borrowck diagnostics: address review comments.

Author: Centril

src/librustc_mir/borrow_check/diagnostics/conflict_errors.rs

@@ -256,8 +256,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             "report_move_out_while_borrowed: location={:?} place={:?} span={:?} borrow={:?}",
             location, place, span, borrow
         );
-        let value_msg = self.describe_place_str(place.as_ref());
-        let borrow_msg = self.describe_place_str(borrow.borrowed_place.as_ref());
+        let value_msg = self.describe_any_place(place.as_ref());
+        let borrow_msg = self.describe_any_place(borrow.borrowed_place.as_ref());
 
         let borrow_spans = self.retrieve_borrow_spans(borrow);
         let borrow_span = borrow_spans.args_or_use();
@@ -266,7 +266,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let span = move_spans.args_or_use();
 
         let mut err =
-            self.cannot_move_when_borrowed(span, &self.describe_place_str(place.as_ref()));
+            self.cannot_move_when_borrowed(span, &self.describe_any_place(place.as_ref()));
         err.span_label(borrow_span, format!("borrow of {} occurs here", borrow_msg));
         err.span_label(span, format!("move out of {} occurs here", value_msg));
 
@@ -306,14 +306,14 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
         let mut err = self.cannot_use_when_mutably_borrowed(
             span,
-            &self.describe_place_str(place.as_ref()),
+            &self.describe_any_place(place.as_ref()),
             borrow_span,
-            &self.describe_place_str(borrow.borrowed_place.as_ref()),
+            &self.describe_any_place(borrow.borrowed_place.as_ref()),
         );
 
         borrow_spans.var_span_label(&mut err, {
             let place = &borrow.borrowed_place;
-            let desc_place = self.describe_place_str(place.as_ref());
+            let desc_place = self.describe_any_place(place.as_ref());
             format!("borrow occurs due to use of {}{}", desc_place, borrow_spans.describe())
         });
 
@@ -506,7 +506,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             );
         } else {
             let borrow_place = &issued_borrow.borrowed_place;
-            let borrow_place_desc = self.describe_place_str(borrow_place.as_ref());
+            let borrow_place_desc = self.describe_any_place(borrow_place.as_ref());
             issued_spans.var_span_label(
                 &mut err,
                 format!(
@@ -647,12 +647,12 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                 && proj_base == target_base.projection
                             {
                                 return Some((
-                                    self.describe_place_str(PlaceRef {
+                                    self.describe_any_place(PlaceRef {
                                         local,
                                         projection: proj_base,
                                     }),
-                                    self.describe_place_str(first_borrowed_place.as_ref()),
-                                    self.describe_place_str(second_borrowed_place.as_ref()),
+                                    self.describe_any_place(first_borrowed_place.as_ref()),
+                                    self.describe_any_place(second_borrowed_place.as_ref()),
                                     union_ty.to_string(),
                                 ));
                             }
@@ -665,7 +665,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 // If we didn't find a field access into a union, or both places match, then
                 // only return the description of the first place.
                 (
-                    self.describe_place_str(first_borrowed_place.as_ref()),
+                    self.describe_any_place(first_borrowed_place.as_ref()),
                     "".to_string(),
                     "".to_string(),
                     "".to_string(),
@@ -1388,7 +1388,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let loan_spans = self.retrieve_borrow_spans(loan);
         let loan_span = loan_spans.args_or_use();
 
-        let descr_place = self.describe_place_str(place.as_ref());
+        let descr_place = self.describe_any_place(place.as_ref());
         if loan.kind == BorrowKind::Shallow {
             if let Some(section) = self.classify_immutable_section(&loan.assigned_place) {
                 let mut err = self.cannot_mutate_in_immutable_section(
@@ -1463,8 +1463,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             })
             | Some(LocalDecl { local_info: LocalInfo::StaticRef { .. }, .. })
             | Some(LocalDecl { local_info: LocalInfo::Other, .. })
-            | None => (self.describe_place_str(place.as_ref()), assigned_span),
-            Some(decl) => (self.describe_place_str(err_place.as_ref()), decl.source_info.span),
+            | None => (self.describe_any_place(place.as_ref()), assigned_span),
+            Some(decl) => (self.describe_any_place(err_place.as_ref()), decl.source_info.span),
         };
 
         let mut err = self.cannot_reassign_immutable(span, &place_description, from_arg);

src/librustc_mir/borrow_check/diagnostics/mod.rs

@@ -138,10 +138,16 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     }
 
     /// End-user visible description of `place` if one can be found.
-    /// If the place is a temporary for instance, `value` will be returned.
-    pub(super) fn describe_place_str(&self, place_ref: PlaceRef<'tcx>) -> String {
+    /// If the place is a temporary for instance, `"value"` will be returned.
+    pub(super) fn describe_any_place(&self, place_ref: PlaceRef<'tcx>) -> String {
         match self.describe_place(place_ref) {
-            Some(descr) => format!("`{}`", descr),
+            Some(mut descr) => {
+                // Surround descr with `backticks`.
+                descr.reserve(2);
+                descr.insert_str(0, "`");
+                descr.push_str("`");
+                descr
+            }
             None => "value".to_string(),
         }
     }

src/librustc_mir/borrow_check/diagnostics/move_errors.rs

@@ -272,14 +272,14 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         span: Span,
     ) -> DiagnosticBuilder<'a> {
         let description = if place.projection.len() == 1 {
-            format!("static item {}", self.describe_place_str(place.as_ref()))
+            format!("static item {}", self.describe_any_place(place.as_ref()))
         } else {
             let base_static = PlaceRef { local: place.local, projection: &[ProjectionElem::Deref] };
 
             format!(
                 "{} as {} is a static item",
-                self.describe_place_str(place.as_ref()),
-                self.describe_place_str(base_static),
+                self.describe_any_place(place.as_ref()),
+                self.describe_any_place(base_static),
             )
         };
 
@@ -349,7 +349,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 let upvar_name = upvar.name;
                 let upvar_span = self.infcx.tcx.hir().span(upvar_hir_id);
 
-                let place_name = self.describe_place_str(move_place.as_ref());
+                let place_name = self.describe_any_place(move_place.as_ref());
 
                 let place_description =
                     if self.is_upvar_field_projection(move_place.as_ref()).is_some() {

src/librustc_mir/borrow_check/diagnostics/mutability_errors.rs

@@ -170,7 +170,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     &mut err,
                     format!(
                         "mutable borrow occurs due to use of {} in closure",
-                        self.describe_place_str(access_place.as_ref()),
+                        self.describe_any_place(access_place.as_ref()),
                     ),
                 );
                 borrow_span

src/librustc_mir/util/borrowck_errors.rs

@@ -53,7 +53,7 @@ impl<'cx, 'tcx> crate::borrow_check::MirBorrowckCtxt<'cx, 'tcx> {
         old_load_end_span: Option<Span>,
     ) -> DiagnosticBuilder<'cx> {
         let via =
-            |msg: &str| if msg.is_empty() { msg.to_string() } else { format!(" (via {})", msg) };
+            |msg: &str| if msg.is_empty() { "".to_string() } else { format!(" (via {})", msg) };
         let mut err = struct_span_err!(
             self,
             new_loan_span,
@@ -201,13 +201,12 @@ impl<'cx, 'tcx> crate::borrow_check::MirBorrowckCtxt<'cx, 'tcx> {
         old_load_end_span: Option<Span>,
     ) -> DiagnosticBuilder<'cx> {
         let via =
-            |msg: &str| if msg.is_empty() { msg.to_string() } else { format!(" (via {})", msg) };
+            |msg: &str| if msg.is_empty() { "".to_string() } else { format!(" (via {})", msg) };
         let mut err = struct_span_err!(
             self,
             span,
             E0502,
-            "cannot borrow {}{} as {} because {} is also borrowed \
-             as {}{}",
+            "cannot borrow {}{} as {} because {} is also borrowed as {}{}",
             desc_new,
             via(msg_new),
             kind_new,