Write an initial version of the `program_clauses` callback

src/librustc_traits/chalk_context.rs

@@ -23,6 +23,7 @@
     Goal,
     GoalKind,
     Clause,
+    ProgramClauseCategory,
     QuantifierKind,
     Environment,
     InEnvironment,
@@ -30,6 +31,7 @@
 use rustc::ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
 use rustc::ty::subst::Kind;
 use rustc::ty::{self, TyCtxt};
+use rustc::hir::def_id::DefId;
 
 use std::fmt::{self, Debug};
 use std::marker::PhantomData;
@@ -330,46 +332,230 @@ impl context::UnificationOps<ChalkArenas<'gcx>, ChalkArenas<'tcx>>
 {
     fn program_clauses(
         &self,
-        _environment: &Environment<'tcx>,
+        environment: &Environment<'tcx>,
         goal: &DomainGoal<'tcx>,
     ) -> Vec<Clause<'tcx>> {
         use rustc::traits::WhereClause::*;
 
-        match goal {
-            DomainGoal::Holds(Implemented(_trait_predicate)) => {
+        fn assemble_clauses_from_impls<'tcx>(
+            tcx: ty::TyCtxt<'_, '_, 'tcx>,
+            trait_def_id: DefId,
+            clauses: &mut Vec<Clause<'tcx>>
+        ) {
+            tcx.for_each_impl(trait_def_id, |impl_def_id| {
+                clauses.extend(
+                    tcx.program_clauses_for(impl_def_id)
+                        .into_iter()
+                        .cloned()
+                );
+            });
+        }
+
+        fn assemble_clauses_from_assoc_ty_values<'tcx>(
+            tcx: ty::TyCtxt<'_, '_, 'tcx>,
+            trait_def_id: DefId,
+            clauses: &mut Vec<Clause<'tcx>>
+        ) {
+            tcx.for_each_impl(trait_def_id, |impl_def_id| {
+                for def_id in tcx.associated_item_def_ids(impl_def_id).iter() {
+                    clauses.extend(
+                        tcx.program_clauses_for(*def_id)
+                            .into_iter()
+                            .cloned()
+                    );
+                }
+            });
+        }
+
+        let mut clauses = match goal {
+            DomainGoal::Holds(Implemented(trait_predicate)) => {
+                // These come from:
+                // * implementations of the trait itself (rule `Implemented-From-Impl`)
+                // * the trait decl (rule `Implemented-From-Env`)
+
+                let mut clauses = vec![];
+                assemble_clauses_from_impls(
+                    self.infcx.tcx,
+                    trait_predicate.def_id(),
+                    &mut clauses
+                );
+
+                // FIXME: we need to add special rules for builtin impls:
+                // * `Copy` / `Clone`
+                // * `Sized`
+                // * `Unsize`
+                // * `Generator`
+                // * `FnOnce` / `FnMut` / `Fn`
+                // * trait objects
+                // * auto traits
+
+                // Rule `Implemented-From-Env` will be computed from the environment.
+                clauses
+            }
+
+            DomainGoal::Holds(ProjectionEq(projection_predicate)) => {
+                // These come from:
+                // * the assoc type definition (rule `ProjectionEq-Placeholder`)
+                // * normalization of the assoc ty values (rule `ProjectionEq-Normalize`)
+                // * implied bounds from trait definitions (rule `Implied-Bound-From-Trait`)
+                // * implied bounds from type definitions (rule `Implied-Bound-From-Type`)
+
+                let clauses = self.infcx.tcx.program_clauses_for(
+                    projection_predicate.projection_ty.item_def_id
+                ).into_iter()
+
+                    // only select `ProjectionEq-Placeholder` and `ProjectionEq-Normalize`
+                    .filter(|clause| clause.category() == ProgramClauseCategory::Other)
+
+                    .cloned()
+                    .collect::<Vec<_>>();
+
+                // Rules `Implied-Bound-From-Trait` and `Implied-Bound-From-Type` will be computed
+                // from the environment.
+                clauses
+            }
+
+            DomainGoal::Holds(RegionOutlives(..)) => {
                 // These come from:
-                //
-                // - Trait definitions (implied bounds)
-                // - Implementations of the trait itself
-                panic!()
+                // * implied bounds from trait definitions (rule `Implied-Bound-From-Trait`)
+                // * implied bounds from type definitions (rule `Implied-Bound-From-Type`)
+
+                // All of these rules are computed in the environment.
+                vec![]
             }
 
-            DomainGoal::Holds(ProjectionEq(_projection_predicate)) => {
+            DomainGoal::Holds(TypeOutlives(..)) => {
                 // These come from:
-                panic!()
+                // * implied bounds from trait definitions (rule `Implied-Bound-From-Trait`)
+                // * implied bounds from type definitions (rule `Implied-Bound-From-Type`)
+
+                // All of these rules are computed in the environment.
+                vec![]
             }
 
-            DomainGoal::Holds(RegionOutlives(_region_outlives)) => {
-                panic!()
+            DomainGoal::WellFormed(WellFormed::Trait(trait_predicate)) => {
+                // These come from -- the trait decl (rule `WellFormed-TraitRef`).
+                self.infcx.tcx.program_clauses_for(trait_predicate.def_id())
+                    .into_iter()
+
+                    // only select `WellFormed-TraitRef`
+                    .filter(|clause| clause.category() == ProgramClauseCategory::WellFormed)
+
+                    .cloned()
+                    .collect()
             }
 
-            DomainGoal::Holds(TypeOutlives(_type_outlives)) => {
-                panic!()
+            DomainGoal::WellFormed(WellFormed::Ty(ty)) => {
+                // These come from:
+                // * the associated type definition if `ty` refers to an unnormalized
+                //   associated type (rule `WellFormed-AssocTy`)
+                // * custom rules for built-in types
+                // * the type definition otherwise (rule `WellFormed-Type`)
+                let clauses = match ty.sty {
+                    ty::Projection(data) => {
+                        self.infcx.tcx.program_clauses_for(data.item_def_id)
+                    }
+
+                    // These types are always WF (recall that we do not check
+                    // for parameters to be WF)
+                    ty::Bool |
+                    ty::Char |
+                    ty::Int(..) |
+                    ty::Uint(..) |
+                    ty::Float(..) |
+                    ty::Str |
+                    ty::RawPtr(..) |
+                    ty::FnPtr(..) |
+                    ty::Param(..) |
+                    ty::Never => {
+                        ty::List::empty()
+                    }
+
+                    // WF if inner type is `Sized`
+                    ty::Slice(..) |
+                    ty::Array(..) => {
+                        ty::List::empty()
+                    }
+
+                    ty::Tuple(..) => {
+                        ty::List::empty()
+                    }
+
+                    // WF if `sub_ty` outlives `region`
+                    ty::Ref(..) => {
+                        ty::List::empty()
+                    }
+
+                    ty::Dynamic(..) => {
+                        // FIXME: no rules yet for trait objects
+                        ty::List::empty()
+                    }
+
+                    ty::Adt(def, ..) => {
+                        self.infcx.tcx.program_clauses_for(def.did)
+                    }
+
+                    ty::Foreign(def_id) |
+                    ty::FnDef(def_id, ..) |
+                    ty::Closure(def_id, ..) |
+                    ty::Generator(def_id, ..) |
+                    ty::Opaque(def_id, ..) => {
+                        self.infcx.tcx.program_clauses_for(def_id)
+                    }
+
+                    ty::GeneratorWitness(..) |
+                    ty::UnnormalizedProjection(..) |
+                    ty::Infer(..) |
+                    ty::Error => {
+                        bug!("unexpected type {:?}", ty)
+                    }
+                };
+
+                clauses.into_iter()
+                    .filter(|clause| clause.category() == ProgramClauseCategory::WellFormed)
+                    .cloned()
+                    .collect()
             }
 
-            DomainGoal::WellFormed(WellFormed::Trait(_trait_predicate)) => {
-                // These come from -- the trait decl.
-                panic!()
+            DomainGoal::FromEnv(FromEnv::Trait(..)) => {
+                // These come from:
+                // * implied bounds from trait definitions (rule `Implied-Bound-From-Trait`)
+                // * implied bounds from type definitions (rule `Implied-Bound-From-Type`)
+                // * implied bounds from assoc type defs (rules `Implied-Trait-From-AssocTy`,
+                //   `Implied-Bound-From-AssocTy` and `Implied-WC-From-AssocTy`)
+
+                // All of these rules are computed in the environment.
+                vec![]
             }
 
-            DomainGoal::WellFormed(WellFormed::Ty(_ty)) => panic!(),
+            DomainGoal::FromEnv(FromEnv::Ty(..)) => {
+                // There are no `FromEnv::Ty(..) :- ...` rules (this predicate only
+                // comes from the environment).
+                vec![]
+            }
 
-            DomainGoal::FromEnv(FromEnv::Trait(_trait_predicate)) => panic!(),
+            DomainGoal::Normalize(projection_predicate) => {
+                // These come from -- assoc ty values (rule `Normalize-From-Impl`).
+                let mut clauses = vec![];
 
-            DomainGoal::FromEnv(FromEnv::Ty(_ty)) => panic!(),
+                assemble_clauses_from_assoc_ty_values(
+                    self.infcx.tcx,
+                    projection_predicate.projection_ty.trait_ref(self.infcx.tcx).def_id,
+                    &mut clauses
+                );
 
-            DomainGoal::Normalize(_) => panic!(),
-        }
+                clauses
+            }
+        };
+
+        let environment = self.infcx.tcx.lift_to_global(environment)
+            .expect("environment is not global");
+        clauses.extend(
+            self.infcx.tcx.program_clauses_for_env(environment)
+                .into_iter()
+                .cloned()
+        );
+        clauses
     }
 
     fn instantiate_binders_universally(

src/librustc_traits/lowering/environment.rs

@@ -86,13 +86,16 @@ fn visit_ty(&mut self, ty: Ty<'tcx>) {
             ty::Slice(..) |
             ty::RawPtr(..) |
             ty::FnPtr(..) |
-            ty::Never |
             ty::Tuple(..) |
+            ty::Never |
+            ty::Param(..) => (),
+
             ty::GeneratorWitness(..) |
             ty::UnnormalizedProjection(..) |
-            ty::Param(..) |
             ty::Infer(..) |
-            ty::Error => (),
+            ty::Error => {
+                bug!("unexpected type {:?}", ty);
+            }
         }
     }
 

src/librustc_traits/lowering/mod.rs

@@ -433,7 +433,7 @@ pub fn program_clauses_for_associated_type_def<'a, 'tcx>(
     let wf_clause = ProgramClause {
         goal: DomainGoal::WellFormed(WellFormed::Ty(placeholder_ty)),
         hypotheses: tcx.mk_goals(iter::once(hypothesis)),
-        category: ProgramClauseCategory::Other,
+        category: ProgramClauseCategory::WellFormed,
     };
 
     // Rule Implied-Trait-From-AssocTy