improve parser recovery of type argument list

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 engine.parser_test;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/incremental_scanner.dart';
@@ skipping 8748 matching lines @@
     expect(identifier.name, lexeme);
   }
 
   void test_parseSimpleIdentifier_normalIdentifier() {
     String lexeme = "foo";
     SimpleIdentifier identifier = parse4("parseSimpleIdentifier", lexeme);
     expect(identifier.token, isNotNull);
     expect(identifier.name, lexeme);
   }
 
+  void test_parseStatement_emptyTypeArgumentListt() {
+    VariableDeclarationStatement statement = ParserTestCase.parse4(
+        "parseStatement", "C<> c;", [ParserErrorCode.EXPECTED_TYPE_NAME]);
+    VariableDeclarationList variables = statement.variables;
+    TypeName type = variables.type;
+    TypeArgumentList argumentList = type.typeArguments;
+    expect(argumentList.leftBracket, isNotNull);
+    expect(argumentList.arguments, hasLength(1));
+    expect(argumentList.arguments[0].isSynthetic, isTrue);
+    expect(argumentList.rightBracket, isNotNull);
+  }
+
   void test_parseStatement_functionDeclaration() {
     // TODO(brianwilkerson) Implement more tests for this method.
     FunctionDeclarationStatement statement =
         parse4("parseStatement", "int f(a, b) {};");
     expect(statement.functionDeclaration, isNotNull);
   }
 
   void test_parseStatement_mulipleLabels() {
     LabeledStatement statement = parse4("parseStatement", "l: m: return x;");
     expect(statement.labels, hasLength(2));
@@ skipping 345 matching lines @@
     FunctionTypeAlias typeAlias = parse("parseTypeAlias",
         <Object>[emptyCommentAndMetadata()], "typedef void F();");
     expect(typeAlias.typedefKeyword, isNotNull);
     expect(typeAlias.name, isNotNull);
     expect(typeAlias.parameters, isNotNull);
     expect(typeAlias.returnType, isNotNull);
     expect(typeAlias.semicolon, isNotNull);
     expect(typeAlias.typeParameters, isNull);
   }
 
+  void test_parseTypeArgumentList_empty() {
+    TypeArgumentList argumentList = ParserTestCase.parse4(
+        "parseTypeArgumentList", "<>", [ParserErrorCode.EXPECTED_TYPE_NAME]);
+    expect(argumentList.leftBracket, isNotNull);
+    expect(argumentList.arguments, hasLength(1));
+    expect(argumentList.rightBracket, isNotNull);
+  }
+
   void test_parseTypeArgumentList_multiple() {
     TypeArgumentList argumentList =
         parse4("parseTypeArgumentList", "<int, int, int>");
     expect(argumentList.leftBracket, isNotNull);
     expect(argumentList.arguments, hasLength(3));
     expect(argumentList.rightBracket, isNotNull);
   }
 
   void test_parseTypeArgumentList_nested() {
     TypeArgumentList argumentList = parse4("parseTypeArgumentList", "<A<B>>");
@@ skipping 661 matching lines @@
         new Scanner(null, new CharSequenceReader(source), listener);
     Token tokenStream = scanner.tokenize();
     //
     // Parse the source.
     //
     Parser parser = new Parser(null, listener);
     return invokeParserMethodImpl(
         parser, methodName, <Object>[tokenStream], tokenStream) as Token;
   }
 }