Report messages instead of just printing.

pkg/front_end/lib/src/fasta/compiler_context.dart

 // Copyright (c) 2017, 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.compiler_context;
 
 import 'dart:async' show Zone, runZoned;
 
 import 'package:front_end/file_system.dart';
 import 'package:front_end/physical_file_system.dart';
 import 'package:kernel/ast.dart' show Source;
 
 import 'compiler_command_line.dart' show CompilerCommandLine;
 
 import 'colors.dart' show computeEnableColors;
 
+import 'fasta_codes.dart' show LocatedMessage, Message;
+
+import 'severity.dart' show Severity;
+
 final Object compilerContextKey = new Object();
 
 final CompilerContext rootContext =
     new CompilerContext(CompilerCommandLine.forRootContext());
 
 class CompilerContext {
   final FileSystem fileSystem = PhysicalFileSystem.instance;
+
   final CompilerCommandLine options;
 
   final Map<String, Source> uriToSource = <String, Source>{};
 
   bool enableColorsCached = null;
 
   CompilerContext(this.options);
 
   void disableColors() {
     enableColorsCached = false;
   }
 
+  /// Report [message], for example, by printing it.
+  void report(LocatedMessage message, Severity severity) {
+    options.report(message, severity);
+  }
+
+  /// Report [message], for example, by printing it.
+  void reportWithoutLocation(Message message, Severity severity) {
+    options.reportWithoutLocation(message, severity);
+  }
+
+  /// Format [message] as a text string that can be included in generated code.
+  String format(LocatedMessage message, Severity severity) {
+    return options.format(message, severity);
+  }
+
+  /// Format [message] as a text string that can be included in generated code.
+  String formatWithoutLocation(Message message, Severity severity) {
+    return options.formatWithoutLocation(message, severity);
+  }
+
   static CompilerContext get current {
     return Zone.current[compilerContextKey] ?? rootContext;
   }
 
   /// Perform [action] in a [Zone] where [cl] will be available as
   /// `CompilerContext.current.options`.
   static dynamic withGlobalOptions(
       CompilerCommandLine cl, dynamic action(CompilerContext c)) {
     CompilerContext c = new CompilerContext(cl);
     return runZoned(() => action(c), zoneValues: {compilerContextKey: c});
   }
 
   static bool get enableColors {
     return current.enableColorsCached ??= computeEnableColors(current);
   }
 }