completions: speed up completions by filtering non-applicable traits

crates/hir-ty/src/infer/unify.rs

@@ -457,6 +457,7 @@ impl<'a> InferenceTable<'a> {
     }
 
     /// Unify two relatable values (e.g. `Ty`) and register new trait goals that arise from that.
+    #[tracing::instrument(skip_all)]
     pub(crate) fn unify<T: ?Sized + Zip<Interner>>(&mut self, ty1: &T, ty2: &T) -> bool {
         let result = match self.try_unify(ty1, ty2) {
             Ok(r) => r,

crates/hir-ty/src/method_resolution.rs

@@ -254,6 +254,11 @@ impl TraitImpls {
             .flat_map(|v| v.iter().copied())
     }
 
+    /// Queries whether `self_ty` has potentially applicable implementations of `trait_`.
+    pub fn has_impls_for_trait_and_self_ty(&self, trait_: TraitId, self_ty: TyFingerprint) -> bool {
+        self.for_trait_and_self_ty(trait_, self_ty).next().is_some()
+    }
+
     pub fn all_impls(&self) -> impl Iterator<Item = ImplId> + '_ {
         self.map.values().flat_map(|map| map.values().flat_map(|v| v.iter().copied()))
     }
@@ -1170,7 +1175,7 @@ fn iterate_trait_method_candidates(
         for &(_, item) in data.items.iter() {
             // Don't pass a `visible_from_module` down to `is_valid_candidate`,
             // since only inherent methods should be included into visibility checking.
-            let visible = match is_valid_candidate(table, name, receiver_ty, item, self_ty, None) {
+            let visible = match is_valid_method_candidate(table, name, receiver_ty, item, self_ty) {
                 IsValidCandidate::Yes => true,
                 IsValidCandidate::NotVisible => false,
                 IsValidCandidate::No => continue,
@@ -1414,6 +1419,74 @@ fn is_valid_candidate(
     }
 }
 
+/// Checks whether a given `AssocItemId` is applicable for `receiver_ty`.
+///
+/// This method should *only* be called by [`iterate_trait_method_candidates`],
+/// as it is responsible for determining applicability in completions.
+#[tracing::instrument(skip_all, fields(name))]
+fn is_valid_method_candidate(
+    table: &mut InferenceTable<'_>,
+    name: Option<&Name>,
+    receiver_ty: Option<&Ty>,
+    item: AssocItemId,
+    self_ty: &Ty,
+) -> IsValidCandidate {
+    let db = table.db;
+    match item {
+        AssocItemId::FunctionId(fn_id) => {
+            let data = db.function_data(fn_id);
+
+            check_that!(name.map_or(true, |n| n == &data.name));
+
+            table.run_in_snapshot(|table| {
+                let container = fn_id.lookup(db.upcast()).container;
+                let (impl_subst, expect_self_ty) = match container {
+                    ItemContainerId::ImplId(it) => {
+                        let subst = TyBuilder::subst_for_def(db, it, None)
+                            .fill_with_inference_vars(table)
+                            .build();
+                        let self_ty = db.impl_self_ty(it).substitute(Interner, &subst);
+                        (subst, self_ty)
+                    }
+                    ItemContainerId::TraitId(it) => {
+                        let subst = TyBuilder::subst_for_def(db, it, None)
+                            .fill_with_inference_vars(table)
+                            .build();
+                        let self_ty = subst.at(Interner, 0).assert_ty_ref(Interner).clone();
+                        (subst, self_ty)
+                    }
+                    _ => unreachable!(),
+                };
+
+                check_that!(table.unify(&expect_self_ty, self_ty));
+
+                if let Some(receiver_ty) = receiver_ty {
+                    check_that!(data.has_self_param());
+
+                    let fn_subst = TyBuilder::subst_for_def(db, fn_id, Some(impl_subst.clone()))
+                        .fill_with_inference_vars(table)
+                        .build();
+
+                    let sig = db.callable_item_signature(fn_id.into());
+                    let expected_receiver =
+                        sig.map(|s| s.params()[0].clone()).substitute(Interner, &fn_subst);
+
+                    check_that!(table.unify(receiver_ty, &expected_receiver));
+                }
+
+                IsValidCandidate::Yes
+            })
+        }
+        AssocItemId::ConstId(c) => {
+            check_that!(receiver_ty.is_none());
+            check_that!(name.map_or(true, |n| db.const_data(c).name.as_ref() == Some(n)));
+
+            IsValidCandidate::Yes
+        }
+        _ => IsValidCandidate::No,
+    }
+}
+
 enum IsValidCandidate {
     Yes,
     No,
@@ -1441,6 +1514,8 @@ fn is_valid_fn_candidate(
     }
     table.run_in_snapshot(|table| {
         let container = fn_id.lookup(db.upcast()).container;
+
+        let _p = tracing::span!(tracing::Level::INFO, "subst_for_def").entered();
         let (impl_subst, expect_self_ty) = match container {
             ItemContainerId::ImplId(it) => {
                 let subst =
@@ -1460,6 +1535,7 @@ fn is_valid_fn_candidate(
         check_that!(table.unify(&expect_self_ty, self_ty));
 
         if let Some(receiver_ty) = receiver_ty {
+            let _p = tracing::span!(tracing::Level::INFO, "check_receiver_ty").entered();
             check_that!(data.has_self_param());
 
             let fn_subst = TyBuilder::subst_for_def(db, fn_id, Some(impl_subst.clone()))
@@ -1474,6 +1550,7 @@ fn is_valid_fn_candidate(
         }
 
         if let ItemContainerId::ImplId(impl_id) = container {
+            let _p = tracing::span!(tracing::Level::INFO, "check_item_container").entered();
             // We need to consider the bounds on the impl to distinguish functions of the same name
             // for a type.
             let predicates = db.generic_predicates(impl_id.into());

crates/hir-ty/src/traits.rs

@@ -139,6 +139,7 @@ fn solve(
     block: Option<BlockId>,
     goal: &chalk_ir::UCanonical<chalk_ir::InEnvironment<chalk_ir::Goal<Interner>>>,
 ) -> Option<chalk_solve::Solution<Interner>> {
+    let _p = tracing::span!(tracing::Level::INFO, "solve", ?krate, ?block).entered();
     let context = ChalkContext { db, krate, block };
     tracing::debug!("solve goal: {:?}", goal);
     let mut solver = create_chalk_solver();