Add AstBuilder support for fields.

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 1293 matching lines @@
 
   @override
   void endTypeArguments(int count, Token beginToken, Token endToken) {
     debugEvent("TypeArguments");
     List<TypeAnnotation> arguments = popList(count);
     push(ast.typeArgumentList(
         toAnalyzerToken(beginToken), arguments, toAnalyzerToken(endToken)));
   }
 
   @override
+  void endFields(
+      int count, Token covariantKeyword, Token beginToken, Token endToken) {
+    debugEvent("Fields");
+    List<VariableDeclaration> variables = popList(count);
+    TypeAnnotation type = pop();
+    List<Token> modifiers = pop();
+    Token staticKeyword;
+    Token keyword;
+    for (Token modifier in modifiers) {

[ahe, 2017/03/01 15:20:31]

Would it make sense to have something more like
pkg/front_end/lib/src/fasta/modifier.dart?

[Paul Berry, 2017/03/01 21:08:22]

Unfortunately that wouldn't be quite enough; the analyzer AST needs to point to
the modifier tokens themselves.

However, I like the idea of encapsulating some of this logic in a class.  I'll
look into it.

+      String value = modifier.stringValue;
+      if (identical('static', value)) {
+        // TODO(paulberry): Check the order and uniqueness.

[ahe, 2017/03/01 15:20:31]

I think we should have the parser do that (while still recovering from wrong
order).

[Paul Berry, 2017/03/01 21:08:22]

Agreed.  There are several TODOs that say this, so I will submit a follow-up CL
to fix all of them.

+        staticKeyword = modifier;
+      } else if (identical('var', value)) {
+        // TODO(paulberry): Check the order and uniqueness.
+        keyword = modifier;
+      } else {
+        // TODO(paulberry): Report error.
+        internalError("Invalid modifier ($value). Report an error.");
+      }
+    }
+    var variableList = ast.variableDeclarationList(
+        null, null, toAnalyzerToken(keyword), type, variables);
+    List<Annotation> metadata = pop();
+    // TODO(paulberry): capture doc comments.  See dartbug.com/28851.
+    Comment comment = null;
+    push(ast.fieldDeclaration2(
+        comment: comment,
+        metadata: metadata,
+        covariantKeyword: toAnalyzerToken(covariantKeyword),
+        staticKeyword: toAnalyzerToken(staticKeyword),
+        fieldList: variableList,
+        semicolon: toAnalyzerToken(endToken)));
+  }
+
+  @override
   void handleOperatorName(Token operatorKeyword, Token token) {
     debugEvent("OperatorName");
     push(new _OperatorName(operatorKeyword,
         ast.simpleIdentifier(toAnalyzerToken(token), isDeclaration: true)));
   }
 
   /**
    * Pop the modifiers list, if the list is empty return `null`, if the list
    * has one item return it; otherwise return `null`.
    */
@@ skipping 73 matching lines @@
 }
 
 /// Data structure placed on the stack to represent the keyword "operator"
 /// followed by a token.
 class _OperatorName {
   final Token operatorKeyword;
   final SimpleIdentifier name;
 
   _OperatorName(this.operatorKeyword, this.name);
 }