Apply code review suggestions

Author: eholk

compiler/rustc_hir_typeck/src/coercion.rs

@@ -216,7 +216,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
             }
             ty::Adt(pin, _)
                 if self.tcx.features().pin_ergonomics
-                    && pin.did() == self.tcx.lang_items().pin_type().unwrap() =>
+                    && self.tcx.is_lang_item(pin.did(), hir::LangItem::Pin) =>
             {
                 return self.coerce_pin(a, b);
             }
@@ -796,29 +796,29 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
         // Then we will build a ReborrowPin adjustment and return that as an InferOk.
 
         // Right now we can only reborrow if this is a `Pin<&mut T>`.
-        let can_reborrow = |ty: Ty<'tcx>| {
+        let extract_pin_mut = |ty: Ty<'tcx>| {
             // Get the T out of Pin<T>
             let ty = match ty.kind() {
-                ty::Adt(pin, args) if pin.did() == self.tcx.lang_items().pin_type().unwrap() => {
+                ty::Adt(pin, args) if self.tcx.is_lang_item(pin.did(), hir::LangItem::Pin) => {
                     args[0].expect_ty()
                 }
                 _ => {
                     debug!("can't reborrow {:?} as pinned", ty);
-                    return None;
+                    return Err(TypeError::Mismatch);
                 }
             };
             // Make sure the T is something we understand (just `&mut U` for now)
             match ty.kind() {
-                ty::Ref(region, ty, ty::Mutability::Mut) => Some((*region, *ty)),
+                ty::Ref(region, ty, ty::Mutability::Mut) => Ok((*region, *ty)),
                 _ => {
                     debug!("can't reborrow pin of inner type {:?}", ty);
-                    None
+                    Err(TypeError::Mismatch)
                 }
             }
         };
 
-        let (_, _a_ty) = can_reborrow(a).ok_or(TypeError::Mismatch)?;
-        let (b_region, _b_ty) = can_reborrow(b).ok_or(TypeError::Mismatch)?;
+        let (_, _a_ty) = extract_pin_mut(a)?;
+        let (b_region, _b_ty) = extract_pin_mut(b)?;
 
         // To complete the reborrow, we need to make sure we can unify the inner types, and if so we
         // add the adjustments.

compiler/rustc_hir_typeck/src/expr_use_visitor.rs

@@ -791,8 +791,6 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
                         adjustment::AutoBorrow::RawPtr(m) => ty::BorrowKind::from_mutbl(*m),
                     };
                     self.delegate.borrow_mut().borrow(&place_with_id, place_with_id.hir_id, bk);
-
-                    self.walk_autoref(expr, &place_with_id, autoref);
                 }
             }
             place_with_id = self.cat_expr_adjusted(expr, place_with_id, adjustment)?;

compiler/rustc_middle/src/ty/adjustment.rs

@@ -105,7 +105,8 @@ pub enum Adjust<'tcx> {
     /// Cast into a dyn* object.
     DynStar,
 
-    /// Take a Pin<Ptr> and call either as_mut() or as_ref() to get a Pin<&mut T> or Pin<&T>.
+    /// Take a `Pin<Ptr>` and call either `as_mut()` or `as_ref()` to get a `Pin<&mut T>` or
+    /// `Pin<&T>`.
     ReborrowPin(AutoBorrow<'tcx>),
 }