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             span: g.span,
 464         }
 465     }
 466
 467     fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause {
 468         hir::WhereClause {
 469             id: wc.id,
 470             predicates: wc.predicates
 471                           .iter()
 472                           .map(|predicate| self.lower_where_predicate(predicate))
 473                           .collect(),
 474         }
 475     }
 476
 477     fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate {
 478         match *pred {
 479             WherePredicate::BoundPredicate(WhereBoundPredicate{ ref bound_lifetimes,
 480                                                                 ref bounded_ty,
 481                                                                 ref bounds,
 482                                                                 span}) => {
 483                 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
 484                     bound_lifetimes: self.lower_lifetime_defs(bound_lifetimes),
 485                     bounded_ty: self.lower_ty(bounded_ty),
 486                     bounds: bounds.iter().map(|x| self.lower_ty_param_bound(x)).collect(),
 487                     span: span,
 488                 })
 489             }
 490             WherePredicate::RegionPredicate(WhereRegionPredicate{ ref lifetime,
 491                                                                   ref bounds,
 492                                                                   span}) => {
 493                 hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
 494                     span: span,
 495                     lifetime: self.lower_lifetime(lifetime),
 496                     bounds: bounds.iter().map(|bound| self.lower_lifetime(bound)).collect(),
 497                 })
 498             }
 499             WherePredicate::EqPredicate(WhereEqPredicate{ id,
 500                                                           ref path,
 501                                                           ref ty,
 502                                                           span}) => {
 503                 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
 504                     id: id,
 505                     path: self.lower_path(path),
 506                     ty: self.lower_ty(ty),
 507                     span: span,
 508                 })
 509             }
 510         }
 511     }
 512
 513     fn lower_variant_data(&mut self, vdata: &VariantData) -> hir::VariantData {
 514         match *vdata {
 515             VariantData::Struct(ref fields, id) => {
 516                 hir::VariantData::Struct(fields.iter()
 517                                                .enumerate()
 518                                                .map(|f| self.lower_struct_field(f))
 519                                                .collect(),
 520                                          id)
 521             }
 522             VariantData::Tuple(ref fields, id) => {
 523                 hir::VariantData::Tuple(fields.iter()
 524                                               .enumerate()
 525                                               .map(|f| self.lower_struct_field(f))
 526                                               .collect(),
 527                                         id)
 528             }
 529             VariantData::Unit(id) => hir::VariantData::Unit(id),
 530         }
 531     }
 532
 533     fn lower_trait_ref(&mut self, p: &TraitRef) -> hir::TraitRef {
 534         hir::TraitRef {
 535             path: self.lower_path(&p.path),
 536             ref_id: p.ref_id,
 537         }
 538     }
 539
 540     fn lower_poly_trait_ref(&mut self, p: &PolyTraitRef) -> hir::PolyTraitRef {
 541         hir::PolyTraitRef {
 542             bound_lifetimes: self.lower_lifetime_defs(&p.bound_lifetimes),
 543             trait_ref: self.lower_trait_ref(&p.trait_ref),
 544             span: p.span,
 545         }
 546     }
 547
 548     fn lower_struct_field(&mut self, (index, f): (usize, &StructField)) -> hir::StructField {
 549         hir::StructField {
 550             span: f.span,
 551             id: f.id,
 552             name: f.ident.map(|ident| ident.name).unwrap_or(token::intern(&index.to_string())),
 553             vis: self.lower_visibility(&f.vis),
 554             ty: self.lower_ty(&f.ty),
 555             attrs: self.lower_attrs(&f.attrs),
 556         }
 557     }
 558
 559     fn lower_field(&mut self, f: &Field) -> hir::Field {
 560         hir::Field {
 561             name: respan(f.ident.span, f.ident.node.name),
 562             expr: self.lower_expr(&f.expr),
 563             span: f.span,
 564         }
 565     }
 566
 567     fn lower_mt(&mut self, mt: &MutTy) -> hir::MutTy {
 568         hir::MutTy {
 569             ty: self.lower_ty(&mt.ty),
 570             mutbl: self.lower_mutability(mt.mutbl),
 571         }
 572     }
 573
 574     fn lower_bounds(&mut self, bounds: &TyParamBounds) -> hir::TyParamBounds {
 575         bounds.iter().map(|bound| self.lower_ty_param_bound(bound)).collect()
 576     }
 577
 578     fn lower_block(&mut self, b: &Block) -> P<hir::Block> {
 579         let mut stmts = Vec::new();
 580         let mut expr = None;
 581
 582         if let Some((last, rest)) = b.stmts.split_last() {
 583             stmts = rest.iter().map(|s| self.lower_stmt(s)).collect::<Vec<_>>();
 584             let last = self.lower_stmt(last);
 585             if let hir::StmtExpr(e, _) = last.node {
 586                 expr = Some(e);
 587             } else {
 588                 stmts.push(last);
 589             }
 590         }
 591
 592         P(hir::Block {
 593             id: b.id,
 594             stmts: stmts.into(),
 595             expr: expr,
 596             rules: self.lower_block_check_mode(&b.rules),
 597             span: b.span,
 598         })
 599     }
 600
 601     fn lower_item_kind(&mut self, i: &ItemKind) -> hir::Item_ {
 602         match *i {
 603             ItemKind::ExternCrate(string) => hir::ItemExternCrate(string),
 604             ItemKind::Use(ref view_path) => {
 605                 hir::ItemUse(self.lower_view_path(view_path))
 606             }
 607             ItemKind::Static(ref t, m, ref e) => {
 608                 hir::ItemStatic(self.lower_ty(t),
 609                                 self.lower_mutability(m),
 610                                 self.lower_expr(e))
 611             }
 612             ItemKind::Const(ref t, ref e) => {
 613                 hir::ItemConst(self.lower_ty(t), self.lower_expr(e))
 614             }
 615             ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 616                 hir::ItemFn(self.lower_fn_decl(decl),
 617                             self.lower_unsafety(unsafety),
 618                             self.lower_constness(constness),
 619                             abi,
 620                             self.lower_generics(generics),
 621                             self.lower_block(body))
 622             }
 623             ItemKind::Mod(ref m) => hir::ItemMod(self.lower_mod(m)),
 624             ItemKind::ForeignMod(ref nm) => hir::ItemForeignMod(self.lower_foreign_mod(nm)),
 625             ItemKind::Ty(ref t, ref generics) => {
 626                 hir::ItemTy(self.lower_ty(t), self.lower_generics(generics))
 627             }
 628             ItemKind::Enum(ref enum_definition, ref generics) => {
 629                 hir::ItemEnum(hir::EnumDef {
 630                                   variants: enum_definition.variants
 631                                                            .iter()
 632                                                            .map(|x| self.lower_variant(x))
 633                                                            .collect(),
 634                               },
 635                               self.lower_generics(generics))
 636             }
 637             ItemKind::Struct(ref struct_def, ref generics) => {
 638                 let struct_def = self.lower_variant_data(struct_def);
 639                 hir::ItemStruct(struct_def, self.lower_generics(generics))
 640             }
 641             ItemKind::Union(..) => panic!("`union` is not yet implemented"),
 642             ItemKind::DefaultImpl(unsafety, ref trait_ref) => {
 643                 hir::ItemDefaultImpl(self.lower_unsafety(unsafety),
 644                                      self.lower_trait_ref(trait_ref))
 645             }
 646             ItemKind::Impl(unsafety, polarity, ref generics, ref ifce, ref ty, ref impl_items) => {
 647                 let new_impl_items = impl_items.iter()
 648                                                .map(|item| self.lower_impl_item(item))
 649                                                .collect();
 650                 let ifce = ifce.as_ref().map(|trait_ref| self.lower_trait_ref(trait_ref));
 651                 hir::ItemImpl(self.lower_unsafety(unsafety),
 652                               self.lower_impl_polarity(polarity),
 653                               self.lower_generics(generics),
 654                               ifce,
 655                               self.lower_ty(ty),
 656                               new_impl_items)
 657             }
 658             ItemKind::Trait(unsafety, ref generics, ref bounds, ref items) => {
 659                 let bounds = self.lower_bounds(bounds);
 660                 let items = items.iter().map(|item| self.lower_trait_item(item)).collect();
 661                 hir::ItemTrait(self.lower_unsafety(unsafety),
 662                                self.lower_generics(generics),
 663                                bounds,
 664                                items)
 665             }
 666             ItemKind::Mac(_) => panic!("Shouldn't still be around"),
 667         }
 668     }
 669
 670     fn lower_trait_item(&mut self, i: &TraitItem) -> hir::TraitItem {
 671         self.with_parent_def(i.id, |this| {
 672             hir::TraitItem {
 673                 id: i.id,
 674                 name: i.ident.name,
 675                 attrs: this.lower_attrs(&i.attrs),
 676                 node: match i.node {
 677                     TraitItemKind::Const(ref ty, ref default) => {
 678                         hir::ConstTraitItem(this.lower_ty(ty),
 679                                             default.as_ref().map(|x| this.lower_expr(x)))
 680                     }
 681                     TraitItemKind::Method(ref sig, ref body) => {
 682                         hir::MethodTraitItem(this.lower_method_sig(sig),
 683                                              body.as_ref().map(|x| this.lower_block(x)))
 684                     }
 685                     TraitItemKind::Type(ref bounds, ref default) => {
 686                         hir::TypeTraitItem(this.lower_bounds(bounds),
 687                                            default.as_ref().map(|x| this.lower_ty(x)))
 688                     }
 689                     TraitItemKind::Macro(..) => panic!("Shouldn't exist any more"),
 690                 },
 691                 span: i.span,
 692             }
 693         })
 694     }
 695
 696     fn lower_impl_item(&mut self, i: &ImplItem) -> hir::ImplItem {
 697         self.with_parent_def(i.id, |this| {
 698             hir::ImplItem {
 699                 id: i.id,
 700                 name: i.ident.name,
 701                 attrs: this.lower_attrs(&i.attrs),
 702                 vis: this.lower_visibility(&i.vis),
 703                 defaultness: this.lower_defaultness(i.defaultness),
 704                 node: match i.node {
 705                     ImplItemKind::Const(ref ty, ref expr) => {
 706                         hir::ImplItemKind::Const(this.lower_ty(ty), this.lower_expr(expr))
 707                     }
 708                     ImplItemKind::Method(ref sig, ref body) => {
 709                         hir::ImplItemKind::Method(this.lower_method_sig(sig),
 710                                                   this.lower_block(body))
 711                     }
 712                     ImplItemKind::Type(ref ty) => hir::ImplItemKind::Type(this.lower_ty(ty)),
 713                     ImplItemKind::Macro(..) => panic!("Shouldn't exist any more"),
 714                 },
 715                 span: i.span,
 716             }
 717         })
 718     }
 719
 720     fn lower_mod(&mut self, m: &Mod) -> hir::Mod {
 721         hir::Mod {
 722             inner: m.inner,
 723             item_ids: m.items.iter().map(|x| self.lower_item_id(x)).collect(),
 724         }
 725     }
 726
 727     fn lower_macro_def(&mut self, m: &MacroDef) -> hir::MacroDef {
 728         hir::MacroDef {
 729             name: m.ident.name,
 730             attrs: self.lower_attrs(&m.attrs),
 731             id: m.id,
 732             span: m.span,
 733             imported_from: m.imported_from.map(|x| x.name),
 734             export: m.export,
 735             use_locally: m.use_locally,
 736             allow_internal_unstable: m.allow_internal_unstable,
 737             body: m.body.clone().into(),
 738         }
 739     }
 740
 741     fn lower_item_id(&mut self, i: &Item) -> hir::ItemId {
 742         hir::ItemId { id: i.id }
 743     }
 744
 745     pub fn lower_item(&mut self, i: &Item) -> hir::Item {
 746         let node = self.with_parent_def(i.id, |this| {
 747             this.lower_item_kind(&i.node)
 748         });
 749
 750         hir::Item {
 751             id: i.id,
 752             name: i.ident.name,
 753             attrs: self.lower_attrs(&i.attrs),
 754             node: node,
 755             vis: self.lower_visibility(&i.vis),
 756             span: i.span,
 757         }
 758     }
 759
 760     fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem {
 761         self.with_parent_def(i.id, |this| {
 762             hir::ForeignItem {
 763                 id: i.id,
 764                 name: i.ident.name,
 765                 attrs: this.lower_attrs(&i.attrs),
 766                 node: match i.node {
 767                     ForeignItemKind::Fn(ref fdec, ref generics) => {
 768                         hir::ForeignItemFn(this.lower_fn_decl(fdec), this.lower_generics(generics))
 769                     }
 770                     ForeignItemKind::Static(ref t, m) => {
 771                         hir::ForeignItemStatic(this.lower_ty(t), m)
 772                     }
 773                 },
 774                 vis: this.lower_visibility(&i.vis),
 775                 span: i.span,
 776             }
 777         })
 778     }
 779
 780     fn lower_method_sig(&mut self, sig: &MethodSig) -> hir::MethodSig {
 781         let hir_sig = hir::MethodSig {
 782             generics: self.lower_generics(&sig.generics),
 783             abi: sig.abi,
 784             unsafety: self.lower_unsafety(sig.unsafety),
 785             constness: self.lower_constness(sig.constness),
 786             decl: self.lower_fn_decl(&sig.decl),
 787         };
 788         // Check for `self: _` and `self: &_`
 789         if let Some(SelfKind::Explicit(..)) = sig.decl.get_self().map(|eself| eself.node) {
 790             match hir_sig.decl.get_self().map(|eself| eself.node) {
 791                 Some(hir::SelfKind::Value(..)) | Some(hir::SelfKind::Region(..)) => {
 792                     self.diagnostic().span_err(sig.decl.inputs[0].ty.span,
 793                         "the type placeholder `_` is not allowed within types on item signatures");
 794                 }
 795                 _ => {}
 796             }
 797         }
 798         hir_sig
 799     }
 800
 801     fn lower_unsafety(&mut self, u: Unsafety) -> hir::Unsafety {
 802         match u {
 803             Unsafety::Unsafe => hir::Unsafety::Unsafe,
 804             Unsafety::Normal => hir::Unsafety::Normal,
 805         }
 806     }
 807
 808     fn lower_constness(&mut self, c: Spanned<Constness>) -> hir::Constness {
 809         match c.node {
 810             Constness::Const => hir::Constness::Const,
 811             Constness::NotConst => hir::Constness::NotConst,
 812         }
 813     }
 814
 815     fn lower_unop(&mut self, u: UnOp) -> hir::UnOp {
 816         match u {
 817             UnOp::Deref => hir::UnDeref,
 818             UnOp::Not => hir::UnNot,
 819             UnOp::Neg => hir::UnNeg,
 820         }
 821     }
 822
 823     fn lower_binop(&mut self, b: BinOp) -> hir::BinOp {
 824         Spanned {
 825             node: match b.node {
 826                 BinOpKind::Add => hir::BiAdd,
 827                 BinOpKind::Sub => hir::BiSub,
 828                 BinOpKind::Mul => hir::BiMul,
 829                 BinOpKind::Div => hir::BiDiv,
 830                 BinOpKind::Rem => hir::BiRem,
 831                 BinOpKind::And => hir::BiAnd,
 832                 BinOpKind::Or => hir::BiOr,
 833                 BinOpKind::BitXor => hir::BiBitXor,
 834                 BinOpKind::BitAnd => hir::BiBitAnd,
 835                 BinOpKind::BitOr => hir::BiBitOr,
 836                 BinOpKind::Shl => hir::BiShl,
 837                 BinOpKind::Shr => hir::BiShr,
 838                 BinOpKind::Eq => hir::BiEq,
 839                 BinOpKind::Lt => hir::BiLt,
 840                 BinOpKind::Le => hir::BiLe,
 841                 BinOpKind::Ne => hir::BiNe,
 842                 BinOpKind::Ge => hir::BiGe,
 843                 BinOpKind::Gt => hir::BiGt,
 844             },
 845             span: b.span,
 846         }
 847     }
 848
 849     fn lower_pat(&mut self, p: &Pat) -> P<hir::Pat> {
 850         P(hir::Pat {
 851             id: p.id,
 852             node: match p.node {
 853                 PatKind::Wild => hir::PatKind::Wild,
 854                 PatKind::Ident(ref binding_mode, pth1, ref sub) => {
 855                     self.with_parent_def(p.id, |this| {
 856                         match this.resolver.get_resolution(p.id).map(|d| d.base_def) {
 857                             // `None` can occur in body-less function signatures
 858                             None | Some(Def::Local(..)) => {
 859                                 hir::PatKind::Binding(this.lower_binding_mode(binding_mode),
 860                                                       respan(pth1.span, pth1.node.name),
 861                                                       sub.as_ref().map(|x| this.lower_pat(x)))
 862                             }
 863                             _ => hir::PatKind::Path(None, hir::Path::from_name(pth1.span,
 864                                                                                pth1.node.name))
 865                         }
 866                     })
 867                 }
 868                 PatKind::Lit(ref e) => hir::PatKind::Lit(self.lower_expr(e)),
 869                 PatKind::TupleStruct(ref pth, ref pats, ddpos) => {
 870                     hir::PatKind::TupleStruct(self.lower_path(pth),
 871                                               pats.iter().map(|x| self.lower_pat(x)).collect(),
 872                                               ddpos)
 873                 }
 874                 PatKind::Path(ref opt_qself, ref path) => {
 875                     let opt_qself = opt_qself.as_ref().map(|qself| {
 876                         hir::QSelf { ty: self.lower_ty(&qself.ty), position: qself.position }
 877                     });
 878                     hir::PatKind::Path(opt_qself, self.lower_path(path))
 879                 }
 880                 PatKind::Struct(ref pth, ref fields, etc) => {
 881                     let pth = self.lower_path(pth);
 882                     let fs = fields.iter()
 883                                    .map(|f| {
 884                                        Spanned {
 885                                            span: f.span,
 886                                            node: hir::FieldPat {
 887                                                name: f.node.ident.name,
 888                                                pat: self.lower_pat(&f.node.pat),
 889                                                is_shorthand: f.node.is_shorthand,
 890                                            },
 891                                        }
 892                                    })
 893                                    .collect();
 894                     hir::PatKind::Struct(pth, fs, etc)
 895                 }
 896                 PatKind::Tuple(ref elts, ddpos) => {
 897                     hir::PatKind::Tuple(elts.iter().map(|x| self.lower_pat(x)).collect(), ddpos)
 898                 }
 899                 PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)),
 900                 PatKind::Ref(ref inner, mutbl) => {
 901                     hir::PatKind::Ref(self.lower_pat(inner), self.lower_mutability(mutbl))
 902                 }
 903                 PatKind::Range(ref e1, ref e2) => {
 904                     hir::PatKind::Range(self.lower_expr(e1), self.lower_expr(e2))
 905                 }
 906                 PatKind::Vec(ref before, ref slice, ref after) => {
 907                     hir::PatKind::Vec(before.iter().map(|x| self.lower_pat(x)).collect(),
 908                                 slice.as_ref().map(|x| self.lower_pat(x)),
 909                                 after.iter().map(|x| self.lower_pat(x)).collect())
 910                 }
 911                 PatKind::Mac(_) => panic!("Shouldn't exist here"),
 912             },
 913             span: p.span,
 914         })
 915     }
 916
 917     fn lower_expr(&mut self, e: &Expr) -> P<hir::Expr> {
 918         P(hir::Expr {
 919             id: e.id,
 920             node: match e.node {
 921                 // Issue #22181:
 922                 // Eventually a desugaring for `box EXPR`
 923                 // (similar to the desugaring above for `in PLACE BLOCK`)
 924                 // should go here, desugaring
 925                 //
 926                 // to:
 927                 //
 928                 // let mut place = BoxPlace::make_place();
 929                 // let raw_place = Place::pointer(&mut place);
 930                 // let value = $value;
 931                 // unsafe {
 932                 //     ::std::ptr::write(raw_place, value);
 933                 //     Boxed::finalize(place)
 934                 // }
 935                 //
 936                 // But for now there are type-inference issues doing that.
 937                 ExprKind::Box(ref e) => {
 938                     hir::ExprBox(self.lower_expr(e))
 939                 }
 940
 941                 // Desugar ExprBox: `in (PLACE) EXPR`
 942                 ExprKind::InPlace(ref placer, ref value_expr) => {
 943                     // to:
 944                     //
 945                     // let p = PLACE;
 946                     // let mut place = Placer::make_place(p);
 947                     // let raw_place = Place::pointer(&mut place);
 948                     // push_unsafe!({
 949                     //     std::intrinsics::move_val_init(raw_place, pop_unsafe!( EXPR ));
 950                     //     InPlace::finalize(place)
 951                     // })
 952                     let placer_expr = self.lower_expr(placer);
 953                     let value_expr = self.lower_expr(value_expr);
 954
 955                     let placer_ident = self.str_to_ident("placer");
 956                     let place_ident = self.str_to_ident("place");
 957                     let p_ptr_ident = self.str_to_ident("p_ptr");
 958
 959                     let make_place = ["ops", "Placer", "make_place"];
 960                     let place_pointer = ["ops", "Place", "pointer"];
 961                     let move_val_init = ["intrinsics", "move_val_init"];
 962                     let inplace_finalize = ["ops", "InPlace", "finalize"];
 963
 964                     let make_call = |this: &mut LoweringContext, p, args| {
 965                         let path = this.std_path(e.span, p);
 966                         let path = this.expr_path(path, ThinVec::new());
 967                         this.expr_call(e.span, path, args)
 968                     };
 969
 970                     let mk_stmt_let = |this: &mut LoweringContext, bind, expr| {
 971                         this.stmt_let(e.span, false, bind, expr)
 972                     };
 973
 974                     let mk_stmt_let_mut = |this: &mut LoweringContext, bind, expr| {
 975                         this.stmt_let(e.span, true, bind, expr)
 976                     };
 977
 978                     // let placer = <placer_expr> ;
 979                     let (s1, placer_binding) = {
 980                         let placer_expr = self.signal_block_expr(hir_vec![],
 981                                                                  placer_expr,
 982                                                                  e.span,
 983                                                                  hir::PopUnstableBlock,
 984                                                                  ThinVec::new());
 985                         mk_stmt_let(self, placer_ident, placer_expr)
 986                     };
 987
 988                     // let mut place = Placer::make_place(placer);
 989                     let (s2, place_binding) = {
 990                         let placer = self.expr_ident(e.span, placer_ident, placer_binding);
 991                         let call = make_call(self, &make_place, hir_vec![placer]);
 992                         mk_stmt_let_mut(self, place_ident, call)
 993                     };
 994
 995                     // let p_ptr = Place::pointer(&mut place);
 996                     let (s3, p_ptr_binding) = {
 997                         let agent = self.expr_ident(e.span, place_ident, place_binding);
 998                         let args = hir_vec![self.expr_mut_addr_of(e.span, agent)];
 999                         let call = make_call(self, &place_pointer, args);
1000                         mk_stmt_let(self, p_ptr_ident, call)
1001                     };
1002
1003                     // pop_unsafe!(EXPR));
1004                     let pop_unsafe_expr = {
1005                         let value_expr = self.signal_block_expr(hir_vec![],
1006                                                                 value_expr,
1007                                                                 e.span,
1008                                                                 hir::PopUnstableBlock,
1009                                                                 ThinVec::new());
1010                         self.signal_block_expr(hir_vec![],
1011                                                value_expr,
1012                                                e.span,
1013                                                hir::PopUnsafeBlock(hir::CompilerGenerated),
1014                                                ThinVec::new())
1015                     };
1016
1017                     // push_unsafe!({
1018                     //     std::intrinsics::move_val_init(raw_place, pop_unsafe!( EXPR ));
1019                     //     InPlace::finalize(place)
1020                     // })
1021                     let expr = {
1022                         let ptr = self.expr_ident(e.span, p_ptr_ident, p_ptr_binding);
1023                         let call_move_val_init =
1024                             hir::StmtSemi(
1025                                 make_call(self, &move_val_init, hir_vec![ptr, pop_unsafe_expr]),
1026                                 self.next_id());
1027                         let call_move_val_init = respan(e.span, call_move_val_init);
1028
1029                         let place = self.expr_ident(e.span, place_ident, place_binding);
1030                         let call = make_call(self, &inplace_finalize, hir_vec![place]);
1031                         self.signal_block_expr(hir_vec![call_move_val_init],
1032                                                call,
1033                                                e.span,
1034                                                hir::PushUnsafeBlock(hir::CompilerGenerated),
1035                                                ThinVec::new())
1036                     };
1037
1038                     return self.signal_block_expr(hir_vec![s1, s2, s3],
1039                                                   expr,
1040                                                   e.span,
1041                                                   hir::PushUnstableBlock,
1042                                                   e.attrs.clone());
1043                 }
1044
1045                 ExprKind::Vec(ref exprs) => {
1046                     hir::ExprVec(exprs.iter().map(|x| self.lower_expr(x)).collect())
1047                 }
1048                 ExprKind::Repeat(ref expr, ref count) => {
1049                     let expr = self.lower_expr(expr);
1050                     let count = self.lower_expr(count);
1051                     hir::ExprRepeat(expr, count)
1052                 }
1053                 ExprKind::Tup(ref elts) => {
1054                     hir::ExprTup(elts.iter().map(|x| self.lower_expr(x)).collect())
1055                 }
1056                 ExprKind::Call(ref f, ref args) => {
1057                     let f = self.lower_expr(f);
1058                     hir::ExprCall(f, args.iter().map(|x| self.lower_expr(x)).collect())
1059                 }
1060                 ExprKind::MethodCall(i, ref tps, ref args) => {
1061                     let tps = tps.iter().map(|x| self.lower_ty(x)).collect();
1062                     let args = args.iter().map(|x| self.lower_expr(x)).collect();
1063                     hir::ExprMethodCall(respan(i.span, i.node.name), tps, args)
1064                 }
1065                 ExprKind::Binary(binop, ref lhs, ref rhs) => {
1066                     let binop = self.lower_binop(binop);
1067                     let lhs = self.lower_expr(lhs);
1068                     let rhs = self.lower_expr(rhs);
1069                     hir::ExprBinary(binop, lhs, rhs)
1070                 }
1071                 ExprKind::Unary(op, ref ohs) => {
1072                     let op = self.lower_unop(op);
1073                     let ohs = self.lower_expr(ohs);
1074                     hir::ExprUnary(op, ohs)
1075                 }
1076                 ExprKind::Lit(ref l) => hir::ExprLit(P((**l).clone())),
1077                 ExprKind::Cast(ref expr, ref ty) => {
1078                     let expr = self.lower_expr(expr);
1079                     hir::ExprCast(expr, self.lower_ty(ty))
1080                 }
1081                 ExprKind::Type(ref expr, ref ty) => {
1082                     let expr = self.lower_expr(expr);
1083                     hir::ExprType(expr, self.lower_ty(ty))
1084                 }
1085                 ExprKind::AddrOf(m, ref ohs) => {
1086                     let m = self.lower_mutability(m);
1087                     let ohs = self.lower_expr(ohs);
1088                     hir::ExprAddrOf(m, ohs)
1089                 }
1090                 // More complicated than you might expect because the else branch
1091                 // might be `if let`.
1092                 ExprKind::If(ref cond, ref blk, ref else_opt) => {
1093                     let else_opt = else_opt.as_ref().map(|els| {
1094                         match els.node {
1095                             ExprKind::IfLet(..) => {
1096                                 // wrap the if-let expr in a block
1097                                 let span = els.span;
1098                                 let els = self.lower_expr(els);
1099                                 let id = self.next_id();
1100                                 let blk = P(hir::Block {
1101                                     stmts: hir_vec![],
1102                                     expr: Some(els),
1103                                     id: id,
1104                                     rules: hir::DefaultBlock,
1105                                     span: span,
1106                                 });
1107                                 self.expr_block(blk, ThinVec::new())
1108                             }
1109                             _ => self.lower_expr(els),
1110                         }
1111                     });
1112
1113                     hir::ExprIf(self.lower_expr(cond), self.lower_block(blk), else_opt)
1114                 }
1115                 ExprKind::While(ref cond, ref body, opt_ident) => {
1116                     hir::ExprWhile(self.lower_expr(cond), self.lower_block(body),
1117                                    self.lower_opt_sp_ident(opt_ident))
1118                 }
1119                 ExprKind::Loop(ref body, opt_ident) => {
1120                     hir::ExprLoop(self.lower_block(body), self.lower_opt_sp_ident(opt_ident))
1121                 }
1122                 ExprKind::Match(ref expr, ref arms) => {
1123                     hir::ExprMatch(self.lower_expr(expr),
1124                                    arms.iter().map(|x| self.lower_arm(x)).collect(),
1125                                    hir::MatchSource::Normal)
1126                 }
1127                 ExprKind::Closure(capture_clause, ref decl, ref body, fn_decl_span) => {
1128                     self.with_parent_def(e.id, |this| {
1129                         hir::ExprClosure(this.lower_capture_clause(capture_clause),
1130                                          this.lower_fn_decl(decl),
1131                                          this.lower_block(body),
1132                                          fn_decl_span)
1133                     })
1134                 }
1135                 ExprKind::Block(ref blk) => hir::ExprBlock(self.lower_block(blk)),
1136                 ExprKind::Assign(ref el, ref er) => {
1137                     hir::ExprAssign(self.lower_expr(el), self.lower_expr(er))
1138                 }
1139                 ExprKind::AssignOp(op, ref el, ref er) => {
1140                     hir::ExprAssignOp(self.lower_binop(op),
1141                                       self.lower_expr(el),
1142                                       self.lower_expr(er))
1143                 }
1144                 ExprKind::Field(ref el, ident) => {
1145                     hir::ExprField(self.lower_expr(el), respan(ident.span, ident.node.name))
1146                 }
1147                 ExprKind::TupField(ref el, ident) => {
1148                     hir::ExprTupField(self.lower_expr(el), ident)
1149                 }
1150                 ExprKind::Index(ref el, ref er) => {
1151                     hir::ExprIndex(self.lower_expr(el), self.lower_expr(er))
1152                 }
1153                 ExprKind::Range(ref e1, ref e2, lims) => {
1154                     fn make_struct(this: &mut LoweringContext,
1155                                    ast_expr: &Expr,
1156                                    path: &[&str],
1157                                    fields: &[(&str, &P<Expr>)]) -> P<hir::Expr> {
1158                         let struct_path = this.std_path(ast_expr.span,
1159                                                         &iter::once(&"ops").chain(path)
1160                                                                            .map(|s| *s)
1161                                                                            .collect::<Vec<_>>());
1162
1163                         let hir_expr = if fields.len() == 0 {
1164                             this.expr_path(struct_path, 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, struct_path, 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 = self.std_path(e.span, &["iter", "Iterator", "next"]);
1461                         let iter = self.expr_ident(e.span, iter, iter_pat.id);
1462                         let ref_mut_iter = self.expr_mut_addr_of(e.span, iter);
1463                         let next_path = self.expr_path(next_path, ThinVec::new());
1464                         let next_expr = self.expr_call(e.span, next_path, hir_vec![ref_mut_iter]);
1465                         let arms = hir_vec![pat_arm, break_arm];
1466
1467                         self.expr(e.span,
1468                                   hir::ExprMatch(next_expr, arms, hir::MatchSource::ForLoopDesugar),
1469                                   ThinVec::new())
1470                     };
1471
1472                     // `[opt_ident]: loop { ... }`
1473                     let loop_block = self.block_expr(match_expr);
1474                     let loop_expr = hir::ExprLoop(loop_block, self.lower_opt_sp_ident(opt_ident));
1475                     let loop_expr = P(hir::Expr {
1476                         id: e.id,
1477                         node: loop_expr,
1478                         span: e.span,
1479                         attrs: ThinVec::new(),
1480                     });
1481
1482                     // `mut iter => { ... }`
1483                     let iter_arm = self.arm(hir_vec![iter_pat], loop_expr);
1484
1485                     // `match ::std::iter::IntoIterator::into_iter(<head>) { ... }`
1486                     let into_iter_expr = {
1487                         let into_iter_path = self.std_path(e.span,
1488                                                            &["iter", "IntoIterator", "into_iter"]);
1489
1490                         let into_iter = self.expr_path(into_iter_path, ThinVec::new());
1491                         self.expr_call(e.span, into_iter, hir_vec![head])
1492                     };
1493
1494                     let match_expr = self.expr_match(e.span,
1495                                                      into_iter_expr,
1496                                                      hir_vec![iter_arm],
1497                                                      hir::MatchSource::ForLoopDesugar);
1498
1499                     // `{ let _result = ...; _result }`
1500                     // underscore prevents an unused_variables lint if the head diverges
1501                     let result_ident = self.str_to_ident("_result");
1502                     let (let_stmt, let_stmt_binding) =
1503                         self.stmt_let(e.span, false, result_ident, match_expr);
1504
1505                     let result = self.expr_ident(e.span, result_ident, let_stmt_binding);
1506                     let block = self.block_all(e.span, hir_vec![let_stmt], Some(result));
1507                     // add the attributes to the outer returned expr node
1508                     return self.expr_block(block, e.attrs.clone());
1509                 }
1510
1511                 // Desugar ExprKind::Try
1512                 // From: `<expr>?`
1513                 ExprKind::Try(ref sub_expr) => {
1514                     // to:
1515                     //
1516                     // {
1517                     //     match { Carrier::translate( { <expr> } ) } {
1518                     //         Ok(val) => val,
1519                     //         Err(err) => { return Carrier::from_error(From::from(err)); }
1520                     //     }
1521                     // }
1522
1523                     // { Carrier::translate( { <expr> } ) }
1524                     let discr = {
1525                         // expand <expr>
1526                         let sub_expr = self.lower_expr(sub_expr);
1527                         let sub_expr = self.signal_block_expr(hir_vec![],
1528                                                               sub_expr,
1529                                                               e.span,
1530                                                               hir::PopUnstableBlock,
1531                                                               ThinVec::new());
1532
1533                         let path = self.std_path(e.span, &["ops", "Carrier", "translate"]);
1534                         let path = self.expr_path(path, ThinVec::new());
1535                         let call = self.expr_call(e.span, path, hir_vec![sub_expr]);
1536
1537                         self.signal_block_expr(hir_vec![],
1538                                                call,
1539                                                e.span,
1540                                                hir::PushUnstableBlock,
1541                                                ThinVec::new())
1542                     };
1543
1544                     // Ok(val) => val
1545                     let ok_arm = {
1546                         let val_ident = self.str_to_ident("val");
1547                         let val_pat = self.pat_ident(e.span, val_ident);
1548                         let val_expr = self.expr_ident(e.span, val_ident, val_pat.id);
1549                         let ok_pat = self.pat_ok(e.span, val_pat);
1550
1551                         self.arm(hir_vec![ok_pat], val_expr)
1552                     };
1553
1554                     // Err(err) => { return Carrier::from_error(From::from(err)); }
1555                     let err_arm = {
1556                         let err_ident = self.str_to_ident("err");
1557                         let err_local = self.pat_ident(e.span, err_ident);
1558                         let from_expr = {
1559                             let path = self.std_path(e.span, &["convert", "From", "from"]);
1560                             let from = self.expr_path(path, ThinVec::new());
1561                             let err_expr = self.expr_ident(e.span, err_ident, err_local.id);
1562
1563                             self.expr_call(e.span, from, hir_vec![err_expr])
1564                         };
1565                         let from_err_expr = {
1566                             let path = self.std_path(e.span, &["ops", "Carrier", "from_error"]);
1567                             let from_err = self.expr_path(path, ThinVec::new());
1568                             self.expr_call(e.span, from_err, hir_vec![from_expr])
1569                         };
1570
1571                         let ret_expr = self.expr(e.span,
1572                                                  hir::Expr_::ExprRet(Some(from_err_expr)),
1573                                                                      ThinVec::new());
1574                         let ret_stmt = self.stmt_expr(ret_expr);
1575                         let block = self.signal_block_stmt(ret_stmt, e.span,
1576                                                            hir::PushUnstableBlock, ThinVec::new());
1577
1578                         let err_pat = self.pat_err(e.span, err_local);
1579                         self.arm(hir_vec![err_pat], block)
1580                     };
1581
1582                     return self.expr_match(e.span, discr, hir_vec![err_arm, ok_arm],
1583                                            hir::MatchSource::TryDesugar);
1584                 }
1585
1586                 ExprKind::Mac(_) => panic!("Shouldn't exist here"),
1587             },
1588             span: e.span,
1589             attrs: e.attrs.clone(),
1590         })
1591     }
1592
1593     fn lower_stmt(&mut self, s: &Stmt) -> hir::Stmt {
1594         match s.node {
1595             StmtKind::Local(ref l) => Spanned {
1596                 node: hir::StmtDecl(P(Spanned {
1597                     node: hir::DeclLocal(self.lower_local(l)),
1598                     span: s.span,
1599                 }), s.id),
1600                 span: s.span,
1601             },
1602             StmtKind::Item(ref it) => Spanned {
1603                 node: hir::StmtDecl(P(Spanned {
1604                     node: hir::DeclItem(self.lower_item_id(it)),
1605                     span: s.span,
1606                 }), s.id),
1607                 span: s.span,
1608             },
1609             StmtKind::Expr(ref e) => {
1610                 Spanned {
1611                     node: hir::StmtExpr(self.lower_expr(e), s.id),
1612                     span: s.span,
1613                 }
1614             }
1615             StmtKind::Semi(ref e) => {
1616                 Spanned {
1617                     node: hir::StmtSemi(self.lower_expr(e), s.id),
1618                     span: s.span,
1619                 }
1620             }
1621             StmtKind::Mac(..) => panic!("Shouldn't exist here"),
1622         }
1623     }
1624
1625     fn lower_capture_clause(&mut self, c: CaptureBy) -> hir::CaptureClause {
1626         match c {
1627             CaptureBy::Value => hir::CaptureByValue,
1628             CaptureBy::Ref => hir::CaptureByRef,
1629         }
1630     }
1631
1632     fn lower_visibility(&mut self, v: &Visibility) -> hir::Visibility {
1633         match *v {
1634             Visibility::Public => hir::Public,
1635             Visibility::Crate(_) => hir::Visibility::Crate,
1636             Visibility::Restricted { ref path, id } =>
1637                 hir::Visibility::Restricted { path: P(self.lower_path(path)), id: id },
1638             Visibility::Inherited => hir::Inherited,
1639         }
1640     }
1641
1642     fn lower_defaultness(&mut self, d: Defaultness) -> hir::Defaultness {
1643         match d {
1644             Defaultness::Default => hir::Defaultness::Default,
1645             Defaultness::Final => hir::Defaultness::Final,
1646         }
1647     }
1648
1649     fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode {
1650         match *b {
1651             BlockCheckMode::Default => hir::DefaultBlock,
1652             BlockCheckMode::Unsafe(u) => hir::UnsafeBlock(self.lower_unsafe_source(u)),
1653         }
1654     }
1655
1656     fn lower_binding_mode(&mut self, b: &BindingMode) -> hir::BindingMode {
1657         match *b {
1658             BindingMode::ByRef(m) => hir::BindByRef(self.lower_mutability(m)),
1659             BindingMode::ByValue(m) => hir::BindByValue(self.lower_mutability(m)),
1660         }
1661     }
1662
1663     fn lower_unsafe_source(&mut self, u: UnsafeSource) -> hir::UnsafeSource {
1664         match u {
1665             CompilerGenerated => hir::CompilerGenerated,
1666             UserProvided => hir::UserProvided,
1667         }
1668     }
1669
1670     fn lower_impl_polarity(&mut self, i: ImplPolarity) -> hir::ImplPolarity {
1671         match i {
1672             ImplPolarity::Positive => hir::ImplPolarity::Positive,
1673             ImplPolarity::Negative => hir::ImplPolarity::Negative,
1674         }
1675     }
1676
1677     fn lower_trait_bound_modifier(&mut self, f: TraitBoundModifier) -> hir::TraitBoundModifier {
1678         match f {
1679             TraitBoundModifier::None => hir::TraitBoundModifier::None,
1680             TraitBoundModifier::Maybe => hir::TraitBoundModifier::Maybe,
1681         }
1682     }
1683
1684     // Helper methods for building HIR.
1685
1686     fn arm(&mut self, pats: hir::HirVec<P<hir::Pat>>, expr: P<hir::Expr>) -> hir::Arm {
1687         hir::Arm {
1688             attrs: hir_vec![],
1689             pats: pats,
1690             guard: None,
1691             body: expr,
1692         }
1693     }
1694
1695     fn field(&mut self, name: Name, expr: P<hir::Expr>, span: Span) -> hir::Field {
1696         hir::Field {
1697             name: Spanned {
1698                 node: name,
1699                 span: span,
1700             },
1701             span: span,
1702             expr: expr,
1703         }
1704     }
1705
1706     fn expr_break(&mut self, span: Span, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
1707         self.expr(span, hir::ExprBreak(None), attrs)
1708     }
1709
1710     fn expr_call(&mut self, span: Span, e: P<hir::Expr>, args: hir::HirVec<P<hir::Expr>>)
1711                  -> P<hir::Expr> {
1712         self.expr(span, hir::ExprCall(e, args), ThinVec::new())
1713     }
1714
1715     fn expr_ident(&mut self, span: Span, id: Name, binding: NodeId) -> P<hir::Expr> {
1716         let expr_path = hir::ExprPath(None, self.path_ident(span, id));
1717         let expr = self.expr(span, expr_path, ThinVec::new());
1718
1719         let def = self.resolver.definitions().map(|defs| {
1720             Def::Local(defs.local_def_id(binding), binding)
1721         }).unwrap_or(Def::Err);
1722         self.resolver.record_resolution(expr.id, def);
1723
1724         expr
1725     }
1726
1727     fn expr_mut_addr_of(&mut self, span: Span, e: P<hir::Expr>) -> P<hir::Expr> {
1728         self.expr(span, hir::ExprAddrOf(hir::MutMutable, e), ThinVec::new())
1729     }
1730
1731     fn expr_path(&mut self, path: hir::Path, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
1732         let def = self.resolver.resolve_generated_global_path(&path, true);
1733         let expr = self.expr(path.span, hir::ExprPath(None, path), attrs);
1734         self.resolver.record_resolution(expr.id, def);
1735         expr
1736     }
1737
1738     fn expr_match(&mut self,
1739                   span: Span,
1740                   arg: P<hir::Expr>,
1741                   arms: hir::HirVec<hir::Arm>,
1742                   source: hir::MatchSource)
1743                   -> P<hir::Expr> {
1744         self.expr(span, hir::ExprMatch(arg, arms, source), ThinVec::new())
1745     }
1746
1747     fn expr_block(&mut self, b: P<hir::Block>, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
1748         self.expr(b.span, hir::ExprBlock(b), attrs)
1749     }
1750
1751     fn expr_tuple(&mut self, sp: Span, exprs: hir::HirVec<P<hir::Expr>>) -> P<hir::Expr> {
1752         self.expr(sp, hir::ExprTup(exprs), ThinVec::new())
1753     }
1754
1755     fn expr_struct(&mut self,
1756                    sp: Span,
1757                    path: hir::Path,
1758                    fields: hir::HirVec<hir::Field>,
1759                    e: Option<P<hir::Expr>>,
1760                    attrs: ThinVec<Attribute>) -> P<hir::Expr> {
1761         let def = self.resolver.resolve_generated_global_path(&path, false);
1762         let expr = self.expr(sp, hir::ExprStruct(path, fields, e), attrs);
1763         self.resolver.record_resolution(expr.id, def);
1764         expr
1765     }
1766
1767     fn expr(&mut self, span: Span, node: hir::Expr_, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
1768         P(hir::Expr {
1769             id: self.next_id(),
1770             node: node,
1771             span: span,
1772             attrs: attrs,
1773         })
1774     }
1775
1776     fn stmt_let(&mut self, sp: Span, mutbl: bool, ident: Name, ex: P<hir::Expr>)
1777                 -> (hir::Stmt, NodeId) {
1778         let pat = if mutbl {
1779             self.pat_ident_binding_mode(sp, ident, hir::BindByValue(hir::MutMutable))
1780         } else {
1781             self.pat_ident(sp, ident)
1782         };
1783         let pat_id = pat.id;
1784         let local = P(hir::Local {
1785             pat: pat,
1786             ty: None,
1787             init: Some(ex),
1788             id: self.next_id(),
1789             span: sp,
1790             attrs: ThinVec::new(),
1791         });
1792         let decl = respan(sp, hir::DeclLocal(local));
1793         (respan(sp, hir::StmtDecl(P(decl), self.next_id())), pat_id)
1794     }
1795
1796     // Turns `<expr>` into `<expr>;`, note that this produces a StmtSemi, not a
1797     // StmtExpr.
1798     fn stmt_expr(&self, expr: P<hir::Expr>) -> hir::Stmt {
1799         hir::Stmt {
1800             span: expr.span,
1801             node: hir::StmtSemi(expr, self.next_id()),
1802         }
1803     }
1804
1805     fn block_expr(&mut self, expr: P<hir::Expr>) -> P<hir::Block> {
1806         self.block_all(expr.span, hir::HirVec::new(), Some(expr))
1807     }
1808
1809     fn block_all(&mut self, span: Span, stmts: hir::HirVec<hir::Stmt>, expr: Option<P<hir::Expr>>)
1810                  -> P<hir::Block> {
1811         P(hir::Block {
1812             stmts: stmts,
1813             expr: expr,
1814             id: self.next_id(),
1815             rules: hir::DefaultBlock,
1816             span: span,
1817         })
1818     }
1819
1820     fn pat_ok(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
1821         let path = self.std_path(span, &["result", "Result", "Ok"]);
1822         self.pat_enum(span, path, hir_vec![pat])
1823     }
1824
1825     fn pat_err(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
1826         let path = self.std_path(span, &["result", "Result", "Err"]);
1827         self.pat_enum(span, path, hir_vec![pat])
1828     }
1829
1830     fn pat_some(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
1831         let path = self.std_path(span, &["option", "Option", "Some"]);
1832         self.pat_enum(span, path, hir_vec![pat])
1833     }
1834
1835     fn pat_none(&mut self, span: Span) -> P<hir::Pat> {
1836         let path = self.std_path(span, &["option", "Option", "None"]);
1837         self.pat_enum(span, path, hir_vec![])
1838     }
1839
1840     fn pat_enum(&mut self, span: Span, path: hir::Path, subpats: hir::HirVec<P<hir::Pat>>)
1841                 -> P<hir::Pat> {
1842         let def = self.resolver.resolve_generated_global_path(&path, true);
1843         let pt = if subpats.is_empty() {
1844             hir::PatKind::Path(None, path)
1845         } else {
1846             hir::PatKind::TupleStruct(path, subpats, None)
1847         };
1848         let pat = self.pat(span, pt);
1849         self.resolver.record_resolution(pat.id, def);
1850         pat
1851     }
1852
1853     fn pat_ident(&mut self, span: Span, name: Name) -> P<hir::Pat> {
1854         self.pat_ident_binding_mode(span, name, hir::BindByValue(hir::MutImmutable))
1855     }
1856
1857     fn pat_ident_binding_mode(&mut self, span: Span, name: Name, bm: hir::BindingMode)
1858                               -> P<hir::Pat> {
1859         let pat_ident = hir::PatKind::Binding(bm,
1860                                             Spanned {
1861                                                 span: span,
1862                                                 node: name,
1863                                             },
1864                                             None);
1865
1866         let pat = self.pat(span, pat_ident);
1867
1868         let parent_def = self.parent_def;
1869         let def = self.resolver.definitions().map(|defs| {
1870             let def_path_data = DefPathData::Binding(name.as_str());
1871             let def_index = defs.create_def_with_parent(parent_def, pat.id, def_path_data);
1872             Def::Local(DefId::local(def_index), pat.id)
1873         }).unwrap_or(Def::Err);
1874         self.resolver.record_resolution(pat.id, def);
1875
1876         pat
1877     }
1878
1879     fn pat_wild(&mut self, span: Span) -> P<hir::Pat> {
1880         self.pat(span, hir::PatKind::Wild)
1881     }
1882
1883     fn pat(&mut self, span: Span, pat: hir::PatKind) -> P<hir::Pat> {
1884         P(hir::Pat {
1885             id: self.next_id(),
1886             node: pat,
1887             span: span,
1888         })
1889     }
1890
1891     fn path_ident(&mut self, span: Span, id: Name) -> hir::Path {
1892         self.path(span, vec![id])
1893     }
1894
1895     fn path(&mut self, span: Span, strs: Vec<Name>) -> hir::Path {
1896         self.path_all(span, false, strs, hir::HirVec::new(), hir::HirVec::new(), hir::HirVec::new())
1897     }
1898
1899     fn path_global(&mut self, span: Span, strs: Vec<Name>) -> hir::Path {
1900         self.path_all(span, true, strs, hir::HirVec::new(), hir::HirVec::new(), hir::HirVec::new())
1901     }
1902
1903     fn path_all(&mut self,
1904                 sp: Span,
1905                 global: bool,
1906                 mut names: Vec<Name>,
1907                 lifetimes: hir::HirVec<hir::Lifetime>,
1908                 types: hir::HirVec<P<hir::Ty>>,
1909                 bindings: hir::HirVec<hir::TypeBinding>)
1910                 -> hir::Path {
1911         let last_identifier = names.pop().unwrap();
1912         let mut segments: Vec<hir::PathSegment> = names.into_iter().map(|name| {
1913             hir::PathSegment {
1914                 name: name,
1915                 parameters: hir::PathParameters::none(),
1916            }
1917         }).collect();
1918
1919         segments.push(hir::PathSegment {
1920             name: last_identifier,
1921             parameters: hir::AngleBracketedParameters(hir::AngleBracketedParameterData {
1922                 lifetimes: lifetimes,
1923                 types: types,
1924                 bindings: bindings,
1925             }),
1926         });
1927         hir::Path {
1928             span: sp,
1929             global: global,
1930             segments: segments.into(),
1931         }
1932     }
1933
1934     fn std_path_components(&mut self, components: &[&str]) -> Vec<Name> {
1935         let mut v = Vec::new();
1936         if let Some(s) = self.crate_root {
1937             v.push(token::intern(s));
1938         }
1939         v.extend(components.iter().map(|s| token::intern(s)));
1940         return v;
1941     }
1942
1943     // Given suffix ["b","c","d"], returns path `::std::b::c::d` when
1944     // `fld.cx.use_std`, and `::core::b::c::d` otherwise.
1945     fn std_path(&mut self, span: Span, components: &[&str]) -> hir::Path {
1946         let idents = self.std_path_components(components);
1947         self.path_global(span, idents)
1948     }
1949
1950     fn signal_block_expr(&mut self,
1951                          stmts: hir::HirVec<hir::Stmt>,
1952                          expr: P<hir::Expr>,
1953                          span: Span,
1954                          rule: hir::BlockCheckMode,
1955                          attrs: ThinVec<Attribute>)
1956                          -> P<hir::Expr> {
1957         let id = self.next_id();
1958         let block = P(hir::Block {
1959             rules: rule,
1960             span: span,
1961             id: id,
1962             stmts: stmts,
1963             expr: Some(expr),
1964         });
1965         self.expr_block(block, attrs)
1966     }
1967
1968     fn signal_block_stmt(&mut self,
1969                          stmt: hir::Stmt,
1970                          span: Span,
1971                          rule: hir::BlockCheckMode,
1972                          attrs: ThinVec<Attribute>)
1973                          -> P<hir::Expr> {
1974         let id = self.next_id();
1975         let block = P(hir::Block {
1976             rules: rule,
1977             span: span,
1978             id: id,
1979             stmts: hir_vec![stmt],
1980             expr: None,
1981         });
1982         self.expr_block(block, attrs)
1983     }
1984 }