Use printUnexpected and add location information.

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

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library fasta.source_loader;
 
 import 'dart:async' show
     Future;
 
 import 'dart:io' show
@@ skipping 14 matching lines @@
 import 'package:kernel/ast.dart' show
     Program;
 
 import 'package:kernel/class_hierarchy.dart' show
     ClassHierarchy;
 
 import 'package:kernel/core_types.dart' show
     CoreTypes;
 
 import '../errors.dart' show
-    InputError,
-    inputError;
+    inputError,
+    printUnexpected;
 
 import '../messages.dart' show
     warning;
 
 import '../export.dart' show
     Export;
 
 import '../analyzer/element_store.dart' show
     ElementStore;
 
@@ skipping 44 matching lines @@
       List<int> bytes = await readBytesFromFile(uri);
       byteCount += bytes.length - 1;
       ScannerResult result = scan(bytes);
       Token token = result.tokens;
       if (!suppressLexicalErrors) {
         target.addLineStarts(library.fileUri, result.lineStarts);
       }
       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;
       }
       return token;
     } on FileSystemException catch (e) {
       String message = e.message;
       String osMessage = e.osError?.message;
       if (osMessage != null && osMessage.isNotEmpty) {
         message = osMessage;
       }
@@ skipping 251 matching lines @@
     ticker.logMs("Built analyzer element model.");
   }
 
   void computeHierarchy(Program program) {
     hierarchy = new ClassHierarchy(program);
     ticker.logMs("Computed class hierarchy");
     coreTypes = new CoreTypes(program);
     ticker.logMs("Computed core types");
   }
 }