Report messages instead of just printing.

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 964d1ece04ca9f0e5dae7ab35745581d4798260f..7f430a77ca97f412582d05c13f66438de2a0192d 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 +32,7 @@ import '../builder/builder.dart'
 
 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;
 
@@ -58,6 +57,8 @@ 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;
@@ -530,7 +531,8 @@ class SourceLoader<L> extends Loader<L> {
   }
 
   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);
   }
 }