Add method to Mir that maps a Location to its SourceInfo.

src/librustc/mir/mod.rs

@@ -284,6 +284,19 @@ impl<'tcx> Mir<'tcx> {
         debug_assert!(location.statement_index < block.statements.len());
         block.statements[location.statement_index].make_nop()
     }
+
+    /// Returns the source info associated with `location`.
+    pub fn source_info(&self, location: Location) -> &SourceInfo {
+        let block = &self[location.block];
+        let stmts = &block.statements;
+        let idx = location.statement_index;
+        if location.statement_index < stmts.len() {
+            &stmts[idx].source_info
+        } else {
+            assert!(location.statement_index == stmts.len());
+            &block.terminator().source_info
+        }
+    }
 }
 
 #[derive(Clone, Debug)]

src/librustc_mir/borrow_check.rs

@@ -1126,9 +1126,7 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
 
     // Retrieve span of given borrow from the current MIR representation
     fn retrieve_borrow_span(&self, borrow: &BorrowData) -> Span {
-        self.mir.basic_blocks()[borrow.location.block]
-            .statements[borrow.location.statement_index]
-            .source_info.span
+        self.mir.source_info(borrow.location).span
     }
 }