Remove use of NullThrownError (#116122)

packages/flutter/lib/src/foundation/assertions.dart

@@ -672,9 +672,7 @@ class FlutterErrorDetails with Diagnosticable {
     super.debugFillProperties(properties);
     final DiagnosticsNode verb = ErrorDescription('thrown${ context != null ? ErrorDescription(" $context") : ""}');
     final Diagnosticable? diagnosticable = _exceptionToDiagnosticable();
-    if (exception is NullThrownError) { // ignore: deprecated_member_use
-      properties.add(ErrorDescription('The null value was $verb.'));
-    } else if (exception is num) {
+    if (exception is num) {
       properties.add(ErrorDescription('The number $exception was $verb.'));
     } else {
       final DiagnosticsNode errorName;

packages/flutter/test/foundation/_compute_caller_unsound_null_safety.dart

-// Copyright 2014 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Running in unsound null-safety mode is intended to test for potential miscasts
-// or invalid assertions.
-
-import 'package:flutter/src/foundation/_isolates_io.dart';
-import 'package:flutter/src/foundation/isolates.dart' as isolates;
-
-int? returnInt(int? arg) {
-  return arg;
-}
-
-Future<int?> returnIntAsync(int? arg) {
-  return Future<int>.value(arg);
-}
-
-Future<void> testCompute<T>(isolates.ComputeCallback<T, T> callback, T input) async {
-  if (input != await compute(callback, input)) {
-    throw Exception('compute returned bad result');
-  }
-}
-
-void main() async {
-  await testCompute(returnInt, 10);
-  await testCompute(returnInt, null);
-  await testCompute(returnIntAsync, 10);
-  await testCompute(returnIntAsync, null);
-}

packages/flutter/test/foundation/_compute_caller_unsound_null_safety_error.dart

-// Copyright 2014 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Running in unsound null-safety mode is intended to test for potential miscasts
-// or invalid assertions.
-
-import 'package:flutter/src/foundation/_isolates_io.dart';
-
-int throwNull(dynamic arg) {
-  throw arg as Object;
-}
-
-void main() async {
-  try {
-    await compute(throwNull, null);
-  } catch (e) {
-    if (e is! TypeError && e is! NullThrownError) { // ignore: deprecated_member_use
-      throw Exception('compute returned bad result');
-    }
-  }
-}

packages/flutter/test/foundation/assertions_test.dart

@@ -58,21 +58,6 @@ void main() {
         'INFO\n'
         '═════════════════════════════════════════════════════════════════\n',
     );
-    expect(
-      FlutterErrorDetails(
-        exception: NullThrownError(), // ignore: deprecated_member_use
-        library: 'LIBRARY',
-        context: ErrorDescription('CONTEXTING'),
-        informationCollector: () sync* {
-          yield ErrorDescription('INFO');
-        },
-      ).toString(),
-      '══╡ EXCEPTION CAUGHT BY LIBRARY ╞════════════════════════════════\n'
-      'The null value was thrown CONTEXTING.\n'
-      '\n'
-      'INFO\n'
-      '═════════════════════════════════════════════════════════════════\n',
-    );
     expect(
       FlutterErrorDetails(
         exception: 'MESSAGE',
@@ -112,13 +97,6 @@ void main() {
       'MESSAGE\n'
       '═════════════════════════════════════════════════════════════════\n',
     );
-    expect(
-      // ignore: deprecated_member_use
-      FlutterErrorDetails(exception: NullThrownError()).toString(),
-      '══╡ EXCEPTION CAUGHT BY FLUTTER FRAMEWORK ╞══════════════════════\n'
-      'The null value was thrown.\n'
-      '═════════════════════════════════════════════════════════════════\n',
-    );
   });
 
   test('FlutterErrorDetails.toStringShort', () {

packages/flutter/test/foundation/isolates_test.dart

@@ -221,15 +221,4 @@ void main() {
           '_compute_caller_invalid_message.dart');
     });
   }, skip: kIsWeb); // [intended] isn't supported on the web.
-
-  group('compute() works with unsound null safety caller', () {
-    test('returning', () async {
-      await expectFileSuccessfullyCompletes(
-          '_compute_caller_unsound_null_safety.dart', true);
-    });
-    test('erroring', () async {
-      await expectFileSuccessfullyCompletes(
-          '_compute_caller_unsound_null_safety_error.dart', true);
-    });
-  }, skip: kIsWeb); // [intended] isn't supported on the web.
 }