Add support for parsing annotations with Fasta.

pkg/front_end/lib/src/fasta/analyzer/ast_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.analyzer.ast_builder;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/ast_factory.dart' show AstFactory;
 import 'package:analyzer/dart/ast/standard_ast_factory.dart' as standard;
 import 'package:analyzer/dart/ast/token.dart' as analyzer show Token;
@@ skipping 1452 matching lines @@
   @override
   void beginMetadataStar(Token token) {
     debugEvent("beginMetadataStar");
     if (token.precedingComments != null) {
       push(_toAnalyzerComment(token.precedingComments));
     } else {
       push(NullValue.Comments);
     }
   }
 
+  @override
+  void endMetadata(Token beginToken, Token periodBeforeName, Token endToken) {
+    debugEvent("Metadata");
+    MethodInvocation invocation = pop();
+    SimpleIdentifier constructorName = periodBeforeName != null ? pop() : null;
+    pop(); // Type arguments, not allowed.
+    Identifier name = pop();
+    push(ast.annotation(
+        toAnalyzerToken(beginToken),
+        name,
+        toAnalyzerToken(periodBeforeName),
+        constructorName,
+        invocation?.argumentList));
+  }
+
   ParameterKind _toAnalyzerParameterKind(FormalParameterType type) {
     if (type == FormalParameterType.POSITIONAL) {
       return ParameterKind.POSITIONAL;
     } else if (type == FormalParameterType.NAMED) {
       return ParameterKind.NAMED;
     } else {
       return ParameterKind.REQUIRED;
     }
   }
 
@@ skipping 106 matching lines @@
       } else if (identical('static', s)) {
         staticKeyword = token;
       } else if (identical('var', s)) {
         finalConstOrVarKeyword = token;
       } else {
         internalError('Unhandled modifier: $s');
       }
     }
   }
 }