt_continue {
1321                                 Some((e, true)) => {
1322                                     else_opt = Some(e);
1323                                 }
1324                                 Some((e, false)) => {
1325                                     else_opt = Some(e);
1326                                     break;
1327                                 }
1328                                 None => {
1329                                     else_opt = None;
1330                                     break;
1331                                 }
1332                             }
1333                         }
1334                         arms
1335                     };
1336
1337                     let contains_else_clause = else_opt.is_some();
1338
1339                     // `_ => [<else_opt> | ()]`
1340                     let else_arm = {
1341                         let pat_under = self.pat_wild(e.span);
1342                         let else_expr =
1343                             else_opt.unwrap_or_else(|| self.expr_tuple(e.span, hir_vec![]));
1344                         self.arm(hir_vec![pat_under], else_expr)
1345                     };
1346
1347                     let mut arms = Vec::with_capacity(else_if_arms.len() + 2);
1348                     arms.push(pat_arm);
1349                     arms.extend(else_if_arms);
1350                     arms.push(else_arm);
1351
1352                     let sub_expr = self.lower_expr(sub_expr);
1353                     // add attributes to the outer returned expr node
1354                     return self.expr(e.span,
1355                                      hir::ExprMatch(sub_expr,
1356                                                     arms.into(),
1357                                                     hir::MatchSource::IfLetDesugar {
1358                                                         contains_else_clause: contains_else_clause,
1359                                                     }),
1360                                      e.attrs.clone());
1361                 }
1362
1363                 // Desugar ExprWhileLet
1364                 // From: `[opt_ident]: while let <pat> = <sub_expr> <body>`
1365                 ExprKind::WhileLet(ref pat, ref sub_expr, ref body, opt_ident) => {
1366                     // to:
1367                     //
1368                     //   [opt_ident]: loop {
1369                     //     match <sub_expr> {
1370                     //       <pat> => <body>,
1371                     //       _ => break
1372                     //     }
1373                     //   }
1374
1375                     // `<pat> => <body>`
1376                     let pat_arm = {
1377                         let body = self.lower_block(body);
1378                         let body_expr = self.expr_block(body, ThinVec::new());
1379                         let pat = self.lower_pat(pat);
1380                         self.arm(hir_vec![pat], body_expr)
1381                     };
1382
1383                     // `_ => break`
1384                     let break_arm = {
1385                         let pat_under = self.pat_wild(e.span);
1386                         let break_expr = self.expr_break(e.span, ThinVec::new());
1387                         self.arm(hir_vec![pat_under], break_expr)
1388                     };
1389
1390                     // `match <sub_expr> { ... }`
1391                     let arms = hir_vec![pat_arm, break_arm];
1392                     let sub_expr = self.lower_expr(sub_expr);
1393                     let match_expr = self.expr(e.span,
1394                                                hir::ExprMatch(sub_expr,
1395                                                               arms,
1396                                                               hir::MatchSource::WhileLetDesugar),
1397                                                ThinVec::new());
1398
1399                     // `[opt_ident]: loop { ... }`
1400                     let loop_block = self.block_expr(match_expr);
1401                     let loop_expr = hir::ExprLoop(loop_block, self.lower_opt_sp_ident(opt_ident));
1402                     // add attributes to the outer returned expr node
1403                     let attrs = e.attrs.clone();
1404                     return P(hir::Expr { id: e.id, node: loop_expr, span: e.span, attrs: attrs });
1405                 }
1406
1407                 // Desugar ExprForLoop
1408                 // From: `[opt_ident]: for <pat> in <head> <body>`
1409                 ExprKind::ForLoop(ref pat, ref head, ref body, opt_ident) => {
1410                     // to:
1411                     //
1412                     //   {
1413                     //     let result = match ::std::iter::IntoIterator::into_iter(<head>) {
1414                     //       mut iter => {
1415                     //         [opt_ident]: loop {
1416                     //           match ::std::iter::Iterator::next(&mut iter) {
1417                     //             ::std::option::Option::Some(<pat>) => <body>,
1418                     //             ::std::option::Option::None => break
1419                     //           }
1420                     //         }
1421                     //       }
1422                     //     };
1423                     //     result
1424                     //   }
1425
1426                     // expand <head>
1427                     let head = self.lower_expr(head);
1428
1429                     let iter = self.str_to_ident("iter");
1430
1431                     // `::std::option::Option::Some(<pat>) => <body>`
1432                     let pat_arm = {
1433                         let body_block = self.lower_block(body);
1434                         let body_span = body_block.span;
1435                         let body_expr = P(hir::Expr {
1436                             id: self.next_id(),
1437                             node: hir::ExprBlock(body_block),
1438                             span: body_span,
1439                             attrs: ThinVec::new(),
1440                         });
1441                         let pat = self.lower_pat(pat);
1442                         let some_pat = self.pat_some(e.span, pat);
1443
1444                         self.arm(hir_vec![some_pat], body_expr)
1445                     };
1446
1447                     // `::std::option::Option::None => break`
1448                     let break_arm = {
1449                         let break_expr = self.expr_break(e.span, ThinVec::new());
1450                         let pat = self.pat_none(e.span);
1451                         self.arm(hir_vec![pat], break_expr)
1452                     };
1453
1454                     // `mut iter`
1455                     let iter_pat = self.pat_ident_binding_mode(e.span, iter,
1456                                                                hir::BindByValue(hir::MutMutable));
1457
1458                     // `match ::std::iter::Iterator::next(&mut iter) { ... }`
1459                     let match_expr = {
1460                         let next_path = {
1461                             let strs = self.std_path(&["iter", "Iterator", "next"]);
1462
1463                             self.path_global(e.span, strs)
1464                         };
1465                         let iter = self.expr_ident(e.span, iter, iter_pat.id);
1466                         let ref_mut_iter = self.expr_mut_addr_of(e.span, iter);
1467                         let next_path = self.expr_path(next_path, ThinVec::new());
1468                         let next_expr = self.expr_call(e.span, next_path, hir_vec![ref_mut_iter]);
1469                         let arms = hir_vec![pat_arm, break_arm];
1470
1471                         self.expr(e.span,
1472                                   hir::ExprMatch(next_expr, arms, hir::MatchSource::ForLoopDesugar),
1473                                   ThinVec::new())
1474                     };
1475
1476                     // `[opt_ident]: loop { ... }`
1477                     let loop_block = self.block_expr(match_expr);
1478                     let loop_expr = hir::ExprLoop(loop_block, self.lower_opt_sp_ident(opt_ident));
1479                     let loop_expr = P(hir::Expr {
1480                         id: e.id,
1481                         node: loop_expr,
1482                         span: e.span,
1483                         attrs: ThinVec::new(),
1484                     });
1485
1486                     // `mut iter => { ... }`
1487                     let iter_arm = self.arm(hir_vec![iter_pat], loop_expr);
1488
1489                     // `match ::std::iter::IntoIterator::into_iter(<head>) { ... }`
1490                     let into_iter_expr = {
1491                         let into_iter_path = {
1492                             let strs = self.std_path(&["iter", "IntoIterator", "into_iter"]);
1493
1494                             self.path_global(e.span, strs)
1495                         };
1496
1497                         let into_iter = self.expr_path(into_iter_path, ThinVec::new());
1498                         self.expr_call(e.span, into_iter, hir_vec![head])
1499                     };
1500
1501                     let match_expr = self.expr_match(e.span,
1502                                                      into_iter_expr,
1503                                                      hir_vec![iter_arm],
1504                                                      hir::MatchSource::ForLoopDesugar);
1505
1506                     // `{ let _result = ...; _result }`
1507                     // underscore prevents an unused_variables lint if the head diverges
1508                     let result_ident = self.str_to_ident("_result");
1509                     let (let_stmt, let_stmt_binding) =
1510                         self.stmt_let(e.span, false, result_ident, match_expr);
1511
1512                     let result = self.expr_ident(e.span, result_ident, let_stmt_binding);
1513                     let block = self.block_all(e.span, hir_vec![let_stmt], Some(result));
1514                     // add the attributes to the outer returned expr node
1515                     return self.expr_block(block, e.attrs.clone());
1516                 }
1517
1518                 // Desugar ExprKind::Try
1519                 // From: `<expr>?`
1520                 ExprKind::Try(ref sub_expr) => {
1521                     // to:
1522                     //
1523                     // {
1524                     //     match <expr> {
1525                     //         Ok(val) => val,
1526                     //         Err(err) => {
1527                     //             return Err(From::from(err))
1528                     //         }
1529                     //     }
1530                     // }
1531
1532                     // expand <expr>
1533                     let sub_expr = self.lower_expr(sub_expr);
1534
1535                     // Ok(val) => val
1536                     let ok_arm = {
1537                         let val_ident = self.str_to_ident("val");
1538                         let val_pat = self.pat_ident(e.span, val_ident);
1539                         let val_expr = self.expr_ident(e.span, val_ident, val_pat.id);
1540                         let ok_pat = self.pat_ok(e.span, val_pat);
1541
1542                         self.arm(hir_vec![ok_pat], val_expr)
1543                     };
1544
1545                     // Err(err) => return Err(From::from(err))
1546                     let err_arm = {
1547                         let err_ident = self.str_to_ident("err");
1548                         let err_local = self.pat_ident(e.span, err_ident);
1549                         let from_expr = {
1550                             let path = self.std_path(&["convert", "From", "from"]);
1551                             let path = self.path_global(e.span, path);
1552                             let from = self.expr_path(path, ThinVec::new());
1553                             let err_expr = self.expr_ident(e.span, err_ident, err_local.id);
1554
1555                             self.expr_call(e.span, from, hir_vec![err_expr])
1556                         };
1557                         let err_expr = {
1558                             let path = self.std_path(&["result", "Result", "Err"]);
1559                             let path = self.path_global(e.span, path);
1560                             let err_ctor = self.expr_path(path, ThinVec::new());
1561                             self.expr_call(e.span, err_ctor, hir_vec![from_expr])
1562                         };
1563                         let err_pat = self.pat_err(e.span, err_local);
1564                         let ret_expr = self.expr(e.span,
1565                                                  hir::Expr_::ExprRet(Some(err_expr)),
1566                                                  ThinVec::new());
1567                         self.arm(hir_vec![err_pat], ret_expr)
1568                     };
1569
1570                     return self.expr_match(e.span, sub_expr, hir_vec![err_arm, ok_arm],
1571                                            hir::MatchSource::TryDesugar);
1572                 }
1573
1574                 ExprKind::Mac(_) => panic!("Shouldn't exist here"),
1575             },
1576             span: e.span,
1577             attrs: e.attrs.clone(),
1578         })
1579     }
1580
1581     fn lower_stmt(&mut self, s: &Stmt) -> hir::Stmt {
1582         match s.node {
1583             StmtKind::Local(ref l) => Spanned {
1584                 node: hir::StmtDecl(P(Spanned {
1585                     node: hir::DeclLocal(self.lower_local(l)),
1586                     span: s.span,
1587                 }), s.id),
1588                 span: s.span,
1589             },
1590             StmtKind::Item(ref it) => Spanned {
1591                 node: hir::StmtDecl(P(Spanned {
1592                     node: hir::DeclItem(self.lower_item_id(it)),
1593                     span: s.span,
1594                 }), s.id),
1595                 span: s.span,
1596             },
1597             StmtKind::Expr(ref e) => {
1598                 Spanned {
1599                     node: hir::StmtExpr(self.lower_expr(e), s.id),
1600                     span: s.span,
1601                 }
1602             }
1603             StmtKind::Semi(ref e) => {
1604                 Spanned {
1605                     node: hir::StmtSemi(self.lower_expr(e), s.id),
1606                     span: s.span,
1607                 }
1608             }
1609             StmtKind::Mac(..) => panic!("Shouldn't exist here"),
1610         }
1611     }
1612
1613     fn lower_capture_clause(&mut self, c: CaptureBy) -> hir::CaptureClause {
1614         match c {
1615             CaptureBy::Value => hir::CaptureByValue,
1616             CaptureBy::Ref => hir::CaptureByRef,
1617         }
1618     }
1619
1620     fn lower_visibility(&mut self, v: &Visibility) -> hir::Visibility {
1621         match *v {
1622             Visibility::Public => hir::Public,
1623             Visibility::Crate(_) => hir::Visibility::Crate,
1624             Visibility::Restricted { ref path, id } =>
1625                 hir::Visibility::Restricted { path: P(self.lower_path(path)), id: id },
1626             Visibility::Inherited => hir::Inherited,
1627         }
1628     }
1629
1630     fn lower_defaultness(&mut self, d: Defaultness) -> hir::Defaultness {
1631         match d {
1632             Defaultness::Default => hir::Defaultness::Default,
1633             Defaultness::Final => hir::Defaultness::Final,
1634         }
1635     }
1636
1637     fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode {
1638         match *b {
1639             BlockCheckMode::Default => hir::DefaultBlock,
1640             BlockCheckMode::Unsafe(u) => hir::UnsafeBlock(self.lower_unsafe_source(u)),
1641         }
1642     }
1643
1644     fn lower_binding_mode(&mut self, b: &BindingMode) -> hir::BindingMode {
1645         match *b {
1646             BindingMode::ByRef(m) => hir::BindByRef(self.lower_mutability(m)),
1647             BindingMode::ByValue(m) => hir::BindByValue(self.lower_mutability(m)),
1648         }
1649     }
1650
1651     fn lower_unsafe_source(&mut self, u: UnsafeSource) -> hir::UnsafeSource {
1652         match u {
1653             CompilerGenerated => hir::CompilerGenerated,
1654             UserProvided => hir::UserProvided,
1655         }
1656     }
1657
1658     fn lower_impl_polarity(&mut self, i: ImplPolarity) -> hir::ImplPolarity {
1659         match i {
1660             ImplPolarity::Positive => hir::ImplPolarity::Positive,
1661             ImplPolarity::Negative => hir::ImplPolarity::Negative,
1662         }
1663     }
1664
1665     fn lower_trait_bound_modifier(&mut self, f: TraitBoundModifier) -> hir::TraitBoundModifier {
1666         match f {
1667             TraitBoundModifier::None => hir::TraitBoundModifier::None,
1668             TraitBoundModifier::Maybe => hir::TraitBoundModifier::Maybe,
1669         }
1670     }
1671
1672     // Helper methods for building HIR.
1673
1674     fn arm(&mut self, pats: hir::HirVec<P<hir::Pat>>, expr: P<hir::Expr>) -> hir::Arm {
1675         hir::Arm {
1676             attrs: hir_vec![],
1677             pats: pats,
1678             guard: None,
1679             body: expr,
1680         }
1681     }
1682
1683     fn field(&mut self, name: Name, expr: P<hir::Expr>, span: Span) -> hir::Field {
1684         hir::Field {
1685             name: Spanned {
1686                 node: name,
1687                 span: span,
1688             },
1689             span: span,
1690             expr: expr,
1691         }
1692     }
1693
1694     fn expr_break(&mut self, span: Span, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
1695         self.expr(span, hir::ExprBreak(None), attrs)
1696     }
1697
1698     fn expr_call(&mut self, span: Span, e: P<hir::Expr>, args: hir::HirVec<P<hir::Expr>>)
1699                  -> P<hir::Expr> {
1700         self.expr(span, hir::ExprCall(e, args), ThinVec::new())
1701     }
1702
1703     fn expr_ident(&mut self, span: Span, id: Name, binding: NodeId) -> P<hir::Expr> {
1704         let expr_path = hir::ExprPath(None, self.path_ident(span, id));
1705         let expr = self.expr(span, expr_path, ThinVec::new());
1706
1707         let def = self.resolver.definitions().map(|defs| {
1708             Def::Local(defs.local_def_id(binding), binding)
1709         }).unwrap_or(Def::Err);
1710         self.resolver.record_resolution(expr.id, def);
1711
1712         expr
1713     }
1714
1715     fn expr_mut_addr_of(&mut self, span: Span, e: P<hir::Expr>) -> P<hir::Expr> {
1716         self.expr(span, hir::ExprAddrOf(hir::MutMutable, e), ThinVec::new())
1717     }
1718
1719     fn expr_path(&mut self, path: hir::Path, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
1720         let def = self.resolver.resolve_generated_global_path(&path, true);
1721         let expr = self.expr(path.span, hir::ExprPath(None, path), attrs);
1722         self.resolver.record_resolution(expr.id, def);
1723         expr
1724     }
1725
1726     fn expr_match(&mut self,
1727                   span: Span,
1728                   arg: P<hir::Expr>,
1729                   arms: hir::HirVec<hir::Arm>,
1730                   source: hir::MatchSource)
1731                   -> P<hir::Expr> {
1732         self.expr(span, hir::ExprMatch(arg, arms, source), ThinVec::new())
1733     }
1734
1735     fn expr_block(&mut self, b: P<hir::Block>, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
1736         self.expr(b.span, hir::ExprBlock(b), attrs)
1737     }
1738
1739     fn expr_tuple(&mut self, sp: Span, exprs: hir::HirVec<P<hir::Expr>>) -> P<hir::Expr> {
1740         self.expr(sp, hir::ExprTup(exprs), ThinVec::new())
1741     }
1742
1743     fn expr_struct(&mut self,
1744                    sp: Span,
1745                    path: hir::Path,
1746                    fields: hir::HirVec<hir::Field>,
1747                    e: Option<P<hir::Expr>>,
1748                    attrs: ThinVec<Attribute>) -> P<hir::Expr> {
1749         let def = self.resolver.resolve_generated_global_path(&path, false);
1750         let expr = self.expr(sp, hir::ExprStruct(path, fields, e), attrs);
1751         self.resolver.record_resolution(expr.id, def);
1752         expr
1753     }
1754
1755     fn expr(&mut self, span: Span, node: hir::Expr_, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
1756         P(hir::Expr {
1757             id: self.next_id(),
1758             node: node,
1759             span: span,
1760             attrs: attrs,
1761         })
1762     }
1763
1764     fn stmt_let(&mut self, sp: Span, mutbl: bool, ident: Name, ex: P<hir::Expr>)
1765                 -> (hir::Stmt, NodeId) {
1766         let pat = if mutbl {
1767             self.pat_ident_binding_mode(sp, ident, hir::BindByValue(hir::MutMutable))
1768         } else {
1769             self.pat_ident(sp, ident)
1770         };
1771         let pat_id = pat.id;
1772         let local = P(hir::Local {
1773             pat: pat,
1774             ty: None,
1775             init: Some(ex),
1776             id: self.next_id(),
1777             span: sp,
1778             attrs: ThinVec::new(),
1779         });
1780         let decl = respan(sp, hir::DeclLocal(local));
1781         (respan(sp, hir::StmtDecl(P(decl), self.next_id())), pat_id)
1782     }
1783
1784     fn block_expr(&mut self, expr: P<hir::Expr>) -> P<hir::Block> {
1785         self.block_all(expr.span, hir::HirVec::new(), Some(expr))
1786     }
1787
1788     fn block_all(&mut self, span: Span, stmts: hir::HirVec<hir::Stmt>, expr: Option<P<hir::Expr>>)
1789                  -> P<hir::Block> {
1790         P(hir::Block {
1791             stmts: stmts,
1792             expr: expr,
1793             id: self.next_id(),
1794             rules: hir::DefaultBlock,
1795             span: span,
1796         })
1797     }
1798
1799     fn pat_ok(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
1800         let ok = self.std_path(&["result", "Result", "Ok"]);
1801         let path = self.path_global(span, ok);
1802         self.pat_enum(span, path, hir_vec![pat])
1803     }
1804
1805     fn pat_err(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
1806         let err = self.std_path(&["result", "Result", "Err"]);
1807         let path = self.path_global(span, err);
1808         self.pat_enum(span, path, hir_vec![pat])
1809     }
1810
1811     fn pat_some(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
1812         let some = self.std_path(&["option", "Option", "Some"]);
1813         let path = self.path_global(span, some);
1814         self.pat_enum(span, path, hir_vec![pat])
1815     }
1816
1817     fn pat_none(&mut self, span: Span) -> P<hir::Pat> {
1818         let none = self.std_path(&["option", "Option", "None"]);
1819         let path = self.path_global(span, none);
1820         self.pat_enum(span, path, hir_vec![])
1821     }
1822
1823     fn pat_enum(&mut self, span: Span, path: hir::Path, subpats: hir::HirVec<P<hir::Pat>>)
1824                 -> P<hir::Pat> {
1825         let def = self.resolver.resolve_generated_global_path(&path, true);
1826         let pt = if subpats.is_empty() {
1827             hir::PatKind::Path(None, path)
1828         } else {
1829             hir::PatKind::TupleStruct(path, subpats, None)
1830         };
1831         let pat = self.pat(span, pt);
1832         self.resolver.record_resolution(pat.id, def);
1833         pat
1834     }
1835
1836     fn pat_ident(&mut self, span: Span, name: Name) -> P<hir::Pat> {
1837         self.pat_ident_binding_mode(span, name, hir::BindByValue(hir::MutImmutable))
1838     }
1839
1840     fn pat_ident_binding_mode(&mut self, span: Span, name: Name, bm: hir::BindingMode)
1841                               -> P<hir::Pat> {
1842         let pat_ident = hir::PatKind::Binding(bm,
1843                                             Spanned {
1844                                                 span: span,
1845                                                 node: name,
1846                                             },
1847                                             None);
1848
1849         let pat = self.pat(span, pat_ident);
1850
1851         let parent_def = self.parent_def;
1852         let def = self.resolver.definitions().map(|defs| {
1853             let def_path_data = DefPathData::Binding(name.as_str());
1854             let def_index = defs.create_def_with_parent(parent_def, pat.id, def_path_data);
1855             Def::Local(DefId::local(def_index), pat.id)
1856         }).unwrap_or(Def::Err);
1857         self.resolver.record_resolution(pat.id, def);
1858
1859         pat
1860     }
1861
1862     fn pat_wild(&mut self, span: Span) -> P<hir::Pat> {
1863         self.pat(span, hir::PatKind::Wild)
1864     }
1865
1866     fn pat(&mut self, span: Span, pat: hir::PatKind) -> P<hir::Pat> {
1867         P(hir::Pat {
1868             id: self.next_id(),
1869             node: pat,
1870             span: span,
1871         })
1872     }
1873
1874     fn path_ident(&mut self, span: Span, id: Name) -> hir::Path {
1875         self.path(span, vec![id])
1876     }
1877
1878     fn path(&mut self, span: Span, strs: Vec<Name>) -> hir::Path {
1879         self.path_all(span, false, strs, hir::HirVec::new(), hir::HirVec::new(), hir::HirVec::new())
1880     }
1881
1882     fn path_global(&mut self, span: Span, strs: Vec<Name>) -> hir::Path {
1883         self.path_all(span, true, strs, hir::HirVec::new(), hir::HirVec::new(), hir::HirVec::new())
1884     }
1885
1886     fn path_all(&mut self,
1887                 sp: Span,
1888                 global: bool,
1889                 mut names: Vec<Name>,
1890                 lifetimes: hir::HirVec<hir::Lifetime>,
1891                 types: hir::HirVec<P<hir::Ty>>,
1892                 bindings: hir::HirVec<hir::TypeBinding>)
1893                 -> hir::Path {
1894         let last_identifier = names.pop().unwrap();
1895         let mut segments: Vec<hir::PathSegment> = names.into_iter().map(|name| {
1896             hir::PathSegment {
1897                 name: name,
1898                 parameters: hir::PathParameters::none(),
1899            }
1900         }).collect();
1901
1902         segments.push(hir::PathSegment {
1903             name: last_identifier,
1904             parameters: hir::AngleBracketedParameters(hir::AngleBracketedParameterData {
1905                 lifetimes: lifetimes,
1906                 types: types,
1907                 bindings: bindings,
1908             }),
1909         });
1910         hir::Path {
1911             span: sp,
1912             global: global,
1913             segments: segments.into(),
1914         }
1915     }
1916
1917     fn std_path(&mut self, components: &[&str]) -> Vec<Name> {
1918         let mut v = Vec::new();
1919         if let Some(s) = self.crate_root {
1920             v.push(token::intern(s));
1921         }
1922         v.extend(components.iter().map(|s| token::intern(s)));
1923         return v;
1924     }
1925
1926     // Given suffix ["b","c","d"], returns path `::std::b::c::d` when
1927     // `fld.cx.use_std`, and `::core::b::c::d` otherwise.
1928     fn core_path(&mut self, span: Span, components: &[&str]) -> hir::Path {
1929         let idents = self.std_path(components);
1930         self.path_global(span, idents)
1931     }
1932
1933     fn signal_block_expr(&mut self,
1934                          stmts: hir::HirVec<hir::Stmt>,
1935                          expr: P<hir::Expr>,
1936                          span: Span,
1937                          rule: hir::BlockCheckMode,
1938                          attrs: ThinVec<Attribute>)
1939                          -> P<hir::Expr> {
1940         let id = self.next_id();
1941         let block = P(hir::Block {
1942             rules: rule,
1943             span: span,
1944             id: id,
1945             stmts: stmts,
1946             expr: Some(expr),
1947         });
1948         self.expr_block(block, attrs)
1949     }
1950 }