src/librustc_traits/chalk_context/program_clauses.rs

   1 use rustc::traits::{
   2     WellFormed,
   3     FromEnv,
   4     DomainGoal,
   5     GoalKind,
   6     Clause,
   7     Clauses,
   8     ProgramClause,
   9     ProgramClauseCategory,
  10     Environment,
  11 };
  12 use rustc::ty;
  13 use rustc::ty::subst::{InternalSubsts, Subst};
  14 use rustc::hir;
  15 use rustc::hir::def_id::DefId;
  16 use rustc_target::spec::abi;
  17 use super::ChalkInferenceContext;
  18 use crate::lowering::Lower;
  19 use crate::generic_types;
  20 use std::iter;
  21
  22 fn assemble_clauses_from_impls<'tcx>(
  23     tcx: ty::TyCtxt<'_, '_, 'tcx>,
  24     trait_def_id: DefId,
  25     clauses: &mut Vec<Clause<'tcx>>
  26 ) {
  27     tcx.for_each_impl(trait_def_id, |impl_def_id| {
  28         clauses.extend(
  29             tcx.program_clauses_for(impl_def_id)
  30                 .into_iter()
  31                 .cloned()
  32         );
  33     });
  34 }
  35
  36 fn assemble_clauses_from_assoc_ty_values<'tcx>(
  37     tcx: ty::TyCtxt<'_, '_, 'tcx>,
  38     trait_def_id: DefId,
  39     clauses: &mut Vec<Clause<'tcx>>
  40 ) {
  41     tcx.for_each_impl(trait_def_id, |impl_def_id| {
  42         for def_id in tcx.associated_item_def_ids(impl_def_id).iter() {
  43             clauses.extend(
  44                 tcx.program_clauses_for(*def_id)
  45                     .into_iter()
  46                     .cloned()
  47             );
  48         }
  49     });
  50 }
  51
  52 fn assemble_builtin_sized_impls<'tcx>(
  53     tcx: ty::TyCtxt<'_, '_, 'tcx>,
  54     sized_def_id: DefId,
  55     ty: ty::Ty<'tcx>,
  56     clauses: &mut Vec<Clause<'tcx>>
  57 ) {
  58     let mut push_builtin_impl = |ty: ty::Ty<'tcx>, nested: &[ty::Ty<'tcx>]| {
  59         let clause = ProgramClause {
  60             goal: ty::TraitPredicate {
  61                 trait_ref: ty::TraitRef {
  62                     def_id: sized_def_id,
  63                     substs: tcx.mk_substs_trait(ty, &[]),
  64                 },
  65             }.lower(),
  66             hypotheses: tcx.mk_goals(
  67                 nested.iter()
  68                     .cloned()
  69                     .map(|nested_ty| ty::TraitRef {
  70                         def_id: sized_def_id,
  71                         substs: tcx.mk_substs_trait(nested_ty, &[]),
  72                     })
  73                     .map(|trait_ref| ty::TraitPredicate { trait_ref })
  74                     .map(|pred| GoalKind::DomainGoal(pred.lower()))
  75                     .map(|goal_kind| tcx.mk_goal(goal_kind))
  76             ),
  77             category: ProgramClauseCategory::Other,
  78         };
  79         // Bind innermost bound vars that may exist in `ty` and `nested`.
  80         clauses.push(Clause::ForAll(ty::Binder::bind(clause)));
  81     };
  82
  83     match &ty.sty {
  84         // Non parametric primitive types.
  85         ty::Bool |
  86         ty::Char |
  87         ty::Int(..) |
  88         ty::Uint(..) |
  89         ty::Float(..) |
  90         ty::Error |
  91         ty::Never => push_builtin_impl(ty, &[]),
  92
  93         // These ones are always `Sized`.
  94         &ty::Array(_, length) => {
  95             push_builtin_impl(tcx.mk_ty(ty::Array(generic_types::bound(tcx, 0), length)), &[]);
  96         }
  97         ty::RawPtr(ptr) => {
  98             push_builtin_impl(generic_types::raw_ptr(tcx, ptr.mutbl), &[]);
  99         }
 100         &ty::Ref(_, _, mutbl) => {
 101             push_builtin_impl(generic_types::ref_ty(tcx, mutbl), &[]);
 102         }
 103         ty::FnPtr(fn_ptr) => {
 104             let fn_ptr = fn_ptr.skip_binder();
 105             let fn_ptr = generic_types::fn_ptr(
 106                 tcx,
 107                 fn_ptr.inputs_and_output.len(),
 108                 fn_ptr.c_variadic,
 109                 fn_ptr.unsafety,
 110                 fn_ptr.abi
 111             );
 112             push_builtin_impl(fn_ptr, &[]);
 113         }
 114         &ty::FnDef(def_id, ..) => {
 115             push_builtin_impl(generic_types::fn_def(tcx, def_id), &[]);
 116         }
 117         &ty::Closure(def_id, ..) => {
 118             push_builtin_impl(generic_types::closure(tcx, def_id), &[]);
 119         }
 120         &ty::Generator(def_id, ..) => {
 121             push_builtin_impl(generic_types::generator(tcx, def_id), &[]);
 122         }
 123
 124         // `Sized` if the last type is `Sized` (because else we will get a WF error anyway).
 125         &ty::Tuple(type_list) => {
 126             let type_list = generic_types::type_list(tcx, type_list.len());
 127             push_builtin_impl(tcx.mk_ty(ty::Tuple(type_list)), &**type_list);
 128         }
 129
 130         // Struct def
 131         ty::Adt(adt_def, _) => {
 132             let substs = InternalSubsts::bound_vars_for_item(tcx, adt_def.did);
 133             let adt = tcx.mk_ty(ty::Adt(adt_def, substs));
 134             let sized_constraint = adt_def.sized_constraint(tcx)
 135                 .iter()
 136                 .map(|ty| ty.subst(tcx, substs))
 137                 .collect::<Vec<_>>();
 138             push_builtin_impl(adt, &sized_constraint);
 139         }
 140
 141         // Artificially trigger an ambiguity.
 142         ty::Infer(..) => {
 143             // Everybody can find at least two types to unify against:
 144             // general ty vars, int vars and float vars.
 145             push_builtin_impl(tcx.types.i32, &[]);
 146             push_builtin_impl(tcx.types.u32, &[]);
 147             push_builtin_impl(tcx.types.f32, &[]);
 148             push_builtin_impl(tcx.types.f64, &[]);
 149         }
 150
 151         ty::Projection(_projection_ty) => {
 152             // FIXME: add builtin impls from the associated type values found in
 153             // trait impls of `projection_ty.trait_ref(tcx)`.
 154         }
 155
 156         // The `Sized` bound can only come from the environment.
 157         ty::Param(..) |
 158         ty::Placeholder(..) |
 159         ty::UnnormalizedProjection(..) => (),
 160
 161         // Definitely not `Sized`.
 162         ty::Foreign(..) |
 163         ty::Str |
 164         ty::Slice(..) |
 165         ty::Dynamic(..) |
 166         ty::Opaque(..) => (),
 167
 168         ty::Bound(..) |
 169         ty::GeneratorWitness(..) => bug!("unexpected type {:?}", ty),
 170     }
 171 }
 172
 173 fn wf_clause_for_raw_ptr<'tcx>(
 174     tcx: ty::TyCtxt<'_, '_, 'tcx>,
 175     mutbl: hir::Mutability
 176 ) -> Clauses<'tcx> {
 177     let ptr_ty = generic_types::raw_ptr(tcx, mutbl);
 178
 179     let wf_clause = ProgramClause {
 180         goal: DomainGoal::WellFormed(WellFormed::Ty(ptr_ty)),
 181         hypotheses: ty::List::empty(),
 182         category: ProgramClauseCategory::WellFormed,
 183     };
 184     let wf_clause = Clause::Implies(wf_clause);
 185
 186     // `forall<T> { WellFormed(*const T). }`
 187     tcx.mk_clauses(iter::once(wf_clause))
 188 }
 189
 190 fn wf_clause_for_fn_ptr<'tcx>(
 191     tcx: ty::TyCtxt<'_, '_, 'tcx>,
 192     arity_and_output: usize,
 193     c_variadic: bool,
 194     unsafety: hir::Unsafety,
 195     abi: abi::Abi
 196 ) -> Clauses<'tcx> {
 197     let fn_ptr = generic_types::fn_ptr(tcx, arity_and_output, c_variadic, unsafety, abi);
 198
 199     let wf_clause = ProgramClause {
 200         goal: DomainGoal::WellFormed(WellFormed::Ty(fn_ptr)),
 201         hypotheses: ty::List::empty(),
 202         category: ProgramClauseCategory::WellFormed,
 203     };
 204     let wf_clause = Clause::ForAll(ty::Binder::bind(wf_clause));
 205
 206     // `forall <T1, ..., Tn+1> { WellFormed(for<> fn(T1, ..., Tn) -> Tn+1). }`
 207     // where `n + 1` == `arity_and_output`
 208     tcx.mk_clauses(iter::once(wf_clause))
 209 }
 210
 211 fn wf_clause_for_slice<'tcx>(tcx: ty::TyCtxt<'_, '_, 'tcx>) -> Clauses<'tcx> {
 212     let ty = generic_types::bound(tcx, 0);
 213     let slice_ty = tcx.mk_slice(ty);
 214
 215     let sized_trait = match tcx.lang_items().sized_trait() {
 216         Some(def_id) => def_id,
 217         None => return ty::List::empty(),
 218     };
 219     let sized_implemented = ty::TraitRef {
 220         def_id: sized_trait,
 221         substs: tcx.mk_substs_trait(ty, ty::List::empty()),
 222     };
 223     let sized_implemented: DomainGoal<'_> = ty::TraitPredicate {
 224         trait_ref: sized_implemented
 225     }.lower();
 226
 227     let wf_clause = ProgramClause {
 228         goal: DomainGoal::WellFormed(WellFormed::Ty(slice_ty)),
 229         hypotheses: tcx.mk_goals(
 230             iter::once(tcx.mk_goal(GoalKind::DomainGoal(sized_implemented)))
 231         ),
 232         category: ProgramClauseCategory::WellFormed,
 233     };
 234     let wf_clause = Clause::ForAll(ty::Binder::bind(wf_clause));
 235
 236     // `forall<T> { WellFormed([T]) :- Implemented(T: Sized). }`
 237     tcx.mk_clauses(iter::once(wf_clause))
 238 }
 239
 240 fn wf_clause_for_array<'tcx>(
 241     tcx: ty::TyCtxt<'_, '_, 'tcx>,
 242     length: &'tcx ty::Const<'tcx>
 243 ) -> Clauses<'tcx> {
 244     let ty = generic_types::bound(tcx, 0);
 245     let array_ty = tcx.mk_ty(ty::Array(ty, length));
 246
 247     let sized_trait = match tcx.lang_items().sized_trait() {
 248         Some(def_id) => def_id,
 249         None => return ty::List::empty(),
 250     };
 251     let sized_implemented = ty::TraitRef {
 252         def_id: sized_trait,
 253         substs: tcx.mk_substs_trait(ty, ty::List::empty()),
 254     };
 255     let sized_implemented: DomainGoal<'_> = ty::TraitPredicate {
 256         trait_ref: sized_implemented
 257     }.lower();
 258
 259     let wf_clause = ProgramClause {
 260         goal: DomainGoal::WellFormed(WellFormed::Ty(array_ty)),
 261         hypotheses: tcx.mk_goals(
 262             iter::once(tcx.mk_goal(GoalKind::DomainGoal(sized_implemented)))
 263         ),
 264         category: ProgramClauseCategory::WellFormed,
 265     };
 266     let wf_clause = Clause::ForAll(ty::Binder::bind(wf_clause));
 267
 268     // `forall<T> { WellFormed([T; length]) :- Implemented(T: Sized). }`
 269     tcx.mk_clauses(iter::once(wf_clause))
 270 }
 271
 272 fn wf_clause_for_tuple<'tcx>(
 273     tcx: ty::TyCtxt<'_, '_, 'tcx>,
 274     arity: usize
 275 ) -> Clauses<'tcx> {
 276     let type_list = generic_types::type_list(tcx, arity);
 277     let tuple_ty = tcx.mk_ty(ty::Tuple(type_list));
 278
 279     let sized_trait = match tcx.lang_items().sized_trait() {
 280         Some(def_id) => def_id,
 281         None => return ty::List::empty(),
 282     };
 283
 284     // If `arity == 0` (i.e. the unit type) or `arity == 1`, this list of
 285     // hypotheses is actually empty.
 286     let sized_implemented = type_list[0 .. std::cmp::max(arity, 1) - 1].iter()
 287         .map(|ty| ty::TraitRef {
 288             def_id: sized_trait,
 289             substs: tcx.mk_substs_trait(*ty, ty::List::empty()),
 290         })
 291         .map(|trait_ref| ty::TraitPredicate { trait_ref })
 292         .map(|predicate| predicate.lower());
 293
 294     let wf_clause = ProgramClause {
 295         goal: DomainGoal::WellFormed(WellFormed::Ty(tuple_ty)),
 296         hypotheses: tcx.mk_goals(
 297             sized_implemented.map(|domain_goal| {
 298                 tcx.mk_goal(GoalKind::DomainGoal(domain_goal))
 299             })
 300         ),
 301         category: ProgramClauseCategory::WellFormed,
 302     };
 303     let wf_clause = Clause::ForAll(ty::Binder::bind(wf_clause));
 304
 305     // ```
 306     // forall<T1, ..., Tn-1, Tn> {
 307     //     WellFormed((T1, ..., Tn)) :-
 308     //         Implemented(T1: Sized),
 309     //         ...
 310     //         Implemented(Tn-1: Sized).
 311     // }
 312     // ```
 313     tcx.mk_clauses(iter::once(wf_clause))
 314 }
 315
 316 fn wf_clause_for_ref<'tcx>(
 317     tcx: ty::TyCtxt<'_, '_, 'tcx>,
 318     mutbl: hir::Mutability
 319 ) -> Clauses<'tcx> {
 320     let region = tcx.mk_region(
 321         ty::ReLateBound(ty::INNERMOST, ty::BoundRegion::BrAnon(0))
 322     );
 323     let ty = generic_types::bound(tcx, 1);
 324     let ref_ty = tcx.mk_ref(region, ty::TypeAndMut {
 325         ty,
 326         mutbl,
 327     });
 328
 329     let _outlives: DomainGoal<'_> = ty::OutlivesPredicate(ty, region).lower();
 330     let wf_clause = ProgramClause {
 331         goal: DomainGoal::WellFormed(WellFormed::Ty(ref_ty)),
 332         hypotheses: ty::List::empty(),
 333
 334         // FIXME: restore this later once we get better at handling regions
 335         // hypotheses: tcx.mk_goals(
 336         //     iter::once(tcx.mk_goal(outlives.into_goal()))
 337         // ),
 338         category: ProgramClauseCategory::WellFormed,
 339     };
 340     let wf_clause = Clause::ForAll(ty::Binder::bind(wf_clause));
 341
 342     // `forall<'a, T> { WellFormed(&'a T) :- Outlives(T: 'a). }`
 343     tcx.mk_clauses(iter::once(wf_clause))
 344 }
 345
 346 fn wf_clause_for_fn_def<'tcx>(
 347     tcx: ty::TyCtxt<'_, '_, 'tcx>,
 348     def_id: DefId
 349 ) -> Clauses<'tcx> {
 350     let fn_def = generic_types::fn_def(tcx, def_id);
 351
 352     let wf_clause = ProgramClause {
 353         goal: DomainGoal::WellFormed(WellFormed::Ty(fn_def)),
 354         hypotheses: ty::List::empty(),
 355         category: ProgramClauseCategory::WellFormed,
 356     };
 357     let wf_clause = Clause::ForAll(ty::Binder::bind(wf_clause));
 358
 359     // `forall <T1, ..., Tn+1> { WellFormed(fn some_fn(T1, ..., Tn) -> Tn+1). }`
 360     // where `def_id` maps to the `some_fn` function definition
 361     tcx.mk_clauses(iter::once(wf_clause))
 362 }
 363
 364 impl ChalkInferenceContext<'cx, 'gcx, 'tcx> {
 365     pub(super) fn program_clauses_impl(
 366         &self,
 367         environment: &Environment<'tcx>,
 368         goal: &DomainGoal<'tcx>,
 369     ) -> Vec<Clause<'tcx>> {
 370         use rustc::traits::WhereClause::*;
 371         use rustc::infer::canonical::OriginalQueryValues;
 372
 373         let goal = self.infcx.resolve_type_vars_if_possible(goal);
 374
 375         debug!("program_clauses(goal = {:?})", goal);
 376
 377         let mut clauses = match goal {
 378             DomainGoal::Holds(Implemented(trait_predicate)) => {
 379                 // These come from:
 380                 // * implementations of the trait itself (rule `Implemented-From-Impl`)
 381                 // * the trait decl (rule `Implemented-From-Env`)
 382
 383                 let mut clauses = vec![];
 384
 385                 assemble_clauses_from_impls(
 386                     self.infcx.tcx,
 387                     trait_predicate.def_id(),
 388                     &mut clauses
 389                 );
 390
 391                 if Some(trait_predicate.def_id()) == self.infcx.tcx.lang_items().sized_trait() {
 392                     assemble_builtin_sized_impls(
 393                         self.infcx.tcx,
 394                         trait_predicate.def_id(),
 395                         trait_predicate.self_ty(),
 396                         &mut clauses
 397                     );
 398                 }
 399
 400                 // FIXME: we need to add special rules for builtin impls:
 401                 // * `Copy` / `Clone`
 402                 // * `Sized`
 403                 // * `Unsize`
 404                 // * `Generator`
 405                 // * `FnOnce` / `FnMut` / `Fn`
 406                 // * trait objects
 407                 // * auto traits
 408
 409                 // Rule `Implemented-From-Env` will be computed from the environment.
 410                 clauses
 411             }
 412
 413             DomainGoal::Holds(ProjectionEq(projection_predicate)) => {
 414                 // These come from:
 415                 // * the assoc type definition (rule `ProjectionEq-Placeholder`)
 416                 // * normalization of the assoc ty values (rule `ProjectionEq-Normalize`)
 417                 // * implied bounds from trait definitions (rule `Implied-Bound-From-Trait`)
 418                 // * implied bounds from type definitions (rule `Implied-Bound-From-Type`)
 419
 420                 let clauses = self.infcx.tcx.program_clauses_for(
 421                     projection_predicate.projection_ty.item_def_id
 422                 ).into_iter()
 423
 424                     // only select `ProjectionEq-Placeholder` and `ProjectionEq-Normalize`
 425                     .filter(|clause| clause.category() == ProgramClauseCategory::Other)
 426
 427                     .cloned()
 428                     .collect::<Vec<_>>();
 429
 430                 // Rules `Implied-Bound-From-Trait` and `Implied-Bound-From-Type` will be computed
 431                 // from the environment.
 432                 clauses
 433             }
 434
 435             DomainGoal::Holds(RegionOutlives(..)) => {
 436                 // These come from:
 437                 // * implied bounds from trait definitions (rule `Implied-Bound-From-Trait`)
 438                 // * implied bounds from type definitions (rule `Implied-Bound-From-Type`)
 439
 440                 // All of these rules are computed in the environment.
 441                 vec![]
 442             }
 443
 444             DomainGoal::Holds(TypeOutlives(..)) => {
 445                 // These come from:
 446                 // * implied bounds from trait definitions (rule `Implied-Bound-From-Trait`)
 447                 // * implied bounds from type definitions (rule `Implied-Bound-From-Type`)
 448
 449                 // All of these rules are computed in the environment.
 450                 vec![]
 451             }
 452
 453             DomainGoal::WellFormed(WellFormed::Trait(trait_predicate)) => {
 454                 // These come from -- the trait decl (rule `WellFormed-TraitRef`).
 455                 self.infcx.tcx.program_clauses_for(trait_predicate.def_id())
 456                     .into_iter()
 457
 458                     // only select `WellFormed-TraitRef`
 459                     .filter(|clause| clause.category() == ProgramClauseCategory::WellFormed)
 460
 461                     .cloned()
 462                     .collect()
 463             }
 464
 465             DomainGoal::WellFormed(WellFormed::Ty(ty)) => {
 466                 // These come from:
 467                 // * the associated type definition if `ty` refers to an unnormalized
 468                 //   associated type (rule `WellFormed-AssocTy`)
 469                 // * custom rules for built-in types
 470                 // * the type definition otherwise (rule `WellFormed-Type`)
 471                 let clauses = match ty.sty {
 472                     ty::Projection(data) => {
 473                         self.infcx.tcx.program_clauses_for(data.item_def_id)
 474                     }
 475
 476                     // These types are always WF.
 477                     ty::Bool |
 478                     ty::Char |
 479                     ty::Int(..) |
 480                     ty::Uint(..) |
 481                     ty::Float(..) |
 482                     ty::Str |
 483                     ty::Param(..) |
 484                     ty::Placeholder(..) |
 485                     ty::Error |
 486                     ty::Never => {
 487                         let wf_clause = ProgramClause {
 488                             goal: DomainGoal::WellFormed(WellFormed::Ty(ty)),
 489                             hypotheses: ty::List::empty(),
 490                             category: ProgramClauseCategory::WellFormed,
 491                         };
 492                         let wf_clause = Clause::Implies(wf_clause);
 493
 494                         self.infcx.tcx.mk_clauses(iter::once(wf_clause))
 495                     }
 496
 497                     // Always WF (recall that we do not check for parameters to be WF).
 498                     ty::RawPtr(ptr) => wf_clause_for_raw_ptr(self.infcx.tcx, ptr.mutbl),
 499
 500                     // Always WF (recall that we do not check for parameters to be WF).
 501                     ty::FnPtr(fn_ptr) => {
 502                         let fn_ptr = fn_ptr.skip_binder();
 503                         wf_clause_for_fn_ptr(
 504                             self.infcx.tcx,
 505                             fn_ptr.inputs_and_output.len(),
 506                             fn_ptr.c_variadic,
 507                             fn_ptr.unsafety,
 508                             fn_ptr.abi
 509                         )
 510                     }
 511
 512                     // WF if inner type is `Sized`.
 513                     ty::Slice(..) => wf_clause_for_slice(self.infcx.tcx),
 514
 515                     // WF if inner type is `Sized`.
 516                     ty::Array(_, length) => wf_clause_for_array(self.infcx.tcx, length),
 517
 518                     // WF if all types but the last one are `Sized`.
 519                     ty::Tuple(types) => wf_clause_for_tuple(
 520                         self.infcx.tcx,
 521                         types.len()
 522                     ),
 523
 524                     // WF if `sub_ty` outlives `region`.
 525                     ty::Ref(_, _, mutbl) => wf_clause_for_ref(self.infcx.tcx, mutbl),
 526
 527                     ty::FnDef(def_id, ..) => wf_clause_for_fn_def(self.infcx.tcx, def_id),
 528
 529                     ty::Dynamic(..) => {
 530                         // FIXME: no rules yet for trait objects
 531                         ty::List::empty()
 532                     }
 533
 534                     ty::Adt(def, ..) => {
 535                         self.infcx.tcx.program_clauses_for(def.did)
 536                     }
 537
 538                     // FIXME: these are probably wrong
 539                     ty::Foreign(def_id) |
 540                     ty::Closure(def_id, ..) |
 541                     ty::Generator(def_id, ..) |
 542                     ty::Opaque(def_id, ..) => {
 543                         self.infcx.tcx.program_clauses_for(def_id)
 544                     }
 545
 546                     // Artificially trigger an ambiguity.
 547                     ty::Infer(..) => {
 548                         let tcx = self.infcx.tcx;
 549                         let types = [tcx.types.i32, tcx.types.u32, tcx.types.f32, tcx.types.f64];
 550                         let clauses = types.iter()
 551                             .cloned()
 552                             .map(|ty| ProgramClause {
 553                                 goal: DomainGoal::WellFormed(WellFormed::Ty(ty)),
 554                                 hypotheses: ty::List::empty(),
 555                                 category: ProgramClauseCategory::WellFormed,
 556                             })
 557                             .map(|clause| Clause::Implies(clause));
 558                         tcx.mk_clauses(clauses)
 559                     }
 560
 561                     ty::GeneratorWitness(..) |
 562                     ty::UnnormalizedProjection(..) |
 563                     ty::Bound(..) => {
 564                         bug!("unexpected type {:?}", ty)
 565                     }
 566                 };
 567
 568                 clauses.into_iter()
 569                     .filter(|clause| clause.category() == ProgramClauseCategory::WellFormed)
 570                     .cloned()
 571                     .collect()
 572             }
 573
 574             DomainGoal::FromEnv(FromEnv::Trait(..)) => {
 575                 // These come from:
 576                 // * implied bounds from trait definitions (rule `Implied-Bound-From-Trait`)
 577                 // * implied bounds from type definitions (rule `Implied-Bound-From-Type`)
 578                 // * implied bounds from assoc type defs (rules `Implied-Trait-From-AssocTy`,
 579                 //   `Implied-Bound-From-AssocTy` and `Implied-WC-From-AssocTy`)
 580
 581                 // All of these rules are computed in the environment.
 582                 vec![]
 583             }
 584
 585             DomainGoal::FromEnv(FromEnv::Ty(..)) => {
 586                 // There are no `FromEnv::Ty(..) :- ...` rules (this predicate only
 587                 // comes from the environment).
 588                 vec![]
 589             }
 590
 591             DomainGoal::Normalize(projection_predicate) => {
 592                 // These come from -- assoc ty values (rule `Normalize-From-Impl`).
 593                 let mut clauses = vec![];
 594
 595                 assemble_clauses_from_assoc_ty_values(
 596                     self.infcx.tcx,
 597                     projection_predicate.projection_ty.trait_ref(self.infcx.tcx).def_id,
 598                     &mut clauses
 599                 );
 600
 601                 clauses
 602             }
 603         };
 604
 605         debug!("program_clauses: clauses = {:?}", clauses);
 606         debug!("program_clauses: adding clauses from environment = {:?}", environment);
 607
 608         let mut _orig_query_values = OriginalQueryValues::default();
 609         let canonical_environment = self.infcx.canonicalize_query(
 610             environment,
 611             &mut _orig_query_values
 612         ).value;
 613         let env_clauses = self.infcx.tcx.program_clauses_for_env(canonical_environment);
 614
 615         debug!("program_clauses: env_clauses = {:?}", env_clauses);
 616
 617         clauses.extend(env_clauses.into_iter().cloned());
 618         clauses.extend(environment.clauses.iter().cloned());
 619         clauses
 620     }
 621 }