src/librustc_typeck/collect.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 /*
  12
  13 # Collect phase
  14
  15 The collect phase of type check has the job of visiting all items,
  16 determining their type, and writing that type into the `tcx.tcache`
  17 table.  Despite its name, this table does not really operate as a
  18 *cache*, at least not for the types of items defined within the
  19 current crate: we assume that after the collect phase, the types of
  20 all local items will be present in the table.
  21
  22 Unlike most of the types that are present in Rust, the types computed
  23 for each item are in fact type schemes. This means that they are
  24 generic types that may have type parameters. TypeSchemes are
  25 represented by an instance of `ty::TypeScheme`.  This combines the
  26 core type along with a list of the bounds for each parameter. Type
  27 parameters themselves are represented as `ty_param()` instances.
  28
  29 The phasing of type conversion is somewhat complicated. There is no
  30 clear set of phases we can enforce (e.g., converting traits first,
  31 then types, or something like that) because the user can introduce
  32 arbitrary interdependencies. So instead we generally convert things
  33 lazilly and on demand, and include logic that checks for cycles.
  34 Demand is driven by calls to `AstConv::get_item_type_scheme` or
  35 `AstConv::lookup_trait_def`.
  36
  37 Currently, we "convert" types and traits in three phases (note that
  38 conversion only affects the types of items / enum variants / methods;
  39 it does not e.g. compute the types of individual expressions):
  40
  41 0. Intrinsics
  42 1. Trait definitions
  43 2. Type definitions
  44
  45 Conversion itself is done by simply walking each of the items in turn
  46 and invoking an appropriate function (e.g., `trait_def_of_item` or
  47 `convert_item`). However, it is possible that while converting an
  48 item, we may need to compute the *type scheme* or *trait definition*
  49 for other items.
  50
  51 There are some shortcomings in this design:
  52
  53 - Before walking the set of supertraits for a given trait, you must
  54   call `ensure_super_predicates` on that trait def-id. Otherwise,
  55   `lookup_super_predicates` will result in ICEs.
  56 - Because the type scheme includes defaults, cycles through type
  57   parameter defaults are illegal even if those defaults are never
  58   employed. This is not necessarily a bug.
  59 - The phasing of trait definitions before type definitions does not
  60   seem to be necessary, sufficient, or particularly helpful, given that
  61   processing a trait definition can trigger processing a type def and
  62   vice versa. However, if I remove it, I get ICEs, so some more work is
  63   needed in that area. -nmatsakis
  64
  65 */
  66
  67 use astconv::{self, AstConv, ty_of_arg, ast_ty_to_ty, ast_region_to_region};
  68 use middle::def;
  69 use middle::def_id::DefId;
  70 use constrained_type_params as ctp;
  71 use middle::lang_items::SizedTraitLangItem;
  72 use middle::free_region::FreeRegionMap;
  73 use middle::region;
  74 use middle::resolve_lifetime;
  75 use middle::const_eval::{self, ConstVal};
  76 use middle::const_eval::EvalHint::UncheckedExprHint;
  77 use middle::subst::{Substs, FnSpace, ParamSpace, SelfSpace, TypeSpace, VecPerParamSpace};
  78 use middle::ty::{ToPredicate, ImplContainer, ImplOrTraitItemContainer, TraitContainer};
  79 use middle::ty::{self, RegionEscape, ToPolyTraitRef, Ty, TypeScheme};
  80 use middle::ty::{VariantKind};
  81 use middle::ty::fold::{TypeFolder, TypeFoldable};
  82 use middle::ty::util::IntTypeExt;
  83 use middle::infer;
  84 use rscope::*;
  85 use rustc::front::map as hir_map;
  86 use util::common::{ErrorReported, memoized};
  87 use util::nodemap::{FnvHashMap, FnvHashSet};
  88 use write_ty_to_tcx;
  89
  90 use std::cell::{Cell, RefCell};
  91 use std::collections::HashSet;
  92 use std::rc::Rc;
  93
  94 use syntax::abi;
  95 use syntax::ast;
  96 use syntax::attr;
  97 use syntax::codemap::Span;
  98 use syntax::parse::token::special_idents;
  99 use syntax::ptr::P;
 100 use rustc_front::hir;
 101 use rustc_front::visit;
 102 use rustc_front::print::pprust;
 103
 104 ///////////////////////////////////////////////////////////////////////////
 105 // Main entry point
 106
 107 pub fn collect_item_types(tcx: &ty::ctxt) {
 108     let ccx = &CrateCtxt { tcx: tcx, stack: RefCell::new(Vec::new()) };
 109
 110     let mut visitor = CollectTraitDefVisitor{ ccx: ccx };
 111     visit::walk_crate(&mut visitor, ccx.tcx.map.krate());
 112
 113     let mut visitor = CollectItemTypesVisitor{ ccx: ccx };
 114     visit::walk_crate(&mut visitor, ccx.tcx.map.krate());
 115 }
 116
 117 ///////////////////////////////////////////////////////////////////////////
 118
 119 struct CrateCtxt<'a,'tcx:'a> {
 120     tcx: &'a ty::ctxt<'tcx>,
 121
 122     // This stack is used to identify cycles in the user's source.
 123     // Note that these cycles can cross multiple items.
 124     stack: RefCell<Vec<AstConvRequest>>,
 125 }
 126
 127 /// Context specific to some particular item. This is what implements
 128 /// AstConv. It has information about the predicates that are defined
 129 /// on the trait. Unfortunately, this predicate information is
 130 /// available in various different forms at various points in the
 131 /// process. So we can't just store a pointer to e.g. the AST or the
 132 /// parsed ty form, we have to be more flexible. To this end, the
 133 /// `ItemCtxt` is parameterized by a `GetTypeParameterBounds` object
 134 /// that it uses to satisfy `get_type_parameter_bounds` requests.
 135 /// This object might draw the information from the AST
 136 /// (`hir::Generics`) or it might draw from a `ty::GenericPredicates`
 137 /// or both (a tuple).
 138 struct ItemCtxt<'a,'tcx:'a> {
 139     ccx: &'a CrateCtxt<'a,'tcx>,
 140     param_bounds: &'a (GetTypeParameterBounds<'tcx>+'a),
 141 }
 142
 143 #[derive(Copy, Clone, PartialEq, Eq)]
 144 enum AstConvRequest {
 145     GetItemTypeScheme(DefId),
 146     GetTraitDef(DefId),
 147     EnsureSuperPredicates(DefId),
 148     GetTypeParameterBounds(ast::NodeId),
 149 }
 150
 151 ///////////////////////////////////////////////////////////////////////////
 152 // First phase: just collect *trait definitions* -- basically, the set
 153 // of type parameters and supertraits. This is information we need to
 154 // know later when parsing field defs.
 155
 156 struct CollectTraitDefVisitor<'a, 'tcx: 'a> {
 157     ccx: &'a CrateCtxt<'a, 'tcx>
 158 }
 159
 160 impl<'a, 'tcx, 'v> visit::Visitor<'v> for CollectTraitDefVisitor<'a, 'tcx> {
 161     fn visit_item(&mut self, i: &hir::Item) {
 162         match i.node {
 163             hir::ItemTrait(..) => {
 164                 // computing the trait def also fills in the table
 165                 let _ = trait_def_of_item(self.ccx, i);
 166             }
 167             _ => { }
 168         }
 169
 170         visit::walk_item(self, i);
 171     }
 172 }
 173
 174 ///////////////////////////////////////////////////////////////////////////
 175 // Second phase: collection proper.
 176
 177 struct CollectItemTypesVisitor<'a, 'tcx: 'a> {
 178     ccx: &'a CrateCtxt<'a, 'tcx>
 179 }
 180
 181 impl<'a, 'tcx, 'v> visit::Visitor<'v> for CollectItemTypesVisitor<'a, 'tcx> {
 182     fn visit_item(&mut self, i: &hir::Item) {
 183         convert_item(self.ccx, i);
 184         visit::walk_item(self, i);
 185     }
 186     fn visit_foreign_item(&mut self, i: &hir::ForeignItem) {
 187         convert_foreign_item(self.ccx, i);
 188         visit::walk_foreign_item(self, i);
 189     }
 190 }
 191
 192 ///////////////////////////////////////////////////////////////////////////
 193 // Utility types and common code for the above passes.
 194
 195 impl<'a,'tcx> CrateCtxt<'a,'tcx> {
 196     fn icx(&'a self, param_bounds: &'a GetTypeParameterBounds<'tcx>) -> ItemCtxt<'a,'tcx> {
 197         ItemCtxt { ccx: self, param_bounds: param_bounds }
 198     }
 199
 200     fn method_ty(&self, method_id: ast::NodeId) -> Rc<ty::Method<'tcx>> {
 201         let def_id = self.tcx.map.local_def_id(method_id);
 202         match *self.tcx.impl_or_trait_items.borrow().get(&def_id).unwrap() {
 203             ty::MethodTraitItem(ref mty) => mty.clone(),
 204             _ => {
 205                 self.tcx.sess.bug(&format!("method with id {} has the wrong type", method_id));
 206             }
 207         }
 208     }
 209
 210     fn cycle_check<F,R>(&self,
 211                         span: Span,
 212                         request: AstConvRequest,
 213                         code: F)
 214                         -> Result<R,ErrorReported>
 215         where F: FnOnce() -> Result<R,ErrorReported>
 216     {
 217         {
 218             let mut stack = self.stack.borrow_mut();
 219             match stack.iter().enumerate().rev().find(|&(_, r)| *r == request) {
 220                 None => { }
 221                 Some((i, _)) => {
 222                     let cycle = &stack[i..];
 223                     self.report_cycle(span, cycle);
 224                     return Err(ErrorReported);
 225                 }
 226             }
 227             stack.push(request);
 228         }
 229
 230         let result = code();
 231
 232         self.stack.borrow_mut().pop();
 233         result
 234     }
 235
 236     fn report_cycle(&self,
 237                     span: Span,
 238                     cycle: &[AstConvRequest])
 239     {
 240         assert!(!cycle.is_empty());
 241         let tcx = self.tcx;
 242
 243         span_err!(tcx.sess, span, E0391,
 244             "unsupported cyclic reference between types/traits detected");
 245
 246         match cycle[0] {
 247             AstConvRequest::GetItemTypeScheme(def_id) |
 248             AstConvRequest::GetTraitDef(def_id) => {
 249                 tcx.sess.note(
 250                     &format!("the cycle begins when processing `{}`...",
 251                              tcx.item_path_str(def_id)));
 252             }
 253             AstConvRequest::EnsureSuperPredicates(def_id) => {
 254                 tcx.sess.note(
 255                     &format!("the cycle begins when computing the supertraits of `{}`...",
 256                              tcx.item_path_str(def_id)));
 257             }
 258             AstConvRequest::GetTypeParameterBounds(id) => {
 259                 let def = tcx.type_parameter_def(id);
 260                 tcx.sess.note(
 261                     &format!("the cycle begins when computing the bounds \
 262                               for type parameter `{}`...",
 263                              def.name));
 264             }
 265         }
 266
 267         for request in &cycle[1..] {
 268             match *request {
 269                 AstConvRequest::GetItemTypeScheme(def_id) |
 270                 AstConvRequest::GetTraitDef(def_id) => {
 271                     tcx.sess.note(
 272                         &format!("...which then requires processing `{}`...",
 273                                  tcx.item_path_str(def_id)));
 274                 }
 275                 AstConvRequest::EnsureSuperPredicates(def_id) => {
 276                     tcx.sess.note(
 277                         &format!("...which then requires computing the supertraits of `{}`...",
 278                                  tcx.item_path_str(def_id)));
 279                 }
 280                 AstConvRequest::GetTypeParameterBounds(id) => {
 281                     let def = tcx.type_parameter_def(id);
 282                     tcx.sess.note(
 283                         &format!("...which then requires computing the bounds \
 284                                   for type parameter `{}`...",
 285                                  def.name));
 286                 }
 287             }
 288         }
 289
 290         match cycle[0] {
 291             AstConvRequest::GetItemTypeScheme(def_id) |
 292             AstConvRequest::GetTraitDef(def_id) => {
 293                 tcx.sess.note(
 294                     &format!("...which then again requires processing `{}`, completing the cycle.",
 295                              tcx.item_path_str(def_id)));
 296             }
 297             AstConvRequest::EnsureSuperPredicates(def_id) => {
 298                 tcx.sess.note(
 299                     &format!("...which then again requires computing the supertraits of `{}`, \
 300                               completing the cycle.",
 301                              tcx.item_path_str(def_id)));
 302             }
 303             AstConvRequest::GetTypeParameterBounds(id) => {
 304                 let def = tcx.type_parameter_def(id);
 305                 tcx.sess.note(
 306                     &format!("...which then again requires computing the bounds \
 307                               for type parameter `{}`, completing the cycle.",
 308                              def.name));
 309             }
 310         }
 311     }
 312
 313     /// Loads the trait def for a given trait, returning ErrorReported if a cycle arises.
 314     fn get_trait_def(&self, trait_id: DefId)
 315                      -> &'tcx ty::TraitDef<'tcx>
 316     {
 317         let tcx = self.tcx;
 318
 319         if let Some(trait_id) = tcx.map.as_local_node_id(trait_id) {
 320             let item = match tcx.map.get(trait_id) {
 321                 hir_map::NodeItem(item) => item,
 322                 _ => tcx.sess.bug(&format!("get_trait_def({:?}): not an item", trait_id))
 323             };
 324
 325             trait_def_of_item(self, &*item)
 326         } else {
 327             tcx.lookup_trait_def(trait_id)
 328         }
 329     }
 330
 331     /// Ensure that the (transitive) super predicates for
 332     /// `trait_def_id` are available. This will report a cycle error
 333     /// if a trait `X` (transitively) extends itself in some form.
 334     fn ensure_super_predicates(&self, span: Span, trait_def_id: DefId)
 335                                -> Result<(), ErrorReported>
 336     {
 337         self.cycle_check(span, AstConvRequest::EnsureSuperPredicates(trait_def_id), || {
 338             let def_ids = ensure_super_predicates_step(self, trait_def_id);
 339
 340             for def_id in def_ids {
 341                 try!(self.ensure_super_predicates(span, def_id));
 342             }
 343
 344             Ok(())
 345         })
 346     }
 347 }
 348
 349 impl<'a,'tcx> ItemCtxt<'a,'tcx> {
 350     fn to_ty<RS:RegionScope>(&self, rs: &RS, ast_ty: &hir::Ty) -> Ty<'tcx> {
 351         ast_ty_to_ty(self, rs, ast_ty)
 352     }
 353 }
 354
 355 impl<'a, 'tcx> AstConv<'tcx> for ItemCtxt<'a, 'tcx> {
 356     fn tcx(&self) -> &ty::ctxt<'tcx> { self.ccx.tcx }
 357
 358     fn get_item_type_scheme(&self, span: Span, id: DefId)
 359                             -> Result<ty::TypeScheme<'tcx>, ErrorReported>
 360     {
 361         self.ccx.cycle_check(span, AstConvRequest::GetItemTypeScheme(id), || {
 362             Ok(type_scheme_of_def_id(self.ccx, id))
 363         })
 364     }
 365
 366     fn get_trait_def(&self, span: Span, id: DefId)
 367                      -> Result<&'tcx ty::TraitDef<'tcx>, ErrorReported>
 368     {
 369         self.ccx.cycle_check(span, AstConvRequest::GetTraitDef(id), || {
 370             Ok(self.ccx.get_trait_def(id))
 371         })
 372     }
 373
 374     fn ensure_super_predicates(&self,
 375                                span: Span,
 376                                trait_def_id: DefId)
 377                                -> Result<(), ErrorReported>
 378     {
 379         debug!("ensure_super_predicates(trait_def_id={:?})",
 380                trait_def_id);
 381
 382         self.ccx.ensure_super_predicates(span, trait_def_id)
 383     }
 384
 385
 386     fn get_type_parameter_bounds(&self,
 387                                  span: Span,
 388                                  node_id: ast::NodeId)
 389                                  -> Result<Vec<ty::PolyTraitRef<'tcx>>, ErrorReported>
 390     {
 391         self.ccx.cycle_check(span, AstConvRequest::GetTypeParameterBounds(node_id), || {
 392             let v = self.param_bounds.get_type_parameter_bounds(self, span, node_id)
 393                                      .into_iter()
 394                                      .filter_map(|p| p.to_opt_poly_trait_ref())
 395                                      .collect();
 396             Ok(v)
 397         })
 398     }
 399
 400     fn trait_defines_associated_type_named(&self,
 401                                            trait_def_id: DefId,
 402                                            assoc_name: ast::Name)
 403                                            -> bool
 404     {
 405         if let Some(trait_id) = self.tcx().map.as_local_node_id(trait_def_id) {
 406             trait_defines_associated_type_named(self.ccx, trait_id, assoc_name)
 407         } else {
 408             let trait_def = self.tcx().lookup_trait_def(trait_def_id);
 409             trait_def.associated_type_names.contains(&assoc_name)
 410         }
 411     }
 412
 413         fn ty_infer(&self,
 414                     _ty_param_def: Option<ty::TypeParameterDef<'tcx>>,
 415                     _substs: Option<&mut Substs<'tcx>>,
 416                     _space: Option<ParamSpace>,
 417                     span: Span) -> Ty<'tcx> {
 418         span_err!(self.tcx().sess, span, E0121,
 419                   "the type placeholder `_` is not allowed within types on item signatures");
 420         self.tcx().types.err
 421     }
 422
 423     fn projected_ty(&self,
 424                     _span: Span,
 425                     trait_ref: ty::TraitRef<'tcx>,
 426                     item_name: ast::Name)
 427                     -> Ty<'tcx>
 428     {
 429         self.tcx().mk_projection(trait_ref, item_name)
 430     }
 431 }
 432
 433 /// Interface used to find the bounds on a type parameter from within
 434 /// an `ItemCtxt`. This allows us to use multiple kinds of sources.
 435 trait GetTypeParameterBounds<'tcx> {
 436     fn get_type_parameter_bounds(&self,
 437                                  astconv: &AstConv<'tcx>,
 438                                  span: Span,
 439                                  node_id: ast::NodeId)
 440                                  -> Vec<ty::Predicate<'tcx>>;
 441 }
 442
 443 /// Find bounds from both elements of the tuple.
 444 impl<'a,'b,'tcx,A,B> GetTypeParameterBounds<'tcx> for (&'a A,&'b B)
 445     where A : GetTypeParameterBounds<'tcx>, B : GetTypeParameterBounds<'tcx>
 446 {
 447     fn get_type_parameter_bounds(&self,
 448                                  astconv: &AstConv<'tcx>,
 449                                  span: Span,
 450                                  node_id: ast::NodeId)
 451                                  -> Vec<ty::Predicate<'tcx>>
 452     {
 453         let mut v = self.0.get_type_parameter_bounds(astconv, span, node_id);
 454         v.extend(self.1.get_type_parameter_bounds(astconv, span, node_id));
 455         v
 456     }
 457 }
 458
 459 /// Empty set of bounds.
 460 impl<'tcx> GetTypeParameterBounds<'tcx> for () {
 461     fn get_type_parameter_bounds(&self,
 462                                  _astconv: &AstConv<'tcx>,
 463                                  _span: Span,
 464                                  _node_id: ast::NodeId)
 465                                  -> Vec<ty::Predicate<'tcx>>
 466     {
 467         Vec::new()
 468     }
 469 }
 470
 471 /// Find bounds from the parsed and converted predicates.  This is
 472 /// used when converting methods, because by that time the predicates
 473 /// from the trait/impl have been fully converted.
 474 impl<'tcx> GetTypeParameterBounds<'tcx> for ty::GenericPredicates<'tcx> {
 475     fn get_type_parameter_bounds(&self,
 476                                  astconv: &AstConv<'tcx>,
 477                                  _span: Span,
 478                                  node_id: ast::NodeId)
 479                                  -> Vec<ty::Predicate<'tcx>>
 480     {
 481         let def = astconv.tcx().type_parameter_def(node_id);
 482
 483         self.predicates
 484             .iter()
 485             .filter(|predicate| {
 486                 match **predicate {
 487                     ty::Predicate::Trait(ref data) => {
 488                         data.skip_binder().self_ty().is_param(def.space, def.index)
 489                     }
 490                     ty::Predicate::TypeOutlives(ref data) => {
 491                         data.skip_binder().0.is_param(def.space, def.index)
 492                     }
 493                     ty::Predicate::Equate(..) |
 494                     ty::Predicate::RegionOutlives(..) |
 495                     ty::Predicate::WellFormed(..) |
 496                     ty::Predicate::ObjectSafe(..) |
 497                     ty::Predicate::Projection(..) => {
 498                         false
 499                     }
 500                 }
 501             })
 502             .cloned()
 503             .collect()
 504     }
 505 }
 506
 507 /// Find bounds from hir::Generics. This requires scanning through the
 508 /// AST. We do this to avoid having to convert *all* the bounds, which
 509 /// would create artificial cycles. Instead we can only convert the
 510 /// bounds for those a type parameter `X` if `X::Foo` is used.
 511 impl<'tcx> GetTypeParameterBounds<'tcx> for hir::Generics {
 512     fn get_type_parameter_bounds(&self,
 513                                  astconv: &AstConv<'tcx>,
 514                                  _: Span,
 515                                  node_id: ast::NodeId)
 516                                  -> Vec<ty::Predicate<'tcx>>
 517     {
 518         // In the AST, bounds can derive from two places. Either
 519         // written inline like `<T:Foo>` or in a where clause like
 520         // `where T:Foo`.
 521
 522         let def = astconv.tcx().type_parameter_def(node_id);
 523         let ty = astconv.tcx().mk_param_from_def(&def);
 524
 525         let from_ty_params =
 526             self.ty_params
 527                 .iter()
 528                 .filter(|p| p.id == node_id)
 529                 .flat_map(|p| p.bounds.iter())
 530                 .flat_map(|b| predicates_from_bound(astconv, ty, b));
 531
 532         let from_where_clauses =
 533             self.where_clause
 534                 .predicates
 535                 .iter()
 536                 .filter_map(|wp| match *wp {
 537                     hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 538                     _ => None
 539                 })
 540                 .filter(|bp| is_param(astconv.tcx(), &bp.bounded_ty, node_id))
 541                 .flat_map(|bp| bp.bounds.iter())
 542                 .flat_map(|b| predicates_from_bound(astconv, ty, b));
 543
 544         from_ty_params.chain(from_where_clauses).collect()
 545     }
 546 }
 547
 548 /// Tests whether this is the AST for a reference to the type
 549 /// parameter with id `param_id`. We use this so as to avoid running
 550 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
 551 /// conversion of the type to avoid inducing unnecessary cycles.
 552 fn is_param<'tcx>(tcx: &ty::ctxt<'tcx>,
 553                   ast_ty: &hir::Ty,
 554                   param_id: ast::NodeId)
 555                   -> bool
 556 {
 557     if let hir::TyPath(None, _) = ast_ty.node {
 558         let path_res = *tcx.def_map.borrow().get(&ast_ty.id).unwrap();
 559         match path_res.base_def {
 560             def::DefSelfTy(Some(def_id), None) => {
 561                 path_res.depth == 0 && def_id == tcx.map.local_def_id(param_id)
 562             }
 563             def::DefTyParam(_, _, def_id, _) => {
 564                 path_res.depth == 0 && def_id == tcx.map.local_def_id(param_id)
 565             }
 566             _ => {
 567                 false
 568             }
 569         }
 570     } else {
 571         false
 572     }
 573 }
 574
 575
 576 fn convert_method<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
 577                             container: ImplOrTraitItemContainer,
 578                             sig: &hir::MethodSig,
 579                             id: ast::NodeId,
 580                             name: ast::Name,
 581                             vis: hir::Visibility,
 582                             untransformed_rcvr_ty: Ty<'tcx>,
 583                             rcvr_ty_generics: &ty::Generics<'tcx>,
 584                             rcvr_ty_predicates: &ty::GenericPredicates<'tcx>) {
 585     let ty_generics = ty_generics_for_fn(ccx, &sig.generics, rcvr_ty_generics);
 586
 587     let ty_generic_predicates =
 588         ty_generic_predicates_for_fn(ccx, &sig.generics, rcvr_ty_predicates);
 589
 590     let (fty, explicit_self_category) =
 591         astconv::ty_of_method(&ccx.icx(&(rcvr_ty_predicates, &sig.generics)),
 592                               sig, untransformed_rcvr_ty);
 593
 594     let def_id = ccx.tcx.map.local_def_id(id);
 595     let ty_method = ty::Method::new(name,
 596                                     ty_generics,
 597                                     ty_generic_predicates,
 598                                     fty,
 599                                     explicit_self_category,
 600                                     vis,
 601                                     def_id,
 602                                     container);
 603
 604     let fty = ccx.tcx.mk_fn(Some(def_id),
 605                             ccx.tcx.mk_bare_fn(ty_method.fty.clone()));
 606     debug!("method {} (id {}) has type {:?}",
 607             name, id, fty);
 608     ccx.tcx.register_item_type(def_id, TypeScheme {
 609         generics: ty_method.generics.clone(),
 610         ty: fty
 611     });
 612     ccx.tcx.predicates.borrow_mut().insert(def_id, ty_method.predicates.clone());
 613
 614     write_ty_to_tcx(ccx.tcx, id, fty);
 615
 616     debug!("writing method type: def_id={:?} mty={:?}",
 617             def_id, ty_method);
 618
 619     ccx.tcx.impl_or_trait_items.borrow_mut().insert(def_id,
 620         ty::MethodTraitItem(Rc::new(ty_method)));
 621 }
 622
 623 fn convert_field<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
 624                            struct_generics: &ty::Generics<'tcx>,
 625                            struct_predicates: &ty::GenericPredicates<'tcx>,
 626                            v: &hir::StructField,
 627                            ty_f: ty::FieldDefMaster<'tcx>)
 628 {
 629     let tt = ccx.icx(struct_predicates).to_ty(&ExplicitRscope, &*v.node.ty);
 630     ty_f.fulfill_ty(tt);
 631     write_ty_to_tcx(ccx.tcx, v.node.id, tt);
 632
 633     /* add the field to the tcache */
 634     ccx.tcx.register_item_type(ccx.tcx.map.local_def_id(v.node.id),
 635                                ty::TypeScheme {
 636                                    generics: struct_generics.clone(),
 637                                    ty: tt
 638                                });
 639     ccx.tcx.predicates.borrow_mut().insert(ccx.tcx.map.local_def_id(v.node.id),
 640                                            struct_predicates.clone());
 641 }
 642
 643 fn convert_associated_const<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
 644                                       container: ImplOrTraitItemContainer,
 645                                       name: ast::Name,
 646                                       id: ast::NodeId,
 647                                       vis: hir::Visibility,
 648                                       ty: ty::Ty<'tcx>,
 649                                       has_value: bool)
 650 {
 651     ccx.tcx.predicates.borrow_mut().insert(ccx.tcx.map.local_def_id(id),
 652                                            ty::GenericPredicates::empty());
 653
 654     write_ty_to_tcx(ccx.tcx, id, ty);
 655
 656     let associated_const = Rc::new(ty::AssociatedConst {
 657         name: name,
 658         vis: vis,
 659         def_id: ccx.tcx.map.local_def_id(id),
 660         container: container,
 661         ty: ty,
 662         has_value: has_value
 663     });
 664     ccx.tcx.impl_or_trait_items.borrow_mut()
 665        .insert(ccx.tcx.map.local_def_id(id), ty::ConstTraitItem(associated_const));
 666 }
 667
 668 fn convert_associated_type<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
 669                                      container: ImplOrTraitItemContainer,
 670                                      name: ast::Name,
 671                                      id: ast::NodeId,
 672                                      vis: hir::Visibility,
 673                                      ty: Option<Ty<'tcx>>)
 674 {
 675     let associated_type = Rc::new(ty::AssociatedType {
 676         name: name,
 677         vis: vis,
 678         ty: ty,
 679         def_id: ccx.tcx.map.local_def_id(id),
 680         container: container
 681     });
 682     ccx.tcx.impl_or_trait_items.borrow_mut()
 683        .insert(ccx.tcx.map.local_def_id(id), ty::TypeTraitItem(associated_type));
 684 }
 685
 686 fn convert_methods<'a,'tcx,'i,I>(ccx: &CrateCtxt<'a, 'tcx>,
 687                                  container: ImplOrTraitItemContainer,
 688                                  methods: I,
 689                                  untransformed_rcvr_ty: Ty<'tcx>,
 690                                  rcvr_ty_generics: &ty::Generics<'tcx>,
 691                                  rcvr_ty_predicates: &ty::GenericPredicates<'tcx>)
 692     where I: Iterator<Item=(&'i hir::MethodSig, ast::NodeId, ast::Name, hir::Visibility, Span)>
 693 {
 694     debug!("convert_methods(untransformed_rcvr_ty={:?}, rcvr_ty_generics={:?}, \
 695                             rcvr_ty_predicates={:?})",
 696            untransformed_rcvr_ty,
 697            rcvr_ty_generics,
 698            rcvr_ty_predicates);
 699
 700     for (sig, id, name, vis, _span) in methods {
 701         convert_method(ccx,
 702                        container,
 703                        sig,
 704                        id,
 705                        name,
 706                        vis,
 707                        untransformed_rcvr_ty,
 708                        rcvr_ty_generics,
 709                        rcvr_ty_predicates);
 710     }
 711 }
 712
 713 fn ensure_no_ty_param_bounds(ccx: &CrateCtxt,
 714                                  span: Span,
 715                                  generics: &hir::Generics,
 716                                  thing: &'static str) {
 717     let mut warn = false;
 718
 719     for ty_param in generics.ty_params.iter() {
 720         for bound in ty_param.bounds.iter() {
 721             match *bound {
 722                 hir::TraitTyParamBound(..) => {
 723                     warn = true;
 724                 }
 725                 hir::RegionTyParamBound(..) => { }
 726             }
 727         }
 728     }
 729
 730     if warn {
 731         // According to accepted RFC #XXX, we should
 732         // eventually accept these, but it will not be
 733         // part of this PR. Still, convert to warning to
 734         // make bootstrapping easier.
 735         span_warn!(ccx.tcx.sess, span, E0122,
 736                    "trait bounds are not (yet) enforced \
 737                    in {} definitions",
 738                    thing);
 739     }
 740 }
 741
 742 fn convert_item(ccx: &CrateCtxt, it: &hir::Item) {
 743     let tcx = ccx.tcx;
 744     debug!("convert: item {} with id {}", it.name, it.id);
 745     match it.node {
 746         // These don't define types.
 747         hir::ItemExternCrate(_) | hir::ItemUse(_) |
 748         hir::ItemForeignMod(_) | hir::ItemMod(_) => {
 749         }
 750         hir::ItemEnum(ref enum_definition, _) => {
 751             let (scheme, predicates) = convert_typed_item(ccx, it);
 752             write_ty_to_tcx(tcx, it.id, scheme.ty);
 753             convert_enum_variant_types(ccx,
 754                                        tcx.lookup_adt_def_master(ccx.tcx.map.local_def_id(it.id)),
 755                                        scheme,
 756                                        predicates,
 757                                        &enum_definition.variants);
 758         },
 759         hir::ItemDefaultImpl(_, ref ast_trait_ref) => {
 760             let trait_ref =
 761                 astconv::instantiate_mono_trait_ref(&ccx.icx(&()),
 762                                                     &ExplicitRscope,
 763                                                     ast_trait_ref,
 764                                                     None);
 765
 766             tcx.record_trait_has_default_impl(trait_ref.def_id);
 767
 768             tcx.impl_trait_refs.borrow_mut().insert(ccx.tcx.map.local_def_id(it.id),
 769                                                     Some(trait_ref));
 770         }
 771         hir::ItemImpl(_, _,
 772                       ref generics,
 773                       ref opt_trait_ref,
 774                       ref selfty,
 775                       ref impl_items) => {
 776             // Create generics from the generics specified in the impl head.
 777             debug!("convert: ast_generics={:?}", generics);
 778             let ty_generics = ty_generics_for_type_or_impl(ccx, generics);
 779             let ty_predicates = ty_generic_predicates_for_type_or_impl(ccx, generics);
 780
 781             debug!("convert: impl_bounds={:?}", ty_predicates);
 782
 783             let selfty = ccx.icx(&ty_predicates).to_ty(&ExplicitRscope, &**selfty);
 784             write_ty_to_tcx(tcx, it.id, selfty);
 785
 786             tcx.register_item_type(ccx.tcx.map.local_def_id(it.id),
 787                                    TypeScheme { generics: ty_generics.clone(),
 788                                                 ty: selfty });
 789             tcx.predicates.borrow_mut().insert(ccx.tcx.map.local_def_id(it.id),
 790                                                ty_predicates.clone());
 791             if let &Some(ref ast_trait_ref) = opt_trait_ref {
 792                 tcx.impl_trait_refs.borrow_mut().insert(
 793                     ccx.tcx.map.local_def_id(it.id),
 794                     Some(astconv::instantiate_mono_trait_ref(&ccx.icx(&ty_predicates),
 795                                                              &ExplicitRscope,
 796                                                              ast_trait_ref,
 797                                                              Some(selfty)))
 798                         );
 799             } else {
 800                 tcx.impl_trait_refs.borrow_mut().insert(ccx.tcx.map.local_def_id(it.id), None);
 801             }
 802
 803
 804             // If there is a trait reference, treat the methods as always public.
 805             // This is to work around some incorrect behavior in privacy checking:
 806             // when the method belongs to a trait, it should acquire the privacy
 807             // from the trait, not the impl. Forcing the visibility to be public
 808             // makes things sorta work.
 809             let parent_visibility = if opt_trait_ref.is_some() {
 810                 hir::Public
 811             } else {
 812                 it.vis
 813             };
 814
 815             // Convert all the associated consts.
 816             // Also, check if there are any duplicate associated items
 817             let mut seen_type_items = FnvHashSet();
 818             let mut seen_value_items = FnvHashSet();
 819
 820             for impl_item in impl_items {
 821                 let seen_items = match impl_item.node {
 822                     hir::TypeImplItem(_) => &mut seen_type_items,
 823                     _                    => &mut seen_value_items,
 824                 };
 825                 if !seen_items.insert(impl_item.name) {
 826                     let desc = match impl_item.node {
 827                         hir::ConstImplItem(_, _) => "associated constant",
 828                         hir::TypeImplItem(_) => "associated type",
 829                         hir::MethodImplItem(ref sig, _) =>
 830                             match sig.explicit_self.node {
 831                                 hir::SelfStatic => "associated function",
 832                                 _ => "method",
 833                             },
 834                     };
 835
 836                     span_err!(tcx.sess, impl_item.span, E0201, "duplicate {}", desc);
 837                 }
 838
 839                 if let hir::ConstImplItem(ref ty, _) = impl_item.node {
 840                     let ty = ccx.icx(&ty_predicates)
 841                                 .to_ty(&ExplicitRscope, &*ty);
 842                     tcx.register_item_type(ccx.tcx.map.local_def_id(impl_item.id),
 843                                            TypeScheme {
 844                                                generics: ty_generics.clone(),
 845                                                ty: ty,
 846                                            });
 847                     convert_associated_const(ccx, ImplContainer(ccx.tcx.map.local_def_id(it.id)),
 848                                              impl_item.name, impl_item.id,
 849                                              impl_item.vis.inherit_from(parent_visibility),
 850                                              ty, true /* has_value */);
 851                 }
 852             }
 853
 854             // Convert all the associated types.
 855             for impl_item in impl_items {
 856                 if let hir::TypeImplItem(ref ty) = impl_item.node {
 857                     if opt_trait_ref.is_none() {
 858                         span_err!(tcx.sess, impl_item.span, E0202,
 859                                   "associated types are not allowed in inherent impls");
 860                     }
 861
 862                     let typ = ccx.icx(&ty_predicates).to_ty(&ExplicitRscope, ty);
 863
 864                     convert_associated_type(ccx, ImplContainer(ccx.tcx.map.local_def_id(it.id)),
 865                                             impl_item.name, impl_item.id, impl_item.vis,
 866                                             Some(typ));
 867                 }
 868             }
 869
 870             let methods = impl_items.iter().filter_map(|ii| {
 871                 if let hir::MethodImplItem(ref sig, _) = ii.node {
 872                     // if the method specifies a visibility, use that, otherwise
 873                     // inherit the visibility from the impl (so `foo` in `pub impl
 874                     // { fn foo(); }` is public, but private in `impl { fn
 875                     // foo(); }`).
 876                     let method_vis = ii.vis.inherit_from(parent_visibility);
 877                     Some((sig, ii.id, ii.name, method_vis, ii.span))
 878                 } else {
 879                     None
 880                 }
 881             });
 882             convert_methods(ccx,
 883                             ImplContainer(ccx.tcx.map.local_def_id(it.id)),
 884                             methods,
 885                             selfty,
 886                             &ty_generics,
 887                             &ty_predicates);
 888
 889             for impl_item in impl_items {
 890                 if let hir::MethodImplItem(ref sig, ref body) = impl_item.node {
 891                     let body_id = body.id;
 892                     check_method_self_type(ccx,
 893                                            &BindingRscope::new(),
 894                                            ccx.method_ty(impl_item.id),
 895                                            selfty,
 896                                            &sig.explicit_self,
 897                                            body_id);
 898                 }
 899             }
 900
 901             enforce_impl_params_are_constrained(tcx,
 902                                                 generics,
 903                                                 ccx.tcx.map.local_def_id(it.id),
 904                                                 impl_items);
 905         },
 906         hir::ItemTrait(_, _, _, ref trait_items) => {
 907             let trait_def = trait_def_of_item(ccx, it);
 908             let _: Result<(), ErrorReported> = // any error is already reported, can ignore
 909                 ccx.ensure_super_predicates(it.span, ccx.tcx.map.local_def_id(it.id));
 910             convert_trait_predicates(ccx, it);
 911             let trait_predicates = tcx.lookup_predicates(ccx.tcx.map.local_def_id(it.id));
 912
 913             debug!("convert: trait_bounds={:?}", trait_predicates);
 914
 915             // Convert all the associated types.
 916             for trait_item in trait_items {
 917                 match trait_item.node {
 918                     hir::ConstTraitItem(ref ty, ref default) => {
 919                         let ty = ccx.icx(&trait_predicates)
 920                                     .to_ty(&ExplicitRscope, ty);
 921                         tcx.register_item_type(ccx.tcx.map.local_def_id(trait_item.id),
 922                                                TypeScheme {
 923                                                    generics: trait_def.generics.clone(),
 924                                                    ty: ty,
 925                                                });
 926                         convert_associated_const(ccx,
 927                                                  TraitContainer(ccx.tcx.map.local_def_id(it.id)),
 928                                                  trait_item.name,
 929                                                  trait_item.id,
 930                                                  hir::Public,
 931                                                  ty,
 932                                                  default.is_some())
 933                     }
 934                     _ => {}
 935                 }
 936             };
 937
 938             // Convert all the associated types.
 939             for trait_item in trait_items {
 940                 match trait_item.node {
 941                     hir::TypeTraitItem(_, ref opt_ty) => {
 942                         let typ = opt_ty.as_ref().map({
 943                             |ty| ccx.icx(&trait_predicates).to_ty(&ExplicitRscope, &ty)
 944                         });
 945
 946                         convert_associated_type(ccx,
 947                                                 TraitContainer(ccx.tcx.map.local_def_id(it.id)),
 948                                                 trait_item.name,
 949                                                 trait_item.id,
 950                                                 hir::Public,
 951                                                 typ);
 952                     }
 953                     _ => {}
 954                 }
 955             };
 956
 957             let methods = trait_items.iter().filter_map(|ti| {
 958                 let sig = match ti.node {
 959                     hir::MethodTraitItem(ref sig, _) => sig,
 960                     _ => return None,
 961                 };
 962                 Some((sig, ti.id, ti.name, hir::Inherited, ti.span))
 963             });
 964
 965             // Run convert_methods on the trait methods.
 966             convert_methods(ccx,
 967                             TraitContainer(ccx.tcx.map.local_def_id(it.id)),
 968                             methods,
 969                             tcx.mk_self_type(),
 970                             &trait_def.generics,
 971                             &trait_predicates);
 972
 973             // Add an entry mapping
 974             let trait_item_def_ids = Rc::new(trait_items.iter().map(|trait_item| {
 975                 let def_id = ccx.tcx.map.local_def_id(trait_item.id);
 976                 match trait_item.node {
 977                     hir::ConstTraitItem(..) => {
 978                         ty::ConstTraitItemId(def_id)
 979                     }
 980                     hir::MethodTraitItem(..) => {
 981                         ty::MethodTraitItemId(def_id)
 982                     }
 983                     hir::TypeTraitItem(..) => {
 984                         ty::TypeTraitItemId(def_id)
 985                     }
 986                 }
 987             }).collect());
 988             tcx.trait_item_def_ids.borrow_mut().insert(ccx.tcx.map.local_def_id(it.id),
 989                                                        trait_item_def_ids);
 990
 991             // This must be done after `collect_trait_methods` so that
 992             // we have a method type stored for every method.
 993             for trait_item in trait_items {
 994                 let sig = match trait_item.node {
 995                     hir::MethodTraitItem(ref sig, _) => sig,
 996                     _ => continue
 997                 };
 998                 check_method_self_type(ccx,
 999                                        &BindingRscope::new(),
1000                                        ccx.method_ty(trait_item.id),
1001                                        tcx.mk_self_type(),
1002                                        &sig.explicit_self,
1003                                        it.id)
1004             }
1005         },
1006         hir::ItemStruct(ref struct_def, _) => {
1007             let (scheme, predicates) = convert_typed_item(ccx, it);
1008             write_ty_to_tcx(tcx, it.id, scheme.ty);
1009
1010             let it_def_id = ccx.tcx.map.local_def_id(it.id);
1011             let variant = tcx.lookup_adt_def_master(it_def_id).struct_variant();
1012
1013             for (f, ty_f) in struct_def.fields.iter().zip(variant.fields.iter()) {
1014                 convert_field(ccx, &scheme.generics, &predicates, f, ty_f)
1015             }
1016
1017             if let Some(ctor_id) = struct_def.ctor_id {
1018                 convert_variant_ctor(tcx, ctor_id, variant, scheme, predicates);
1019             }
1020         },
1021         hir::ItemTy(_, ref generics) => {
1022             ensure_no_ty_param_bounds(ccx, it.span, generics, "type");
1023             let (scheme, _) = convert_typed_item(ccx, it);
1024             write_ty_to_tcx(tcx, it.id, scheme.ty);
1025         },
1026         _ => {
1027             // This call populates the type cache with the converted type
1028             // of the item in passing. All we have to do here is to write
1029             // it into the node type table.
1030             let (scheme, _) = convert_typed_item(ccx, it);
1031             write_ty_to_tcx(tcx, it.id, scheme.ty);
1032         },
1033     }
1034 }
1035
1036 fn convert_variant_ctor<'a, 'tcx>(tcx: &ty::ctxt<'tcx>,
1037                                   ctor_id: ast::NodeId,
1038                                   variant: ty::VariantDef<'tcx>,
1039                                   scheme: ty::TypeScheme<'tcx>,
1040                                   predicates: ty::GenericPredicates<'tcx>) {
1041     let ctor_ty = match variant.kind() {
1042         VariantKind::Unit | VariantKind::Dict => scheme.ty,
1043         VariantKind::Tuple => {
1044             let inputs: Vec<_> =
1045                 variant.fields
1046                 .iter()
1047                 .map(|field| field.unsubst_ty())
1048                 .collect();
1049             tcx.mk_ctor_fn(tcx.map.local_def_id(ctor_id),
1050                            &inputs[..],
1051                            scheme.ty)
1052         }
1053     };
1054     write_ty_to_tcx(tcx, ctor_id, ctor_ty);
1055     tcx.predicates.borrow_mut().insert(tcx.map.local_def_id(ctor_id), predicates);
1056     tcx.register_item_type(tcx.map.local_def_id(ctor_id),
1057                            TypeScheme {
1058                                generics: scheme.generics,
1059                                ty: ctor_ty
1060                            });
1061 }
1062
1063 fn convert_enum_variant_types<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
1064                                         def: ty::AdtDefMaster<'tcx>,
1065                                         scheme: ty::TypeScheme<'tcx>,
1066                                         predicates: ty::GenericPredicates<'tcx>,
1067                                         variants: &[P<hir::Variant>]) {
1068     let tcx = ccx.tcx;
1069     let icx = ccx.icx(&predicates);
1070
1071     // fill the field types
1072     for (variant, ty_variant) in variants.iter().zip(def.variants.iter()) {
1073         match variant.node.kind {
1074             hir::TupleVariantKind(ref args) => {
1075                 let rs = ExplicitRscope;
1076                 let input_tys: Vec<_> = args.iter().map(|va| icx.to_ty(&rs, &*va.ty)).collect();
1077                 for (field, &ty) in ty_variant.fields.iter().zip(input_tys.iter()) {
1078                     field.fulfill_ty(ty);
1079                 }
1080             }
1081
1082             hir::StructVariantKind(ref struct_def) => {
1083                 for (f, ty_f) in struct_def.fields.iter().zip(ty_variant.fields.iter()) {
1084                     convert_field(ccx, &scheme.generics, &predicates, f, ty_f)
1085                 }
1086             }
1087         };
1088
1089         // Convert the ctor, if any. This also registers the variant as
1090         // an item.
1091         convert_variant_ctor(
1092             tcx,
1093             variant.node.id,
1094             ty_variant,
1095             scheme.clone(),
1096             predicates.clone()
1097         );
1098     }
1099 }
1100
1101 fn convert_struct_variant<'tcx>(tcx: &ty::ctxt<'tcx>,
1102                                 did: DefId,
1103                                 name: ast::Name,
1104                                 disr_val: ty::Disr,
1105                                 def: &hir::StructDef) -> ty::VariantDefData<'tcx, 'tcx> {
1106     let mut seen_fields: FnvHashMap<ast::Name, Span> = FnvHashMap();
1107     let fields = def.fields.iter().map(|f| {
1108         let fid = tcx.map.local_def_id(f.node.id);
1109         match f.node.kind {
1110             hir::NamedField(name, vis) => {
1111                 let dup_span = seen_fields.get(&name).cloned();
1112                 if let Some(prev_span) = dup_span {
1113                     span_err!(tcx.sess, f.span, E0124,
1114                               "field `{}` is already declared",
1115                               name);
1116                     span_note!(tcx.sess, prev_span, "previously declared here");
1117                 } else {
1118                     seen_fields.insert(name, f.span);
1119                 }
1120
1121                 ty::FieldDefData::new(fid, name, vis)
1122             },
1123             hir::UnnamedField(vis) => {
1124                 ty::FieldDefData::new(fid, special_idents::unnamed_field.name, vis)
1125             }
1126         }
1127     }).collect();
1128     ty::VariantDefData {
1129         did: did,
1130         name: name,
1131         disr_val: disr_val,
1132         fields: fields
1133     }
1134 }
1135
1136 fn convert_struct_def<'tcx>(tcx: &ty::ctxt<'tcx>,
1137                             it: &hir::Item,
1138                             def: &hir::StructDef)
1139                             -> ty::AdtDefMaster<'tcx>
1140 {
1141
1142     let did = tcx.map.local_def_id(it.id);
1143     tcx.intern_adt_def(
1144         did,
1145         ty::AdtKind::Struct,
1146         vec![convert_struct_variant(tcx, did, it.name, 0, def)]
1147     )
1148 }
1149
1150 fn convert_enum_def<'tcx>(tcx: &ty::ctxt<'tcx>,
1151                           it: &hir::Item,
1152                           def: &hir::EnumDef)
1153                           -> ty::AdtDefMaster<'tcx>
1154 {
1155     fn evaluate_disr_expr<'tcx>(tcx: &ty::ctxt<'tcx>,
1156                                 repr_ty: Ty<'tcx>,
1157                                 e: &hir::Expr) -> Option<ty::Disr> {
1158         debug!("disr expr, checking {}", pprust::expr_to_string(e));
1159
1160         let hint = UncheckedExprHint(repr_ty);
1161         match const_eval::eval_const_expr_partial(tcx, e, hint) {
1162             Ok(ConstVal::Int(val)) => Some(val as ty::Disr),
1163             Ok(ConstVal::Uint(val)) => Some(val as ty::Disr),
1164             Ok(_) => {
1165                 let sign_desc = if repr_ty.is_signed() {
1166                     "signed"
1167                 } else {
1168                     "unsigned"
1169                 };
1170                 span_err!(tcx.sess, e.span, E0079,
1171                           "expected {} integer constant",
1172                           sign_desc);
1173                 None
1174             },
1175             Err(err) => {
1176                 span_err!(tcx.sess, err.span, E0080,
1177                           "constant evaluation error: {}",
1178                           err.description());
1179                 if !e.span.contains(err.span) {
1180                     tcx.sess.span_note(e.span, "for enum discriminant here");
1181                 }
1182                 None
1183             }
1184         }
1185     }
1186
1187     fn report_discrim_overflow(tcx: &ty::ctxt,
1188                                variant_span: Span,
1189                                variant_name: &str,
1190                                repr_type: attr::IntType,
1191                                prev_val: ty::Disr) {
1192         let computed_value = repr_type.disr_wrap_incr(Some(prev_val));
1193         let computed_value = repr_type.disr_string(computed_value);
1194         let prev_val = repr_type.disr_string(prev_val);
1195         let repr_type = repr_type.to_ty(tcx);
1196         span_err!(tcx.sess, variant_span, E0370,
1197                   "enum discriminant overflowed on value after {}: {}; \
1198                    set explicitly via {} = {} if that is desired outcome",
1199                   prev_val, repr_type, variant_name, computed_value);
1200     }
1201
1202     fn next_disr(tcx: &ty::ctxt,
1203                  v: &hir::Variant,
1204                  repr_type: attr::IntType,
1205                  prev_disr_val: Option<ty::Disr>) -> Option<ty::Disr> {
1206         if let Some(prev_disr_val) = prev_disr_val {
1207             let result = repr_type.disr_incr(prev_disr_val);
1208             if let None = result {
1209                 report_discrim_overflow(tcx, v.span, &v.node.name.as_str(),
1210                                              repr_type, prev_disr_val);
1211             }
1212             result
1213         } else {
1214             Some(ty::INITIAL_DISCRIMINANT_VALUE)
1215         }
1216     }
1217     fn convert_enum_variant<'tcx>(tcx: &ty::ctxt<'tcx>,
1218                                   v: &hir::Variant,
1219                                   disr: ty::Disr)
1220                                   -> ty::VariantDefData<'tcx, 'tcx>
1221     {
1222         let did = tcx.map.local_def_id(v.node.id);
1223         let name = v.node.name;
1224         match v.node.kind {
1225             hir::TupleVariantKind(ref va) => {
1226                 ty::VariantDefData {
1227                     did: did,
1228                     name: name,
1229                     disr_val: disr,
1230                     fields: va.iter().map(|&hir::VariantArg { id, .. }| {
1231                         ty::FieldDefData::new(
1232                             tcx.map.local_def_id(id),
1233                             special_idents::unnamed_field.name,
1234                             hir::Visibility::Public
1235                         )
1236                     }).collect()
1237                 }
1238             }
1239             hir::StructVariantKind(ref def) => {
1240                 convert_struct_variant(tcx, did, name, disr, &def)
1241             }
1242         }
1243     }
1244     let did = tcx.map.local_def_id(it.id);
1245     let repr_hints = tcx.lookup_repr_hints(did);
1246     let (repr_type, repr_type_ty) = tcx.enum_repr_type(repr_hints.get(0));
1247     let mut prev_disr = None;
1248     let variants = def.variants.iter().map(|v| {
1249         let disr = match v.node.disr_expr {
1250             Some(ref e) => evaluate_disr_expr(tcx, repr_type_ty, e),
1251             None => next_disr(tcx, v, repr_type, prev_disr)
1252         }.unwrap_or(repr_type.disr_wrap_incr(prev_disr));
1253
1254         let v = convert_enum_variant(tcx, v, disr);
1255         prev_disr = Some(disr);
1256         v
1257     }).collect();
1258     tcx.intern_adt_def(tcx.map.local_def_id(it.id), ty::AdtKind::Enum, variants)
1259 }
1260
1261 /// Ensures that the super-predicates of the trait with def-id
1262 /// trait_def_id are converted and stored. This does NOT ensure that
1263 /// the transitive super-predicates are converted; that is the job of
1264 /// the `ensure_super_predicates()` method in the `AstConv` impl
1265 /// above. Returns a list of trait def-ids that must be ensured as
1266 /// well to guarantee that the transitive superpredicates are
1267 /// converted.
1268 fn ensure_super_predicates_step(ccx: &CrateCtxt,
1269                                 trait_def_id: DefId)
1270                                 -> Vec<DefId>
1271 {
1272     let tcx = ccx.tcx;
1273
1274     debug!("ensure_super_predicates_step(trait_def_id={:?})", trait_def_id);
1275
1276     let trait_node_id = if let Some(n) = tcx.map.as_local_node_id(trait_def_id) {
1277         n
1278     } else {
1279         // If this trait comes from an external crate, then all of the
1280         // supertraits it may depend on also must come from external
1281         // crates, and hence all of them already have their
1282         // super-predicates "converted" (and available from crate
1283         // meta-data), so there is no need to transitively test them.
1284         return Vec::new();
1285     };
1286
1287     let superpredicates = tcx.super_predicates.borrow().get(&trait_def_id).cloned();
1288     let superpredicates = superpredicates.unwrap_or_else(|| {
1289         let item = match ccx.tcx.map.get(trait_node_id) {
1290             hir_map::NodeItem(item) => item,
1291             _ => ccx.tcx.sess.bug(&format!("trait_node_id {} is not an item", trait_node_id))
1292         };
1293
1294         let (generics, bounds) = match item.node {
1295             hir::ItemTrait(_, ref generics, ref supertraits, _) => (generics, supertraits),
1296             _ => tcx.sess.span_bug(item.span,
1297                                    "ensure_super_predicates_step invoked on non-trait"),
1298         };
1299
1300         // In-scope when converting the superbounds for `Trait` are
1301         // that `Self:Trait` as well as any bounds that appear on the
1302         // generic types:
1303         let trait_def = trait_def_of_item(ccx, item);
1304         let self_predicate = ty::GenericPredicates {
1305             predicates: VecPerParamSpace::new(vec![],
1306                                               vec![trait_def.trait_ref.to_predicate()],
1307                                               vec![])
1308         };
1309         let scope = &(generics, &self_predicate);
1310
1311         // Convert the bounds that follow the colon, e.g. `Bar+Zed` in `trait Foo : Bar+Zed`.
1312         let self_param_ty = tcx.mk_self_type();
1313         let superbounds1 = compute_bounds(&ccx.icx(scope),
1314                                     self_param_ty,
1315                                     bounds,
1316                                     SizedByDefault::No,
1317                                     item.span);
1318
1319         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1320
1321         // Convert any explicit superbounds in the where clause,
1322         // e.g. `trait Foo where Self : Bar`:
1323         let superbounds2 = generics.get_type_parameter_bounds(&ccx.icx(scope), item.span, item.id);
1324
1325         // Combine the two lists to form the complete set of superbounds:
1326         let superbounds = superbounds1.into_iter().chain(superbounds2).collect();
1327         let superpredicates = ty::GenericPredicates {
1328             predicates: VecPerParamSpace::new(superbounds, vec![], vec![])
1329         };
1330         debug!("superpredicates for trait {:?} = {:?}",
1331                tcx.map.local_def_id(item.id),
1332                superpredicates);
1333
1334         tcx.super_predicates.borrow_mut().insert(trait_def_id, superpredicates.clone());
1335
1336         superpredicates
1337     });
1338
1339     let def_ids: Vec<_> = superpredicates.predicates
1340                                          .iter()
1341                                          .filter_map(|p| p.to_opt_poly_trait_ref())
1342                                          .map(|tr| tr.def_id())
1343                                          .collect();
1344
1345     debug!("ensure_super_predicates_step: def_ids={:?}", def_ids);
1346
1347     def_ids
1348 }
1349
1350 fn trait_def_of_item<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
1351                                it: &hir::Item)
1352                                -> &'tcx ty::TraitDef<'tcx>
1353 {
1354     let def_id = ccx.tcx.map.local_def_id(it.id);
1355     let tcx = ccx.tcx;
1356
1357     if let Some(def) = tcx.trait_defs.borrow().get(&def_id) {
1358         return def.clone();
1359     }
1360
1361     let (unsafety, generics, items) = match it.node {
1362         hir::ItemTrait(unsafety, ref generics, _, ref items) => (unsafety, generics, items),
1363         _ => tcx.sess.span_bug(it.span, "trait_def_of_item invoked on non-trait"),
1364     };
1365
1366     let paren_sugar = tcx.has_attr(def_id, "rustc_paren_sugar");
1367     if paren_sugar && !ccx.tcx.sess.features.borrow().unboxed_closures {
1368         ccx.tcx.sess.span_err(
1369             it.span,
1370             "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1371              which traits can use parenthetical notation");
1372         fileline_help!(ccx.tcx.sess, it.span,
1373                    "add `#![feature(unboxed_closures)]` to \
1374                     the crate attributes to use it");
1375     }
1376
1377     let substs = ccx.tcx.mk_substs(mk_trait_substs(ccx, generics));
1378
1379     let ty_generics = ty_generics_for_trait(ccx, it.id, substs, generics);
1380
1381     let associated_type_names: Vec<_> = items.iter().filter_map(|trait_item| {
1382         match trait_item.node {
1383             hir::TypeTraitItem(..) => Some(trait_item.name),
1384             _ => None,
1385         }
1386     }).collect();
1387
1388     let trait_ref = ty::TraitRef {
1389         def_id: def_id,
1390         substs: substs,
1391     };
1392
1393     let trait_def = ty::TraitDef {
1394         paren_sugar: paren_sugar,
1395         unsafety: unsafety,
1396         generics: ty_generics,
1397         trait_ref: trait_ref,
1398         associated_type_names: associated_type_names,
1399         nonblanket_impls: RefCell::new(FnvHashMap()),
1400         blanket_impls: RefCell::new(vec![]),
1401         flags: Cell::new(ty::TraitFlags::NO_TRAIT_FLAGS)
1402     };
1403
1404     return tcx.intern_trait_def(trait_def);
1405
1406     fn mk_trait_substs<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
1407                                  generics: &hir::Generics)
1408                                  -> Substs<'tcx>
1409     {
1410         let tcx = ccx.tcx;
1411
1412         // Creates a no-op substitution for the trait's type parameters.
1413         let regions =
1414             generics.lifetimes
1415                     .iter()
1416                     .enumerate()
1417                     .map(|(i, def)| ty::ReEarlyBound(ty::EarlyBoundRegion {
1418                         def_id: tcx.map.local_def_id(def.lifetime.id),
1419                         space: TypeSpace,
1420                         index: i as u32,
1421                         name: def.lifetime.name
1422                     }))
1423                     .collect();
1424
1425         // Start with the generics in the type parameters...
1426         let types: Vec<_> =
1427             generics.ty_params
1428                     .iter()
1429                     .enumerate()
1430                     .map(|(i, def)| tcx.mk_param(TypeSpace,
1431                                                  i as u32, def.name))
1432                     .collect();
1433
1434         // ...and also create the `Self` parameter.
1435         let self_ty = tcx.mk_self_type();
1436
1437         Substs::new_trait(types, regions, self_ty)
1438     }
1439 }
1440
1441 fn trait_defines_associated_type_named(ccx: &CrateCtxt,
1442                                        trait_node_id: ast::NodeId,
1443                                        assoc_name: ast::Name)
1444                                        -> bool
1445 {
1446     let item = match ccx.tcx.map.get(trait_node_id) {
1447         hir_map::NodeItem(item) => item,
1448         _ => ccx.tcx.sess.bug(&format!("trait_node_id {} is not an item", trait_node_id))
1449     };
1450
1451     let trait_items = match item.node {
1452         hir::ItemTrait(_, _, _, ref trait_items) => trait_items,
1453         _ => ccx.tcx.sess.bug(&format!("trait_node_id {} is not a trait", trait_node_id))
1454     };
1455
1456     trait_items.iter().any(|trait_item| {
1457         match trait_item.node {
1458             hir::TypeTraitItem(..) => trait_item.name == assoc_name,
1459             _ => false,
1460         }
1461     })
1462 }
1463
1464 fn convert_trait_predicates<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>, it: &hir::Item) {
1465     let tcx = ccx.tcx;
1466     let trait_def = trait_def_of_item(ccx, it);
1467
1468     let def_id = ccx.tcx.map.local_def_id(it.id);
1469
1470     let (generics, items) = match it.node {
1471         hir::ItemTrait(_, ref generics, _, ref items) => (generics, items),
1472         ref s => {
1473             tcx.sess.span_bug(
1474                 it.span,
1475                 &format!("trait_def_of_item invoked on {:?}", s));
1476         }
1477     };
1478
1479     let super_predicates = ccx.tcx.lookup_super_predicates(def_id);
1480
1481     // `ty_generic_predicates` below will consider the bounds on the type
1482     // parameters (including `Self`) and the explicit where-clauses,
1483     // but to get the full set of predicates on a trait we need to add
1484     // in the supertrait bounds and anything declared on the
1485     // associated types.
1486     let mut base_predicates = super_predicates;
1487
1488     // Add in a predicate that `Self:Trait` (where `Trait` is the
1489     // current trait).  This is needed for builtin bounds.
1490     let self_predicate = trait_def.trait_ref.to_poly_trait_ref().to_predicate();
1491     base_predicates.predicates.push(SelfSpace, self_predicate);
1492
1493     // add in the explicit where-clauses
1494     let mut trait_predicates =
1495         ty_generic_predicates(ccx, TypeSpace, generics, &base_predicates);
1496
1497     let assoc_predicates = predicates_for_associated_types(ccx,
1498                                                            generics,
1499                                                            &trait_predicates,
1500                                                            trait_def.trait_ref,
1501                                                            items);
1502     trait_predicates.predicates.extend(TypeSpace, assoc_predicates.into_iter());
1503
1504     let prev_predicates = tcx.predicates.borrow_mut().insert(def_id, trait_predicates);
1505     assert!(prev_predicates.is_none());
1506
1507     return;
1508
1509     fn predicates_for_associated_types<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
1510                                                  ast_generics: &hir::Generics,
1511                                                  trait_predicates: &ty::GenericPredicates<'tcx>,
1512                                                  self_trait_ref: ty::TraitRef<'tcx>,
1513                                                  trait_items: &[P<hir::TraitItem>])
1514                                                  -> Vec<ty::Predicate<'tcx>>
1515     {
1516         trait_items.iter().flat_map(|trait_item| {
1517             let bounds = match trait_item.node {
1518                 hir::TypeTraitItem(ref bounds, _) => bounds,
1519                 _ => {
1520                     return vec!().into_iter();
1521                 }
1522             };
1523
1524             let assoc_ty = ccx.tcx.mk_projection(self_trait_ref,
1525                                                  trait_item.name);
1526
1527             let bounds = compute_bounds(&ccx.icx(&(ast_generics, trait_predicates)),
1528                                         assoc_ty,
1529                                         bounds,
1530                                         SizedByDefault::Yes,
1531                                         trait_item.span);
1532
1533             bounds.predicates(ccx.tcx, assoc_ty).into_iter()
1534         }).collect()
1535     }
1536 }
1537
1538 fn type_scheme_of_def_id<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>,
1539                                   def_id: DefId)
1540                                   -> ty::TypeScheme<'tcx>
1541 {
1542     if let Some(node_id) = ccx.tcx.map.as_local_node_id(def_id) {
1543         match ccx.tcx.map.find(node_id) {
1544             Some(hir_map::NodeItem(item)) => {
1545                 type_scheme_of_item(ccx, &*item)
1546             }
1547             Some(hir_map::NodeForeignItem(foreign_item)) => {
1548                 let abi = ccx.tcx.map.get_foreign_abi(node_id);
1549                 type_scheme_of_foreign_item(ccx, &*foreign_item, abi)
1550             }
1551             x => {
1552                 ccx.tcx.sess.bug(&format!("unexpected sort of node \
1553                                            in get_item_type_scheme(): {:?}",
1554                                           x));
1555             }
1556         }
1557     } else {
1558         ccx.tcx.lookup_item_type(def_id)
1559     }
1560 }
1561
1562 fn type_scheme_of_item<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>,
1563                                 it: &hir::Item)
1564                                 -> ty::TypeScheme<'tcx>
1565 {
1566     memoized(&ccx.tcx.tcache,
1567              ccx.tcx.map.local_def_id(it.id),
1568              |_| compute_type_scheme_of_item(ccx, it))
1569 }
1570
1571 fn compute_type_scheme_of_item<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>,
1572                                         it: &hir::Item)
1573                                         -> ty::TypeScheme<'tcx>
1574 {
1575     let tcx = ccx.tcx;
1576     match it.node {
1577         hir::ItemStatic(ref t, _, _) | hir::ItemConst(ref t, _) => {
1578             let ty = ccx.icx(&()).to_ty(&ExplicitRscope, &**t);
1579             ty::TypeScheme { ty: ty, generics: ty::Generics::empty() }
1580         }
1581         hir::ItemFn(ref decl, unsafety, _, abi, ref generics, _) => {
1582             let ty_generics = ty_generics_for_fn(ccx, generics, &ty::Generics::empty());
1583             let tofd = astconv::ty_of_bare_fn(&ccx.icx(generics), unsafety, abi, &**decl);
1584             let ty = tcx.mk_fn(Some(ccx.tcx.map.local_def_id(it.id)), tcx.mk_bare_fn(tofd));
1585             ty::TypeScheme { ty: ty, generics: ty_generics }
1586         }
1587         hir::ItemTy(ref t, ref generics) => {
1588             let ty_generics = ty_generics_for_type_or_impl(ccx, generics);
1589             let ty = ccx.icx(generics).to_ty(&ExplicitRscope, &**t);
1590             ty::TypeScheme { ty: ty, generics: ty_generics }
1591         }
1592         hir::ItemEnum(ref ei, ref generics) => {
1593             let ty_generics = ty_generics_for_type_or_impl(ccx, generics);
1594             let substs = mk_item_substs(ccx, &ty_generics);
1595             let def = convert_enum_def(tcx, it, ei);
1596             let t = tcx.mk_enum(def, tcx.mk_substs(substs));
1597             ty::TypeScheme { ty: t, generics: ty_generics }
1598         }
1599         hir::ItemStruct(ref si, ref generics) => {
1600             let ty_generics = ty_generics_for_type_or_impl(ccx, generics);
1601             let substs = mk_item_substs(ccx, &ty_generics);
1602             let def = convert_struct_def(tcx, it, si);
1603             let t = tcx.mk_struct(def, tcx.mk_substs(substs));
1604             ty::TypeScheme { ty: t, generics: ty_generics }
1605         }
1606         hir::ItemDefaultImpl(..) |
1607         hir::ItemTrait(..) |
1608         hir::ItemImpl(..) |
1609         hir::ItemMod(..) |
1610         hir::ItemForeignMod(..) |
1611         hir::ItemExternCrate(..) |
1612         hir::ItemUse(..) => {
1613             tcx.sess.span_bug(
1614                 it.span,
1615                 &format!("compute_type_scheme_of_item: unexpected item type: {:?}",
1616                          it.node));
1617         }
1618     }
1619 }
1620
1621 fn convert_typed_item<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
1622                                 it: &hir::Item)
1623                                 -> (ty::TypeScheme<'tcx>, ty::GenericPredicates<'tcx>)
1624 {
1625     let tcx = ccx.tcx;
1626
1627     let tag = type_scheme_of_item(ccx, it);
1628     let scheme = TypeScheme { generics: tag.generics, ty: tag.ty };
1629     let predicates = match it.node {
1630         hir::ItemStatic(..) | hir::ItemConst(..) => {
1631             ty::GenericPredicates::empty()
1632         }
1633         hir::ItemFn(_, _, _, _, ref ast_generics, _) => {
1634             ty_generic_predicates_for_fn(ccx, ast_generics, &ty::GenericPredicates::empty())
1635         }
1636         hir::ItemTy(_, ref generics) => {
1637             ty_generic_predicates_for_type_or_impl(ccx, generics)
1638         }
1639         hir::ItemEnum(_, ref generics) => {
1640             ty_generic_predicates_for_type_or_impl(ccx, generics)
1641         }
1642         hir::ItemStruct(_, ref generics) => {
1643             ty_generic_predicates_for_type_or_impl(ccx, generics)
1644         }
1645         hir::ItemDefaultImpl(..) |
1646         hir::ItemTrait(..) |
1647         hir::ItemExternCrate(..) |
1648         hir::ItemUse(..) |
1649         hir::ItemImpl(..) |
1650         hir::ItemMod(..) |
1651         hir::ItemForeignMod(..) => {
1652             tcx.sess.span_bug(
1653                 it.span,
1654                 &format!("compute_type_scheme_of_item: unexpected item type: {:?}",
1655                          it.node));
1656         }
1657     };
1658
1659     let prev_predicates = tcx.predicates.borrow_mut().insert(ccx.tcx.map.local_def_id(it.id),
1660                                                              predicates.clone());
1661     assert!(prev_predicates.is_none());
1662
1663     // Debugging aid.
1664     if tcx.has_attr(ccx.tcx.map.local_def_id(it.id), "rustc_object_lifetime_default") {
1665         let object_lifetime_default_reprs: String =
1666             scheme.generics.types.iter()
1667                                  .map(|t| match t.object_lifetime_default {
1668                                      ty::ObjectLifetimeDefault::Specific(r) => r.to_string(),
1669                                      d => format!("{:?}", d),
1670                                  })
1671                                  .collect::<Vec<String>>()
1672                                  .join(",");
1673
1674         tcx.sess.span_err(it.span, &object_lifetime_default_reprs);
1675     }
1676
1677     return (scheme, predicates);
1678 }
1679
1680 fn type_scheme_of_foreign_item<'a, 'tcx>(
1681     ccx: &CrateCtxt<'a, 'tcx>,
1682     it: &hir::ForeignItem,
1683     abi: abi::Abi)
1684     -> ty::TypeScheme<'tcx>
1685 {
1686     memoized(&ccx.tcx.tcache,
1687              ccx.tcx.map.local_def_id(it.id),
1688              |_| compute_type_scheme_of_foreign_item(ccx, it, abi))
1689 }
1690
1691 fn compute_type_scheme_of_foreign_item<'a, 'tcx>(
1692     ccx: &CrateCtxt<'a, 'tcx>,
1693     it: &hir::ForeignItem,
1694     abi: abi::Abi)
1695     -> ty::TypeScheme<'tcx>
1696 {
1697     match it.node {
1698         hir::ForeignItemFn(ref fn_decl, ref generics) => {
1699             compute_type_scheme_of_foreign_fn_decl(ccx, fn_decl, generics, abi)
1700         }
1701         hir::ForeignItemStatic(ref t, _) => {
1702             ty::TypeScheme {
1703                 generics: ty::Generics::empty(),
1704                 ty: ast_ty_to_ty(&ccx.icx(&()), &ExplicitRscope, t)
1705             }
1706         }
1707     }
1708 }
1709
1710 fn convert_foreign_item<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
1711                                   it: &hir::ForeignItem)
1712 {
1713     // For reasons I cannot fully articulate, I do so hate the AST
1714     // map, and I regard each time that I use it as a personal and
1715     // moral failing, but at the moment it seems like the only
1716     // convenient way to extract the ABI. - ndm
1717     let tcx = ccx.tcx;
1718     let abi = tcx.map.get_foreign_abi(it.id);
1719
1720     let scheme = type_scheme_of_foreign_item(ccx, it, abi);
1721     write_ty_to_tcx(ccx.tcx, it.id, scheme.ty);
1722
1723     let predicates = match it.node {
1724         hir::ForeignItemFn(_, ref generics) => {
1725             ty_generic_predicates_for_fn(ccx, generics, &ty::GenericPredicates::empty())
1726         }
1727         hir::ForeignItemStatic(..) => {
1728             ty::GenericPredicates::empty()
1729         }
1730     };
1731
1732     let prev_predicates = tcx.predicates.borrow_mut().insert(ccx.tcx.map.local_def_id(it.id),
1733                                                              predicates);
1734     assert!(prev_predicates.is_none());
1735 }
1736
1737 fn ty_generics_for_type_or_impl<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
1738                                           generics: &hir::Generics)
1739                                           -> ty::Generics<'tcx> {
1740     ty_generics(ccx, TypeSpace, generics, &ty::Generics::empty())
1741 }
1742
1743 fn ty_generic_predicates_for_type_or_impl<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>,
1744                                                    generics: &hir::Generics)
1745                                                    -> ty::GenericPredicates<'tcx>
1746 {
1747     ty_generic_predicates(ccx, TypeSpace, generics, &ty::GenericPredicates::empty())
1748 }
1749
1750 fn ty_generics_for_trait<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
1751                                    trait_id: ast::NodeId,
1752                                    substs: &'tcx Substs<'tcx>,
1753                                    ast_generics: &hir::Generics)
1754                                    -> ty::Generics<'tcx>
1755 {
1756     debug!("ty_generics_for_trait(trait_id={:?}, substs={:?})",
1757            ccx.tcx.map.local_def_id(trait_id), substs);
1758
1759     let mut generics = ty_generics_for_type_or_impl(ccx, ast_generics);
1760
1761     // Add in the self type parameter.
1762     //
1763     // Something of a hack: use the node id for the trait, also as
1764     // the node id for the Self type parameter.
1765     let param_id = trait_id;
1766
1767     let parent = ccx.tcx.map.get_parent(param_id);
1768
1769     let def = ty::TypeParameterDef {
1770         space: SelfSpace,
1771         index: 0,
1772         name: special_idents::type_self.name,
1773         def_id: ccx.tcx.map.local_def_id(param_id),
1774         default_def_id: ccx.tcx.map.local_def_id(parent),
1775         default: None,
1776         object_lifetime_default: ty::ObjectLifetimeDefault::BaseDefault,
1777     };
1778
1779     ccx.tcx.ty_param_defs.borrow_mut().insert(param_id, def.clone());
1780
1781     generics.types.push(SelfSpace, def);
1782
1783     return generics;
1784 }
1785
1786 fn ty_generics_for_fn<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>,
1787                                generics: &hir::Generics,
1788                                base_generics: &ty::Generics<'tcx>)
1789                                -> ty::Generics<'tcx>
1790 {
1791     ty_generics(ccx, FnSpace, generics, base_generics)
1792 }
1793
1794 fn ty_generic_predicates_for_fn<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>,
1795                                          generics: &hir::Generics,
1796                                          base_predicates: &ty::GenericPredicates<'tcx>)
1797                                          -> ty::GenericPredicates<'tcx>
1798 {
1799     ty_generic_predicates(ccx, FnSpace, generics, base_predicates)
1800 }
1801
1802 // Add the Sized bound, unless the type parameter is marked as `?Sized`.
1803 fn add_unsized_bound<'tcx>(astconv: &AstConv<'tcx>,
1804                            bounds: &mut ty::BuiltinBounds,
1805                            ast_bounds: &[hir::TyParamBound],
1806                            span: Span)
1807 {
1808     let tcx = astconv.tcx();
1809
1810     // Try to find an unbound in bounds.
1811     let mut unbound = None;
1812     for ab in ast_bounds {
1813         if let &hir::TraitTyParamBound(ref ptr, hir::TraitBoundModifier::Maybe) = ab  {
1814             if unbound.is_none() {
1815                 assert!(ptr.bound_lifetimes.is_empty());
1816                 unbound = Some(ptr.trait_ref.clone());
1817             } else {
1818                 span_err!(tcx.sess, span, E0203,
1819                           "type parameter has more than one relaxed default \
1820                                                 bound, only one is supported");
1821             }
1822         }
1823     }
1824
1825     let kind_id = tcx.lang_items.require(SizedTraitLangItem);
1826     match unbound {
1827         Some(ref tpb) => {
1828             // FIXME(#8559) currently requires the unbound to be built-in.
1829             let trait_def_id = tcx.trait_ref_to_def_id(tpb);
1830             match kind_id {
1831                 Ok(kind_id) if trait_def_id != kind_id => {
1832                     tcx.sess.span_warn(span,
1833                                        "default bound relaxed for a type parameter, but \
1834                                        this does nothing because the given bound is not \
1835                                        a default. Only `?Sized` is supported");
1836                     tcx.try_add_builtin_trait(kind_id, bounds);
1837                 }
1838                 _ => {}
1839             }
1840         }
1841         _ if kind_id.is_ok() => {
1842             tcx.try_add_builtin_trait(kind_id.unwrap(), bounds);
1843         }
1844         // No lang item for Sized, so we can't add it as a bound.
1845         None => {}
1846     }
1847 }
1848
1849 /// Returns the early-bound lifetimes declared in this generics
1850 /// listing.  For anything other than fns/methods, this is just all
1851 /// the lifetimes that are declared. For fns or methods, we have to
1852 /// screen out those that do not appear in any where-clauses etc using
1853 /// `resolve_lifetime::early_bound_lifetimes`.
1854 fn early_bound_lifetimes_from_generics(space: ParamSpace,
1855                                        ast_generics: &hir::Generics)
1856                                        -> Vec<hir::LifetimeDef>
1857 {
1858     match space {
1859         SelfSpace | TypeSpace => ast_generics.lifetimes.to_vec(),
1860         FnSpace => resolve_lifetime::early_bound_lifetimes(ast_generics),
1861     }
1862 }
1863
1864 fn ty_generic_predicates<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>,
1865                                   space: ParamSpace,
1866                                   ast_generics: &hir::Generics,
1867                                   base_predicates: &ty::GenericPredicates<'tcx>)
1868                                   -> ty::GenericPredicates<'tcx>
1869 {
1870     let tcx = ccx.tcx;
1871     let mut result = base_predicates.clone();
1872
1873     // Collect the predicates that were written inline by the user on each
1874     // type parameter (e.g., `<T:Foo>`).
1875     for (index, param) in ast_generics.ty_params.iter().enumerate() {
1876         let index = index as u32;
1877         let param_ty = ty::ParamTy::new(space, index, param.name).to_ty(ccx.tcx);
1878         let bounds = compute_bounds(&ccx.icx(&(base_predicates, ast_generics)),
1879                                     param_ty,
1880                                     &param.bounds,
1881                                     SizedByDefault::Yes,
1882                                     param.span);
1883         let predicates = bounds.predicates(ccx.tcx, param_ty);
1884         result.predicates.extend(space, predicates.into_iter());
1885     }
1886
1887     // Collect the region predicates that were declared inline as
1888     // well. In the case of parameters declared on a fn or method, we
1889     // have to be careful to only iterate over early-bound regions.
1890     let early_lifetimes = early_bound_lifetimes_from_generics(space, ast_generics);
1891     for (index, param) in early_lifetimes.iter().enumerate() {
1892         let index = index as u32;
1893         let def_id = tcx.map.local_def_id(param.lifetime.id);
1894         let region =
1895             ty::ReEarlyBound(ty::EarlyBoundRegion {
1896                 def_id: def_id,
1897                 space: space,
1898                 index: index,
1899                 name: param.lifetime.name
1900             });
1901         for bound in &param.bounds {
1902             let bound_region = ast_region_to_region(ccx.tcx, bound);
1903             let outlives = ty::Binder(ty::OutlivesPredicate(region, bound_region));
1904             result.predicates.push(space, outlives.to_predicate());
1905         }
1906     }
1907
1908     // Add in the bounds that appear in the where-clause
1909     let where_clause = &ast_generics.where_clause;
1910     for predicate in &where_clause.predicates {
1911         match predicate {
1912             &hir::WherePredicate::BoundPredicate(ref bound_pred) => {
1913                 let ty = ast_ty_to_ty(&ccx.icx(&(base_predicates, ast_generics)),
1914                                       &ExplicitRscope,
1915                                       &*bound_pred.bounded_ty);
1916
1917                 for bound in bound_pred.bounds.iter() {
1918                     match bound {
1919                         &hir::TyParamBound::TraitTyParamBound(ref poly_trait_ref, _) => {
1920                             let mut projections = Vec::new();
1921
1922                             let trait_ref =
1923                                 conv_poly_trait_ref(&ccx.icx(&(base_predicates, ast_generics)),
1924                                                     ty,
1925                                                     poly_trait_ref,
1926                                                     &mut projections);
1927
1928                             result.predicates.push(space, trait_ref.to_predicate());
1929
1930                             for projection in &projections {
1931                                 result.predicates.push(space, projection.to_predicate());
1932                             }
1933                         }
1934
1935                         &hir::TyParamBound::RegionTyParamBound(ref lifetime) => {
1936                             let region = ast_region_to_region(tcx, lifetime);
1937                             let pred = ty::Binder(ty::OutlivesPredicate(ty, region));
1938                             result.predicates.push(space, ty::Predicate::TypeOutlives(pred))
1939                         }
1940                     }
1941                 }
1942             }
1943
1944             &hir::WherePredicate::RegionPredicate(ref region_pred) => {
1945                 let r1 = ast_region_to_region(tcx, &region_pred.lifetime);
1946                 for bound in &region_pred.bounds {
1947                     let r2 = ast_region_to_region(tcx, bound);
1948                     let pred = ty::Binder(ty::OutlivesPredicate(r1, r2));
1949                     result.predicates.push(space, ty::Predicate::RegionOutlives(pred))
1950                 }
1951             }
1952
1953             &hir::WherePredicate::EqPredicate(ref eq_pred) => {
1954                 // FIXME(#20041)
1955                 tcx.sess.span_bug(eq_pred.span,
1956                                     "Equality constraints are not yet \
1957                                         implemented (#20041)")
1958             }
1959         }
1960     }
1961
1962     return result;
1963 }
1964
1965 fn ty_generics<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>,
1966                         space: ParamSpace,
1967                         ast_generics: &hir::Generics,
1968                         base_generics: &ty::Generics<'tcx>)
1969                         -> ty::Generics<'tcx>
1970 {
1971     let tcx = ccx.tcx;
1972     let mut result = base_generics.clone();
1973
1974     let early_lifetimes = early_bound_lifetimes_from_generics(space, ast_generics);
1975     for (i, l) in early_lifetimes.iter().enumerate() {
1976         let bounds = l.bounds.iter()
1977                              .map(|l| ast_region_to_region(tcx, l))
1978                              .collect();
1979         let def = ty::RegionParameterDef { name: l.lifetime.name,
1980                                            space: space,
1981                                            index: i as u32,
1982                                            def_id: ccx.tcx.map.local_def_id(l.lifetime.id),
1983                                            bounds: bounds };
1984         result.regions.push(space, def);
1985     }
1986
1987     assert!(result.types.is_empty_in(space));
1988
1989     // Now create the real type parameters.
1990     for i in 0..ast_generics.ty_params.len() {
1991         let def = get_or_create_type_parameter_def(ccx, ast_generics, space, i as u32);
1992         debug!("ty_generics: def for type param: {:?}, {:?}", def, space);
1993         result.types.push(space, def);
1994     }
1995
1996     result
1997 }
1998
1999 fn convert_default_type_parameter<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
2000                                             path: &P<hir::Ty>,
2001                                             space: ParamSpace,
2002                                             index: u32)
2003                                             -> Ty<'tcx>
2004 {
2005     let ty = ast_ty_to_ty(&ccx.icx(&()), &ExplicitRscope, &path);
2006
2007     for leaf_ty in ty.walk() {
2008         if let ty::TyParam(p) = leaf_ty.sty {
2009             if p.space == space && p.idx >= index {
2010                 span_err!(ccx.tcx.sess, path.span, E0128,
2011                           "type parameters with a default cannot use \
2012                            forward declared identifiers");
2013
2014                 return ccx.tcx.types.err
2015             }
2016         }
2017     }
2018
2019     ty
2020 }
2021
2022 fn get_or_create_type_parameter_def<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>,
2023                                              ast_generics: &hir::Generics,
2024                                              space: ParamSpace,
2025                                              index: u32)
2026                                              -> ty::TypeParameterDef<'tcx>
2027 {
2028     let param = &ast_generics.ty_params[index as usize];
2029
2030     let tcx = ccx.tcx;
2031     match tcx.ty_param_defs.borrow().get(&param.id) {
2032         Some(d) => { return d.clone(); }
2033         None => { }
2034     }
2035
2036     let default = param.default.as_ref().map(
2037         |def| convert_default_type_parameter(ccx, def, space, index)
2038     );
2039
2040     let object_lifetime_default =
2041         compute_object_lifetime_default(ccx, param.id,
2042                                         &param.bounds, &ast_generics.where_clause);
2043
2044     let parent = tcx.map.get_parent(param.id);
2045
2046     let def = ty::TypeParameterDef {
2047         space: space,
2048         index: index,
2049         name: param.name,
2050         def_id: ccx.tcx.map.local_def_id(param.id),
2051         default_def_id: ccx.tcx.map.local_def_id(parent),
2052         default: default,
2053         object_lifetime_default: object_lifetime_default,
2054     };
2055
2056     tcx.ty_param_defs.borrow_mut().insert(param.id, def.clone());
2057
2058     def
2059 }
2060
2061 /// Scan the bounds and where-clauses on a parameter to extract bounds
2062 /// of the form `T:'a` so as to determine the `ObjectLifetimeDefault`.
2063 /// This runs as part of computing the minimal type scheme, so we
2064 /// intentionally avoid just asking astconv to convert all the where
2065 /// clauses into a `ty::Predicate`. This is because that could induce
2066 /// artificial cycles.
2067 fn compute_object_lifetime_default<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>,
2068                                             param_id: ast::NodeId,
2069                                             param_bounds: &[hir::TyParamBound],
2070                                             where_clause: &hir::WhereClause)
2071                                             -> ty::ObjectLifetimeDefault
2072 {
2073     let inline_bounds = from_bounds(ccx, param_bounds);
2074     let where_bounds = from_predicates(ccx, param_id, &where_clause.predicates);
2075     let all_bounds: HashSet<_> = inline_bounds.into_iter()
2076                                               .chain(where_bounds)
2077                                               .collect();
2078     return if all_bounds.len() > 1 {
2079         ty::ObjectLifetimeDefault::Ambiguous
2080     } else if all_bounds.len() == 0 {
2081         ty::ObjectLifetimeDefault::BaseDefault
2082     } else {
2083         ty::ObjectLifetimeDefault::Specific(
2084             all_bounds.into_iter().next().unwrap())
2085     };
2086
2087     fn from_bounds<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>,
2088                             bounds: &[hir::TyParamBound])
2089                             -> Vec<ty::Region>
2090     {
2091         bounds.iter()
2092               .filter_map(|bound| {
2093                   match *bound {
2094                       hir::TraitTyParamBound(..) =>
2095                           None,
2096                       hir::RegionTyParamBound(ref lifetime) =>
2097                           Some(astconv::ast_region_to_region(ccx.tcx, lifetime)),
2098                   }
2099               })
2100               .collect()
2101     }
2102
2103     fn from_predicates<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>,
2104                                 param_id: ast::NodeId,
2105                                 predicates: &[hir::WherePredicate])
2106                                 -> Vec<ty::Region>
2107     {
2108         predicates.iter()
2109                   .flat_map(|predicate| {
2110                       match *predicate {
2111                           hir::WherePredicate::BoundPredicate(ref data) => {
2112                               if data.bound_lifetimes.is_empty() &&
2113                                   is_param(ccx.tcx, &data.bounded_ty, param_id)
2114                               {
2115                                   from_bounds(ccx, &data.bounds).into_iter()
2116                               } else {
2117                                   Vec::new().into_iter()
2118                               }
2119                           }
2120                           hir::WherePredicate::RegionPredicate(..) |
2121                           hir::WherePredicate::EqPredicate(..) => {
2122                               Vec::new().into_iter()
2123                           }
2124                       }
2125                   })
2126                   .collect()
2127     }
2128 }
2129
2130 enum SizedByDefault { Yes, No, }
2131
2132 /// Translate the AST's notion of ty param bounds (which are an enum consisting of a newtyped Ty or
2133 /// a region) to ty's notion of ty param bounds, which can either be user-defined traits, or the
2134 /// built-in trait (formerly known as kind): Send.
2135 fn compute_bounds<'tcx>(astconv: &AstConv<'tcx>,
2136                         param_ty: ty::Ty<'tcx>,
2137                         ast_bounds: &[hir::TyParamBound],
2138                         sized_by_default: SizedByDefault,
2139                         span: Span)
2140                         -> astconv::Bounds<'tcx>
2141 {
2142     let mut bounds =
2143         conv_param_bounds(astconv,
2144                           span,
2145                           param_ty,
2146                           ast_bounds);
2147
2148     if let SizedByDefault::Yes = sized_by_default {
2149         add_unsized_bound(astconv,
2150                           &mut bounds.builtin_bounds,
2151                           ast_bounds,
2152                           span);
2153     }
2154
2155     bounds.trait_bounds.sort_by(|a,b| a.def_id().cmp(&b.def_id()));
2156
2157     bounds
2158 }
2159
2160 /// Converts a specific TyParamBound from the AST into a set of
2161 /// predicates that apply to the self-type. A vector is returned
2162 /// because this can be anywhere from 0 predicates (`T:?Sized` adds no
2163 /// predicates) to 1 (`T:Foo`) to many (`T:Bar<X=i32>` adds `T:Bar`
2164 /// and `<T as Bar>::X == i32`).
2165 fn predicates_from_bound<'tcx>(astconv: &AstConv<'tcx>,
2166                                param_ty: Ty<'tcx>,
2167                                bound: &hir::TyParamBound)
2168                                -> Vec<ty::Predicate<'tcx>>
2169 {
2170     match *bound {
2171         hir::TraitTyParamBound(ref tr, hir::TraitBoundModifier::None) => {
2172             let mut projections = Vec::new();
2173             let pred = conv_poly_trait_ref(astconv, param_ty, tr, &mut projections);
2174             projections.into_iter()
2175                        .map(|p| p.to_predicate())
2176                        .chain(Some(pred.to_predicate()))
2177                        .collect()
2178         }
2179         hir::RegionTyParamBound(ref lifetime) => {
2180             let region = ast_region_to_region(astconv.tcx(), lifetime);
2181             let pred = ty::Binder(ty::OutlivesPredicate(param_ty, region));
2182             vec![ty::Predicate::TypeOutlives(pred)]
2183         }
2184         hir::TraitTyParamBound(_, hir::TraitBoundModifier::Maybe) => {
2185             Vec::new()
2186         }
2187     }
2188 }
2189
2190 fn conv_poly_trait_ref<'tcx>(astconv: &AstConv<'tcx>,
2191                              param_ty: Ty<'tcx>,
2192                              trait_ref: &hir::PolyTraitRef,
2193                              projections: &mut Vec<ty::PolyProjectionPredicate<'tcx>>)
2194                              -> ty::PolyTraitRef<'tcx>
2195 {
2196     astconv::instantiate_poly_trait_ref(astconv,
2197                                         &ExplicitRscope,
2198                                         trait_ref,
2199                                         Some(param_ty),
2200                                         projections)
2201 }
2202
2203 fn conv_param_bounds<'a,'tcx>(astconv: &AstConv<'tcx>,
2204                               span: Span,
2205                               param_ty: ty::Ty<'tcx>,
2206                               ast_bounds: &[hir::TyParamBound])
2207                               -> astconv::Bounds<'tcx>
2208 {
2209     let tcx = astconv.tcx();
2210     let astconv::PartitionedBounds {
2211         builtin_bounds,
2212         trait_bounds,
2213         region_bounds
2214     } = astconv::partition_bounds(tcx, span, &ast_bounds);
2215
2216     let mut projection_bounds = Vec::new();
2217
2218     let trait_bounds: Vec<ty::PolyTraitRef> =
2219         trait_bounds.iter()
2220                     .map(|bound| conv_poly_trait_ref(astconv,
2221                                                      param_ty,
2222                                                      *bound,
2223                                                      &mut projection_bounds))
2224                     .collect();
2225
2226     let region_bounds: Vec<ty::Region> =
2227         region_bounds.into_iter()
2228                      .map(|r| ast_region_to_region(tcx, r))
2229                      .collect();
2230
2231     astconv::Bounds {
2232         region_bounds: region_bounds,
2233         builtin_bounds: builtin_bounds,
2234         trait_bounds: trait_bounds,
2235         projection_bounds: projection_bounds,
2236     }
2237 }
2238
2239 fn compute_type_scheme_of_foreign_fn_decl<'a, 'tcx>(
2240     ccx: &CrateCtxt<'a, 'tcx>,
2241     decl: &hir::FnDecl,
2242     ast_generics: &hir::Generics,
2243     abi: abi::Abi)
2244     -> ty::TypeScheme<'tcx>
2245 {
2246     for i in &decl.inputs {
2247         match (*i).pat.node {
2248             hir::PatIdent(_, _, _) => (),
2249             hir::PatWild(hir::PatWildSingle) => (),
2250             _ => {
2251                 span_err!(ccx.tcx.sess, (*i).pat.span, E0130,
2252                           "patterns aren't allowed in foreign function declarations");
2253             }
2254         }
2255     }
2256
2257     let ty_generics = ty_generics_for_fn(ccx, ast_generics, &ty::Generics::empty());
2258
2259     let rb = BindingRscope::new();
2260     let input_tys = decl.inputs
2261                         .iter()
2262                         .map(|a| ty_of_arg(&ccx.icx(ast_generics), &rb, a, None))
2263                         .collect();
2264
2265     let output = match decl.output {
2266         hir::Return(ref ty) =>
2267             ty::FnConverging(ast_ty_to_ty(&ccx.icx(ast_generics), &rb, &**ty)),
2268         hir::DefaultReturn(..) =>
2269             ty::FnConverging(ccx.tcx.mk_nil()),
2270         hir::NoReturn(..) =>
2271             ty::FnDiverging
2272     };
2273
2274     let t_fn = ccx.tcx.mk_fn(None,
2275         ccx.tcx.mk_bare_fn(ty::BareFnTy {
2276             abi: abi,
2277             unsafety: hir::Unsafety::Unsafe,
2278             sig: ty::Binder(ty::FnSig {inputs: input_tys,
2279                                        output: output,
2280                                        variadic: decl.variadic}),
2281         }));
2282
2283     ty::TypeScheme {
2284         generics: ty_generics,
2285         ty: t_fn
2286     }
2287 }
2288
2289 fn mk_item_substs<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
2290                             ty_generics: &ty::Generics<'tcx>)
2291                             -> Substs<'tcx>
2292 {
2293     let types =
2294         ty_generics.types.map(
2295             |def| ccx.tcx.mk_param_from_def(def));
2296
2297     let regions =
2298         ty_generics.regions.map(
2299             |def| def.to_early_bound_region());
2300
2301     Substs::new(types, regions)
2302 }
2303
2304 /// Verifies that the explicit self type of a method matches the impl
2305 /// or trait. This is a bit weird but basically because right now we
2306 /// don't handle the general case, but instead map it to one of
2307 /// several pre-defined options using various heuristics, this method
2308 /// comes back to check after the fact that explicit type the user
2309 /// wrote actually matches what the pre-defined option said.
2310 fn check_method_self_type<'a, 'tcx, RS:RegionScope>(
2311     ccx: &CrateCtxt<'a, 'tcx>,
2312     rs: &RS,
2313     method_type: Rc<ty::Method<'tcx>>,
2314     required_type: Ty<'tcx>,
2315     explicit_self: &hir::ExplicitSelf,
2316     body_id: ast::NodeId)
2317 {
2318     let tcx = ccx.tcx;
2319     if let hir::SelfExplicit(ref ast_type, _) = explicit_self.node {
2320         let typ = ccx.icx(&method_type.predicates).to_ty(rs, &**ast_type);
2321         let base_type = match typ.sty {
2322             ty::TyRef(_, tm) => tm.ty,
2323             ty::TyBox(typ) => typ,
2324             _ => typ,
2325         };
2326
2327         let body_scope = tcx.region_maps.item_extent(body_id);
2328
2329         // "Required type" comes from the trait definition. It may
2330         // contain late-bound regions from the method, but not the
2331         // trait (since traits only have early-bound region
2332         // parameters).
2333         assert!(!base_type.has_regions_escaping_depth(1));
2334         let required_type_free =
2335             liberate_early_bound_regions(
2336                 tcx, body_scope,
2337                 &tcx.liberate_late_bound_regions(body_scope, &ty::Binder(required_type)));
2338
2339         // The "base type" comes from the impl. It too may have late-bound
2340         // regions from the method.
2341         assert!(!base_type.has_regions_escaping_depth(1));
2342         let base_type_free =
2343             liberate_early_bound_regions(
2344                 tcx, body_scope,
2345                 &tcx.liberate_late_bound_regions(body_scope, &ty::Binder(base_type)));
2346
2347         debug!("required_type={:?} required_type_free={:?} \
2348                 base_type={:?} base_type_free={:?}",
2349                required_type,
2350                required_type_free,
2351                base_type,
2352                base_type_free);
2353
2354         let infcx = infer::new_infer_ctxt(tcx, &tcx.tables, None, false);
2355         drop(::require_same_types(tcx,
2356                                   Some(&infcx),
2357                                   false,
2358                                   explicit_self.span,
2359                                   base_type_free,
2360                                   required_type_free,
2361                                   || {
2362                 format!("mismatched self type: expected `{}`",
2363                          required_type)
2364         }));
2365
2366         // We could conceviably add more free-region relations here,
2367         // but since this code is just concerned with checking that
2368         // the `&Self` types etc match up, it's not really necessary.
2369         // It would just allow people to be more approximate in some
2370         // cases. In any case, we can do it later as we feel the need;
2371         // I'd like this function to go away eventually.
2372         let free_regions = FreeRegionMap::new();
2373
2374         infcx.resolve_regions_and_report_errors(&free_regions, body_id);
2375     }
2376
2377     fn liberate_early_bound_regions<'tcx,T>(
2378         tcx: &ty::ctxt<'tcx>,
2379         scope: region::CodeExtent,
2380         value: &T)
2381         -> T
2382         where T : TypeFoldable<'tcx>
2383     {
2384         /*!
2385          * Convert early-bound regions into free regions; normally this is done by
2386          * applying the `free_substs` from the `ParameterEnvironment`, but this particular
2387          * method-self-type check is kind of hacky and done very early in the process,
2388          * before we really have a `ParameterEnvironment` to check.
2389          */
2390
2391         tcx.fold_regions(value, &mut false, |region, _| {
2392             match region {
2393                 ty::ReEarlyBound(data) => {
2394                     ty::ReFree(ty::FreeRegion {
2395                         scope: scope,
2396                         bound_region: ty::BrNamed(data.def_id, data.name)
2397                     })
2398                 }
2399                 _ => region
2400             }
2401         })
2402     }
2403 }
2404
2405 /// Checks that all the type parameters on an impl
2406 fn enforce_impl_params_are_constrained<'tcx>(tcx: &ty::ctxt<'tcx>,
2407                                              ast_generics: &hir::Generics,
2408                                              impl_def_id: DefId,
2409                                              impl_items: &[P<hir::ImplItem>])
2410 {
2411     let impl_scheme = tcx.lookup_item_type(impl_def_id);
2412     let impl_predicates = tcx.lookup_predicates(impl_def_id);
2413     let impl_trait_ref = tcx.impl_trait_ref(impl_def_id);
2414
2415     // The trait reference is an input, so find all type parameters
2416     // reachable from there, to start (if this is an inherent impl,
2417     // then just examine the self type).
2418     let mut input_parameters: HashSet<_> =
2419         ctp::parameters_for_type(impl_scheme.ty).into_iter().collect();
2420     if let Some(ref trait_ref) = impl_trait_ref {
2421         input_parameters.extend(ctp::parameters_for_trait_ref(trait_ref));
2422     }
2423
2424     ctp::identify_constrained_type_params(tcx,
2425                                           impl_predicates.predicates.as_slice(),
2426                                           impl_trait_ref,
2427                                           &mut input_parameters);
2428
2429     for (index, ty_param) in ast_generics.ty_params.iter().enumerate() {
2430         let param_ty = ty::ParamTy { space: TypeSpace,
2431                                      idx: index as u32,
2432                                      name: ty_param.name };
2433         if !input_parameters.contains(&ctp::Parameter::Type(param_ty)) {
2434             report_unused_parameter(tcx, ty_param.span, "type", &param_ty.to_string());
2435         }
2436     }
2437
2438     // Every lifetime used in an associated type must be constrained.
2439
2440     let lifetimes_in_associated_types: HashSet<_> =
2441         impl_items.iter()
2442                   .map(|item| tcx.impl_or_trait_item(tcx.map.local_def_id(item.id)))
2443                   .filter_map(|item| match item {
2444                       ty::TypeTraitItem(ref assoc_ty) => assoc_ty.ty,
2445                       ty::ConstTraitItem(..) | ty::MethodTraitItem(..) => None
2446                   })
2447                   .flat_map(|ty| ctp::parameters_for_type(ty))
2448                   .filter_map(|p| match p {
2449                       ctp::Parameter::Type(_) => None,
2450                       ctp::Parameter::Region(r) => Some(r),
2451                   })
2452                   .collect();
2453
2454     for (index, lifetime_def) in ast_generics.lifetimes.iter().enumerate() {
2455         let def_id = tcx.map.local_def_id(lifetime_def.lifetime.id);
2456         let region = ty::EarlyBoundRegion { def_id: def_id,
2457                                             space: TypeSpace,
2458                                             index: index as u32,
2459                                             name: lifetime_def.lifetime.name };
2460         if
2461             lifetimes_in_associated_types.contains(&region) && // (*)
2462             !input_parameters.contains(&ctp::Parameter::Region(region))
2463         {
2464             report_unused_parameter(tcx, lifetime_def.lifetime.span,
2465                                     "lifetime", &region.name.to_string());
2466         }
2467     }
2468
2469     // (*) This is a horrible concession to reality. I think it'd be
2470     // better to just ban unconstrianed lifetimes outright, but in
2471     // practice people do non-hygenic macros like:
2472     //
2473     // ```
2474     // macro_rules! __impl_slice_eq1 {
2475     //     ($Lhs: ty, $Rhs: ty, $Bound: ident) => {
2476     //         impl<'a, 'b, A: $Bound, B> PartialEq<$Rhs> for $Lhs where A: PartialEq<B> {
2477     //            ....
2478     //         }
2479     //     }
2480     // }
2481     // ```
2482     //
2483     // In a concession to backwards compatbility, we continue to
2484     // permit those, so long as the lifetimes aren't used in
2485     // associated types. I believe this is sound, because lifetimes
2486     // used elsewhere are not projected back out.
2487 }
2488
2489 fn report_unused_parameter(tcx: &ty::ctxt,
2490                            span: Span,
2491                            kind: &str,
2492                            name: &str)
2493 {
2494     span_err!(tcx.sess, span, E0207,
2495               "the {} parameter `{}` is not constrained by the \
2496                impl trait, self type, or predicates",
2497               kind, name);
2498 }