Replaced String with &str in API for add_explanation_to_diagnostic.

Author: pnkfelix

src/librustc_mir/borrow_check/error_reporting.rs

@@ -262,7 +262,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
         move_spans.var_span_label(&mut err, "move occurs due to use in closure");
 
         self.explain_why_borrow_contains_point(context, borrow, None)
-            .add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, String::new());
+            .add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, "");
         err.buffer(&mut self.errors_buffer);
     }
 
@@ -299,7 +299,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
         });
 
         self.explain_why_borrow_contains_point(context, borrow, None)
-            .add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, String::new());
+            .add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, "");
         err.buffer(&mut self.errors_buffer);
     }
 
@@ -483,7 +483,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
         }
 
         self.explain_why_borrow_contains_point(context, issued_borrow, None)
-            .add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, first_borrow_desc.to_string());
+            .add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, first_borrow_desc);
 
         err.buffer(&mut self.errors_buffer);
     }
@@ -638,7 +638,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
 
             if let BorrowExplanation::MustBeValidFor(..) = explanation {
             } else {
-                explanation.add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, String::new());
+                explanation.add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, "");
             }
         } else {
             err.span_label(borrow_span, "borrowed value does not live long enough");
@@ -649,7 +649,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
 
             borrow_spans.args_span_label(&mut err, "value captured here");
 
-            explanation.add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, String::new());
+            explanation.add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, "");
         }
 
         err
@@ -709,7 +709,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
             _ => {}
         }
 
-        explanation.add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, String::new());
+        explanation.add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, "");
 
         err.buffer(&mut self.errors_buffer);
     }
@@ -776,7 +776,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
             }
             _ => {}
         }
-        explanation.add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, String::new());
+        explanation.add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, "");
 
         borrow_spans.args_span_label(&mut err, "value captured here");
 
@@ -913,7 +913,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
         loan_spans.var_span_label(&mut err, "borrow occurs due to use in closure");
 
         self.explain_why_borrow_contains_point(context, loan, None)
-            .add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, String::new());
+            .add_explanation_to_diagnostic(self.infcx.tcx, self.mir, &mut err, "");
 
         err.buffer(&mut self.errors_buffer);
     }

src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs

@@ -42,28 +42,28 @@ impl<'tcx> BorrowExplanation<'tcx> {
         tcx: TyCtxt<'cx, 'gcx, 'tcx>,
         _mir: &Mir<'tcx>,
         err: &mut DiagnosticBuilder<'_>,
-        borrow_desc: String,
+        borrow_desc: &str,
     ) {
         match *self {
             BorrowExplanation::UsedLater(later_use_kind, var_or_use_span) => {
-                let message = borrow_desc + match later_use_kind {
+                let message = match later_use_kind {
                     LaterUseKind::ClosureCapture => "borrow later captured here by closure",
                     LaterUseKind::Call =>  "borrow later used by call",
                     LaterUseKind::FakeLetRead => "borrow later stored here",
                     LaterUseKind::Other => "borrow later used here",
                 };
-                err.span_label(var_or_use_span, message);
+                err.span_label(var_or_use_span, format!("{}{}", borrow_desc, message));
             },
             BorrowExplanation::UsedLaterInLoop(later_use_kind, var_or_use_span) => {
-                let message = borrow_desc + match later_use_kind {
+                let message = match later_use_kind {
                     LaterUseKind::ClosureCapture => {
                         "borrow captured here by closure, in later iteration of loop"
                     },
                     LaterUseKind::Call =>  "borrow used by call, in later iteration of loop",
                     LaterUseKind::FakeLetRead => "borrow later stored here",
                     LaterUseKind::Other => "borrow used here, in later iteration of loop",
                 };
-                err.span_label(var_or_use_span, message);
+                err.span_label(var_or_use_span, format!("{}{}", borrow_desc, message));
             },
             BorrowExplanation::UsedLaterWhenDropped(span, local_name, should_note_order) => {
                 err.span_label(
@@ -85,7 +85,7 @@ impl<'tcx> BorrowExplanation<'tcx> {
             BorrowExplanation::MustBeValidFor(region) => {
                 tcx.note_and_explain_free_region(
                     err,
-                    &(borrow_desc + "borrowed value must be valid for "),
+                    &format!("{}{}", borrow_desc, "borrowed value must be valid for "),
                     region,
                     "...",
                 );