improve parser recovery for incomplete prefixed identifier in method/function parameter list

pkg/analyzer/test/generated/parser_test.dart

Index: pkg/analyzer/test/generated/parser_test.dart
diff --git a/pkg/analyzer/test/generated/parser_test.dart b/pkg/analyzer/test/generated/parser_test.dart
index 12ba5b4d310f93ea8cbb69826beb40f143892274..b21fbee49142904bb5f2aa76a4563276d6326050 100644
--- a/pkg/analyzer/test/generated/parser_test.dart
+++ b/pkg/analyzer/test/generated/parser_test.dart
@@ -7154,6 +7154,44 @@ void''');
     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) {}");