Support for the 'covariant' keyword for formal parameters.

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 482 matching lines @@
     debugEvent("ValuedFormalParameter");
     Expression value = pop();
     push(new _ParameterDefaultValue(equals, value));
   }
 
   void handleFormalParameterWithoutValue(Token token) {
     debugEvent("FormalParameterWithoutValue");
     push(NullValue.ParameterDefaultValue);
   }
 
-  void endFormalParameter(Token thisKeyword, FormalParameterType kind) {
+  void endFormalParameter(
+      Token covariantKeyword, Token thisKeyword, FormalParameterType kind) {
     debugEvent("FormalParameter");
     _ParameterDefaultValue defaultValue = pop();
     SimpleIdentifier name = pop();
     TypeName type = pop();
     Token keyword = _popOptionalSingleModifier();
     pop(); // TODO(paulberry): Metadata.
-    // TODO(paulberry): handle covariant keyword.
 
     FormalParameter node;
     if (thisKeyword == null) {
-      node = ast.simpleFormalParameter(
-          null, null, toAnalyzerToken(keyword), type, name);
+      node = ast.simpleFormalParameter2(
+          covariantKeyword: toAnalyzerToken(covariantKeyword),
+          keyword: toAnalyzerToken(keyword),
+          type: type,
+          identifier: name);
     } else {
       // TODO(scheglov): Ideally the period token should be passed in.
       Token period = identical('.', thisKeyword.next?.stringValue)
           ? thisKeyword.next
           : null;
       TypeParameterList typeParameters; // TODO(scheglov)
       FormalParameterList formalParameters; // TODO(scheglov)
-      node = ast.fieldFormalParameter(
-          null,
-          null,
-          toAnalyzerToken(keyword),
-          type,
-          toAnalyzerToken(thisKeyword),
-          toAnalyzerToken(period),
-          name,
-          typeParameters,
-          formalParameters);
+      node = ast.fieldFormalParameter2(
+          covariantKeyword: toAnalyzerToken(covariantKeyword),
+          keyword: toAnalyzerToken(keyword),
+          type: type,
+          thisKeyword: toAnalyzerToken(thisKeyword),
+          period: toAnalyzerToken(period),
+          identifier: name,
+          typeParameters: typeParameters,
+          parameters: formalParameters);
     }
 
     if (defaultValue != null) {
       node = ast.defaultFormalParameter(node, _toAnalyzerParameterKind(kind),
           toAnalyzerToken(defaultValue.separator), defaultValue.value);
     }
 
     scope[name.name] = name.staticElement = new AnalyzerParameterElement(node);
     push(node);
   }
@@ skipping 716 matching lines @@
 }
 
 /// Data structure placed on the stack to represent the default parameter
 /// value with the separator token.
 class _ParameterDefaultValue {
   final Token separator;
   final Expression value;
 
   _ParameterDefaultValue(this.separator, this.value);
 }