6 files changed, 15 insertions, 8 deletions

diff --git a/crates/hir_ty/Cargo.toml b/crates/hir_ty/Cargo.toml
index 0ef27cd37..030b7eebe 100644
--- a/crates/hir_ty/Cargo.toml
+++ b/crates/hir_ty/Cargo.toml
@@ -12,7 +12,7 @@ doctest = false
 [dependencies]
 cov-mark = { version = "1.1", features = ["thread-local"] }
 itertools = "0.10.0"
-arrayvec = "0.5.1"
+arrayvec = "0.6"
 smallvec = "1.2.0"
 ena = "0.14.0"
 log = "0.4.8"
diff --git a/crates/hir_ty/src/display.rs b/crates/hir_ty/src/display.rs
index 6149067c7..51480304b 100644
--- a/crates/hir_ty/src/display.rs
+++ b/crates/hir_ty/src/display.rs
@@ -1,8 +1,7 @@
 //! FIXME: write short doc here
 
-use std::fmt;
+use std::{array, fmt};
 
-use arrayvec::ArrayVec;
 use chalk_ir::Mutability;
 use hir_def::{
     db::DefDatabase,
@@ -669,8 +668,7 @@ fn fn_traits(db: &dyn DefDatabase, trait_: TraitId) -> impl Iterator<Item = Trai
         db.lang_item(krate, "fn_mut".into()),
         db.lang_item(krate, "fn_once".into()),
     ];
-    // FIXME: Replace ArrayVec when into_iter is a thing on arrays
-    ArrayVec::from(fn_traits).into_iter().flatten().flat_map(|it| it.as_trait())
+    array::IntoIter::new(fn_traits).into_iter().flatten().flat_map(|it| it.as_trait())
 }
 
 pub fn write_bounds_like_dyn_trait_with_prefix(
diff --git a/crates/hir_ty/src/infer.rs b/crates/hir_ty/src/infer.rs
index 8f9cf7480..e4407ff50 100644
--- a/crates/hir_ty/src/infer.rs
+++ b/crates/hir_ty/src/infer.rs
@@ -45,6 +45,11 @@ use crate::{
     to_assoc_type_id, to_chalk_trait_id, AliasEq, AliasTy, Interner, TyKind,
 };
 
+// This lint has a false positive here. See the link below for details.
+//
+// https://github.com/rust-lang/rust/issues/57411
+#[allow(unreachable_pub)]
+pub use unify::could_unify;
 pub(crate) use unify::unify;
 
 mod unify;
diff --git a/crates/hir_ty/src/infer/unify.rs b/crates/hir_ty/src/infer/unify.rs
index 75250a369..6e7b0f5a6 100644
--- a/crates/hir_ty/src/infer/unify.rs
+++ b/crates/hir_ty/src/infer/unify.rs
@@ -157,6 +157,10 @@ impl<T> Canonicalized<T> {
     }
 }
 
+pub fn could_unify(t1: &Ty, t2: &Ty) -> bool {
+    InferenceTable::new().unify(t1, t2)
+}
+
 pub(crate) fn unify(tys: &Canonical<(Ty, Ty)>) -> Option<Substitution> {
     let mut table = InferenceTable::new();
     let vars = Substitution(
diff --git a/crates/hir_ty/src/lib.rs b/crates/hir_ty/src/lib.rs
index 69265286f..6f9c698e6 100644
--- a/crates/hir_ty/src/lib.rs
+++ b/crates/hir_ty/src/lib.rs
@@ -41,7 +41,7 @@ use crate::{
 };
 
 pub use autoderef::autoderef;
-pub use infer::{InferenceResult, InferenceVar};
+pub use infer::{could_unify, InferenceResult, InferenceVar};
 pub use lower::{
     associated_type_shorthand_candidates, callable_item_sig, CallableDefId, ImplTraitLoweringMode,
     TyDefId, TyLoweringContext, ValueTyDefId,
diff --git a/crates/hir_ty/src/method_resolution.rs b/crates/hir_ty/src/method_resolution.rs
index 84d9a1e18..bf7d5eded 100644
--- a/crates/hir_ty/src/method_resolution.rs
+++ b/crates/hir_ty/src/method_resolution.rs
@@ -228,12 +228,12 @@ impl Ty {
         &self,
         db: &dyn HirDatabase,
         cur_crate: CrateId,
-    ) -> Option<ArrayVec<[CrateId; 2]>> {
+    ) -> Option<ArrayVec<CrateId, 2>> {
         // Types like slice can have inherent impls in several crates, (core and alloc).
         // The corresponding impls are marked with lang items, so we can use them to find the required crates.
         macro_rules! lang_item_crate {
             ($($name:expr),+ $(,)?) => {{
-                let mut v = ArrayVec::<[LangItemTarget; 2]>::new();
+                let mut v = ArrayVec::<LangItemTarget, 2>::new();
                 $(
                     v.extend(db.lang_item(cur_crate, $name.into()));
                 )+