Use printUnexpected and add location information.

pkg/front_end/lib/src/fasta/source/source_loader.dart

Index: pkg/front_end/lib/src/fasta/source/source_loader.dart
diff --git a/pkg/front_end/lib/src/fasta/source/source_loader.dart b/pkg/front_end/lib/src/fasta/source/source_loader.dart
index d1d3da25def111eb2bd7b0cdbbeafc0e34921d35..42550ce6fa78286c87a839665e6e1b3e9ee316d6 100644
--- a/pkg/front_end/lib/src/fasta/source/source_loader.dart
+++ b/pkg/front_end/lib/src/fasta/source/source_loader.dart
@@ -32,8 +32,8 @@ import 'package:kernel/core_types.dart' show
     CoreTypes;
 
 import '../errors.dart' show
-    InputError,
-    inputError;
+    inputError,
+    printUnexpected;
 
 import '../messages.dart' show
     warning;
@@ -98,8 +98,7 @@ class SourceLoader<L> extends Loader<L> {
       while (token is ErrorToken) {
         if (!suppressLexicalErrors) {
           ErrorToken error = token;
-          print(new InputError(uri, token.charOffset, error.assertionMessage)
-              .format());
+          printUnexpected(uri, token.charOffset, error.assertionMessage);
         }
         token = token.next;
       }