[DAS] Adds tests for create extension member fixes for Object? target

I'd already added the required fixes to the specific diagnostics at 2175df0 so this only adds tests for them.

Bug: #61192
Change-Id: Ia49cd4ddb68ad04fc0eab0a02614959fa2296759
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/447280
Auto-Submit: Felipe Morschel <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>

Author: FMorschel

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

@@ -250,6 +250,23 @@ extension E on int {
 ''');
   }
 
+  Future<void> test_nullableObject_target() async {
+    await resolveTestCode('''
+void f(Object? o) {
+  int _ = o.test;
+}
+''');
+    await assertHasFix('''
+void f(Object? o) {
+  int _ = o.test;
+}
+
+extension on Object? {
+  int get test => null;
+}
+''');
+  }
+
   Future<void> test_nullableTargetType() async {
     await resolveTestCode('''
 void f(int? p) {
@@ -827,6 +844,23 @@ extension E on int {
 ''');
   }
 
+  Future<void> test_nullableObject_target() async {
+    await resolveTestCode('''
+void f(Object? o) {
+  int _ = o.test();
+}
+''');
+    await assertHasFix('''
+void f(Object? o) {
+  int _ = o.test();
+}
+
+extension on Object? {
+  int test() {}
+}
+''');
+  }
+
   Future<void> test_nullableTargetType() async {
     await resolveTestCode('''
 void f(int? p) {
@@ -1533,6 +1567,23 @@ extension on int {
 ''');
   }
 
+  Future<void> test_nullableObject_target() async {
+    await resolveTestCode('''
+void f(Object? o) {
+  o + 0;
+}
+''');
+    await assertHasFix('''
+void f(Object? o) {
+  o + 0;
+}
+
+extension on Object? {
+  void operator +(int other) {}
+}
+''');
+  }
+
   Future<void> test_nullableTargetType() async {
     await resolveTestCode('''
 void f(int? p) {
@@ -1746,6 +1797,23 @@ extension on int {}
 ''');
   }
 
+  Future<void> test_nullableObject_target() async {
+    await resolveTestCode('''
+void f(Object? o) {
+  o.test = 0;
+}
+''');
+    await assertHasFix('''
+void f(Object? o) {
+  o.test = 0;
+}
+
+extension on Object? {
+  set test(int test) {}
+}
+''');
+  }
+
   Future<void> test_nullableTargetType() async {
     await resolveTestCode('''
 void f(int? p) {