Auto merge of #49837 - nikomatsakis:chalkify-engine, r=scalexm

work towards chalkify-ing the engine

This work towards creating a "all program clauses needed for this goal" query

r? @scalexm

Author: bors

src/librustc/dep_graph/dep_node.rs

@@ -655,6 +655,7 @@ define_dep_nodes!( <'tcx>
     [input] Features,
 
     [] ProgramClausesFor(DefId),
+    [] ProgramClausesForEnv(ParamEnv<'tcx>),
     [] WasmImportModuleMap(CrateNum),
     [] ForeignModules(CrateNum),
 

src/librustc/hir/map/def_collector.rs

@@ -107,8 +107,9 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
         // information we encapsulate into
         let def_data = match i.node {
             ItemKind::Impl(..) => DefPathData::Impl,
+            ItemKind::Trait(..) => DefPathData::Trait(i.ident.name.as_str()),
             ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) |
-            ItemKind::Trait(..) | ItemKind::TraitAlias(..) |
+            ItemKind::TraitAlias(..) |
             ItemKind::ExternCrate(..) | ItemKind::ForeignMod(..) | ItemKind::Ty(..) =>
                 DefPathData::TypeNs(i.ident.name.as_str()),
             ItemKind::Mod(..) if i.ident == keywords::Invalid.ident() => {
@@ -222,7 +223,7 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
         let def_data = match ti.node {
             TraitItemKind::Method(..) | TraitItemKind::Const(..) =>
                 DefPathData::ValueNs(ti.ident.name.as_str()),
-            TraitItemKind::Type(..) => DefPathData::TypeNs(ti.ident.name.as_str()),
+            TraitItemKind::Type(..) => DefPathData::AssocTypeInTrait(ti.ident.name.as_str()),
             TraitItemKind::Macro(..) => return self.visit_macro_invoc(ti.id, false),
         };
 
@@ -240,7 +241,7 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
         let def_data = match ii.node {
             ImplItemKind::Method(..) | ImplItemKind::Const(..) =>
                 DefPathData::ValueNs(ii.ident.name.as_str()),
-            ImplItemKind::Type(..) => DefPathData::TypeNs(ii.ident.name.as_str()),
+            ImplItemKind::Type(..) => DefPathData::AssocTypeInImpl(ii.ident.name.as_str()),
             ImplItemKind::Macro(..) => return self.visit_macro_invoc(ii.id, false),
         };
 

src/librustc/hir/map/definitions.rs

@@ -212,6 +212,9 @@ impl DefKey {
         ::std::mem::discriminant(data).hash(&mut hasher);
         match *data {
             DefPathData::TypeNs(name) |
+            DefPathData::Trait(name) |
+            DefPathData::AssocTypeInTrait(name) |
+            DefPathData::AssocTypeInImpl(name) |
             DefPathData::ValueNs(name) |
             DefPathData::Module(name) |
             DefPathData::MacroDef(name) |
@@ -358,6 +361,12 @@ pub enum DefPathData {
     // Different kinds of items and item-like things:
     /// An impl
     Impl,
+    /// A trait
+    Trait(InternedString),
+    /// An associated type **declaration** (i.e., in a trait)
+    AssocTypeInTrait(InternedString),
+    /// An associated type **value** (i.e., in an impl)
+    AssocTypeInImpl(InternedString),
     /// Something in the type NS
     TypeNs(InternedString),
     /// Something in the value NS
@@ -639,6 +648,9 @@ impl DefPathData {
         use self::DefPathData::*;
         match *self {
             TypeNs(name) |
+            Trait(name) |
+            AssocTypeInTrait(name) |
+            AssocTypeInImpl(name) |
             ValueNs(name) |
             Module(name) |
             MacroDef(name) |
@@ -663,6 +675,9 @@ impl DefPathData {
         use self::DefPathData::*;
         let s = match *self {
             TypeNs(name) |
+            Trait(name) |
+            AssocTypeInTrait(name) |
+            AssocTypeInImpl(name) |
             ValueNs(name) |
             Module(name) |
             MacroDef(name) |

src/librustc/ich/impls_ty.rs

@@ -1352,10 +1352,6 @@ impl_stable_hash_for!(
     }
 );
 
-impl_stable_hash_for!(struct infer::canonical::QueryRegionConstraints<'tcx> {
-    region_outlives, ty_outlives
-});
-
 impl_stable_hash_for!(enum infer::canonical::Certainty {
     Proven, Ambiguous
 });
@@ -1417,6 +1413,7 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for traits::Goal<'tcx> {
                 quantifier.hash_stable(hcx, hasher);
                 goal.hash_stable(hcx, hasher);
             },
+            CannotProve => { },
         }
     }
 }

src/librustc/infer/canonical.rs

@@ -42,7 +42,6 @@ use traits::{Obligation, ObligationCause, PredicateObligation};
 use ty::{self, CanonicalVar, Lift, Region, Slice, Ty, TyCtxt, TypeFlags};
 use ty::subst::{Kind, UnpackedKind};
 use ty::fold::{TypeFoldable, TypeFolder};
-use util::captures::Captures;
 
 use rustc_data_structures::indexed_vec::IndexVec;
 use rustc_data_structures::fx::FxHashMap;
@@ -121,7 +120,7 @@ pub enum CanonicalTyVarKind {
 #[derive(Clone, Debug)]
 pub struct QueryResult<'tcx, R> {
     pub var_values: CanonicalVarValues<'tcx>,
-    pub region_constraints: QueryRegionConstraints<'tcx>,
+    pub region_constraints: Vec<QueryRegionConstraint<'tcx>>,
     pub certainty: Certainty,
     pub value: R,
 }
@@ -181,12 +180,7 @@ impl<'tcx, R> Canonical<'tcx, QueryResult<'tcx, R>> {
     }
 }
 
-/// Subset of `RegionConstraintData` produced by trait query.
-#[derive(Clone, Debug, Default)]
-pub struct QueryRegionConstraints<'tcx> {
-    pub region_outlives: Vec<(Region<'tcx>, Region<'tcx>)>,
-    pub ty_outlives: Vec<(Ty<'tcx>, Region<'tcx>)>,
-}
+pub type QueryRegionConstraint<'tcx> = ty::Binder<ty::OutlivesPredicate<Kind<'tcx>, Region<'tcx>>>;
 
 /// Trait implemented by values that can be canonicalized. It mainly
 /// serves to identify the interning table we will use.
@@ -382,35 +376,29 @@ impl<'cx, 'gcx, 'tcx> InferCtxt<'cx, 'gcx, 'tcx> {
         &'a self,
         cause: &'a ObligationCause<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
-        unsubstituted_region_constraints: &'a QueryRegionConstraints<'tcx>,
+        unsubstituted_region_constraints: &'a [QueryRegionConstraint<'tcx>],
         result_subst: &'a CanonicalVarValues<'tcx>,
-    ) -> impl Iterator<Item = PredicateObligation<'tcx>> + Captures<'gcx> + 'a {
-        let QueryRegionConstraints {
-            region_outlives,
-            ty_outlives,
-        } = unsubstituted_region_constraints;
-
-        let region_obligations = region_outlives.iter().map(move |(r1, r2)| {
-            let r1 = substitute_value(self.tcx, result_subst, r1);
-            let r2 = substitute_value(self.tcx, result_subst, r2);
-            Obligation::new(
-                cause.clone(),
-                param_env,
-                ty::Predicate::RegionOutlives(ty::Binder(ty::OutlivesPredicate(r1, r2))),
-            )
-        });
-
-        let ty_obligations = ty_outlives.iter().map(move |(t1, r2)| {
-            let t1 = substitute_value(self.tcx, result_subst, t1);
+    ) -> impl Iterator<Item = PredicateObligation<'tcx>> + 'a {
+        Box::new(unsubstituted_region_constraints.iter().map(move |constraint| {
+            let ty::OutlivesPredicate(k1, r2) = constraint.skip_binder(); // restored below
+            let k1 = substitute_value(self.tcx, result_subst, k1);
             let r2 = substitute_value(self.tcx, result_subst, r2);
-            Obligation::new(
-                cause.clone(),
-                param_env,
-                ty::Predicate::TypeOutlives(ty::Binder(ty::OutlivesPredicate(t1, r2))),
-            )
-        });
-
-        region_obligations.chain(ty_obligations)
+            match k1.unpack() {
+                UnpackedKind::Lifetime(r1) =>
+                    Obligation::new(
+                        cause.clone(),
+                        param_env,
+                        ty::Predicate::RegionOutlives(ty::Binder(ty::OutlivesPredicate(r1, r2))),
+                    ),
+
+                UnpackedKind::Type(t1) =>
+                    Obligation::new(
+                        cause.clone(),
+                        param_env,
+                        ty::Predicate::TypeOutlives(ty::Binder(ty::OutlivesPredicate(t1, r2))),
+                    ),
+            }
+        })) as Box<dyn Iterator<Item = _>>
     }
 
     /// Given two sets of values for the same set of canonical variables, unify them.
@@ -913,19 +901,6 @@ BraceStructTypeFoldableImpl! {
     }
 }
 
-BraceStructTypeFoldableImpl! {
-    impl<'tcx> TypeFoldable<'tcx> for QueryRegionConstraints<'tcx> {
-        region_outlives, ty_outlives
-    }
-}
-
-BraceStructLiftImpl! {
-    impl<'a, 'tcx> Lift<'tcx> for QueryRegionConstraints<'a> {
-        type Lifted = QueryRegionConstraints<'tcx>;
-        region_outlives, ty_outlives
-    }
-}
-
 BraceStructTypeFoldableImpl! {
     impl<'tcx, R> TypeFoldable<'tcx> for QueryResult<'tcx, R> {
         var_values, region_constraints, certainty, value

src/librustc/session/config.rs

@@ -1289,6 +1289,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "tell the linker to strip debuginfo when building without debuginfo enabled."),
     share_generics: Option<bool> = (None, parse_opt_bool, [TRACKED],
           "make the current crate share its generic instantiations"),
+    chalk: bool = (false, parse_bool, [TRACKED],
+          "enable the experimental Chalk-based trait solving engine"),
 }
 
 pub fn default_lib_output() -> CrateType {

src/librustc/traits/mod.rs

@@ -282,13 +282,16 @@ pub enum QuantifierKind {
 
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 pub enum Goal<'tcx> {
-    Implies(&'tcx Slice<Clause<'tcx>>, &'tcx Goal<'tcx>),
+    Implies(Clauses<'tcx>, &'tcx Goal<'tcx>),
     And(&'tcx Goal<'tcx>, &'tcx Goal<'tcx>),
     Not(&'tcx Goal<'tcx>),
     DomainGoal(DomainGoal<'tcx>),
-    Quantified(QuantifierKind, ty::Binder<&'tcx Goal<'tcx>>)
+    Quantified(QuantifierKind, ty::Binder<&'tcx Goal<'tcx>>),
+    CannotProve,
 }
 
+pub type Goals<'tcx> = &'tcx Slice<Goal<'tcx>>;
+
 impl<'tcx> Goal<'tcx> {
     pub fn from_poly_domain_goal<'a>(
         domain_goal: PolyDomainGoal<'tcx>,
@@ -318,6 +321,9 @@ pub enum Clause<'tcx> {
     ForAll(ty::Binder<ProgramClause<'tcx>>),
 }
 
+/// Multiple clauses.
+pub type Clauses<'tcx> = &'tcx Slice<Clause<'tcx>>;
+
 /// A "program clause" has the form `D :- G1, ..., Gn`. It is saying
 /// that the domain goal `D` is true if `G1...Gn` are provable. This
 /// is equivalent to the implication `G1..Gn => D`; we usually write
@@ -330,7 +336,7 @@ pub struct ProgramClause<'tcx> {
     pub goal: DomainGoal<'tcx>,
 
     /// ...if we can prove these hypotheses (there may be no hypotheses at all):
-    pub hypotheses: &'tcx Slice<Goal<'tcx>>,
+    pub hypotheses: Goals<'tcx>,
 }
 
 pub type Selection<'tcx> = Vtable<'tcx, PredicateObligation<'tcx>>;

src/librustc/traits/structural_impls.rs

@@ -491,6 +491,7 @@ impl<'tcx> fmt::Display for traits::Goal<'tcx> {
                 // FIXME: appropriate binder names
                 write!(fmt, "{}<> {{ {} }}", qkind, goal.skip_binder())
             }
+            CannotProve => write!(fmt, "CannotProve"),
         }
     }
 }
@@ -557,6 +558,7 @@ EnumTypeFoldableImpl! {
         (traits::Goal::Not)(goal),
         (traits::Goal::DomainGoal)(domain_goal),
         (traits::Goal::Quantified)(qkind, goal),
+        (traits::Goal::CannotProve),
     }
 }
 

src/librustc/ty/context.rs

@@ -38,7 +38,7 @@ use ty::subst::{Kind, Substs};
 use ty::ReprOptions;
 use ty::Instance;
 use traits;
-use traits::{Clause, Goal};
+use traits::{Clause, Clauses, Goal, Goals};
 use ty::{self, Ty, TypeAndMut};
 use ty::{TyS, TypeVariants, Slice};
 use ty::{AdtKind, AdtDef, ClosureSubsts, GeneratorInterior, Region, Const};
@@ -2517,15 +2517,15 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         }
     }
 
-    pub fn intern_clauses(self, ts: &[Clause<'tcx>]) -> &'tcx Slice<Clause<'tcx>> {
+    pub fn intern_clauses(self, ts: &[Clause<'tcx>]) -> Clauses<'tcx> {
         if ts.len() == 0 {
             Slice::empty()
         } else {
             self._intern_clauses(ts)
         }
     }
 
-    pub fn intern_goals(self, ts: &[Goal<'tcx>]) -> &'tcx Slice<Goal<'tcx>> {
+    pub fn intern_goals(self, ts: &[Goal<'tcx>]) -> Goals<'tcx> {
         if ts.len() == 0 {
             Slice::empty()
         } else {
@@ -2579,13 +2579,11 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         self.mk_substs(iter::once(s).chain(t.into_iter().cloned()).map(Kind::from))
     }
 
-    pub fn mk_clauses<I: InternAs<[Clause<'tcx>],
-        &'tcx Slice<Clause<'tcx>>>>(self, iter: I) -> I::Output {
+    pub fn mk_clauses<I: InternAs<[Clause<'tcx>], Clauses<'tcx>>>(self, iter: I) -> I::Output {
         iter.intern_with(|xs| self.intern_clauses(xs))
     }
 
-    pub fn mk_goals<I: InternAs<[Goal<'tcx>],
-        &'tcx Slice<Goal<'tcx>>>>(self, iter: I) -> I::Output {
+    pub fn mk_goals<I: InternAs<[Goal<'tcx>], Goals<'tcx>>>(self, iter: I) -> I::Output {
         iter.intern_with(|xs| self.intern_goals(xs))
     }
 

src/librustc/ty/item_path.rs

@@ -204,6 +204,9 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             // finer-grained distinctions, e.g. between enum/struct).
             data @ DefPathData::Misc |
             data @ DefPathData::TypeNs(..) |
+            data @ DefPathData::Trait(..) |
+            data @ DefPathData::AssocTypeInTrait(..) |
+            data @ DefPathData::AssocTypeInImpl(..) |
             data @ DefPathData::ValueNs(..) |
             data @ DefPathData::Module(..) |
             data @ DefPathData::TypeParam(..) |