Always parse 'x.y' as a prefixed identifier.

pkg/analyzer/test/generated/parser_test.dart

 // Copyright (c) 2014, 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 analyzer.test.generated.parser_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/standard_ast_factory.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
@@ skipping 4162 matching lines @@
     expect(argumentList, isNotNull);
     expect(argumentList.arguments, hasLength(1));
     expect(propertyAccess.operator, isNotNull);
     expect(propertyAccess.propertyName, isNotNull);
   }
 
   void test_parseAssignableExpression_identifier_dot() {
     Expression expression = parseAssignableExpression('x.y', false);
     expect(expression, isNotNull);
     assertNoErrors();
-    var propertyAccess = expression as PropertyAccess;
-    expect(propertyAccess.target, isNotNull);
-    expect(propertyAccess.operator, isNotNull);
-    expect(propertyAccess.operator.type, TokenType.PERIOD);
-    expect(propertyAccess.propertyName, isNotNull);
+    var identifier = expression as PrefixedIdentifier;
+    expect(identifier.prefix.name, 'x');
+    expect(identifier.period, isNotNull);
+    expect(identifier.period.type, TokenType.PERIOD);
+    expect(identifier.identifier.name, 'y');
   }
 
   void test_parseAssignableExpression_identifier_index() {
     Expression expression = parseAssignableExpression('x[y]', false);
     expect(expression, isNotNull);
     assertNoErrors();
     var indexExpression = expression as IndexExpression;
     expect(indexExpression.target, isNotNull);
     expect(indexExpression.leftBracket, isNotNull);
     expect(indexExpression.index, isNotNull);
@@ skipping 10378 matching lines @@
     expect(typeAlias.name, isNotNull);
     expect(typeAlias.typeParameters, isNull);
     expect(typeAlias.semicolon, isNotNull);
     GenericFunctionType functionType = typeAlias.functionType;
     expect(functionType, isNotNull);
     expect(functionType.parameters, isNotNull);
     expect(functionType.returnType, isNotNull);
     expect(functionType.typeParameters, isNull);
   }
 }