Add AstBuilder support for enum declarations.

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 103 matching lines @@
   void handleIdentifier(Token token, IdentifierContext context) {
     debugEvent("handleIdentifier");
     String name = token.value;
     SimpleIdentifier identifier = ast.simpleIdentifier(toAnalyzerToken(token));
     if (context.inLibraryOrPartOfDeclaration) {
       if (!context.isContinuation) {
         push([identifier]);
       } else {
         push(identifier);
       }
+    } else if (context == IdentifierContext.enumValueDeclaration) {
+      // TODO(paulberry): analyzer's ASTs allow for enumerated values to have
+      // metadata, but the spec doesn't permit it.

[ahe, 2017/02/23 16:47:25]

I think we should accept it for error recovery.

+      List<Annotation> metadata;
+      // TODO(paulberry): capture doc comments.  See dartbug.com/28851.
+      Comment comment = null;
+      push(ast.enumConstantDeclaration(comment, metadata, identifier));
     } else {
       if (context.isScopeReference) {
         Builder builder = scope.lookup(name, token.charOffset, uri);
         if (builder != null) {
           Element element = elementStore[builder];
           assert(element != null);
           identifier.staticElement = element;
         }
       }
       push(identifier);
@@ skipping 937 matching lines @@
         comment,
         metadata,
         toAnalyzerToken(typedefKeyword),
         returnType,
         name,
         typeParameters,
         parameters,
         toAnalyzerToken(endToken)));
   }
 
+  void endEnum(Token enumKeyword, Token endBrace, int count) {
+    debugEvent("Enum");
+    List<EnumConstantDeclaration> constants = popList(count);
+    // TODO(paulberry,ahe): the parser should pass in the openBrace token.
+    var openBrace = enumKeyword.next.next as BeginGroupToken;

[ahe, 2017/02/23 16:47:25]

I would recommend against casts as they have to be checked at runtime. Instead,
this works well:

BeginGroupToken openBrace = enumKeyword.next.next;

+    // TODO(paulberry): what if the '}' is missing and the parser has performed
+    // error recovery?

[ahe, 2017/02/23 16:47:25]

The scanner always provides a synthetic end token. The problem is actually on
the previous statement, if a { was missing. I don't think the parser can recover
from that today, though.

+    Token closeBrace = openBrace.endGroup;
+    SimpleIdentifier name = pop();
+    List<Annotation> metadata = pop();
+    // TODO(paulberry): capture doc comments.  See dartbug.com/28851.
+    Comment comment = null;
+    push(ast.enumDeclaration(
+        comment,
+        metadata,
+        toAnalyzerToken(enumKeyword),
+        name,
+        toAnalyzerToken(openBrace),
+        constants,
+        toAnalyzerToken(closeBrace)));
+  }
+
   /**
    * Pop the modifiers list, if the list is empty return `null`, if the list
    * has one item return it; otherwise return `null`.
    */
   Token _popOptionalSingleModifier() {
     List<Token> modifiers = pop();
     if (modifiers.length == 0) {
       return null;
     } else if (modifiers.length == 1) {
       // TODO(scheglov): Verify that the modifier is valid.
@@ skipping 29 matching lines @@
 /// [ClassDeclaration] or [ClassTypeAlias] object.
 class _MixinApplication {
   final TypeName supertype;
 
   final Token withKeyword;
 
   final List<TypeName> mixinTypes;
 
   _MixinApplication(this.supertype, this.withKeyword, this.mixinTypes);
 }