4 files changed, 31 insertions, 21 deletions

diff --git a/crates/hir_ty/src/infer/coerce.rs b/crates/hir_ty/src/infer/coerce.rs
index 03b97e7db..4b7f31521 100644
--- a/crates/hir_ty/src/infer/coerce.rs
+++ b/crates/hir_ty/src/infer/coerce.rs
@@ -2,8 +2,8 @@
 //! happen in certain places, e.g. weakening `&mut` to `&` or deref coercions
 //! like going from `&Vec<T>` to `&[T]`.
 //!
-//! See https://doc.rust-lang.org/nomicon/coercions.html and
-//! librustc_typeck/check/coercion.rs.
+//! See <https://doc.rust-lang.org/nomicon/coercions.html> and
+//! `librustc_typeck/check/coercion.rs`.
 
 use chalk_ir::{cast::Cast, Mutability, TyVariableKind};
 use hir_def::{expr::ExprId, lang_item::LangItemTarget};
@@ -109,7 +109,7 @@ impl<'a> InferenceContext<'a> {
         }
 
         // Consider coercing the subtype to a DST
-        if let Ok(ret) = self.try_coerce_unsized(&from_ty, &to_ty) {
+        if let Ok(ret) = self.try_coerce_unsized(&from_ty, to_ty) {
             return Ok(ret);
         }
 
@@ -331,7 +331,7 @@ impl<'a> InferenceContext<'a> {
 
     /// Coerce a type using `from_ty: CoerceUnsized<ty_ty>`
     ///
-    /// See: https://doc.rust-lang.org/nightly/std/marker/trait.CoerceUnsized.html
+    /// See: <https://doc.rust-lang.org/nightly/std/marker/trait.CoerceUnsized.html>
     fn try_coerce_unsized(&mut self, from_ty: &Ty, to_ty: &Ty) -> InferResult {
         // These 'if' statements require some explanation.
         // The `CoerceUnsized` trait is special - it is only
diff --git a/crates/hir_ty/src/infer/expr.rs b/crates/hir_ty/src/infer/expr.rs
index f73bf43b2..5ea2e5934 100644
--- a/crates/hir_ty/src/infer/expr.rs
+++ b/crates/hir_ty/src/infer/expr.rs
@@ -54,7 +54,7 @@ impl<'a> InferenceContext<'a> {
     /// Infer type of expression with possibly implicit coerce to the expected type.
     /// Return the type after possible coercion.
     pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
-        let ty = self.infer_expr_inner(expr, &expected);
+        let ty = self.infer_expr_inner(expr, expected);
         let ty = if let Some(target) = expected.only_has_type(&mut self.table) {
             if !self.coerce(&ty, &target) {
                 self.result
@@ -135,11 +135,11 @@ impl<'a> InferenceContext<'a> {
                 let mut both_arms_diverge = Diverges::Always;
 
                 let mut result_ty = self.table.new_type_var();
-                let then_ty = self.infer_expr_inner(*then_branch, &expected);
+                let then_ty = self.infer_expr_inner(*then_branch, expected);
                 both_arms_diverge &= mem::replace(&mut self.diverges, Diverges::Maybe);
                 result_ty = self.coerce_merge_branch(Some(*then_branch), &result_ty, &then_ty);
                 let else_ty = match else_branch {
-                    Some(else_branch) => self.infer_expr_inner(*else_branch, &expected),
+                    Some(else_branch) => self.infer_expr_inner(*else_branch, expected),
                     None => TyBuilder::unit(),
                 };
                 both_arms_diverge &= self.diverges;
@@ -327,20 +327,19 @@ impl<'a> InferenceContext<'a> {
                 self.normalize_associated_types_in(ret_ty)
             }
             Expr::MethodCall { receiver, args, method_name, generic_args } => self
-                .infer_method_call(
-                    tgt_expr,
-                    *receiver,
-                    &args,
-                    &method_name,
-                    generic_args.as_deref(),
-                ),
+                .infer_method_call(tgt_expr, *receiver, args, method_name, generic_args.as_deref()),
             Expr::Match { expr, arms } => {
                 let input_ty = self.infer_expr(*expr, &Expectation::none());
 
+                let expected = expected.adjust_for_branches(&mut self.table);
+
                 let mut result_ty = if arms.is_empty() {
                     TyKind::Never.intern(&Interner)
                 } else {
-                    self.table.new_type_var()
+                    match &expected {
+                        Expectation::HasType(ty) => ty.clone(),
+                        _ => self.table.new_type_var(),
+                    }
                 };
 
                 let matchee_diverges = self.diverges;
@@ -988,7 +987,7 @@ impl<'a> InferenceContext<'a> {
     }
 
     fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
-        let callable_ty = self.resolve_ty_shallow(&callable_ty);
+        let callable_ty = self.resolve_ty_shallow(callable_ty);
         if let TyKind::FnDef(fn_def, parameters) = callable_ty.kind(&Interner) {
             let def: CallableDefId = from_chalk(self.db, *fn_def);
             let generic_predicates = self.db.generic_predicates(def.into());
diff --git a/crates/hir_ty/src/infer/pat.rs b/crates/hir_ty/src/infer/pat.rs
index 83e0a7a9e..035f4ded6 100644
--- a/crates/hir_ty/src/infer/pat.rs
+++ b/crates/hir_ty/src/infer/pat.rs
@@ -101,7 +101,9 @@ impl<'a> InferenceContext<'a> {
         let mut expected = self.resolve_ty_shallow(expected);
 
         if is_non_ref_pat(&body, pat) {
+            let mut pat_adjustments = Vec::new();
             while let Some((inner, _lifetime, mutability)) = expected.as_reference() {
+                pat_adjustments.push(expected.clone());
                 expected = self.resolve_ty_shallow(inner);
                 default_bm = match default_bm {
                     BindingMode::Move => BindingMode::Ref(mutability),
@@ -109,6 +111,11 @@ impl<'a> InferenceContext<'a> {
                     BindingMode::Ref(Mutability::Mut) => BindingMode::Ref(mutability),
                 }
             }
+
+            if !pat_adjustments.is_empty() {
+                pat_adjustments.shrink_to_fit();
+                self.result.pat_adjustments.insert(pat, pat_adjustments);
+            }
         } else if let Pat::Ref { .. } = &body[pat] {
             cov_mark::hit!(match_ergonomics_ref);
             // When you encounter a `&pat` pattern, reset to Move.
@@ -185,7 +192,7 @@ impl<'a> InferenceContext<'a> {
             Pat::Path(path) => {
                 // FIXME use correct resolver for the surrounding expression
                 let resolver = self.resolver.clone();
-                self.infer_path(&resolver, &path, pat.into()).unwrap_or(self.err_ty())
+                self.infer_path(&resolver, path, pat.into()).unwrap_or(self.err_ty())
             }
             Pat::Bind { mode, name: _, subpat } => {
                 let mode = if mode == &BindingAnnotation::Unannotated {
@@ -268,7 +275,7 @@ impl<'a> InferenceContext<'a> {
         if !self.unify(&ty, &expected) {
             self.result
                 .type_mismatches
-                .insert(pat.into(), TypeMismatch { expected: expected, actual: ty.clone() });
+                .insert(pat.into(), TypeMismatch { expected, actual: ty.clone() });
         }
         self.write_pat_ty(pat, ty.clone());
         ty
@@ -290,6 +297,10 @@ fn is_non_ref_pat(body: &hir_def::body::Body, pat: PatId) -> bool {
             Expr::Literal(Literal::String(..)) => false,
             _ => true,
         },
+        Pat::Bind { mode: BindingAnnotation::Mutable, subpat: Some(subpat), .. }
+        | Pat::Bind { mode: BindingAnnotation::Unannotated, subpat: Some(subpat), .. } => {
+            is_non_ref_pat(body, *subpat)
+        }
         Pat::Wild | Pat::Bind { .. } | Pat::Ref { .. } | Pat::Box { .. } | Pat::Missing => false,
     }
 }
diff --git a/crates/hir_ty/src/infer/path.rs b/crates/hir_ty/src/infer/path.rs
index 14c99eafd..056cdb5d5 100644
--- a/crates/hir_ty/src/infer/path.rs
+++ b/crates/hir_ty/src/infer/path.rs
@@ -43,11 +43,11 @@ impl<'a> InferenceContext<'a> {
             }
             let ty = self.make_ty(type_ref);
             let remaining_segments_for_ty = path.segments().take(path.segments().len() - 1);
-            let ctx = crate::lower::TyLoweringContext::new(self.db, &resolver);
+            let ctx = crate::lower::TyLoweringContext::new(self.db, resolver);
             let (ty, _) = ctx.lower_ty_relative_path(ty, None, remaining_segments_for_ty);
             self.resolve_ty_assoc_item(
                 ty,
-                &path.segments().last().expect("path had at least one segment").name,
+                path.segments().last().expect("path had at least one segment").name,
                 id,
             )?
         } else {
@@ -154,7 +154,7 @@ impl<'a> InferenceContext<'a> {
                 let segment =
                     remaining_segments.last().expect("there should be at least one segment here");
 
-                self.resolve_ty_assoc_item(ty, &segment.name, id)
+                self.resolve_ty_assoc_item(ty, segment.name, id)
             }
         }
     }