improve parser recovery for incomplete prefixed identifier in method/function parameter 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 7136 matching lines @@
   void test_parseFormalParameterList_positional_single() {
     FormalParameterList parameterList =
         parse4("parseFormalParameterList", "([A a = null])");
     expect(parameterList.leftParenthesis, isNotNull);
     expect(parameterList.leftDelimiter, isNotNull);
     expect(parameterList.parameters, hasLength(1));
     expect(parameterList.rightDelimiter, isNotNull);
     expect(parameterList.rightParenthesis, isNotNull);
   }
 
+  void test_parseFormalParameterList_prefixedType() {
+    FormalParameterList parameterList =
+        parse4("parseFormalParameterList", "(io.File f)");
+    expect(parameterList.leftParenthesis, isNotNull);
+    expect(parameterList.leftDelimiter, isNull);
+    expect(parameterList.parameters, hasLength(1));
+    expect(parameterList.parameters[0].toSource(), 'io.File f');
+    expect(parameterList.rightDelimiter, isNull);
+    expect(parameterList.rightParenthesis, isNotNull);
+  }
+
+  void test_parseFormalParameterList_prefixedType_partial() {
+    FormalParameterList parameterList =
+        parse4("parseFormalParameterList", "(io.)", [
+          ParserErrorCode.MISSING_IDENTIFIER,
+          ParserErrorCode.MISSING_IDENTIFIER]);
+    expect(parameterList.leftParenthesis, isNotNull);
+    expect(parameterList.leftDelimiter, isNull);
+    expect(parameterList.parameters, hasLength(1));
+    expect(parameterList.parameters[0].toSource(), 'io. ');
+    expect(parameterList.rightDelimiter, isNull);
+    expect(parameterList.rightParenthesis, isNotNull);
+  }
+
+  void test_parseFormalParameterList_prefixedType_partial2() {
+    FormalParameterList parameterList =
+        parse4("parseFormalParameterList", "(io.,a)", [
+          ParserErrorCode.MISSING_IDENTIFIER,
+          ParserErrorCode.MISSING_IDENTIFIER]);
+    expect(parameterList.leftParenthesis, isNotNull);
+    expect(parameterList.leftDelimiter, isNull);
+    expect(parameterList.parameters, hasLength(2));
+    expect(parameterList.parameters[0].toSource(), 'io. ');
+    expect(parameterList.parameters[1].toSource(), 'a');
+    expect(parameterList.rightDelimiter, isNull);
+    expect(parameterList.rightParenthesis, isNotNull);
+  }
+
   void test_parseForStatement_each_await() {
     ForEachStatement statement =
         parse4("parseForStatement", "await for (element in list) {}");
     expect(statement.awaitKeyword, isNotNull);
     expect(statement.forKeyword, isNotNull);
     expect(statement.leftParenthesis, isNotNull);
     expect(statement.loopVariable, isNull);
     expect(statement.identifier, isNotNull);
     expect(statement.inKeyword, isNotNull);
     expect(statement.iterable, isNotNull);
@@ skipping 2734 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;
   }
 }