Issue 52296. Fix NPE in AddTypeAnnotation, when formal parameter without name.

Bug: https://github.com/dart-lang/sdk/issues/52296
Change-Id: I6f3952faa9f3fc9e7f9e1d83c4699222be8dbcdc
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/301731
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Keerti Parthasarathy <keertip@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/analysis_server/lib/src/services/correction/dart/add_type_annotation.dart

@@ -47,10 +47,12 @@ class AddTypeAnnotation extends CorrectionProducer {
   @override
   Future<void> compute(ChangeBuilder builder) async {
     final node = this.node;
+
     if (node is SimpleFormalParameter) {
-      await _forSimpleFormalParameter(builder, node.name!, node);
+      await _forSimpleFormalParameter(builder, node);
       return;
     }
+
     if (node is DeclaredVariablePattern) {
       var type = node.matchedValueType;
       var keyword = node.keyword;
@@ -133,12 +135,17 @@ class AddTypeAnnotation extends CorrectionProducer {
         builder, declaredIdentifier.keyword, declaredIdentifier.name, type);
   }
 
-  Future<void> _forSimpleFormalParameter(ChangeBuilder builder, Token name,
-      SimpleFormalParameter parameter) async {
+  Future<void> _forSimpleFormalParameter(
+      ChangeBuilder builder, SimpleFormalParameter parameter) async {
     // Ensure that there isn't already a type annotation.
     if (parameter.type != null) {
       return;
     }
+    // Ensure that the parameter is named.
+    final name = parameter.name;
+    if (name == null) {
+      return;
+    }
     // Prepare the type.
     var type = parameter.declaredElement!.type;
     // TODO(scheglov) If the parameter is in a method declaration, and if the

pkg/analysis_server/test/src/services/correction/assist/add_type_annotation_test.dart

@@ -689,6 +689,14 @@ void f() {
 ''');
   }
 
+  Future<void> test_parameter_final_type_noName() async {
+    verifyNoTestUnitErrors = false;
+    await resolveTestCode('''
+typedef F = void Function(final int);
+''');
+    await assertNoAssistAt('final');
+  }
+
   @FailingTest(reason: '''
 This functionality is disabled in `AddTypeAnnotation._forSimpleFormalParameter`
 because `writeType` is writing the names of the parameters when it shouldn't.