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: match path_list_ident.node {
 222                 PathListItemKind::Ident { id, name, rename } => hir::PathListIdent {
 223                     id: id,
 224                     name: name.name,
 225                     rename: rename.map(|x| x.name),
 226                 },
 227                 PathListItemKind::Mod { id, rename } => hir::PathListMod {
 228                     id: id,
 229                     rename: rename.map(|x| x.name),
 230                 },
 231             },
 232             span: path_list_ident.span,
 233         }
 234     }
 235
 236     fn lower_arm(&mut self, arm: &Arm) -> hir::Arm {
 237         hir::Arm {
 238             attrs: self.lower_attrs(&arm.attrs),
 239             pats: arm.pats.iter().map(|x| self.lower_pat(x)).collect(),
 240             guard: arm.guard.as_ref().map(|ref x| self.lower_expr(x)),
 241             body: self.lower_expr(&arm.body),
 242         }
 243     }
 244
 245     fn lower_ty_binding(&mut self, b: &TypeBinding) -> hir::TypeBinding {
 246         hir::TypeBinding {
 247             id: b.id,
 248             name: b.ident.name,
 249             ty: self.lower_ty(&b.ty),
 250             span: b.span,
 251         }
 252     }
 253
 254     fn lower_ty(&mut self, t: &Ty) -> P<hir::Ty> {
 255         use syntax::ast::TyKind::*;
 256         P(hir::Ty {
 257             id: t.id,
 258             node: match t.node {
 259                 Infer | ImplicitSelf => hir::TyInfer,
 260                 Vec(ref ty) => hir::TyVec(self.lower_ty(ty)),
 261                 Ptr(ref mt) => hir::TyPtr(self.lower_mt(mt)),
 262                 Rptr(ref region, ref mt) => {
 263                     hir::TyRptr(self.lower_opt_lifetime(region), self.lower_mt(mt))
 264                 }
 265                 BareFn(ref f) => {
 266                     hir::TyBareFn(P(hir::BareFnTy {
 267                         lifetimes: self.lower_lifetime_defs(&f.lifetimes),
 268                         unsafety: self.lower_unsafety(f.unsafety),
 269                         abi: f.abi,
 270                         decl: self.lower_fn_decl(&f.decl),
 271                     }))
 272                 }
 273                 Never => hir::TyNever,
 274                 Tup(ref tys) => hir::TyTup(tys.iter().map(|ty| self.lower_ty(ty)).collect()),
 275                 Paren(ref ty) => {
 276                     return self.lower_ty(ty);
 277                 }
 278                 Path(ref qself, ref path) => {
 279                     let qself = qself.as_ref().map(|&QSelf { ref ty, position }| {
 280                         hir::QSelf {
 281                             ty: self.lower_ty(ty),
 282                             position: position,
 283                         }
 284                     });
 285                     hir::TyPath(qself, self.lower_path(path))
 286                 }
 287                 ObjectSum(ref ty, ref bounds) => {
 288                     hir::TyObjectSum(self.lower_ty(ty), self.lower_bounds(bounds))
 289                 }
 290                 FixedLengthVec(ref ty, ref e) => {
 291                     hir::TyFixedLengthVec(self.lower_ty(ty), self.lower_expr(e))
 292                 }
 293                 Typeof(ref expr) => {
 294                     hir::TyTypeof(self.lower_expr(expr))
 295                 }
 296                 PolyTraitRef(ref bounds) => {
 297                     hir::TyPolyTraitRef(self.lower_bounds(bounds))
 298                 }
 299                 ImplTrait(ref bounds) => {
 300                     hir::TyImplTrait(self.lower_bounds(bounds))
 301                 }
 302                 Mac(_) => panic!("TyMac should have been expanded by now."),
 303             },
 304             span: t.span,
 305         })
 306     }
 307
 308     fn lower_foreign_mod(&mut self, fm: &ForeignMod) -> hir::ForeignMod {
 309         hir::ForeignMod {
 310             abi: fm.abi,
 311             items: fm.items.iter().map(|x| self.lower_foreign_item(x)).collect(),
 312         }
 313     }
 314
 315     fn lower_variant(&mut self, v: &Variant) -> hir::Variant {
 316         Spanned {
 317             node: hir::Variant_ {
 318                 name: v.node.name.name,
 319                 attrs: self.lower_attrs(&v.node.attrs),
 320                 data: self.lower_variant_data(&v.node.data),
 321                 disr_expr: v.node.disr_expr.as_ref().map(|e| self.lower_expr(e)),
 322             },
 323             span: v.span,
 324         }
 325     }
 326
 327     fn lower_path(&mut self, p: &Path) -> hir::Path {
 328         hir::Path {
 329             global: p.global,
 330             segments: p.segments
 331                        .iter()
 332                        .map(|&PathSegment { identifier, ref parameters }| {
 333                            hir::PathSegment {
 334                                name: identifier.name,
 335                                parameters: self.lower_path_parameters(parameters),
 336                            }
 337                        })
 338                        .collect(),
 339             span: p.span,
 340         }
 341     }
 342
 343     fn lower_path_parameters(&mut self, path_parameters: &PathParameters) -> hir::PathParameters {
 344         match *path_parameters {
 345             PathParameters::AngleBracketed(ref data) =>
 346                 hir::AngleBracketedParameters(self.lower_angle_bracketed_parameter_data(data)),
 347             PathParameters::Parenthesized(ref data) =>
 348                 hir::ParenthesizedParameters(self.lower_parenthesized_parameter_data(data)),
 349         }
 350     }
 351
 352     fn lower_angle_bracketed_parameter_data(&mut self,
 353                                             data: &AngleBracketedParameterData)
 354                                             -> hir::AngleBracketedParameterData {
 355         let &AngleBracketedParameterData { ref lifetimes, ref types, ref bindings } = data;
 356         hir::AngleBracketedParameterData {
 357             lifetimes: self.lower_lifetimes(lifetimes),
 358             types: types.iter().map(|ty| self.lower_ty(ty)).collect(),
 359             bindings: bindings.iter().map(|b| self.lower_ty_binding(b)).collect(),
 360         }
 361     }
 362
 363     fn lower_parenthesized_parameter_data(&mut self,
 364                                           data: &ParenthesizedParameterData)
 365                                           -> hir::ParenthesizedParameterData {
 366         let &ParenthesizedParameterData { ref inputs, ref output, span } = data;
 367         hir::ParenthesizedParameterData {
 368             inputs: inputs.iter().map(|ty| self.lower_ty(ty)).collect(),
 369             output: output.as_ref().map(|ty| self.lower_ty(ty)),
 370             span: span,
 371         }
 372     }
 373
 374     fn lower_local(&mut self, l: &Local) -> P<hir::Local> {
 375         P(hir::Local {
 376             id: l.id,
 377             ty: l.ty.as_ref().map(|t| self.lower_ty(t)),
 378             pat: self.lower_pat(&l.pat),
 379             init: l.init.as_ref().map(|e| self.lower_expr(e)),
 380             span: l.span,
 381             attrs: l.attrs.clone(),
 382         })
 383     }
 384
 385     fn lower_mutability(&mut self, m: Mutability) -> hir::Mutability {
 386         match m {
 387             Mutability::Mutable => hir::MutMutable,
 388             Mutability::Immutable => hir::MutImmutable,
 389         }
 390     }
 391
 392     fn lower_arg(&mut self, arg: &Arg) -> hir::Arg {
 393         hir::Arg {
 394             id: arg.id,
 395             pat: self.lower_pat(&arg.pat),
 396             ty: self.lower_ty(&arg.ty),
 397         }
 398     }
 399
 400     fn lower_fn_decl(&mut self, decl: &FnDecl) -> P<hir::FnDecl> {
 401         P(hir::FnDecl {
 402             inputs: decl.inputs.iter().map(|x| self.lower_arg(x)).collect(),
 403             output: match decl.output {
 404                 FunctionRetTy::Ty(ref ty) => hir::Return(self.lower_ty(ty)),
 405                 FunctionRetTy::Default(span) => hir::DefaultReturn(span),
 406             },
 407             variadic: decl.variadic,
 408         })
 409     }
 410
 411     fn lower_ty_param_bound(&mut self, tpb: &TyParamBound) -> hir::TyParamBound {
 412         match *tpb {
 413             TraitTyParamBound(ref ty, modifier) => {
 414                 hir::TraitTyParamBound(self.lower_poly_trait_ref(ty),
 415                                        self.lower_trait_bound_modifier(modifier))
 416             }
 417             RegionTyParamBound(ref lifetime) => {
 418                 hir::RegionTyParamBound(self.lower_lifetime(lifetime))
 419             }
 420         }
 421     }
 422
 423     fn lower_ty_param(&mut self, tp: &TyParam) -> hir::TyParam {
 424         hir::TyParam {
 425             id: tp.id,
 426             name: tp.ident.name,
 427             bounds: self.lower_bounds(&tp.bounds),
 428             default: tp.default.as_ref().map(|x| self.lower_ty(x)),
 429             span: tp.span,
 430         }
 431     }
 432
 433     fn lower_ty_params(&mut self, tps: &P<[TyParam]>) -> hir::HirVec<hir::TyParam> {
 434         tps.iter().map(|tp| self.lower_ty_param(tp)).collect()
 435     }
 436
 437     fn lower_lifetime(&mut self, l: &Lifetime) -> hir::Lifetime {
 438         hir::Lifetime {
 439             id: l.id,
 440             name: l.name,
 441             span: l.span,
 442         }
 443     }
 444
 445     fn lower_lifetime_def(&mut self, l: &LifetimeDef) -> hir::LifetimeDef {
 446         hir::LifetimeDef {
 447             lifetime: self.lower_lifetime(&l.lifetime),
 448             bounds: self.lower_lifetimes(&l.bounds),
 449         }
 450     }
 451
 452     fn lower_lifetimes(&mut self, lts: &Vec<Lifetime>) -> hir::HirVec<hir::Lifetime> {
 453         lts.iter().map(|l| self.lower_lifetime(l)).collect()
 454     }
 455
 456     fn lower_lifetime_defs(&mut self, lts: &Vec<LifetimeDef>) -> hir::HirVec<hir::LifetimeDef> {
 457         lts.iter().map(|l| self.lower_lifetime_def(l)).collect()
 458     }
 459
 460     fn lower_opt_lifetime(&mut self, o_lt: &Option<Lifetime>) -> Option<hir::Lifetime> {
 461         o_lt.as_ref().map(|lt| self.lower_lifetime(lt))
 462     }
 463
 464     fn lower_generics(&mut self, g: &Generics) -> hir::Generics {
 465         hir::Generics {
 466             ty_params: self.lower_ty_params(&g.ty_params),
 467             lifetimes: self.lower_lifetime_defs(&g.lifetimes),
 468             where_clause: self.lower_where_clause(&g.where_clause),
 469         }
 470     }
 471
 472     fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause {
 473         hir::WhereClause {
 474             id: wc.id,
 475             predicates: wc.predicates
 476                           .iter()
 477                           .map(|predicate| self.lower_where_predicate(predicate))
 478                           .collect(),
 479         }
 480     }
 481
 482     fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate {
 483         match *pred {
 484             WherePredicate::BoundPredicate(WhereBoundPredicate{ ref bound_lifetimes,
 485                                                                 ref bounded_ty,
 486                                                                 ref bounds,
 487                                                                 span}) => {
 488                 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
 489                     bound_lifetimes: self.lower_lifetime_defs(bound_lifetimes),
 490                     bounded_ty: self.lower_ty(bounded_ty),
 491                     bounds: bounds.iter().map(|x| self.lower_ty_param_bound(x)).collect(),
 492                     span: span,
 493                 })
 494             }
 495             WherePredicate::RegionPredicate(WhereRegionPredicate{ ref lifetime,
 496                                                                   ref bounds,
 497                                                                   span}) => {
 498                 hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
 499                     span: span,
 500                     lifetime: self.lower_lifetime(lifetime),
 501                     bounds: bounds.iter().map(|bound| self.lower_lifetime(bound)).collect(),
 502                 })
 503             }
 504             WherePredicate::EqPredicate(WhereEqPredicate{ id,
 505                                                           ref path,
 506                                                           ref ty,
 507                                                           span}) => {
 508                 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
 509                     id: id,
 510                     path: self.lower_path(path),
 511                     ty: self.lower_ty(ty),
 512                     span: span,
 513                 })
 514             }
 515         }
 516     }
 517
 518     fn lower_variant_data(&mut self, vdata: &VariantData) -> hir::VariantData {
 519         match *vdata {
 520             VariantData::Struct(ref fields, id) => {
 521                 hir::VariantData::Struct(fields.iter()
 522                                                .enumerate()
 523                                                .map(|f| self.lower_struct_field(f))
 524                                                .collect(),
 525                                          id)
 526             }
 527             VariantData::Tuple(ref fields, id) => {
 528                 hir::VariantData::Tuple(fields.iter()
 529                                               .enumerate()
 530                                               .map(|f| self.lower_struct_field(f))
 531                                               .collect(),
 532                                         id)
 533             }
 534             VariantData::Unit(id) => hir::VariantData::Unit(id),
 535         }
 536     }
 537
 538     fn lower_trait_ref(&mut self, p: &TraitRef) -> hir::TraitRef {
 539         hir::TraitRef {
 540             path: self.lower_path(&p.path),
 541             ref_id: p.ref_id,
 542         }
 543     }
 544
 545     fn lower_poly_trait_ref(&mut self, p: &PolyTraitRef) -> hir::PolyTraitRef {
 546         hir::PolyTraitRef {
 547             bound_lifetimes: self.lower_lifetime_defs(&p.bound_lifetimes),
 548             trait_ref: self.lower_trait_ref(&p.trait_ref),
 549             span: p.span,
 550         }
 551     }
 552
 553     fn lower_struct_field(&mut self, (index, f): (usize, &StructField)) -> hir::StructField {
 554         hir::StructField {
 555             span: f.span,
 556             id: f.id,
 557             name: f.ident.map(|ident| ident.name).unwrap_or(token::intern(&index.to_string())),
 558             vis: self.lower_visibility(&f.vis),
 559             ty: self.lower_ty(&f.ty),
 560             attrs: self.lower_attrs(&f.attrs),
 561         }
 562     }
 563
 564     fn lower_field(&mut self, f: &Field) -> hir::Field {
 565         hir::Field {
 566             name: respan(f.ident.span, f.ident.node.name),
 567             expr: self.lower_expr(&f.expr),
 568             span: f.span,
 569         }
 570     }
 571
 572     fn lower_mt(&mut self, mt: &MutTy) -> hir::MutTy {
 573         hir::MutTy {
 574             ty: self.lower_ty(&mt.ty),
 575             mutbl: self.lower_mutability(mt.mutbl),
 576         }
 577     }
 578
 579     fn lower_bounds(&mut self, bounds: &TyParamBounds) -> hir::TyParamBounds {
 580         bounds.iter().map(|bound| self.lower_ty_param_bound(bound)).collect()
 581     }
 582
 583     fn lower_block(&mut self, b: &Block) -> P<hir::Block> {
 584         let mut stmts = Vec::new();
 585         let mut expr = None;
 586
 587         if let Some((last, rest)) = b.stmts.split_last() {
 588             stmts = rest.iter().map(|s| self.lower_stmt(s)).collect::<Vec<_>>();
 589             let last = self.lower_stmt(last);
 590             if let hir::StmtExpr(e, _) = last.node {
 591                 expr = Some(e);
 592             } else {
 593                 stmts.push(last);
 594             }
 595         }
 596
 597         P(hir::Block {
 598             id: b.id,
 599             stmts: stmts.into(),
 600             expr: expr,
 601             rules: self.lower_block_check_mode(&b.rules),
 602             span: b.span,
 603         })
 604     }
 605
 606     fn lower_item_kind(&mut self, i: &ItemKind) -> hir::Item_ {
 607         match *i {
 608             ItemKind::ExternCrate(string) => hir::ItemExternCrate(string),
 609             ItemKind::Use(ref view_path) => {
 610                 hir::ItemUse(self.lower_view_path(view_path))
 611             }
 612             ItemKind::Static(ref t, m, ref e) => {
 613                 hir::ItemStatic(self.lower_ty(t),
 614                                 self.lower_mutability(m),
 615                                 self.lower_expr(e))
 616             }
 617             ItemKind::Const(ref t, ref e) => {
 618                 hir::ItemConst(self.lower_ty(t), self.lower_expr(e))
 619             }
 620             ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 621                 hir::ItemFn(self.lower_fn_decl(decl),
 622                             self.lower_unsafety(unsafety),
 623                             self.lower_constness(constness),
 624                             abi,
 625                             self.lower_generics(generics),
 626                             self.lower_block(body))
 627             }
 628             ItemKind::Mod(ref m) => hir::ItemMod(self.lower_mod(m)),
 629             ItemKind::ForeignMod(ref nm) => hir::ItemForeignMod(self.lower_foreign_mod(nm)),
 630             ItemKind::Ty(ref t, ref generics) => {
 631                 hir::ItemTy(self.lower_ty(t), self.lower_generics(generics))
 632             }
 633             ItemKind::Enum(ref enum_definition, ref generics) => {
 634                 hir::ItemEnum(hir::EnumDef {
 635                                   variants: enum_definition.variants
 636                                                            .iter()
 637                                                            .map(|x| self.lower_variant(x))
 638                                                            .collect(),
 639                               },
 640                               self.lower_generics(generics))
 641             }
 642             ItemKind::Struct(ref struct_def, ref generics) => {
 643                 let struct_def = self.lower_variant_data(struct_def);
 644                 hir::ItemStruct(struct_def, self.lower_generics(generics))
 645             }
 646             ItemKind::DefaultImpl(unsafety, ref trait_ref) => {
 647                 hir::ItemDefaultImpl(self.lower_unsafety(unsafety),
 648                                      self.lower_trait_ref(trait_ref))
 649             }
 650             ItemKind::Impl(unsafety, polarity, ref generics, ref ifce, ref ty, ref impl_items) => {
 651                 let new_impl_items = impl_items.iter()
 652                                                .map(|item| self.lower_impl_item(item))
 653                                                .collect();
 654                 let ifce = ifce.as_ref().map(|trait_ref| self.lower_trait_ref(trait_ref));
 655                 hir::ItemImpl(self.lower_unsafety(unsafety),
 656                               self.lower_impl_polarity(polarity),
 657                               self.lower_generics(generics),
 658                               ifce,
 659                               self.lower_ty(ty),
 660                               new_impl_items)
 661             }
 662             ItemKind::Trait(unsafety, ref generics, ref bounds, ref items) => {
 663                 let bounds = self.lower_bounds(bounds);
 664                 let items = items.iter().map(|item| self.lower_trait_item(item)).collect();
 665                 hir::ItemTrait(self.lower_unsafety(unsafety),
 666                                self.lower_generics(generics),
 667                                bounds,
 668                                items)
 669             }
 670             ItemKind::Mac(_) => panic!("Shouldn't still be around"),
 671         }
 672     }
 673
 674     fn lower_trait_item(&mut self, i: &TraitItem) -> hir::TraitItem {
 675         self.with_parent_def(i.id, |this| {
 676             hir::TraitItem {
 677                 id: i.id,
 678                 name: i.ident.name,
 679                 attrs: this.lower_attrs(&i.attrs),
 680                 node: match i.node {
 681                     TraitItemKind::Const(ref ty, ref default) => {
 682                         hir::ConstTraitItem(this.lower_ty(ty),
 683                                             default.as_ref().map(|x| this.lower_expr(x)))
 684                     }
 685                     TraitItemKind::Method(ref sig, ref body) => {
 686                         hir::MethodTraitItem(this.lower_method_sig(sig),
 687                                              body.as_ref().map(|x| this.lower_block(x)))
 688                     }
 689                     TraitItemKind::Type(ref bounds, ref default) => {
 690                         hir::TypeTraitItem(this.lower_bounds(bounds),
 691                                            default.as_ref().map(|x| this.lower_ty(x)))
 692                     }
 693                     TraitItemKind::Macro(..) => panic!("Shouldn't exist any more"),
 694                 },
 695                 span: i.span,
 696             }
 697         })
 698     }
 699
 700     fn lower_impl_item(&mut self, i: &ImplItem) -> hir::ImplItem {
 701         self.with_parent_def(i.id, |this| {
 702             hir::ImplItem {
 703                 id: i.id,
 704                 name: i.ident.name,
 705                 attrs: this.lower_attrs(&i.attrs),
 706                 vis: this.lower_visibility(&i.vis),
 707                 defaultness: this.lower_defaultness(i.defaultness),
 708                 node: match i.node {
 709                     ImplItemKind::Const(ref ty, ref expr) => {
 710                         hir::ImplItemKind::Const(this.lower_ty(ty), this.lower_expr(expr))
 711                     }
 712                     ImplItemKind::Method(ref sig, ref body) => {
 713                         hir::ImplItemKind::Method(this.lower_method_sig(sig),
 714                                                   this.lower_block(body))
 715                     }
 716                     ImplItemKind::Type(ref ty) => hir::ImplItemKind::Type(this.lower_ty(ty)),
 717                     ImplItemKind::Macro(..) => panic!("Shouldn't exist any more"),
 718                 },
 719                 span: i.span,
 720             }
 721         })
 722     }
 723
 724     fn lower_mod(&mut self, m: &Mod) -> hir::Mod {
 725         hir::Mod {
 726             inner: m.inner,
 727             item_ids: m.items.iter().map(|x| self.lower_item_id(x)).collect(),
 728         }
 729     }
 730
 731     fn lower_macro_def(&mut self, m: &MacroDef) -> hir::MacroDef {
 732         hir::MacroDef {
 733             name: m.ident.name,
 734             attrs: self.lower_attrs(&m.attrs),
 735             id: m.id,
 736             span: m.span,
 737             imported_from: m.imported_from.map(|x| x.name),
 738             export: m.export,
 739             use_locally: m.use_locally,
 740             allow_internal_unstable: m.allow_internal_unstable,
 741             body: m.body.clone().into(),
 742         }
 743     }
 744
 745     fn lower_item_id(&mut self, i: &Item) -> hir::ItemId {
 746         hir::ItemId { id: i.id }
 747     }
 748
 749     pub fn lower_item(&mut self, i: &Item) -> hir::Item {
 750         let node = self.with_parent_def(i.id, |this| {
 751             this.lower_item_kind(&i.node)
 752         });
 753
 754         hir::Item {
 755             id: i.id,
 756             name: i.ident.name,
 757             attrs: self.lower_attrs(&i.attrs),
 758             node: node,
 759             vis: self.lower_visibility(&i.vis),
 760             span: i.span,
 761         }
 762     }
 763
 764     fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem {
 765         self.with_parent_def(i.id, |this| {
 766             hir::ForeignItem {
 767                 id: i.id,
 768                 name: i.ident.name,
 769                 attrs: this.lower_attrs(&i.attrs),
 770                 node: match i.node {
 771                     ForeignItemKind::Fn(ref fdec, ref generics) => {
 772                         hir::ForeignItemFn(this.lower_fn_decl(fdec), this.lower_generics(generics))
 773                     }
 774                     ForeignItemKind::Static(ref t, m) => {
 775                         hir::ForeignItemStatic(this.lower_ty(t), m)
 776                     }
 777                 },
 778                 vis: this.lower_visibility(&i.vis),
 779                 span: i.span,
 780             }
 781         })
 782     }
 783
 784     fn lower_method_sig(&mut self, sig: &MethodSig) -> hir::MethodSig {
 785         let hir_sig = hir::MethodSig {
 786             generics: self.lower_generics(&sig.generics),
 787             abi: sig.abi,
 788             unsafety: self.lower_unsafety(sig.unsafety),
 789             constness: self.lower_constness(sig.constness),
 790             decl: self.lower_fn_decl(&sig.decl),
 791         };
 792         // Check for `self: _` and `self: &_`
 793         if let Some(SelfKind::Explicit(..)) = sig.decl.get_self().map(|eself| eself.node) {
 794             match hir_sig.decl.get_self().map(|eself| eself.node) {
 795                 Some(hir::SelfKind::Value(..)) | Some(hir::SelfKind::Region(..)) => {
 796                     self.diagnostic().span_err(sig.decl.inputs[0].ty.span,
 797                         "the type placeholder `_` is not allowed within types on item signatures");
 798                 }
 799                 _ => {}
 800             }
 801         }
 802         hir_sig
 803     }
 804
 805     fn lower_unsafety(&mut self, u: Unsafety) -> hir::Unsafety {
 806         match u {
 807             Unsafety::Unsafe => hir::Unsafety::Unsafe,
 808             Unsafety::Normal => hir::Unsafety::Normal,
 809         }
 810     }
 811
 812     fn lower_constness(&mut self, c: Constness) -> hir::Constness {
 813         match c {
 814             Constness::Const => hir::Constness::Const,
 815             Constness::NotConst => hir::Constness::NotConst,
 816         }
 817     }
 818
 819     fn lower_unop(&mut self, u: UnOp) -> hir::UnOp {
 820         match u {
 821             UnOp::Deref => hir::UnDeref,
 822             UnOp::Not => hir::UnNot,
 823             UnOp::Neg => hir::UnNeg,
 824         }
 825     }
 826
 827     fn lower_binop(&mut self, b: BinOp) -> hir::BinOp {
 828         Spanned {
 829             node: match b.node {
 830                 BinOpKind::Add => hir::BiAdd,
 831                 BinOpKind::Sub => hir::BiSub,
 832                 BinOpKind::Mul => hir::BiMul,
 833                 BinOpKind::Div => hir::BiDiv,
 834                 BinOpKind::Rem => hir::BiRem,
 835                 BinOpKind::And => hir::BiAnd,
 836                 BinOpKind::Or => hir::BiOr,
 837                 BinOpKind::BitXor => hir::BiBitXor,
 838                 BinOpKind::BitAnd => hir::BiBitAnd,
 839                 BinOpKind::BitOr => hir::BiBitOr,
 840                 BinOpKind::Shl => hir::BiShl,
 841                 BinOpKind::Shr => hir::BiShr,
 842                 BinOpKind::Eq => hir::BiEq,
 843                 BinOpKind::Lt => hir::BiLt,
 844                 BinOpKind::Le => hir::BiLe,
 845                 BinOpKind::Ne => hir::BiNe,
 846                 BinOpKind::Ge => hir::BiGe,
 847                 BinOpKind::Gt => hir::BiGt,
 848             },
 849             span: b.span,
 850         }
 851     }
 852
 853     fn lower_pat(&mut self, p: &Pat) -> P<hir::Pat> {
 854         P(hir::Pat {
 855             id: p.id,
 856             node: match p.node {
 857                 PatKind::Wild => hir::PatKind::Wild,
 858                 PatKind::Ident(ref binding_mode, pth1, ref sub) => {
 859                     self.with_parent_def(p.id, |this| {
 860                         match this.resolver.get_resolution(p.id).map(|d| d.base_def) {
 861                             // `None` can occur in body-less function signatures
 862                             None | Some(Def::Local(..)) => {
 863                                 hir::PatKind::Binding(this.lower_binding_mode(binding_mode),
 864                                                       respan(pth1.span, pth1.node.name),
 865                                                       sub.as_ref().map(|x| this.lower_pat(x)))
 866                             }
 867                             _ => hir::PatKind::Path(None, hir::Path::from_name(pth1.span,
 868                                                                                pth1.node.name))
 869                         }
 870                     })
 871                 }
 872                 PatKind::Lit(ref e) => hir::PatKind::Lit(self.lower_expr(e)),
 873                 PatKind::TupleStruct(ref pth, ref pats, ddpos) => {
 874                     hir::PatKind::TupleStruct(self.lower_path(pth),
 875                                               pats.iter().map(|x| self.lower_pat(x)).collect(),
 876                                               ddpos)
 877                 }
 878                 PatKind::Path(ref opt_qself, ref path) => {
 879                     let opt_qself = opt_qself.as_ref().map(|qself| {
 880                         hir::QSelf { ty: self.lower_ty(&qself.ty), position: qself.position }
 881                     });
 882                     hir::PatKind::Path(opt_qself, self.lower_path(path))
 883                 }
 884                 PatKind::Struct(ref pth, ref fields, etc) => {
 885                     let pth = self.lower_path(pth);
 886                     let fs = fields.iter()
 887                                    .map(|f| {
 888                                        Spanned {
 889                                            span: f.span,
 890                                            node: hir::FieldPat {
 891                                                name: f.node.ident.name,
 892                                                pat: self.lower_pat(&f.node.pat),
 893                                                is_shorthand: f.node.is_shorthand,
 894                                            },
 895                                        }
 896                                    })
 897                                    .collect();
 898                     hir::PatKind::Struct(pth, fs, etc)
 899                 }
 900                 PatKind::Tuple(ref elts, ddpos) => {
 901                     hir::PatKind::Tuple(elts.iter().map(|x| self.lower_pat(x)).collect(), ddpos)
 902                 }
 903                 PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)),
 904                 PatKind::Ref(ref inner, mutbl) => {
 905                     hir::PatKind::Ref(self.lower_pat(inner), self.lower_mutability(mutbl))
 906                 }
 907                 PatKind::Range(ref e1, ref e2) => {
 908                     hir::PatKind::Range(self.lower_expr(e1), self.lower_expr(e2))
 909                 }
 910                 PatKind::Vec(ref before, ref slice, ref after) => {
 911                     hir::PatKind::Vec(before.iter().map(|x| self.lower_pat(x)).collect(),
 912                                 slice.as_ref().map(|x| self.lower_pat(x)),
 913                                 after.iter().map(|x| self.lower_pat(x)).collect())
 914                 }
 915                 PatKind::Mac(_) => panic!("Shouldn't exist here"),
 916             },
 917             span: p.span,
 918         })
 919     }
 920
 921     fn lower_expr(&mut self, e: &Expr) -> P<hir::Expr> {
 922         P(hir::Expr {
 923             id: e.id,
 924             node: match e.node {
 925                 // Issue #22181:
 926                 // Eventually a desugaring for `box EXPR`
 927                 // (similar to the desugaring above for `in PLACE BLOCK`)
 928                 // should go here, desugaring
 929                 //
 930                 // to:
 931                 //
 932                 // let mut place = BoxPlace::make_place();
 933                 // let raw_place = Place::pointer(&mut place);
 934                 // let value = $value;
 935                 // unsafe {
 936                 //     ::std::ptr::write(raw_place, value);
 937                 //     Boxed::finalize(place)
 938                 // }
 939                 //
 940                 // But for now there are type-inference issues doing that.
 941                 ExprKind::Box(ref e) => {
 942                     hir::ExprBox(self.lower_expr(e))
 943                 }
 944
 945                 // Desugar ExprBox: `in (PLACE) EXPR`
 946                 ExprKind::InPlace(ref placer, ref value_expr) => {
 947                     // to:
 948                     //
 949                     // let p = PLACE;
 950                     // let mut place = Placer::make_place(p);
 951                     // let raw_place = Place::pointer(&mut place);
 952                     // push_unsafe!({
 953                     //     std::intrinsics::move_val_init(raw_place, pop_unsafe!( EXPR ));
 954                     //     InPlace::finalize(place)
 955                     // })
 956                     let placer_expr = self.lower_expr(placer);
 957                     let value_expr = self.lower_expr(value_expr);
 958
 959                     let placer_ident = self.str_to_ident("placer");
 960                     let place_ident = self.str_to_ident("place");
 961                     let p_ptr_ident = self.str_to_ident("p_ptr");
 962
 963                     let make_place = ["ops", "Placer", "make_place"];
 964                     let place_pointer = ["ops", "Place", "pointer"];
 965                     let move_val_init = ["intrinsics", "move_val_init"];
 966                     let inplace_finalize = ["ops", "InPlace", "finalize"];
 967
 968                     let make_call = |this: &mut LoweringContext, p, args| {
 969                         let path = this.std_path(e.span, p);
 970                         let path = this.expr_path(path, ThinVec::new());
 971                         this.expr_call(e.span, path, args)
 972                     };
 973
 974                     let mk_stmt_let = |this: &mut LoweringContext, bind, expr| {
 975                         this.stmt_let(e.span, false, bind, expr)
 976                     };
 977
 978                     let mk_stmt_let_mut = |this: &mut LoweringContext, bind, expr| {
 979                         this.stmt_let(e.span, true, bind, expr)
 980                     };
 981
 982                     // let placer = <placer_expr> ;
 983                     let (s1, placer_binding) = {
 984                         let placer_expr = self.signal_block_expr(hir_vec![],
 985                                                                  placer_expr,
 986                                                                  e.span,
 987                                                                  hir::PopUnstableBlock,
 988                                                                  ThinVec::new());
 989                         mk_stmt_let(self, placer_ident, placer_expr)
 990                     };
 991
 992                     // let mut place = Placer::make_place(placer);
 993                     let (s2, place_binding) = {
 994                         let placer = self.expr_ident(e.span, placer_ident, placer_binding);
 995                         let call = make_call(self, &make_place, hir_vec![placer]);
 996                         mk_stmt_let_mut(self, place_ident, call)
 997                     };
 998
 999                     // let p_ptr = Place::pointer(&mut place);
1000                     let (s3, p_ptr_binding) = {
1001                         let agent = self.expr_ident(e.span, place_ident, place_binding);
1002                         let args = hir_vec![self.expr_mut_addr_of(e.span, agent)];
1003                         let call = make_call(self, &place_pointer, args);
1004                         mk_stmt_let(self, p_ptr_ident, call)
1005                     };
1006
1007                     // pop_unsafe!(EXPR));
1008                     let pop_unsafe_expr = {
1009                         let value_expr = self.signal_block_expr(hir_vec![],
1010                                                                 value_expr,
1011                                                                 e.span,
1012                                                                 hir::PopUnstableBlock,
1013                                                                 ThinVec::new());
1014                         self.signal_block_expr(hir_vec![],
1015                                                value_expr,
1016                                                e.span,
1017                                                hir::PopUnsafeBlock(hir::CompilerGenerated),
1018                                                ThinVec::new())
1019                     };
1020
1021                     // push_unsafe!({
1022                     //     std::intrinsics::move_val_init(raw_place, pop_unsafe!( EXPR ));
1023                     //     InPlace::finalize(place)
1024                     // })
1025                     let expr = {
1026                         let ptr = self.expr_ident(e.span, p_ptr_ident, p_ptr_binding);
1027                         let call_move_val_init =
1028                             hir::StmtSemi(
1029                                 make_call(self, &move_val_init, hir_vec![ptr, pop_unsafe_expr]),
1030                                 self.next_id());
1031                         let call_move_val_init = respan(e.span, call_move_val_init);
1032
1033                         let place = self.expr_ident(e.span, place_ident, place_binding);
1034                         let call = make_call(self, &inplace_finalize, hir_vec![place]);
1035                         self.signal_block_expr(hir_vec![call_move_val_init],
1036                                                call,
1037                                                e.span,
1038                                                hir::PushUnsafeBlock(hir::CompilerGenerated),
1039                                                ThinVec::new())
1040                     };
1041
1042                     return self.signal_block_expr(hir_vec![s1, s2, s3],
1043                                                   expr,
1044                                                   e.span,
1045                                                   hir::PushUnstableBlock,
1046                                                   e.attrs.clone());
1047                 }
1048
1049                 ExprKind::Vec(ref exprs) => {
1050                     hir::ExprVec(exprs.iter().map(|x| self.lower_expr(x)).collect())
1051                 }
1052                 ExprKind::Repeat(ref expr, ref count) => {
1053                     let expr = self.lower_expr(expr);
1054                     let count = self.lower_expr(count);
1055                     hir::ExprRepeat(expr, count)
1056                 }
1057                 ExprKind::Tup(ref elts) => {
1058                     hir::ExprTup(elts.iter().map(|x| self.lower_expr(x)).collect())
1059                 }
1060                 ExprKind::Call(ref f, ref args) => {
1061                     let f = self.lower_expr(f);
1062                     hir::ExprCall(f, args.iter().map(|x| self.lower_expr(x)).collect())
1063                 }
1064                 ExprKind::MethodCall(i, ref tps, ref args) => {
1065                     let tps = tps.iter().map(|x| self.lower_ty(x)).collect();
1066                     let args = args.iter().map(|x| self.lower_expr(x)).collect();
1067                     hir::ExprMethodCall(respan(i.span, i.node.name), tps, args)
1068                 }
1069                 ExprKind::Binary(binop, ref lhs, ref rhs) => {
1070                     let binop = self.lower_binop(binop);
1071                     let lhs = self.lower_expr(lhs);
1072                     let rhs = self.lower_expr(rhs);
1073                     hir::ExprBinary(binop, lhs, rhs)
1074                 }
1075                 ExprKind::Unary(op, ref ohs) => {
1076                     let op = self.lower_unop(op);
1077                     let ohs = self.lower_expr(ohs);
1078                     hir::ExprUnary(op, ohs)
1079                 }
1080                 ExprKind::Lit(ref l) => hir::ExprLit(P((**l).clone())),
1081                 ExprKind::Cast(ref expr, ref ty) => {
1082                     let expr = self.lower_expr(expr);
1083                     hir::ExprCast(expr, self.lower_ty(ty))
1084                 }
1085                 ExprKind::Type(ref expr, ref ty) => {
1086                     let expr = self.lower_expr(expr);
1087                     hir::ExprType(expr, self.lower_ty(ty))
1088                 }
1089                 ExprKind::AddrOf(m, ref ohs) => {
1090                     let m = self.lower_mutability(m);
1091                     let ohs = self.lower_expr(ohs);
1092                     hir::ExprAddrOf(m, ohs)
1093                 }
1094                 // More complicated than you might expect because the else branch
1095                 // might be `if let`.
1096                 ExprKind::If(ref cond, ref blk, ref else_opt) => {
1097                     let else_opt = else_opt.as_ref().map(|els| {
1098                         match els.node {
1099                             ExprKind::IfLet(..) => {
1100                                 // wrap the if-let expr in a block
1101                                 let span = els.span;
1102                                 let els = self.lower_expr(els);
1103                                 let id = self.next_id();
1104                                 let blk = P(hir::Block {
1105                                     stmts: hir_vec![],
1106                                     expr: Some(els),
1107                                     id: id,
1108                                     rules: hir::DefaultBlock,
1109                                     span: span,
1110                                 });
1111                                 self.expr_block(blk, ThinVec::new())
1112                             }
1113                             _ => self.lower_expr(els),
1114                         }
1115                     });
1116
1117                     hir::ExprIf(self.lower_expr(cond), self.lower_block(blk), else_opt)
1118                 }
1119                 ExprKind::While(ref cond, ref body, opt_ident) => {
1120                     hir::ExprWhile(self.lower_expr(cond), self.lower_block(body),
1121                                    self.lower_opt_sp_ident(opt_ident))
1122                 }
1123                 ExprKind::Loop(ref body, opt_ident) => {
1124                     hir::ExprLoop(self.lower_block(body), self.lower_opt_sp_ident(opt_ident))
1125                 }
1126                 ExprKind::Match(ref expr, ref arms) => {
1127                     hir::ExprMatch(self.lower_expr(expr),
1128                                    arms.iter().map(|x| self.lower_arm(x)).collect(),
1129                                    hir::MatchSource::Normal)
1130                 }
1131                 ExprKind::Closure(capture_clause, ref decl, ref body, fn_decl_span) => {
1132                     self.with_parent_def(e.id, |this| {
1133                         hir::ExprClosure(this.lower_capture_clause(capture_clause),
1134                                          this.lower_fn_decl(decl),
1135                                          this.lower_block(body),
1136                                          fn_decl_span)
1137                     })
1138                 }
1139                 ExprKind::Block(ref blk) => hir::ExprBlock(self.lower_block(blk)),
1140                 ExprKind::Assign(ref el, ref er) => {
1141                     hir::ExprAssign(self.lower_expr(el), self.lower_expr(er))
1142                 }
1143                 ExprKind::AssignOp(op, ref el, ref er) => {
1144                     hir::ExprAssignOp(self.lower_binop(op),
1145                                       self.lower_expr(el),
1146                                       self.lower_expr(er))
1147                 }
1148                 ExprKind::Field(ref el, ident) => {
1149                     hir::ExprField(self.lower_expr(el), respan(ident.span, ident.node.name))
1150                 }
1151                 ExprKind::TupField(ref el, ident) => {
1152                     hir::ExprTupField(self.lower_expr(el), ident)
1153                 }
1154                 ExprKind::Index(ref el, ref er) => {
1155                     hir::ExprIndex(self.lower_expr(el), self.lower_expr(er))
1156                 }
1157                 ExprKind::Range(ref e1, ref e2, lims) => {
1158                     fn make_struct(this: &mut LoweringContext,
1159                                    ast_expr: &Expr,
1160                                    path: &[&str],
1161                                    fields: &[(&str, &P<Expr>)]) -> P<hir::Expr> {
1162                         let struct_path = this.std_path(ast_expr.span,
1163                                                         &iter::once(&"ops").chain(path)
1164                                                                            .map(|s| *s)
1165                                                                            .collect::<Vec<_>>());
1166
1167                         let hir_expr = if fields.len() == 0 {
1168                             this.expr_path(struct_path, ast_expr.attrs.clone())
1169                         } else {
1170                             let fields = fields.into_iter().map(|&(s, e)| {
1171                                 let expr = this.lower_expr(&e);
1172                                 let signal_block = this.signal_block_expr(hir_vec![],
1173                                                                           expr,
1174                                                                           e.span,
1175                                                                           hir::PopUnstableBlock,
1176                                                                           ThinVec::new());
1177                                 this.field(token::intern(s), signal_block, ast_expr.span)
1178                             }).collect();
1179                             let attrs = ast_expr.attrs.clone();
1180
1181                             this.expr_struct(ast_expr.span, struct_path, fields, None, attrs)
1182                         };
1183
1184                         this.signal_block_expr(hir_vec![],
1185                                                hir_expr,
1186                                                ast_expr.span,
1187                                                hir::PushUnstableBlock,
1188                                                ThinVec::new())
1189                     }
1190
1191                     use syntax::ast::RangeLimits::*;
1192
1193                     return match (e1, e2, lims) {
1194                         (&None,         &None,         HalfOpen) =>
1195                             make_struct(self, e, &["RangeFull"], &[]),
1196
1197                         (&Some(ref e1), &None,         HalfOpen) =>
1198                             make_struct(self, e, &["RangeFrom"],
1199                                                  &[("start", e1)]),
1200
1201                         (&None,         &Some(ref e2), HalfOpen) =>
1202                             make_struct(self, e, &["RangeTo"],
1203                                                  &[("end", e2)]),
1204
1205                         (&Some(ref e1), &Some(ref e2), HalfOpen) =>
1206                             make_struct(self, e, &["Range"],
1207                                                  &[("start", e1), ("end", e2)]),
1208
1209                         (&None,         &Some(ref e2), Closed)   =>
1210                             make_struct(self, e, &["RangeToInclusive"],
1211                                                  &[("end", e2)]),
1212
1213                         (&Some(ref e1), &Some(ref e2), Closed)   =>
1214                             make_struct(self, e, &["RangeInclusive", "NonEmpty"],
1215                                                  &[("start", e1), ("end", e2)]),
1216
1217                         _ => panic!(self.diagnostic()
1218                                         .span_fatal(e.span, "inclusive range with no end")),
1219                     };
1220                 }
1221                 ExprKind::Path(ref qself, ref path) => {
1222                     let hir_qself = qself.as_ref().map(|&QSelf { ref ty, position }| {
1223                         hir::QSelf {
1224                             ty: self.lower_ty(ty),
1225                             position: position,
1226                         }
1227                     });
1228                     hir::ExprPath(hir_qself, self.lower_path(path))
1229                 }
1230                 ExprKind::Break(opt_ident) => hir::ExprBreak(self.lower_opt_sp_ident(opt_ident)),
1231                 ExprKind::Continue(opt_ident) => hir::ExprAgain(self.lower_opt_sp_ident(opt_ident)),
1232                 ExprKind::Ret(ref e) => hir::ExprRet(e.as_ref().map(|x| self.lower_expr(x))),
1233                 ExprKind::InlineAsm(InlineAsm {
1234                         ref inputs,
1235                         ref outputs,
1236                         ref asm,
1237                         asm_str_style,
1238                         ref clobbers,
1239                         volatile,
1240                         alignstack,
1241                         dialect,
1242                         expn_id,
1243                     }) => hir::ExprInlineAsm(hir::InlineAsm {
1244                     inputs: inputs.iter().map(|&(ref c, _)| c.clone()).collect(),
1245                     outputs: outputs.iter()
1246                                     .map(|out| {
1247                                         hir::InlineAsmOutput {
1248                                             constraint: out.constraint.clone(),
1249                                             is_rw: out.is_rw,
1250                                             is_indirect: out.is_indirect,
1251                                         }
1252                                     })
1253                                     .collect(),
1254                     asm: asm.clone(),
1255                     asm_str_style: asm_str_style,
1256                     clobbers: clobbers.clone().into(),
1257                     volatile: volatile,
1258                     alignstack: alignstack,
1259                     dialect: dialect,
1260                     expn_id: expn_id,
1261                 }, outputs.iter().map(|out| self.lower_expr(&out.expr)).collect(),
1262                    inputs.iter().map(|&(_, ref input)| self.lower_expr(input)).collect()),
1263                 ExprKind::Struct(ref path, ref fields, ref maybe_expr) => {
1264                     hir::ExprStruct(self.lower_path(path),
1265                                     fields.iter().map(|x| self.lower_field(x)).collect(),
1266                                     maybe_expr.as_ref().map(|x| self.lower_expr(x)))
1267                 }
1268                 ExprKind::Paren(ref ex) => {
1269                     return self.lower_expr(ex).map(|mut ex| {
1270                         // include parens in span, but only if it is a super-span.
1271                         if e.span.contains(ex.span) {
1272                             ex.span = e.span;
1273                         }
1274                         // merge attributes into the inner expression.
1275                         let mut attrs = e.attrs.clone();
1276                         attrs.extend::<Vec<_>>(ex.attrs.into());
1277                         ex.attrs = attrs;
1278                         ex
1279                     });
1280                 }
1281
1282                 // Desugar ExprIfLet
1283                 // From: `if let <pat> = <sub_expr> <body> [<else_opt>]`
1284                 ExprKind::IfLet(ref pat, ref sub_expr, ref body, ref else_opt) => {
1285                     // to:
1286                     //
1287                     //   match <sub_expr> {
1288                     //     <pat> => <body>,
1289                     //     [_ if <else_opt_if_cond> => <else_opt_if_body>,]
1290                     //     _ => [<else_opt> | ()]
1291                     //   }
1292
1293                     // `<pat> => <body>`
1294                     let pat_arm = {
1295                         let body = self.lower_block(body);
1296                         let body_expr = self.expr_block(body, ThinVec::new());
1297                         let pat = self.lower_pat(pat);
1298                         self.arm(hir_vec![pat], body_expr)
1299                     };
1300
1301                     // `[_ if <else_opt_if_cond> => <else_opt_if_body>,]`
1302                     let mut else_opt = else_opt.as_ref().map(|e| self.lower_expr(e));
1303                     let else_if_arms = {
1304                         let mut arms = vec![];
1305                         loop {
1306                             let else_opt_continue = else_opt.and_then(|els| {
1307                                 els.and_then(|els| {
1308                                     match els.node {
1309                                         // else if
1310                                         hir::ExprIf(cond, then, else_opt) => {
1311                                             let pat_under = self.pat_wild(e.span);
1312                                             arms.push(hir::Arm {
1313                                                 attrs: hir_vec![],
1314                                                 pats: hir_vec![pat_under],
1315                                                 guard: Some(cond),
1316                                                 body: self.expr_block(then, ThinVec::new()),
1317                                             });
1318                                             else_opt.map(|else_opt| (else_opt, true))
1319                                         }
1320                                         _ => Some((P(els), false)),
1321                                     }
1322                                 })
1323                             });
1324                             match else_opt_continue {
1325                                 Some((e, true)) => {
1326                                     else_opt = Some(e);
1327                                 }
1328                                 Some((e, false)) => {
1329                                     else_opt = Some(e);
1330                                     break;
1331                                 }
1332                                 None => {
1333                                     else_opt = None;
1334                                     break;
1335                                 }
1336                             }
1337                         }
1338                         arms
1339                     };
1340
1341                     let contains_else_clause = else_opt.is_some();
1342
1343                     // `_ => [<else_opt> | ()]`
1344                     let else_arm = {
1345                         let pat_under = self.pat_wild(e.span);
1346                         let else_expr =
1347                             else_opt.unwrap_or_else(|| self.expr_tuple(e.span, hir_vec![]));
1348                         self.arm(hir_vec![pat_under], else_expr)
1349                     };
1350
1351                     let mut arms = Vec::with_capacity(else_if_arms.len() + 2);
1352                     arms.push(pat_arm);
1353                     arms.extend(else_if_arms);
1354                     arms.push(else_arm);
1355
1356                     let sub_expr = self.lower_expr(sub_expr);
1357                     // add attributes to the outer returned expr node
1358                     return self.expr(e.span,
1359                                      hir::ExprMatch(sub_expr,
1360                                                     arms.into(),
1361                                                     hir::MatchSource::IfLetDesugar {
1362                                                         contains_else_clause: contains_else_clause,
1363                                                     }),
1364                                      e.attrs.clone());
1365                 }
1366
1367                 // Desugar ExprWhileLet
1368                 // From: `[opt_ident]: while let <pat> = <sub_expr> <body>`
1369                 ExprKind::WhileLet(ref pat, ref sub_expr, ref body, opt_ident) => {
1370                     // to:
1371                     //
1372                     //   [opt_ident]: loop {
1373                     //     match <sub_expr> {
1374                     //       <pat> => <body>,
1375                     //       _ => break
1376                     //     }
1377                     //   }
1378
1379                     // `<pat> => <body>`
1380                     let pat_arm = {
1381                         let body = self.lower_block(body);
1382                         let body_expr = self.expr_block(body, ThinVec::new());
1383                         let pat = self.lower_pat(pat);
1384                         self.arm(hir_vec![pat], body_expr)
1385                     };
1386
1387                     // `_ => break`
1388                     let break_arm = {
1389                         let pat_under = self.pat_wild(e.span);
1390                         let break_expr = self.expr_break(e.span, ThinVec::new());
1391                         self.arm(hir_vec![pat_under], break_expr)
1392                     };
1393
1394                     // `match <sub_expr> { ... }`
1395                     let arms = hir_vec![pat_arm, break_arm];
1396                     let sub_expr = self.lower_expr(sub_expr);
1397                     let match_expr = self.expr(e.span,
1398                                                hir::ExprMatch(sub_expr,
1399                                                               arms,
1400                                                               hir::MatchSource::WhileLetDesugar),
1401                                                ThinVec::new());
1402
1403                     // `[opt_ident]: loop { ... }`
1404                     let loop_block = self.block_expr(match_expr);
1405                     let loop_expr = hir::ExprLoop(loop_block, self.lower_opt_sp_ident(opt_ident));
1406                     // add attributes to the outer returned expr node
1407                     let attrs = e.attrs.clone();
1408                     return P(hir::Expr { id: e.id, node: loop_expr, span: e.span, attrs: attrs });
1409                 }
1410
1411                 // Desugar ExprForLoop
1412                 // From: `[opt_ident]: for <pat> in <head> <body>`
1413                 ExprKind::ForLoop(ref pat, ref head, ref body, opt_ident) => {
1414                     // to:
1415                     //
1416                     //   {
1417                     //     let result = match ::std::iter::IntoIterator::into_iter(<head>) {
1418                     //       mut iter => {
1419                     //         [opt_ident]: loop {
1420                     //           match ::std::iter::Iterator::next(&mut iter) {
1421                     //             ::std::option::Option::Some(<pat>) => <body>,
1422                     //             ::std::option::Option::None => break
1423                     //           }
1424                     //         }
1425                     //       }
1426                     //     };
1427                     //     result
1428                     //   }
1429
1430                     // expand <head>
1431                     let head = self.lower_expr(head);
1432
1433                     let iter = self.str_to_ident("iter");
1434
1435                     // `::std::option::Option::Some(<pat>) => <body>`
1436                     let pat_arm = {
1437                         let body_block = self.lower_block(body);
1438                         let body_span = body_block.span;
1439                         let body_expr = P(hir::Expr {
1440                             id: self.next_id(),
1441                             node: hir::ExprBlock(body_block),
1442                             span: body_span,
1443                             attrs: ThinVec::new(),
1444                         });
1445                         let pat = self.lower_pat(pat);
1446                         let some_pat = self.pat_some(e.span, pat);
1447
1448                         self.arm(hir_vec![some_pat], body_expr)
1449                     };
1450
1451                     // `::std::option::Option::None => break`
1452                     let break_arm = {
1453                         let break_expr = self.expr_break(e.span, ThinVec::new());
1454                         let pat = self.pat_none(e.span);
1455                         self.arm(hir_vec![pat], break_expr)
1456                     };
1457
1458                     // `mut iter`
1459                     let iter_pat = self.pat_ident_binding_mode(e.span, iter,
1460                                                                hir::BindByValue(hir::MutMutable));
1461
1462                     // `match ::std::iter::Iterator::next(&mut iter) { ... }`
1463                     let match_expr = {
1464                         let next_path = self.std_path(e.span, &["iter", "Iterator", "next"]);
1465                         let iter = self.expr_ident(e.span, iter, iter_pat.id);
1466                         let ref_mut_iter = self.expr_mut_addr_of(e.span, iter);
1467                         let next_path = self.expr_path(next_path, ThinVec::new());
1468                         let next_expr = self.expr_call(e.span, next_path, hir_vec![ref_mut_iter]);
1469                         let arms = hir_vec![pat_arm, break_arm];
1470
1471                         self.expr(e.span,
1472                                   hir::ExprMatch(next_expr, arms, hir::MatchSource::ForLoopDesugar),
1473                                   ThinVec::new())
1474                     };
1475
1476                     // `[opt_ident]: loop { ... }`
1477                     let loop_block = self.block_expr(match_expr);
1478                     let loop_expr = hir::ExprLoop(loop_block, self.lower_opt_sp_ident(opt_ident));
1479                     let loop_expr = P(hir::Expr {
1480                         id: e.id,
1481                         node: loop_expr,
1482                         span: e.span,
1483                         attrs: ThinVec::new(),
1484                     });
1485
1486                     // `mut iter => { ... }`
1487                     let iter_arm = self.arm(hir_vec![iter_pat], loop_expr);
1488
1489                     // `match ::std::iter::IntoIterator::into_iter(<head>) { ... }`
1490                     let into_iter_expr = {
1491                         let into_iter_path = self.std_path(e.span,
1492                                                            &["iter", "IntoIterator", "into_iter"]);
1493
1494                         let into_iter = self.expr_path(into_iter_path, ThinVec::new());
1495                         self.expr_call(e.span, into_iter, hir_vec![head])
1496                     };
1497
1498                     let match_expr = self.expr_match(e.span,
1499                                                      into_iter_expr,
1500                                                      hir_vec![iter_arm],
1501                                                      hir::MatchSource::ForLoopDesugar);
1502
1503                     // `{ let _result = ...; _result }`
1504                     // underscore prevents an unused_variables lint if the head diverges
1505                     let result_ident = self.str_to_ident("_result");
1506                     let (let_stmt, let_stmt_binding) =
1507                         self.stmt_let(e.span, false, result_ident, match_expr);
1508
1509                     let result = self.expr_ident(e.span, result_ident, let_stmt_binding);
1510                     let block = self.block_all(e.span, hir_vec![let_stmt], Some(result));
1511                     // add the attributes to the outer returned expr node
1512                     return self.expr_block(block, e.attrs.clone());
1513                 }
1514
1515                 // Desugar ExprKind::Try
1516                 // From: `<expr>?`
1517                 ExprKind::Try(ref sub_expr) => {
1518                     // to:
1519                     //
1520                     // {
1521                     //     match { Carrier::translate( { <expr> } ) } {
1522                     //         Ok(val) => val,
1523                     //         Err(err) => { return Carrier::from_error(From::from(err)); }
1524                     //     }
1525                     // }
1526
1527                     // { Carrier::translate( { <expr> } ) }
1528                     let discr = {
1529                         // expand <expr>
1530                         let sub_expr = self.lower_expr(sub_expr);
1531                         let sub_expr = self.signal_block_expr(hir_vec![],
1532                                                               sub_expr,
1533                                                               e.span,
1534                                                               hir::PopUnstableBlock,
1535                                                               ThinVec::new());
1536
1537                         let path = self.std_path(e.span, &["ops", "Carrier", "translate"]);
1538                         let path = self.expr_path(path, ThinVec::new());
1539                         let call = self.expr_call(e.span, path, hir_vec![sub_expr]);
1540
1541                         self.signal_block_expr(hir_vec![],
1542                                                call,
1543                                                e.span,
1544                                                hir::PushUnstableBlock,
1545                                                ThinVec::new())
1546                     };
1547
1548                     // Ok(val) => val
1549                     let ok_arm = {
1550                         let val_ident = self.str_to_ident("val");
1551                         let val_pat = self.pat_ident(e.span, val_ident);
1552                         let val_expr = self.expr_ident(e.span, val_ident, val_pat.id);
1553                         let ok_pat = self.pat_ok(e.span, val_pat);
1554
1555                         self.arm(hir_vec![ok_pat], val_expr)
1556                     };
1557
1558                     // Err(err) => { return Carrier::from_error(From::from(err)); }
1559                     let err_arm = {
1560                         let err_ident = self.str_to_ident("err");
1561                         let err_local = self.pat_ident(e.span, err_ident);
1562                         let from_expr = {
1563                             let path = self.std_path(e.span, &["convert", "From", "from"]);
1564                             let from = self.expr_path(path, ThinVec::new());
1565                             let err_expr = self.expr_ident(e.span, err_ident, err_local.id);
1566
1567                             self.expr_call(e.span, from, hir_vec![err_expr])
1568                         };
1569                         let from_err_expr = {
1570                             let path = self.std_path(e.span, &["ops", "Carrier", "from_error"]);
1571                             let from_err = self.expr_path(path, ThinVec::new());
1572                             self.expr_call(e.span, from_err, hir_vec![from_expr])
1573                         };
1574
1575                         let ret_expr = self.expr(e.span,
1576                                                  hir::Expr_::ExprRet(Some(from_err_expr)),
1577                                                                      ThinVec::new());
1578                         let ret_stmt = self.stmt_expr(ret_expr);
1579                         let block = self.signal_block_stmt(ret_stmt, e.span,
1580                                                            hir::PushUnstableBlock, ThinVec::new());
1581
1582                         let err_pat = self.pat_err(e.span, err_local);
1583                         self.arm(hir_vec![err_pat], block)
1584                     };
1585
1586                     return self.expr_match(e.span, discr, hir_vec![err_arm, ok_arm],
1587                                            hir::MatchSource::TryDesugar);
1588                 }
1589
1590                 ExprKind::Mac(_) => panic!("Shouldn't exist here"),
1591             },
1592             span: e.span,
1593             attrs: e.attrs.clone(),
1594         })
1595     }
1596
1597     fn lower_stmt(&mut self, s: &Stmt) -> hir::Stmt {
1598         match s.node {
1599             StmtKind::Local(ref l) => Spanned {
1600                 node: hir::StmtDecl(P(Spanned {
1601                     node: hir::DeclLocal(self.lower_local(l)),
1602                     span: s.span,
1603                 }), s.id),
1604                 span: s.span,
1605             },
1606             StmtKind::Item(ref it) => Spanned {
1607                 node: hir::StmtDecl(P(Spanned {
1608                     node: hir::DeclItem(self.lower_item_id(it)),
1609                     span: s.span,
1610                 }), s.id),
1611                 span: s.span,
1612             },
1613             StmtKind::Expr(ref e) => {
1614                 Spanned {
1615                     node: hir::StmtExpr(self.lower_expr(e), s.id),
1616                     span: s.span,
1617                 }
1618             }
1619             StmtKind::Semi(ref e) => {
1620                 Spanned {
1621                     node: hir::StmtSemi(self.lower_expr(e), s.id),
1622                     span: s.span,
1623                 }
1624             }
1625             StmtKind::Mac(..) => panic!("Shouldn't exist here"),
1626         }
1627     }
1628
1629     fn lower_capture_clause(&mut self, c: CaptureBy) -> hir::CaptureClause {
1630         match c {
1631             CaptureBy::Value => hir::CaptureByValue,
1632             CaptureBy::Ref => hir::CaptureByRef,
1633         }
1634     }
1635
1636     fn lower_visibility(&mut self, v: &Visibility) -> hir::Visibility {
1637         match *v {
1638             Visibility::Public => hir::Public,
1639             Visibility::Crate(_) => hir::Visibility::Crate,
1640             Visibility::Restricted { ref path, id } =>
1641                 hir::Visibility::Restricted { path: P(self.lower_path(path)), id: id },
1642             Visibility::Inherited => hir::Inherited,
1643         }
1644     }
1645
1646     fn lower_defaultness(&mut self, d: Defaultness) -> hir::Defaultness {
1647         match d {
1648             Defaultness::Default => hir::Defaultness::Default,
1649             Defaultness::Final => hir::Defaultness::Final,
1650         }
1651     }
1652
1653     fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode {
1654         match *b {
1655             BlockCheckMode::Default => hir::DefaultBlock,
1656             BlockCheckMode::Unsafe(u) => hir::UnsafeBlock(self.lower_unsafe_source(u)),
1657         }
1658     }
1659
1660     fn lower_binding_mode(&mut self, b: &BindingMode) -> hir::BindingMode {
1661         match *b {
1662             BindingMode::ByRef(m) => hir::BindByRef(self.lower_mutability(m)),
1663             BindingMode::ByValue(m) => hir::BindByValue(self.lower_mutability(m)),
1664         }
1665     }
1666
1667     fn lower_unsafe_source(&mut self, u: UnsafeSource) -> hir::UnsafeSource {
1668         match u {
1669             CompilerGenerated => hir::CompilerGenerated,
1670             UserProvided => hir::UserProvided,
1671         }
1672     }
1673
1674     fn lower_impl_polarity(&mut self, i: ImplPolarity) -> hir::ImplPolarity {
1675         match i {
1676             ImplPolarity::Positive => hir::ImplPolarity::Positive,
1677             ImplPolarity::Negative => hir::ImplPolarity::Negative,
1678         }
1679     }
1680
1681     fn lower_trait_bound_modifier(&mut self, f: TraitBoundModifier) -> hir::TraitBoundModifier {
1682         match f {
1683             TraitBoundModifier::None => hir::TraitBoundModifier::None,
1684             TraitBoundModifier::Maybe => hir::TraitBoundModifier::Maybe,
1685         }
1686     }
1687
1688     // Helper methods for building HIR.
1689
1690     fn arm(&mut self, pats: hir::HirVec<P<hir::Pat>>, expr: P<hir::Expr>) -> hir::Arm {
1691         hir::Arm {
1692             attrs: hir_vec![],
1693             pats: pats,
1694             guard: None,
1695             body: expr,
1696         }
1697     }
1698
1699     fn field(&mut self, name: Name, expr: P<hir::Expr>, span: Span) -> hir::Field {
1700         hir::Field {
1701             name: Spanned {
1702                 node: name,
1703                 span: span,
1704             },
1705             span: span,
1706             expr: expr,
1707         }
1708     }
1709
1710     fn expr_break(&mut self, span: Span, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
1711         self.expr(span, hir::ExprBreak(None), attrs)
1712     }
1713
1714     fn expr_call(&mut self, span: Span, e: P<hir::Expr>, args: hir::HirVec<P<hir::Expr>>)
1715                  -> P<hir::Expr> {
1716         self.expr(span, hir::ExprCall(e, args), ThinVec::new())
1717     }
1718
1719     fn expr_ident(&mut self, span: Span, id: Name, binding: NodeId) -> P<hir::Expr> {
1720         let expr_path = hir::ExprPath(None, self.path_ident(span, id));
1721         let expr = self.expr(span, expr_path, ThinVec::new());
1722
1723         let def = self.resolver.definitions().map(|defs| {
1724             Def::Local(defs.local_def_id(binding), binding)
1725         }).unwrap_or(Def::Err);
1726         self.resolver.record_resolution(expr.id, def);
1727
1728         expr
1729     }
1730
1731     fn expr_mut_addr_of(&mut self, span: Span, e: P<hir::Expr>) -> P<hir::Expr> {
1732         self.expr(span, hir::ExprAddrOf(hir::MutMutable, e), ThinVec::new())
1733     }
1734
1735     fn expr_path(&mut self, path: hir::Path, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
1736         let def = self.resolver.resolve_generated_global_path(&path, true);
1737         let expr = self.expr(path.span, hir::ExprPath(None, path), attrs);
1738         self.resolver.record_resolution(expr.id, def);
1739         expr
1740     }
1741
1742     fn expr_match(&mut self,
1743                   span: Span,
1744                   arg: P<hir::Expr>,
1745                   arms: hir::HirVec<hir::Arm>,
1746                   source: hir::MatchSource)
1747                   -> P<hir::Expr> {
1748         self.expr(span, hir::ExprMatch(arg, arms, source), ThinVec::new())
1749     }
1750
1751     fn expr_block(&mut self, b: P<hir::Block>, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
1752         self.expr(b.span, hir::ExprBlock(b), attrs)
1753     }
1754
1755     fn expr_tuple(&mut self, sp: Span, exprs: hir::HirVec<P<hir::Expr>>) -> P<hir::Expr> {
1756         self.expr(sp, hir::ExprTup(exprs), ThinVec::new())
1757     }
1758
1759     fn expr_struct(&mut self,
1760                    sp: Span,
1761                    path: hir::Path,
1762                    fields: hir::HirVec<hir::Field>,
1763                    e: Option<P<hir::Expr>>,
1764                    attrs: ThinVec<Attribute>) -> P<hir::Expr> {
1765         let def = self.resolver.resolve_generated_global_path(&path, false);
1766         let expr = self.expr(sp, hir::ExprStruct(path, fields, e), attrs);
1767         self.resolver.record_resolution(expr.id, def);
1768         expr
1769     }
1770
1771     fn expr(&mut self, span: Span, node: hir::Expr_, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
1772         P(hir::Expr {
1773             id: self.next_id(),
1774             node: node,
1775             span: span,
1776             attrs: attrs,
1777         })
1778     }
1779
1780     fn stmt_let(&mut self, sp: Span, mutbl: bool, ident: Name, ex: P<hir::Expr>)
1781                 -> (hir::Stmt, NodeId) {
1782         let pat = if mutbl {
1783             self.pat_ident_binding_mode(sp, ident, hir::BindByValue(hir::MutMutable))
1784         } else {
1785             self.pat_ident(sp, ident)
1786         };
1787         let pat_id = pat.id;
1788         let local = P(hir::Local {
1789             pat: pat,
1790             ty: None,
1791             init: Some(ex),
1792             id: self.next_id(),
1793             span: sp,
1794             attrs: ThinVec::new(),
1795         });
1796         let decl = respan(sp, hir::DeclLocal(local));
1797         (respan(sp, hir::StmtDecl(P(decl), self.next_id())), pat_id)
1798     }
1799
1800     // Turns `<expr>` into `<expr>;`, note that this produces a StmtSemi, not a
1801     // StmtExpr.
1802     fn stmt_expr(&self, expr: P<hir::Expr>) -> hir::Stmt {
1803         hir::Stmt {
1804             span: expr.span,
1805             node: hir::StmtSemi(expr, self.next_id()),
1806         }
1807     }
1808
1809     fn block_expr(&mut self, expr: P<hir::Expr>) -> P<hir::Block> {
1810         self.block_all(expr.span, hir::HirVec::new(), Some(expr))
1811     }
1812
1813     fn block_all(&mut self, span: Span, stmts: hir::HirVec<hir::Stmt>, expr: Option<P<hir::Expr>>)
1814                  -> P<hir::Block> {
1815         P(hir::Block {
1816             stmts: stmts,
1817             expr: expr,
1818             id: self.next_id(),
1819             rules: hir::DefaultBlock,
1820             span: span,
1821         })
1822     }
1823
1824     fn pat_ok(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
1825         let path = self.std_path(span, &["result", "Result", "Ok"]);
1826         self.pat_enum(span, path, hir_vec![pat])
1827     }
1828
1829     fn pat_err(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
1830         let path = self.std_path(span, &["result", "Result", "Err"]);
1831         self.pat_enum(span, path, hir_vec![pat])
1832     }
1833
1834     fn pat_some(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
1835         let path = self.std_path(span, &["option", "Option", "Some"]);
1836         self.pat_enum(span, path, hir_vec![pat])
1837     }
1838
1839     fn pat_none(&mut self, span: Span) -> P<hir::Pat> {
1840         let path = self.std_path(span, &["option", "Option", "None"]);
1841         self.pat_enum(span, path, hir_vec![])
1842     }
1843
1844     fn pat_enum(&mut self, span: Span, path: hir::Path, subpats: hir::HirVec<P<hir::Pat>>)
1845                 -> P<hir::Pat> {
1846         let def = self.resolver.resolve_generated_global_path(&path, true);
1847         let pt = if subpats.is_empty() {
1848             hir::PatKind::Path(None, path)
1849         } else {
1850             hir::PatKind::TupleStruct(path, subpats, None)
1851         };
1852         let pat = self.pat(span, pt);
1853         self.resolver.record_resolution(pat.id, def);
1854         pat
1855     }
1856
1857     fn pat_ident(&mut self, span: Span, name: Name) -> P<hir::Pat> {
1858         self.pat_ident_binding_mode(span, name, hir::BindByValue(hir::MutImmutable))
1859     }
1860
1861     fn pat_ident_binding_mode(&mut self, span: Span, name: Name, bm: hir::BindingMode)
1862                               -> P<hir::Pat> {
1863         let pat_ident = hir::PatKind::Binding(bm,
1864                                             Spanned {
1865                                                 span: span,
1866                                                 node: name,
1867                                             },
1868                                             None);
1869
1870         let pat = self.pat(span, pat_ident);
1871
1872         let parent_def = self.parent_def;
1873         let def = self.resolver.definitions().map(|defs| {
1874             let def_path_data = DefPathData::Binding(name.as_str());
1875             let def_index = defs.create_def_with_parent(parent_def, pat.id, def_path_data);
1876             Def::Local(DefId::local(def_index), pat.id)
1877         }).unwrap_or(Def::Err);
1878         self.resolver.record_resolution(pat.id, def);
1879
1880         pat
1881     }
1882
1883     fn pat_wild(&mut self, span: Span) -> P<hir::Pat> {
1884         self.pat(span, hir::PatKind::Wild)
1885     }
1886
1887     fn pat(&mut self, span: Span, pat: hir::PatKind) -> P<hir::Pat> {
1888         P(hir::Pat {
1889             id: self.next_id(),
1890             node: pat,
1891             span: span,
1892         })
1893     }
1894
1895     fn path_ident(&mut self, span: Span, id: Name) -> hir::Path {
1896         self.path(span, vec![id])
1897     }
1898
1899     fn path(&mut self, span: Span, strs: Vec<Name>) -> hir::Path {
1900         self.path_all(span, false, strs, hir::HirVec::new(), hir::HirVec::new(), hir::HirVec::new())
1901     }
1902
1903     fn path_global(&mut self, span: Span, strs: Vec<Name>) -> hir::Path {
1904         self.path_all(span, true, strs, hir::HirVec::new(), hir::HirVec::new(), hir::HirVec::new())
1905     }
1906
1907     fn path_all(&mut self,
1908                 sp: Span,
1909                 global: bool,
1910                 mut names: Vec<Name>,
1911                 lifetimes: hir::HirVec<hir::Lifetime>,
1912                 types: hir::HirVec<P<hir::Ty>>,
1913                 bindings: hir::HirVec<hir::TypeBinding>)
1914                 -> hir::Path {
1915         let last_identifier = names.pop().unwrap();
1916         let mut segments: Vec<hir::PathSegment> = names.into_iter().map(|name| {
1917             hir::PathSegment {
1918                 name: name,
1919                 parameters: hir::PathParameters::none(),
1920            }
1921         }).collect();
1922
1923         segments.push(hir::PathSegment {
1924             name: last_identifier,
1925             parameters: hir::AngleBracketedParameters(hir::AngleBracketedParameterData {
1926                 lifetimes: lifetimes,
1927                 types: types,
1928                 bindings: bindings,
1929             }),
1930         });
1931         hir::Path {
1932             span: sp,
1933             global: global,
1934             segments: segments.into(),
1935         }
1936     }
1937
1938     fn std_path_components(&mut self, components: &[&str]) -> Vec<Name> {
1939         let mut v = Vec::new();
1940         if let Some(s) = self.crate_root {
1941             v.push(token::intern(s));
1942         }
1943         v.extend(components.iter().map(|s| token::intern(s)));
1944         return v;
1945     }
1946
1947     // Given suffix ["b","c","d"], returns path `::std::b::c::d` when
1948     // `fld.cx.use_std`, and `::core::b::c::d` otherwise.
1949     fn std_path(&mut self, span: Span, components: &[&str]) -> hir::Path {
1950         let idents = self.std_path_components(components);
1951         self.path_global(span, idents)
1952     }
1953
1954     fn signal_block_expr(&mut self,
1955                          stmts: hir::HirVec<hir::Stmt>,
1956                          expr: P<hir::Expr>,
1957                          span: Span,
1958                          rule: hir::BlockCheckMode,
1959                          attrs: ThinVec<Attribute>)
1960                          -> P<hir::Expr> {
1961         let id = self.next_id();
1962         let block = P(hir::Block {
1963             rules: rule,
1964             span: span,
1965             id: id,
1966             stmts: stmts,
1967             expr: Some(expr),
1968         });
1969         self.expr_block(block, attrs)
1970     }
1971
1972     fn signal_block_stmt(&mut self,
1973                          stmt: hir::Stmt,
1974                          span: Span,
1975                          rule: hir::BlockCheckMode,
1976                          attrs: ThinVec<Attribute>)
1977                          -> P<hir::Expr> {
1978         let id = self.next_id();
1979         let block = P(hir::Block {
1980             rules: rule,
1981             span: span,
1982             id: id,
1983             stmts: hir_vec![stmt],
1984             expr: None,
1985         });
1986         self.expr_block(block, attrs)
1987     }
1988 }