Generate clauses for super traits of opaque bounds

chalk-ir/src/could_match.rs

@@ -33,7 +33,7 @@ where
         struct MatchZipper<'i, I> {
             interner: &'i I,
             db: &'i dyn UnificationDatabase<I>,
-        };
+        }
 
         impl<'i, I: Interner> Zipper<'i, I> for MatchZipper<'i, I> {
             fn zip_tys(&mut self, variance: Variance, a: &Ty<I>, b: &Ty<I>) -> Fallible<()> {

chalk-solve/src/clauses.rs

@@ -18,6 +18,7 @@ mod dyn_ty;
 mod env_elaborator;
 mod generalize;
 pub mod program_clauses;
+mod super_traits;
 
 // yields the types "contained" in `app_ty`
 fn constituent_types<I: Interner>(db: &dyn RustIrDatabase<I>, ty: &TyKind<I>) -> Vec<Ty<I>> {

chalk-solve/src/clauses/dyn_ty.rs

@@ -1,11 +1,6 @@
-use rustc_hash::FxHashSet;
-
 use super::{builder::ClauseBuilder, generalize};
 use crate::RustIrDatabase;
-use chalk_ir::{
-    cast::Cast, fold::shift::Shift, interner::Interner, Binders, BoundVar, DebruijnIndex, TraitId,
-    TraitRef, Ty, TyKind, WhereClause,
-};
+use chalk_ir::{cast::Cast, interner::Interner, Ty, TyKind, WhereClause};
 
 /// If the self type `S` of an `Implemented` goal is a `dyn trait` type, we wish
 /// to generate program-clauses that indicates that it implements its own
@@ -67,123 +62,20 @@ pub(super) fn build_dyn_self_ty_clauses<I: Interner>(
                 .cloned()
                 .substitute(interner, &[self_ty.clone().cast(interner)]);
 
-            builder.push_binders(qwc, |builder, wc| match &wc {
+            builder.push_binders(qwc, |builder, bound| match &bound {
                 // For the implemented traits, we need to elaborate super traits and add where clauses from the trait
                 WhereClause::Implemented(trait_ref) => {
-                    push_dyn_ty_impl_clauses(db, builder, trait_ref.clone())
+                    super::super_traits::push_trait_super_clauses(
+                        builder.db,
+                        builder,
+                        trait_ref.clone(),
+                    )
                 }
-                // Associated item bindings are just taken as facts (?)
-                WhereClause::AliasEq(_) => builder.push_fact(wc),
+                // FIXME: Associated item bindings are just taken as facts (?)
+                WhereClause::AliasEq(_) => builder.push_fact(bound),
                 WhereClause::LifetimeOutlives(..) => {}
                 WhereClause::TypeOutlives(..) => {}
             });
         }
     });
 }
-
-/// Generate `Implemented` clauses for a `dyn Trait` type. We need to generate
-/// `Implemented` clauses for all super traits, and for each trait we require
-/// its where clauses. (See #203.)
-fn push_dyn_ty_impl_clauses<I: Interner>(
-    db: &dyn RustIrDatabase<I>,
-    builder: &mut ClauseBuilder<'_, I>,
-    trait_ref: TraitRef<I>,
-) {
-    let interner = db.interner();
-    // We have some `dyn Trait`, and some `trait SuperTrait: WC`
-    // which is a super trait of `Trait` (including actually
-    // just being the same trait); then we want to push
-    // `Implemented(dyn Trait: SuperTrait) :- WC`.
-
-    let super_trait_refs =
-        super_traits(db, trait_ref.trait_id).substitute(interner, &trait_ref.substitution);
-
-    for q_super_trait_ref in super_trait_refs {
-        builder.push_binders(q_super_trait_ref.clone(), |builder, super_trait_ref| {
-            let trait_datum = db.trait_datum(super_trait_ref.trait_id);
-            let wc = trait_datum
-                .where_clauses()
-                .cloned()
-                .substitute(interner, &super_trait_ref.substitution);
-            builder.push_clause(super_trait_ref, wc);
-        });
-    }
-}
-
-pub fn super_traits<I: Interner>(
-    db: &dyn RustIrDatabase<I>,
-    trait_id: TraitId<I>,
-) -> Binders<Vec<Binders<TraitRef<I>>>> {
-    let interner = db.interner();
-    let mut seen_traits = FxHashSet::default();
-    let trait_datum = db.trait_datum(trait_id);
-    let trait_ref = Binders::empty(
-        db.interner(),
-        TraitRef {
-            trait_id,
-            substitution: trait_datum
-                .binders
-                .identity_substitution(interner)
-                .shifted_in(interner),
-        },
-    );
-    let mut trait_refs = Vec::new();
-    go(db, trait_ref, &mut seen_traits, &mut trait_refs);
-
-    fn go<I: Interner>(
-        db: &dyn RustIrDatabase<I>,
-        trait_ref: Binders<TraitRef<I>>,
-        seen_traits: &mut FxHashSet<TraitId<I>>,
-        trait_refs: &mut Vec<Binders<TraitRef<I>>>,
-    ) {
-        let interner = db.interner();
-        let trait_id = trait_ref.skip_binders().trait_id;
-        // Avoid cycles
-        if !seen_traits.insert(trait_id) {
-            return;
-        }
-        trait_refs.push(trait_ref.clone());
-        let trait_datum = db.trait_datum(trait_id);
-        let super_trait_refs = trait_datum
-            .binders
-            .map_ref(|td| {
-                td.where_clauses
-                    .iter()
-                    .filter_map(|qwc| {
-                        qwc.as_ref().filter_map(|wc| match wc {
-                            WhereClause::Implemented(tr) => {
-                                let self_ty = tr.self_type_parameter(db.interner());
-
-                                // We're looking for where clauses
-                                // of the form `Self: Trait`. That's
-                                // ^1.0 because we're one binder in.
-                                if self_ty.bound_var(db.interner())
-                                    != Some(BoundVar::new(DebruijnIndex::ONE, 0))
-                                {
-                                    return None;
-                                }
-                                Some(tr.clone())
-                            }
-                            WhereClause::AliasEq(_) => None,
-                            WhereClause::LifetimeOutlives(..) => None,
-                            WhereClause::TypeOutlives(..) => None,
-                        })
-                    })
-                    .collect::<Vec<_>>()
-            })
-            // we skip binders on the trait_ref here and add them to the binders
-            // on the trait ref in the loop below. We could probably avoid this if
-            // we could turn the `Binders<Vec<>>` into a `Vec<Binders<>>` easily.
-            .substitute(db.interner(), &trait_ref.skip_binders().substitution);
-        for q_super_trait_ref in super_trait_refs {
-            // So now we need to combine the binders of trait_ref with the
-            // binders of super_trait_ref.
-            let actual_binders = Binders::new(trait_ref.binders.clone(), q_super_trait_ref);
-            let q_super_trait_ref = actual_binders.fuse_binders(interner);
-            go(db, q_super_trait_ref, seen_traits, trait_refs);
-        }
-        seen_traits.remove(&trait_id);
-    }
-
-    Binders::new(trait_datum.binders.binders.clone(), trait_refs)
-}

chalk-solve/src/clauses/program_clauses.rs

@@ -195,10 +195,20 @@ impl<I: Interner> ToProgramClauses<I> for OpaqueTyDatum<I> {
 
             let substitution = Substitution::from1(interner, alias_placeholder_ty);
             for bound in opaque_ty_bound.bounds {
-                // Implemented(!T<..>: Bound).
                 let bound_with_placeholder_ty = bound.substitute(interner, &substitution);
-                builder.push_binders(bound_with_placeholder_ty, |builder, bound| {
-                    builder.push_fact(bound);
+                builder.push_binders(bound_with_placeholder_ty, |builder, bound| match &bound {
+                    // For the implemented traits, we need to elaborate super traits and add where clauses from the trait
+                    WhereClause::Implemented(trait_ref) => {
+                        super::super_traits::push_trait_super_clauses(
+                            builder.db,
+                            builder,
+                            trait_ref.clone(),
+                        )
+                    }
+                    // FIXME: Associated item bindings are just taken as facts (?)
+                    WhereClause::AliasEq(_) => builder.push_fact(bound),
+                    WhereClause::LifetimeOutlives(..) => {}
+                    WhereClause::TypeOutlives(..) => {}
                 });
             }
         });

chalk-solve/src/clauses/super_traits.rs

@@ -0,0 +1,118 @@
+use rustc_hash::FxHashSet;
+
+use super::builder::ClauseBuilder;
+use crate::RustIrDatabase;
+use chalk_ir::{
+    fold::shift::Shift, interner::Interner, Binders, BoundVar, DebruijnIndex, TraitId, TraitRef,
+    WhereClause,
+};
+
+/// Generate `Implemented` clauses for `dyn Trait` and opaque types. We need to generate
+/// `Implemented` clauses for all super traits, and for each trait we require
+/// its where clauses. (See #203.)
+pub(super) fn push_trait_super_clauses<I: Interner>(
+    db: &dyn RustIrDatabase<I>,
+    builder: &mut ClauseBuilder<'_, I>,
+    trait_ref: TraitRef<I>,
+) {
+    let interner = db.interner();
+    // Given`trait SuperTrait: WC`, which is a super trait
+    // of `Trait` (including actually just being the same trait);
+    // then we want to push
+    // - for `dyn Trait`:
+    //     `Implemented(dyn Trait: SuperTrait) :- WC`.
+    // - for placeholder `!T` of `opaque type T: Trait = HiddenTy`:
+    //     `Implemented(!T: SuperTrait) :- WC`
+
+    let super_trait_refs =
+        super_traits(db, trait_ref.trait_id).substitute(interner, &trait_ref.substitution);
+
+    for q_super_trait_ref in super_trait_refs {
+        builder.push_binders(q_super_trait_ref.clone(), |builder, super_trait_ref| {
+            let trait_datum = db.trait_datum(super_trait_ref.trait_id);
+            let wc = trait_datum
+                .where_clauses()
+                .cloned()
+                .substitute(interner, &super_trait_ref.substitution);
+            builder.push_clause(super_trait_ref, wc);
+        });
+    }
+}
+
+pub fn super_traits<I: Interner>(
+    db: &dyn RustIrDatabase<I>,
+    trait_id: TraitId<I>,
+) -> Binders<Vec<Binders<TraitRef<I>>>> {
+    let interner = db.interner();
+    let mut seen_traits = FxHashSet::default();
+    let trait_datum = db.trait_datum(trait_id);
+    let trait_ref = Binders::empty(
+        db.interner(),
+        TraitRef {
+            trait_id,
+            substitution: trait_datum
+                .binders
+                .identity_substitution(interner)
+                .shifted_in(interner),
+        },
+    );
+    let mut trait_refs = Vec::new();
+    go(db, trait_ref, &mut seen_traits, &mut trait_refs);
+
+    fn go<I: Interner>(
+        db: &dyn RustIrDatabase<I>,
+        trait_ref: Binders<TraitRef<I>>,
+        seen_traits: &mut FxHashSet<TraitId<I>>,
+        trait_refs: &mut Vec<Binders<TraitRef<I>>>,
+    ) {
+        let interner = db.interner();
+        let trait_id = trait_ref.skip_binders().trait_id;
+        // Avoid cycles
+        if !seen_traits.insert(trait_id) {
+            return;
+        }
+        trait_refs.push(trait_ref.clone());
+        let trait_datum = db.trait_datum(trait_id);
+        let super_trait_refs = trait_datum
+            .binders
+            .map_ref(|td| {
+                td.where_clauses
+                    .iter()
+                    .filter_map(|qwc| {
+                        qwc.as_ref().filter_map(|wc| match wc {
+                            WhereClause::Implemented(tr) => {
+                                let self_ty = tr.self_type_parameter(db.interner());
+
+                                // We're looking for where clauses
+                                // of the form `Self: Trait`. That's
+                                // ^1.0 because we're one binder in.
+                                if self_ty.bound_var(db.interner())
+                                    != Some(BoundVar::new(DebruijnIndex::ONE, 0))
+                                {
+                                    return None;
+                                }
+                                Some(tr.clone())
+                            }
+                            WhereClause::AliasEq(_) => None,
+                            WhereClause::LifetimeOutlives(..) => None,
+                            WhereClause::TypeOutlives(..) => None,
+                        })
+                    })
+                    .collect::<Vec<_>>()
+            })
+            // we skip binders on the trait_ref here and add them to the binders
+            // on the trait ref in the loop below. We could probably avoid this if
+            // we could turn the `Binders<Vec<>>` into a `Vec<Binders<>>` easily.
+            .substitute(db.interner(), &trait_ref.skip_binders().substitution);
+        for q_super_trait_ref in super_trait_refs {
+            // So now we need to combine the binders of trait_ref with the
+            // binders of super_trait_ref.
+            let actual_binders = Binders::new(trait_ref.binders.clone(), q_super_trait_ref);
+            let q_super_trait_ref = actual_binders.fuse_binders(interner);
+            go(db, q_super_trait_ref, seen_traits, trait_refs);
+        }
+        seen_traits.remove(&trait_id);
+    }
+
+    Binders::new(trait_datum.binders.binders.clone(), trait_refs)
+}

tests/test/opaque_types.rs

@@ -263,3 +263,23 @@ fn opaque_auto_traits_indirect() {
         }
     }
 }
+
+#[test]
+fn opaque_super_trait() {
+    test! {
+        program {
+            trait Base {}
+            trait Super where Self: Base {}
+            impl Base for () {}
+            impl Super for () {}
+
+            opaque type Opaque: Super = ();
+        }
+
+        goal {
+            Opaque: Base
+        } yields {
+            "Unique"
+        }
+    }
+}