src/librustc_typeck/coherence/mod.rs

   1 // Copyright 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 // Coherence phase
  12 //
  13 // The job of the coherence phase of typechecking is to ensure that
  14 // each trait has at most one implementation for each type. This is
  15 // done by the orphan and overlap modules. Then we build up various
  16 // mappings. That mapping code resides here.
  17
  18
  19 use middle::lang_items::UnsizeTraitLangItem;
  20 use middle::subst::{self, Subst};
  21 use middle::traits;
  22 use middle::ty::RegionEscape;
  23 use middle::ty::{ImplContainer, ImplOrTraitItemId, ConstTraitItemId};
  24 use middle::ty::{MethodTraitItemId, TypeTraitItemId, ParameterEnvironment};
  25 use middle::ty::{Ty, TyBool, TyChar, TyEnum, TyError};
  26 use middle::ty::{TyParam, TypeScheme, TyRawPtr};
  27 use middle::ty::{TyRef, TyStruct, TyTrait, TyTuple};
  28 use middle::ty::{TyStr, TyArray, TySlice, TyFloat, TyInfer, TyInt};
  29 use middle::ty::{TyUint, TyClosure, TyBox, TyBareFn};
  30 use middle::ty::TyProjection;
  31 use middle::ty;
  32 use middle::free_region::FreeRegionMap;
  33 use CrateCtxt;
  34 use middle::infer::{self, InferCtxt, new_infer_ctxt};
  35 use rustc::ast_map::{self, NodeItem};
  36 use std::cell::RefCell;
  37 use std::rc::Rc;
  38 use syntax::ast::{Crate, DefId};
  39 use syntax::ast::{Item, ItemImpl};
  40 use syntax::ast::{LOCAL_CRATE};
  41 use syntax::ast;
  42 use syntax::ast_util::local_def;
  43 use syntax::codemap::Span;
  44 use syntax::parse::token;
  45 use syntax::visit;
  46 use util::nodemap::{DefIdMap, FnvHashMap};
  47
  48 mod orphan;
  49 mod overlap;
  50 mod unsafety;
  51
  52 // Returns the def ID of the base type, if there is one.
  53 fn get_base_type_def_id<'a, 'tcx>(inference_context: &InferCtxt<'a, 'tcx>,
  54                                   span: Span,
  55                                   ty: Ty<'tcx>)
  56                                   -> Option<DefId> {
  57     match ty.sty {
  58         TyEnum(def_id, _) |
  59         TyStruct(def_id, _) => {
  60             Some(def_id)
  61         }
  62
  63         TyTrait(ref t) => {
  64             Some(t.principal_def_id())
  65         }
  66
  67         TyBox(_) => {
  68             inference_context.tcx.lang_items.owned_box()
  69         }
  70
  71         TyBool | TyChar | TyInt(..) | TyUint(..) | TyFloat(..) |
  72         TyStr(..) | TyArray(..) | TySlice(..) | TyBareFn(..) | TyTuple(..) |
  73         TyParam(..) | TyError |
  74         TyRawPtr(_) | TyRef(_, _) | TyProjection(..) => {
  75             None
  76         }
  77
  78         TyInfer(..) | TyClosure(..) => {
  79             // `ty` comes from a user declaration so we should only expect types
  80             // that the user can type
  81             inference_context.tcx.sess.span_bug(
  82                 span,
  83                 &format!("coherence encountered unexpected type searching for base type: {}",
  84                          ty));
  85         }
  86     }
  87 }
  88
  89 struct CoherenceChecker<'a, 'tcx: 'a> {
  90     crate_context: &'a CrateCtxt<'a, 'tcx>,
  91     inference_context: InferCtxt<'a, 'tcx>,
  92     inherent_impls: RefCell<DefIdMap<Rc<RefCell<Vec<ast::DefId>>>>>,
  93 }
  94
  95 struct CoherenceCheckVisitor<'a, 'tcx: 'a> {
  96     cc: &'a CoherenceChecker<'a, 'tcx>
  97 }
  98
  99 impl<'a, 'tcx, 'v> visit::Visitor<'v> for CoherenceCheckVisitor<'a, 'tcx> {
 100     fn visit_item(&mut self, item: &Item) {
 101         if let ItemImpl(..) = item.node {
 102             self.cc.check_implementation(item)
 103         }
 104
 105         visit::walk_item(self, item);
 106     }
 107 }
 108
 109 impl<'a, 'tcx> CoherenceChecker<'a, 'tcx> {
 110     fn check(&self, krate: &Crate) {
 111         // Check implementations and traits. This populates the tables
 112         // containing the inherent methods and extension methods. It also
 113         // builds up the trait inheritance table.
 114         let mut visitor = CoherenceCheckVisitor { cc: self };
 115         visit::walk_crate(&mut visitor, krate);
 116
 117         // Copy over the inherent impls we gathered up during the walk into
 118         // the tcx.
 119         let mut tcx_inherent_impls =
 120             self.crate_context.tcx.inherent_impls.borrow_mut();
 121         for (k, v) in self.inherent_impls.borrow().iter() {
 122             tcx_inherent_impls.insert((*k).clone(),
 123                                       Rc::new((*v.borrow()).clone()));
 124         }
 125
 126         // Populate the table of destructors. It might seem a bit strange to
 127         // do this here, but it's actually the most convenient place, since
 128         // the coherence tables contain the trait -> type mappings.
 129         self.populate_destructor_table();
 130
 131         // Check to make sure implementations of `Copy` are legal.
 132         self.check_implementations_of_copy();
 133
 134         // Check to make sure implementations of `CoerceUnsized` are legal
 135         // and collect the necessary information from them.
 136         self.check_implementations_of_coerce_unsized();
 137     }
 138
 139     fn check_implementation(&self, item: &Item) {
 140         let tcx = self.crate_context.tcx;
 141         let impl_did = local_def(item.id);
 142         let self_type = tcx.lookup_item_type(impl_did);
 143
 144         // If there are no traits, then this implementation must have a
 145         // base type.
 146
 147         let impl_items = self.create_impl_from_item(item);
 148
 149         if let Some(trait_ref) = self.crate_context.tcx.impl_trait_ref(impl_did) {
 150             debug!("(checking implementation) adding impl for trait '{:?}', item '{}'",
 151                    trait_ref,
 152                    item.ident);
 153
 154             enforce_trait_manually_implementable(self.crate_context.tcx,
 155                                                  item.span,
 156                                                  trait_ref.def_id);
 157             self.add_trait_impl(trait_ref, impl_did);
 158         } else {
 159             // Add the implementation to the mapping from implementation to base
 160             // type def ID, if there is a base type for this implementation and
 161             // the implementation does not have any associated traits.
 162             if let Some(base_type_def_id) = get_base_type_def_id(
 163                     &self.inference_context, item.span, self_type.ty) {
 164                 self.add_inherent_impl(base_type_def_id, impl_did);
 165             }
 166         }
 167
 168         tcx.impl_items.borrow_mut().insert(impl_did, impl_items);
 169     }
 170
 171     // Creates default method IDs and performs type substitutions for an impl
 172     // and trait pair. Then, for each provided method in the trait, inserts a
 173     // `ProvidedMethodInfo` instance into the `provided_method_sources` map.
 174     fn instantiate_default_methods(
 175             &self,
 176             impl_id: DefId,
 177             trait_ref: &ty::TraitRef<'tcx>,
 178             all_impl_items: &mut Vec<ImplOrTraitItemId>) {
 179         let tcx = self.crate_context.tcx;
 180         debug!("instantiate_default_methods(impl_id={:?}, trait_ref={:?})",
 181                impl_id, trait_ref);
 182
 183         let impl_type_scheme = tcx.lookup_item_type(impl_id);
 184
 185         let prov = tcx.provided_trait_methods(trait_ref.def_id);
 186         for trait_method in &prov {
 187             // Synthesize an ID.
 188             let new_id = tcx.sess.next_node_id();
 189             let new_did = local_def(new_id);
 190
 191             debug!("new_did={:?} trait_method={:?}", new_did, trait_method);
 192
 193             // Create substitutions for the various trait parameters.
 194             let new_method_ty =
 195                 Rc::new(subst_receiver_types_in_method_ty(
 196                     tcx,
 197                     impl_id,
 198                     &impl_type_scheme,
 199                     trait_ref,
 200                     new_did,
 201                     &**trait_method,
 202                     Some(trait_method.def_id)));
 203
 204             debug!("new_method_ty={:?}", new_method_ty);
 205             all_impl_items.push(MethodTraitItemId(new_did));
 206
 207             // construct the polytype for the method based on the
 208             // method_ty.  it will have all the generics from the
 209             // impl, plus its own.
 210             let new_polytype = ty::TypeScheme {
 211                 generics: new_method_ty.generics.clone(),
 212                 ty: tcx.mk_fn(Some(new_did),
 213                               tcx.mk_bare_fn(new_method_ty.fty.clone()))
 214             };
 215             debug!("new_polytype={:?}", new_polytype);
 216
 217             tcx.register_item_type(new_did, new_polytype);
 218             tcx.predicates.borrow_mut().insert(new_did, new_method_ty.predicates.clone());
 219             tcx.impl_or_trait_items
 220                .borrow_mut()
 221                .insert(new_did, ty::MethodTraitItem(new_method_ty));
 222
 223             // Pair the new synthesized ID up with the
 224             // ID of the method.
 225             self.crate_context.tcx.provided_method_sources.borrow_mut()
 226                 .insert(new_did, trait_method.def_id);
 227         }
 228     }
 229
 230     fn add_inherent_impl(&self, base_def_id: DefId, impl_def_id: DefId) {
 231         match self.inherent_impls.borrow().get(&base_def_id) {
 232             Some(implementation_list) => {
 233                 implementation_list.borrow_mut().push(impl_def_id);
 234                 return;
 235             }
 236             None => {}
 237         }
 238
 239         self.inherent_impls.borrow_mut().insert(
 240             base_def_id,
 241             Rc::new(RefCell::new(vec!(impl_def_id))));
 242     }
 243
 244     fn add_trait_impl(&self, impl_trait_ref: ty::TraitRef<'tcx>, impl_def_id: DefId) {
 245         debug!("add_trait_impl: impl_trait_ref={:?} impl_def_id={:?}",
 246                impl_trait_ref, impl_def_id);
 247         let trait_def = self.crate_context.tcx.lookup_trait_def(impl_trait_ref.def_id);
 248         trait_def.record_impl(self.crate_context.tcx, impl_def_id, impl_trait_ref);
 249     }
 250
 251     // Converts an implementation in the AST to a vector of items.
 252     fn create_impl_from_item(&self, item: &Item) -> Vec<ImplOrTraitItemId> {
 253         match item.node {
 254             ItemImpl(_, _, _, _, _, ref impl_items) => {
 255                 let mut items: Vec<ImplOrTraitItemId> =
 256                         impl_items.iter().map(|impl_item| {
 257                     match impl_item.node {
 258                         ast::ConstImplItem(..) => {
 259                             ConstTraitItemId(local_def(impl_item.id))
 260                         }
 261                         ast::MethodImplItem(..) => {
 262                             MethodTraitItemId(local_def(impl_item.id))
 263                         }
 264                         ast::TypeImplItem(_) => {
 265                             TypeTraitItemId(local_def(impl_item.id))
 266                         }
 267                         ast::MacImplItem(_) => {
 268                             self.crate_context.tcx.sess.span_bug(impl_item.span,
 269                                                                  "unexpanded macro");
 270                         }
 271                     }
 272                 }).collect();
 273
 274                 let def_id = local_def(item.id);
 275                 if let Some(trait_ref) = self.crate_context.tcx.impl_trait_ref(def_id) {
 276                     self.instantiate_default_methods(def_id, &trait_ref, &mut items);
 277                 }
 278
 279                 items
 280             }
 281             _ => {
 282                 self.crate_context.tcx.sess.span_bug(item.span,
 283                                                      "can't convert a non-impl \
 284                                                       to an impl");
 285             }
 286         }
 287     }
 288
 289     //
 290     // Destructors
 291     //
 292
 293     fn populate_destructor_table(&self) {
 294         let tcx = self.crate_context.tcx;
 295         let drop_trait = match tcx.lang_items.drop_trait() {
 296             Some(id) => id, None => { return }
 297         };
 298         tcx.populate_implementations_for_trait_if_necessary(drop_trait);
 299         let drop_trait = tcx.lookup_trait_def(drop_trait);
 300
 301         let impl_items = tcx.impl_items.borrow();
 302
 303         drop_trait.for_each_impl(tcx, |impl_did| {
 304             let items = impl_items.get(&impl_did).unwrap();
 305             if items.is_empty() {
 306                 // We'll error out later. For now, just don't ICE.
 307                 return;
 308             }
 309             let method_def_id = items[0];
 310
 311             let self_type = tcx.lookup_item_type(impl_did);
 312             match self_type.ty.sty {
 313                 ty::TyEnum(type_def_id, _) |
 314                 ty::TyStruct(type_def_id, _) |
 315                 ty::TyClosure(type_def_id, _) => {
 316                     tcx.destructor_for_type
 317                        .borrow_mut()
 318                        .insert(type_def_id, method_def_id.def_id());
 319                     tcx.destructors
 320                        .borrow_mut()
 321                        .insert(method_def_id.def_id());
 322                 }
 323                 _ => {
 324                     // Destructors only work on nominal types.
 325                     if impl_did.krate == ast::LOCAL_CRATE {
 326                         {
 327                             match tcx.map.find(impl_did.node) {
 328                                 Some(ast_map::NodeItem(item)) => {
 329                                     span_err!(tcx.sess, item.span, E0120,
 330                                         "the Drop trait may only be implemented on structures");
 331                                 }
 332                                 _ => {
 333                                     tcx.sess.bug("didn't find impl in ast \
 334                                                   map");
 335                                 }
 336                             }
 337                         }
 338                     } else {
 339                         tcx.sess.bug("found external impl of Drop trait on \
 340                                       something other than a struct");
 341                     }
 342                 }
 343             }
 344         });
 345     }
 346
 347     /// Ensures that implementations of the built-in trait `Copy` are legal.
 348     fn check_implementations_of_copy(&self) {
 349         let tcx = self.crate_context.tcx;
 350         let copy_trait = match tcx.lang_items.copy_trait() {
 351             Some(id) => id,
 352             None => return,
 353         };
 354         tcx.populate_implementations_for_trait_if_necessary(copy_trait);
 355         let copy_trait = tcx.lookup_trait_def(copy_trait);
 356
 357         copy_trait.for_each_impl(tcx, |impl_did| {
 358             debug!("check_implementations_of_copy: impl_did={:?}",
 359                    impl_did);
 360
 361             if impl_did.krate != ast::LOCAL_CRATE {
 362                 debug!("check_implementations_of_copy(): impl not in this \
 363                         crate");
 364                 return
 365             }
 366
 367             let self_type = tcx.lookup_item_type(impl_did);
 368             debug!("check_implementations_of_copy: self_type={:?} (bound)",
 369                    self_type);
 370
 371             let span = tcx.map.span(impl_did.node);
 372             let param_env = ParameterEnvironment::for_item(tcx, impl_did.node);
 373             let self_type = self_type.ty.subst(tcx, &param_env.free_substs);
 374             assert!(!self_type.has_escaping_regions());
 375
 376             debug!("check_implementations_of_copy: self_type={:?} (free)",
 377                    self_type);
 378
 379             match param_env.can_type_implement_copy(self_type, span) {
 380                 Ok(()) => {}
 381                 Err(ty::FieldDoesNotImplementCopy(name)) => {
 382                        span_err!(tcx.sess, span, E0204,
 383                                  "the trait `Copy` may not be \
 384                                           implemented for this type; field \
 385                                           `{}` does not implement `Copy`",
 386                                          token::get_name(name))
 387                 }
 388                 Err(ty::VariantDoesNotImplementCopy(name)) => {
 389                        span_err!(tcx.sess, span, E0205,
 390                                  "the trait `Copy` may not be \
 391                                           implemented for this type; variant \
 392                                           `{}` does not implement `Copy`",
 393                                          token::get_name(name))
 394                 }
 395                 Err(ty::TypeIsStructural) => {
 396                        span_err!(tcx.sess, span, E0206,
 397                                  "the trait `Copy` may not be implemented \
 398                                   for this type; type is not a structure or \
 399                                   enumeration")
 400                 }
 401                 Err(ty::TypeHasDestructor) => {
 402                     span_err!(tcx.sess, span, E0184,
 403                               "the trait `Copy` may not be implemented for this type; \
 404                                the type has a destructor");
 405                 }
 406             }
 407         });
 408     }
 409
 410     /// Process implementations of the built-in trait `CoerceUnsized`.
 411     fn check_implementations_of_coerce_unsized(&self) {
 412         let tcx = self.crate_context.tcx;
 413         let coerce_unsized_trait = match tcx.lang_items.coerce_unsized_trait() {
 414             Some(id) => id,
 415             None => return,
 416         };
 417         let unsize_trait = match tcx.lang_items.require(UnsizeTraitLangItem) {
 418             Ok(id) => id,
 419             Err(err) => {
 420                 tcx.sess.fatal(&format!("`CoerceUnsized` implementation {}", err));
 421             }
 422         };
 423
 424         let trait_def = tcx.lookup_trait_def(coerce_unsized_trait);
 425
 426         trait_def.for_each_impl(tcx, |impl_did| {
 427             debug!("check_implementations_of_coerce_unsized: impl_did={:?}",
 428                    impl_did);
 429
 430             if impl_did.krate != ast::LOCAL_CRATE {
 431                 debug!("check_implementations_of_coerce_unsized(): impl not \
 432                         in this crate");
 433                 return;
 434             }
 435
 436             let source = tcx.lookup_item_type(impl_did).ty;
 437             let trait_ref = self.crate_context.tcx.impl_trait_ref(impl_did).unwrap();
 438             let target = *trait_ref.substs.types.get(subst::TypeSpace, 0);
 439             debug!("check_implementations_of_coerce_unsized: {:?} -> {:?} (bound)",
 440                    source, target);
 441
 442             let span = tcx.map.span(impl_did.node);
 443             let param_env = ParameterEnvironment::for_item(tcx, impl_did.node);
 444             let source = source.subst(tcx, &param_env.free_substs);
 445             let target = target.subst(tcx, &param_env.free_substs);
 446             assert!(!source.has_escaping_regions());
 447
 448             debug!("check_implementations_of_coerce_unsized: {:?} -> {:?} (free)",
 449                    source, target);
 450
 451             let infcx = new_infer_ctxt(tcx, &tcx.tables, Some(param_env), true);
 452
 453             let check_mutbl = |mt_a: ty::mt<'tcx>, mt_b: ty::mt<'tcx>,
 454                                mk_ptr: &Fn(Ty<'tcx>) -> Ty<'tcx>| {
 455                 if (mt_a.mutbl, mt_b.mutbl) == (ast::MutImmutable, ast::MutMutable) {
 456                     infcx.report_mismatched_types(span, mk_ptr(mt_b.ty),
 457                                                   target, &ty::terr_mutability);
 458                 }
 459                 (mt_a.ty, mt_b.ty, unsize_trait, None)
 460             };
 461             let (source, target, trait_def_id, kind) = match (&source.sty, &target.sty) {
 462                 (&ty::TyBox(a), &ty::TyBox(b)) => (a, b, unsize_trait, None),
 463
 464                 (&ty::TyRef(r_a, mt_a), &ty::TyRef(r_b, mt_b)) => {
 465                     infer::mk_subr(&infcx, infer::RelateObjectBound(span), *r_b, *r_a);
 466                     check_mutbl(mt_a, mt_b, &|ty| tcx.mk_imm_ref(r_b, ty))
 467                 }
 468
 469                 (&ty::TyRef(_, mt_a), &ty::TyRawPtr(mt_b)) |
 470                 (&ty::TyRawPtr(mt_a), &ty::TyRawPtr(mt_b)) => {
 471                     check_mutbl(mt_a, mt_b, &|ty| tcx.mk_imm_ptr(ty))
 472                 }
 473
 474                 (&ty::TyStruct(def_id_a, substs_a), &ty::TyStruct(def_id_b, substs_b)) => {
 475                     if def_id_a != def_id_b {
 476                         let source_path = tcx.item_path_str(def_id_a);
 477                         let target_path = tcx.item_path_str(def_id_b);
 478                         span_err!(tcx.sess, span, E0377,
 479                                   "the trait `CoerceUnsized` may only be implemented \
 480                                    for a coercion between structures with the same \
 481                                    definition; expected {}, found {}",
 482                                   source_path, target_path);
 483                         return;
 484                     }
 485
 486                     let origin = infer::Misc(span);
 487                     let fields = tcx.lookup_struct_fields(def_id_a);
 488                     let diff_fields = fields.iter().enumerate().filter_map(|(i, f)| {
 489                         let ty = tcx.lookup_field_type_unsubstituted(def_id_a, f.id);
 490                         let (a, b) = (ty.subst(tcx, substs_a), ty.subst(tcx, substs_b));
 491                         if infcx.sub_types(false, origin, b, a).is_ok() {
 492                             None
 493                         } else {
 494                             Some((i, a, b))
 495                         }
 496                     }).collect::<Vec<_>>();
 497
 498                     if diff_fields.is_empty() {
 499                         span_err!(tcx.sess, span, E0374,
 500                                   "the trait `CoerceUnsized` may only be implemented \
 501                                    for a coercion between structures with one field \
 502                                    being coerced, none found");
 503                         return;
 504                     } else if diff_fields.len() > 1 {
 505                         span_err!(tcx.sess, span, E0375,
 506                                   "the trait `CoerceUnsized` may only be implemented \
 507                                    for a coercion between structures with one field \
 508                                    being coerced, but {} fields need coercions: {}",
 509                                    diff_fields.len(), diff_fields.iter().map(|&(i, a, b)| {
 510                                         let name = fields[i].name;
 511                                         format!("{} ({} to {})",
 512                                                 if name == token::special_names::unnamed_field {
 513                                                     i.to_string()
 514                                                 } else {
 515                                                     name.to_string()
 516                                                 }, a, b)
 517                                    }).collect::<Vec<_>>().join(", "));
 518                         return;
 519                     }
 520
 521                     let (i, a, b) = diff_fields[0];
 522                     let kind = ty::CustomCoerceUnsized::Struct(i);
 523                     (a, b, coerce_unsized_trait, Some(kind))
 524                 }
 525
 526                 _ => {
 527                     span_err!(tcx.sess, span, E0376,
 528                               "the trait `CoerceUnsized` may only be implemented \
 529                                for a coercion between structures");
 530                     return;
 531                 }
 532             };
 533
 534             let mut fulfill_cx = infcx.fulfillment_cx.borrow_mut();
 535
 536             // Register an obligation for `A: Trait<B>`.
 537             let cause = traits::ObligationCause::misc(span, impl_did.node);
 538             let predicate = traits::predicate_for_trait_def(tcx, cause, trait_def_id,
 539                                                             0, source, vec![target]);
 540             fulfill_cx.register_predicate_obligation(&infcx, predicate);
 541
 542             // Check that all transitive obligations are satisfied.
 543             if let Err(errors) = fulfill_cx.select_all_or_error(&infcx) {
 544                 traits::report_fulfillment_errors(&infcx, &errors);
 545             }
 546
 547             // Finally, resolve all regions.
 548             let mut free_regions = FreeRegionMap::new();
 549             free_regions.relate_free_regions_from_predicates(tcx, &infcx.parameter_environment
 550                                                                         .caller_bounds);
 551             infcx.resolve_regions_and_report_errors(&free_regions, impl_did.node);
 552
 553             if let Some(kind) = kind {
 554                 tcx.custom_coerce_unsized_kinds.borrow_mut().insert(impl_did, kind);
 555             }
 556         });
 557     }
 558 }
 559
 560 fn enforce_trait_manually_implementable(tcx: &ty::ctxt, sp: Span, trait_def_id: ast::DefId) {
 561     if tcx.sess.features.borrow().unboxed_closures {
 562         // the feature gate allows all of them
 563         return
 564     }
 565     let did = Some(trait_def_id);
 566     let li = &tcx.lang_items;
 567
 568     let trait_name = if did == li.fn_trait() {
 569         "Fn"
 570     } else if did == li.fn_mut_trait() {
 571         "FnMut"
 572     } else if did == li.fn_once_trait() {
 573         "FnOnce"
 574     } else {
 575         return // everything OK
 576     };
 577     span_err!(tcx.sess, sp, E0183, "manual implementations of `{}` are experimental", trait_name);
 578     fileline_help!(tcx.sess, sp,
 579                "add `#![feature(unboxed_closures)]` to the crate attributes to enable");
 580 }
 581
 582 fn subst_receiver_types_in_method_ty<'tcx>(tcx: &ty::ctxt<'tcx>,
 583                                            impl_id: ast::DefId,
 584                                            impl_type_scheme: &ty::TypeScheme<'tcx>,
 585                                            trait_ref: &ty::TraitRef<'tcx>,
 586                                            new_def_id: ast::DefId,
 587                                            method: &ty::Method<'tcx>,
 588                                            provided_source: Option<ast::DefId>)
 589                                            -> ty::Method<'tcx>
 590 {
 591     let combined_substs = tcx.make_substs_for_receiver_types(trait_ref, method);
 592
 593     debug!("subst_receiver_types_in_method_ty: combined_substs={:?}",
 594            combined_substs);
 595
 596     let method_predicates = method.predicates.subst(tcx, &combined_substs);
 597     let mut method_generics = method.generics.subst(tcx, &combined_substs);
 598
 599     // replace the type parameters declared on the trait with those
 600     // from the impl
 601     for &space in &[subst::TypeSpace, subst::SelfSpace] {
 602         method_generics.types.replace(
 603             space,
 604             impl_type_scheme.generics.types.get_slice(space).to_vec());
 605         method_generics.regions.replace(
 606             space,
 607             impl_type_scheme.generics.regions.get_slice(space).to_vec());
 608     }
 609
 610     debug!("subst_receiver_types_in_method_ty: method_generics={:?}",
 611            method_generics);
 612
 613     let method_fty = method.fty.subst(tcx, &combined_substs);
 614
 615     debug!("subst_receiver_types_in_method_ty: method_ty={:?}",
 616            method.fty);
 617
 618     ty::Method::new(
 619         method.name,
 620         method_generics,
 621         method_predicates,
 622         method_fty,
 623         method.explicit_self,
 624         method.vis,
 625         new_def_id,
 626         ImplContainer(impl_id),
 627         provided_source
 628     )
 629 }
 630
 631 pub fn check_coherence(crate_context: &CrateCtxt) {
 632     CoherenceChecker {
 633         crate_context: crate_context,
 634         inference_context: new_infer_ctxt(crate_context.tcx, &crate_context.tcx.tables, None, true),
 635         inherent_impls: RefCell::new(FnvHashMap()),
 636     }.check(crate_context.tcx.map.krate());
 637     unsafety::check(crate_context.tcx);
 638     orphan::check(crate_context.tcx);
 639     overlap::check(crate_context.tcx);
 640 }