Report messages instead of just printing.

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:typed_data' show Uint8List;
 
@@ skipping 14 matching lines @@
     show
         Builder,
         ClassBuilder,
         EnumBuilder,
         LibraryBuilder,
         NamedTypeBuilder,
         TypeBuilder;
 
 import '../compiler_context.dart' show CompilerContext;
 
-import '../deprecated_problems.dart'
-    show deprecated_formatUnexpected, deprecated_inputError;
+import '../deprecated_problems.dart' show deprecated_inputError;
 
 import '../export.dart' show Export;
 
 import '../fasta_codes.dart'
     show
         Message,
         templateCyclicClassHierarchy,
         templateExtendingEnum,
         templateExtendingRestricted,
         templateIllegalMixin,
         templateIllegalMixinDueToConstructors,
         templateIllegalMixinDueToConstructorsCause,
         templateUnspecified;
 
 import '../kernel/kernel_shadow_ast.dart' show KernelTypeInferenceEngine;
 
 import '../kernel/kernel_target.dart' show KernelTarget;
 
 import '../loader.dart' show Loader;
 
 import '../parser/class_member_parser.dart' show ClassMemberParser;
 
 import '../scanner.dart' show ErrorToken, ScannerResult, Token, scan;
 
+import '../severity.dart' show Severity;
+
 import '../type_inference/type_inference_engine.dart' show TypeInferenceEngine;
 
 import 'diet_listener.dart' show DietListener;
 
 import 'diet_parser.dart' show DietParser;
 
 import 'outline_builder.dart' show OutlineBuilder;
 
 import 'source_class_builder.dart' show SourceClassBuilder;
 
@@ skipping 452 matching lines @@
         isStatic: isStatic,
         isConstructor: isConstructor,
         isTopLevel: isTopLevel);
   }
 
   Expression throwCompileConstantError(Expression error) {
     return target.backendTarget.throwCompileConstantError(coreTypes, error);
   }
 
   Expression buildCompileTimeError(Message message, int offset, Uri uri) {
-    String text = deprecated_formatUnexpected(uri, offset, message.message);
+    String text = target.context
+        .format(message.withLocation(uri, offset), Severity.error);
     return target.backendTarget.buildCompileTimeError(coreTypes, text, offset);
   }
 }