Use FastaMessage instead of String. Part 1.

pkg/front_end/lib/src/fasta/builder/class_builder.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.class_builder;
 
 import '../deprecated_problems.dart' show deprecated_internalProblem;
 
 import 'builder.dart'
     show
         Builder,
         ConstructorReferenceBuilder,
         LibraryBuilder,
         MemberBuilder,
         MetadataBuilder,
         MixinApplicationBuilder,
         NamedTypeBuilder,
         Scope,
         ScopeBuilder,
         TypeBuilder,
         TypeDeclarationBuilder,
         TypeVariableBuilder;
 
+import '../fasta_codes.dart' show Message;
+
 abstract class ClassBuilder<T extends TypeBuilder, R>
     extends TypeDeclarationBuilder<T, R> {
   final List<TypeVariableBuilder> typeVariables;
 
   T supertype;
 
   List<T> interfaces;
 
   final Scope scope;
 
@@ skipping 157 matching lines @@
   }
 
   /// Don't use for scope lookup. Only use when an element is known to exist
   /// (and isn't a setter).
   MemberBuilder operator [](String name) {
     // TODO(ahe): Rename this to getLocalMember.
     return scope.local[name] ??
         deprecated_internalProblem("Not found: '$name'.");
   }
 
+  void addCompileTimeError(Message message, int charOffset) {
+    library.addCompileTimeError(message, charOffset, fileUri);
+  }
+
+  void addWarning(Message message, int charOffset) {
+    library.addWarning(message, charOffset, fileUri);
+  }
+
+  void addNit(Message message, int charOffset) {
+    library.addNit(message, charOffset, fileUri);
+  }
+
   void deprecated_addCompileTimeError(int charOffset, String message) {
     library.deprecated_addCompileTimeError(charOffset, message,
         fileUri: fileUri);
   }
 
   void deprecated_addWarning(int charOffset, String message) {
     library.deprecated_addWarning(charOffset, message, fileUri: fileUri);
   }
 
   void deprecated_addNit(int charOffset, String message) {
     library.deprecated_addNit(charOffset, message, fileUri: fileUri);
   }
 }