[DAS] Fixes getDefaultStringParameterValue for parameters with no name

Fixes: #60579
Change-Id: I5bc2ef990fab1ef8a76efb6fdcb53dbc8ba9c10d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/423761
Commit-Queue: Brian Wilkerson <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>
Auto-Submit: Felipe Morschel <[email protected]>

Author: FMorschel

pkg/analysis_server/lib/src/services/completion/dart/utilities.dart

@@ -15,6 +15,7 @@ import 'package:analyzer/dart/element/nullability_suffix.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/source/source.dart';
 import 'package:analyzer/src/utilities/extensions/flutter.dart';
+import 'package:analyzer/src/utilities/extensions/string.dart';
 import 'package:analyzer_plugin/protocol/protocol_common.dart'
     as protocol
     show Element, ElementKind;
@@ -179,8 +180,12 @@ DefaultArgument? getDefaultStringParameterValue(
       return DefaultArgument('$quote$quote', cursorPosition: 1);
     }
   } else if (type is FunctionType) {
-    var params = type.formalParameters
-        .map((p) => '${getTypeString(p.type)}${p.displayName}')
+    var params = type.formalParameters.indexed
+        .map((r) {
+          var (index, parameter) = r;
+          var name = parameter.displayName.ifNotEmptyOrElse('p${index + 1}');
+          return '${getTypeString(parameter.type)}$name';
+        })
         .join(', ');
     // TODO(devoncarew): Support having this method return text with newlines.
     var text = '($params) {  }';

pkg/analysis_server/test/src/services/correction/fix/add_missing_required_argument_test.dart

@@ -319,6 +319,23 @@ void f() {
 ''');
   }
 
+  Future<void> test_functionType_noParameterName() async {
+    await resolveTestCode('''
+void foo({required void Function(int) f}) {}
+
+void bar() {
+  foo();
+}
+''');
+    await assertHasFix('''
+void foo({required void Function(int) f}) {}
+
+void bar() {
+  foo(f: (int p1) {  });
+}
+''');
+  }
+
   Future<void> test_multiple() async {
     await resolveTestCode('''
 test({required int a, required int bcd}) {}